1 <html><head><title>N1570 April 12, 2011 ISO/IEC 9899:201x</title></head><body>
3 N1570 Committee Draft -- April 12, 2011 ISO/IEC 9899:201x
8 INTERNATIONAL STANDARD (C)ISO/IEC ISO/IEC 9899:201x
15 <p><small><a href="#Contents">Contents</a></small>
16 <h1>Programming languages -- C</h1>
24 (Cover sheet to be provided by ISO Secretariat.)
26 This International Standard specifies the form and establishes the interpretation of
27 programs expressed in the programming language C. Its purpose is to promote
28 portability, reliability, maintainability, and efficient execution of C language programs on
29 a variety of computing systems.
31 Clauses are included that detail the C language itself and the contents of the C language
32 execution library. Annexes summarize aspects of both of them, and enumerate factors
33 that influence the portability of C programs.
35 Although this International Standard is intended to guide knowledgeable C language
36 programmers as well as implementors of C language translation systems, the document
37 itself is not designed to serve as a tutorial.
39 Recipients of this draft are invited to submit, with their comments, notification of any
40 relevant patent rights of which they are aware and to provide supporting documentation.
42 Changes from the previous draft (N1539) are indicated by ''diff marks'' in the right
43 margin: deleted text is marked with ''*'', new or changed text with '' ''.
48 <p><small><a href="#Contents">Contents</a></small>
49 <h2><a name="Contents" href="#Contents">Contents</a></h2>
51 <li><a href="#Foreword">Foreword</a>
52 <li><a href="#Introduction">Introduction</a>
53 <li><a href="#1">1. Scope</a>
54 <li><a href="#2">2. Normative references</a>
55 <li><a href="#3">3. Terms, definitions, and symbols</a>
56 <li><a href="#4">4. Conformance</a>
57 <li><a href="#5">5. Environment</a>
59 <li><a href="#5.1"> 5.1 Conceptual models</a>
61 <li><a href="#5.1.1"> 5.1.1 Translation environment</a>
62 <li><a href="#5.1.2"> 5.1.2 Execution environments</a>
64 <li><a href="#5.2"> 5.2 Environmental considerations</a>
66 <li><a href="#5.2.1"> 5.2.1 Character sets</a>
67 <li><a href="#5.2.2"> 5.2.2 Character display semantics</a>
68 <li><a href="#5.2.3"> 5.2.3 Signals and interrupts</a>
69 <li><a href="#5.2.4"> 5.2.4 Environmental limits</a>
72 <li><a href="#6">6. Language</a>
74 <li><a href="#6.1"> 6.1 Notation</a>
75 <li><a href="#6.2"> 6.2 Concepts</a>
77 <li><a href="#6.2.1"> 6.2.1 Scopes of identifiers</a>
78 <li><a href="#6.2.2"> 6.2.2 Linkages of identifiers</a>
79 <li><a href="#6.2.3"> 6.2.3 Name spaces of identifiers</a>
80 <li><a href="#6.2.4"> 6.2.4 Storage durations of objects</a>
81 <li><a href="#6.2.5"> 6.2.5 Types</a>
82 <li><a href="#6.2.6"> 6.2.6 Representations of types</a>
83 <li><a href="#6.2.7"> 6.2.7 Compatible type and composite type</a>
84 <li><a href="#6.2.8"> 6.2.8 Alignment of objects</a>
86 <li><a href="#6.3"> 6.3 Conversions</a>
88 <li><a href="#6.3.1"> 6.3.1 Arithmetic operands</a>
89 <li><a href="#6.3.2"> 6.3.2 Other operands</a>
91 <li><a href="#6.4"> 6.4 Lexical elements</a>
93 <li><a href="#6.4.1"> 6.4.1 Keywords</a>
94 <li><a href="#6.4.2"> 6.4.2 Identifiers</a>
95 <li><a href="#6.4.3"> 6.4.3 Universal character names</a>
96 <li><a href="#6.4.4"> 6.4.4 Constants</a>
97 <li><a href="#6.4.5"> 6.4.5 String literals</a>
98 <li><a href="#6.4.6"> 6.4.6 Punctuators</a>
99 <li><a href="#6.4.7"> 6.4.7 Header names</a>
100 <li><a href="#6.4.8"> 6.4.8 Preprocessing numbers</a>
101 <li><a href="#6.4.9"> 6.4.9 Comments</a>
104 <li><a href="#6.5"> 6.5 Expressions</a>
106 <li><a href="#6.5.1"> 6.5.1 Primary expressions</a>
107 <li><a href="#6.5.2"> 6.5.2 Postfix operators</a>
108 <li><a href="#6.5.3"> 6.5.3 Unary operators</a>
109 <li><a href="#6.5.4"> 6.5.4 Cast operators</a>
110 <li><a href="#6.5.5"> 6.5.5 Multiplicative operators</a>
111 <li><a href="#6.5.6"> 6.5.6 Additive operators</a>
112 <li><a href="#6.5.7"> 6.5.7 Bitwise shift operators</a>
113 <li><a href="#6.5.8"> 6.5.8 Relational operators</a>
114 <li><a href="#6.5.9"> 6.5.9 Equality operators</a>
115 <li><a href="#6.5.10"> 6.5.10 Bitwise AND operator</a>
116 <li><a href="#6.5.11"> 6.5.11 Bitwise exclusive OR operator</a>
117 <li><a href="#6.5.12"> 6.5.12 Bitwise inclusive OR operator</a>
118 <li><a href="#6.5.13"> 6.5.13 Logical AND operator</a>
119 <li><a href="#6.5.14"> 6.5.14 Logical OR operator</a>
120 <li><a href="#6.5.15"> 6.5.15 Conditional operator</a>
121 <li><a href="#6.5.16"> 6.5.16 Assignment operators</a>
122 <li><a href="#6.5.17"> 6.5.17 Comma operator</a>
124 <li><a href="#6.6"> 6.6 Constant expressions</a>
125 <li><a href="#6.7"> 6.7 Declarations</a>
127 <li><a href="#6.7.1"> 6.7.1 Storage-class specifiers</a>
128 <li><a href="#6.7.2"> 6.7.2 Type specifiers</a>
129 <li><a href="#6.7.3"> 6.7.3 Type qualifiers</a>
130 <li><a href="#6.7.4"> 6.7.4 Function specifiers</a>
131 <li><a href="#6.7.5"> 6.7.5 Alignment specifier</a>
132 <li><a href="#6.7.6"> 6.7.6 Declarators</a>
133 <li><a href="#6.7.7"> 6.7.7 Type names</a>
134 <li><a href="#6.7.8"> 6.7.8 Type definitions</a>
135 <li><a href="#6.7.9"> 6.7.9 Initialization</a>
136 <li><a href="#6.7.10"> 6.7.10 Static assertions</a>
138 <li><a href="#6.8"> 6.8 Statements and blocks</a>
140 <li><a href="#6.8.1"> 6.8.1 Labeled statements</a>
141 <li><a href="#6.8.2"> 6.8.2 Compound statement</a>
142 <li><a href="#6.8.3"> 6.8.3 Expression and null statements</a>
143 <li><a href="#6.8.4"> 6.8.4 Selection statements</a>
144 <li><a href="#6.8.5"> 6.8.5 Iteration statements</a>
145 <li><a href="#6.8.6"> 6.8.6 Jump statements</a>
147 <li><a href="#6.9"> 6.9 External definitions</a>
149 <li><a href="#6.9.1"> 6.9.1 Function definitions</a>
150 <li><a href="#6.9.2"> 6.9.2 External object definitions</a>
152 <li><a href="#6.10"> 6.10 Preprocessing directives</a>
154 <li><a href="#6.10.1"> 6.10.1 Conditional inclusion</a>
155 <li><a href="#6.10.2"> 6.10.2 Source file inclusion</a>
156 <li><a href="#6.10.3"> 6.10.3 Macro replacement</a>
158 <li><a href="#6.10.4"> 6.10.4 Line control</a>
159 <li><a href="#6.10.5"> 6.10.5 Error directive</a>
160 <li><a href="#6.10.6"> 6.10.6 Pragma directive</a>
161 <li><a href="#6.10.7"> 6.10.7 Null directive</a>
162 <li><a href="#6.10.8"> 6.10.8 Predefined macro names</a>
163 <li><a href="#6.10.9"> 6.10.9 Pragma operator</a>
165 <li><a href="#6.11"> 6.11 Future language directions</a>
167 <li><a href="#6.11.1"> 6.11.1 Floating types</a>
168 <li><a href="#6.11.2"> 6.11.2 Linkages of identifiers</a>
169 <li><a href="#6.11.3"> 6.11.3 External names</a>
170 <li><a href="#6.11.4"> 6.11.4 Character escape sequences</a>
171 <li><a href="#6.11.5"> 6.11.5 Storage-class specifiers</a>
172 <li><a href="#6.11.6"> 6.11.6 Function declarators</a>
173 <li><a href="#6.11.7"> 6.11.7 Function definitions</a>
174 <li><a href="#6.11.8"> 6.11.8 Pragma directives</a>
175 <li><a href="#6.11.9"> 6.11.9 Predefined macro names</a>
178 <li><a href="#7">7. Library</a>
180 <li><a href="#7.1"> 7.1 Introduction</a>
182 <li><a href="#7.1.1"> 7.1.1 Definitions of terms</a>
183 <li><a href="#7.1.2"> 7.1.2 Standard headers</a>
184 <li><a href="#7.1.3"> 7.1.3 Reserved identifiers</a>
185 <li><a href="#7.1.4"> 7.1.4 Use of library functions</a>
187 <li><a href="#7.2"> 7.2 Diagnostics <assert.h></a>
189 <li><a href="#7.2.1"> 7.2.1 Program diagnostics</a>
191 <li><a href="#7.3"> 7.3 Complex arithmetic <complex.h></a>
193 <li><a href="#7.3.1"> 7.3.1 Introduction</a>
194 <li><a href="#7.3.2"> 7.3.2 Conventions</a>
195 <li><a href="#7.3.3"> 7.3.3 Branch cuts</a>
196 <li><a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma</a>
197 <li><a href="#7.3.5"> 7.3.5 Trigonometric functions</a>
198 <li><a href="#7.3.6"> 7.3.6 Hyperbolic functions</a>
199 <li><a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions</a>
200 <li><a href="#7.3.8"> 7.3.8 Power and absolute-value functions</a>
201 <li><a href="#7.3.9"> 7.3.9 Manipulation functions</a>
203 <li><a href="#7.4"> 7.4 Character handling <ctype.h></a>
205 <li><a href="#7.4.1"> 7.4.1 Character classification functions</a>
206 <li><a href="#7.4.2"> 7.4.2 Character case mapping functions</a>
208 <li><a href="#7.5"> 7.5 Errors <errno.h></a>
209 <li><a href="#7.6"> 7.6 Floating-point environment <fenv.h></a>
211 <li><a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma</a>
212 <li><a href="#7.6.2"> 7.6.2 Floating-point exceptions</a>
213 <li><a href="#7.6.3"> 7.6.3 Rounding</a>
214 <li><a href="#7.6.4"> 7.6.4 Environment</a>
216 <li><a href="#7.7"> 7.7 Characteristics of floating types <float.h></a>
218 <li><a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h></a>
220 <li><a href="#7.8.1"> 7.8.1 Macros for format specifiers</a>
221 <li><a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types</a>
223 <li><a href="#7.9"> 7.9 Alternative spellings <iso646.h></a>
224 <li><a href="#7.10"> 7.10 Sizes of integer types <limits.h></a>
225 <li><a href="#7.11"> 7.11 Localization <locale.h></a>
227 <li><a href="#7.11.1"> 7.11.1 Locale control</a>
228 <li><a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry</a>
230 <li><a href="#7.12"> 7.12 Mathematics <math.h></a>
232 <li><a href="#7.12.1"> 7.12.1 Treatment of error conditions</a>
233 <li><a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma</a>
234 <li><a href="#7.12.3"> 7.12.3 Classification macros</a>
235 <li><a href="#7.12.4"> 7.12.4 Trigonometric functions</a>
236 <li><a href="#7.12.5"> 7.12.5 Hyperbolic functions</a>
237 <li><a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions</a>
238 <li><a href="#7.12.7"> 7.12.7 Power and absolute-value functions</a>
239 <li><a href="#7.12.8"> 7.12.8 Error and gamma functions</a>
240 <li><a href="#7.12.9"> 7.12.9 Nearest integer functions</a>
241 <li><a href="#7.12.10"> 7.12.10 Remainder functions</a>
242 <li><a href="#7.12.11"> 7.12.11 Manipulation functions</a>
243 <li><a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions</a>
244 <li><a href="#7.12.13"> 7.12.13 Floating multiply-add</a>
245 <li><a href="#7.12.14"> 7.12.14 Comparison macros</a>
247 <li><a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h></a>
249 <li><a href="#7.13.1"> 7.13.1 Save calling environment</a>
250 <li><a href="#7.13.2"> 7.13.2 Restore calling environment</a>
252 <li><a href="#7.14"> 7.14 Signal handling <signal.h></a>
254 <li><a href="#7.14.1"> 7.14.1 Specify signal handling</a>
255 <li><a href="#7.14.2"> 7.14.2 Send signal</a>
257 <li><a href="#7.15"> 7.15 Alignment <stdalign.h></a>
258 <li><a href="#7.16"> 7.16 Variable arguments <stdarg.h></a>
260 <li><a href="#7.16.1"> 7.16.1 Variable argument list access macros</a>
262 <li><a href="#7.17"> 7.17 Atomics <stdatomic.h></a>
264 <li><a href="#7.17.1"> 7.17.1 Introduction</a>
265 <li><a href="#7.17.2"> 7.17.2 Initialization</a>
266 <li><a href="#7.17.3"> 7.17.3 Order and consistency</a>
267 <li><a href="#7.17.4"> 7.17.4 Fences</a>
268 <li><a href="#7.17.5"> 7.17.5 Lock-free property</a>
269 <li><a href="#7.17.6"> 7.17.6 Atomic integer types</a>
270 <li><a href="#7.17.7"> 7.17.7 Operations on atomic types</a>
271 <li><a href="#7.17.8"> 7.17.8 Atomic flag type and operations</a>
273 <li><a href="#7.18"> 7.18 Boolean type and values <stdbool.h></a>
274 <li><a href="#7.19"> 7.19 Common definitions <stddef.h></a>
275 <li><a href="#7.20"> 7.20 Integer types <stdint.h></a>
278 <li><a href="#7.20.1"> 7.20.1 Integer types</a>
279 <li><a href="#7.20.2"> 7.20.2 Limits of specified-width integer types</a>
280 <li><a href="#7.20.3"> 7.20.3 Limits of other integer types</a>
281 <li><a href="#7.20.4"> 7.20.4 Macros for integer constants</a>
283 <li><a href="#7.21"> 7.21 Input/output <stdio.h></a>
285 <li><a href="#7.21.1"> 7.21.1 Introduction</a>
286 <li><a href="#7.21.2"> 7.21.2 Streams</a>
287 <li><a href="#7.21.3"> 7.21.3 Files</a>
288 <li><a href="#7.21.4"> 7.21.4 Operations on files</a>
289 <li><a href="#7.21.5"> 7.21.5 File access functions</a>
290 <li><a href="#7.21.6"> 7.21.6 Formatted input/output functions</a>
291 <li><a href="#7.21.7"> 7.21.7 Character input/output functions</a>
292 <li><a href="#7.21.8"> 7.21.8 Direct input/output functions</a>
293 <li><a href="#7.21.9"> 7.21.9 File positioning functions</a>
294 <li><a href="#7.21.10"> 7.21.10 Error-handling functions</a>
296 <li><a href="#7.22"> 7.22 General utilities <stdlib.h></a>
298 <li><a href="#7.22.1"> 7.22.1 Numeric conversion functions</a>
299 <li><a href="#7.22.2"> 7.22.2 Pseudo-random sequence generation functions</a>
300 <li><a href="#7.22.3"> 7.22.3 Memory management functions</a>
301 <li><a href="#7.22.4"> 7.22.4 Communication with the environment</a>
302 <li><a href="#7.22.5"> 7.22.5 Searching and sorting utilities</a>
303 <li><a href="#7.22.6"> 7.22.6 Integer arithmetic functions</a>
304 <li><a href="#7.22.7"> 7.22.7 Multibyte/wide character conversion functions</a>
305 <li><a href="#7.22.8"> 7.22.8 Multibyte/wide string conversion functions</a>
307 <li><a href="#7.23"> 7.23 _Noreturn <stdnoreturn.h></a>
308 <li><a href="#7.24"> 7.24 String handling <string.h></a>
310 <li><a href="#7.24.1"> 7.24.1 String function conventions</a>
311 <li><a href="#7.24.2"> 7.24.2 Copying functions</a>
312 <li><a href="#7.24.3"> 7.24.3 Concatenation functions</a>
313 <li><a href="#7.24.4"> 7.24.4 Comparison functions</a>
314 <li><a href="#7.24.5"> 7.24.5 Search functions</a>
315 <li><a href="#7.24.6"> 7.24.6 Miscellaneous functions</a>
317 <li><a href="#7.25"> 7.25 Type-generic math <tgmath.h></a>
318 <li><a href="#7.26"> 7.26 Threads <threads.h></a>
320 <li><a href="#7.26.1"> 7.26.1 Introduction</a>
321 <li><a href="#7.26.2"> 7.26.2 Initialization functions</a>
322 <li><a href="#7.26.3"> 7.26.3 Condition variable functions</a>
323 <li><a href="#7.26.4"> 7.26.4 Mutex functions</a>
324 <li><a href="#7.26.5"> 7.26.5 Thread functions</a>
325 <li><a href="#7.26.6"> 7.26.6 Thread-specific storage functions</a>
327 <li><a href="#7.27"> 7.27 Date and time <time.h></a>
329 <li><a href="#7.27.1"> 7.27.1 Components of time</a>
330 <li><a href="#7.27.2"> 7.27.2 Time manipulation functions</a>
331 <li><a href="#7.27.3"> 7.27.3 Time conversion functions</a>
334 <li><a href="#7.28"> 7.28 Unicode utilities <uchar.h></a>
336 <li><a href="#7.28.1"> 7.28.1 Restartable multibyte/wide character conversion functions</a>
338 <li><a href="#7.29"> 7.29 Extended multibyte and wide character utilities <wchar.h></a>
340 <li><a href="#7.29.1"> 7.29.1 Introduction</a>
341 <li><a href="#7.29.2"> 7.29.2 Formatted wide character input/output functions</a>
342 <li><a href="#7.29.3"> 7.29.3 Wide character input/output functions</a>
343 <li><a href="#7.29.4"> 7.29.4 General wide string utilities</a>
345 <li><a href="#7.29.4.1"> 7.29.4.1 Wide string numeric conversion functions</a>
346 <li><a href="#7.29.4.2"> 7.29.4.2 Wide string copying functions</a>
347 <li><a href="#7.29.4.3"> 7.29.4.3 Wide string concatenation functions</a>
348 <li><a href="#7.29.4.4"> 7.29.4.4 Wide string comparison functions</a>
349 <li><a href="#7.29.4.5"> 7.29.4.5 Wide string search functions</a>
350 <li><a href="#7.29.4.6"> 7.29.4.6 Miscellaneous functions</a>
352 <li><a href="#7.29.5"> 7.29.5 Wide character time conversion functions</a>
353 <li><a href="#7.29.6"> 7.29.6 Extended multibyte/wide character conversion utilities</a>
355 <li><a href="#7.29.6.1"> 7.29.6.1 Single-byte/wide character conversion functions</a>
356 <li><a href="#7.29.6.2"> 7.29.6.2 Conversion state functions</a>
357 <li><a href="#7.29.6.3"> 7.29.6.3 Restartable multibyte/wide character conversion functions</a>
358 <li><a href="#7.29.6.4"> 7.29.6.4 Restartable multibyte/wide string conversion functions</a>
361 <li><a href="#7.30"> 7.30 Wide character classification and mapping utilities <wctype.h></a>
363 <li><a href="#7.30.1"> 7.30.1 Introduction</a>
364 <li><a href="#7.30.2"> 7.30.2 Wide character classification utilities</a>
366 <li><a href="#7.30.2.1"> 7.30.2.1 Wide character classification functions</a>
367 <li><a href="#7.30.2.2"> 7.30.2.2 Extensible wide character classification functions</a>
369 <li><a href="#7.30.3"> 7.30.3 Wide character case mapping utilities</a>
371 <li><a href="#7.30.3.1"> 7.30.3.1 Wide character case mapping functions</a>
372 <li><a href="#7.30.3.2"> 7.30.3.2 Extensible wide character case mapping functions</a>
375 <li><a href="#7.31"> 7.31 Future library directions</a>
377 <li><a href="#7.31.1"> 7.31.1 Complex arithmetic <complex.h></a>
378 <li><a href="#7.31.2"> 7.31.2 Character handling <ctype.h></a>
379 <li><a href="#7.31.3"> 7.31.3 Errors <errno.h></a>
380 <li><a href="#7.31.4"> 7.31.4 Floating-point environment <fenv.h></a>
381 <li><a href="#7.31.5"> 7.31.5 Format conversion of integer types <inttypes.h></a>
382 <li><a href="#7.31.6"> 7.31.6 Localization <locale.h></a>
383 <li><a href="#7.31.7"> 7.31.7 Signal handling <signal.h></a>
384 <li><a href="#7.31.8"> 7.31.8 Atomics <stdatomic.h></a>
385 <li><a href="#7.31.9"> 7.31.9 Boolean type and values <stdbool.h></a>
386 <li><a href="#7.31.10"> 7.31.10 Integer types <stdint.h></a>
387 <li><a href="#7.31.11"> 7.31.11 Input/output <stdio.h></a>
388 <li><a href="#7.31.12"> 7.31.12 General utilities <stdlib.h></a>
390 <li><a href="#7.31.13"> 7.31.13 String handling <string.h></a>
391 <li><a href="#7.31.14"> 7.31.14 Date and time <time.h></a>
392 <li><a href="#7.31.15"> 7.31.15 Threads <threads.h></a>
393 <li><a href="#7.31.16"> 7.31.16 Extended multibyte and wide character utilities <wchar.h></a>
394 <li><a href="#7.31.17"> 7.31.17 Wide character classification and mapping utilities <wctype.h></a>
397 <li><a href="#A">Annex A (informative) Language syntax summary</a>
399 <li><a href="#A.1"> A.1 Lexical grammar</a>
400 <li><a href="#A.2"> A.2 Phrase structure grammar</a>
401 <li><a href="#A.3"> A.3 Preprocessing directives</a>
403 <li><a href="#B">Annex B (informative) Library summary</a>
405 <li><a href="#B.1"> B.1 Diagnostics <assert.h></a>
406 <li><a href="#B.2"> B.2 Complex <complex.h></a>
407 <li><a href="#B.3"> B.3 Character handling <ctype.h></a>
408 <li><a href="#B.4"> B.4 Errors <errno.h></a>
409 <li><a href="#B.5"> B.5 Floating-point environment <fenv.h></a>
410 <li><a href="#B.6"> B.6 Characteristics of floating types <float.h></a>
411 <li><a href="#B.7"> B.7 Format conversion of integer types <inttypes.h></a>
412 <li><a href="#B.8"> B.8 Alternative spellings <iso646.h></a>
413 <li><a href="#B.9"> B.9 Sizes of integer types <limits.h></a>
414 <li><a href="#B.10"> B.10 Localization <locale.h></a>
415 <li><a href="#B.11"> B.11 Mathematics <math.h></a>
416 <li><a href="#B.12"> B.12 Nonlocal jumps <setjmp.h></a>
417 <li><a href="#B.13"> B.13 Signal handling <signal.h></a>
418 <li><a href="#B.14"> B.14 Alignment <stdalign.h></a>
419 <li><a href="#B.15"> B.15 Variable arguments <stdarg.h></a>
420 <li><a href="#B.16"> B.16 Atomics <stdatomic.h></a>
421 <li><a href="#B.17"> B.17 Boolean type and values <stdbool.h></a>
422 <li><a href="#B.18"> B.18 Common definitions <stddef.h></a>
423 <li><a href="#B.19"> B.19 Integer types <stdint.h></a>
424 <li><a href="#B.20"> B.20 Input/output <stdio.h></a>
425 <li><a href="#B.21"> B.21 General utilities <stdlib.h></a>
426 <li><a href="#B.22"> B.22 _Noreturn <stdnoreturn.h></a>
427 <li><a href="#B.23"> B.23 String handling <string.h></a>
428 <li><a href="#B.24"> B.24 Type-generic math <tgmath.h></a>
429 <li><a href="#B.25"> B.25 Threads <threads.h></a>
430 <li><a href="#B.26"> B.26 Date and time <time.h></a>
431 <li><a href="#B.27"> B.27 Unicode utilities <uchar.h></a>
432 <li><a href="#B.28"> B.28 Extended multibyte/wide character utilities <wchar.h></a>
433 <li><a href="#B.29"> B.29 Wide character classification and mapping utilities <wctype.h></a>
435 <li><a href="#C">Annex C (informative) Sequence points</a>
437 <li><a href="#D">Annex D (normative) Universal character names for identifiers</a>
439 <li><a href="#D.1"> D.1 Ranges of characters allowed</a>
440 <li><a href="#D.2"> D.2 Ranges of characters disallowed initially</a>
442 <li><a href="#E">Annex E (informative) Implementation limits</a>
443 <li><a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic</a>
445 <li><a href="#F.1"> F.1 Introduction</a>
446 <li><a href="#F.2"> F.2 Types</a>
447 <li><a href="#F.3"> F.3 Operators and functions</a>
448 <li><a href="#F.4"> F.4 Floating to integer conversion</a>
449 <li><a href="#F.5"> F.5 Binary-decimal conversion</a>
450 <li><a href="#F.6"> F.6 The return statement</a>
451 <li><a href="#F.7"> F.7 Contracted expressions</a>
452 <li><a href="#F.8"> F.8 Floating-point environment</a>
453 <li><a href="#F.9"> F.9 Optimization</a>
454 <li><a href="#F.10"> F.10 Mathematics <math.h></a>
456 <li><a href="#F.10.1"> F.10.1 Trigonometric functions</a>
457 <li><a href="#F.10.2"> F.10.2 Hyperbolic functions</a>
458 <li><a href="#F.10.3"> F.10.3 Exponential and logarithmic functions</a>
459 <li><a href="#F.10.4"> F.10.4 Power and absolute value functions</a>
460 <li><a href="#F.10.5"> F.10.5 Error and gamma functions</a>
461 <li><a href="#F.10.6"> F.10.6 Nearest integer functions</a>
462 <li><a href="#F.10.7"> F.10.7 Remainder functions</a>
463 <li><a href="#F.10.8"> F.10.8 Manipulation functions</a>
464 <li><a href="#F.10.9"> F.10.9 Maximum, minimum, and positive difference functions</a>
465 <li><a href="#F.10.10"> F.10.10 Floating multiply-add</a>
466 <li><a href="#F.10.11"> F.10.11 Comparison macros</a>
469 <li><a href="#G">Annex G (normative) IEC 60559-compatible complex arithmetic</a>
471 <li><a href="#G.1"> G.1 Introduction</a>
472 <li><a href="#G.2"> G.2 Types</a>
473 <li><a href="#G.3"> G.3 Conventions</a>
474 <li><a href="#G.4"> G.4 Conversions</a>
476 <li><a href="#G.4.1"> G.4.1 Imaginary types</a>
477 <li><a href="#G.4.2"> G.4.2 Real and imaginary</a>
478 <li><a href="#G.4.3"> G.4.3 Imaginary and complex</a>
480 <li><a href="#G.5"> G.5 Binary operators</a>
482 <li><a href="#G.5.1"> G.5.1 Multiplicative operators</a>
483 <li><a href="#G.5.2"> G.5.2 Additive operators</a>
485 <li><a href="#G.6"> G.6 Complex arithmetic <complex.h></a>
487 <li><a href="#G.6.1"> G.6.1 Trigonometric functions</a>
488 <li><a href="#G.6.2"> G.6.2 Hyperbolic functions</a>
489 <li><a href="#G.6.3"> G.6.3 Exponential and logarithmic functions</a>
490 <li><a href="#G.6.4"> G.6.4 Power and absolute-value functions</a>
492 <li><a href="#G.7"> G.7 Type-generic math <tgmath.h></a>
495 <li><a href="#H">Annex H (informative) Language independent arithmetic</a>
497 <li><a href="#H.1"> H.1 Introduction</a>
498 <li><a href="#H.2"> H.2 Types</a>
499 <li><a href="#H.3"> H.3 Notification</a>
501 <li><a href="#I">Annex I (informative) Common warnings</a>
502 <li><a href="#J">Annex J (informative) Portability issues</a>
504 <li><a href="#J.1"> J.1 Unspecified behavior</a>
505 <li><a href="#J.2"> J.2 Undefined behavior</a>
506 <li><a href="#J.3"> J.3 Implementation-defined behavior</a>
507 <li><a href="#J.4"> J.4 Locale-specific behavior</a>
508 <li><a href="#J.5"> J.5 Common extensions</a>
510 <li><a href="#K">Annex K (normative) Bounds-checking interfaces</a>
512 <li><a href="#K.1"> K.1 Background</a>
513 <li><a href="#K.2"> K.2 Scope</a>
514 <li><a href="#K.3"> K.3 Library</a>
516 <li><a href="#K.3.1"> K.3.1 Introduction</a>
518 <li><a href="#K.3.1.1"> K.3.1.1 Standard headers</a>
519 <li><a href="#K.3.1.2"> K.3.1.2 Reserved identifiers</a>
520 <li><a href="#K.3.1.3"> K.3.1.3 Use of errno</a>
521 <li><a href="#K.3.1.4"> K.3.1.4 Runtime-constraint violations</a>
523 <li><a href="#K.3.2"> K.3.2 Errors <errno.h></a>
524 <li><a href="#K.3.3"> K.3.3 Common definitions <stddef.h></a>
525 <li><a href="#K.3.4"> K.3.4 Integer types <stdint.h></a>
526 <li><a href="#K.3.5"> K.3.5 Input/output <stdio.h></a>
528 <li><a href="#K.3.5.1"> K.3.5.1 Operations on files</a>
529 <li><a href="#K.3.5.2"> K.3.5.2 File access functions</a>
530 <li><a href="#K.3.5.3"> K.3.5.3 Formatted input/output functions</a>
531 <li><a href="#K.3.5.4"> K.3.5.4 Character input/output functions</a>
533 <li><a href="#K.3.6"> K.3.6 General utilities <stdlib.h></a>
535 <li><a href="#K.3.6.1"> K.3.6.1 Runtime-constraint handling</a>
536 <li><a href="#K.3.6.2"> K.3.6.2 Communication with the environment</a>
537 <li><a href="#K.3.6.3"> K.3.6.3 Searching and sorting utilities</a>
538 <li><a href="#K.3.6.4"> K.3.6.4 Multibyte/wide character conversion functions</a>
539 <li><a href="#K.3.6.5"> K.3.6.5 Multibyte/wide string conversion functions</a>
541 <li><a href="#K.3.7"> K.3.7 String handling <string.h></a>
543 <li><a href="#K.3.7.1"> K.3.7.1 Copying functions</a>
544 <li><a href="#K.3.7.2"> K.3.7.2 Concatenation functions</a>
545 <li><a href="#K.3.7.3"> K.3.7.3 Search functions</a>
546 <li><a href="#K.3.7.4"> K.3.7.4 Miscellaneous functions</a>
548 <li><a href="#K.3.8"> K.3.8 Date and time <time.h></a>
550 <li><a href="#K.3.8.1"> K.3.8.1 Components of time</a>
551 <li><a href="#K.3.8.2"> K.3.8.2 Time conversion functions</a>
554 <li><a href="#K.3.9"> K.3.9 Extended multibyte and wide character utilities <wchar.h></a>
556 <li><a href="#K.3.9.1"> K.3.9.1 Formatted wide character input/output functions</a>
557 <li><a href="#K.3.9.2"> K.3.9.2 General wide string utilities</a>
558 <li><a href="#K.3.9.3"> K.3.9.3 Extended multibyte/wide character conversion utilities</a>
562 <li><a href="#L">Annex L (normative) Analyzability</a>
564 <li><a href="#L.1"> L.1 Scope</a>
565 <li><a href="#L.2"> L.2 Definitions</a>
566 <li><a href="#L.3"> L.3 Requirements</a>
568 <li><a href="#Bibliography">Bibliography</a>
569 <li><a href="#Index">Index</a>
573 <p><small><a href="#Contents">Contents</a></small>
574 <h2><a name="Foreword" href="#Foreword">Foreword</a></h2>
575 <p><a name="Forewordp1" href="#Forewordp1"><small>1</small></a>
576 ISO (the International Organization for Standardization) and IEC (the International
577 Electrotechnical Commission) form the specialized system for worldwide
578 standardization. National bodies that are member of ISO or IEC participate in the
579 development of International Standards through technical committees established by the
580 respective organization to deal with particular fields of technical activity. ISO and IEC
581 technical committees collaborate in fields of mutual interest. Other international
582 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
583 take part in the work.
584 <p><a name="Forewordp2" href="#Forewordp2"><small>2</small></a>
585 International Standards are drafted in accordance with the rules given in the ISO/IEC
586 Directives, Part 2. This International Standard was drafted in accordance with the fifth
588 <p><a name="Forewordp3" href="#Forewordp3"><small>3</small></a>
589 In the field of information technology, ISO and IEC have established a joint technical
590 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
591 committee are circulated to national bodies for voting. Publication as an International
592 Standard requires approval by at least 75% of the national bodies casting a vote.
593 <p><a name="Forewordp4" href="#Forewordp4"><small>4</small></a>
594 Attention is drawn to the possibility that some of the elements of this document may be
595 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
596 or all such patent rights.
597 <p><a name="Forewordp5" href="#Forewordp5"><small>5</small></a>
598 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
599 Information technology, Subcommittee SC 22, Programming languages, their
600 environments and system software interfaces. The Working Group responsible for this
601 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
602 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
603 standard such as a Rationale for many of the decisions made during its preparation and a
604 log of Defect Reports and Responses.
605 <p><a name="Forewordp6" href="#Forewordp6"><small>6</small></a>
606 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
607 corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
608 ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
610 <li> conditional (optional) features (including some that were previously mandatory)
611 <li> support for multiple threads of execution including an improved memory sequencing
612 model, atomic objects, and thread-local storage (<a href="#7.17"><stdatomic.h></a> and
613 <a href="#7.26"><threads.h></a>)
614 <li> additional floating-point characteristic macros (<a href="#7.7"><float.h></a>)
615 <li> querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
616 <li> Unicode characters and strings (<a href="#7.28"><uchar.h></a>) (originally specified in
617 ISO/IEC TR 19769:2004)
618 <li> type-generic expressions
620 <li> static assertions
621 <li> anonymous structures and unions
622 <li> no-return functions
623 <li> macros to create complex numbers (<a href="#7.3"><complex.h></a>)
624 <li> support for opening files for exclusive access
625 <li> removed the gets function (<a href="#7.21"><stdio.h></a>)
626 <li> added the aligned_alloc, at_quick_exit, and quick_exit functions
627 (<a href="#7.22"><stdlib.h></a>)
628 <li> (conditional) support for bounds-checking interfaces (originally specified in
629 ISO/IEC TR 24731-1:2007)
630 <li> (conditional) support for analyzability
632 <p><a name="Forewordp7" href="#Forewordp7"><small>7</small></a>
633 Major changes in the second edition included:
635 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
637 <li> wide character library support in <a href="#7.29"><wchar.h></a> and <a href="#7.30"><wctype.h></a> (originally
639 <li> more precise aliasing rules via effective type
640 <li> restricted pointers
641 <li> variable length arrays
642 <li> flexible array members
643 <li> static and type qualifiers in parameter array declarators
644 <li> complex (and imaginary) support in <a href="#7.3"><complex.h></a>
645 <li> type-generic math macros in <a href="#7.25"><tgmath.h></a>
646 <li> the long long int type and library functions
647 <li> increased minimum translation limits
648 <li> additional floating-point characteristics in <a href="#7.7"><float.h></a>
649 <li> remove implicit int
650 <li> reliable integer division
651 <li> universal character names (\u and \U)
652 <li> extended identifiers
653 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
656 <li> compound literals
657 <li> designated initializers
659 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
660 <li> remove implicit function declaration
661 <li> preprocessor arithmetic done in intmax_t/uintmax_t
662 <li> mixed declarations and code
663 <li> new block scopes for selection and iteration statements
664 <li> integer constant type rules
665 <li> integer promotion rules
666 <li> macros with a variable number of arguments
667 <li> the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.29"><wchar.h></a>
668 <li> additional math library functions in <a href="#7.12"><math.h></a>
669 <li> treatment of error conditions by math library functions (math_errhandling)
670 <li> floating-point environment access in <a href="#7.6"><fenv.h></a>
671 <li> IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
672 <li> trailing comma allowed in enum declaration
673 <li> %lf conversion specifier allowed in printf
674 <li> inline functions
675 <li> the snprintf family of functions in <a href="#7.21"><stdio.h></a>
676 <li> boolean type in <a href="#7.18"><stdbool.h></a>
677 <li> idempotent type qualifiers
678 <li> empty macro arguments
679 <li> new structure type compatibility rules (tag compatibility)
680 <li> additional predefined macro names
681 <li> _Pragma preprocessing operator
682 <li> standard pragmas
683 <li> __func__ predefined identifier
685 <li> additional strftime conversion specifiers
686 <li> LIA compatibility annex
688 <li> deprecate ungetc at the beginning of a binary file
689 <li> remove deprecation of aliased array parameters
690 <li> conversion of array to pointer not limited to lvalues
691 <li> relaxed constraints on aggregate and union initialization
692 <li> relaxed restrictions on portable header names
693 <li> return without expression not permitted in function that returns a value (and vice
696 <p><a name="Forewordp8" href="#Forewordp8"><small>8</small></a>
697 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H,
698 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
699 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
700 are also for information only.
703 <p><small><a href="#Contents">Contents</a></small>
704 <h2><a name="Introduction" href="#Introduction">Introduction</a></h2>
705 <p><a name="Introductionp1" href="#Introductionp1"><small>1</small></a>
706 With the introduction of new devices and extended character sets, new features may be
707 added to this International Standard. Subclauses in the language and library clauses warn
708 implementors and programmers of usages which, though valid in themselves, may
709 conflict with future additions.
710 <p><a name="Introductionp2" href="#Introductionp2"><small>2</small></a>
711 Certain features are obsolescent, which means that they may be considered for
712 withdrawal in future revisions of this International Standard. They are retained because
713 of their widespread use, but their use in new implementations (for implementation
714 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.31">7.31</a>]) is discouraged.
715 <p><a name="Introductionp3" href="#Introductionp3"><small>3</small></a>
716 This International Standard is divided into four major subdivisions:
718 <li> preliminary elements (clauses 1-4);
719 <li> the characteristics of environments that translate and execute C programs (clause 5);
720 <li> the language syntax, constraints, and semantics (clause 6);
721 <li> the library facilities (clause 7).
723 <p><a name="Introductionp4" href="#Introductionp4"><small>4</small></a>
724 Examples are provided to illustrate possible forms of the constructions described.
725 Footnotes are provided to emphasize consequences of the rules described in that
726 subclause or elsewhere in this International Standard. References are used to refer to
727 other related subclauses. Recommendations are provided to give advice or guidance to
728 implementors. Annexes provide additional information and summarize the information
729 contained in this International Standard. A bibliography lists documents that were
730 referred to during the preparation of the standard.
731 <p><a name="Introductionp5" href="#Introductionp5"><small>5</small></a>
732 The language clause (clause 6) is derived from ''The C Reference Manual''.
733 <p><a name="Introductionp6" href="#Introductionp6"><small>6</small></a>
734 The library clause (clause 7) is based on the 1984 /usr/group Standard.
738 <p><small><a href="#Contents">Contents</a></small>
739 <h1>Programming languages -- C</h1>
744 <p><small><a href="#Contents">Contents</a></small>
745 <h2><a name="1" href="#1">1. Scope</a></h2>
746 <p><a name="1p1" href="#1p1"><small>1</small></a>
747 This International Standard specifies the form and establishes the interpretation of
748 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
750 <li> the representation of C programs;
751 <li> the syntax and constraints of the C language;
752 <li> the semantic rules for interpreting C programs;
753 <li> the representation of input data to be processed by C programs;
754 <li> the representation of output data produced by C programs;
755 <li> the restrictions and limits imposed by a conforming implementation of C.
757 <p><a name="1p2" href="#1p2"><small>2</small></a>
758 This International Standard does not specify
760 <li> the mechanism by which C programs are transformed for use by a data-processing
762 <li> the mechanism by which C programs are invoked for use by a data-processing
764 <li> the mechanism by which input data are transformed for use by a C program;
765 <li> the mechanism by which output data are transformed after being produced by a C
767 <li> the size or complexity of a program and its data that will exceed the capacity of any
768 specific data-processing system or the capacity of a particular processor;
769 <li> all minimal requirements of a data-processing system that is capable of supporting a
770 conforming implementation.
777 <p><small><a name="note1" href="#note1">1)</a> This International Standard is designed to promote the portability of C programs among a variety of
778 data-processing systems. It is intended for use by implementors and programmers.
781 <p><small><a href="#Contents">Contents</a></small>
782 <h2><a name="2" href="#2">2. Normative references</a></h2>
783 <p><a name="2p1" href="#2p1"><small>1</small></a>
784 The following referenced documents are indispensable for the application of this
785 document. For dated references, only the edition cited applies. For undated references,
786 the latest edition of the referenced document (including any amendments) applies.
787 <p><a name="2p2" href="#2p2"><small>2</small></a>
788 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
789 use in the physical sciences and technology.
790 <p><a name="2p3" href="#2p3"><small>3</small></a>
791 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
793 <p><a name="2p4" href="#2p4"><small>4</small></a>
794 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
796 <p><a name="2p5" href="#2p5"><small>5</small></a>
797 ISO 4217, Codes for the representation of currencies and funds.
798 <p><a name="2p6" href="#2p6"><small>6</small></a>
799 ISO 8601, Data elements and interchange formats -- Information interchange --
800 Representation of dates and times.
801 <p><a name="2p7" href="#2p7"><small>7</small></a>
802 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
804 <p><a name="2p8" href="#2p8"><small>8</small></a>
805 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
806 designated IEC 559:1989).
809 <p><small><a href="#Contents">Contents</a></small>
810 <h2><a name="3" href="#3">3. Terms, definitions, and symbols</a></h2>
811 <p><a name="3p1" href="#3p1"><small>1</small></a>
812 For the purposes of this International Standard, the following definitions apply. Other
813 terms are defined where they appear in italic type or on the left side of a syntax rule.
814 Terms explicitly defined in this International Standard are not to be presumed to refer
815 implicitly to similar terms defined elsewhere. Terms not defined in this International
816 Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
817 defined in this International Standard are to be interpreted according to ISO 31-11.
819 <p><small><a href="#Contents">Contents</a></small>
820 <h3><a name="3.1" href="#3.1">3.1</a></h3>
821 <p><a name="3.1p1" href="#3.1p1"><small>1</small></a>
823 <execution-time action> to read or modify the value of an object
824 <p><a name="3.1p2" href="#3.1p2"><small>2</small></a>
825 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
827 <p><a name="3.1p3" href="#3.1p3"><small>3</small></a>
828 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
830 <p><a name="3.1p4" href="#3.1p4"><small>4</small></a>
831 NOTE 3 Expressions that are not evaluated do not access objects.
834 <p><small><a href="#Contents">Contents</a></small>
835 <h3><a name="3.2" href="#3.2">3.2</a></h3>
836 <p><a name="3.2p1" href="#3.2p1"><small>1</small></a>
837 <b> alignment</b><br>
838 requirement that objects of a particular type be located on storage boundaries with
839 addresses that are particular multiples of a byte address
841 <p><small><a href="#Contents">Contents</a></small>
842 <h3><a name="3.3" href="#3.3">3.3</a></h3>
843 <p><a name="3.3p1" href="#3.3p1"><small>1</small></a>
846 actual parameter (deprecated)
847 expression in the comma-separated list bounded by the parentheses in a function call
848 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
849 by the parentheses in a function-like macro invocation
851 <p><small><a href="#Contents">Contents</a></small>
852 <h3><a name="3.4" href="#3.4">3.4</a></h3>
853 <p><a name="3.4p1" href="#3.4p1"><small>1</small></a>
855 external appearance or action
857 <p><small><a href="#Contents">Contents</a></small>
858 <h4><a name="3.4.1" href="#3.4.1">3.4.1</a></h4>
859 <p><a name="3.4.1p1" href="#3.4.1p1"><small>1</small></a>
860 <b> implementation-defined behavior</b><br>
861 unspecified behavior where each implementation documents how the choice is made
862 <p><a name="3.4.1p2" href="#3.4.1p2"><small>2</small></a>
863 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
864 when a signed integer is shifted right.
867 <p><small><a href="#Contents">Contents</a></small>
868 <h4><a name="3.4.2" href="#3.4.2">3.4.2</a></h4>
869 <p><a name="3.4.2p1" href="#3.4.2p1"><small>1</small></a>
870 <b> locale-specific behavior</b><br>
871 behavior that depends on local conventions of nationality, culture, and language that each
872 implementation documents
874 <p><a name="3.4.2p2" href="#3.4.2p2"><small>2</small></a>
875 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
876 characters other than the 26 lowercase Latin letters.
879 <p><small><a href="#Contents">Contents</a></small>
880 <h4><a name="3.4.3" href="#3.4.3">3.4.3</a></h4>
881 <p><a name="3.4.3p1" href="#3.4.3p1"><small>1</small></a>
882 <b> undefined behavior</b><br>
883 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
884 for which this International Standard imposes no requirements
885 <p><a name="3.4.3p2" href="#3.4.3p2"><small>2</small></a>
886 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
887 results, to behaving during translation or program execution in a documented manner characteristic of the
888 environment (with or without the issuance of a diagnostic message), to terminating a translation or
889 execution (with the issuance of a diagnostic message).
891 <p><a name="3.4.3p3" href="#3.4.3p3"><small>3</small></a>
892 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
895 <p><small><a href="#Contents">Contents</a></small>
896 <h4><a name="3.4.4" href="#3.4.4">3.4.4</a></h4>
897 <p><a name="3.4.4p1" href="#3.4.4p1"><small>1</small></a>
898 <b> unspecified behavior</b><br>
899 use of an unspecified value, or other behavior where this International Standard provides
900 two or more possibilities and imposes no further requirements on which is chosen in any
902 <p><a name="3.4.4p2" href="#3.4.4p2"><small>2</small></a>
903 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
907 <p><small><a href="#Contents">Contents</a></small>
908 <h3><a name="3.5" href="#3.5">3.5</a></h3>
909 <p><a name="3.5p1" href="#3.5p1"><small>1</small></a>
911 unit of data storage in the execution environment large enough to hold an object that may
912 have one of two values
913 <p><a name="3.5p2" href="#3.5p2"><small>2</small></a>
914 NOTE It need not be possible to express the address of each individual bit of an object.
917 <p><small><a href="#Contents">Contents</a></small>
918 <h3><a name="3.6" href="#3.6">3.6</a></h3>
919 <p><a name="3.6p1" href="#3.6p1"><small>1</small></a>
921 addressable unit of data storage large enough to hold any member of the basic character
922 set of the execution environment
923 <p><a name="3.6p2" href="#3.6p2"><small>2</small></a>
924 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
926 <p><a name="3.6p3" href="#3.6p3"><small>3</small></a>
927 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
928 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
932 <p><small><a href="#Contents">Contents</a></small>
933 <h3><a name="3.7" href="#3.7">3.7</a></h3>
934 <p><a name="3.7p1" href="#3.7p1"><small>1</small></a>
935 <b> character</b><br>
936 <abstract> member of a set of elements used for the organization, control, or
937 representation of data
939 <p><small><a href="#Contents">Contents</a></small>
940 <h4><a name="3.7.1" href="#3.7.1">3.7.1</a></h4>
941 <p><a name="3.7.1p1" href="#3.7.1p1"><small>1</small></a>
942 <b> character</b><br>
943 single-byte character
944 <C> bit representation that fits in a byte
947 <p><small><a href="#Contents">Contents</a></small>
948 <h4><a name="3.7.2" href="#3.7.2">3.7.2</a></h4>
949 <p><a name="3.7.2p1" href="#3.7.2p1"><small>1</small></a>
950 <b> multibyte character</b><br>
951 sequence of one or more bytes representing a member of the extended character set of
952 either the source or the execution environment
953 <p><a name="3.7.2p2" href="#3.7.2p2"><small>2</small></a>
954 NOTE The extended character set is a superset of the basic character set.
957 <p><small><a href="#Contents">Contents</a></small>
958 <h4><a name="3.7.3" href="#3.7.3">3.7.3</a></h4>
959 <p><a name="3.7.3p1" href="#3.7.3p1"><small>1</small></a>
960 <b> wide character</b><br>
961 value representable by an object of type wchar_t, capable of representing any character
962 in the current locale
964 <p><small><a href="#Contents">Contents</a></small>
965 <h3><a name="3.8" href="#3.8">3.8</a></h3>
966 <p><a name="3.8p1" href="#3.8p1"><small>1</small></a>
967 <b> constraint</b><br>
968 restriction, either syntactic or semantic, by which the exposition of language elements is
971 <p><small><a href="#Contents">Contents</a></small>
972 <h3><a name="3.9" href="#3.9">3.9</a></h3>
973 <p><a name="3.9p1" href="#3.9p1"><small>1</small></a>
974 <b> correctly rounded result</b><br>
975 representation in the result format that is nearest in value, subject to the current rounding
976 mode, to what the result would be given unlimited range and precision
978 <p><small><a href="#Contents">Contents</a></small>
979 <h3><a name="3.10" href="#3.10">3.10</a></h3>
980 <p><a name="3.10p1" href="#3.10p1"><small>1</small></a>
981 <b> diagnostic message</b><br>
982 message belonging to an implementation-defined subset of the implementation's message
985 <p><small><a href="#Contents">Contents</a></small>
986 <h3><a name="3.11" href="#3.11">3.11</a></h3>
987 <p><a name="3.11p1" href="#3.11p1"><small>1</small></a>
988 <b> forward reference</b><br>
989 reference to a later subclause of this International Standard that contains additional
990 information relevant to this subclause
992 <p><small><a href="#Contents">Contents</a></small>
993 <h3><a name="3.12" href="#3.12">3.12</a></h3>
994 <p><a name="3.12p1" href="#3.12p1"><small>1</small></a>
995 <b> implementation</b><br>
996 particular set of software, running in a particular translation environment under particular
997 control options, that performs translation of programs for, and supports execution of
998 functions in, a particular execution environment
1000 <p><small><a href="#Contents">Contents</a></small>
1001 <h3><a name="3.13" href="#3.13">3.13</a></h3>
1002 <p><a name="3.13p1" href="#3.13p1"><small>1</small></a>
1003 <b> implementation limit</b><br>
1004 restriction imposed upon programs by the implementation
1006 <p><small><a href="#Contents">Contents</a></small>
1007 <h3><a name="3.14" href="#3.14">3.14</a></h3>
1008 <p><a name="3.14p1" href="#3.14p1"><small>1</small></a>
1009 <b> memory location</b><br>
1010 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
1013 <p><a name="3.14p2" href="#3.14p2"><small>2</small></a>
1014 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
1017 <p><a name="3.14p3" href="#3.14p3"><small>3</small></a>
1018 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
1019 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
1020 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
1021 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
1022 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
1023 intervening bit-fields happen to be.
1025 <p><a name="3.14p4" href="#3.14p4"><small>4</small></a>
1026 EXAMPLE A structure declared as
1030 int b:5, c:11, :0, d:8;
1031 struct { int ee:8; } e;
1034 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
1035 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
1036 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
1037 modified, but b and a, for example, can be.
1040 <p><small><a href="#Contents">Contents</a></small>
1041 <h3><a name="3.15" href="#3.15">3.15</a></h3>
1042 <p><a name="3.15p1" href="#3.15p1"><small>1</small></a>
1044 region of data storage in the execution environment, the contents of which can represent
1046 <p><a name="3.15p2" href="#3.15p2"><small>2</small></a>
1047 NOTE When referenced, an object may be interpreted as having a particular type; see <a href="#6.3.2.1">6.3.2.1</a>.
1050 <p><small><a href="#Contents">Contents</a></small>
1051 <h3><a name="3.16" href="#3.16">3.16</a></h3>
1052 <p><a name="3.16p1" href="#3.16p1"><small>1</small></a>
1053 <b> parameter</b><br>
1055 formal argument (deprecated)
1056 object declared as part of a function declaration or definition that acquires a value on
1057 entry to the function, or an identifier from the comma-separated list bounded by the
1058 parentheses immediately following the macro name in a function-like macro definition
1060 <p><small><a href="#Contents">Contents</a></small>
1061 <h3><a name="3.17" href="#3.17">3.17</a></h3>
1062 <p><a name="3.17p1" href="#3.17p1"><small>1</small></a>
1063 <b> recommended practice</b><br>
1064 specification that is strongly recommended as being in keeping with the intent of the
1065 standard, but that may be impractical for some implementations
1067 <p><small><a href="#Contents">Contents</a></small>
1068 <h3><a name="3.18" href="#3.18">3.18</a></h3>
1069 <p><a name="3.18p1" href="#3.18p1"><small>1</small></a>
1070 <b> runtime-constraint</b><br>
1071 requirement on a program when calling a library function
1072 <p><a name="3.18p2" href="#3.18p2"><small>2</small></a>
1073 NOTE 1 Despite the similar terms, a runtime-constraint is not a kind of constraint as defined by <a href="#3.8">3.8</a>, and
1074 need not be diagnosed at translation time.
1076 <p><a name="3.18p3" href="#3.18p3"><small>3</small></a>
1077 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
1078 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
1081 <p><small><a href="#Contents">Contents</a></small>
1082 <h3><a name="3.19" href="#3.19">3.19</a></h3>
1083 <p><a name="3.19p1" href="#3.19p1"><small>1</small></a>
1085 precise meaning of the contents of an object when interpreted as having a specific type
1087 <p><small><a href="#Contents">Contents</a></small>
1088 <h4><a name="3.19.1" href="#3.19.1">3.19.1</a></h4>
1089 <p><a name="3.19.1p1" href="#3.19.1p1"><small>1</small></a>
1090 <b> implementation-defined value</b><br>
1091 unspecified value where each implementation documents how the choice is made
1093 <p><small><a href="#Contents">Contents</a></small>
1094 <h4><a name="3.19.2" href="#3.19.2">3.19.2</a></h4>
1095 <p><a name="3.19.2p1" href="#3.19.2p1"><small>1</small></a>
1096 <b> indeterminate value</b><br>
1097 either an unspecified value or a trap representation
1099 <p><small><a href="#Contents">Contents</a></small>
1100 <h4><a name="3.19.3" href="#3.19.3">3.19.3</a></h4>
1101 <p><a name="3.19.3p1" href="#3.19.3p1"><small>1</small></a>
1102 <b> unspecified value</b><br>
1103 valid value of the relevant type where this International Standard imposes no
1104 requirements on which value is chosen in any instance
1105 <p><a name="3.19.3p2" href="#3.19.3p2"><small>2</small></a>
1106 NOTE An unspecified value cannot be a trap representation.
1109 <p><small><a href="#Contents">Contents</a></small>
1110 <h4><a name="3.19.4" href="#3.19.4">3.19.4</a></h4>
1111 <p><a name="3.19.4p1" href="#3.19.4p1"><small>1</small></a>
1112 <b> trap representation</b><br>
1113 an object representation that need not represent a value of the object type
1115 <p><small><a href="#Contents">Contents</a></small>
1116 <h4><a name="3.19.5" href="#3.19.5">3.19.5</a></h4>
1117 <p><a name="3.19.5p1" href="#3.19.5p1"><small>1</small></a>
1118 <b> perform a trap</b><br>
1119 interrupt execution of the program such that no further operations are performed
1120 <p><a name="3.19.5p2" href="#3.19.5p2"><small>2</small></a>
1121 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
1122 ''representation'', this is the intended usage.<sup><a href="#note2"><b>2)</b></a></sup>
1126 <p><small><a name="note2" href="#note2">2)</a> For example, ''Trapping or stopping (if supported) is disabled...'' (<a href="#F.8.2">F.8.2</a>). Note that fetching a trap
1127 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
1130 <p><small><a href="#Contents">Contents</a></small>
1131 <h3><a name="3.20" href="#3.20">3.20</a></h3>
1132 <p><a name="3.20p1" href="#3.20p1"><small>1</small></a>
1134 ceiling of x: the least integer greater than or equal to x
1135 <p><a name="3.20p2" href="#3.20p2"><small>2</small></a>
1136 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
1139 <p><small><a href="#Contents">Contents</a></small>
1140 <h3><a name="3.21" href="#3.21">3.21</a></h3>
1141 <p><a name="3.21p1" href="#3.21p1"><small>1</small></a>
1143 floor of x: the greatest integer less than or equal to x
1144 <p><a name="3.21p2" href="#3.21p2"><small>2</small></a>
1145 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
1152 <p><small><a href="#Contents">Contents</a></small>
1153 <h2><a name="4" href="#4">4. Conformance</a></h2>
1154 <p><a name="4p1" href="#4p1"><small>1</small></a>
1155 In this International Standard, ''shall'' is to be interpreted as a requirement on an
1156 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
1158 <p><a name="4p2" href="#4p2"><small>2</small></a>
1159 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
1160 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
1161 indicated in this International Standard by the words ''undefined behavior'' or by the
1162 omission of any explicit definition of behavior. There is no difference in emphasis among
1163 these three; they all describe ''behavior that is undefined''.
1164 <p><a name="4p3" href="#4p3"><small>3</small></a>
1165 A program that is correct in all other aspects, operating on correct data, containing
1166 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
1167 <p><a name="4p4" href="#4p4"><small>4</small></a>
1168 The implementation shall not successfully translate a preprocessing translation unit
1169 containing a #error preprocessing directive unless it is part of a group skipped by
1170 conditional inclusion.
1171 <p><a name="4p5" href="#4p5"><small>5</small></a>
1172 A strictly conforming program shall use only those features of the language and library
1173 specified in this International Standard.<sup><a href="#note3"><b>3)</b></a></sup> It shall not produce output dependent on any
1174 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
1175 minimum implementation limit.
1176 <p><a name="4p6" href="#4p6"><small>6</small></a>
1177 The two forms of conforming implementation are hosted and freestanding. A conforming
1178 hosted implementation shall accept any strictly conforming program. A conforming
1179 freestanding implementation shall accept any strictly conforming program in which the *
1180 use of the features specified in the library clause (clause 7) is confined to the contents of
1181 the standard headers <a href="#7.7"><float.h></a>, <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdalign.h></a>,
1182 <a href="#7.16"><stdarg.h></a>, <a href="#7.18"><stdbool.h></a>, <a href="#7.19"><stddef.h></a>, <a href="#7.20"><stdint.h></a>, and
1183 <a href="#7.23"><stdnoreturn.h></a>. A conforming implementation may have extensions (including
1184 additional library functions), provided they do not alter the behavior of any strictly
1185 conforming program.<sup><a href="#note4"><b>4)</b></a></sup>
1190 <p><a name="4p7" href="#4p7"><small>7</small></a>
1191 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note5"><b>5)</b></a></sup>
1192 <p><a name="4p8" href="#4p8"><small>8</small></a>
1193 An implementation shall be accompanied by a document that defines all implementation-
1194 defined and locale-specific characteristics and all extensions.
1195 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
1196 characteristics of floating types <a href="#7.7"><float.h></a> (<a href="#7.7">7.7</a>), alternative spellings <a href="#7.9"><iso646.h></a>
1197 (<a href="#7.9">7.9</a>), sizes of integer types <a href="#7.10"><limits.h></a> (<a href="#7.10">7.10</a>), alignment <a href="#7.15"><stdalign.h></a> (<a href="#7.15">7.15</a>),
1198 variable arguments <a href="#7.16"><stdarg.h></a> (<a href="#7.16">7.16</a>), boolean type and values <a href="#7.18"><stdbool.h></a>
1199 (<a href="#7.18">7.18</a>), common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>),
1200 <a href="#7.23"><stdnoreturn.h></a> (<a href="#7.23">7.23</a>).
1208 <p><small><a name="note3" href="#note3">3)</a> A strictly conforming program can use conditional features (see <a href="#6.10.8.3">6.10.8.3</a>) provided the use is guarded
1209 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
1212 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
1214 fesetround(FE_UPWARD);
1220 <p><small><a name="note4" href="#note4">4)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
1221 reserved in this International Standard.
1223 <p><small><a name="note5" href="#note5">5)</a> Strictly conforming programs are intended to be maximally portable among conforming
1224 implementations. Conforming programs may depend upon nonportable features of a conforming
1228 <p><small><a href="#Contents">Contents</a></small>
1229 <h2><a name="5" href="#5">5. Environment</a></h2>
1230 <p><a name="5p1" href="#5p1"><small>1</small></a>
1231 An implementation translates C source files and executes C programs in two data-
1232 processing-system environments, which will be called the translation environment and
1233 the execution environment in this International Standard. Their characteristics define and
1234 constrain the results of executing conforming C programs constructed according to the
1235 syntactic and semantic rules for conforming implementations.
1236 <p><b> Forward references</b>: In this clause, only a few of many possible forward references
1239 <p><small><a href="#Contents">Contents</a></small>
1240 <h3><a name="5.1" href="#5.1">5.1 Conceptual models</a></h3>
1242 <p><small><a href="#Contents">Contents</a></small>
1243 <h4><a name="5.1.1" href="#5.1.1">5.1.1 Translation environment</a></h4>
1245 <p><small><a href="#Contents">Contents</a></small>
1246 <h5><a name="5.1.1.1" href="#5.1.1.1">5.1.1.1 Program structure</a></h5>
1247 <p><a name="5.1.1.1p1" href="#5.1.1.1p1"><small>1</small></a>
1248 A C program need not all be translated at the same time. The text of the program is kept
1249 in units called source files, (or preprocessing files) in this International Standard. A
1250 source file together with all the headers and source files included via the preprocessing
1251 directive #include is known as a preprocessing translation unit. After preprocessing, a
1252 preprocessing translation unit is called a translation unit. Previously translated translation
1253 units may be preserved individually or in libraries. The separate translation units of a
1254 program communicate by (for example) calls to functions whose identifiers have external
1255 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
1256 of data files. Translation units may be separately translated and then later linked to
1257 produce an executable program.
1258 <p><b> Forward references</b>: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
1259 preprocessing directives (<a href="#6.10">6.10</a>).
1261 <p><small><a href="#Contents">Contents</a></small>
1262 <h5><a name="5.1.1.2" href="#5.1.1.2">5.1.1.2 Translation phases</a></h5>
1263 <p><a name="5.1.1.2p1" href="#5.1.1.2p1"><small>1</small></a>
1264 The precedence among the syntax rules of translation is specified by the following
1265 phases.<sup><a href="#note6"><b>6)</b></a></sup>
1267 <li> Physical source file multibyte characters are mapped, in an implementation-
1268 defined manner, to the source character set (introducing new-line characters for
1269 end-of-line indicators) if necessary. Trigraph sequences are replaced by
1270 corresponding single-character internal representations.
1275 <li> Each instance of a backslash character (\) immediately followed by a new-line
1276 character is deleted, splicing physical source lines to form logical source lines.
1277 Only the last backslash on any physical source line shall be eligible for being part
1278 of such a splice. A source file that is not empty shall end in a new-line character,
1279 which shall not be immediately preceded by a backslash character before any such
1280 splicing takes place.
1281 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note7"><b>7)</b></a></sup> and sequences of
1282 white-space characters (including comments). A source file shall not end in a
1283 partial preprocessing token or in a partial comment. Each comment is replaced by
1284 one space character. New-line characters are retained. Whether each nonempty
1285 sequence of white-space characters other than new-line is retained or replaced by
1286 one space character is implementation-defined.
1287 <li> Preprocessing directives are executed, macro invocations are expanded, and
1288 _Pragma unary operator expressions are executed. If a character sequence that
1289 matches the syntax of a universal character name is produced by token
1290 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1291 directive causes the named header or source file to be processed from phase 1
1292 through phase 4, recursively. All preprocessing directives are then deleted.
1293 <li> Each source character set member and escape sequence in character constants and
1294 string literals is converted to the corresponding member of the execution character
1295 set; if there is no corresponding member, it is converted to an implementation-
1296 defined member other than the null (wide) character.<sup><a href="#note8"><b>8)</b></a></sup>
1297 <li> Adjacent string literal tokens are concatenated.
1298 <li> White-space characters separating tokens are no longer significant. Each
1299 preprocessing token is converted into a token. The resulting tokens are
1300 syntactically and semantically analyzed and translated as a translation unit.
1301 <li> All external object and function references are resolved. Library components are
1302 linked to satisfy external references to functions and objects not defined in the
1303 current translation. All such translator output is collected into a program image
1304 which contains information needed for execution in its execution environment.
1306 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
1307 preprocessing directives (<a href="#6.10">6.10</a>), trigraph sequences (<a href="#5.2.1.1">5.2.1.1</a>), external definitions (<a href="#6.9">6.9</a>).
1314 <p><small><a name="note6" href="#note6">6)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
1315 together in practice. Source files, translation units, and translated translation units need not
1316 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1317 and any external representation. The description is conceptual only, and does not specify any
1318 particular implementation.
1320 <p><small><a name="note7" href="#note7">7)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
1321 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1323 <p><small><a name="note8" href="#note8">8)</a> An implementation need not convert all non-corresponding source characters to the same execution
1327 <p><small><a href="#Contents">Contents</a></small>
1328 <h5><a name="5.1.1.3" href="#5.1.1.3">5.1.1.3 Diagnostics</a></h5>
1329 <p><a name="5.1.1.3p1" href="#5.1.1.3p1"><small>1</small></a>
1330 A conforming implementation shall produce at least one diagnostic message (identified in
1331 an implementation-defined manner) if a preprocessing translation unit or translation unit
1332 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1333 specified as undefined or implementation-defined. Diagnostic messages need not be
1334 produced in other circumstances.<sup><a href="#note9"><b>9)</b></a></sup>
1335 <p><a name="5.1.1.3p2" href="#5.1.1.3p2"><small>2</small></a>
1336 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1341 because in those cases where wording in this International Standard describes the behavior for a construct
1342 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1346 <p><small><a name="note9" href="#note9">9)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1347 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1348 valid program is still correctly translated. It may also successfully translate an invalid program.
1351 <p><small><a href="#Contents">Contents</a></small>
1352 <h4><a name="5.1.2" href="#5.1.2">5.1.2 Execution environments</a></h4>
1353 <p><a name="5.1.2p1" href="#5.1.2p1"><small>1</small></a>
1354 Two execution environments are defined: freestanding and hosted. In both cases,
1355 program startup occurs when a designated C function is called by the execution
1356 environment. All objects with static storage duration shall be initialized (set to their
1357 initial values) before program startup. The manner and timing of such initialization are
1358 otherwise unspecified. Program termination returns control to the execution
1360 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.9">6.7.9</a>).
1362 <p><small><a href="#Contents">Contents</a></small>
1363 <h5><a name="5.1.2.1" href="#5.1.2.1">5.1.2.1 Freestanding environment</a></h5>
1364 <p><a name="5.1.2.1p1" href="#5.1.2.1p1"><small>1</small></a>
1365 In a freestanding environment (in which C program execution may take place without any
1366 benefit of an operating system), the name and type of the function called at program
1367 startup are implementation-defined. Any library facilities available to a freestanding
1368 program, other than the minimal set required by clause 4, are implementation-defined.
1369 <p><a name="5.1.2.1p2" href="#5.1.2.1p2"><small>2</small></a>
1370 The effect of program termination in a freestanding environment is implementation-
1373 <p><small><a href="#Contents">Contents</a></small>
1374 <h5><a name="5.1.2.2" href="#5.1.2.2">5.1.2.2 Hosted environment</a></h5>
1375 <p><a name="5.1.2.2p1" href="#5.1.2.2p1"><small>1</small></a>
1376 A hosted environment need not be provided, but shall conform to the following
1377 specifications if present.
1384 <p><small><a href="#Contents">Contents</a></small>
1385 <h5><a name="5.1.2.2.1" href="#5.1.2.2.1">5.1.2.2.1 Program startup</a></h5>
1386 <p><a name="5.1.2.2.1p1" href="#5.1.2.2.1p1"><small>1</small></a>
1387 The function called at program startup is named main. The implementation declares no
1388 prototype for this function. It shall be defined with a return type of int and with no
1391 int main(void) { /* ... */ }
1393 or with two parameters (referred to here as argc and argv, though any names may be
1394 used, as they are local to the function in which they are declared):
1396 int main(int argc, char *argv[]) { /* ... */ }
1398 or equivalent;<sup><a href="#note10"><b>10)</b></a></sup> or in some other implementation-defined manner.
1399 <p><a name="5.1.2.2.1p2" href="#5.1.2.2.1p2"><small>2</small></a>
1400 If they are declared, the parameters to the main function shall obey the following
1403 <li> The value of argc shall be nonnegative.
1404 <li> argv[argc] shall be a null pointer.
1405 <li> If the value of argc is greater than zero, the array members argv[0] through
1406 argv[argc-1] inclusive shall contain pointers to strings, which are given
1407 implementation-defined values by the host environment prior to program startup. The
1408 intent is to supply to the program information determined prior to program startup
1409 from elsewhere in the hosted environment. If the host environment is not capable of
1410 supplying strings with letters in both uppercase and lowercase, the implementation
1411 shall ensure that the strings are received in lowercase.
1412 <li> If the value of argc is greater than zero, the string pointed to by argv[0]
1413 represents the program name; argv[0][0] shall be the null character if the
1414 program name is not available from the host environment. If the value of argc is
1415 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1416 represent the program parameters.
1417 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1418 be modifiable by the program, and retain their last-stored values between program
1419 startup and program termination.
1423 <p><small><a name="note10" href="#note10">10)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1424 char ** argv, and so on.
1427 <p><small><a href="#Contents">Contents</a></small>
1428 <h5><a name="5.1.2.2.2" href="#5.1.2.2.2">5.1.2.2.2 Program execution</a></h5>
1429 <p><a name="5.1.2.2.2p1" href="#5.1.2.2.2p1"><small>1</small></a>
1430 In a hosted environment, a program may use all the functions, macros, type definitions,
1431 and objects described in the library clause (clause 7).
1438 <p><small><a href="#Contents">Contents</a></small>
1439 <h5><a name="5.1.2.2.3" href="#5.1.2.2.3">5.1.2.2.3 Program termination</a></h5>
1440 <p><a name="5.1.2.2.3p1" href="#5.1.2.2.3p1"><small>1</small></a>
1441 If the return type of the main function is a type compatible with int, a return from the
1442 initial call to the main function is equivalent to calling the exit function with the value
1443 returned by the main function as its argument;<sup><a href="#note11"><b>11)</b></a></sup> reaching the } that terminates the
1444 main function returns a value of 0. If the return type is not compatible with int, the
1445 termination status returned to the host environment is unspecified.
1446 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.22.4.4">7.22.4.4</a>).
1449 <p><small><a name="note11" href="#note11">11)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1450 will have ended in the former case, even where they would not have in the latter.
1453 <p><small><a href="#Contents">Contents</a></small>
1454 <h5><a name="5.1.2.3" href="#5.1.2.3">5.1.2.3 Program execution</a></h5>
1455 <p><a name="5.1.2.3p1" href="#5.1.2.3p1"><small>1</small></a>
1456 The semantic descriptions in this International Standard describe the behavior of an
1457 abstract machine in which issues of optimization are irrelevant.
1458 <p><a name="5.1.2.3p2" href="#5.1.2.3p2"><small>2</small></a>
1459 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1460 that does any of those operations are all side effects,<sup><a href="#note12"><b>12)</b></a></sup> which are changes in the state of
1461 the execution environment. Evaluation of an expression in general includes both value
1462 computations and initiation of side effects. Value computation for an lvalue expression
1463 includes determining the identity of the designated object.
1464 <p><a name="5.1.2.3p3" href="#5.1.2.3p3"><small>3</small></a>
1465 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1466 executed by a single thread, which induces a partial order among those evaluations.
1467 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1468 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1469 sequenced after A.) If A is not sequenced before or after B, then A and B are
1470 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1471 either before or after B, but it is unspecified which.<sup><a href="#note13"><b>13)</b></a></sup> The presence of a sequence point
1472 between the evaluation of expressions A and B implies that every value computation and
1473 side effect associated with A is sequenced before every value computation and side effect
1474 associated with B. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1475 <p><a name="5.1.2.3p4" href="#5.1.2.3p4"><small>4</small></a>
1476 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1477 actual implementation need not evaluate part of an expression if it can deduce that its
1478 value is not used and that no needed side effects are produced (including any caused by
1481 calling a function or accessing a volatile object).
1482 <p><a name="5.1.2.3p5" href="#5.1.2.3p5"><small>5</small></a>
1483 When the processing of the abstract machine is interrupted by receipt of a signal, the
1484 values of objects that are neither lock-free atomic objects nor of type volatile
1485 sig_atomic_t are unspecified, as is the state of the floating-point environment. The
1486 value of any object modified by the handler that is neither a lock-free atomic object nor of
1487 type volatile sig_atomic_t becomes indeterminate when the handler exits, as
1488 does the state of the floating-point environment if it is modified by the handler and not
1489 restored to its original state.
1490 <p><a name="5.1.2.3p6" href="#5.1.2.3p6"><small>6</small></a>
1491 The least requirements on a conforming implementation are:
1493 <li> Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1495 <li> At program termination, all data written into files shall be identical to the result that
1496 execution of the program according to the abstract semantics would have produced.
1497 <li> The input and output dynamics of interactive devices shall take place as specified in
1498 <a href="#7.21.3">7.21.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1499 appear as soon as possible, to ensure that prompting messages actually appear prior to
1500 a program waiting for input.
1502 This is the observable behavior of the program.
1503 <p><a name="5.1.2.3p7" href="#5.1.2.3p7"><small>7</small></a>
1504 What constitutes an interactive device is implementation-defined.
1505 <p><a name="5.1.2.3p8" href="#5.1.2.3p8"><small>8</small></a>
1506 More stringent correspondences between abstract and actual semantics may be defined by
1507 each implementation.
1508 <p><a name="5.1.2.3p9" href="#5.1.2.3p9"><small>9</small></a>
1509 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1510 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1511 abstract semantics. The keyword volatile would then be redundant.
1512 <p><a name="5.1.2.3p10" href="#5.1.2.3p10"><small>10</small></a>
1513 Alternatively, an implementation might perform various optimizations within each translation unit, such
1514 that the actual semantics would agree with the abstract semantics only when making function calls across
1515 translation unit boundaries. In such an implementation, at the time of each function entry and function
1516 return where the calling function and the called function are in different translation units, the values of all
1517 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1518 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1519 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1520 type of implementation, objects referred to by interrupt service routines activated by the signal function
1521 would require explicit specification of volatile storage, as well as other implementation-defined
1524 <p><a name="5.1.2.3p11" href="#5.1.2.3p11"><small>11</small></a>
1525 EXAMPLE 2 In executing the fragment
1531 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1532 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1534 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1535 produce the same result, possibly omitting the promotions.
1537 <p><a name="5.1.2.3p12" href="#5.1.2.3p12"><small>12</small></a>
1538 EXAMPLE 3 Similarly, in the fragment
1545 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1546 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1547 were replaced by the constant 2.0, which has type double).
1549 <p><a name="5.1.2.3p13" href="#5.1.2.3p13"><small>13</small></a>
1550 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1551 semantics. Values are independent of whether they are represented in a register or in memory. For
1552 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1553 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1554 perform their specified conversion. For the fragment
1558 d1 = f = expression;
1559 d2 = (float) expression;
1561 the values assigned to d1 and d2 are required to have been converted to float.
1563 <p><a name="5.1.2.3p14" href="#5.1.2.3p14"><small>14</small></a>
1564 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1565 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1566 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1567 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1568 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1569 numbers are often not valid (see <a href="#F.9">F.9</a>).
1573 x = (x * y) * z; // not equivalent to x *= y * z;
1574 z = (x - y) + y ; // not equivalent to z = x;
1575 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1576 y = x / 5.0; // not equivalent to y = x * 0.2;
1579 <p><a name="5.1.2.3p15" href="#5.1.2.3p15"><small>15</small></a>
1580 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1584 a = a + 32760 + b + 5;
1586 the expression statement behaves exactly the same as
1588 a = (((a + 32760) + b) + 5);
1590 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1591 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1592 which overflows produce an explicit trap and in which the range of values representable by an int is
1593 [-32768, +32767], the implementation cannot rewrite this expression as
1595 a = ((a + b) + 32765);
1597 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1599 while the original expression would not; nor can the expression be rewritten either as
1601 a = ((a + 32765) + b);
1605 a = (a + (b + 32765));
1607 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1608 in which overflow silently generates some value and where positive and negative overflows cancel, the
1609 above expression statement can be rewritten by the implementation in any of the above ways because the
1610 same result will occur.
1612 <p><a name="5.1.2.3p16" href="#5.1.2.3p16"><small>16</small></a>
1613 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1616 #include <a href="#7.21"><stdio.h></a>
1620 sum = sum * 10 - '0' + (*p++ = getchar());
1622 the expression statement is grouped as if it were written as
1624 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
1626 but the actual increment of p can occur at any time between the previous sequence point and the next
1627 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1630 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>), statements (<a href="#6.8">6.8</a>), floating-
1631 point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), the signal function (<a href="#7.14">7.14</a>), files (<a href="#7.21.3">7.21.3</a>).
1634 <p><small><a name="note12" href="#note12">12)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1635 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1636 values of floating-point operations. Implementations that support such floating-point state are
1637 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1638 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1639 effects matter, freeing the implementations in other cases.
1641 <p><small><a name="note13" href="#note13">13)</a> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1642 cannot interleave, but can be executed in any order.
1645 <p><small><a href="#Contents">Contents</a></small>
1646 <h5><a name="5.1.2.4" href="#5.1.2.4">5.1.2.4 Multi-threaded executions and data races</a></h5>
1647 <p><a name="5.1.2.4p1" href="#5.1.2.4p1"><small>1</small></a>
1648 Under a hosted implementation, a program can have more than one thread of execution
1649 (or thread) running concurrently. The execution of each thread proceeds as defined by
1650 the remainder of this standard. The execution of the entire program consists of an
1651 execution of all of its threads.<sup><a href="#note14"><b>14)</b></a></sup> Under a freestanding implementation, it is
1652 implementation-defined whether a program can have more than one thread of execution.
1653 <p><a name="5.1.2.4p2" href="#5.1.2.4p2"><small>2</small></a>
1654 The value of an object visible to a thread T at a particular point is the initial value of the
1655 object, a value stored in the object by T , or a value stored in the object by another thread,
1656 according to the rules below.
1657 <p><a name="5.1.2.4p3" href="#5.1.2.4p3"><small>3</small></a>
1658 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1659 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1660 implicitly supports a simpler view for more restricted programs.
1662 <p><a name="5.1.2.4p4" href="#5.1.2.4p4"><small>4</small></a>
1663 Two expression evaluations conflict if one of them modifies a memory location and the
1664 other one reads or modifies the same memory location.
1668 <p><a name="5.1.2.4p5" href="#5.1.2.4p5"><small>5</small></a>
1669 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1670 (<a href="#7.26.4">7.26.4</a>) that are specially identified as synchronization operations. These operations play
1671 a special role in making assignments in one thread visible to another. A synchronization
1672 operation on one or more memory locations is either an acquire operation, a release
1673 operation, both an acquire and release operation, or a consume operation. A
1674 synchronization operation without an associated memory location is a fence and can be
1675 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1676 there are relaxed atomic operations, which are not synchronization operations, and
1677 atomic read-modify-write operations, which have special characteristics.
1678 <p><a name="5.1.2.4p6" href="#5.1.2.4p6"><small>6</small></a>
1679 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1680 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1681 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1682 on other memory locations to become visible to other threads that later perform an acquire or consume
1683 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1684 synchronization operations, they cannot contribute to data races.
1686 <p><a name="5.1.2.4p7" href="#5.1.2.4p7"><small>7</small></a>
1687 All modifications to a particular atomic object M occur in some particular total order,
1688 called the modification order of M. If A and B are modifications of an atomic object M,
1689 and A happens before B, then A shall precede B in the modification order of M, which is
1691 <p><a name="5.1.2.4p8" href="#5.1.2.4p8"><small>8</small></a>
1692 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1694 <p><a name="5.1.2.4p9" href="#5.1.2.4p9"><small>9</small></a>
1695 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1696 combined into a single total order for all objects. In general this will be impossible since different threads
1697 may observe modifications to different variables in inconsistent orders.
1699 <p><a name="5.1.2.4p10" href="#5.1.2.4p10"><small>10</small></a>
1700 A release sequence headed by a release operation A on an atomic object M is a maximal
1701 contiguous sub-sequence of side effects in the modification order of M, where the first
1702 operation is A and every subsequent operation either is performed by the same thread that
1703 performed the release or is an atomic read-modify-write operation.
1704 <p><a name="5.1.2.4p11" href="#5.1.2.4p11"><small>11</small></a>
1705 Certain library calls synchronize with other library calls performed by another thread. In
1706 particular, an atomic operation A that performs a release operation on an object M
1707 synchronizes with an atomic operation B that performs an acquire operation on M and
1708 reads a value written by any side effect in the release sequence headed by A.
1709 <p><a name="5.1.2.4p12" href="#5.1.2.4p12"><small>12</small></a>
1710 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1711 described below. Such a requirement would sometimes interfere with efficient implementation.
1713 <p><a name="5.1.2.4p13" href="#5.1.2.4p13"><small>13</small></a>
1714 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1715 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1716 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1718 <p><a name="5.1.2.4p14" href="#5.1.2.4p14"><small>14</small></a>
1719 An evaluation A carries a dependency <sup><a href="#note15"><b>15)</b></a></sup> to an evaluation B if:
1724 <li> the value of A is used as an operand of B, unless:
1726 <li> B is an invocation of the kill_dependency macro,
1728 <li> A is the left operand of a && or || operator,
1730 <li> A is the left operand of a ? : operator, or
1732 <li> A is the left operand of a , operator;
1735 <li> A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1736 is sequenced before B, or
1737 <li> for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1739 <p><a name="5.1.2.4p15" href="#5.1.2.4p15"><small>15</small></a>
1740 An evaluation A is dependency-ordered before<sup><a href="#note16"><b>16)</b></a></sup> an evaluation B if:
1742 <li> A performs a release operation on an atomic object M, and, in another thread, B
1743 performs a consume operation on M and reads a value written by any side effect in
1744 the release sequence headed by A, or
1745 <li> for some evaluation X, A is dependency-ordered before X and X carries a
1748 <p><a name="5.1.2.4p16" href="#5.1.2.4p16"><small>16</small></a>
1749 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1750 is dependency-ordered before B, or, for some evaluation X:
1752 <li> A synchronizes with X and X is sequenced before B,
1753 <li> A is sequenced before X and X inter-thread happens before B, or
1754 <li> A inter-thread happens before X and X inter-thread happens before B.
1756 <p><a name="5.1.2.4p17" href="#5.1.2.4p17"><small>17</small></a>
1757 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1758 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1759 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1760 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1761 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1762 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1763 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1764 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1765 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1766 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1767 consisting entirely of ''sequenced before''.
1769 <p><a name="5.1.2.4p18" href="#5.1.2.4p18"><small>18</small></a>
1770 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1771 thread happens before B.
1776 <p><a name="5.1.2.4p19" href="#5.1.2.4p19"><small>19</small></a>
1777 A visible side effect A on an object M with respect to a value computation B of M
1778 satisfies the conditions:
1780 <li> A happens before B, and
1781 <li> there is no other side effect X to M such that A happens before X and X happens
1784 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1785 value stored by the visible side effect A.
1786 <p><a name="5.1.2.4p20" href="#5.1.2.4p20"><small>20</small></a>
1787 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1788 race and the behavior is undefined.
1790 <p><a name="5.1.2.4p21" href="#5.1.2.4p21"><small>21</small></a>
1791 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1792 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1793 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1796 <p><a name="5.1.2.4p22" href="#5.1.2.4p22"><small>22</small></a>
1797 The visible sequence of side effects on an atomic object M, with respect to a value
1798 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1799 modification order of M, where the first side effect is visible with respect to B, and for
1800 every subsequent side effect, it is not the case that B happens before it. The value of an
1801 atomic object M, as determined by evaluation B, shall be the value stored by some
1802 operation in the visible sequence of M with respect to B. Furthermore, if a value
1803 computation A of an atomic object M happens before a value computation B of M, and
1804 the value computed by A corresponds to the value stored by side effect X, then the value
1805 computed by B shall either equal the value computed by A, or be the value stored by side
1806 effect Y , where Y follows X in the modification order of M.
1807 <p><a name="5.1.2.4p23" href="#5.1.2.4p23"><small>23</small></a>
1808 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1809 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1810 provided by most hardware available to C atomic operations.
1812 <p><a name="5.1.2.4p24" href="#5.1.2.4p24"><small>24</small></a>
1813 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1814 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1815 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1816 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1817 constraints as imposed here.
1819 <p><a name="5.1.2.4p25" href="#5.1.2.4p25"><small>25</small></a>
1820 The execution of a program contains a data race if it contains two conflicting actions in
1821 different threads, at least one of which is not atomic, and neither happens before the
1822 other. Any such data race results in undefined behavior.
1823 <p><a name="5.1.2.4p26" href="#5.1.2.4p26"><small>26</small></a>
1824 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1825 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1826 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1827 with each value computation of an object being the last value stored in that interleaving. This is normally
1828 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1829 race-free programs cannot observe most program transformations that do not change single-threaded
1830 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1831 any program that behaves differently as a result must contain undefined behavior.
1833 <p><a name="5.1.2.4p27" href="#5.1.2.4p27"><small>27</small></a>
1834 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1835 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1836 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1837 execution would not have encountered a data race. This includes implementations of data member
1838 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1839 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1840 "visible sequence" rules.
1842 <p><a name="5.1.2.4p28" href="#5.1.2.4p28"><small>28</small></a>
1843 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1844 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1845 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1846 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1847 is not tolerant of races or provides hardware race detection.
1851 <p><small><a name="note14" href="#note14">14)</a> The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
1852 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1855 <p><small><a name="note15" href="#note15">15)</a> The ''carries a dependency'' relation is a subset of the ''sequenced before'' relation, and is similarly
1856 strictly intra-thread.
1858 <p><small><a name="note16" href="#note16">16)</a> The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
1859 release/consume in place of release/acquire.
1862 <p><small><a href="#Contents">Contents</a></small>
1863 <h3><a name="5.2" href="#5.2">5.2 Environmental considerations</a></h3>
1865 <p><small><a href="#Contents">Contents</a></small>
1866 <h4><a name="5.2.1" href="#5.2.1">5.2.1 Character sets</a></h4>
1867 <p><a name="5.2.1p1" href="#5.2.1p1"><small>1</small></a>
1868 Two sets of characters and their associated collating sequences shall be defined: the set in
1869 which source files are written (the source character set), and the set interpreted in the
1870 execution environment (the execution character set). Each set is further divided into a
1871 basic character set, whose contents are given by this subclause, and a set of zero or more
1872 locale-specific members (which are not members of the basic character set) called
1873 extended characters. The combined set is also called the extended character set. The
1874 values of the members of the execution character set are implementation-defined.
1875 <p><a name="5.2.1p2" href="#5.2.1p2"><small>2</small></a>
1876 In a character constant or string literal, members of the execution character set shall be
1877 represented by corresponding members of the source character set or by escape
1878 sequences consisting of the backslash \ followed by one or more characters. A byte with
1879 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1880 is used to terminate a character string.
1881 <p><a name="5.2.1p3" href="#5.2.1p3"><small>3</small></a>
1882 Both the basic source and basic execution character sets shall have the following
1883 members: the 26 uppercase letters of the Latin alphabet
1885 A B C D E F G H I J K L M
1886 N O P Q R S T U V W X Y Z
1888 the 26 lowercase letters of the Latin alphabet
1890 a b c d e f g h i j k l m
1891 n o p q r s t u v w x y z
1893 the 10 decimal digits
1897 the following 29 graphic characters
1899 ! " # % & ' ( ) * + , - . / :
1900 ; < = > ? [ \ ] ^ _ { | } ~
1902 the space character, and control characters representing horizontal tab, vertical tab, and
1903 form feed. The representation of each member of the source and execution basic
1904 character sets shall fit in a byte. In both the source and execution basic character sets, the
1905 value of each character after 0 in the above list of decimal digits shall be one greater than
1906 the value of the previous. In source files, there shall be some way of indicating the end of
1907 each line of text; this International Standard treats such an end-of-line indicator as if it
1908 were a single new-line character. In the basic execution character set, there shall be
1909 control characters representing alert, backspace, carriage return, and new line. If any
1910 other characters are encountered in a source file (except in an identifier, a character
1911 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1913 converted to a token), the behavior is undefined.
1914 <p><a name="5.2.1p4" href="#5.2.1p4"><small>4</small></a>
1915 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1916 Standard the term does not include other characters that are letters in other alphabets.
1917 <p><a name="5.2.1p5" href="#5.2.1p5"><small>5</small></a>
1918 The universal character name construct provides a way to name other characters.
1919 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), character constants (<a href="#6.4.4.4">6.4.4.4</a>),
1920 preprocessing directives (<a href="#6.10">6.10</a>), string literals (<a href="#6.4.5">6.4.5</a>), comments (<a href="#6.4.9">6.4.9</a>), string (<a href="#7.1.1">7.1.1</a>).
1922 <p><small><a href="#Contents">Contents</a></small>
1923 <h5><a name="5.2.1.1" href="#5.2.1.1">5.2.1.1 Trigraph sequences</a></h5>
1924 <p><a name="5.2.1.1p1" href="#5.2.1.1p1"><small>1</small></a>
1925 Before any other processing takes place, each occurrence of one of the following
1926 sequences of three characters (called trigraph sequences<sup><a href="#note17"><b>17)</b></a></sup>) is replaced with the
1927 corresponding single character.
1930 ??( [ ??' ^ ??> }
1931 ??/ \ ??< { ??- ~
1933 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1934 above is not changed.
1935 <p><a name="5.2.1.1p2" href="#5.2.1.1p2"><small>2</small></a>
1938 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1942 #define arraycheck(a, b) a[b] || b[a]
1945 <p><a name="5.2.1.1p3" href="#5.2.1.1p3"><small>3</small></a>
1946 EXAMPLE 2 The following source line
1950 becomes (after replacement of the trigraph sequence ??/)
1957 <p><small><a name="note17" href="#note17">17)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1958 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1961 <p><small><a href="#Contents">Contents</a></small>
1962 <h5><a name="5.2.1.2" href="#5.2.1.2">5.2.1.2 Multibyte characters</a></h5>
1963 <p><a name="5.2.1.2p1" href="#5.2.1.2p1"><small>1</small></a>
1964 The source character set may contain multibyte characters, used to represent members of
1965 the extended character set. The execution character set may also contain multibyte
1966 characters, which need not have the same encoding as for the source character set. For
1967 both character sets, the following shall hold:
1969 <li> The basic character set shall be present and each character shall be encoded as a
1971 <li> The presence, meaning, and representation of any additional members is locale-
1975 <li> A multibyte character set may have a state-dependent encoding, wherein each
1976 sequence of multibyte characters begins in an initial shift state and enters other
1977 locale-specific shift states when specific multibyte characters are encountered in the
1978 sequence. While in the initial shift state, all single-byte characters retain their usual
1979 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1980 in the sequence is a function of the current shift state.
1981 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1982 state. Such a byte shall not occur as part of any other multibyte character.
1984 <p><a name="5.2.1.2p2" href="#5.2.1.2p2"><small>2</small></a>
1985 For source files, the following shall hold:
1987 <li> An identifier, comment, string literal, character constant, or header name shall begin
1988 and end in the initial shift state.
1989 <li> An identifier, comment, string literal, character constant, or header name shall consist
1990 of a sequence of valid multibyte characters.
1993 <p><small><a href="#Contents">Contents</a></small>
1994 <h4><a name="5.2.2" href="#5.2.2">5.2.2 Character display semantics</a></h4>
1995 <p><a name="5.2.2p1" href="#5.2.2p1"><small>1</small></a>
1996 The active position is that location on a display device where the next character output by
1997 the fputc function would appear. The intent of writing a printing character (as defined
1998 by the isprint function) to a display device is to display a graphic representation of
1999 that character at the active position and then advance the active position to the next
2000 position on the current line. The direction of writing is locale-specific. If the active
2001 position is at the final position of a line (if there is one), the behavior of the display device
2003 <p><a name="5.2.2p2" href="#5.2.2p2"><small>2</small></a>
2004 Alphabetic escape sequences representing nongraphic characters in the execution
2005 character set are intended to produce actions on display devices as follows:
2006 \a (alert) Produces an audible or visible alert without changing the active position.
2007 \b (backspace) Moves the active position to the previous position on the current line. If
2009 the active position is at the initial position of a line, the behavior of the display
2010 device is unspecified.
2012 \f ( form feed) Moves the active position to the initial position at the start of the next
2016 \n (new line) Moves the active position to the initial position of the next line.
2017 \r (carriage return) Moves the active position to the initial position of the current line.
2018 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
2020 on the current line. If the active position is at or past the last defined horizontal
2021 tabulation position, the behavior of the display device is unspecified.
2023 \v (vertical tab) Moves the active position to the initial position of the next vertical
2026 tabulation position. If the active position is at or past the last defined vertical
2027 tabulation position, the behavior of the display device is unspecified.
2029 <p><a name="5.2.2p3" href="#5.2.2p3"><small>3</small></a>
2030 Each of these escape sequences shall produce a unique implementation-defined value
2031 which can be stored in a single char object. The external representations in a text file
2032 need not be identical to the internal representations, and are outside the scope of this
2033 International Standard.
2034 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.21.7.3">7.21.7.3</a>).
2036 <p><small><a href="#Contents">Contents</a></small>
2037 <h4><a name="5.2.3" href="#5.2.3">5.2.3 Signals and interrupts</a></h4>
2038 <p><a name="5.2.3p1" href="#5.2.3p1"><small>1</small></a>
2039 Functions shall be implemented such that they may be interrupted at any time by a signal,
2040 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
2041 invocations' control flow (after the interruption), function return values, or objects with
2042 automatic storage duration. All such objects shall be maintained outside the function
2043 image (the instructions that compose the executable representation of a function) on a
2044 per-invocation basis.
2046 <p><small><a href="#Contents">Contents</a></small>
2047 <h4><a name="5.2.4" href="#5.2.4">5.2.4 Environmental limits</a></h4>
2048 <p><a name="5.2.4p1" href="#5.2.4p1"><small>1</small></a>
2049 Both the translation and execution environments constrain the implementation of
2050 language translators and libraries. The following summarizes the language-related
2051 environmental limits on a conforming implementation; the library-related limits are
2052 discussed in clause 7.
2054 <p><small><a href="#Contents">Contents</a></small>
2055 <h5><a name="5.2.4.1" href="#5.2.4.1">5.2.4.1 Translation limits</a></h5>
2056 <p><a name="5.2.4.1p1" href="#5.2.4.1p1"><small>1</small></a>
2057 The implementation shall be able to translate and execute at least one program that
2058 contains at least one instance of every one of the following limits:<sup><a href="#note18"><b>18)</b></a></sup>
2060 <li> 127 nesting levels of blocks
2061 <li> 63 nesting levels of conditional inclusion
2062 <li> 12 pointer, array, and function declarators (in any combinations) modifying an
2063 arithmetic, structure, union, or void type in a declaration
2064 <li> 63 nesting levels of parenthesized declarators within a full declarator
2065 <li> 63 nesting levels of parenthesized expressions within a full expression
2066 <li> 63 significant initial characters in an internal identifier or a macro name (each
2067 universal character name or extended source character is considered a single
2069 <li> 31 significant initial characters in an external identifier (each universal character name
2070 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
2075 universal character name specifying a short identifier of 00010000 or more is
2076 considered 10 characters, and each extended source character is considered the same
2077 number of characters as the corresponding universal character name, if any)<sup><a href="#note19"><b>19)</b></a></sup>
2079 <li> 4095 external identifiers in one translation unit
2080 <li> 511 identifiers with block scope declared in one block
2081 <li> 4095 macro identifiers simultaneously defined in one preprocessing translation unit
2082 <li> 127 parameters in one function definition
2083 <li> 127 arguments in one function call
2084 <li> 127 parameters in one macro definition
2085 <li> 127 arguments in one macro invocation
2086 <li> 4095 characters in a logical source line
2087 <li> 4095 characters in a string literal (after concatenation)
2088 <li> 65535 bytes in an object (in a hosted environment only)
2089 <li> 15 nesting levels for #included files
2090 <li> 1023 case labels for a switch statement (excluding those for any nested switch
2092 <li> 1023 members in a single structure or union
2093 <li> 1023 enumeration constants in a single enumeration
2094 <li> 63 levels of nested structure or union definitions in a single struct-declaration-list
2098 <p><small><a name="note18" href="#note18">18)</a> Implementations should avoid imposing fixed translation limits whenever possible.
2100 <p><small><a name="note19" href="#note19">19)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
2103 <p><small><a href="#Contents">Contents</a></small>
2104 <h5><a name="5.2.4.2" href="#5.2.4.2">5.2.4.2 Numerical limits</a></h5>
2105 <p><a name="5.2.4.2p1" href="#5.2.4.2p1"><small>1</small></a>
2106 An implementation is required to document all the limits specified in this subclause,
2107 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
2108 specified in <a href="#7.20"><stdint.h></a>.
2109 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
2111 <p><small><a href="#Contents">Contents</a></small>
2112 <h5><a name="5.2.4.2.1" href="#5.2.4.2.1">5.2.4.2.1 Sizes of integer types <limits.h></a></h5>
2113 <p><a name="5.2.4.2.1p1" href="#5.2.4.2.1p1"><small>1</small></a>
2114 The values given below shall be replaced by constant expressions suitable for use in #if
2115 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
2116 following shall be replaced by expressions that have the same type as would an
2117 expression that is an object of the corresponding type converted according to the integer
2118 promotions. Their implementation-defined values shall be equal or greater in magnitude
2122 (absolute value) to those shown, with the same sign.
2124 <li> number of bits for smallest object that is not a bit-field (byte)
2126 <li> minimum value for an object of type signed char
2127 SCHAR_MIN -127 // -(27 - 1)
2128 <li> maximum value for an object of type signed char
2129 SCHAR_MAX +127 // 27 - 1
2130 <li> maximum value for an object of type unsigned char
2131 UCHAR_MAX 255 // 28 - 1
2132 <li> minimum value for an object of type char
2134 <li> maximum value for an object of type char
2136 <li> maximum number of bytes in a multibyte character, for any supported locale
2138 <li> minimum value for an object of type short int
2139 SHRT_MIN -32767 // -(215 - 1)
2140 <li> maximum value for an object of type short int
2141 SHRT_MAX +32767 // 215 - 1
2142 <li> maximum value for an object of type unsigned short int
2143 USHRT_MAX 65535 // 216 - 1
2144 <li> minimum value for an object of type int
2145 INT_MIN -32767 // -(215 - 1)
2146 <li> maximum value for an object of type int
2147 INT_MAX +32767 // 215 - 1
2148 <li> maximum value for an object of type unsigned int
2149 UINT_MAX 65535 // 216 - 1
2150 <li> minimum value for an object of type long int
2151 LONG_MIN -2147483647 // -(231 - 1)
2152 <li> maximum value for an object of type long int
2153 LONG_MAX +2147483647 // 231 - 1
2154 <li> maximum value for an object of type unsigned long int
2155 ULONG_MAX 4294967295 // 232 - 1
2157 <li> minimum value for an object of type long long int
2158 LLONG_MIN -9223372036854775807 // -(263 - 1)
2159 <li> maximum value for an object of type long long int
2160 LLONG_MAX +9223372036854775807 // 263 - 1
2161 <li> maximum value for an object of type unsigned long long int
2162 ULLONG_MAX 18446744073709551615 // 264 - 1
2164 <p><a name="5.2.4.2.1p2" href="#5.2.4.2.1p2"><small>2</small></a>
2165 If the value of an object of type char is treated as a signed integer when used in an
2166 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
2167 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
2168 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
2169 UCHAR_MAX.<sup><a href="#note20"><b>20)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
2170 <p><b> Forward references</b>: representations of types (<a href="#6.2.6">6.2.6</a>), conditional inclusion (<a href="#6.10.1">6.10.1</a>).
2173 <p><small><a name="note20" href="#note20">20)</a> See <a href="#6.2.5">6.2.5</a>.
2176 <p><small><a href="#Contents">Contents</a></small>
2177 <h5><a name="5.2.4.2.2" href="#5.2.4.2.2">5.2.4.2.2 Characteristics of floating types <float.h></a></h5>
2178 <p><a name="5.2.4.2.2p1" href="#5.2.4.2.2p1"><small>1</small></a>
2179 The characteristics of floating types are defined in terms of a model that describes a
2180 representation of floating-point numbers and values that provide information about an
2181 implementation's floating-point arithmetic.<sup><a href="#note21"><b>21)</b></a></sup> The following parameters are used to
2182 define the model for each floating-point type:
2185 b base or radix of exponent representation (an integer > 1)
2186 e exponent (an integer between a minimum emin and a maximum emax )
2187 p precision (the number of base-b digits in the significand)
2188 fk nonnegative integers less than b (the significand digits)
2190 <p><a name="5.2.4.2.2p2" href="#5.2.4.2.2p2"><small>2</small></a>
2191 A floating-point number (x) is defined by the following model:
2194 x = sb e (Sum) f k b-k ,
2196 emin <= e <= emax
2199 <p><a name="5.2.4.2.2p3" href="#5.2.4.2.2p3"><small>3</small></a>
2200 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
2201 able to contain other kinds of floating-point numbers, such as subnormal floating-point
2202 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
2203 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
2204 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
2205 through almost every arithmetic operation without raising a floating-point exception; a
2206 signaling NaN generally raises a floating-point exception when occurring as an
2210 arithmetic operand.<sup><a href="#note22"><b>22)</b></a></sup>
2211 <p><a name="5.2.4.2.2p4" href="#5.2.4.2.2p4"><small>4</small></a>
2212 An implementation may give zero and values that are not floating-point numbers (such as
2213 infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
2214 unsigned, any requirement in this International Standard to retrieve the sign shall produce
2215 an unspecified sign, and any requirement to set the sign shall be ignored.
2216 <p><a name="5.2.4.2.2p5" href="#5.2.4.2.2p5"><small>5</small></a>
2217 The minimum range of representable values for a floating type is the most negative finite
2218 floating-point number representable in that type through the most positive finite floating-
2219 point number representable in that type. In addition, if negative infinity is representable
2220 in a type, the range of that type is extended to all negative real numbers; likewise, if
2221 positive infinity is representable in a type, the range of that type is extended to all positive
2223 <p><a name="5.2.4.2.2p6" href="#5.2.4.2.2p6"><small>6</small></a>
2224 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
2225 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
2226 defined, as is the accuracy of the conversion between floating-point internal
2227 representations and string representations performed by the library functions in
2228 <a href="#7.21"><stdio.h></a>, <a href="#7.22"><stdlib.h></a>, and <a href="#7.29"><wchar.h></a>. The implementation may state that the
2229 accuracy is unknown.
2230 <p><a name="5.2.4.2.2p7" href="#5.2.4.2.2p7"><small>7</small></a>
2231 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
2232 expressions suitable for use in #if preprocessing directives; all floating values shall be
2233 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
2234 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
2235 point model representation is provided for all values except FLT_EVAL_METHOD and
2237 <p><a name="5.2.4.2.2p8" href="#5.2.4.2.2p8"><small>8</small></a>
2238 The rounding mode for floating-point addition is characterized by the implementation-
2239 defined value of FLT_ROUNDS:<sup><a href="#note23"><b>23)</b></a></sup>
2244 2 toward positive infinity
2245 3 toward negative infinity
2247 All other values for FLT_ROUNDS characterize implementation-defined rounding
2252 <p><a name="5.2.4.2.2p9" href="#5.2.4.2.2p9"><small>9</small></a>
2253 Except for assignment and cast (which remove all extra range and precision), the values
2254 yielded by operators with floating operands and values subject to the usual arithmetic
2255 conversions and of floating constants are evaluated to a format whose range and precision
2256 may be greater than required by the type. The use of evaluation formats is characterized
2257 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note24"><b>24)</b></a></sup>
2260 0 evaluate all operations and constants just to the range and precision of the
2262 1 evaluate operations and constants of type float and double to the
2263 range and precision of the double type, evaluate long double
2264 operations and constants to the range and precision of the long double
2266 2 evaluate all operations and constants to the range and precision of the
2269 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
2271 <p><a name="5.2.4.2.2p10" href="#5.2.4.2.2p10"><small>10</small></a>
2272 The presence or absence of subnormal numbers is characterized by the implementation-
2273 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
2276 -1 indeterminable<sup><a href="#note25"><b>25)</b></a></sup>
2277 0 absent<sup><a href="#note26"><b>26)</b></a></sup> (type does not support subnormal numbers)
2278 1 present (type does support subnormal numbers)
2280 <p><a name="5.2.4.2.2p11" href="#5.2.4.2.2p11"><small>11</small></a>
2281 The values given in the following list shall be replaced by constant expressions with
2282 implementation-defined values that are greater or equal in magnitude (absolute value) to
2283 those shown, with the same sign:
2285 <li> radix of exponent representation, b
2292 <li> number of base-FLT_RADIX digits in the floating-point significand, p
2296 <li> number of decimal digits, n, such that any floating-point number with p radix b digits
2297 can be rounded to a floating-point number with n decimal digits and back again
2298 without change to the value,
2300 { p log10 b if b is a power of 10
2302 { [^1 + p log10 b^] otherwise
2307 <li> number of decimal digits, n, such that any floating-point number in the widest
2308 supported floating type with pmax radix b digits can be rounded to a floating-point
2309 number with n decimal digits and back again without change to the value,
2311 { pmax log10 b if b is a power of 10
2313 { [^1 + pmax log10 b^] otherwise
2316 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
2317 can be rounded into a floating-point number with p radix b digits and back again
2318 without change to the q decimal digits,
2320 { p log10 b if b is a power of 10
2322 { [_( p - 1) log10 b_] otherwise
2327 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
2328 a normalized floating-point number, emin
2333 <li> minimum negative integer such that 10 raised to that power is in the range of
2334 normalized floating-point numbers, [^log10 b emin -1 ^]
2341 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
2342 representable finite floating-point number, emax
2348 <li> maximum integer such that 10 raised to that power is in the range of representable
2349 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
2356 <p><a name="5.2.4.2.2p12" href="#5.2.4.2.2p12"><small>12</small></a>
2357 The values given in the following list shall be replaced by constant expressions with
2358 implementation-defined values that are greater than or equal to those shown:
2360 <li> maximum representable finite floating-point number, (1 - b- p )b emax
2367 <p><a name="5.2.4.2.2p13" href="#5.2.4.2.2p13"><small>13</small></a>
2368 The values given in the following list shall be replaced by constant expressions with
2369 implementation-defined (positive) values that are less than or equal to those shown:
2371 <li> the difference between 1 and the least value greater than 1 that is representable in the
2372 given floating point type, b1- p
2378 <li> minimum normalized positive floating-point number, b emin -1
2385 <li> minimum positive floating-point number<sup><a href="#note27"><b>27)</b></a></sup>
2390 <p><b>Recommended practice</b>
2391 <p><a name="5.2.4.2.2p14" href="#5.2.4.2.2p14"><small>14</small></a>
2392 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
2393 should be the identity function.
2394 <p><a name="5.2.4.2.2p15" href="#5.2.4.2.2p15"><small>15</small></a>
2395 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
2396 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
2400 x = s16e (Sum) f k 16-k ,
2402 -31 <= e <= +32
2408 FLT_EPSILON 9.53674316E-07F
2412 FLT_MIN 2.93873588E-39F
2415 FLT_MAX 3.40282347E+38F
2419 <p><a name="5.2.4.2.2p16" href="#5.2.4.2.2p16"><small>16</small></a>
2420 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
2421 single-precision and double-precision numbers in IEC 60559,<sup><a href="#note28"><b>28)</b></a></sup> and the appropriate values in a
2422 <a href="#7.7"><float.h></a> header for types float and double:
2425 x f = s2e (Sum) f k 2-k ,
2427 -125 <= e <= +128
2432 x d = s2e (Sum) f k 2-k ,
2434 -1021 <= e <= +1024
2441 FLT_EPSILON 1.19209290E-07F // decimal constant
2442 FLT_EPSILON 0X1P-23F // hex constant
2451 FLT_MIN 1.17549435E-38F // decimal constant
2452 FLT_MIN 0X1P-126F // hex constant
2453 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
2454 FLT_TRUE_MIN 0X1P-149F // hex constant
2458 FLT_MAX 3.40282347E+38F // decimal constant
2459 FLT_MAX 0X1.fffffeP127F // hex constant
2462 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
2463 DBL_EPSILON 0X1P-52 // hex constant
2467 DBL_MIN 2.2250738585072014E-308 // decimal constant
2468 DBL_MIN 0X1P-1022 // hex constant
2469 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
2470 DBL_TRUE_MIN 0X1P-1074 // hex constant
2474 DBL_MAX 1.7976931348623157E+308 // decimal constant
2475 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
2478 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
2479 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
2480 precision), then DECIMAL_DIG would be 21.
2482 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
2483 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.29"><wchar.h></a>
2484 (<a href="#7.29">7.29</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.22"><stdlib.h></a>
2485 (<a href="#7.22">7.22</a>), input/output <a href="#7.21"><stdio.h></a> (<a href="#7.21">7.21</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
2489 <p><small><a name="note21" href="#note21">21)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
2490 does not require the floating-point arithmetic of the implementation to be identical.
2492 <p><small><a name="note22" href="#note22">22)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
2493 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
2496 <p><small><a name="note23" href="#note23">23)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
2497 the function fesetround in <a href="#7.6"><fenv.h></a>.
2499 <p><small><a name="note24" href="#note24">24)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
2500 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
2501 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
2504 <p><small><a name="note25" href="#note25">25)</a> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
2505 subnormal representations as zero, nor as nonzero.
2507 <p><small><a name="note26" href="#note26">26)</a> Characterization as absent is intended if no floating-point operations produce subnormal results from
2508 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
2510 <p><small><a name="note27" href="#note27">27)</a> If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a
2511 positive number no greater than the minimum normalized positive number for the type.
2513 <p><small><a name="note28" href="#note28">28)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
2514 limits are one less than shown here.
2517 <p><small><a href="#Contents">Contents</a></small>
2518 <h2><a name="6" href="#6">6. Language</a></h2>
2520 <p><small><a href="#Contents">Contents</a></small>
2521 <h3><a name="6.1" href="#6.1">6.1 Notation</a></h3>
2522 <p><a name="6.1p1" href="#6.1p1"><small>1</small></a>
2523 In the syntax notation used in this clause, syntactic categories (nonterminals) are
2524 indicated by italic type, and literal words and character set members (terminals) by bold
2525 type. A colon (:) following a nonterminal introduces its definition. Alternative
2526 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
2527 optional symbol is indicated by the subscript ''opt'', so that
2529 { expression<sub>opt</sub> }
2531 indicates an optional expression enclosed in braces.
2532 <p><a name="6.1p2" href="#6.1p2"><small>2</small></a>
2533 When syntactic categories are referred to in the main text, they are not italicized and
2534 words are separated by spaces instead of hyphens.
2535 <p><a name="6.1p3" href="#6.1p3"><small>3</small></a>
2536 A summary of the language syntax is given in <a href="#A">annex A</a>.
2538 <p><small><a href="#Contents">Contents</a></small>
2539 <h3><a name="6.2" href="#6.2">6.2 Concepts</a></h3>
2541 <p><small><a href="#Contents">Contents</a></small>
2542 <h4><a name="6.2.1" href="#6.2.1">6.2.1 Scopes of identifiers</a></h4>
2543 <p><a name="6.2.1p1" href="#6.2.1p1"><small>1</small></a>
2544 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2545 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2546 same identifier can denote different entities at different points in the program. A member
2547 of an enumeration is called an enumeration constant. Macro names and macro
2548 parameters are not considered further here, because prior to the semantic phase of
2549 program translation any occurrences of macro names in the source file are replaced by the
2550 preprocessing token sequences that constitute their macro definitions.
2551 <p><a name="6.2.1p2" href="#6.2.1p2"><small>2</small></a>
2552 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2553 used) only within a region of program text called its scope. Different entities designated
2554 by the same identifier either have different scopes, or are in different name spaces. There
2555 are four kinds of scopes: function, file, block, and function prototype. (A function
2556 prototype is a declaration of a function that declares the types of its parameters.)
2557 <p><a name="6.2.1p3" href="#6.2.1p3"><small>3</small></a>
2558 A label name is the only kind of identifier that has function scope. It can be used (in a
2559 goto statement) anywhere in the function in which it appears, and is declared implicitly
2560 by its syntactic appearance (followed by a : and a statement).
2561 <p><a name="6.2.1p4" href="#6.2.1p4"><small>4</small></a>
2562 Every other identifier has scope determined by the placement of its declaration (in a
2563 declarator or type specifier). If the declarator or type specifier that declares the identifier
2564 appears outside of any block or list of parameters, the identifier has file scope, which
2565 terminates at the end of the translation unit. If the declarator or type specifier that
2566 declares the identifier appears inside a block or within the list of parameter declarations in
2567 a function definition, the identifier has block scope, which terminates at the end of the
2568 associated block. If the declarator or type specifier that declares the identifier appears
2570 within the list of parameter declarations in a function prototype (not part of a function
2571 definition), the identifier has function prototype scope, which terminates at the end of the
2572 function declarator. If an identifier designates two different entities in the same name
2573 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2574 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2575 identifier designates the entity declared in the inner scope; the entity declared in the outer
2576 scope is hidden (and not visible) within the inner scope.
2577 <p><a name="6.2.1p5" href="#6.2.1p5"><small>5</small></a>
2578 Unless explicitly stated otherwise, where this International Standard uses the term
2579 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2580 entity in the relevant name space whose declaration is visible at the point the identifier
2582 <p><a name="6.2.1p6" href="#6.2.1p6"><small>6</small></a>
2583 Two identifiers have the same scope if and only if their scopes terminate at the same
2585 <p><a name="6.2.1p7" href="#6.2.1p7"><small>7</small></a>
2586 Structure, union, and enumeration tags have scope that begins just after the appearance of
2587 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2588 begins just after the appearance of its defining enumerator in an enumerator list. Any
2589 other identifier has scope that begins just after the completion of its declarator.
2590 <p><a name="6.2.1p8" href="#6.2.1p8"><small>8</small></a>
2591 As a special case, a type name (which is not a declaration of an identifier) is considered to
2592 have a scope that begins just after the place within the type name where the omitted
2593 identifier would appear were it not omitted.
2594 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), function definitions
2595 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>),
2596 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
2598 <p><small><a href="#Contents">Contents</a></small>
2599 <h4><a name="6.2.2" href="#6.2.2">6.2.2 Linkages of identifiers</a></h4>
2600 <p><a name="6.2.2p1" href="#6.2.2p1"><small>1</small></a>
2601 An identifier declared in different scopes or in the same scope more than once can be
2602 made to refer to the same object or function by a process called linkage.<sup><a href="#note29"><b>29)</b></a></sup> There are
2603 three kinds of linkage: external, internal, and none.
2604 <p><a name="6.2.2p2" href="#6.2.2p2"><small>2</small></a>
2605 In the set of translation units and libraries that constitutes an entire program, each
2606 declaration of a particular identifier with external linkage denotes the same object or
2607 function. Within one translation unit, each declaration of an identifier with internal
2608 linkage denotes the same object or function. Each declaration of an identifier with no
2609 linkage denotes a unique entity.
2610 <p><a name="6.2.2p3" href="#6.2.2p3"><small>3</small></a>
2611 If the declaration of a file scope identifier for an object or a function contains the storage-
2612 class specifier static, the identifier has internal linkage.<sup><a href="#note30"><b>30)</b></a></sup>
2617 <p><a name="6.2.2p4" href="#6.2.2p4"><small>4</small></a>
2618 For an identifier declared with the storage-class specifier extern in a scope in which a
2619 prior declaration of that identifier is visible,<sup><a href="#note31"><b>31)</b></a></sup> if the prior declaration specifies internal or
2620 external linkage, the linkage of the identifier at the later declaration is the same as the
2621 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2622 declaration specifies no linkage, then the identifier has external linkage.
2623 <p><a name="6.2.2p5" href="#6.2.2p5"><small>5</small></a>
2624 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2625 is determined exactly as if it were declared with the storage-class specifier extern. If
2626 the declaration of an identifier for an object has file scope and no storage-class specifier,
2627 its linkage is external.
2628 <p><a name="6.2.2p6" href="#6.2.2p6"><small>6</small></a>
2629 The following identifiers have no linkage: an identifier declared to be anything other than
2630 an object or a function; an identifier declared to be a function parameter; a block scope
2631 identifier for an object declared without the storage-class specifier extern.
2632 <p><a name="6.2.2p7" href="#6.2.2p7"><small>7</small></a>
2633 If, within a translation unit, the same identifier appears with both internal and external
2634 linkage, the behavior is undefined.
2635 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), external definitions (<a href="#6.9">6.9</a>),
2636 statements (<a href="#6.8">6.8</a>).
2639 <p><small><a name="note29" href="#note29">29)</a> There is no linkage between different identifiers.
2641 <p><small><a name="note30" href="#note30">30)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
2642 <a href="#6.7.1">6.7.1</a>.
2644 <p><small><a name="note31" href="#note31">31)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2647 <p><small><a href="#Contents">Contents</a></small>
2648 <h4><a name="6.2.3" href="#6.2.3">6.2.3 Name spaces of identifiers</a></h4>
2649 <p><a name="6.2.3p1" href="#6.2.3p1"><small>1</small></a>
2650 If more than one declaration of a particular identifier is visible at any point in a
2651 translation unit, the syntactic context disambiguates uses that refer to different entities.
2652 Thus, there are separate name spaces for various categories of identifiers, as follows:
2654 <li> label names (disambiguated by the syntax of the label declaration and use);
2655 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note32"><b>32)</b></a></sup>
2656 of the keywords struct, union, or enum);
2657 <li> the members of structures or unions; each structure or union has a separate name
2658 space for its members (disambiguated by the type of the expression used to access the
2659 member via the . or -> operator);
2660 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2661 enumeration constants).
2663 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), labeled statements (<a href="#6.8.1">6.8.1</a>),
2664 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>), tags
2665 (<a href="#6.7.2.3">6.7.2.3</a>), the goto statement (<a href="#6.8.6.1">6.8.6.1</a>).
2670 <p><small><a name="note32" href="#note32">32)</a> There is only one name space for tags even though three are possible.
2673 <p><small><a href="#Contents">Contents</a></small>
2674 <h4><a name="6.2.4" href="#6.2.4">6.2.4 Storage durations of objects</a></h4>
2675 <p><a name="6.2.4p1" href="#6.2.4p1"><small>1</small></a>
2676 An object has a storage duration that determines its lifetime. There are four storage
2677 durations: static, thread, automatic, and allocated. Allocated storage is described in
2678 <a href="#7.22.3">7.22.3</a>.
2679 <p><a name="6.2.4p2" href="#6.2.4p2"><small>2</small></a>
2680 The lifetime of an object is the portion of program execution during which storage is
2681 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note33"><b>33)</b></a></sup> and retains
2682 its last-stored value throughout its lifetime.<sup><a href="#note34"><b>34)</b></a></sup> If an object is referred to outside of its
2683 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2684 the object it points to (or just past) reaches the end of its lifetime.
2685 <p><a name="6.2.4p3" href="#6.2.4p3"><small>3</small></a>
2686 An object whose identifier is declared without the storage-class specifier
2687 _Thread_local, and either with external or internal linkage or with the storage-class
2688 specifier static, has static storage duration. Its lifetime is the entire execution of the
2689 program and its stored value is initialized only once, prior to program startup.
2690 <p><a name="6.2.4p4" href="#6.2.4p4"><small>4</small></a>
2691 An object whose identifier is declared with the storage-class specifier _Thread_local
2692 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2693 is created, and its stored value is initialized when the thread is started. There is a distinct
2694 object per thread, and use of the declared name in an expression refers to the object
2695 associated with the thread evaluating the expression. The result of attempting to
2696 indirectly access an object with thread storage duration from a thread other than the one
2697 with which the object is associated is implementation-defined.
2698 <p><a name="6.2.4p5" href="#6.2.4p5"><small>5</small></a>
2699 An object whose identifier is declared with no linkage and without the storage-class
2700 specifier static has automatic storage duration, as do some compound literals. The
2701 result of attempting to indirectly access an object with automatic storage duration from a
2702 thread other than the one with which the object is associated is implementation-defined.
2703 <p><a name="6.2.4p6" href="#6.2.4p6"><small>6</small></a>
2704 For such an object that does not have a variable length array type, its lifetime extends
2705 from entry into the block with which it is associated until execution of that block ends in
2706 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2707 execution of the current block.) If the block is entered recursively, a new instance of the
2708 object is created each time. The initial value of the object is indeterminate. If an
2709 initialization is specified for the object, it is performed each time the declaration or
2710 compound literal is reached in the execution of the block; otherwise, the value becomes
2711 indeterminate each time the declaration is reached.
2716 <p><a name="6.2.4p7" href="#6.2.4p7"><small>7</small></a>
2717 For such an object that does have a variable length array type, its lifetime extends from
2718 the declaration of the object until execution of the program leaves the scope of the
2719 declaration.<sup><a href="#note35"><b>35)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2720 each time. The initial value of the object is indeterminate.
2721 <p><a name="6.2.4p8" href="#6.2.4p8"><small>8</small></a>
2722 A non-lvalue expression with structure or union type, where the structure or union
2723 contains a member with array type (including, recursively, members of all contained
2724 structures and unions) refers to an object with automatic storage duration and temporary
2725 lifetime.<sup><a href="#note36"><b>36)</b></a></sup> Its lifetime begins when the expression is evaluated and its initial value is the
2726 value of the expression. Its lifetime ends when the evaluation of the containing full
2727 expression or full declarator ends. Any attempt to modify an object with temporary
2728 lifetime results in undefined behavior.
2729 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), compound literals (<a href="#6.5.2.5">6.5.2.5</a>), declarators
2730 (<a href="#6.7.6">6.7.6</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), initialization (<a href="#6.7.9">6.7.9</a>), statements (<a href="#6.8">6.8</a>).
2733 <p><small><a name="note33" href="#note33">33)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2734 times will compare equal. The address may be different during two different executions of the same
2737 <p><small><a name="note34" href="#note34">34)</a> In the case of a volatile object, the last store need not be explicit in the program.
2739 <p><small><a name="note35" href="#note35">35)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2740 embedded block prior to the declaration, leaves the scope of the declaration.
2742 <p><small><a name="note36" href="#note36">36)</a> The address of such an object is taken implicitly when an array member is accessed.
2745 <p><small><a href="#Contents">Contents</a></small>
2746 <h4><a name="6.2.5" href="#6.2.5">6.2.5 Types</a></h4>
2747 <p><a name="6.2.5p1" href="#6.2.5p1"><small>1</small></a>
2748 The meaning of a value stored in an object or returned by a function is determined by the
2749 type of the expression used to access it. (An identifier declared to be an object is the
2750 simplest such expression; the type is specified in the declaration of the identifier.) Types
2751 are partitioned into object types (types that describe objects) and function types (types
2752 that describe functions). At various points within a translation unit an object type may be
2753 incomplete (lacking sufficient information to determine the size of objects of that type) or
2754 complete (having sufficient information).<sup><a href="#note37"><b>37)</b></a></sup>
2755 <p><a name="6.2.5p2" href="#6.2.5p2"><small>2</small></a>
2756 An object declared as type _Bool is large enough to store the values 0 and 1.
2757 <p><a name="6.2.5p3" href="#6.2.5p3"><small>3</small></a>
2758 An object declared as type char is large enough to store any member of the basic
2759 execution character set. If a member of the basic execution character set is stored in a
2760 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2761 a char object, the resulting value is implementation-defined but shall be within the range
2762 of values that can be represented in that type.
2763 <p><a name="6.2.5p4" href="#6.2.5p4"><small>4</small></a>
2764 There are five standard signed integer types, designated as signed char, short
2765 int, int, long int, and long long int. (These and other types may be
2766 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2767 implementation-defined extended signed integer types.<sup><a href="#note38"><b>38)</b></a></sup> The standard and extended
2768 signed integer types are collectively called signed integer types.<sup><a href="#note39"><b>39)</b></a></sup>
2771 <p><a name="6.2.5p5" href="#6.2.5p5"><small>5</small></a>
2772 An object declared as type signed char occupies the same amount of storage as a
2773 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2774 architecture of the execution environment (large enough to contain any value in the range
2775 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2776 <p><a name="6.2.5p6" href="#6.2.5p6"><small>6</small></a>
2777 For each of the signed integer types, there is a corresponding (but different) unsigned
2778 integer type (designated with the keyword unsigned) that uses the same amount of
2779 storage (including sign information) and has the same alignment requirements. The type
2780 _Bool and the unsigned integer types that correspond to the standard signed integer
2781 types are the standard unsigned integer types. The unsigned integer types that
2782 correspond to the extended signed integer types are the extended unsigned integer types.
2783 The standard and extended unsigned integer types are collectively called unsigned integer
2784 types.<sup><a href="#note40"><b>40)</b></a></sup>
2785 <p><a name="6.2.5p7" href="#6.2.5p7"><small>7</small></a>
2786 The standard signed integer types and standard unsigned integer types are collectively
2787 called the standard integer types, the extended signed integer types and extended
2788 unsigned integer types are collectively called the extended integer types.
2789 <p><a name="6.2.5p8" href="#6.2.5p8"><small>8</small></a>
2790 For any two integer types with the same signedness and different integer conversion rank
2791 (see <a href="#6.3.1.1">6.3.1.1</a>), the range of values of the type with smaller integer conversion rank is a
2792 subrange of the values of the other type.
2793 <p><a name="6.2.5p9" href="#6.2.5p9"><small>9</small></a>
2794 The range of nonnegative values of a signed integer type is a subrange of the
2795 corresponding unsigned integer type, and the representation of the same value in each
2796 type is the same.<sup><a href="#note41"><b>41)</b></a></sup> A computation involving unsigned operands can never overflow,
2797 because a result that cannot be represented by the resulting unsigned integer type is
2798 reduced modulo the number that is one greater than the largest value that can be
2799 represented by the resulting type.
2800 <p><a name="6.2.5p10" href="#6.2.5p10"><small>10</small></a>
2801 There are three real floating types, designated as float, double, and long
2802 double.<sup><a href="#note42"><b>42)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2803 type double; the set of values of the type double is a subset of the set of values of the
2808 <p><a name="6.2.5p11" href="#6.2.5p11"><small>11</small></a>
2809 There are three complex types, designated as float _Complex, double
2810 _Complex, and long double _Complex.<sup><a href="#note43"><b>43)</b></a></sup> (Complex types are a conditional
2811 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2812 complex types are collectively called the floating types.
2813 <p><a name="6.2.5p12" href="#6.2.5p12"><small>12</small></a>
2814 For each floating type there is a corresponding real type, which is always a real floating
2815 type. For real floating types, it is the same type. For complex types, it is the type given
2816 by deleting the keyword _Complex from the type name.
2817 <p><a name="6.2.5p13" href="#6.2.5p13"><small>13</small></a>
2818 Each complex type has the same representation and alignment requirements as an array
2819 type containing exactly two elements of the corresponding real type; the first element is
2820 equal to the real part, and the second element to the imaginary part, of the complex
2822 <p><a name="6.2.5p14" href="#6.2.5p14"><small>14</small></a>
2823 The type char, the signed and unsigned integer types, and the floating types are
2824 collectively called the basic types. The basic types are complete object types. Even if the
2825 implementation defines two or more basic types to have the same representation, they are
2826 nevertheless different types.<sup><a href="#note44"><b>44)</b></a></sup>
2827 <p><a name="6.2.5p15" href="#6.2.5p15"><small>15</small></a>
2828 The three types char, signed char, and unsigned char are collectively called
2829 the character types. The implementation shall define char to have the same range,
2830 representation, and behavior as either signed char or unsigned char.<sup><a href="#note45"><b>45)</b></a></sup>
2831 <p><a name="6.2.5p16" href="#6.2.5p16"><small>16</small></a>
2832 An enumeration comprises a set of named integer constant values. Each distinct
2833 enumeration constitutes a different enumerated type.
2834 <p><a name="6.2.5p17" href="#6.2.5p17"><small>17</small></a>
2835 The type char, the signed and unsigned integer types, and the enumerated types are
2836 collectively called integer types. The integer and real floating types are collectively called
2838 <p><a name="6.2.5p18" href="#6.2.5p18"><small>18</small></a>
2839 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2840 belongs to one type domain: the real type domain comprises the real types, the complex
2841 type domain comprises the complex types.
2842 <p><a name="6.2.5p19" href="#6.2.5p19"><small>19</small></a>
2843 The void type comprises an empty set of values; it is an incomplete object type that
2844 cannot be completed.
2849 <p><a name="6.2.5p20" href="#6.2.5p20"><small>20</small></a>
2850 Any number of derived types can be constructed from the object and function types, as
2853 <li> An array type describes a contiguously allocated nonempty set of objects with a
2854 particular member object type, called the element type. The element type shall be
2855 complete whenever the array type is specified. Array types are characterized by their
2856 element type and by the number of elements in the array. An array type is said to be
2857 derived from its element type, and if its element type is T , the array type is sometimes
2858 called ''array of T ''. The construction of an array type from an element type is called
2859 ''array type derivation''.
2860 <li> A structure type describes a sequentially allocated nonempty set of member objects
2861 (and, in certain circumstances, an incomplete array), each of which has an optionally
2862 specified name and possibly distinct type.
2863 <li> A union type describes an overlapping nonempty set of member objects, each of
2864 which has an optionally specified name and possibly distinct type.
2865 <li> A function type describes a function with specified return type. A function type is
2866 characterized by its return type and the number and types of its parameters. A
2867 function type is said to be derived from its return type, and if its return type is T , the
2868 function type is sometimes called ''function returning T ''. The construction of a
2869 function type from a return type is called ''function type derivation''.
2870 <li> A pointer type may be derived from a function type or an object type, called the
2871 referenced type. A pointer type describes an object whose value provides a reference
2872 to an entity of the referenced type. A pointer type derived from the referenced type T
2873 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2874 referenced type is called ''pointer type derivation''. A pointer type is a complete
2876 <li> An atomic type describes the type designated by the construct _Atomic ( type-
2877 name ). (Atomic types are a conditional feature that implementations need not
2878 support; see <a href="#6.10.8.3">6.10.8.3</a>.)
2880 These methods of constructing derived types can be applied recursively.
2881 <p><a name="6.2.5p21" href="#6.2.5p21"><small>21</small></a>
2882 Arithmetic types and pointer types are collectively called scalar types. Array and
2883 structure types are collectively called aggregate types.<sup><a href="#note46"><b>46)</b></a></sup>
2884 <p><a name="6.2.5p22" href="#6.2.5p22"><small>22</small></a>
2885 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2886 that type, by specifying the size in a later declaration (with internal or external linkage).
2887 A structure or union type of unknown content (as described in <a href="#6.7.2.3">6.7.2.3</a>) is an incomplete
2891 type. It is completed, for all declarations of that type, by declaring the same structure or
2892 union tag with its defining content later in the same scope.
2893 <p><a name="6.2.5p23" href="#6.2.5p23"><small>23</small></a>
2894 A type has known constant size if the type is not incomplete and is not a variable length
2896 <p><a name="6.2.5p24" href="#6.2.5p24"><small>24</small></a>
2897 Array, function, and pointer types are collectively called derived declarator types. A
2898 declarator type derivation from a type T is the construction of a derived declarator type
2899 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2901 <p><a name="6.2.5p25" href="#6.2.5p25"><small>25</small></a>
2902 A type is characterized by its type category, which is either the outermost derivation of a
2903 derived type (as noted above in the construction of derived types), or the type itself if the
2904 type consists of no derived types.
2905 <p><a name="6.2.5p26" href="#6.2.5p26"><small>26</small></a>
2906 Any type so far mentioned is an unqualified type. Each unqualified type has several
2907 qualified versions of its type,<sup><a href="#note47"><b>47)</b></a></sup> corresponding to the combinations of one, two, or all
2908 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2909 versions of a type are distinct types that belong to the same type category and have the
2910 same representation and alignment requirements.<sup><a href="#note48"><b>48)</b></a></sup> A derived type is not qualified by the
2911 qualifiers (if any) of the type from which it is derived.
2912 <p><a name="6.2.5p27" href="#6.2.5p27"><small>27</small></a>
2913 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier
2914 designates an atomic type. The size, representation, and alignment of an atomic type
2915 need not be the same as those of the corresponding unqualified type. Therefore, this
2916 Standard explicitly uses the phrase ''atomic, qualified or unqualified type'' whenever the
2917 atomic version of a type is permitted along with the other qualified versions of a type.
2918 The phrase ''qualified or unqualified type'', without specific mention of atomic, does not
2919 include the atomic types.
2920 <p><a name="6.2.5p28" href="#6.2.5p28"><small>28</small></a>
2921 A pointer to void shall have the same representation and alignment requirements as a
2922 pointer to a character type.<sup><a href="#note48"><b>48)</b></a></sup> Similarly, pointers to qualified or unqualified versions of
2923 compatible types shall have the same representation and alignment requirements. All
2924 pointers to structure types shall have the same representation and alignment requirements
2925 as each other. All pointers to union types shall have the same representation and
2926 alignment requirements as each other. Pointers to other types need not have the same
2927 representation or alignment requirements.
2928 <p><a name="6.2.5p29" href="#6.2.5p29"><small>29</small></a>
2929 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2930 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2931 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2935 qualified float'' and is a pointer to a qualified type.
2937 <p><a name="6.2.5p30" href="#6.2.5p30"><small>30</small></a>
2938 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2939 function returning struct tag''. The array has length five and the function has a single parameter of type
2940 float. Its type category is array.
2942 <p><b> Forward references</b>: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2945 <p><small><a name="note37" href="#note37">37)</a> A type may be incomplete or complete throughout an entire translation unit, or it may change states at
2946 different points within a translation unit.
2948 <p><small><a name="note38" href="#note38">38)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2949 described in <a href="#7.1.3">7.1.3</a>.
2951 <p><small><a name="note39" href="#note39">39)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2952 signed integer types.
2954 <p><small><a name="note40" href="#note40">40)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2955 unsigned integer types.
2957 <p><small><a name="note41" href="#note41">41)</a> The same representation and alignment requirements are meant to imply interchangeability as
2958 arguments to functions, return values from functions, and members of unions.
2960 <p><small><a name="note42" href="#note42">42)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2962 <p><small><a name="note43" href="#note43">43)</a> A specification for imaginary types is in <a href="#G">annex G</a>.
2964 <p><small><a name="note44" href="#note44">44)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2965 any other) type; this does not violate the requirement that all basic types be different.
2966 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2967 described in <a href="#7.1.3">7.1.3</a>.
2969 <p><small><a name="note45" href="#note45">45)</a> CHAR_MIN, defined in <a href="#7.10"><limits.h></a>, will have one of the values 0 or SCHAR_MIN, and this can be
2970 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2971 other two and is not compatible with either.
2973 <p><small><a name="note46" href="#note46">46)</a> Note that aggregate type does not include union type because an object with union type can only
2974 contain one member at a time.
2976 <p><small><a name="note47" href="#note47">47)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2978 <p><small><a name="note48" href="#note48">48)</a> The same representation and alignment requirements are meant to imply interchangeability as
2979 arguments to functions, return values from functions, and members of unions.
2982 <p><small><a href="#Contents">Contents</a></small>
2983 <h4><a name="6.2.6" href="#6.2.6">6.2.6 Representations of types</a></h4>
2985 <p><small><a href="#Contents">Contents</a></small>
2986 <h5><a name="6.2.6.1" href="#6.2.6.1">6.2.6.1 General</a></h5>
2987 <p><a name="6.2.6.1p1" href="#6.2.6.1p1"><small>1</small></a>
2988 The representations of all types are unspecified except as stated in this subclause.
2989 <p><a name="6.2.6.1p2" href="#6.2.6.1p2"><small>2</small></a>
2990 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2991 the number, order, and encoding of which are either explicitly specified or
2992 implementation-defined.
2993 <p><a name="6.2.6.1p3" href="#6.2.6.1p3"><small>3</small></a>
2994 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2995 represented using a pure binary notation.<sup><a href="#note49"><b>49)</b></a></sup>
2996 <p><a name="6.2.6.1p4" href="#6.2.6.1p4"><small>4</small></a>
2997 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2998 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2999 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
3000 called the object representation of the value. Values stored in bit-fields consist of m bits,
3001 where m is the size specified for the bit-field. The object representation is the set of m
3002 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
3003 than NaNs) with the same object representation compare equal, but values that compare
3004 equal may have different object representations.
3005 <p><a name="6.2.6.1p5" href="#6.2.6.1p5"><small>5</small></a>
3006 Certain object representations need not represent a value of the object type. If the stored
3007 value of an object has such a representation and is read by an lvalue expression that does
3008 not have character type, the behavior is undefined. If such a representation is produced
3009 by a side effect that modifies all or any part of the object by an lvalue expression that
3010 does not have character type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup> Such a representation is called
3011 a trap representation.
3012 <p><a name="6.2.6.1p6" href="#6.2.6.1p6"><small>6</small></a>
3013 When a value is stored in an object of structure or union type, including in a member
3014 object, the bytes of the object representation that correspond to any padding bytes take
3015 unspecified values.<sup><a href="#note51"><b>51)</b></a></sup> The value of a structure or union object is never a trap
3019 representation, even though the value of a member of the structure or union object may be
3020 a trap representation.
3021 <p><a name="6.2.6.1p7" href="#6.2.6.1p7"><small>7</small></a>
3022 When a value is stored in a member of an object of union type, the bytes of the object
3023 representation that do not correspond to that member but do correspond to other members
3024 take unspecified values.
3025 <p><a name="6.2.6.1p8" href="#6.2.6.1p8"><small>8</small></a>
3026 Where an operator is applied to a value that has more than one object representation,
3027 which object representation is used shall not affect the value of the result.<sup><a href="#note52"><b>52)</b></a></sup> Where a
3028 value is stored in an object using a type that has more than one object representation for
3029 that value, it is unspecified which representation is used, but a trap representation shall
3031 <p><a name="6.2.6.1p9" href="#6.2.6.1p9"><small>9</small></a>
3032 Loads and stores of objects with atomic types are done with
3033 memory_order_seq_cst semantics.
3034 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
3035 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
3038 <p><small><a name="note49" href="#note49">49)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
3039 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
3040 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
3041 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
3042 type unsigned char range from 0 to 2
3049 <p><small><a name="note50" href="#note50">50)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
3050 behavior, but the value of the variable cannot be used until a proper value is stored in it.
3052 <p><small><a name="note51" href="#note51">51)</a> Thus, for example, structure assignment need not copy any padding bits.
3054 <p><small><a name="note52" href="#note52">52)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
3055 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
3056 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
3057 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
3058 on values of type T may distinguish between them.
3061 <p><small><a href="#Contents">Contents</a></small>
3062 <h5><a name="6.2.6.2" href="#6.2.6.2">6.2.6.2 Integer types</a></h5>
3063 <p><a name="6.2.6.2p1" href="#6.2.6.2p1"><small>1</small></a>
3064 For unsigned integer types other than unsigned char, the bits of the object
3065 representation shall be divided into two groups: value bits and padding bits (there need
3066 not be any of the latter). If there are N value bits, each bit shall represent a different
3067 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
3068 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
3069 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note53"><b>53)</b></a></sup>
3070 <p><a name="6.2.6.2p2" href="#6.2.6.2p2"><small>2</small></a>
3071 For signed integer types, the bits of the object representation shall be divided into three
3072 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
3073 signed char shall not have any padding bits. There shall be exactly one sign bit.
3074 Each bit that is a value bit shall have the same value as the same bit in the object
3075 representation of the corresponding unsigned type (if there are M value bits in the signed
3076 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
3079 the resulting value. If the sign bit is one, the value shall be modified in one of the
3082 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
3083 <li> the sign bit has the value -(2 M ) (two's complement);
3084 <li> the sign bit has the value -(2 M - 1) (ones' complement).
3086 Which of these applies is implementation-defined, as is whether the value with sign bit 1
3087 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
3088 complement), is a trap representation or a normal value. In the case of sign and
3089 magnitude and ones' complement, if this representation is a normal value it is called a
3091 <p><a name="6.2.6.2p3" href="#6.2.6.2p3"><small>3</small></a>
3092 If the implementation supports negative zeros, they shall be generated only by:
3094 <li> the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
3095 <li> the +, -, *, /, and % operators where one operand is a negative zero and the result is
3097 <li> compound assignment operators based on the above cases.
3099 It is unspecified whether these cases actually generate a negative zero or a normal zero,
3100 and whether a negative zero becomes a normal zero when stored in an object.
3101 <p><a name="6.2.6.2p4" href="#6.2.6.2p4"><small>4</small></a>
3102 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
3103 and >> operators with operands that would produce such a value is undefined.
3104 <p><a name="6.2.6.2p5" href="#6.2.6.2p5"><small>5</small></a>
3105 The values of any padding bits are unspecified.<sup><a href="#note54"><b>54)</b></a></sup> A valid (non-trap) object representation
3106 of a signed integer type where the sign bit is zero is a valid object representation of the
3107 corresponding unsigned type, and shall represent the same value. For any integer type,
3108 the object representation where all the bits are zero shall be a representation of the value
3110 <p><a name="6.2.6.2p6" href="#6.2.6.2p6"><small>6</small></a>
3111 The precision of an integer type is the number of bits it uses to represent values,
3112 excluding any sign and padding bits. The width of an integer type is the same but
3113 including any sign bit; thus for unsigned integer types the two values are the same, while
3114 for signed integer types the width is one greater than the precision.
3122 <p><small><a name="note53" href="#note53">53)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3123 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3124 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
3125 with unsigned types. All other combinations of padding bits are alternative object representations of
3126 the value specified by the value bits.
3128 <p><small><a name="note54" href="#note54">54)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3129 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3130 representation other than as part of an exceptional condition such as an overflow. All other
3131 combinations of padding bits are alternative object representations of the value specified by the value
3135 <p><small><a href="#Contents">Contents</a></small>
3136 <h4><a name="6.2.7" href="#6.2.7">6.2.7 Compatible type and composite type</a></h4>
3137 <p><a name="6.2.7p1" href="#6.2.7p1"><small>1</small></a>
3138 Two types have compatible type if their types are the same. Additional rules for
3139 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
3140 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.6">6.7.6</a> for declarators.<sup><a href="#note55"><b>55)</b></a></sup> Moreover, two structure,
3141 union, or enumerated types declared in separate translation units are compatible if their
3142 tags and members satisfy the following requirements: If one is declared with a tag, the
3143 other shall be declared with the same tag. If both are completed anywhere within their
3144 respective translation units, then the following additional requirements apply: there shall
3145 be a one-to-one correspondence between their members such that each pair of
3146 corresponding members are declared with compatible types; if one member of the pair is
3147 declared with an alignment specifier, the other is declared with an equivalent alignment
3148 specifier; and if one member of the pair is declared with a name, the other is declared
3149 with the same name. For two structures, corresponding members shall be declared in the
3150 same order. For two structures or unions, corresponding bit-fields shall have the same
3151 widths. For two enumerations, corresponding members shall have the same values.
3152 <p><a name="6.2.7p2" href="#6.2.7p2"><small>2</small></a>
3153 All declarations that refer to the same object or function shall have compatible type;
3154 otherwise, the behavior is undefined.
3155 <p><a name="6.2.7p3" href="#6.2.7p3"><small>3</small></a>
3156 A composite type can be constructed from two types that are compatible; it is a type that
3157 is compatible with both of the two types and satisfies the following conditions:
3159 <li> If both types are array types, the following rules are applied:
3161 <li> If one type is an array of known constant size, the composite type is an array of
3163 <li> Otherwise, if one type is a variable length array whose size is specified by an
3164 expression that is not evaluated, the behavior is undefined.
3165 <li> Otherwise, if one type is a variable length array whose size is specified, the
3166 composite type is a variable length array of that size.
3167 <li> Otherwise, if one type is a variable length array of unspecified size, the composite
3168 type is a variable length array of unspecified size.
3169 <li> Otherwise, both types are arrays of unknown size and the composite type is an
3170 array of unknown size.
3172 The element type of the composite type is the composite type of the two element
3174 <li> If only one type is a function type with a parameter type list (a function prototype),
3175 the composite type is a function prototype with the parameter type list.
3179 <li> If both types are function types with parameter type lists, the type of each parameter
3180 in the composite parameter type list is the composite type of the corresponding
3183 These rules apply recursively to the types from which the two types are derived.
3184 <p><a name="6.2.7p4" href="#6.2.7p4"><small>4</small></a>
3185 For an identifier with internal or external linkage declared in a scope in which a prior
3186 declaration of that identifier is visible,<sup><a href="#note56"><b>56)</b></a></sup> if the prior declaration specifies internal or
3187 external linkage, the type of the identifier at the later declaration becomes the composite
3189 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
3190 <p><a name="6.2.7p5" href="#6.2.7p5"><small>5</small></a>
3191 EXAMPLE Given the following two file scope declarations:
3193 int f(int (*)(), double (*)[3]);
3194 int f(int (*)(char *), double (*)[]);
3196 The resulting composite type for the function is:
3198 int f(int (*)(char *), double (*)[3]);
3203 <p><small><a name="note55" href="#note55">55)</a> Two types need not be identical to be compatible.
3205 <p><small><a name="note56" href="#note56">56)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
3208 <p><small><a href="#Contents">Contents</a></small>
3209 <h4><a name="6.2.8" href="#6.2.8">6.2.8 Alignment of objects</a></h4>
3210 <p><a name="6.2.8p1" href="#6.2.8p1"><small>1</small></a>
3211 Complete object types have alignment requirements which place restrictions on the
3212 addresses at which objects of that type may be allocated. An alignment is an
3213 implementation-defined integer value representing the number of bytes between
3214 successive addresses at which a given object can be allocated. An object type imposes an
3215 alignment requirement on every object of that type: stricter alignment can be requested
3216 using the _Alignas keyword.
3217 <p><a name="6.2.8p2" href="#6.2.8p2"><small>2</small></a>
3218 A fundamental alignment is represented by an alignment less than or equal to the greatest
3219 alignment supported by the implementation in all contexts, which is equal to
3220 _Alignof (max_align_t).
3221 <p><a name="6.2.8p3" href="#6.2.8p3"><small>3</small></a>
3222 An extended alignment is represented by an alignment greater than
3223 _Alignof (max_align_t). It is implementation-defined whether any extended
3224 alignments are supported and the contexts in which they are supported. A type having an
3225 extended alignment requirement is an over-aligned type.<sup><a href="#note57"><b>57)</b></a></sup>
3226 <p><a name="6.2.8p4" href="#6.2.8p4"><small>4</small></a>
3227 Alignments are represented as values of the type size_t. Valid alignments include only
3228 those values returned by an _Alignof expression for fundamental types, plus an
3229 additional implementation-defined set of values, which may be empty. Every valid
3230 alignment value shall be a nonnegative integral power of two.
3234 <p><a name="6.2.8p5" href="#6.2.8p5"><small>5</small></a>
3235 Alignments have an order from weaker to stronger or stricter alignments. Stricter
3236 alignments have larger alignment values. An address that satisfies an alignment
3237 requirement also satisfies any weaker valid alignment requirement.
3238 <p><a name="6.2.8p6" href="#6.2.8p6"><small>6</small></a>
3239 The alignment requirement of a complete type can be queried using an _Alignof
3240 expression. The types char, signed char, and unsigned char shall have the
3241 weakest alignment requirement.
3242 <p><a name="6.2.8p7" href="#6.2.8p7"><small>7</small></a>
3243 Comparing alignments is meaningful and provides the obvious results:
3245 <li> Two alignments are equal when their numeric values are equal.
3246 <li> Two alignments are different when their numeric values are not equal.
3247 <li> When an alignment is larger than another it represents a stricter alignment.
3252 <p><small><a name="note57" href="#note57">57)</a> Every over-aligned type is, or contains, a structure or union type with a member to which an extended
3253 alignment has been applied.
3256 <p><small><a href="#Contents">Contents</a></small>
3257 <h3><a name="6.3" href="#6.3">6.3 Conversions</a></h3>
3258 <p><a name="6.3p1" href="#6.3p1"><small>1</small></a>
3259 Several operators convert operand values from one type to another automatically. This
3260 subclause specifies the result required from such an implicit conversion, as well as those
3261 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
3262 the conversions performed by most ordinary operators; it is supplemented as required by
3263 the discussion of each operator in <a href="#6.5">6.5</a>.
3264 <p><a name="6.3p2" href="#6.3p2"><small>2</small></a>
3265 Conversion of an operand value to a compatible type causes no change to the value or the
3267 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>).
3269 <p><small><a href="#Contents">Contents</a></small>
3270 <h4><a name="6.3.1" href="#6.3.1">6.3.1 Arithmetic operands</a></h4>
3272 <p><small><a href="#Contents">Contents</a></small>
3273 <h5><a name="6.3.1.1" href="#6.3.1.1">6.3.1.1 Boolean, characters, and integers</a></h5>
3274 <p><a name="6.3.1.1p1" href="#6.3.1.1p1"><small>1</small></a>
3275 Every integer type has an integer conversion rank defined as follows:
3277 <li> No two signed integer types shall have the same rank, even if they have the same
3279 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
3280 type with less precision.
3281 <li> The rank of long long int shall be greater than the rank of long int, which
3282 shall be greater than the rank of int, which shall be greater than the rank of short
3283 int, which shall be greater than the rank of signed char.
3284 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
3285 signed integer type, if any.
3286 <li> The rank of any standard integer type shall be greater than the rank of any extended
3287 integer type with the same width.
3288 <li> The rank of char shall equal the rank of signed char and unsigned char.
3289 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
3290 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
3291 (see <a href="#6.7.2.2">6.7.2.2</a>).
3292 <li> The rank of any extended signed integer type relative to another extended signed
3293 integer type with the same precision is implementation-defined, but still subject to the
3294 other rules for determining the integer conversion rank.
3295 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
3296 greater rank than T3, then T1 has greater rank than T3.
3298 <p><a name="6.3.1.1p2" href="#6.3.1.1p2"><small>2</small></a>
3299 The following may be used in an expression wherever an int or unsigned int may
3303 <li> An object or expression with an integer type (other than int or unsigned int)
3304 whose integer conversion rank is less than or equal to the rank of int and
3306 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
3308 If an int can represent all values of the original type (as restricted by the width, for a
3309 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
3310 int. These are called the integer promotions.<sup><a href="#note58"><b>58)</b></a></sup> All other types are unchanged by the
3312 <p><a name="6.3.1.1p3" href="#6.3.1.1p3"><small>3</small></a>
3313 The integer promotions preserve value including sign. As discussed earlier, whether a
3314 ''plain'' char is treated as signed is implementation-defined.
3315 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
3316 (<a href="#6.7.2.1">6.7.2.1</a>).
3319 <p><small><a name="note58" href="#note58">58)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
3320 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
3321 shift operators, as specified by their respective subclauses.
3324 <p><small><a href="#Contents">Contents</a></small>
3325 <h5><a name="6.3.1.2" href="#6.3.1.2">6.3.1.2 Boolean type</a></h5>
3326 <p><a name="6.3.1.2p1" href="#6.3.1.2p1"><small>1</small></a>
3327 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
3328 to 0; otherwise, the result is 1.<sup><a href="#note59"><b>59)</b></a></sup>
3331 <p><small><a name="note59" href="#note59">59)</a> NaNs do not compare equal to 0 and thus convert to 1.
3334 <p><small><a href="#Contents">Contents</a></small>
3335 <h5><a name="6.3.1.3" href="#6.3.1.3">6.3.1.3 Signed and unsigned integers</a></h5>
3336 <p><a name="6.3.1.3p1" href="#6.3.1.3p1"><small>1</small></a>
3337 When a value with integer type is converted to another integer type other than _Bool, if
3338 the value can be represented by the new type, it is unchanged.
3339 <p><a name="6.3.1.3p2" href="#6.3.1.3p2"><small>2</small></a>
3340 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
3341 subtracting one more than the maximum value that can be represented in the new type
3342 until the value is in the range of the new type.<sup><a href="#note60"><b>60)</b></a></sup>
3343 <p><a name="6.3.1.3p3" href="#6.3.1.3p3"><small>3</small></a>
3344 Otherwise, the new type is signed and the value cannot be represented in it; either the
3345 result is implementation-defined or an implementation-defined signal is raised.
3348 <p><small><a name="note60" href="#note60">60)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
3351 <p><small><a href="#Contents">Contents</a></small>
3352 <h5><a name="6.3.1.4" href="#6.3.1.4">6.3.1.4 Real floating and integer</a></h5>
3353 <p><a name="6.3.1.4p1" href="#6.3.1.4p1"><small>1</small></a>
3354 When a finite value of real floating type is converted to an integer type other than _Bool,
3355 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
3356 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note61"><b>61)</b></a></sup>
3360 <p><a name="6.3.1.4p2" href="#6.3.1.4p2"><small>2</small></a>
3361 When a value of integer type is converted to a real floating type, if the value being
3362 converted can be represented exactly in the new type, it is unchanged. If the value being
3363 converted is in the range of values that can be represented but cannot be represented
3364 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3365 in an implementation-defined manner. If the value being converted is outside the range of
3366 values that can be represented, the behavior is undefined. Results of some implicit
3367 conversions may be represented in greater range and precision than that required by the
3368 new type (see <a href="#6.3.1.8">6.3.1.8</a> and <a href="#6.8.6.4">6.8.6.4</a>).
3371 <p><small><a name="note61" href="#note61">61)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
3372 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
3373 range of portable real floating values is (-1, Utype_MAX+1).
3376 <p><small><a href="#Contents">Contents</a></small>
3377 <h5><a name="6.3.1.5" href="#6.3.1.5">6.3.1.5 Real floating types</a></h5>
3378 <p><a name="6.3.1.5p1" href="#6.3.1.5p1"><small>1</small></a>
3379 When a value of real floating type is converted to a real floating type, if the value being
3380 converted can be represented exactly in the new type, it is unchanged. If the value being
3381 converted is in the range of values that can be represented but cannot be represented
3382 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3383 in an implementation-defined manner. If the value being converted is outside the range of
3384 values that can be represented, the behavior is undefined. Results of some implicit
3385 conversions may be represented in greater range and precision than that required by the
3386 new type (see <a href="#6.3.1.8">6.3.1.8</a> and <a href="#6.8.6.4">6.8.6.4</a>).
3388 <p><small><a href="#Contents">Contents</a></small>
3389 <h5><a name="6.3.1.6" href="#6.3.1.6">6.3.1.6 Complex types</a></h5>
3390 <p><a name="6.3.1.6p1" href="#6.3.1.6p1"><small>1</small></a>
3391 When a value of complex type is converted to another complex type, both the real and
3392 imaginary parts follow the conversion rules for the corresponding real types.
3394 <p><small><a href="#Contents">Contents</a></small>
3395 <h5><a name="6.3.1.7" href="#6.3.1.7">6.3.1.7 Real and complex</a></h5>
3396 <p><a name="6.3.1.7p1" href="#6.3.1.7p1"><small>1</small></a>
3397 When a value of real type is converted to a complex type, the real part of the complex
3398 result value is determined by the rules of conversion to the corresponding real type and
3399 the imaginary part of the complex result value is a positive zero or an unsigned zero.
3400 <p><a name="6.3.1.7p2" href="#6.3.1.7p2"><small>2</small></a>
3401 When a value of complex type is converted to a real type, the imaginary part of the
3402 complex value is discarded and the value of the real part is converted according to the
3403 conversion rules for the corresponding real type.
3405 <p><small><a href="#Contents">Contents</a></small>
3406 <h5><a name="6.3.1.8" href="#6.3.1.8">6.3.1.8 Usual arithmetic conversions</a></h5>
3407 <p><a name="6.3.1.8p1" href="#6.3.1.8p1"><small>1</small></a>
3408 Many operators that expect operands of arithmetic type cause conversions and yield result
3409 types in a similar way. The purpose is to determine a common real type for the operands
3410 and result. For the specified operands, each operand is converted, without change of type
3411 domain, to a type whose corresponding real type is the common real type. Unless
3412 explicitly stated otherwise, the common real type is also the corresponding real type of
3413 the result, whose type domain is the type domain of the operands if they are the same,
3414 and complex otherwise. This pattern is called the usual arithmetic conversions:
3417 First, if the corresponding real type of either operand is long double, the other
3418 operand is converted, without change of type domain, to a type whose
3419 corresponding real type is long double.
3420 Otherwise, if the corresponding real type of either operand is double, the other
3421 operand is converted, without change of type domain, to a type whose
3422 corresponding real type is double.
3423 Otherwise, if the corresponding real type of either operand is float, the other
3424 operand is converted, without change of type domain, to a type whose
3425 corresponding real type is float.<sup><a href="#note62"><b>62)</b></a></sup>
3426 Otherwise, the integer promotions are performed on both operands. Then the
3427 following rules are applied to the promoted operands:
3428 If both operands have the same type, then no further conversion is needed.
3429 Otherwise, if both operands have signed integer types or both have unsigned
3430 integer types, the operand with the type of lesser integer conversion rank is
3431 converted to the type of the operand with greater rank.
3432 Otherwise, if the operand that has unsigned integer type has rank greater or
3433 equal to the rank of the type of the other operand, then the operand with
3434 signed integer type is converted to the type of the operand with unsigned
3436 Otherwise, if the type of the operand with signed integer type can represent
3437 all of the values of the type of the operand with unsigned integer type, then
3438 the operand with unsigned integer type is converted to the type of the
3439 operand with signed integer type.
3440 Otherwise, both operands are converted to the unsigned integer type
3441 corresponding to the type of the operand with signed integer type.
3443 <p><a name="6.3.1.8p2" href="#6.3.1.8p2"><small>2</small></a>
3444 The values of floating operands and of the results of floating expressions may be
3445 represented in greater range and precision than that required by the type; the types are not
3446 changed thereby.<sup><a href="#note63"><b>63)</b></a></sup>
3454 <p><small><a name="note62" href="#note62">62)</a> For example, addition of a double _Complex and a float entails just the conversion of the
3455 float operand to double (and yields a double _Complex result).
3457 <p><small><a name="note63" href="#note63">63)</a> The cast and assignment operators are still required to remove extra range and precision.
3460 <p><small><a href="#Contents">Contents</a></small>
3461 <h4><a name="6.3.2" href="#6.3.2">6.3.2 Other operands</a></h4>
3463 <p><small><a href="#Contents">Contents</a></small>
3464 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
3465 <p><a name="6.3.2.1p1" href="#6.3.2.1p1"><small>1</small></a>
3466 An lvalue is an expression (with an object type other than void) that potentially
3467 designates an object;<sup><a href="#note64"><b>64)</b></a></sup> if an lvalue does not designate an object when it is evaluated, the
3468 behavior is undefined. When an object is said to have a particular type, the type is
3469 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
3470 does not have array type, does not have an incomplete type, does not have a const-
3471 qualified type, and if it is a structure or union, does not have any member (including,
3472 recursively, any member or element of all contained aggregates or unions) with a const-
3474 <p><a name="6.3.2.1p2" href="#6.3.2.1p2"><small>2</small></a>
3475 Except when it is the operand of the sizeof operator, the _Alignof operator, the
3476 unary & operator, the ++ operator, the -- operator, or the left operand of the . operator
3477 or an assignment operator, an lvalue that does not have array type is converted to the
3478 value stored in the designated object (and is no longer an lvalue); this is called lvalue
3479 conversion. If the lvalue has qualified type, the value has the unqualified version of the
3480 type of the lvalue; additionally, if the lvalue has atomic type, the value has the non-atomic
3481 version of the type of the lvalue; otherwise, the value has the type of the lvalue. If the
3482 lvalue has an incomplete type and does not have array type, the behavior is undefined. If
3483 the lvalue designates an object of automatic storage duration that could have been
3484 declared with the register storage class (never had its address taken), and that object
3485 is uninitialized (not declared with an initializer and no assignment to it has been
3486 performed prior to use), the behavior is undefined.
3487 <p><a name="6.3.2.1p3" href="#6.3.2.1p3"><small>3</small></a>
3488 Except when it is the operand of the sizeof operator, the _Alignof operator, or the
3489 unary & operator, or is a string literal used to initialize an array, an expression that has
3490 type ''array of type'' is converted to an expression with type ''pointer to type'' that points
3491 to the initial element of the array object and is not an lvalue. If the array object has
3492 register storage class, the behavior is undefined.
3493 <p><a name="6.3.2.1p4" href="#6.3.2.1p4"><small>4</small></a>
3494 A function designator is an expression that has function type. Except when it is the
3495 operand of the sizeof operator, the _Alignof operator,<sup><a href="#note65"><b>65)</b></a></sup> or the unary & operator, a
3496 function designator with type ''function returning type'' is converted to an expression that
3500 has type ''pointer to function returning type''.
3501 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
3502 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), initialization (<a href="#6.7.9">6.7.9</a>), postfix
3503 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3504 (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof and _Alignof operators (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members
3505 (<a href="#6.5.2.3">6.5.2.3</a>).
3508 <p><small><a name="note64" href="#note64">64)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
3509 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
3510 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
3511 as the ''value of an expression''.
3512 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
3513 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
3515 <p><small><a name="note65" href="#note65">65)</a> Because this conversion does not occur, the operand of the sizeof or _Alignof operator remains
3516 a function designator and violates the constraints in <a href="#6.5.3.4">6.5.3.4</a>.
3519 <p><small><a href="#Contents">Contents</a></small>
3520 <h5><a name="6.3.2.2" href="#6.3.2.2">6.3.2.2 void</a></h5>
3521 <p><a name="6.3.2.2p1" href="#6.3.2.2p1"><small>1</small></a>
3522 The (nonexistent) value of a void expression (an expression that has type void) shall not
3523 be used in any way, and implicit or explicit conversions (except to void) shall not be
3524 applied to such an expression. If an expression of any other type is evaluated as a void
3525 expression, its value or designator is discarded. (A void expression is evaluated for its
3528 <p><small><a href="#Contents">Contents</a></small>
3529 <h5><a name="6.3.2.3" href="#6.3.2.3">6.3.2.3 Pointers</a></h5>
3530 <p><a name="6.3.2.3p1" href="#6.3.2.3p1"><small>1</small></a>
3531 A pointer to void may be converted to or from a pointer to any object type. A pointer to
3532 any object type may be converted to a pointer to void and back again; the result shall
3533 compare equal to the original pointer.
3534 <p><a name="6.3.2.3p2" href="#6.3.2.3p2"><small>2</small></a>
3535 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
3536 the q-qualified version of the type; the values stored in the original and converted pointers
3537 shall compare equal.
3538 <p><a name="6.3.2.3p3" href="#6.3.2.3p3"><small>3</small></a>
3539 An integer constant expression with the value 0, or such an expression cast to type
3540 void *, is called a null pointer constant.<sup><a href="#note66"><b>66)</b></a></sup> If a null pointer constant is converted to a
3541 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
3542 to a pointer to any object or function.
3543 <p><a name="6.3.2.3p4" href="#6.3.2.3p4"><small>4</small></a>
3544 Conversion of a null pointer to another pointer type yields a null pointer of that type.
3545 Any two null pointers shall compare equal.
3546 <p><a name="6.3.2.3p5" href="#6.3.2.3p5"><small>5</small></a>
3547 An integer may be converted to any pointer type. Except as previously specified, the
3548 result is implementation-defined, might not be correctly aligned, might not point to an
3549 entity of the referenced type, and might be a trap representation.<sup><a href="#note67"><b>67)</b></a></sup>
3550 <p><a name="6.3.2.3p6" href="#6.3.2.3p6"><small>6</small></a>
3551 Any pointer type may be converted to an integer type. Except as previously specified, the
3552 result is implementation-defined. If the result cannot be represented in the integer type,
3553 the behavior is undefined. The result need not be in the range of values of any integer
3558 <p><a name="6.3.2.3p7" href="#6.3.2.3p7"><small>7</small></a>
3559 A pointer to an object type may be converted to a pointer to a different object type. If the
3560 resulting pointer is not correctly aligned<sup><a href="#note68"><b>68)</b></a></sup> for the referenced type, the behavior is
3561 undefined. Otherwise, when converted back again, the result shall compare equal to the
3562 original pointer. When a pointer to an object is converted to a pointer to a character type,
3563 the result points to the lowest addressed byte of the object. Successive increments of the
3564 result, up to the size of the object, yield pointers to the remaining bytes of the object.
3565 <p><a name="6.3.2.3p8" href="#6.3.2.3p8"><small>8</small></a>
3566 A pointer to a function of one type may be converted to a pointer to a function of another
3567 type and back again; the result shall compare equal to the original pointer. If a converted
3568 pointer is used to call a function whose type is not compatible with the referenced type,
3569 the behavior is undefined.
3570 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>), equality operators (<a href="#6.5.9">6.5.9</a>), integer types
3571 capable of holding object pointers (<a href="#7.20.1.4">7.20.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
3579 <p><small><a name="note66" href="#note66">66)</a> The macro NULL is defined in <a href="#7.19"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.19">7.19</a>.
3581 <p><small><a name="note67" href="#note67">67)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
3582 be consistent with the addressing structure of the execution environment.
3584 <p><small><a name="note68" href="#note68">68)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
3585 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
3586 correctly aligned for a pointer to type C.
3589 <p><small><a href="#Contents">Contents</a></small>
3590 <h3><a name="6.4" href="#6.4">6.4 Lexical elements</a></h3>
3592 <p><a name="6.4p1" href="#6.4p1"><small>1</small></a>
3600 preprocessing-token:
3607 each non-white-space character that cannot be one of the above
3609 <p><b>Constraints</b>
3610 <p><a name="6.4p2" href="#6.4p2"><small>2</small></a>
3611 Each preprocessing token that is converted to a token shall have the lexical form of a
3612 keyword, an identifier, a constant, a string literal, or a punctuator.
3614 <p><a name="6.4p3" href="#6.4p3"><small>3</small></a>
3615 A token is the minimal lexical element of the language in translation phases 7 and 8. The
3616 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
3617 A preprocessing token is the minimal lexical element of the language in translation
3618 phases 3 through 6. The categories of preprocessing tokens are: header names,
3619 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
3620 single non-white-space characters that do not lexically match the other preprocessing
3621 token categories.<sup><a href="#note69"><b>69)</b></a></sup> If a ' or a " character matches the last category, the behavior is
3622 undefined. Preprocessing tokens can be separated by white space; this consists of
3623 comments (described later), or white-space characters (space, horizontal tab, new-line,
3624 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
3625 during translation phase 4, white space (or the absence thereof) serves as more than
3626 preprocessing token separation. White space may appear within a preprocessing token
3627 only as part of a header name or between the quotation characters in a character constant
3633 <p><a name="6.4p4" href="#6.4p4"><small>4</small></a>
3634 If the input stream has been parsed into preprocessing tokens up to a given character, the
3635 next preprocessing token is the longest sequence of characters that could constitute a
3636 preprocessing token. There is one exception to this rule: header name preprocessing
3637 tokens are recognized only within #include preprocessing directives and in
3638 implementation-defined locations within #pragma directives. In such contexts, a
3639 sequence of characters that could be either a header name or a string literal is recognized
3641 <p><a name="6.4p5" href="#6.4p5"><small>5</small></a>
3642 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
3643 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
3644 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
3645 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
3646 not E is a macro name.
3648 <p><a name="6.4p6" href="#6.4p6"><small>6</small></a>
3649 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
3650 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
3652 <p><b> Forward references</b>: character constants (<a href="#6.4.4.4">6.4.4.4</a>), comments (<a href="#6.4.9">6.4.9</a>), expressions (<a href="#6.5">6.5</a>),
3653 floating constants (<a href="#6.4.4.2">6.4.4.2</a>), header names (<a href="#6.4.7">6.4.7</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), postfix
3654 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3655 (<a href="#6.5.3.1">6.5.3.1</a>), preprocessing directives (<a href="#6.10">6.10</a>), preprocessing numbers (<a href="#6.4.8">6.4.8</a>), string literals
3656 (<a href="#6.4.5">6.4.5</a>).
3659 <p><small><a name="note69" href="#note69">69)</a> An additional category, placemarkers, is used internally in translation phase 4 (see <a href="#6.10.3.3">6.10.3.3</a>); it cannot
3660 occur in source files.
3663 <p><small><a href="#Contents">Contents</a></small>
3664 <h4><a name="6.4.1" href="#6.4.1">6.4.1 Keywords</a></h4>
3666 <p><a name="6.4.1p1" href="#6.4.1p1"><small>1</small></a>
3673 const register _Alignas
3674 continue restrict _Alignof
3675 default return _Atomic
3677 double signed _Complex
3678 else sizeof _Generic
3679 enum static _Imaginary
3680 extern struct _Noreturn
3681 float switch _Static_assert
3682 for typedef _Thread_local
3686 <p><a name="6.4.1p2" href="#6.4.1p2"><small>2</small></a>
3687 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
3688 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
3690 specifying imaginary types.<sup><a href="#note70"><b>70)</b></a></sup>
3693 <p><small><a name="note70" href="#note70">70)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
3696 <p><small><a href="#Contents">Contents</a></small>
3697 <h4><a name="6.4.2" href="#6.4.2">6.4.2 Identifiers</a></h4>
3699 <p><small><a href="#Contents">Contents</a></small>
3700 <h5><a name="6.4.2.1" href="#6.4.2.1">6.4.2.1 General</a></h5>
3702 <p><a name="6.4.2.1p1" href="#6.4.2.1p1"><small>1</small></a>
3706 identifier identifier-nondigit
3708 identifier-nondigit:
3710 universal-character-name
3711 other implementation-defined characters
3713 _ a b c d e f g h i j k l m
3714 n o p q r s t u v w x y z
3715 A B C D E F G H I J K L M
3716 N O P Q R S T U V W X Y Z
3721 <p><a name="6.4.2.1p2" href="#6.4.2.1p2"><small>2</small></a>
3722 An identifier is a sequence of nondigit characters (including the underscore _, the
3723 lowercase and uppercase Latin letters, and other characters) and digits, which designates
3724 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
3725 There is no specific limit on the maximum length of an identifier.
3726 <p><a name="6.4.2.1p3" href="#6.4.2.1p3"><small>3</small></a>
3727 Each universal character name in an identifier shall designate a character whose encoding
3728 in ISO/IEC 10646 falls into one of the ranges specified in D.1.<sup><a href="#note71"><b>71)</b></a></sup> The initial character
3729 shall not be a universal character name designating a character whose encoding falls into
3730 one of the ranges specified in <a href="#D.2">D.2</a>. An implementation may allow multibyte characters
3731 that are not part of the basic source character set to appear in identifiers; which characters
3732 and their correspondence to universal character names is implementation-defined.
3737 <p><a name="6.4.2.1p4" href="#6.4.2.1p4"><small>4</small></a>
3738 When preprocessing tokens are converted to tokens during translation phase 7, if a
3739 preprocessing token could be converted to either a keyword or an identifier, it is converted
3741 <p><b>Implementation limits</b>
3742 <p><a name="6.4.2.1p5" href="#6.4.2.1p5"><small>5</small></a>
3743 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
3744 characters in an identifier; the limit for an external name (an identifier that has external
3745 linkage) may be more restrictive than that for an internal name (a macro name or an
3746 identifier that does not have external linkage). The number of significant characters in an
3747 identifier is implementation-defined.
3748 <p><a name="6.4.2.1p6" href="#6.4.2.1p6"><small>6</small></a>
3749 Any identifiers that differ in a significant character are different identifiers. If two
3750 identifiers differ only in nonsignificant characters, the behavior is undefined.
3751 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>).
3754 <p><small><a name="note71" href="#note71">71)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
3755 name may be used in forming valid external identifiers. For example, some otherwise unused
3756 character or sequence of characters may be used to encode the \u in a universal character name.
3757 Extended characters may produce a long external identifier.
3760 <p><small><a href="#Contents">Contents</a></small>
3761 <h5><a name="6.4.2.2" href="#6.4.2.2">6.4.2.2 Predefined identifiers</a></h5>
3763 <p><a name="6.4.2.2p1" href="#6.4.2.2p1"><small>1</small></a>
3764 The identifier __func__ shall be implicitly declared by the translator as if,
3765 immediately following the opening brace of each function definition, the declaration
3767 static const char __func__[] = "function-name";
3769 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note72"><b>72)</b></a></sup>
3770 <p><a name="6.4.2.2p2" href="#6.4.2.2p2"><small>2</small></a>
3771 This name is encoded as if the implicit declaration had been written in the source
3772 character set and then translated into the execution character set as indicated in translation
3774 <p><a name="6.4.2.2p3" href="#6.4.2.2p3"><small>3</small></a>
3775 EXAMPLE Consider the code fragment:
3777 #include <a href="#7.21"><stdio.h></a>
3780 printf("%s\n", __func__);
3784 Each time the function is called, it will print to the standard output stream:
3789 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
3797 <p><small><a name="note72" href="#note72">72)</a> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
3798 identifier is explicitly declared using the name __func__, the behavior is undefined.
3801 <p><small><a href="#Contents">Contents</a></small>
3802 <h4><a name="6.4.3" href="#6.4.3">6.4.3 Universal character names</a></h4>
3804 <p><a name="6.4.3p1" href="#6.4.3p1"><small>1</small></a>
3806 universal-character-name:
3808 \U hex-quad hex-quad
3810 hexadecimal-digit hexadecimal-digit
3811 hexadecimal-digit hexadecimal-digit
3813 <p><b>Constraints</b>
3814 <p><a name="6.4.3p2" href="#6.4.3p2"><small>2</small></a>
3815 A universal character name shall not specify a character whose short identifier is less than
3816 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
3817 DFFF inclusive.<sup><a href="#note73"><b>73)</b></a></sup>
3818 <p><b>Description</b>
3819 <p><a name="6.4.3p3" href="#6.4.3p3"><small>3</small></a>
3820 Universal character names may be used in identifiers, character constants, and string
3821 literals to designate characters that are not in the basic character set.
3823 <p><a name="6.4.3p4" href="#6.4.3p4"><small>4</small></a>
3824 The universal character name \Unnnnnnnn designates the character whose eight-digit
3825 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note74"><b>74)</b></a></sup> Similarly, the universal
3826 character name \unnnn designates the character whose four-digit short identifier is nnnn
3827 (and whose eight-digit short identifier is 0000nnnn).
3835 <p><small><a name="note73" href="#note73">73)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
3836 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3840 <p><small><a name="note74" href="#note74">74)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3843 <p><small><a href="#Contents">Contents</a></small>
3844 <h4><a name="6.4.4" href="#6.4.4">6.4.4 Constants</a></h4>
3846 <p><a name="6.4.4p1" href="#6.4.4p1"><small>1</small></a>
3851 enumeration-constant
3854 <p><b>Constraints</b>
3855 <p><a name="6.4.4p2" href="#6.4.4p2"><small>2</small></a>
3856 Each constant shall have a type and the value of a constant shall be in the range of
3857 representable values for its type.
3859 <p><a name="6.4.4p3" href="#6.4.4p3"><small>3</small></a>
3860 Each constant has a type, determined by its form and value, as detailed later.
3862 <p><small><a href="#Contents">Contents</a></small>
3863 <h5><a name="6.4.4.1" href="#6.4.4.1">6.4.4.1 Integer constants</a></h5>
3865 <p><a name="6.4.4.1p1" href="#6.4.4.1p1"><small>1</small></a>
3869 decimal-constant integer-suffix<sub>opt</sub>
3870 octal-constant integer-suffix<sub>opt</sub>
3871 hexadecimal-constant integer-suffix<sub>opt</sub>
3874 decimal-constant digit
3877 octal-constant octal-digit
3878 hexadecimal-constant:
3879 hexadecimal-prefix hexadecimal-digit
3880 hexadecimal-constant hexadecimal-digit
3881 hexadecimal-prefix: one of
3883 nonzero-digit: one of
3887 hexadecimal-digit: one of
3892 unsigned-suffix long-suffix<sub>opt</sub>
3893 unsigned-suffix long-long-suffix
3894 long-suffix unsigned-suffix<sub>opt</sub>
3895 long-long-suffix unsigned-suffix<sub>opt</sub>
3896 unsigned-suffix: one of
3900 long-long-suffix: one of
3903 <p><b>Description</b>
3904 <p><a name="6.4.4.1p2" href="#6.4.4.1p2"><small>2</small></a>
3905 An integer constant begins with a digit, but has no period or exponent part. It may have a
3906 prefix that specifies its base and a suffix that specifies its type.
3907 <p><a name="6.4.4.1p3" href="#6.4.4.1p3"><small>3</small></a>
3908 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3909 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3910 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3911 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3912 10 through 15 respectively.
3914 <p><a name="6.4.4.1p4" href="#6.4.4.1p4"><small>4</small></a>
3915 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3916 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3917 <p><a name="6.4.4.1p5" href="#6.4.4.1p5"><small>5</small></a>
3918 The type of an integer constant is the first of the corresponding list in which its value can
3922 Octal or Hexadecimal
3924 Suffix Decimal Constant Constant
3928 long int unsigned int
3929 long long int long int
3932 unsigned long long int
3935 u or U unsigned int unsigned int
3937 unsigned long int unsigned long int
3938 unsigned long long int unsigned long long int
3941 l or L long int long int
3943 long long int unsigned long int
3945 unsigned long long int
3948 Both u or U unsigned long int unsigned long int
3949 and l or L unsigned long long int unsigned long long int
3951 ll or LL long long int long long int
3953 unsigned long long int
3956 Both u or U unsigned long long int unsigned long long int
3958 <p><a name="6.4.4.1p6" href="#6.4.4.1p6"><small>6</small></a>
3959 If an integer constant cannot be represented by any type in its list, it may have an
3960 extended integer type, if the extended integer type can represent its value. If all of the
3961 types in the list for the constant are signed, the extended integer type shall be signed. If
3962 all of the types in the list for the constant are unsigned, the extended integer type shall be
3963 unsigned. If the list contains both signed and unsigned types, the extended integer type
3964 may be signed or unsigned. If an integer constant cannot be represented by any type in
3965 its list and has no extended integer type, then the integer constant has no type.
3968 <p><small><a href="#Contents">Contents</a></small>
3969 <h5><a name="6.4.4.2" href="#6.4.4.2">6.4.4.2 Floating constants</a></h5>
3971 <p><a name="6.4.4.2p1" href="#6.4.4.2p1"><small>1</small></a>
3975 decimal-floating-constant
3976 hexadecimal-floating-constant
3977 decimal-floating-constant:
3978 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
3979 digit-sequence exponent-part floating-suffix<sub>opt</sub>
3980 hexadecimal-floating-constant:
3981 hexadecimal-prefix hexadecimal-fractional-constant
3982 binary-exponent-part floating-suffix<sub>opt</sub>
3983 hexadecimal-prefix hexadecimal-digit-sequence
3984 binary-exponent-part floating-suffix<sub>opt</sub>
3985 fractional-constant:
3986 digit-sequence<sub>opt</sub> . digit-sequence
3989 e sign<sub>opt</sub> digit-sequence
3990 E sign<sub>opt</sub> digit-sequence
3995 digit-sequence digit
3996 hexadecimal-fractional-constant:
3997 hexadecimal-digit-sequence<sub>opt</sub> .
3998 hexadecimal-digit-sequence
3999 hexadecimal-digit-sequence .
4000 binary-exponent-part:
4001 p sign<sub>opt</sub> digit-sequence
4002 P sign<sub>opt</sub> digit-sequence
4003 hexadecimal-digit-sequence:
4005 hexadecimal-digit-sequence hexadecimal-digit
4006 floating-suffix: one of
4009 <p><b>Description</b>
4010 <p><a name="6.4.4.2p2" href="#6.4.4.2p2"><small>2</small></a>
4011 A floating constant has a significand part that may be followed by an exponent part and a
4012 suffix that specifies its type. The components of the significand part may include a digit
4013 sequence representing the whole-number part, followed by a period (.), followed by a
4014 digit sequence representing the fraction part. The components of the exponent part are an
4015 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
4016 Either the whole-number part or the fraction part has to be present; for decimal floating
4017 constants, either the period or the exponent part has to be present.
4019 <p><a name="6.4.4.2p3" href="#6.4.4.2p3"><small>3</small></a>
4020 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
4021 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
4022 floating constants, the exponent indicates the power of 10 by which the significand part is
4023 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
4024 by which the significand part is to be scaled. For decimal floating constants, and also for
4025 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
4026 the nearest representable value, or the larger or smaller representable value immediately
4027 adjacent to the nearest representable value, chosen in an implementation-defined manner.
4028 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
4030 <p><a name="6.4.4.2p4" href="#6.4.4.2p4"><small>4</small></a>
4031 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
4032 type float. If suffixed by the letter l or L, it has type long double.
4033 <p><a name="6.4.4.2p5" href="#6.4.4.2p5"><small>5</small></a>
4034 Floating constants are converted to internal format as if at translation-time. The
4035 conversion of a floating constant shall not raise an exceptional condition or a floating-
4036 point exception at execution time. All floating constants of the same source form<sup><a href="#note75"><b>75)</b></a></sup> shall
4037 convert to the same internal format with the same value.
4038 <p><b>Recommended practice</b>
4039 <p><a name="6.4.4.2p6" href="#6.4.4.2p6"><small>6</small></a>
4040 The implementation should produce a diagnostic message if a hexadecimal constant
4041 cannot be represented exactly in its evaluation format; the implementation should then
4042 proceed with the translation of the program.
4043 <p><a name="6.4.4.2p7" href="#6.4.4.2p7"><small>7</small></a>
4044 The translation-time conversion of floating constants should match the execution-time
4045 conversion of character strings by library functions, such as strtod, given matching
4046 inputs suitable for both conversions, the same result format, and default execution-time
4047 rounding.<sup><a href="#note76"><b>76)</b></a></sup>
4052 <p><small><a name="note75" href="#note75">75)</a> <a href="#1.23">1.23</a>, 1.230, 123e-2, 123e-02, and 1.23L are all different source forms and thus need not
4053 convert to the same internal format and value.
4055 <p><small><a name="note76" href="#note76">76)</a> The specification for the library functions recommends more accurate conversion than required for
4056 floating constants (see <a href="#7.22.1.3">7.22.1.3</a>).
4059 <p><small><a href="#Contents">Contents</a></small>
4060 <h5><a name="6.4.4.3" href="#6.4.4.3">6.4.4.3 Enumeration constants</a></h5>
4062 <p><a name="6.4.4.3p1" href="#6.4.4.3p1"><small>1</small></a>
4064 enumeration-constant:
4068 <p><a name="6.4.4.3p2" href="#6.4.4.3p2"><small>2</small></a>
4069 An identifier declared as an enumeration constant has type int.
4070 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
4072 <p><small><a href="#Contents">Contents</a></small>
4073 <h5><a name="6.4.4.4" href="#6.4.4.4">6.4.4.4 Character constants</a></h5>
4075 <p><a name="6.4.4.4p1" href="#6.4.4.4p1"><small>1</small></a>
4080 L' c-char-sequence '
4081 u' c-char-sequence '
4082 U' c-char-sequence '
4085 c-char-sequence c-char
4087 any member of the source character set except
4088 the single-quote ', backslash \, or new-line character
4091 simple-escape-sequence
4092 octal-escape-sequence
4093 hexadecimal-escape-sequence
4094 universal-character-name
4095 simple-escape-sequence: one of
4097 \a \b \f \n \r \t \v
4098 octal-escape-sequence:
4100 \ octal-digit octal-digit
4101 \ octal-digit octal-digit octal-digit
4102 hexadecimal-escape-sequence:
4103 \x hexadecimal-digit
4104 hexadecimal-escape-sequence hexadecimal-digit
4106 <p><b>Description</b>
4107 <p><a name="6.4.4.4p2" href="#6.4.4.4p2"><small>2</small></a>
4108 An integer character constant is a sequence of one or more multibyte characters enclosed
4109 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
4110 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
4111 any members of the source character set; they are mapped in an implementation-defined
4112 manner to members of the execution character set.
4113 <p><a name="6.4.4.4p3" href="#6.4.4.4p3"><small>3</small></a>
4114 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
4115 arbitrary integer values are representable according to the following table of escape
4122 octal character \octal digits
4123 hexadecimal character \x hexadecimal digits
4125 <p><a name="6.4.4.4p4" href="#6.4.4.4p4"><small>4</small></a>
4126 The double-quote " and question-mark ? are representable either by themselves or by the
4127 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
4128 shall be represented, respectively, by the escape sequences \' and \\.
4129 <p><a name="6.4.4.4p5" href="#6.4.4.4p5"><small>5</small></a>
4130 The octal digits that follow the backslash in an octal escape sequence are taken to be part
4131 of the construction of a single character for an integer character constant or of a single
4132 wide character for a wide character constant. The numerical value of the octal integer so
4133 formed specifies the value of the desired character or wide character.
4134 <p><a name="6.4.4.4p6" href="#6.4.4.4p6"><small>6</small></a>
4135 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
4136 sequence are taken to be part of the construction of a single character for an integer
4137 character constant or of a single wide character for a wide character constant. The
4138 numerical value of the hexadecimal integer so formed specifies the value of the desired
4139 character or wide character.
4140 <p><a name="6.4.4.4p7" href="#6.4.4.4p7"><small>7</small></a>
4141 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
4142 constitute the escape sequence.
4143 <p><a name="6.4.4.4p8" href="#6.4.4.4p8"><small>8</small></a>
4144 In addition, characters not in the basic character set are representable by universal
4145 character names and certain nongraphic characters are representable by escape sequences
4146 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
4147 and \v.<sup><a href="#note77"><b>77)</b></a></sup>
4149 <p><b>Constraints</b>
4150 <p><a name="6.4.4.4p9" href="#6.4.4.4p9"><small>9</small></a>
4151 The value of an octal or hexadecimal escape sequence shall be in the range of
4152 representable values for the corresponding type:
4154 Prefix Corresponding Type
4156 L the unsigned type corresponding to wchar_t
4161 <p><a name="6.4.4.4p10" href="#6.4.4.4p10"><small>10</small></a>
4162 An integer character constant has type int. The value of an integer character constant
4163 containing a single character that maps to a single-byte execution character is the
4164 numerical value of the representation of the mapped character interpreted as an integer.
4165 The value of an integer character constant containing more than one character (e.g.,
4166 'ab'), or containing a character or escape sequence that does not map to a single-byte
4167 execution character, is implementation-defined. If an integer character constant contains
4168 a single character or escape sequence, its value is the one that results when an object with
4169 type char whose value is that of the single character or escape sequence is converted to
4171 <p><a name="6.4.4.4p11" href="#6.4.4.4p11"><small>11</small></a>
4172 A wide character constant prefixed by the letter L has type wchar_t, an integer type
4173 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
4174 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
4175 <a href="#7.28"><uchar.h></a> header. The value of a wide character constant containing a single
4176 multibyte character that maps to a single member of the extended execution character set
4177 is the wide character corresponding to that multibyte character, as defined by the
4178 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
4179 implementation-defined current locale. The value of a wide character constant containing
4180 more than one multibyte character or a single multibyte character that maps to multiple
4181 members of the extended execution character set, or containing a multibyte character or
4182 escape sequence not represented in the extended execution character set, is
4183 implementation-defined.
4184 <p><a name="6.4.4.4p12" href="#6.4.4.4p12"><small>12</small></a>
4185 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
4187 <p><a name="6.4.4.4p13" href="#6.4.4.4p13"><small>13</small></a>
4188 EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight
4189 bits for objects that have type char. In an implementation in which type char has the same range of
4190 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
4191 same range of values as unsigned char, the character constant '\xFF' has the value +255.
4197 <p><a name="6.4.4.4p14" href="#6.4.4.4p14"><small>14</small></a>
4198 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
4199 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
4200 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
4201 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
4202 escape sequence is terminated after three octal digits. (The value of this two-character integer character
4203 constant is implementation-defined.)
4205 <p><a name="6.4.4.4p15" href="#6.4.4.4p15"><small>15</small></a>
4206 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
4207 L'\1234' specifies the implementation-defined value that results from the combination of the values
4210 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
4211 (<a href="#7.22.7.2">7.22.7.2</a>), Unicode utilities <a href="#7.28"><uchar.h></a> (<a href="#7.28">7.28</a>).
4214 <p><small><a name="note77" href="#note77">77)</a> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
4215 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
4218 <p><small><a href="#Contents">Contents</a></small>
4219 <h4><a name="6.4.5" href="#6.4.5">6.4.5 String literals</a></h4>
4221 <p><a name="6.4.5p1" href="#6.4.5p1"><small>1</small></a>
4224 encoding-prefix<sub>opt</sub> " s-char-sequence<sub>opt</sub> "
4232 s-char-sequence s-char
4234 any member of the source character set except
4235 the double-quote ", backslash \, or new-line character
4238 <p><b>Constraints</b>
4239 <p><a name="6.4.5p2" href="#6.4.5p2"><small>2</small></a>
4240 A sequence of adjacent string literal tokens shall not include both a wide string literal and
4241 a UTF-8 string literal.
4242 <p><b>Description</b>
4243 <p><a name="6.4.5p3" href="#6.4.5p3"><small>3</small></a>
4244 A character string literal is a sequence of zero or more multibyte characters enclosed in
4245 double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8.
4246 A wide string literal is the same, except prefixed by the letter L, u, or U.
4247 <p><a name="6.4.5p4" href="#6.4.5p4"><small>4</small></a>
4248 The same considerations apply to each element of the sequence in a string literal as if it
4249 were in an integer character constant (for a character or UTF-8 string literal) or a wide
4250 character constant (for a wide string literal), except that the single-quote ' is
4251 representable either by itself or by the escape sequence \', but the double-quote " shall
4253 be represented by the escape sequence \".
4255 <p><a name="6.4.5p5" href="#6.4.5p5"><small>5</small></a>
4256 In translation phase 6, the multibyte character sequences specified by any sequence of
4257 adjacent character and identically-prefixed string literal tokens are concatenated into a
4258 single multibyte character sequence. If any of the tokens has an encoding prefix, the
4259 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
4260 is treated as a character string literal. Whether differently-prefixed wide string literal
4261 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
4262 sequence are implementation-defined.
4263 <p><a name="6.4.5p6" href="#6.4.5p6"><small>6</small></a>
4264 In translation phase 7, a byte or code of value zero is appended to each multibyte
4265 character sequence that results from a string literal or literals.<sup><a href="#note78"><b>78)</b></a></sup> The multibyte character
4266 sequence is then used to initialize an array of static storage duration and length just
4267 sufficient to contain the sequence. For character string literals, the array elements have
4268 type char, and are initialized with the individual bytes of the multibyte character
4269 sequence. For UTF-8 string literals, the array elements have type char, and are
4270 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
4271 For wide string literals prefixed by the letter L, the array elements have type wchar_t
4272 and are initialized with the sequence of wide characters corresponding to the multibyte
4273 character sequence, as defined by the mbstowcs function with an implementation-
4274 defined current locale. For wide string literals prefixed by the letter u or U, the array
4275 elements have type char16_t or char32_t, respectively, and are initialized with the
4276 sequence of wide characters corresponding to the multibyte character sequence, as
4277 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
4278 its type, with an implementation-defined current locale. The value of a string literal
4279 containing a multibyte character or escape sequence not represented in the execution
4280 character set is implementation-defined.
4281 <p><a name="6.4.5p7" href="#6.4.5p7"><small>7</small></a>
4282 It is unspecified whether these arrays are distinct provided their elements have the
4283 appropriate values. If the program attempts to modify such an array, the behavior is
4285 <p><a name="6.4.5p8" href="#6.4.5p8"><small>8</small></a>
4286 EXAMPLE 1 This pair of adjacent character string literals
4290 produces a single character string literal containing the two characters whose values are '\x12' and '3',
4291 because escape sequences are converted into single members of the execution character set just prior to
4292 adjacent string literal concatenation.
4294 <p><a name="6.4.5p9" href="#6.4.5p9"><small>9</small></a>
4295 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
4306 is equivalent to the string literal
4310 Likewise, each of the sequences
4322 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
4323 function (<a href="#7.22.8.1">7.22.8.1</a>), Unicode utilities <a href="#7.28"><uchar.h></a> (<a href="#7.28">7.28</a>).
4326 <p><small><a name="note78" href="#note78">78)</a> A string literal need not be a string (see <a href="#7.1.1">7.1.1</a>), because a null character may be embedded in it by a
4330 <p><small><a href="#Contents">Contents</a></small>
4331 <h4><a name="6.4.6" href="#6.4.6">6.4.6 Punctuators</a></h4>
4333 <p><a name="6.4.6p1" href="#6.4.6p1"><small>1</small></a>
4337 ++ -- & * + - ~ !
4338 / % << >> < > <= >= == != ^ | && ||
4340 = *= /= %= += -= <<= >>= &= ^= |=
4342 <: :> <% %> %: %:%:
4345 <p><a name="6.4.6p2" href="#6.4.6p2"><small>2</small></a>
4346 A punctuator is a symbol that has independent syntactic and semantic significance.
4347 Depending on context, it may specify an operation to be performed (which in turn may
4348 yield a value or a function designator, produce a side effect, or some combination thereof)
4349 in which case it is known as an operator (other forms of operator also exist in some
4350 contexts). An operand is an entity on which an operator acts.
4352 <p><a name="6.4.6p3" href="#6.4.6p3"><small>3</small></a>
4353 In all aspects of the language, the six tokens<sup><a href="#note79"><b>79)</b></a></sup>
4355 <: :> <% %> %: %:%:
4357 behave, respectively, the same as the six tokens
4361 except for their spelling.<sup><a href="#note80"><b>80)</b></a></sup>
4362 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
4363 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
4366 <p><small><a name="note79" href="#note79">79)</a> These tokens are sometimes called ''digraphs''.
4368 <p><small><a name="note80" href="#note80">80)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
4372 <p><small><a href="#Contents">Contents</a></small>
4373 <h4><a name="6.4.7" href="#6.4.7">6.4.7 Header names</a></h4>
4375 <p><a name="6.4.7p1" href="#6.4.7p1"><small>1</small></a>
4378 < h-char-sequence >
4382 h-char-sequence h-char
4384 any member of the source character set except
4385 the new-line character and >
4388 q-char-sequence q-char
4390 any member of the source character set except
4391 the new-line character and "
4394 <p><a name="6.4.7p2" href="#6.4.7p2"><small>2</small></a>
4395 The sequences in both forms of header names are mapped in an implementation-defined
4396 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
4397 <p><a name="6.4.7p3" href="#6.4.7p3"><small>3</small></a>
4398 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
4399 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
4405 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note81"><b>81)</b></a></sup> Header name
4406 preprocessing tokens are recognized only within #include preprocessing directives and
4407 in implementation-defined locations within #pragma directives.<sup><a href="#note82"><b>82)</b></a></sup>
4408 <p><a name="6.4.7p4" href="#6.4.7p4"><small>4</small></a>
4409 EXAMPLE The following sequence of characters:
4412 #include <1/a.h>
4413 #define const.member@$
4415 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
4416 by a { on the left and a } on the right).
4418 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
4419 {#}{include} {<1/a.h>}
4420 {#}{define} {const}{.}{member}{@}{$}
4423 <p><b> Forward references</b>: source file inclusion (<a href="#6.10.2">6.10.2</a>).
4426 <p><small><a name="note81" href="#note81">81)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
4428 <p><small><a name="note82" href="#note82">82)</a> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
4431 <p><small><a href="#Contents">Contents</a></small>
4432 <h4><a name="6.4.8" href="#6.4.8">6.4.8 Preprocessing numbers</a></h4>
4434 <p><a name="6.4.8p1" href="#6.4.8p1"><small>1</small></a>
4440 pp-number identifier-nondigit
4447 <p><b>Description</b>
4448 <p><a name="6.4.8p2" href="#6.4.8p2"><small>2</small></a>
4449 A preprocessing number begins with a digit optionally preceded by a period (.) and may
4450 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
4452 <p><a name="6.4.8p3" href="#6.4.8p3"><small>3</small></a>
4453 Preprocessing number tokens lexically include all floating and integer constant tokens.
4455 <p><a name="6.4.8p4" href="#6.4.8p4"><small>4</small></a>
4456 A preprocessing number does not have type or a value; it acquires both after a successful
4457 conversion (as part of translation phase 7) to a floating constant token or an integer
4463 <p><small><a href="#Contents">Contents</a></small>
4464 <h4><a name="6.4.9" href="#6.4.9">6.4.9 Comments</a></h4>
4465 <p><a name="6.4.9p1" href="#6.4.9p1"><small>1</small></a>
4466 Except within a character constant, a string literal, or a comment, the characters /*
4467 introduce a comment. The contents of such a comment are examined only to identify
4468 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note83"><b>83)</b></a></sup>
4469 <p><a name="6.4.9p2" href="#6.4.9p2"><small>2</small></a>
4470 Except within a character constant, a string literal, or a comment, the characters //
4471 introduce a comment that includes all multibyte characters up to, but not including, the
4472 next new-line character. The contents of such a comment are examined only to identify
4473 multibyte characters and to find the terminating new-line character.
4474 <p><a name="6.4.9p3" href="#6.4.9p3"><small>3</small></a>
4477 "a//b" // four-character string literal
4478 #include "//e" // undefined behavior
4479 // */ // comment, not syntax error
4480 f = g/**//h; // equivalent to f = g / h;
4482 i(); // part of a two-line comment
4484 / j(); // part of a two-line comment
4485 #define glue(x,y) x##y
4486 glue(/,/) k(); // syntax error, not comment
4487 /*//*/ l(); // equivalent to l();
4489 + p; // equivalent to m = n + p;
4498 <p><small><a name="note83" href="#note83">83)</a> Thus, /* ... */ comments do not nest.
4501 <p><small><a href="#Contents">Contents</a></small>
4502 <h3><a name="6.5" href="#6.5">6.5 Expressions</a></h3>
4503 <p><a name="6.5p1" href="#6.5p1"><small>1</small></a>
4504 An expression is a sequence of operators and operands that specifies computation of a
4505 value, or that designates an object or a function, or that generates side effects, or that
4506 performs a combination thereof. The value computations of the operands of an operator
4507 are sequenced before the value computation of the result of the operator.
4508 <p><a name="6.5p2" href="#6.5p2"><small>2</small></a>
4509 If a side effect on a scalar object is unsequenced relative to either a different side effect
4510 on the same scalar object or a value computation using the value of the same scalar
4511 object, the behavior is undefined. If there are multiple allowable orderings of the
4512 subexpressions of an expression, the behavior is undefined if such an unsequenced side
4513 effect occurs in any of the orderings.<sup><a href="#note84"><b>84)</b></a></sup>
4514 <p><a name="6.5p3" href="#6.5p3"><small>3</small></a>
4515 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note85"><b>85)</b></a></sup> Except as specified
4516 later, side effects and value computations of subexpressions are unsequenced.<sup><a href="#note86"><b>86)</b></a></sup>
4517 <p><a name="6.5p4" href="#6.5p4"><small>4</small></a>
4518 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
4519 collectively described as bitwise operators) are required to have operands that have
4520 integer type. These operators yield values that depend on the internal representations of
4521 integers, and have implementation-defined and undefined aspects for signed types.
4522 <p><a name="6.5p5" href="#6.5p5"><small>5</small></a>
4523 If an exceptional condition occurs during the evaluation of an expression (that is, if the
4524 result is not mathematically defined or not in the range of representable values for its
4525 type), the behavior is undefined.
4530 <p><a name="6.5p6" href="#6.5p6"><small>6</small></a>
4531 The effective type of an object for an access to its stored value is the declared type of the
4532 object, if any.<sup><a href="#note87"><b>87)</b></a></sup> If a value is stored into an object having no declared type through an
4533 lvalue having a type that is not a character type, then the type of the lvalue becomes the
4534 effective type of the object for that access and for subsequent accesses that do not modify
4535 the stored value. If a value is copied into an object having no declared type using
4536 memcpy or memmove, or is copied as an array of character type, then the effective type
4537 of the modified object for that access and for subsequent accesses that do not modify the
4538 value is the effective type of the object from which the value is copied, if it has one. For
4539 all other accesses to an object having no declared type, the effective type of the object is
4540 simply the type of the lvalue used for the access.
4541 <p><a name="6.5p7" href="#6.5p7"><small>7</small></a>
4542 An object shall have its stored value accessed only by an lvalue expression that has one of
4543 the following types:<sup><a href="#note88"><b>88)</b></a></sup>
4545 <li> a type compatible with the effective type of the object,
4546 <li> a qualified version of a type compatible with the effective type of the object,
4547 <li> a type that is the signed or unsigned type corresponding to the effective type of the
4549 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
4550 effective type of the object,
4551 <li> an aggregate or union type that includes one of the aforementioned types among its
4552 members (including, recursively, a member of a subaggregate or contained union), or
4553 <li> a character type.
4555 <p><a name="6.5p8" href="#6.5p8"><small>8</small></a>
4556 A floating expression may be contracted, that is, evaluated as though it were a single
4557 operation, thereby omitting rounding errors implied by the source code and the
4558 expression evaluation method.<sup><a href="#note89"><b>89)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
4559 way to disallow contracted expressions. Otherwise, whether and how expressions are
4560 contracted is implementation-defined.<sup><a href="#note90"><b>90)</b></a></sup>
4561 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.24.2">7.24.2</a>).
4567 <p><small><a name="note84" href="#note84">84)</a> This paragraph renders undefined statement expressions such as
4581 <p><small><a name="note85" href="#note85">85)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
4582 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
4583 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
4584 <a href="#6.5.1">6.5.1</a> through <a href="#6.5.6">6.5.6</a>. The exceptions are cast expressions (<a href="#6.5.4">6.5.4</a>) as operands of unary operators
4585 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
4586 parentheses () (<a href="#6.5.1">6.5.1</a>), subscripting brackets [] (<a href="#6.5.2.1">6.5.2.1</a>), function-call parentheses () (<a href="#6.5.2.2">6.5.2.2</a>), and
4587 the conditional operator ? : (<a href="#6.5.15">6.5.15</a>).
4588 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
4589 indicated in each subclause by the syntax for the expressions discussed therein.
4591 <p><small><a name="note86" href="#note86">86)</a> In an expression that is evaluated more than once during the execution of a program, unsequenced and
4592 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
4593 different evaluations.
4595 <p><small><a name="note87" href="#note87">87)</a> Allocated objects have no declared type.
4597 <p><small><a name="note88" href="#note88">88)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
4599 <p><small><a name="note89" href="#note89">89)</a> The intermediate operations in the contracted expression are evaluated as if to infinite range and
4600 precision, while the final operation is rounded to the format determined by the expression evaluation
4601 method. A contracted expression might also omit the raising of floating-point exceptions.
4603 <p><small><a name="note90" href="#note90">90)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
4604 combine multiple C operators. As contractions potentially undermine predictability, and can even
4605 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
4609 <p><small><a href="#Contents">Contents</a></small>
4610 <h4><a name="6.5.1" href="#6.5.1">6.5.1 Primary expressions</a></h4>
4612 <p><a name="6.5.1p1" href="#6.5.1p1"><small>1</small></a>
4622 <p><a name="6.5.1p2" href="#6.5.1p2"><small>2</small></a>
4623 An identifier is a primary expression, provided it has been declared as designating an
4624 object (in which case it is an lvalue) or a function (in which case it is a function
4625 designator).<sup><a href="#note91"><b>91)</b></a></sup>
4626 <p><a name="6.5.1p3" href="#6.5.1p3"><small>3</small></a>
4627 A constant is a primary expression. Its type depends on its form and value, as detailed in
4628 <a href="#6.4.4">6.4.4</a>.
4629 <p><a name="6.5.1p4" href="#6.5.1p4"><small>4</small></a>
4630 A string literal is a primary expression. It is an lvalue with type as detailed in <a href="#6.4.5">6.4.5</a>.
4631 <p><a name="6.5.1p5" href="#6.5.1p5"><small>5</small></a>
4632 A parenthesized expression is a primary expression. Its type and value are identical to
4633 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
4634 expression if the unparenthesized expression is, respectively, an lvalue, a function
4635 designator, or a void expression.
4636 <p><a name="6.5.1p6" href="#6.5.1p6"><small>6</small></a>
4637 A generic selection is a primary expression. Its type and value depend on the selected
4638 generic association, as detailed in the following subclause.
4639 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>).
4642 <p><small><a name="note91" href="#note91">91)</a> Thus, an undeclared identifier is a violation of the syntax.
4645 <p><small><a href="#Contents">Contents</a></small>
4646 <h5><a name="6.5.1.1" href="#6.5.1.1">6.5.1.1 Generic selection</a></h5>
4648 <p><a name="6.5.1.1p1" href="#6.5.1.1p1"><small>1</small></a>
4651 _Generic ( assignment-expression , generic-assoc-list )
4654 generic-assoc-list , generic-association
4655 generic-association:
4656 type-name : assignment-expression
4657 default : assignment-expression
4663 <p><b>Constraints</b>
4664 <p><a name="6.5.1.1p2" href="#6.5.1.1p2"><small>2</small></a>
4665 A generic selection shall have no more than one default generic association. The type
4666 name in a generic association shall specify a complete object type other than a variably
4667 modified type. No two generic associations in the same generic selection shall specify
4668 compatible types. The controlling expression of a generic selection shall have type
4669 compatible with at most one of the types named in its generic association list. If a
4670 generic selection has no default generic association, its controlling expression shall
4671 have type compatible with exactly one of the types named in its generic association list.
4673 <p><a name="6.5.1.1p3" href="#6.5.1.1p3"><small>3</small></a>
4674 The controlling expression of a generic selection is not evaluated. If a generic selection
4675 has a generic association with a type name that is compatible with the type of the
4676 controlling expression, then the result expression of the generic selection is the
4677 expression in that generic association. Otherwise, the result expression of the generic
4678 selection is the expression in the default generic association. None of the expressions
4679 from any other generic association of the generic selection is evaluated.
4680 <p><a name="6.5.1.1p4" href="#6.5.1.1p4"><small>4</small></a>
4681 The type and value of a generic selection are identical to those of its result expression. It
4682 is an lvalue, a function designator, or a void expression if its result expression is,
4683 respectively, an lvalue, a function designator, or a void expression.
4684 <p><a name="6.5.1.1p5" href="#6.5.1.1p5"><small>5</small></a>
4685 EXAMPLE The cbrt type-generic macro could be implemented as follows:
4687 #define cbrt(X) _Generic((X), \
4688 long double: cbrtl, \
4695 <p><small><a href="#Contents">Contents</a></small>
4696 <h4><a name="6.5.2" href="#6.5.2">6.5.2 Postfix operators</a></h4>
4698 <p><a name="6.5.2p1" href="#6.5.2p1"><small>1</small></a>
4703 postfix-expression [ expression ]
4704 postfix-expression ( argument-expression-list<sub>opt</sub> )
4705 postfix-expression . identifier
4706 postfix-expression -> identifier
4707 postfix-expression ++
4708 postfix-expression --
4709 ( type-name ) { initializer-list }
4710 ( type-name ) { initializer-list , }
4711 argument-expression-list:
4712 assignment-expression
4713 argument-expression-list , assignment-expression
4716 <p><small><a href="#Contents">Contents</a></small>
4717 <h5><a name="6.5.2.1" href="#6.5.2.1">6.5.2.1 Array subscripting</a></h5>
4718 <p><b>Constraints</b>
4719 <p><a name="6.5.2.1p1" href="#6.5.2.1p1"><small>1</small></a>
4720 One of the expressions shall have type ''pointer to complete object type'', the other
4721 expression shall have integer type, and the result has type ''type''.
4723 <p><a name="6.5.2.1p2" href="#6.5.2.1p2"><small>2</small></a>
4724 A postfix expression followed by an expression in square brackets [] is a subscripted
4725 designation of an element of an array object. The definition of the subscript operator []
4726 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
4727 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
4728 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
4729 element of E1 (counting from zero).
4730 <p><a name="6.5.2.1p3" href="#6.5.2.1p3"><small>3</small></a>
4731 Successive subscript operators designate an element of a multidimensional array object.
4732 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
4733 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
4734 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
4735 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
4736 array, which itself is converted into a pointer if used as other than an lvalue. It follows
4737 from this that arrays are stored in row-major order (last subscript varies fastest).
4738 <p><a name="6.5.2.1p4" href="#6.5.2.1p4"><small>4</small></a>
4739 EXAMPLE Consider the array object defined by the declaration
4743 Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an
4744 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
4745 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
4746 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
4747 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
4748 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
4751 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
4752 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
4755 <p><small><a href="#Contents">Contents</a></small>
4756 <h5><a name="6.5.2.2" href="#6.5.2.2">6.5.2.2 Function calls</a></h5>
4757 <p><b>Constraints</b>
4758 <p><a name="6.5.2.2p1" href="#6.5.2.2p1"><small>1</small></a>
4759 The expression that denotes the called function<sup><a href="#note92"><b>92)</b></a></sup> shall have type pointer to function
4760 returning void or returning a complete object type other than an array type.
4761 <p><a name="6.5.2.2p2" href="#6.5.2.2p2"><small>2</small></a>
4762 If the expression that denotes the called function has a type that includes a prototype, the
4763 number of arguments shall agree with the number of parameters. Each argument shall
4764 have a type such that its value may be assigned to an object with the unqualified version
4765 of the type of its corresponding parameter.
4767 <p><a name="6.5.2.2p3" href="#6.5.2.2p3"><small>3</small></a>
4768 A postfix expression followed by parentheses () containing a possibly empty, comma-
4769 separated list of expressions is a function call. The postfix expression denotes the called
4770 function. The list of expressions specifies the arguments to the function.
4771 <p><a name="6.5.2.2p4" href="#6.5.2.2p4"><small>4</small></a>
4772 An argument may be an expression of any complete object type. In preparing for the call
4773 to a function, the arguments are evaluated, and each parameter is assigned the value of the
4774 corresponding argument.<sup><a href="#note93"><b>93)</b></a></sup>
4775 <p><a name="6.5.2.2p5" href="#6.5.2.2p5"><small>5</small></a>
4776 If the expression that denotes the called function has type pointer to function returning an
4777 object type, the function call expression has the same type as that object type, and has the
4778 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void.
4779 <p><a name="6.5.2.2p6" href="#6.5.2.2p6"><small>6</small></a>
4780 If the expression that denotes the called function has a type that does not include a
4781 prototype, the integer promotions are performed on each argument, and arguments that
4782 have type float are promoted to double. These are called the default argument
4783 promotions. If the number of arguments does not equal the number of parameters, the
4784 behavior is undefined. If the function is defined with a type that includes a prototype, and
4785 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
4786 promotion are not compatible with the types of the parameters, the behavior is undefined.
4787 If the function is defined with a type that does not include a prototype, and the types of
4788 the arguments after promotion are not compatible with those of the parameters after
4789 promotion, the behavior is undefined, except for the following cases:
4791 <li> one promoted type is a signed integer type, the other promoted type is the
4792 corresponding unsigned integer type, and the value is representable in both types;
4797 <li> both types are pointers to qualified or unqualified versions of a character type or
4800 <p><a name="6.5.2.2p7" href="#6.5.2.2p7"><small>7</small></a>
4801 If the expression that denotes the called function has a type that does include a prototype,
4802 the arguments are implicitly converted, as if by assignment, to the types of the
4803 corresponding parameters, taking the type of each parameter to be the unqualified version
4804 of its declared type. The ellipsis notation in a function prototype declarator causes
4805 argument type conversion to stop after the last declared parameter. The default argument
4806 promotions are performed on trailing arguments.
4807 <p><a name="6.5.2.2p8" href="#6.5.2.2p8"><small>8</small></a>
4808 No other conversions are performed implicitly; in particular, the number and types of
4809 arguments are not compared with those of the parameters in a function definition that
4810 does not include a function prototype declarator.
4811 <p><a name="6.5.2.2p9" href="#6.5.2.2p9"><small>9</small></a>
4812 If the function is defined with a type that is not compatible with the type (of the
4813 expression) pointed to by the expression that denotes the called function, the behavior is
4815 <p><a name="6.5.2.2p10" href="#6.5.2.2p10"><small>10</small></a>
4816 There is a sequence point after the evaluations of the function designator and the actual
4817 arguments but before the actual call. Every evaluation in the calling function (including
4818 other function calls) that is not otherwise specifically sequenced before or after the
4819 execution of the body of the called function is indeterminately sequenced with respect to
4820 the execution of the called function.<sup><a href="#note94"><b>94)</b></a></sup>
4821 <p><a name="6.5.2.2p11" href="#6.5.2.2p11"><small>11</small></a>
4822 Recursive function calls shall be permitted, both directly and indirectly through any chain
4824 <p><a name="6.5.2.2p12" href="#6.5.2.2p12"><small>12</small></a>
4825 EXAMPLE In the function call
4827 (*pf[f1()]) (f2(), f3() + f4())
4829 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
4830 the function pointed to by pf[f1()] is called.
4832 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
4833 definitions (<a href="#6.9.1">6.9.1</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
4836 <p><small><a name="note92" href="#note92">92)</a> Most often, this is the result of converting an identifier that is a function designator.
4838 <p><small><a name="note93" href="#note93">93)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
4839 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
4840 change the value of the object pointed to. A parameter declared to have array or function type is
4841 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
4843 <p><small><a name="note94" href="#note94">94)</a> In other words, function executions do not ''interleave'' with each other.
4846 <p><small><a href="#Contents">Contents</a></small>
4847 <h5><a name="6.5.2.3" href="#6.5.2.3">6.5.2.3 Structure and union members</a></h5>
4848 <p><b>Constraints</b>
4849 <p><a name="6.5.2.3p1" href="#6.5.2.3p1"><small>1</small></a>
4850 The first operand of the . operator shall have an atomic, qualified, or unqualified
4851 structure or union type, and the second operand shall name a member of that type.
4852 <p><a name="6.5.2.3p2" href="#6.5.2.3p2"><small>2</small></a>
4853 The first operand of the -> operator shall have type ''pointer to atomic, qualified, or
4854 unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the
4855 second operand shall name a member of the type pointed to.
4860 <p><a name="6.5.2.3p3" href="#6.5.2.3p3"><small>3</small></a>
4861 A postfix expression followed by the . operator and an identifier designates a member of
4862 a structure or union object. The value is that of the named member,<sup><a href="#note95"><b>95)</b></a></sup> and is an lvalue if
4863 the first expression is an lvalue. If the first expression has qualified type, the result has
4864 the so-qualified version of the type of the designated member.
4865 <p><a name="6.5.2.3p4" href="#6.5.2.3p4"><small>4</small></a>
4866 A postfix expression followed by the -> operator and an identifier designates a member
4867 of a structure or union object. The value is that of the named member of the object to
4868 which the first expression points, and is an lvalue.<sup><a href="#note96"><b>96)</b></a></sup> If the first expression is a pointer to
4869 a qualified type, the result has the so-qualified version of the type of the designated
4871 <p><a name="6.5.2.3p5" href="#6.5.2.3p5"><small>5</small></a>
4872 Accessing a member of an atomic structure or union object results in undefined
4873 behavior.<sup><a href="#note97"><b>97)</b></a></sup>
4874 <p><a name="6.5.2.3p6" href="#6.5.2.3p6"><small>6</small></a>
4875 One special guarantee is made in order to simplify the use of unions: if a union contains
4876 several structures that share a common initial sequence (see below), and if the union
4877 object currently contains one of these structures, it is permitted to inspect the common
4878 initial part of any of them anywhere that a declaration of the completed type of the union
4879 is visible. Two structures share a common initial sequence if corresponding members
4880 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
4882 <p><a name="6.5.2.3p7" href="#6.5.2.3p7"><small>7</small></a>
4883 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
4884 union, f().x is a valid postfix expression but is not an lvalue.
4886 <p><a name="6.5.2.3p8" href="#6.5.2.3p8"><small>8</small></a>
4889 struct s { int i; const int ci; };
4892 volatile struct s vs;
4894 the various members have the types:
4906 vs.ci volatile const int
4909 <p><a name="6.5.2.3p9" href="#6.5.2.3p9"><small>9</small></a>
4910 EXAMPLE 3 The following is a valid fragment:
4926 u.nf.doublenode = <a href="#3.14">3.14</a>;
4928 if (u.n.alltypes == 1)
4929 if (sin(u.nf.doublenode) == 0.0)
4932 The following is not a valid fragment (because the union type is not visible within function f):
4934 struct t1 { int m; };
4935 struct t2 { int m; };
4936 int f(struct t1 *p1, struct t2 *p2)
4938 if (p1->m < 0)
4939 p2->m = -p2->m;
4949 return f(&u.s1, &u.s2);
4953 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4954 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
4958 <p><small><a name="note95" href="#note95">95)</a> If the member used to read the contents of a union object is not the same as the member last used to
4959 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
4960 as an object representation in the new type as described in <a href="#6.2.6">6.2.6</a> (a process sometimes called ''type
4961 punning''). This might be a trap representation.
4963 <p><small><a name="note96" href="#note96">96)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
4964 its operand), the expression (&E)->MOS is the same as E.MOS.
4966 <p><small><a name="note97" href="#note97">97)</a> For example, a data race would occur if access to the entire structure or union in one thread conflicts
4967 with access to a member from another thread, where at least one access is a modification. Members
4968 can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
4971 <p><small><a href="#Contents">Contents</a></small>
4972 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
4973 <p><b>Constraints</b>
4974 <p><a name="6.5.2.4p1" href="#6.5.2.4p1"><small>1</small></a>
4975 The operand of the postfix increment or decrement operator shall have atomic, qualified,
4976 or unqualified real or pointer type, and shall be a modifiable lvalue.
4978 <p><a name="6.5.2.4p2" href="#6.5.2.4p2"><small>2</small></a>
4979 The result of the postfix ++ operator is the value of the operand. As a side effect, the
4980 value of the operand object is incremented (that is, the value 1 of the appropriate type is
4981 added to it). See the discussions of additive operators and compound assignment for
4982 information on constraints, types, and conversions and the effects of operations on
4983 pointers. The value computation of the result is sequenced before the side effect of
4984 updating the stored value of the operand. With respect to an indeterminately-sequenced
4985 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
4986 with atomic type is a read-modify-write operation with memory_order_seq_cst
4987 memory order semantics.<sup><a href="#note98"><b>98)</b></a></sup>
4988 <p><a name="6.5.2.4p3" href="#6.5.2.4p3"><small>3</small></a>
4989 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4990 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4992 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
4995 <p><small><a name="note98" href="#note98">98)</a> Where a pointer to an atomic object can be formed and E has integer type, E++ is equivalent to the
4996 following code sequence where T is the type of E:
5004 } while (!atomic_compare_exchange_strong(addr, &old, new));
5006 with old being the result of the operation.
5007 Special care must be taken if E has floating type; see <a href="#6.5.16.2">6.5.16.2</a>.
5010 <p><small><a href="#Contents">Contents</a></small>
5011 <h5><a name="6.5.2.5" href="#6.5.2.5">6.5.2.5 Compound literals</a></h5>
5012 <p><b>Constraints</b>
5013 <p><a name="6.5.2.5p1" href="#6.5.2.5p1"><small>1</small></a>
5014 The type name shall specify a complete object type or an array of unknown size, but not a
5015 variable length array type.
5016 <p><a name="6.5.2.5p2" href="#6.5.2.5p2"><small>2</small></a>
5017 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
5019 <p><a name="6.5.2.5p3" href="#6.5.2.5p3"><small>3</small></a>
5020 A postfix expression that consists of a parenthesized type name followed by a brace-
5021 enclosed list of initializers is a compound literal. It provides an unnamed object whose
5024 value is given by the initializer list.<sup><a href="#note99"><b>99)</b></a></sup>
5025 <p><a name="6.5.2.5p4" href="#6.5.2.5p4"><small>4</small></a>
5026 If the type name specifies an array of unknown size, the size is determined by the
5027 initializer list as specified in <a href="#6.7.9">6.7.9</a>, and the type of the compound literal is that of the
5028 completed array type. Otherwise (when the type name specifies an object type), the type
5029 of the compound literal is that specified by the type name. In either case, the result is an
5031 <p><a name="6.5.2.5p5" href="#6.5.2.5p5"><small>5</small></a>
5032 The value of the compound literal is that of an unnamed object initialized by the
5033 initializer list. If the compound literal occurs outside the body of a function, the object
5034 has static storage duration; otherwise, it has automatic storage duration associated with
5035 the enclosing block.
5036 <p><a name="6.5.2.5p6" href="#6.5.2.5p6"><small>6</small></a>
5037 All the semantic rules for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.<sup><a href="#note100"><b>100)</b></a></sup>
5038 <p><a name="6.5.2.5p7" href="#6.5.2.5p7"><small>7</small></a>
5039 String literals, and compound literals with const-qualified types, need not designate
5040 distinct objects.<sup><a href="#note101"><b>101)</b></a></sup>
5041 <p><a name="6.5.2.5p8" href="#6.5.2.5p8"><small>8</small></a>
5042 EXAMPLE 1 The file scope definition
5044 int *p = (int []){2, 4};
5046 initializes p to point to the first element of an array of two ints, the first having the value two and the
5047 second, four. The expressions in this compound literal are required to be constant. The unnamed object
5048 has static storage duration.
5050 <p><a name="6.5.2.5p9" href="#6.5.2.5p9"><small>9</small></a>
5051 EXAMPLE 2 In contrast, in
5061 p is assigned the address of the first element of an array of two ints, the first having the value previously
5062 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
5063 unnamed object has automatic storage duration.
5065 <p><a name="6.5.2.5p10" href="#6.5.2.5p10"><small>10</small></a>
5066 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
5067 created using compound literals can be passed to functions without depending on member order:
5069 drawline((struct point){.x=1, .y=1},
5070 (struct point){.x=3, .y=4});
5076 Or, if drawline instead expected pointers to struct point:
5078 drawline(&(struct point){.x=1, .y=1},
5079 &(struct point){.x=3, .y=4});
5082 <p><a name="6.5.2.5p11" href="#6.5.2.5p11"><small>11</small></a>
5083 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
5085 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
5088 <p><a name="6.5.2.5p12" href="#6.5.2.5p12"><small>12</small></a>
5089 EXAMPLE 5 The following three expressions have different meanings:
5092 (char []){"/tmp/fileXXXXXX"}
5093 (const char []){"/tmp/fileXXXXXX"}
5095 The first always has static storage duration and has type array of char, but need not be modifiable; the last
5096 two have automatic storage duration when they occur within the body of a function, and the first of these
5099 <p><a name="6.5.2.5p13" href="#6.5.2.5p13"><small>13</small></a>
5100 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
5101 and can even be shared. For example,
5103 (const char []){"abc"} == "abc"
5105 might yield 1 if the literals' storage is shared.
5107 <p><a name="6.5.2.5p14" href="#6.5.2.5p14"><small>14</small></a>
5108 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
5109 linked object. For example, there is no way to write a self-referential compound literal that could be used
5110 as the function argument in place of the named object endless_zeros below:
5112 struct int_list { int car; struct int_list *cdr; };
5113 struct int_list endless_zeros = {0, &endless_zeros};
5114 eval(endless_zeros);
5117 <p><a name="6.5.2.5p15" href="#6.5.2.5p15"><small>15</small></a>
5118 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
5120 struct s { int i; };
5123 struct s *p = 0, *q;
5126 q = p, p = &((struct s){ j++ });
5127 if (j < 2) goto again;
5128 return p == q && q->i == 1;
5131 The function f() always returns the value 1.
5132 <p><a name="6.5.2.5p16" href="#6.5.2.5p16"><small>16</small></a>
5133 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
5134 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
5135 have an indeterminate value, which would result in undefined behavior.
5137 <p><b> Forward references</b>: type names (<a href="#6.7.7">6.7.7</a>), initialization (<a href="#6.7.9">6.7.9</a>).
5141 <p><small><a name="note99" href="#note99">99)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
5142 or void only, and the result of a cast expression is not an lvalue.
5144 <p><small><a name="note100" href="#note100">100)</a> For example, subobjects without explicit initializers are initialized to zero.
5146 <p><small><a name="note101" href="#note101">101)</a> This allows implementations to share storage for string literals and constant compound literals with
5147 the same or overlapping representations.
5150 <p><small><a href="#Contents">Contents</a></small>
5151 <h4><a name="6.5.3" href="#6.5.3">6.5.3 Unary operators</a></h4>
5153 <p><a name="6.5.3p1" href="#6.5.3p1"><small>1</small></a>
5159 unary-operator cast-expression
5160 sizeof unary-expression
5161 sizeof ( type-name )
5162 _Alignof ( type-name )
5163 unary-operator: one of
5167 <p><small><a href="#Contents">Contents</a></small>
5168 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
5169 <p><b>Constraints</b>
5170 <p><a name="6.5.3.1p1" href="#6.5.3.1p1"><small>1</small></a>
5171 The operand of the prefix increment or decrement operator shall have atomic, qualified,
5172 or unqualified real or pointer type, and shall be a modifiable lvalue.
5174 <p><a name="6.5.3.1p2" href="#6.5.3.1p2"><small>2</small></a>
5175 The value of the operand of the prefix ++ operator is incremented. The result is the new
5176 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
5177 See the discussions of additive operators and compound assignment for information on
5178 constraints, types, side effects, and conversions and the effects of operations on pointers.
5179 <p><a name="6.5.3.1p3" href="#6.5.3.1p3"><small>3</small></a>
5180 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
5181 operand is decremented.
5182 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
5184 <p><small><a href="#Contents">Contents</a></small>
5185 <h5><a name="6.5.3.2" href="#6.5.3.2">6.5.3.2 Address and indirection operators</a></h5>
5186 <p><b>Constraints</b>
5187 <p><a name="6.5.3.2p1" href="#6.5.3.2p1"><small>1</small></a>
5188 The operand of the unary & operator shall be either a function designator, the result of a
5189 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
5190 not declared with the register storage-class specifier.
5191 <p><a name="6.5.3.2p2" href="#6.5.3.2p2"><small>2</small></a>
5192 The operand of the unary * operator shall have pointer type.
5194 <p><a name="6.5.3.2p3" href="#6.5.3.2p3"><small>3</small></a>
5195 The unary & operator yields the address of its operand. If the operand has type ''type'',
5196 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
5197 neither that operator nor the & operator is evaluated and the result is as if both were
5198 omitted, except that the constraints on the operators still apply and the result is not an
5200 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
5201 the unary * that is implied by the [] is evaluated and the result is as if the & operator
5202 were removed and the [] operator were changed to a + operator. Otherwise, the result is
5203 a pointer to the object or function designated by its operand.
5204 <p><a name="6.5.3.2p4" href="#6.5.3.2p4"><small>4</small></a>
5205 The unary * operator denotes indirection. If the operand points to a function, the result is
5206 a function designator; if it points to an object, the result is an lvalue designating the
5207 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
5208 invalid value has been assigned to the pointer, the behavior of the unary * operator is
5209 undefined.<sup><a href="#note102"><b>102)</b></a></sup>
5210 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
5211 (<a href="#6.7.2.1">6.7.2.1</a>).
5214 <p><small><a name="note102" href="#note102">102)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
5215 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
5216 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
5217 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
5218 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
5219 address inappropriately aligned for the type of object pointed to, and the address of an object after the
5220 end of its lifetime.
5223 <p><small><a href="#Contents">Contents</a></small>
5224 <h5><a name="6.5.3.3" href="#6.5.3.3">6.5.3.3 Unary arithmetic operators</a></h5>
5225 <p><b>Constraints</b>
5226 <p><a name="6.5.3.3p1" href="#6.5.3.3p1"><small>1</small></a>
5227 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
5228 integer type; of the ! operator, scalar type.
5230 <p><a name="6.5.3.3p2" href="#6.5.3.3p2"><small>2</small></a>
5231 The result of the unary + operator is the value of its (promoted) operand. The integer
5232 promotions are performed on the operand, and the result has the promoted type.
5233 <p><a name="6.5.3.3p3" href="#6.5.3.3p3"><small>3</small></a>
5234 The result of the unary - operator is the negative of its (promoted) operand. The integer
5235 promotions are performed on the operand, and the result has the promoted type.
5236 <p><a name="6.5.3.3p4" href="#6.5.3.3p4"><small>4</small></a>
5237 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
5238 each bit in the result is set if and only if the corresponding bit in the converted operand is
5239 not set). The integer promotions are performed on the operand, and the result has the
5240 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
5241 to the maximum value representable in that type minus E.
5242 <p><a name="6.5.3.3p5" href="#6.5.3.3p5"><small>5</small></a>
5243 The result of the logical negation operator ! is 0 if the value of its operand compares
5244 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
5245 The expression !E is equivalent to (0==E).
5251 <p><small><a href="#Contents">Contents</a></small>
5252 <h5><a name="6.5.3.4" href="#6.5.3.4">6.5.3.4 The sizeof and _Alignof operators</a></h5>
5253 <p><b>Constraints</b>
5254 <p><a name="6.5.3.4p1" href="#6.5.3.4p1"><small>1</small></a>
5255 The sizeof operator shall not be applied to an expression that has function type or an
5256 incomplete type, to the parenthesized name of such a type, or to an expression that
5257 designates a bit-field member. The _Alignof operator shall not be applied to a
5258 function type or an incomplete type.
5260 <p><a name="6.5.3.4p2" href="#6.5.3.4p2"><small>2</small></a>
5261 The sizeof operator yields the size (in bytes) of its operand, which may be an
5262 expression or the parenthesized name of a type. The size is determined from the type of
5263 the operand. The result is an integer. If the type of the operand is a variable length array
5264 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
5266 <p><a name="6.5.3.4p3" href="#6.5.3.4p3"><small>3</small></a>
5267 The _Alignof operator yields the alignment requirement of its operand type. The
5268 operand is not evaluated and the result is an integer constant. When applied to an array
5269 type, the result is the alignment requirement of the element type.
5270 <p><a name="6.5.3.4p4" href="#6.5.3.4p4"><small>4</small></a>
5271 When sizeof is applied to an operand that has type char, unsigned char, or
5272 signed char, (or a qualified version thereof) the result is 1. When applied to an
5273 operand that has array type, the result is the total number of bytes in the array.<sup><a href="#note103"><b>103)</b></a></sup> When
5274 applied to an operand that has structure or union type, the result is the total number of
5275 bytes in such an object, including internal and trailing padding.
5276 <p><a name="6.5.3.4p5" href="#6.5.3.4p5"><small>5</small></a>
5277 The value of the result of both operators is implementation-defined, and its type (an
5278 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
5279 <p><a name="6.5.3.4p6" href="#6.5.3.4p6"><small>6</small></a>
5280 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
5281 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
5282 allocate and return a pointer to void. For example:
5284 extern void *alloc(size_t);
5285 double *dp = alloc(sizeof *dp);
5287 The implementation of the alloc function should ensure that its return value is aligned suitably for
5288 conversion to a pointer to double.
5290 <p><a name="6.5.3.4p7" href="#6.5.3.4p7"><small>7</small></a>
5291 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
5293 sizeof array / sizeof array[0]
5296 <p><a name="6.5.3.4p8" href="#6.5.3.4p8"><small>8</small></a>
5297 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
5300 #include <a href="#7.19"><stddef.h></a>
5307 size_t fsize3(int n)
5309 char b[n+3]; // variable length array
5310 return sizeof b; // execution time sizeof
5315 size = fsize3(10); // fsize3 returns 13
5320 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), declarations (<a href="#6.7">6.7</a>),
5321 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.7">6.7.7</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
5324 <p><small><a name="note103" href="#note103">103)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
5325 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
5328 <p><small><a href="#Contents">Contents</a></small>
5329 <h4><a name="6.5.4" href="#6.5.4">6.5.4 Cast operators</a></h4>
5331 <p><a name="6.5.4p1" href="#6.5.4p1"><small>1</small></a>
5335 ( type-name ) cast-expression
5337 <p><b>Constraints</b>
5338 <p><a name="6.5.4p2" href="#6.5.4p2"><small>2</small></a>
5339 Unless the type name specifies a void type, the type name shall specify atomic, qualified,
5340 or unqualified scalar type, and the operand shall have scalar type.
5341 <p><a name="6.5.4p3" href="#6.5.4p3"><small>3</small></a>
5342 Conversions that involve pointers, other than where permitted by the constraints of
5343 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
5344 <p><a name="6.5.4p4" href="#6.5.4p4"><small>4</small></a>
5345 A pointer type shall not be converted to any floating type. A floating type shall not be
5346 converted to any pointer type.
5348 <p><a name="6.5.4p5" href="#6.5.4p5"><small>5</small></a>
5349 Preceding an expression by a parenthesized type name converts the value of the
5350 expression to the named type. This construction is called a cast.<sup><a href="#note104"><b>104)</b></a></sup> A cast that specifies
5351 no conversion has no effect on the type or value of an expression.
5352 <p><a name="6.5.4p6" href="#6.5.4p6"><small>6</small></a>
5353 If the value of the expression is represented with greater range or precision than required
5354 by the type named by the cast (<a href="#6.3.1.8">6.3.1.8</a>), then the cast specifies a conversion even if the
5355 type of the expression is the same as the named type and removes any extra range and
5357 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
5358 prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
5363 <p><small><a name="note104" href="#note104">104)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
5364 unqualified version of the type.
5367 <p><small><a href="#Contents">Contents</a></small>
5368 <h4><a name="6.5.5" href="#6.5.5">6.5.5 Multiplicative operators</a></h4>
5370 <p><a name="6.5.5p1" href="#6.5.5p1"><small>1</small></a>
5372 multiplicative-expression:
5374 multiplicative-expression * cast-expression
5375 multiplicative-expression / cast-expression
5376 multiplicative-expression % cast-expression
5378 <p><b>Constraints</b>
5379 <p><a name="6.5.5p2" href="#6.5.5p2"><small>2</small></a>
5380 Each of the operands shall have arithmetic type. The operands of the % operator shall
5383 <p><a name="6.5.5p3" href="#6.5.5p3"><small>3</small></a>
5384 The usual arithmetic conversions are performed on the operands.
5385 <p><a name="6.5.5p4" href="#6.5.5p4"><small>4</small></a>
5386 The result of the binary * operator is the product of the operands.
5387 <p><a name="6.5.5p5" href="#6.5.5p5"><small>5</small></a>
5388 The result of the / operator is the quotient from the division of the first operand by the
5389 second; the result of the % operator is the remainder. In both operations, if the value of
5390 the second operand is zero, the behavior is undefined.
5391 <p><a name="6.5.5p6" href="#6.5.5p6"><small>6</small></a>
5392 When integers are divided, the result of the / operator is the algebraic quotient with any
5393 fractional part discarded.<sup><a href="#note105"><b>105)</b></a></sup> If the quotient a/b is representable, the expression
5394 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
5398 <p><small><a name="note105" href="#note105">105)</a> This is often called ''truncation toward zero''.
5401 <p><small><a href="#Contents">Contents</a></small>
5402 <h4><a name="6.5.6" href="#6.5.6">6.5.6 Additive operators</a></h4>
5404 <p><a name="6.5.6p1" href="#6.5.6p1"><small>1</small></a>
5406 additive-expression:
5407 multiplicative-expression
5408 additive-expression + multiplicative-expression
5409 additive-expression - multiplicative-expression
5411 <p><b>Constraints</b>
5412 <p><a name="6.5.6p2" href="#6.5.6p2"><small>2</small></a>
5413 For addition, either both operands shall have arithmetic type, or one operand shall be a
5414 pointer to a complete object type and the other shall have integer type. (Incrementing is
5415 equivalent to adding 1.)
5416 <p><a name="6.5.6p3" href="#6.5.6p3"><small>3</small></a>
5417 For subtraction, one of the following shall hold:
5424 <li> both operands have arithmetic type;
5425 <li> both operands are pointers to qualified or unqualified versions of compatible complete
5427 <li> the left operand is a pointer to a complete object type and the right operand has
5430 (Decrementing is equivalent to subtracting 1.)
5432 <p><a name="6.5.6p4" href="#6.5.6p4"><small>4</small></a>
5433 If both operands have arithmetic type, the usual arithmetic conversions are performed on
5435 <p><a name="6.5.6p5" href="#6.5.6p5"><small>5</small></a>
5436 The result of the binary + operator is the sum of the operands.
5437 <p><a name="6.5.6p6" href="#6.5.6p6"><small>6</small></a>
5438 The result of the binary - operator is the difference resulting from the subtraction of the
5439 second operand from the first.
5440 <p><a name="6.5.6p7" href="#6.5.6p7"><small>7</small></a>
5441 For the purposes of these operators, a pointer to an object that is not an element of an
5442 array behaves the same as a pointer to the first element of an array of length one with the
5443 type of the object as its element type.
5444 <p><a name="6.5.6p8" href="#6.5.6p8"><small>8</small></a>
5445 When an expression that has integer type is added to or subtracted from a pointer, the
5446 result has the type of the pointer operand. If the pointer operand points to an element of
5447 an array object, and the array is large enough, the result points to an element offset from
5448 the original element such that the difference of the subscripts of the resulting and original
5449 array elements equals the integer expression. In other words, if the expression P points to
5450 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
5451 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
5452 the array object, provided they exist. Moreover, if the expression P points to the last
5453 element of an array object, the expression (P)+1 points one past the last element of the
5454 array object, and if the expression Q points one past the last element of an array object,
5455 the expression (Q)-1 points to the last element of the array object. If both the pointer
5456 operand and the result point to elements of the same array object, or one past the last
5457 element of the array object, the evaluation shall not produce an overflow; otherwise, the
5458 behavior is undefined. If the result points one past the last element of the array object, it
5459 shall not be used as the operand of a unary * operator that is evaluated.
5460 <p><a name="6.5.6p9" href="#6.5.6p9"><small>9</small></a>
5461 When two pointers are subtracted, both shall point to elements of the same array object,
5462 or one past the last element of the array object; the result is the difference of the
5463 subscripts of the two array elements. The size of the result is implementation-defined,
5464 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
5465 If the result is not representable in an object of that type, the behavior is undefined. In
5466 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
5467 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
5469 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
5470 an array object or one past the last element of an array object, and the expression Q points
5471 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
5472 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
5473 expression P points one past the last element of the array object, even though the
5474 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note106"><b>106)</b></a></sup>
5475 <p><a name="6.5.6p10" href="#6.5.6p10"><small>10</small></a>
5476 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
5481 int (*p)[m] = a; // p == &a[0]
5482 p += 1; // p == &a[1]
5483 (*p)[2] = 99; // a[1][2] == 99
5484 n = p - a; // n == 1
5487 <p><a name="6.5.6p11" href="#6.5.6p11"><small>11</small></a>
5488 If array a in the above example were declared to be an array of known constant size, and pointer p were
5489 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
5492 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), common definitions <a href="#7.19"><stddef.h></a>
5493 (<a href="#7.19">7.19</a>).
5496 <p><small><a name="note106" href="#note106">106)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
5497 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
5498 by the size of the object originally pointed to, and the resulting pointer is converted back to the
5499 original type. For pointer subtraction, the result of the difference between the character pointers is
5500 similarly divided by the size of the object originally pointed to.
5501 When viewed in this way, an implementation need only provide one extra byte (which may overlap
5502 another object in the program) just after the end of the object in order to satisfy the ''one past the last
5503 element'' requirements.
5506 <p><small><a href="#Contents">Contents</a></small>
5507 <h4><a name="6.5.7" href="#6.5.7">6.5.7 Bitwise shift operators</a></h4>
5509 <p><a name="6.5.7p1" href="#6.5.7p1"><small>1</small></a>
5513 shift-expression << additive-expression
5514 shift-expression >> additive-expression
5516 <p><b>Constraints</b>
5517 <p><a name="6.5.7p2" href="#6.5.7p2"><small>2</small></a>
5518 Each of the operands shall have integer type.
5520 <p><a name="6.5.7p3" href="#6.5.7p3"><small>3</small></a>
5521 The integer promotions are performed on each of the operands. The type of the result is
5522 that of the promoted left operand. If the value of the right operand is negative or is
5525 greater than or equal to the width of the promoted left operand, the behavior is undefined.
5526 <p><a name="6.5.7p4" href="#6.5.7p4"><small>4</small></a>
5527 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
5528 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
5529 one more than the maximum value representable in the result type. If E1 has a signed
5530 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
5531 the resulting value; otherwise, the behavior is undefined.
5532 <p><a name="6.5.7p5" href="#6.5.7p5"><small>5</small></a>
5533 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
5534 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
5535 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
5536 resulting value is implementation-defined.
5538 <p><small><a href="#Contents">Contents</a></small>
5539 <h4><a name="6.5.8" href="#6.5.8">6.5.8 Relational operators</a></h4>
5541 <p><a name="6.5.8p1" href="#6.5.8p1"><small>1</small></a>
5543 relational-expression:
5545 relational-expression < shift-expression
5546 relational-expression > shift-expression
5547 relational-expression <= shift-expression
5548 relational-expression >= shift-expression
5550 <p><b>Constraints</b>
5551 <p><a name="6.5.8p2" href="#6.5.8p2"><small>2</small></a>
5552 One of the following shall hold:
5554 <li> both operands have real type; or
5555 <li> both operands are pointers to qualified or unqualified versions of compatible object
5559 <p><a name="6.5.8p3" href="#6.5.8p3"><small>3</small></a>
5560 If both of the operands have arithmetic type, the usual arithmetic conversions are
5562 <p><a name="6.5.8p4" href="#6.5.8p4"><small>4</small></a>
5563 For the purposes of these operators, a pointer to an object that is not an element of an
5564 array behaves the same as a pointer to the first element of an array of length one with the
5565 type of the object as its element type.
5566 <p><a name="6.5.8p5" href="#6.5.8p5"><small>5</small></a>
5567 When two pointers are compared, the result depends on the relative locations in the
5568 address space of the objects pointed to. If two pointers to object types both point to the
5569 same object, or both point one past the last element of the same array object, they
5570 compare equal. If the objects pointed to are members of the same aggregate object,
5571 pointers to structure members declared later compare greater than pointers to members
5572 declared earlier in the structure, and pointers to array elements with larger subscript
5573 values compare greater than pointers to elements of the same array with lower subscript
5575 values. All pointers to members of the same union object compare equal. If the
5576 expression P points to an element of an array object and the expression Q points to the
5577 last element of the same array object, the pointer expression Q+1 compares greater than
5578 P. In all other cases, the behavior is undefined.
5579 <p><a name="6.5.8p6" href="#6.5.8p6"><small>6</small></a>
5580 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
5581 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
5582 false.<sup><a href="#note107"><b>107)</b></a></sup> The result has type int.
5585 <p><small><a name="note107" href="#note107">107)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
5586 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
5589 <p><small><a href="#Contents">Contents</a></small>
5590 <h4><a name="6.5.9" href="#6.5.9">6.5.9 Equality operators</a></h4>
5592 <p><a name="6.5.9p1" href="#6.5.9p1"><small>1</small></a>
5594 equality-expression:
5595 relational-expression
5596 equality-expression == relational-expression
5597 equality-expression != relational-expression
5599 <p><b>Constraints</b>
5600 <p><a name="6.5.9p2" href="#6.5.9p2"><small>2</small></a>
5601 One of the following shall hold:
5603 <li> both operands have arithmetic type;
5604 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5605 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5606 unqualified version of void; or
5607 <li> one operand is a pointer and the other is a null pointer constant.
5610 <p><a name="6.5.9p3" href="#6.5.9p3"><small>3</small></a>
5611 The == (equal to) and != (not equal to) operators are analogous to the relational
5612 operators except for their lower precedence.<sup><a href="#note108"><b>108)</b></a></sup> Each of the operators yields 1 if the
5613 specified relation is true and 0 if it is false. The result has type int. For any pair of
5614 operands, exactly one of the relations is true.
5615 <p><a name="6.5.9p4" href="#6.5.9p4"><small>4</small></a>
5616 If both of the operands have arithmetic type, the usual arithmetic conversions are
5617 performed. Values of complex types are equal if and only if both their real parts are equal
5618 and also their imaginary parts are equal. Any two values of arithmetic types from
5619 different type domains are equal if and only if the results of their conversions to the
5620 (complex) result type determined by the usual arithmetic conversions are equal.
5625 <p><a name="6.5.9p5" href="#6.5.9p5"><small>5</small></a>
5626 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
5627 null pointer constant, the null pointer constant is converted to the type of the pointer. If
5628 one operand is a pointer to an object type and the other is a pointer to a qualified or
5629 unqualified version of void, the former is converted to the type of the latter.
5630 <p><a name="6.5.9p6" href="#6.5.9p6"><small>6</small></a>
5631 Two pointers compare equal if and only if both are null pointers, both are pointers to the
5632 same object (including a pointer to an object and a subobject at its beginning) or function,
5633 both are pointers to one past the last element of the same array object, or one is a pointer
5634 to one past the end of one array object and the other is a pointer to the start of a different
5635 array object that happens to immediately follow the first array object in the address
5636 space.<sup><a href="#note109"><b>109)</b></a></sup>
5637 <p><a name="6.5.9p7" href="#6.5.9p7"><small>7</small></a>
5638 For the purposes of these operators, a pointer to an object that is not an element of an
5639 array behaves the same as a pointer to the first element of an array of length one with the
5640 type of the object as its element type.
5643 <p><small><a name="note108" href="#note108">108)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
5645 <p><small><a name="note109" href="#note109">109)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
5646 adjacent members of a structure with no padding between them, or because the implementation chose
5647 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
5648 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
5652 <p><small><a href="#Contents">Contents</a></small>
5653 <h4><a name="6.5.10" href="#6.5.10">6.5.10 Bitwise AND operator</a></h4>
5655 <p><a name="6.5.10p1" href="#6.5.10p1"><small>1</small></a>
5659 AND-expression & equality-expression
5661 <p><b>Constraints</b>
5662 <p><a name="6.5.10p2" href="#6.5.10p2"><small>2</small></a>
5663 Each of the operands shall have integer type.
5665 <p><a name="6.5.10p3" href="#6.5.10p3"><small>3</small></a>
5666 The usual arithmetic conversions are performed on the operands.
5667 <p><a name="6.5.10p4" href="#6.5.10p4"><small>4</small></a>
5668 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
5669 the result is set if and only if each of the corresponding bits in the converted operands is
5677 <p><small><a href="#Contents">Contents</a></small>
5678 <h4><a name="6.5.11" href="#6.5.11">6.5.11 Bitwise exclusive OR operator</a></h4>
5680 <p><a name="6.5.11p1" href="#6.5.11p1"><small>1</small></a>
5682 exclusive-OR-expression:
5684 exclusive-OR-expression ^ AND-expression
5686 <p><b>Constraints</b>
5687 <p><a name="6.5.11p2" href="#6.5.11p2"><small>2</small></a>
5688 Each of the operands shall have integer type.
5690 <p><a name="6.5.11p3" href="#6.5.11p3"><small>3</small></a>
5691 The usual arithmetic conversions are performed on the operands.
5692 <p><a name="6.5.11p4" href="#6.5.11p4"><small>4</small></a>
5693 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
5694 in the result is set if and only if exactly one of the corresponding bits in the converted
5697 <p><small><a href="#Contents">Contents</a></small>
5698 <h4><a name="6.5.12" href="#6.5.12">6.5.12 Bitwise inclusive OR operator</a></h4>
5700 <p><a name="6.5.12p1" href="#6.5.12p1"><small>1</small></a>
5702 inclusive-OR-expression:
5703 exclusive-OR-expression
5704 inclusive-OR-expression | exclusive-OR-expression
5706 <p><b>Constraints</b>
5707 <p><a name="6.5.12p2" href="#6.5.12p2"><small>2</small></a>
5708 Each of the operands shall have integer type.
5710 <p><a name="6.5.12p3" href="#6.5.12p3"><small>3</small></a>
5711 The usual arithmetic conversions are performed on the operands.
5712 <p><a name="6.5.12p4" href="#6.5.12p4"><small>4</small></a>
5713 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
5714 the result is set if and only if at least one of the corresponding bits in the converted
5718 <p><small><a href="#Contents">Contents</a></small>
5719 <h4><a name="6.5.13" href="#6.5.13">6.5.13 Logical AND operator</a></h4>
5721 <p><a name="6.5.13p1" href="#6.5.13p1"><small>1</small></a>
5723 logical-AND-expression:
5724 inclusive-OR-expression
5725 logical-AND-expression && inclusive-OR-expression
5727 <p><b>Constraints</b>
5728 <p><a name="6.5.13p2" href="#6.5.13p2"><small>2</small></a>
5729 Each of the operands shall have scalar type.
5731 <p><a name="6.5.13p3" href="#6.5.13p3"><small>3</small></a>
5732 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
5733 yields 0. The result has type int.
5734 <p><a name="6.5.13p4" href="#6.5.13p4"><small>4</small></a>
5735 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
5736 if the second operand is evaluated, there is a sequence point between the evaluations of
5737 the first and second operands. If the first operand compares equal to 0, the second
5738 operand is not evaluated.
5740 <p><small><a href="#Contents">Contents</a></small>
5741 <h4><a name="6.5.14" href="#6.5.14">6.5.14 Logical OR operator</a></h4>
5743 <p><a name="6.5.14p1" href="#6.5.14p1"><small>1</small></a>
5745 logical-OR-expression:
5746 logical-AND-expression
5747 logical-OR-expression || logical-AND-expression
5749 <p><b>Constraints</b>
5750 <p><a name="6.5.14p2" href="#6.5.14p2"><small>2</small></a>
5751 Each of the operands shall have scalar type.
5753 <p><a name="6.5.14p3" href="#6.5.14p3"><small>3</small></a>
5754 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
5755 yields 0. The result has type int.
5756 <p><a name="6.5.14p4" href="#6.5.14p4"><small>4</small></a>
5757 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
5758 second operand is evaluated, there is a sequence point between the evaluations of the first
5759 and second operands. If the first operand compares unequal to 0, the second operand is
5763 <p><small><a href="#Contents">Contents</a></small>
5764 <h4><a name="6.5.15" href="#6.5.15">6.5.15 Conditional operator</a></h4>
5766 <p><a name="6.5.15p1" href="#6.5.15p1"><small>1</small></a>
5768 conditional-expression:
5769 logical-OR-expression
5770 logical-OR-expression ? expression : conditional-expression
5772 <p><b>Constraints</b>
5773 <p><a name="6.5.15p2" href="#6.5.15p2"><small>2</small></a>
5774 The first operand shall have scalar type.
5775 <p><a name="6.5.15p3" href="#6.5.15p3"><small>3</small></a>
5776 One of the following shall hold for the second and third operands:
5778 <li> both operands have arithmetic type;
5779 <li> both operands have the same structure or union type;
5780 <li> both operands have void type;
5781 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5782 <li> one operand is a pointer and the other is a null pointer constant; or
5783 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5784 unqualified version of void.
5787 <p><a name="6.5.15p4" href="#6.5.15p4"><small>4</small></a>
5788 The first operand is evaluated; there is a sequence point between its evaluation and the
5789 evaluation of the second or third operand (whichever is evaluated). The second operand
5790 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
5791 the first compares equal to 0; the result is the value of the second or third operand
5792 (whichever is evaluated), converted to the type described below.<sup><a href="#note110"><b>110)</b></a></sup>
5793 <p><a name="6.5.15p5" href="#6.5.15p5"><small>5</small></a>
5794 If both the second and third operands have arithmetic type, the result type that would be
5795 determined by the usual arithmetic conversions, were they applied to those two operands,
5796 is the type of the result. If both the operands have structure or union type, the result has
5797 that type. If both operands have void type, the result has void type.
5798 <p><a name="6.5.15p6" href="#6.5.15p6"><small>6</small></a>
5799 If both the second and third operands are pointers or one is a null pointer constant and the
5800 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
5801 of the types referenced by both operands. Furthermore, if both operands are pointers to
5802 compatible types or to differently qualified versions of compatible types, the result type is
5803 a pointer to an appropriately qualified version of the composite type; if one operand is a
5804 null pointer constant, the result has the type of the other operand; otherwise, one operand
5805 is a pointer to void or a qualified version of void, in which case the result type is a
5806 pointer to an appropriately qualified version of void.
5809 <p><a name="6.5.15p7" href="#6.5.15p7"><small>7</small></a>
5810 EXAMPLE The common type that results when the second and third operands are pointers is determined
5811 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
5812 pointers have compatible types.
5813 <p><a name="6.5.15p8" href="#6.5.15p8"><small>8</small></a>
5814 Given the declarations
5823 the third column in the following table is the common type that is the result of a conditional expression in
5824 which the first two columns are the second and third operands (in either order):
5826 c_vp c_ip const void *
5827 v_ip 0 volatile int *
5828 c_ip v_ip const volatile int *
5829 vp c_cp const void *
5836 <p><small><a name="note110" href="#note110">110)</a> A conditional expression does not yield an lvalue.
5839 <p><small><a href="#Contents">Contents</a></small>
5840 <h4><a name="6.5.16" href="#6.5.16">6.5.16 Assignment operators</a></h4>
5842 <p><a name="6.5.16p1" href="#6.5.16p1"><small>1</small></a>
5844 assignment-expression:
5845 conditional-expression
5846 unary-expression assignment-operator assignment-expression
5847 assignment-operator: one of
5848 = *= /= %= += -= <<= >>= &= ^= |=
5850 <p><b>Constraints</b>
5851 <p><a name="6.5.16p2" href="#6.5.16p2"><small>2</small></a>
5852 An assignment operator shall have a modifiable lvalue as its left operand.
5854 <p><a name="6.5.16p3" href="#6.5.16p3"><small>3</small></a>
5855 An assignment operator stores a value in the object designated by the left operand. An
5856 assignment expression has the value of the left operand after the assignment,<sup><a href="#note111"><b>111)</b></a></sup> but is not
5857 an lvalue. The type of an assignment expression is the type the left operand would have
5858 after lvalue conversion. The side effect of updating the stored value of the left operand is
5859 sequenced after the value computations of the left and right operands. The evaluations of
5860 the operands are unsequenced.
5868 <p><small><a name="note111" href="#note111">111)</a> The implementation is permitted to read the object to determine the value but is not required to, even
5869 when the object has volatile-qualified type.
5872 <p><small><a href="#Contents">Contents</a></small>
5873 <h5><a name="6.5.16.1" href="#6.5.16.1">6.5.16.1 Simple assignment</a></h5>
5874 <p><b>Constraints</b>
5875 <p><a name="6.5.16.1p1" href="#6.5.16.1p1"><small>1</small></a>
5876 One of the following shall hold:<sup><a href="#note112"><b>112)</b></a></sup>
5878 <li> the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
5880 <li> the left operand has an atomic, qualified, or unqualified version of a structure or union
5881 type compatible with the type of the right;
5882 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5883 the type the left operand would have after lvalue conversion) both operands are
5884 pointers to qualified or unqualified versions of compatible types, and the type pointed
5885 to by the left has all the qualifiers of the type pointed to by the right;
5886 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5887 the type the left operand would have after lvalue conversion) one operand is a pointer
5888 to an object type, and the other is a pointer to a qualified or unqualified version of
5889 void, and the type pointed to by the left has all the qualifiers of the type pointed to
5891 <li> the left operand is an atomic, qualified, or unqualified pointer, and the right is a null
5892 pointer constant; or
5893 <li> the left operand has type atomic, qualified, or unqualified _Bool, and the right is a
5897 <p><a name="6.5.16.1p2" href="#6.5.16.1p2"><small>2</small></a>
5898 In simple assignment (=), the value of the right operand is converted to the type of the
5899 assignment expression and replaces the value stored in the object designated by the left
5901 <p><a name="6.5.16.1p3" href="#6.5.16.1p3"><small>3</small></a>
5902 If the value being stored in an object is read from another object that overlaps in any way
5903 the storage of the first object, then the overlap shall be exact and the two objects shall
5904 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
5906 <p><a name="6.5.16.1p4" href="#6.5.16.1p4"><small>4</small></a>
5907 EXAMPLE 1 In the program fragment
5917 if ((c = f()) == -1)
5920 the int value returned by the function may be truncated when stored in the char, and then converted back
5921 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
5922 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
5923 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
5924 variable c should be declared as int.
5926 <p><a name="6.5.16.1p5" href="#6.5.16.1p5"><small>5</small></a>
5927 EXAMPLE 2 In the fragment:
5934 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
5935 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
5936 that is, long int type.
5938 <p><a name="6.5.16.1p6" href="#6.5.16.1p6"><small>6</small></a>
5939 EXAMPLE 3 Consider the fragment:
5944 cpp = &p; // constraint violation
5945 *cpp = &c; // valid
5948 The first assignment is unsafe because it would allow the following valid code to attempt to change the
5949 value of the const object c.
5953 <p><small><a name="note112" href="#note112">112)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
5954 (specified in <a href="#6.3.2.1">6.3.2.1</a>) that changes lvalues to ''the value of the expression'' and thus removes any type
5955 qualifiers that were applied to the type category of the expression (for example, it removes const but
5956 not volatile from the type int volatile * const).
5959 <p><small><a href="#Contents">Contents</a></small>
5960 <h5><a name="6.5.16.2" href="#6.5.16.2">6.5.16.2 Compound assignment</a></h5>
5961 <p><b>Constraints</b>
5962 <p><a name="6.5.16.2p1" href="#6.5.16.2p1"><small>1</small></a>
5963 For the operators += and -= only, either the left operand shall be an atomic, qualified, or
5964 unqualified pointer to a complete object type, and the right shall have integer type; or the
5965 left operand shall have atomic, qualified, or unqualified arithmetic type, and the right
5966 shall have arithmetic type.
5967 <p><a name="6.5.16.2p2" href="#6.5.16.2p2"><small>2</small></a>
5968 For the other operators, the left operand shall have atomic, qualified, or unqualified
5969 arithmetic type, and (considering the type the left operand would have after lvalue
5970 conversion) each operand shall have arithmetic type consistent with those allowed by the
5971 corresponding binary operator.
5973 <p><a name="6.5.16.2p3" href="#6.5.16.2p3"><small>3</small></a>
5974 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
5975 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
5976 respect to an indeterminately-sequenced function call, the operation of a compound
5978 assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
5979 read-modify-write operation with memory_order_seq_cst memory order
5980 semantics.<sup><a href="#note113"><b>113)</b></a></sup>
5988 <p><small><a name="note113" href="#note113">113)</a> Where a pointer to an atomic object can be formed and E1 and E2 have integer type, this is equivalent
5989 to the following code sequence where T1 is the type of E1 and T2 is the type of E2:
5998 } while (!atomic_compare_exchange_strong(addr, &old, new));
6000 with new being the result of the operation.
6001 If E1 or E2 has floating type, then exceptional conditions or floating-point exceptions encountered
6002 during discarded evaluations of new should also be discarded in order to satisfy the equivalence of E1
6003 op = E2 and E1 = E1 op (E2). For example, if <a href="#F">annex F</a> is in effect, the floating types involved have
6004 IEC 60559 formats, and FLT_EVAL_METHOD is 0, the equivalent code would be:
6007 #include <a href="#7.6"><fenv.h></a>
6008 #pragma STDC FENV_ACCESS ON
6015 feholdexcept(&fenv);
6018 if (atomic_compare_exchange_strong(addr, &old, new))
6020 feclearexcept(FE_ALL_EXCEPT);
6022 feupdateenv(&fenv);
6024 If FLT_EVAL_METHOD is not 0, then T2 must be a type with the range and precision to which E2 is
6025 evaluated in order to satisfy the equivalence.
6028 <p><small><a href="#Contents">Contents</a></small>
6029 <h4><a name="6.5.17" href="#6.5.17">6.5.17 Comma operator</a></h4>
6031 <p><a name="6.5.17p1" href="#6.5.17p1"><small>1</small></a>
6034 assignment-expression
6035 expression , assignment-expression
6038 <p><a name="6.5.17p2" href="#6.5.17p2"><small>2</small></a>
6039 The left operand of a comma operator is evaluated as a void expression; there is a
6040 sequence point between its evaluation and that of the right operand. Then the right
6041 operand is evaluated; the result has its type and value.<sup><a href="#note114"><b>114)</b></a></sup>
6042 <p><a name="6.5.17p3" href="#6.5.17p3"><small>3</small></a>
6043 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
6044 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
6045 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
6046 expression of a conditional operator in such contexts. In the function call
6050 the function has three arguments, the second of which has the value 5.
6052 <p><b> Forward references</b>: initialization (<a href="#6.7.9">6.7.9</a>).
6060 <p><small><a name="note114" href="#note114">114)</a> A comma operator does not yield an lvalue.
6063 <p><small><a href="#Contents">Contents</a></small>
6064 <h3><a name="6.6" href="#6.6">6.6 Constant expressions</a></h3>
6066 <p><a name="6.6p1" href="#6.6p1"><small>1</small></a>
6068 constant-expression:
6069 conditional-expression
6071 <p><b>Description</b>
6072 <p><a name="6.6p2" href="#6.6p2"><small>2</small></a>
6073 A constant expression can be evaluated during translation rather than runtime, and
6074 accordingly may be used in any place that a constant may be.
6075 <p><b>Constraints</b>
6076 <p><a name="6.6p3" href="#6.6p3"><small>3</small></a>
6077 Constant expressions shall not contain assignment, increment, decrement, function-call,
6078 or comma operators, except when they are contained within a subexpression that is not
6079 evaluated.<sup><a href="#note115"><b>115)</b></a></sup>
6080 <p><a name="6.6p4" href="#6.6p4"><small>4</small></a>
6081 Each constant expression shall evaluate to a constant that is in the range of representable
6082 values for its type.
6084 <p><a name="6.6p5" href="#6.6p5"><small>5</small></a>
6085 An expression that evaluates to a constant is required in several contexts. If a floating
6086 expression is evaluated in the translation environment, the arithmetic range and precision
6087 shall be at least as great as if the expression were being evaluated in the execution
6088 environment.<sup><a href="#note116"><b>116)</b></a></sup>
6089 <p><a name="6.6p6" href="#6.6p6"><small>6</small></a>
6090 An integer constant expression<sup><a href="#note117"><b>117)</b></a></sup> shall have integer type and shall only have operands
6091 that are integer constants, enumeration constants, character constants, sizeof
6092 expressions whose results are integer constants, _Alignof expressions, and floating
6093 constants that are the immediate operands of casts. Cast operators in an integer constant
6094 expression shall only convert arithmetic types to integer types, except as part of an
6095 operand to the sizeof or _Alignof operator.
6096 <p><a name="6.6p7" href="#6.6p7"><small>7</small></a>
6097 More latitude is permitted for constant expressions in initializers. Such a constant
6098 expression shall be, or evaluate to, one of the following:
6100 <li> an arithmetic constant expression,
6105 <li> a null pointer constant,
6106 <li> an address constant, or
6107 <li> an address constant for a complete object type plus or minus an integer constant
6110 <p><a name="6.6p8" href="#6.6p8"><small>8</small></a>
6111 An arithmetic constant expression shall have arithmetic type and shall only have
6112 operands that are integer constants, floating constants, enumeration constants, character
6113 constants, sizeof expressions whose results are integer constants, and _Alignof
6114 expressions. Cast operators in an arithmetic constant expression shall only convert
6115 arithmetic types to arithmetic types, except as part of an operand to a sizeof or
6117 <p><a name="6.6p9" href="#6.6p9"><small>9</small></a>
6118 An address constant is a null pointer, a pointer to an lvalue designating an object of static
6119 storage duration, or a pointer to a function designator; it shall be created explicitly using
6120 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
6121 an expression of array or function type. The array-subscript [] and member-access .
6122 and -> operators, the address & and indirection * unary operators, and pointer casts may
6123 be used in the creation of an address constant, but the value of an object shall not be
6124 accessed by use of these operators.
6125 <p><a name="6.6p10" href="#6.6p10"><small>10</small></a>
6126 An implementation may accept other forms of constant expressions.
6127 <p><a name="6.6p11" href="#6.6p11"><small>11</small></a>
6128 The semantic rules for the evaluation of a constant expression are the same as for
6129 nonconstant expressions.<sup><a href="#note118"><b>118)</b></a></sup>
6130 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), initialization (<a href="#6.7.9">6.7.9</a>).
6138 <p><small><a name="note115" href="#note115">115)</a> The operand of a sizeof or _Alignof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
6140 <p><small><a name="note116" href="#note116">116)</a> The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
6141 the translation environment.
6143 <p><small><a name="note117" href="#note117">117)</a> An integer constant expression is required in a number of contexts such as the size of a bit-field
6144 member of a structure, the value of an enumeration constant, and the size of a non-variable length
6145 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
6146 preprocessing directives are discussed in <a href="#6.10.1">6.10.1</a>.
6148 <p><small><a name="note118" href="#note118">118)</a> Thus, in the following initialization,
6151 static int i = 2 || 1 / 0;
6153 the expression is a valid integer constant expression with value one.
6156 <p><small><a href="#Contents">Contents</a></small>
6157 <h3><a name="6.7" href="#6.7">6.7 Declarations</a></h3>
6159 <p><a name="6.7p1" href="#6.7p1"><small>1</small></a>
6162 declaration-specifiers init-declarator-list<sub>opt</sub> ;
6163 static_assert-declaration
6164 declaration-specifiers:
6165 storage-class-specifier declaration-specifiers<sub>opt</sub>
6166 type-specifier declaration-specifiers<sub>opt</sub>
6167 type-qualifier declaration-specifiers<sub>opt</sub>
6168 function-specifier declaration-specifiers<sub>opt</sub>
6169 alignment-specifier declaration-specifiers<sub>opt</sub>
6170 init-declarator-list:
6172 init-declarator-list , init-declarator
6175 declarator = initializer
6177 <p><b>Constraints</b>
6178 <p><a name="6.7p2" href="#6.7p2"><small>2</small></a>
6179 A declaration other than a static_assert declaration shall declare at least a declarator
6180 (other than the parameters of a function or the members of a structure or union), a tag, or
6181 the members of an enumeration.
6182 <p><a name="6.7p3" href="#6.7p3"><small>3</small></a>
6183 If an identifier has no linkage, there shall be no more than one declaration of the identifier
6184 (in a declarator or type specifier) with the same scope and in the same name space, except
6187 <li> a typedef name may be redefined to denote the same type as it currently does,
6188 provided that type is not a variably modified type;
6189 <li> tags may be redeclared as specified in <a href="#6.7.2.3">6.7.2.3</a>.
6191 <p><a name="6.7p4" href="#6.7p4"><small>4</small></a>
6192 All declarations in the same scope that refer to the same object or function shall specify
6195 <p><a name="6.7p5" href="#6.7p5"><small>5</small></a>
6196 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
6197 of an identifier is a declaration for that identifier that:
6199 <li> for an object, causes storage to be reserved for that object;
6200 <li> for a function, includes the function body;<sup><a href="#note119"><b>119)</b></a></sup>
6202 <li> for an enumeration constant, is the (only) declaration of the identifier;
6203 <li> for a typedef name, is the first (or only) declaration of the identifier.
6205 <p><a name="6.7p6" href="#6.7p6"><small>6</small></a>
6206 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
6207 storage duration, and part of the type of the entities that the declarators denote. The init-
6208 declarator-list is a comma-separated sequence of declarators, each of which may have
6209 additional type information, or an initializer, or both. The declarators contain the
6210 identifiers (if any) being declared.
6211 <p><a name="6.7p7" href="#6.7p7"><small>7</small></a>
6212 If an identifier for an object is declared with no linkage, the type for the object shall be
6213 complete by the end of its declarator, or by the end of its init-declarator if it has an
6214 initializer; in the case of function parameters (including in prototypes), it is the adjusted
6215 type (see <a href="#6.7.6.3">6.7.6.3</a>) that is required to be complete.
6216 <p><b> Forward references</b>: declarators (<a href="#6.7.6">6.7.6</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
6217 (<a href="#6.7.9">6.7.9</a>), type names (<a href="#6.7.7">6.7.7</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>).
6220 <p><small><a name="note119" href="#note119">119)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
6223 <p><small><a href="#Contents">Contents</a></small>
6224 <h4><a name="6.7.1" href="#6.7.1">6.7.1 Storage-class specifiers</a></h4>
6226 <p><a name="6.7.1p1" href="#6.7.1p1"><small>1</small></a>
6228 storage-class-specifier:
6236 <p><b>Constraints</b>
6237 <p><a name="6.7.1p2" href="#6.7.1p2"><small>2</small></a>
6238 At most, one storage-class specifier may be given in the declaration specifiers in a
6239 declaration, except that _Thread_local may appear with static or extern.<sup><a href="#note120"><b>120)</b></a></sup>
6240 <p><a name="6.7.1p3" href="#6.7.1p3"><small>3</small></a>
6241 In the declaration of an object with block scope, if the declaration specifiers include
6242 _Thread_local, they shall also include either static or extern. If
6243 _Thread_local appears in any declaration of an object, it shall be present in every
6244 declaration of that object.
6245 <p><a name="6.7.1p4" href="#6.7.1p4"><small>4</small></a>
6246 _Thread_local shall not appear in the declaration specifiers of a function declaration.
6253 <p><a name="6.7.1p5" href="#6.7.1p5"><small>5</small></a>
6254 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
6255 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
6256 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
6257 <p><a name="6.7.1p6" href="#6.7.1p6"><small>6</small></a>
6258 A declaration of an identifier for an object with storage-class specifier register
6259 suggests that access to the object be as fast as possible. The extent to which such
6260 suggestions are effective is implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
6261 <p><a name="6.7.1p7" href="#6.7.1p7"><small>7</small></a>
6262 The declaration of an identifier for a function that has block scope shall have no explicit
6263 storage-class specifier other than extern.
6264 <p><a name="6.7.1p8" href="#6.7.1p8"><small>8</small></a>
6265 If an aggregate or union object is declared with a storage-class specifier other than
6266 typedef, the properties resulting from the storage-class specifier, except with respect to
6267 linkage, also apply to the members of the object, and so on recursively for any aggregate
6268 or union member objects.
6269 <p><b> Forward references</b>: type definitions (<a href="#6.7.8">6.7.8</a>).
6277 <p><small><a name="note120" href="#note120">120)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
6279 <p><small><a name="note121" href="#note121">121)</a> The implementation may treat any register declaration simply as an auto declaration. However,
6280 whether or not addressable storage is actually used, the address of any part of an object declared with
6281 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
6282 operator as discussed in <a href="#6.5.3.2">6.5.3.2</a>) or implicitly (by converting an array name to a pointer as discussed in
6283 <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operators that can be applied to an array declared with storage-class specifier
6284 register are sizeof and _Alignof.
6287 <p><small><a href="#Contents">Contents</a></small>
6288 <h4><a name="6.7.2" href="#6.7.2">6.7.2 Type specifiers</a></h4>
6290 <p><a name="6.7.2p1" href="#6.7.2p1"><small>1</small></a>
6304 atomic-type-specifier
6305 struct-or-union-specifier
6309 <p><b>Constraints</b>
6310 <p><a name="6.7.2p2" href="#6.7.2p2"><small>2</small></a>
6311 At least one type specifier shall be given in the declaration specifiers in each declaration,
6312 and in the specifier-qualifier list in each struct declaration and type name. Each list of
6313 type specifiers shall be one of the following multisets (delimited by commas, when there
6314 is more than one multiset per item); the type specifiers may occur in any order, possibly
6315 intermixed with the other declaration specifiers.
6321 <li> short, signed short, short int, or signed short int
6322 <li> unsigned short, or unsigned short int
6323 <li> int, signed, or signed int
6324 <li> unsigned, or unsigned int
6325 <li> long, signed long, long int, or signed long int
6326 <li> unsigned long, or unsigned long int
6328 <li> long long, signed long long, long long int, or
6329 signed long long int
6330 <li> unsigned long long, or unsigned long long int
6336 <li> double _Complex
6337 <li> long double _Complex
6338 <li> atomic type specifier
6339 <li> struct or union specifier
6343 <p><a name="6.7.2p3" href="#6.7.2p3"><small>3</small></a>
6344 The type specifier _Complex shall not be used if the implementation does not support
6345 complex types (see <a href="#6.10.8.3">6.10.8.3</a>).
6347 <p><a name="6.7.2p4" href="#6.7.2p4"><small>4</small></a>
6348 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href="#6.7.2.1">6.7.2.1</a>
6349 through <a href="#6.7.2.4">6.7.2.4</a>. Declarations of typedef names are discussed in <a href="#6.7.8">6.7.8</a>. The
6350 characteristics of the other types are discussed in <a href="#6.2.5">6.2.5</a>.
6351 <p><a name="6.7.2p5" href="#6.7.2p5"><small>5</small></a>
6352 Each of the comma-separated multisets designates the same type, except that for bit-
6353 fields, it is implementation-defined whether the specifier int designates the same type as
6354 signed int or the same type as unsigned int.
6355 <p><b> Forward references</b>: atomic type specifiers (<a href="#6.7.2.4">6.7.2.4</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>),
6356 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
6358 <p><small><a href="#Contents">Contents</a></small>
6359 <h5><a name="6.7.2.1" href="#6.7.2.1">6.7.2.1 Structure and union specifiers</a></h5>
6361 <p><a name="6.7.2.1p1" href="#6.7.2.1p1"><small>1</small></a>
6364 struct-or-union-specifier:
6365 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
6366 struct-or-union identifier
6370 struct-declaration-list:
6372 struct-declaration-list struct-declaration
6374 specifier-qualifier-list struct-declarator-list<sub>opt</sub> ;
6375 static_assert-declaration
6376 specifier-qualifier-list:
6377 type-specifier specifier-qualifier-list<sub>opt</sub>
6378 type-qualifier specifier-qualifier-list<sub>opt</sub>
6379 struct-declarator-list:
6381 struct-declarator-list , struct-declarator
6384 declarator<sub>opt</sub> : constant-expression
6386 <p><b>Constraints</b>
6387 <p><a name="6.7.2.1p2" href="#6.7.2.1p2"><small>2</small></a>
6388 A struct-declaration that does not declare an anonymous structure or anonymous union
6389 shall contain a struct-declarator-list.
6390 <p><a name="6.7.2.1p3" href="#6.7.2.1p3"><small>3</small></a>
6391 A structure or union shall not contain a member with incomplete or function type (hence,
6392 a structure shall not contain an instance of itself, but may contain a pointer to an instance
6393 of itself), except that the last member of a structure with more than one named member
6394 may have incomplete array type; such a structure (and any union containing, possibly
6395 recursively, a member that is such a structure) shall not be a member of a structure or an
6396 element of an array.
6397 <p><a name="6.7.2.1p4" href="#6.7.2.1p4"><small>4</small></a>
6398 The expression that specifies the width of a bit-field shall be an integer constant
6399 expression with a nonnegative value that does not exceed the width of an object of the
6400 type that would be specified were the colon and expression omitted.<sup><a href="#note122"><b>122)</b></a></sup> If the value is
6401 zero, the declaration shall have no declarator.
6402 <p><a name="6.7.2.1p5" href="#6.7.2.1p5"><small>5</small></a>
6403 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
6404 int, unsigned int, or some other implementation-defined type. It is
6405 implementation-defined whether atomic types are permitted.
6409 <p><a name="6.7.2.1p6" href="#6.7.2.1p6"><small>6</small></a>
6410 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
6411 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
6412 of members whose storage overlap.
6413 <p><a name="6.7.2.1p7" href="#6.7.2.1p7"><small>7</small></a>
6414 Structure and union specifiers have the same form. The keywords struct and union
6415 indicate that the type being specified is, respectively, a structure type or a union type.
6416 <p><a name="6.7.2.1p8" href="#6.7.2.1p8"><small>8</small></a>
6417 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
6418 within a translation unit. The struct-declaration-list is a sequence of declarations for the
6419 members of the structure or union. If the struct-declaration-list does not contain any
6420 named members, either directly or via an anonymous structure or anonymous union, the
6421 behavior is undefined. The type is incomplete until immediately after the } that
6422 terminates the list, and complete thereafter.
6423 <p><a name="6.7.2.1p9" href="#6.7.2.1p9"><small>9</small></a>
6424 A member of a structure or union may have any complete object type other than a
6425 variably modified type.<sup><a href="#note123"><b>123)</b></a></sup> In addition, a member may be declared to consist of a
6426 specified number of bits (including a sign bit, if any). Such a member is called a
6427 bit-field;<sup><a href="#note124"><b>124)</b></a></sup> its width is preceded by a colon.
6428 <p><a name="6.7.2.1p10" href="#6.7.2.1p10"><small>10</small></a>
6429 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
6430 specified number of bits.<sup><a href="#note125"><b>125)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of
6431 type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool
6432 bit-field has the semantics of a _Bool.
6433 <p><a name="6.7.2.1p11" href="#6.7.2.1p11"><small>11</small></a>
6434 An implementation may allocate any addressable storage unit large enough to hold a bit-
6435 field. If enough space remains, a bit-field that immediately follows another bit-field in a
6436 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
6437 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
6438 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
6439 low-order or low-order to high-order) is implementation-defined. The alignment of the
6440 addressable storage unit is unspecified.
6441 <p><a name="6.7.2.1p12" href="#6.7.2.1p12"><small>12</small></a>
6442 A bit-field declaration with no declarator, but only a colon and a width, indicates an
6443 unnamed bit-field.<sup><a href="#note126"><b>126)</b></a></sup> As a special case, a bit-field structure member with a width of 0
6447 indicates that no further bit-field is to be packed into the unit in which the previous bit-
6448 field, if any, was placed.
6449 <p><a name="6.7.2.1p13" href="#6.7.2.1p13"><small>13</small></a>
6450 An unnamed member whose type specifier is a structure specifier with no tag is called an
6451 anonymous structure; an unnamed member whose type specifier is a union specifier with
6452 no tag is called an anonymous union. The members of an anonymous structure or union
6453 are considered to be members of the containing structure or union. This applies
6454 recursively if the containing structure or union is also anonymous.
6455 <p><a name="6.7.2.1p14" href="#6.7.2.1p14"><small>14</small></a>
6456 Each non-bit-field member of a structure or union object is aligned in an implementation-
6457 defined manner appropriate to its type.
6458 <p><a name="6.7.2.1p15" href="#6.7.2.1p15"><small>15</small></a>
6459 Within a structure object, the non-bit-field members and the units in which bit-fields
6460 reside have addresses that increase in the order in which they are declared. A pointer to a
6461 structure object, suitably converted, points to its initial member (or if that member is a
6462 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
6463 padding within a structure object, but not at its beginning.
6464 <p><a name="6.7.2.1p16" href="#6.7.2.1p16"><small>16</small></a>
6465 The size of a union is sufficient to contain the largest of its members. The value of at
6466 most one of the members can be stored in a union object at any time. A pointer to a
6467 union object, suitably converted, points to each of its members (or if a member is a bit-
6468 field, then to the unit in which it resides), and vice versa.
6469 <p><a name="6.7.2.1p17" href="#6.7.2.1p17"><small>17</small></a>
6470 There may be unnamed padding at the end of a structure or union.
6471 <p><a name="6.7.2.1p18" href="#6.7.2.1p18"><small>18</small></a>
6472 As a special case, the last element of a structure with more than one named member may
6473 have an incomplete array type; this is called a flexible array member. In most situations,
6474 the flexible array member is ignored. In particular, the size of the structure is as if the
6475 flexible array member were omitted except that it may have more trailing padding than
6476 the omission would imply. However, when a . (or ->) operator has a left operand that is
6477 (a pointer to) a structure with a flexible array member and the right operand names that
6478 member, it behaves as if that member were replaced with the longest array (with the same
6479 element type) that would not make the structure larger than the object being accessed; the
6480 offset of the array shall remain that of the flexible array member, even if this would differ
6481 from that of the replacement array. If this array would have no elements, it behaves as if
6482 it had one element but the behavior is undefined if any attempt is made to access that
6483 element or to generate a pointer one past it.
6484 <p><a name="6.7.2.1p19" href="#6.7.2.1p19"><small>19</small></a>
6485 EXAMPLE 1 The following illustrates anonymous structures and unions:
6489 union { // anonymous union
6490 struct { int i, j; }; // anonymous structure
6491 struct { long k, l; } w;
6496 v1.k = 3; // invalid: inner structure is not anonymous
6497 v1.w.k = 5; // valid
6500 <p><a name="6.7.2.1p20" href="#6.7.2.1p20"><small>20</small></a>
6501 EXAMPLE 2 After the declaration:
6503 struct s { int n; double d[]; };
6505 the structure struct s has a flexible array member d. A typical way to use this is:
6507 int m = /* some value */;
6508 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
6510 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
6511 p had been declared as:
6513 struct { int n; double d[m]; } *p;
6515 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
6517 <p><a name="6.7.2.1p21" href="#6.7.2.1p21"><small>21</small></a>
6518 Following the above declaration:
6520 struct s t1 = { 0 }; // valid
6521 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
6523 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior
6525 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
6526 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
6528 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
6530 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
6532 <p><a name="6.7.2.1p22" href="#6.7.2.1p22"><small>22</small></a>
6533 After the further declaration:
6535 struct ss { int n; };
6539 sizeof (struct s) >= sizeof (struct ss)
6540 sizeof (struct s) >= offsetof(struct s, d)
6542 are always equal to 1.
6543 <p><a name="6.7.2.1p23" href="#6.7.2.1p23"><small>23</small></a>
6544 If sizeof (double) is 8, then after the following code is executed:
6548 s1 = malloc(sizeof (struct s) + 64);
6549 s2 = malloc(sizeof (struct s) + 46);
6551 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
6552 purposes, as if the identifiers had been declared as:
6554 struct { int n; double d[8]; } *s1;
6555 struct { int n; double d[5]; } *s2;
6557 <p><a name="6.7.2.1p24" href="#6.7.2.1p24"><small>24</small></a>
6558 Following the further successful assignments:
6561 s1 = malloc(sizeof (struct s) + 10);
6562 s2 = malloc(sizeof (struct s) + 6);
6564 they then behave as if the declarations were:
6566 struct { int n; double d[1]; } *s1, *s2;
6571 dp = &(s1->d[0]); // valid
6573 dp = &(s2->d[0]); // valid
6574 *dp = 42; // undefined behavior
6576 <p><a name="6.7.2.1p25" href="#6.7.2.1p25"><small>25</small></a>
6581 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
6582 of the structure, they might be copied or simply overwritten with indeterminate values.
6584 <p><a name="6.7.2.1p26" href="#6.7.2.1p26"><small>26</small></a>
6585 EXAMPLE 3 Because members of anonymous structures and unions are considered to be members of the
6586 containing structure or union, struct s in the following example has more than one named member and
6587 thus the use of a flexible array member is valid:
6595 <p><b> Forward references</b>: declarators (<a href="#6.7.6">6.7.6</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>).
6598 <p><small><a name="note122" href="#note122">122)</a> While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
6599 value bits) of a _Bool may be just 1 bit.
6601 <p><small><a name="note123" href="#note123">123)</a> A structure or union cannot contain a member with a variably modified type because member names
6602 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
6604 <p><small><a name="note124" href="#note124">124)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
6605 or arrays of bit-field objects.
6607 <p><small><a name="note125" href="#note125">125)</a> As specified in <a href="#6.7.2">6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int,
6608 then it is implementation-defined whether the bit-field is signed or unsigned.
6610 <p><small><a name="note126" href="#note126">126)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
6614 <p><small><a href="#Contents">Contents</a></small>
6615 <h5><a name="6.7.2.2" href="#6.7.2.2">6.7.2.2 Enumeration specifiers</a></h5>
6617 <p><a name="6.7.2.2p1" href="#6.7.2.2p1"><small>1</small></a>
6620 enum identifier<sub>opt</sub> { enumerator-list }
6621 enum identifier<sub>opt</sub> { enumerator-list , }
6625 enumerator-list , enumerator
6627 enumeration-constant
6628 enumeration-constant = constant-expression
6630 <p><b>Constraints</b>
6631 <p><a name="6.7.2.2p2" href="#6.7.2.2p2"><small>2</small></a>
6632 The expression that defines the value of an enumeration constant shall be an integer
6633 constant expression that has a value representable as an int.
6636 <p><a name="6.7.2.2p3" href="#6.7.2.2p3"><small>3</small></a>
6637 The identifiers in an enumerator list are declared as constants that have type int and
6638 may appear wherever such are permitted.<sup><a href="#note127"><b>127)</b></a></sup> An enumerator with = defines its
6639 enumeration constant as the value of the constant expression. If the first enumerator has
6640 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
6641 defines its enumeration constant as the value of the constant expression obtained by
6642 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
6643 = may produce enumeration constants with values that duplicate other values in the same
6644 enumeration.) The enumerators of an enumeration are also known as its members.
6645 <p><a name="6.7.2.2p4" href="#6.7.2.2p4"><small>4</small></a>
6646 Each enumerated type shall be compatible with char, a signed integer type, or an
6647 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note128"><b>128)</b></a></sup> but shall be
6648 capable of representing the values of all the members of the enumeration. The
6649 enumerated type is incomplete until immediately after the } that terminates the list of
6650 enumerator declarations, and complete thereafter.
6651 <p><a name="6.7.2.2p5" href="#6.7.2.2p5"><small>5</small></a>
6652 EXAMPLE The following fragment:
6654 enum hue { chartreuse, burgundy, claret=20, winedark };
6658 if (*cp != burgundy)
6661 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
6662 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
6664 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
6667 <p><small><a name="note127" href="#note127">127)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
6668 each other and from other identifiers declared in ordinary declarators.
6670 <p><small><a name="note128" href="#note128">128)</a> An implementation may delay the choice of which integer type until all enumeration constants have
6674 <p><small><a href="#Contents">Contents</a></small>
6675 <h5><a name="6.7.2.3" href="#6.7.2.3">6.7.2.3 Tags</a></h5>
6676 <p><b>Constraints</b>
6677 <p><a name="6.7.2.3p1" href="#6.7.2.3p1"><small>1</small></a>
6678 A specific type shall have its content defined at most once.
6679 <p><a name="6.7.2.3p2" href="#6.7.2.3p2"><small>2</small></a>
6680 Where two declarations that use the same tag declare the same type, they shall both use
6681 the same choice of struct, union, or enum.
6682 <p><a name="6.7.2.3p3" href="#6.7.2.3p3"><small>3</small></a>
6683 A type specifier of the form
6687 without an enumerator list shall only appear after the type it specifies is complete.
6692 <p><a name="6.7.2.3p4" href="#6.7.2.3p4"><small>4</small></a>
6693 All declarations of structure, union, or enumerated types that have the same scope and
6694 use the same tag declare the same type. Irrespective of whether there is a tag or what
6695 other declarations of the type are in the same translation unit, the type is incomplete<sup><a href="#note129"><b>129)</b></a></sup>
6696 until immediately after the closing brace of the list defining the content, and complete
6698 <p><a name="6.7.2.3p5" href="#6.7.2.3p5"><small>5</small></a>
6699 Two declarations of structure, union, or enumerated types which are in different scopes or
6700 use different tags declare distinct types. Each declaration of a structure, union, or
6701 enumerated type which does not include a tag declares a distinct type.
6702 <p><a name="6.7.2.3p6" href="#6.7.2.3p6"><small>6</small></a>
6703 A type specifier of the form
6705 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
6709 enum identifier<sub>opt</sub> { enumerator-list }
6713 enum identifier<sub>opt</sub> { enumerator-list , }
6715 declares a structure, union, or enumerated type. The list defines the structure content,
6716 union content, or enumeration content. If an identifier is provided,<sup><a href="#note130"><b>130)</b></a></sup> the type specifier
6717 also declares the identifier to be the tag of that type.
6718 <p><a name="6.7.2.3p7" href="#6.7.2.3p7"><small>7</small></a>
6719 A declaration of the form
6721 struct-or-union identifier ;
6723 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note131"><b>131)</b></a></sup>
6724 <p><a name="6.7.2.3p8" href="#6.7.2.3p8"><small>8</small></a>
6725 If a type specifier of the form
6727 struct-or-union identifier
6729 occurs other than as part of one of the above forms, and no other declaration of the
6730 identifier as a tag is visible, then it declares an incomplete structure or union type, and
6731 declares the identifier as the tag of that type.<sup><a href="#note131"><b>131)</b></a></sup>
6736 <p><a name="6.7.2.3p9" href="#6.7.2.3p9"><small>9</small></a>
6737 If a type specifier of the form
6739 struct-or-union identifier
6745 occurs other than as part of one of the above forms, and a declaration of the identifier as a
6746 tag is visible, then it specifies the same type as that other declaration, and does not
6748 <p><a name="6.7.2.3p10" href="#6.7.2.3p10"><small>10</small></a>
6749 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
6753 struct tnode *left, *right;
6756 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
6757 declaration has been given, the declaration
6759 struct tnode s, *sp;
6761 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
6762 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
6763 which sp points; the expression s.right->count designates the count member of the right struct
6764 tnode pointed to from s.
6765 <p><a name="6.7.2.3p11" href="#6.7.2.3p11"><small>11</small></a>
6766 The following alternative formulation uses the typedef mechanism:
6768 typedef struct tnode TNODE;
6771 TNODE *left, *right;
6776 <p><a name="6.7.2.3p12" href="#6.7.2.3p12"><small>12</small></a>
6777 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
6778 structures, the declarations
6780 struct s1 { struct s2 *s2p; /* ... */ }; // D1
6781 struct s2 { struct s1 *s1p; /* ... */ }; // D2
6783 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
6784 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
6785 D2. To eliminate this context sensitivity, the declaration
6789 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
6790 completes the specification of the new type.
6792 <p><b> Forward references</b>: declarators (<a href="#6.7.6">6.7.6</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
6796 <p><small><a name="note129" href="#note129">129)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
6797 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
6798 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
6799 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
6801 <p><small><a name="note130" href="#note130">130)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
6802 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
6803 can make use of that typedef name to declare objects having the specified structure, union, or
6806 <p><small><a name="note131" href="#note131">131)</a> A similar construction with enum does not exist.
6809 <p><small><a href="#Contents">Contents</a></small>
6810 <h5><a name="6.7.2.4" href="#6.7.2.4">6.7.2.4 Atomic type specifiers</a></h5>
6812 <p><a name="6.7.2.4p1" href="#6.7.2.4p1"><small>1</small></a>
6814 atomic-type-specifier:
6815 _Atomic ( type-name )
6817 <p><b>Constraints</b>
6818 <p><a name="6.7.2.4p2" href="#6.7.2.4p2"><small>2</small></a>
6819 Atomic type specifiers shall not be used if the implementation does not support atomic
6820 types (see <a href="#6.10.8.3">6.10.8.3</a>).
6821 <p><a name="6.7.2.4p3" href="#6.7.2.4p3"><small>3</small></a>
6822 The type name in an atomic type specifier shall not refer to an array type, a function type,
6823 an atomic type, or a qualified type.
6825 <p><a name="6.7.2.4p4" href="#6.7.2.4p4"><small>4</small></a>
6826 The properties associated with atomic types are meaningful only for expressions that are
6827 lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
6828 interpreted as a type specifier (with a type name), not as a type qualifier.
6830 <p><small><a href="#Contents">Contents</a></small>
6831 <h4><a name="6.7.3" href="#6.7.3">6.7.3 Type qualifiers</a></h4>
6833 <p><a name="6.7.3p1" href="#6.7.3p1"><small>1</small></a>
6841 <p><b>Constraints</b>
6842 <p><a name="6.7.3p2" href="#6.7.3p2"><small>2</small></a>
6843 Types other than pointer types whose referenced type is an object type shall not be
6845 <p><a name="6.7.3p3" href="#6.7.3p3"><small>3</small></a>
6846 The type modified by the _Atomic qualifier shall not be an array type or a function
6849 <p><a name="6.7.3p4" href="#6.7.3p4"><small>4</small></a>
6850 The properties associated with qualified types are meaningful only for expressions that
6851 are lvalues.<sup><a href="#note132"><b>132)</b></a></sup>
6852 <p><a name="6.7.3p5" href="#6.7.3p5"><small>5</small></a>
6853 If the same qualifier appears more than once in the same specifier-qualifier-list, either
6854 directly or via one or more typedefs, the behavior is the same as if it appeared only
6855 once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier-
6858 list, the resulting type is the so-qualified atomic type.
6859 <p><a name="6.7.3p6" href="#6.7.3p6"><small>6</small></a>
6860 If an attempt is made to modify an object defined with a const-qualified type through use
6861 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
6862 made to refer to an object defined with a volatile-qualified type through use of an lvalue
6863 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note133"><b>133)</b></a></sup>
6864 <p><a name="6.7.3p7" href="#6.7.3p7"><small>7</small></a>
6865 An object that has volatile-qualified type may be modified in ways unknown to the
6866 implementation or have other unknown side effects. Therefore any expression referring
6867 to such an object shall be evaluated strictly according to the rules of the abstract machine,
6868 as described in <a href="#5.1.2.3">5.1.2.3</a>. Furthermore, at every sequence point the value last stored in the
6869 object shall agree with that prescribed by the abstract machine, except as modified by the
6870 unknown factors mentioned previously.<sup><a href="#note134"><b>134)</b></a></sup> What constitutes an access to an object that
6871 has volatile-qualified type is implementation-defined.
6872 <p><a name="6.7.3p8" href="#6.7.3p8"><small>8</small></a>
6873 An object that is accessed through a restrict-qualified pointer has a special association
6874 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
6875 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note135"><b>135)</b></a></sup> The intended
6876 use of the restrict qualifier (like the register storage class) is to promote
6877 optimization, and deleting all instances of the qualifier from all preprocessing translation
6878 units composing a conforming program does not change its meaning (i.e., observable
6880 <p><a name="6.7.3p9" href="#6.7.3p9"><small>9</small></a>
6881 If the specification of an array type includes any type qualifiers, the element type is so-
6882 qualified, not the array type. If the specification of a function type includes any type
6883 qualifiers, the behavior is undefined.<sup><a href="#note136"><b>136)</b></a></sup>
6884 <p><a name="6.7.3p10" href="#6.7.3p10"><small>10</small></a>
6885 For two qualified types to be compatible, both shall have the identically qualified version
6886 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
6887 does not affect the specified type.
6888 <p><a name="6.7.3p11" href="#6.7.3p11"><small>11</small></a>
6889 EXAMPLE 1 An object declared
6891 extern const volatile int real_time_clock;
6897 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
6899 <p><a name="6.7.3p12" href="#6.7.3p12"><small>12</small></a>
6900 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
6901 modify an aggregate type:
6903 const struct s { int mem; } cs = { 1 };
6904 struct s ncs; // the object ncs is modifiable
6905 typedef int A[2][3];
6906 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
6910 cs = ncs; // violates modifiable lvalue constraint for =
6911 pi = &ncs.mem; // valid
6912 pi = &cs.mem; // violates type constraints for =
6913 pci = &cs.mem; // valid
6914 pi = a[0]; // invalid: a[0] has type ''const int *''
6917 <p><a name="6.7.3p13" href="#6.7.3p13"><small>13</small></a>
6918 EXAMPLE 3 The declaration
6920 _Atomic volatile int *p;
6922 specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type.
6926 <p><small><a name="note132" href="#note132">132)</a> The implementation may place a const object that is not volatile in a read-only region of
6927 storage. Moreover, the implementation need not allocate storage for such an object if its address is
6930 <p><small><a name="note133" href="#note133">133)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
6931 never actually defined as objects in the program (such as an object at a memory-mapped input/output
6934 <p><small><a name="note134" href="#note134">134)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
6935 input/output port or an object accessed by an asynchronously interrupting function. Actions on
6936 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
6937 permitted by the rules for evaluating expressions.
6939 <p><small><a name="note135" href="#note135">135)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
6940 association between the allocated object and the pointer.
6942 <p><small><a name="note136" href="#note136">136)</a> Both of these can occur through the use of typedefs.
6945 <p><small><a href="#Contents">Contents</a></small>
6946 <h5><a name="6.7.3.1" href="#6.7.3.1">6.7.3.1 Formal definition of restrict</a></h5>
6947 <p><a name="6.7.3.1p1" href="#6.7.3.1p1"><small>1</small></a>
6948 Let D be a declaration of an ordinary identifier that provides a means of designating an
6949 object P as a restrict-qualified pointer to type T.
6950 <p><a name="6.7.3.1p2" href="#6.7.3.1p2"><small>2</small></a>
6951 If D appears inside a block and does not have storage class extern, let B denote the
6952 block. If D appears in the list of parameter declarations of a function definition, let B
6953 denote the associated block. Otherwise, let B denote the block of main (or the block of
6954 whatever function is called at program startup in a freestanding environment).
6955 <p><a name="6.7.3.1p3" href="#6.7.3.1p3"><small>3</small></a>
6956 In what follows, a pointer expression E is said to be based on object P if (at some
6957 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
6958 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note137"><b>137)</b></a></sup>
6959 Note that ''based'' is defined only for expressions with pointer types.
6960 <p><a name="6.7.3.1p4" href="#6.7.3.1p4"><small>4</small></a>
6961 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
6962 access the value of the object X that it designates, and X is also modified (by any means),
6963 then the following requirements apply: T shall not be const-qualified. Every other lvalue
6964 used to access the value of X shall also have its address based on P. Every access that
6965 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
6966 is assigned the value of a pointer expression E that is based on another restricted pointer
6970 object P2, associated with block B2, then either the execution of B2 shall begin before
6971 the execution of B, or the execution of B2 shall end prior to the assignment. If these
6972 requirements are not met, then the behavior is undefined.
6973 <p><a name="6.7.3.1p5" href="#6.7.3.1p5"><small>5</small></a>
6974 Here an execution of B means that portion of the execution of the program that would
6975 correspond to the lifetime of an object with scalar type and automatic storage duration
6977 <p><a name="6.7.3.1p6" href="#6.7.3.1p6"><small>6</small></a>
6978 A translator is free to ignore any or all aliasing implications of uses of restrict.
6979 <p><a name="6.7.3.1p7" href="#6.7.3.1p7"><small>7</small></a>
6980 EXAMPLE 1 The file scope declarations
6986 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
6987 program, then it is never accessed using either of the other two.
6989 <p><a name="6.7.3.1p8" href="#6.7.3.1p8"><small>8</small></a>
6990 EXAMPLE 2 The function parameter declarations in the following example
6992 void f(int n, int * restrict p, int * restrict q)
6998 assert that, during each execution of the function, if an object is accessed through one of the pointer
6999 parameters, then it is not also accessed through the other.
7000 <p><a name="6.7.3.1p9" href="#6.7.3.1p9"><small>9</small></a>
7001 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
7002 analysis of function f without examining any of the calls of f in the program. The cost is that the
7003 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
7004 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
7010 f(50, d + 50, d); // valid
7011 f(50, d + 1, d); // undefined behavior
7015 <p><a name="6.7.3.1p10" href="#6.7.3.1p10"><small>10</small></a>
7016 EXAMPLE 3 The function parameter declarations
7018 void h(int n, int * restrict p, int * restrict q, int * restrict r)
7021 for (i = 0; i < n; i++)
7025 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
7026 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
7027 modified within function h.
7029 <p><a name="6.7.3.1p11" href="#6.7.3.1p11"><small>11</small></a>
7030 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
7031 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
7032 between restricted pointers declared in nested blocks have defined behavior.
7037 p1 = q1; // undefined behavior
7039 int * restrict p2 = p1; // valid
7040 int * restrict q2 = q1; // valid
7041 p1 = q2; // undefined behavior
7042 p2 = q2; // undefined behavior
7046 <p><a name="6.7.3.1p12" href="#6.7.3.1p12"><small>12</small></a>
7047 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
7048 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
7049 example, this permits new_vector to return a vector.
7051 typedef struct { int n; float * restrict v; } vector;
7052 vector new_vector(int n)
7056 t.v = malloc(n * sizeof (float));
7063 <p><small><a name="note137" href="#note137">137)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
7064 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
7065 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
7066 expressions *p and p[1] are not.
7069 <p><small><a href="#Contents">Contents</a></small>
7070 <h4><a name="6.7.4" href="#6.7.4">6.7.4 Function specifiers</a></h4>
7072 <p><a name="6.7.4p1" href="#6.7.4p1"><small>1</small></a>
7078 <p><b>Constraints</b>
7079 <p><a name="6.7.4p2" href="#6.7.4p2"><small>2</small></a>
7080 Function specifiers shall be used only in the declaration of an identifier for a function.
7081 <p><a name="6.7.4p3" href="#6.7.4p3"><small>3</small></a>
7082 An inline definition of a function with external linkage shall not contain a definition of a
7083 modifiable object with static or thread storage duration, and shall not contain a reference
7084 to an identifier with internal linkage.
7085 <p><a name="6.7.4p4" href="#6.7.4p4"><small>4</small></a>
7086 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
7088 <p><a name="6.7.4p5" href="#6.7.4p5"><small>5</small></a>
7089 A function specifier may appear more than once; the behavior is the same as if it
7091 <p><a name="6.7.4p6" href="#6.7.4p6"><small>6</small></a>
7092 A function declared with an inline function specifier is an inline function. Making a
7093 function an inline function suggests that calls to the function be as fast as possible.<sup><a href="#note138"><b>138)</b></a></sup>
7095 The extent to which such suggestions are effective is implementation-defined.<sup><a href="#note139"><b>139)</b></a></sup>
7096 <p><a name="6.7.4p7" href="#6.7.4p7"><small>7</small></a>
7097 Any function with internal linkage can be an inline function. For a function with external
7098 linkage, the following restrictions apply: If a function is declared with an inline
7099 function specifier, then it shall also be defined in the same translation unit. If all of the
7100 file scope declarations for a function in a translation unit include the inline function
7101 specifier without extern, then the definition in that translation unit is an inline
7102 definition. An inline definition does not provide an external definition for the function,
7103 and does not forbid an external definition in another translation unit. An inline definition
7104 provides an alternative to an external definition, which a translator may use to implement
7105 any call to the function in the same translation unit. It is unspecified whether a call to the
7106 function uses the inline definition or the external definition.<sup><a href="#note140"><b>140)</b></a></sup>
7107 <p><a name="6.7.4p8" href="#6.7.4p8"><small>8</small></a>
7108 A function declared with a _Noreturn function specifier shall not return to its caller.
7109 <p><b>Recommended practice</b>
7110 <p><a name="6.7.4p9" href="#6.7.4p9"><small>9</small></a>
7111 The implementation should produce a diagnostic message for a function declared with a
7112 _Noreturn function specifier that appears to be capable of returning to its caller.
7113 <p><a name="6.7.4p10" href="#6.7.4p10"><small>10</small></a>
7114 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
7115 definition, or a definition available for use only within the translation unit. A file scope declaration with
7116 extern creates an external definition. The following example shows an entire translation unit.
7118 inline double fahr(double t)
7120 return (9.0 * t) / 5.0 + 32.0;
7122 inline double cels(double t)
7124 return (5.0 * (t - 32.0)) / 9.0;
7126 extern double fahr(double); // creates an external definition
7134 double convert(int is_fahr, double temp)
7136 /* A translator may perform inline substitutions */
7137 return is_fahr ? cels(temp) : fahr(temp);
7140 <p><a name="6.7.4p11" href="#6.7.4p11"><small>11</small></a>
7141 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
7142 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
7143 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
7144 definition are distinct and either may be used for the call.
7146 <p><a name="6.7.4p12" href="#6.7.4p12"><small>12</small></a>
7149 _Noreturn void f () {
7152 _Noreturn void g (int i) { // causes undefined behavior if i <= 0
7153 if (i > 0) abort();
7157 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
7160 <p><small><a name="note138" href="#note138">138)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
7161 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
7162 Therefore, for example, the expansion of a macro used within the body of the function uses the
7163 definition it had at the point the function body appears, and not where the function is called; and
7164 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
7165 single address, regardless of the number of inline definitions that occur in addition to the external
7168 <p><small><a name="note139" href="#note139">139)</a> For example, an implementation might never perform inline substitution, or might only perform inline
7169 substitutions to calls in the scope of an inline declaration.
7171 <p><small><a name="note140" href="#note140">140)</a> Since an inline definition is distinct from the corresponding external definition and from any other
7172 corresponding inline definitions in other translation units, all corresponding objects with static storage
7173 duration are also distinct in each of the definitions.
7176 <p><small><a href="#Contents">Contents</a></small>
7177 <h4><a name="6.7.5" href="#6.7.5">6.7.5 Alignment specifier</a></h4>
7179 <p><a name="6.7.5p1" href="#6.7.5p1"><small>1</small></a>
7181 alignment-specifier:
7182 _Alignas ( type-name )
7183 _Alignas ( constant-expression )
7185 <p><b>Constraints</b>
7186 <p><a name="6.7.5p2" href="#6.7.5p2"><small>2</small></a>
7187 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
7188 a function, or a parameter, or an object declared with the register storage-class
7190 <p><a name="6.7.5p3" href="#6.7.5p3"><small>3</small></a>
7191 The constant expression shall be an integer constant expression. It shall evaluate to a
7192 valid fundamental alignment, or to a valid extended alignment supported by the
7193 implementation in the context in which it appears, or to zero.
7194 <p><a name="6.7.5p4" href="#6.7.5p4"><small>4</small></a>
7195 The combined effect of all alignment attributes in a declaration shall not specify an
7196 alignment that is less strict than the alignment that would otherwise be required for the
7197 type of the object or member being declared.
7199 <p><a name="6.7.5p5" href="#6.7.5p5"><small>5</small></a>
7200 The first form is equivalent to _Alignas (_Alignof (type-name)).
7201 <p><a name="6.7.5p6" href="#6.7.5p6"><small>6</small></a>
7202 The alignment requirement of the declared object or member is taken to be the specified
7203 alignment. An alignment specification of zero has no effect.<sup><a href="#note141"><b>141)</b></a></sup> When multiple
7204 alignment specifiers occur in a declaration, the effective alignment requirement is the
7205 strictest specified alignment.
7207 <p><a name="6.7.5p7" href="#6.7.5p7"><small>7</small></a>
7208 If the definition of an object has an alignment specifier, any other declaration of that
7209 object shall either specify equivalent alignment or have no alignment specifier. If the
7210 definition of an object does not have an alignment specifier, any other declaration of that
7211 object shall also have no alignment specifier. If declarations of an object in different
7212 translation units have different alignment specifiers, the behavior is undefined.
7215 <p><small><a name="note141" href="#note141">141)</a> An alignment specification of zero also does not affect other alignment specifications in the same
7219 <p><small><a href="#Contents">Contents</a></small>
7220 <h4><a name="6.7.6" href="#6.7.6">6.7.6 Declarators</a></h4>
7222 <p><a name="6.7.6p1" href="#6.7.6p1"><small>1</small></a>
7225 pointer<sub>opt</sub> direct-declarator
7229 direct-declarator [ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
7230 direct-declarator [ static type-qualifier-list<sub>opt</sub> assignment-expression ]
7231 direct-declarator [ type-qualifier-list static assignment-expression ]
7232 direct-declarator [ type-qualifier-list<sub>opt</sub> * ]
7233 direct-declarator ( parameter-type-list )
7234 direct-declarator ( identifier-list<sub>opt</sub> )
7236 * type-qualifier-list<sub>opt</sub>
7237 * type-qualifier-list<sub>opt</sub> pointer
7238 type-qualifier-list:
7240 type-qualifier-list type-qualifier
7241 parameter-type-list:
7243 parameter-list , ...
7245 parameter-declaration
7246 parameter-list , parameter-declaration
7247 parameter-declaration:
7248 declaration-specifiers declarator
7249 declaration-specifiers abstract-declarator<sub>opt</sub>
7258 identifier-list , identifier
7261 <p><a name="6.7.6p2" href="#6.7.6p2"><small>2</small></a>
7262 Each declarator declares one identifier, and asserts that when an operand of the same
7263 form as the declarator appears in an expression, it designates a function or object with the
7264 scope, storage duration, and type indicated by the declaration specifiers.
7265 <p><a name="6.7.6p3" href="#6.7.6p3"><small>3</small></a>
7266 A full declarator is a declarator that is not part of another declarator. The end of a full
7267 declarator is a sequence point. If, in the nested sequence of declarators in a full
7268 declarator, there is a declarator specifying a variable length array type, the type specified
7269 by the full declarator is said to be variably modified. Furthermore, any type derived by
7270 declarator type derivation from a variably modified type is itself variably modified.
7271 <p><a name="6.7.6p4" href="#6.7.6p4"><small>4</small></a>
7272 In the following subclauses, consider a declaration
7276 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
7277 a declarator that contains an identifier ident. The type specified for the identifier ident in
7278 the various forms of declarator is described inductively using this notation.
7279 <p><a name="6.7.6p5" href="#6.7.6p5"><small>5</small></a>
7280 If, in the declaration ''T D1'', D1 has the form
7284 then the type specified for ident is T .
7285 <p><a name="6.7.6p6" href="#6.7.6p6"><small>6</small></a>
7286 If, in the declaration ''T D1'', D1 has the form
7290 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
7291 parentheses is identical to the unparenthesized declarator, but the binding of complicated
7292 declarators may be altered by parentheses.
7293 <p><b>Implementation limits</b>
7294 <p><a name="6.7.6p7" href="#6.7.6p7"><small>7</small></a>
7295 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
7296 function declarators that modify an arithmetic, structure, union, or void type, either
7297 directly or via one or more typedefs.
7298 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
7301 <p><small><a href="#Contents">Contents</a></small>
7302 <h5><a name="6.7.6.1" href="#6.7.6.1">6.7.6.1 Pointer declarators</a></h5>
7304 <p><a name="6.7.6.1p1" href="#6.7.6.1p1"><small>1</small></a>
7305 If, in the declaration ''T D1'', D1 has the form
7307 * type-qualifier-list<sub>opt</sub> D
7309 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7310 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
7311 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
7312 <p><a name="6.7.6.1p2" href="#6.7.6.1p2"><small>2</small></a>
7313 For two pointer types to be compatible, both shall be identically qualified and both shall
7314 be pointers to compatible types.
7315 <p><a name="6.7.6.1p3" href="#6.7.6.1p3"><small>3</small></a>
7316 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
7317 to a constant value'' and a ''constant pointer to a variable value''.
7319 const int *ptr_to_constant;
7320 int *const constant_ptr;
7322 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
7323 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
7324 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
7326 <p><a name="6.7.6.1p4" href="#6.7.6.1p4"><small>4</small></a>
7327 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
7328 type ''pointer to int''.
7330 typedef int *int_ptr;
7331 const int_ptr constant_ptr;
7333 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
7336 <p><small><a href="#Contents">Contents</a></small>
7337 <h5><a name="6.7.6.2" href="#6.7.6.2">6.7.6.2 Array declarators</a></h5>
7338 <p><b>Constraints</b>
7339 <p><a name="6.7.6.2p1" href="#6.7.6.2p1"><small>1</small></a>
7340 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
7341 an expression or *. If they delimit an expression (which specifies the size of an array), the
7342 expression shall have an integer type. If the expression is a constant expression, it shall
7343 have a value greater than zero. The element type shall not be an incomplete or function
7344 type. The optional type qualifiers and the keyword static shall appear only in a
7345 declaration of a function parameter with an array type, and then only in the outermost
7346 array type derivation.
7347 <p><a name="6.7.6.2p2" href="#6.7.6.2p2"><small>2</small></a>
7348 If an identifier is declared as having a variably modified type, it shall be an ordinary
7349 identifier (as defined in <a href="#6.2.3">6.2.3</a>), have no linkage, and have either block scope or function
7350 prototype scope. If an identifier is declared to be an object with static or thread storage
7351 duration, it shall not have a variable length array type.
7354 <p><a name="6.7.6.2p3" href="#6.7.6.2p3"><small>3</small></a>
7355 If, in the declaration ''T D1'', D1 has one of the forms:
7357 D[ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
7358 D[ static type-qualifier-list<sub>opt</sub> assignment-expression ]
7359 D[ type-qualifier-list static assignment-expression ]
7360 D[ type-qualifier-list<sub>opt</sub> * ]
7362 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7363 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note142"><b>142)</b></a></sup>
7364 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
7365 <p><a name="6.7.6.2p4" href="#6.7.6.2p4"><small>4</small></a>
7366 If the size is not present, the array type is an incomplete type. If the size is * instead of
7367 being an expression, the array type is a variable length array type of unspecified size,
7368 which can only be used in declarations or type names with function prototype scope;<sup><a href="#note143"><b>143)</b></a></sup>
7369 such arrays are nonetheless complete types. If the size is an integer constant expression
7370 and the element type has a known constant size, the array type is not a variable length
7371 array type; otherwise, the array type is a variable length array type. (Variable length
7372 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
7373 <p><a name="6.7.6.2p5" href="#6.7.6.2p5"><small>5</small></a>
7374 If the size is an expression that is not an integer constant expression: if it occurs in a
7375 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
7376 each time it is evaluated it shall have a value greater than zero. The size of each instance
7377 of a variable length array type does not change during its lifetime. Where a size
7378 expression is part of the operand of a sizeof operator and changing the value of the
7379 size expression would not affect the result of the operator, it is unspecified whether or not
7380 the size expression is evaluated.
7381 <p><a name="6.7.6.2p6" href="#6.7.6.2p6"><small>6</small></a>
7382 For two array types to be compatible, both shall have compatible element types, and if
7383 both size specifiers are present, and are integer constant expressions, then both size
7384 specifiers shall have the same constant value. If the two array types are used in a context
7385 which requires them to be compatible, it is undefined behavior if the two size specifiers
7386 evaluate to unequal values.
7387 <p><a name="6.7.6.2p7" href="#6.7.6.2p7"><small>7</small></a>
7390 float fa[11], *afp[17];
7392 declares an array of float numbers and an array of pointers to float numbers.
7394 <p><a name="6.7.6.2p8" href="#6.7.6.2p8"><small>8</small></a>
7395 EXAMPLE 2 Note the distinction between the declarations
7405 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
7406 (an incomplete type), the storage for which is defined elsewhere.
7408 <p><a name="6.7.6.2p9" href="#6.7.6.2p9"><small>9</small></a>
7409 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
7418 int (*r)[n][n][n+1];
7419 p = a; // invalid: not compatible because 4 != 6
7420 r = c; // compatible, but defined behavior only if
7421 // n == 6 and m == n+1
7425 <p><a name="6.7.6.2p10" href="#6.7.6.2p10"><small>10</small></a>
7426 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
7427 function prototype scope. Array objects declared with the _Thread_local, static, or extern
7428 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
7429 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
7430 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
7431 structures or unions.
7434 int A[n]; // invalid: file scope VLA
7435 extern int (*p2)[n]; // invalid: file scope VM
7436 int B[100]; // valid: file scope but not VM
7437 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
7438 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
7440 typedef int VLA[m][m]; // valid: block scope typedef VLA
7442 int (*y)[n]; // invalid: y not ordinary identifier
7443 int z[n]; // invalid: z not ordinary identifier
7445 int D[m]; // valid: auto VLA
7446 static int E[m]; // invalid: static block scope VLA
7447 extern int F[m]; // invalid: F has linkage and is VLA
7448 int (*s)[m]; // valid: auto pointer to VLA
7449 extern int (*r)[m]; // invalid: r has linkage and points to VLA
7450 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
7454 <p><b> Forward references</b>: function declarators (<a href="#6.7.6.3">6.7.6.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
7455 initialization (<a href="#6.7.9">6.7.9</a>).
7459 <p><small><a name="note142" href="#note142">142)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
7461 <p><small><a name="note143" href="#note143">143)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.6.3">6.7.6.3</a>).
7464 <p><small><a href="#Contents">Contents</a></small>
7465 <h5><a name="6.7.6.3" href="#6.7.6.3">6.7.6.3 Function declarators (including prototypes)</a></h5>
7466 <p><b>Constraints</b>
7467 <p><a name="6.7.6.3p1" href="#6.7.6.3p1"><small>1</small></a>
7468 A function declarator shall not specify a return type that is a function type or an array
7470 <p><a name="6.7.6.3p2" href="#6.7.6.3p2"><small>2</small></a>
7471 The only storage-class specifier that shall occur in a parameter declaration is register.
7472 <p><a name="6.7.6.3p3" href="#6.7.6.3p3"><small>3</small></a>
7473 An identifier list in a function declarator that is not part of a definition of that function
7475 <p><a name="6.7.6.3p4" href="#6.7.6.3p4"><small>4</small></a>
7476 After adjustment, the parameters in a parameter type list in a function declarator that is
7477 part of a definition of that function shall not have incomplete type.
7479 <p><a name="6.7.6.3p5" href="#6.7.6.3p5"><small>5</small></a>
7480 If, in the declaration ''T D1'', D1 has the form
7482 D( parameter-type-list )
7486 D( identifier-list<sub>opt</sub> )
7488 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7489 T '', then the type specified for ident is ''derived-declarator-type-list function returning
7491 <p><a name="6.7.6.3p6" href="#6.7.6.3p6"><small>6</small></a>
7492 A parameter type list specifies the types of, and may declare identifiers for, the
7493 parameters of the function.
7494 <p><a name="6.7.6.3p7" href="#6.7.6.3p7"><small>7</small></a>
7495 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
7496 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
7497 array type derivation. If the keyword static also appears within the [ and ] of the
7498 array type derivation, then for each call to the function, the value of the corresponding
7499 actual argument shall provide access to the first element of an array with at least as many
7500 elements as specified by the size expression.
7501 <p><a name="6.7.6.3p8" href="#6.7.6.3p8"><small>8</small></a>
7502 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
7503 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
7504 <p><a name="6.7.6.3p9" href="#6.7.6.3p9"><small>9</small></a>
7505 If the list terminates with an ellipsis (, ...), no information about the number or types
7506 of the parameters after the comma is supplied.<sup><a href="#note144"><b>144)</b></a></sup>
7507 <p><a name="6.7.6.3p10" href="#6.7.6.3p10"><small>10</small></a>
7508 The special case of an unnamed parameter of type void as the only item in the list
7509 specifies that the function has no parameters.
7514 <p><a name="6.7.6.3p11" href="#6.7.6.3p11"><small>11</small></a>
7515 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
7516 parameter name, it shall be taken as a typedef name.
7517 <p><a name="6.7.6.3p12" href="#6.7.6.3p12"><small>12</small></a>
7518 If the function declarator is not part of a definition of that function, parameters may have
7519 incomplete type and may use the [*] notation in their sequences of declarator specifiers
7520 to specify variable length array types.
7521 <p><a name="6.7.6.3p13" href="#6.7.6.3p13"><small>13</small></a>
7522 The storage-class specifier in the declaration specifiers for a parameter declaration, if
7523 present, is ignored unless the declared parameter is one of the members of the parameter
7524 type list for a function definition.
7525 <p><a name="6.7.6.3p14" href="#6.7.6.3p14"><small>14</small></a>
7526 An identifier list declares only the identifiers of the parameters of the function. An empty
7527 list in a function declarator that is part of a definition of that function specifies that the
7528 function has no parameters. The empty list in a function declarator that is not part of a
7529 definition of that function specifies that no information about the number or types of the
7530 parameters is supplied.<sup><a href="#note145"><b>145)</b></a></sup>
7531 <p><a name="6.7.6.3p15" href="#6.7.6.3p15"><small>15</small></a>
7532 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note146"><b>146)</b></a></sup>
7533 Moreover, the parameter type lists, if both are present, shall agree in the number of
7534 parameters and in use of the ellipsis terminator; corresponding parameters shall have
7535 compatible types. If one type has a parameter type list and the other type is specified by a
7536 function declarator that is not part of a function definition and that contains an empty
7537 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
7538 parameter shall be compatible with the type that results from the application of the
7539 default argument promotions. If one type has a parameter type list and the other type is
7540 specified by a function definition that contains a (possibly empty) identifier list, both shall
7541 agree in the number of parameters, and the type of each prototype parameter shall be
7542 compatible with the type that results from the application of the default argument
7543 promotions to the type of the corresponding identifier. (In the determination of type
7544 compatibility and of a composite type, each parameter declared with function or array
7545 type is taken as having the adjusted type and each parameter declared with qualified type
7546 is taken as having the unqualified version of its declared type.)
7547 <p><a name="6.7.6.3p16" href="#6.7.6.3p16"><small>16</small></a>
7548 EXAMPLE 1 The declaration
7550 int f(void), *fip(), (*pfi)();
7552 declares a function f with no parameters returning an int, a function fip with no parameter specification
7553 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
7554 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
7555 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
7556 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
7557 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
7561 designator, which is then used to call the function; it returns an int.
7562 <p><a name="6.7.6.3p17" href="#6.7.6.3p17"><small>17</small></a>
7563 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
7564 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
7565 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
7566 the identifier of the pointer pfi has block scope and no linkage.
7568 <p><a name="6.7.6.3p18" href="#6.7.6.3p18"><small>18</small></a>
7569 EXAMPLE 2 The declaration
7571 int (*apfi[3])(int *x, int *y);
7573 declares an array apfi of three pointers to functions returning int. Each of these functions has two
7574 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
7575 go out of scope at the end of the declaration of apfi.
7577 <p><a name="6.7.6.3p19" href="#6.7.6.3p19"><small>19</small></a>
7578 EXAMPLE 3 The declaration
7580 int (*fpfi(int (*)(long), int))(int, ...);
7582 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
7583 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
7584 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
7585 additional arguments of any type.
7587 <p><a name="6.7.6.3p20" href="#6.7.6.3p20"><small>20</small></a>
7588 EXAMPLE 4 The following prototype has a variably modified parameter.
7590 void addscalar(int n, int m,
7591 double a[n][n*m+300], double x);
7595 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
7598 void addscalar(int n, int m,
7599 double a[n][n*m+300], double x)
7601 for (int i = 0; i < n; i++)
7602 for (int j = 0, k = n*m+300; j < k; j++)
7603 // a is a pointer to a VLA with n*m+300 elements
7608 <p><a name="6.7.6.3p21" href="#6.7.6.3p21"><small>21</small></a>
7609 EXAMPLE 5 The following are all compatible function prototype declarators.
7611 double maximum(int n, int m, double a[n][m]);
7612 double maximum(int n, int m, double a[*][*]);
7613 double maximum(int n, int m, double a[ ][*]);
7614 double maximum(int n, int m, double a[ ][m]);
7619 void f(double (* restrict a)[5]);
7620 void f(double a[restrict][5]);
7621 void f(double a[restrict 3][5]);
7622 void f(double a[restrict static 3][5]);
7624 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
7625 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
7627 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
7630 <p><small><a name="note144" href="#note144">144)</a> The macros defined in the <a href="#7.16"><stdarg.h></a> header (<a href="#7.16">7.16</a>) may be used to access arguments that
7631 correspond to the ellipsis.
7633 <p><small><a name="note145" href="#note145">145)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
7635 <p><small><a name="note146" href="#note146">146)</a> If both function types are ''old style'', parameter types are not compared.
7638 <p><small><a href="#Contents">Contents</a></small>
7639 <h4><a name="6.7.7" href="#6.7.7">6.7.7 Type names</a></h4>
7641 <p><a name="6.7.7p1" href="#6.7.7p1"><small>1</small></a>
7644 specifier-qualifier-list abstract-declarator<sub>opt</sub>
7645 abstract-declarator:
7647 pointer<sub>opt</sub> direct-abstract-declarator
7648 direct-abstract-declarator:
7649 ( abstract-declarator )
7650 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list<sub>opt</sub>
7651 assignment-expression<sub>opt</sub> ]
7652 direct-abstract-declarator<sub>opt</sub> [ static type-qualifier-list<sub>opt</sub>
7653 assignment-expression ]
7654 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list static
7655 assignment-expression ]
7656 direct-abstract-declarator<sub>opt</sub> [ * ]
7657 direct-abstract-declarator<sub>opt</sub> ( parameter-type-list<sub>opt</sub> )
7660 <p><a name="6.7.7p2" href="#6.7.7p2"><small>2</small></a>
7661 In several contexts, it is necessary to specify a type. This is accomplished using a type
7662 name, which is syntactically a declaration for a function or an object of that type that
7663 omits the identifier.<sup><a href="#note147"><b>147)</b></a></sup>
7664 <p><a name="6.7.7p3" href="#6.7.7p3"><small>3</small></a>
7665 EXAMPLE The constructions
7674 (h) int (*const [])(unsigned int, ...)
7676 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
7677 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
7678 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
7682 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
7683 parameter that has type unsigned int and an unspecified number of other parameters, returning an
7688 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
7689 parameter specification'', rather than redundant parentheses around the omitted identifier.
7692 <p><small><a href="#Contents">Contents</a></small>
7693 <h4><a name="6.7.8" href="#6.7.8">6.7.8 Type definitions</a></h4>
7695 <p><a name="6.7.8p1" href="#6.7.8p1"><small>1</small></a>
7700 <p><b>Constraints</b>
7701 <p><a name="6.7.8p2" href="#6.7.8p2"><small>2</small></a>
7702 If a typedef name specifies a variably modified type then it shall have block scope.
7704 <p><a name="6.7.8p3" href="#6.7.8p3"><small>3</small></a>
7705 In a declaration whose storage-class specifier is typedef, each declarator defines an
7706 identifier to be a typedef name that denotes the type specified for the identifier in the way
7707 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
7708 declarators are evaluated each time the declaration of the typedef name is reached in the
7709 order of execution. A typedef declaration does not introduce a new type, only a
7710 synonym for the type so specified. That is, in the following declarations:
7712 typedef T type_ident;
7715 type_ident is defined as a typedef name with the type specified by the declaration
7716 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
7717 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
7718 typedef name shares the same name space as other identifiers declared in ordinary
7720 <p><a name="6.7.8p4" href="#6.7.8p4"><small>4</small></a>
7723 typedef int MILES, KLICKSP();
7724 typedef struct { double hi, lo; } range;
7729 extern KLICKSP *metricp;
7733 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
7734 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
7735 such a structure. The object distance has a type compatible with any other int object.
7737 <p><a name="6.7.8p5" href="#6.7.8p5"><small>5</small></a>
7738 EXAMPLE 2 After the declarations
7740 typedef struct s1 { int x; } t1, *tp1;
7741 typedef struct s2 { int x; } t2, *tp2;
7743 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
7745 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
7747 <p><a name="6.7.8p6" href="#6.7.8p6"><small>6</small></a>
7748 EXAMPLE 3 The following obscure constructions
7750 typedef signed int t;
7758 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
7759 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
7760 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
7761 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
7762 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
7763 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
7764 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
7765 in an inner scope by
7770 then a function f is declared with type ''function returning signed int with one unnamed parameter
7771 with type pointer to function returning signed int with one unnamed parameter with type signed
7772 int'', and an identifier t with type long int.
7774 <p><a name="6.7.8p7" href="#6.7.8p7"><small>7</small></a>
7775 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
7776 following declarations of the signal function specify exactly the same type, the first without making use
7777 of any typedef names.
7779 typedef void fv(int), (*pfv)(int);
7780 void (*signal(int, void (*)(int)))(int);
7781 fv *signal(int, fv *);
7782 pfv signal(int, pfv);
7785 <p><a name="6.7.8p8" href="#6.7.8p8"><small>8</small></a>
7786 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
7787 time the typedef name is defined, not each time it is used:
7792 typedef int B[n]; // B is n ints, n evaluated now
7794 B a; // a is n ints, n without += 1
7795 int b[n]; // a and b are different sizes
7796 for (int i = 1; i < n; i++)
7801 <p><small><a href="#Contents">Contents</a></small>
7802 <h4><a name="6.7.9" href="#6.7.9">6.7.9 Initialization</a></h4>
7804 <p><a name="6.7.9p1" href="#6.7.9p1"><small>1</small></a>
7807 assignment-expression
7808 { initializer-list }
7809 { initializer-list , }
7811 designation<sub>opt</sub> initializer
7812 initializer-list , designation<sub>opt</sub> initializer
7817 designator-list designator
7819 [ constant-expression ]
7822 <p><b>Constraints</b>
7823 <p><a name="6.7.9p2" href="#6.7.9p2"><small>2</small></a>
7824 No initializer shall attempt to provide a value for an object not contained within the entity
7826 <p><a name="6.7.9p3" href="#6.7.9p3"><small>3</small></a>
7827 The type of the entity to be initialized shall be an array of unknown size or a complete
7828 object type that is not a variable length array type.
7829 <p><a name="6.7.9p4" href="#6.7.9p4"><small>4</small></a>
7830 All the expressions in an initializer for an object that has static or thread storage duration
7831 shall be constant expressions or string literals.
7832 <p><a name="6.7.9p5" href="#6.7.9p5"><small>5</small></a>
7833 If the declaration of an identifier has block scope, and the identifier has external or
7834 internal linkage, the declaration shall have no initializer for the identifier.
7835 <p><a name="6.7.9p6" href="#6.7.9p6"><small>6</small></a>
7836 If a designator has the form
7838 [ constant-expression ]
7840 then the current object (defined below) shall have array type and the expression shall be
7841 an integer constant expression. If the array is of unknown size, any nonnegative value is
7843 <p><a name="6.7.9p7" href="#6.7.9p7"><small>7</small></a>
7844 If a designator has the form
7848 then the current object (defined below) shall have structure or union type and the
7849 identifier shall be the name of a member of that type.
7852 <p><a name="6.7.9p8" href="#6.7.9p8"><small>8</small></a>
7853 An initializer specifies the initial value stored in an object.
7854 <p><a name="6.7.9p9" href="#6.7.9p9"><small>9</small></a>
7855 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
7856 members of objects of structure and union type do not participate in initialization.
7857 Unnamed members of structure objects have indeterminate value even after initialization.
7858 <p><a name="6.7.9p10" href="#6.7.9p10"><small>10</small></a>
7859 If an object that has automatic storage duration is not initialized explicitly, its value is
7860 indeterminate. If an object that has static or thread storage duration is not initialized
7863 <li> if it has pointer type, it is initialized to a null pointer;
7864 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
7865 <li> if it is an aggregate, every member is initialized (recursively) according to these rules,
7866 and any padding is initialized to zero bits;
7867 <li> if it is a union, the first named member is initialized (recursively) according to these
7868 rules, and any padding is initialized to zero bits;
7870 <p><a name="6.7.9p11" href="#6.7.9p11"><small>11</small></a>
7871 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
7872 initial value of the object is that of the expression (after conversion); the same type
7873 constraints and conversions as for simple assignment apply, taking the type of the scalar
7874 to be the unqualified version of its declared type.
7875 <p><a name="6.7.9p12" href="#6.7.9p12"><small>12</small></a>
7876 The rest of this subclause deals with initializers for objects that have aggregate or union
7878 <p><a name="6.7.9p13" href="#6.7.9p13"><small>13</small></a>
7879 The initializer for a structure or union object that has automatic storage duration shall be
7880 either an initializer list as described below, or a single expression that has compatible
7881 structure or union type. In the latter case, the initial value of the object, including
7882 unnamed members, is that of the expression.
7883 <p><a name="6.7.9p14" href="#6.7.9p14"><small>14</small></a>
7884 An array of character type may be initialized by a character string literal or UTF-8 string
7885 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
7886 terminating null character if there is room or if the array is of unknown size) initialize the
7887 elements of the array.
7888 <p><a name="6.7.9p15" href="#6.7.9p15"><small>15</small></a>
7889 An array with element type compatible with a qualified or unqualified version of
7890 wchar_t, char16_t, or char32_t may be initialized by a wide string literal with
7891 the corresponding encoding prefix (L, u, or U, respectively), optionally enclosed in
7892 braces. Successive wide characters of the wide string literal (including the terminating
7893 null wide character if there is room or if the array is of unknown size) initialize the
7894 elements of the array.
7895 <p><a name="6.7.9p16" href="#6.7.9p16"><small>16</small></a>
7896 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
7897 enclosed list of initializers for the elements or named members.
7899 <p><a name="6.7.9p17" href="#6.7.9p17"><small>17</small></a>
7900 Each brace-enclosed initializer list has an associated current object. When no
7901 designations are present, subobjects of the current object are initialized in order according
7902 to the type of the current object: array elements in increasing subscript order, structure
7903 members in declaration order, and the first named member of a union.<sup><a href="#note148"><b>148)</b></a></sup> In contrast, a
7904 designation causes the following initializer to begin initialization of the subobject
7905 described by the designator. Initialization then continues forward in order, beginning
7906 with the next subobject after that described by the designator.<sup><a href="#note149"><b>149)</b></a></sup>
7907 <p><a name="6.7.9p18" href="#6.7.9p18"><small>18</small></a>
7908 Each designator list begins its description with the current object associated with the
7909 closest surrounding brace pair. Each item in the designator list (in order) specifies a
7910 particular member of its current object and changes the current object for the next
7911 designator (if any) to be that member.<sup><a href="#note150"><b>150)</b></a></sup> The current object that results at the end of the
7912 designator list is the subobject to be initialized by the following initializer.
7913 <p><a name="6.7.9p19" href="#6.7.9p19"><small>19</small></a>
7914 The initialization shall occur in initializer list order, each initializer provided for a
7915 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note151"><b>151)</b></a></sup>
7916 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
7917 objects that have static storage duration.
7918 <p><a name="6.7.9p20" href="#6.7.9p20"><small>20</small></a>
7919 If the aggregate or union contains elements or members that are aggregates or unions,
7920 these rules apply recursively to the subaggregates or contained unions. If the initializer of
7921 a subaggregate or contained union begins with a left brace, the initializers enclosed by
7922 that brace and its matching right brace initialize the elements or members of the
7923 subaggregate or the contained union. Otherwise, only enough initializers from the list are
7924 taken to account for the elements or members of the subaggregate or the first member of
7925 the contained union; any remaining initializers are left to initialize the next element or
7926 member of the aggregate of which the current subaggregate or contained union is a part.
7927 <p><a name="6.7.9p21" href="#6.7.9p21"><small>21</small></a>
7928 If there are fewer initializers in a brace-enclosed list than there are elements or members
7929 of an aggregate, or fewer characters in a string literal used to initialize an array of known
7930 size than there are elements in the array, the remainder of the aggregate shall be
7931 initialized implicitly the same as objects that have static storage duration.
7936 <p><a name="6.7.9p22" href="#6.7.9p22"><small>22</small></a>
7937 If an array of unknown size is initialized, its size is determined by the largest indexed
7938 element with an explicit initializer. The array type is completed at the end of its
7940 <p><a name="6.7.9p23" href="#6.7.9p23"><small>23</small></a>
7941 The evaluations of the initialization list expressions are indeterminately sequenced with
7942 respect to one another and thus the order in which any side effects occur is
7943 unspecified.<sup><a href="#note152"><b>152)</b></a></sup>
7944 <p><a name="6.7.9p24" href="#6.7.9p24"><small>24</small></a>
7945 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
7947 int i = <a href="#3.5">3.5</a>;
7948 double complex c = 5 + 3 * I;
7950 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
7952 <p><a name="6.7.9p25" href="#6.7.9p25"><small>25</small></a>
7953 EXAMPLE 2 The declaration
7955 int x[] = { 1, 3, 5 };
7957 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
7958 and there are three initializers.
7960 <p><a name="6.7.9p26" href="#6.7.9p26"><small>26</small></a>
7961 EXAMPLE 3 The declaration
7969 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
7970 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
7971 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
7975 1, 3, 5, 2, 4, 6, 3, 5, 7
7978 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
7979 next three are taken successively for y[1] and y[2].
7981 <p><a name="6.7.9p27" href="#6.7.9p27"><small>27</small></a>
7982 EXAMPLE 4 The declaration
7985 { 1 }, { 2 }, { 3 }, { 4 }
7988 initializes the first column of z as specified and initializes the rest with zeros.
7990 <p><a name="6.7.9p28" href="#6.7.9p28"><small>28</small></a>
7991 EXAMPLE 5 The declaration
7993 struct { int a[3], b; } w[] = { { 1 }, 2 };
7995 is a definition with an inconsistently bracketed initialization. It defines an array with two element
8000 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
8002 <p><a name="6.7.9p29" href="#6.7.9p29"><small>29</small></a>
8003 EXAMPLE 6 The declaration
8005 short q[4][3][2] = {
8011 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
8012 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
8013 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
8014 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
8015 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
8016 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
8017 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
8018 diagnostic message would have been issued. The same initialization result could have been achieved by:
8020 short q[4][3][2] = {
8028 short q[4][3][2] = {
8041 in a fully bracketed form.
8042 <p><a name="6.7.9p30" href="#6.7.9p30"><small>30</small></a>
8043 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
8046 <p><a name="6.7.9p31" href="#6.7.9p31"><small>31</small></a>
8047 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
8050 typedef int A[]; // OK - declared with block scope
8054 A a = { 1, 2 }, b = { 3, 4, 5 };
8058 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
8060 due to the rules for incomplete types.
8062 <p><a name="6.7.9p32" href="#6.7.9p32"><small>32</small></a>
8063 EXAMPLE 8 The declaration
8065 char s[] = "abc", t[3] = "abc";
8067 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
8068 This declaration is identical to
8070 char s[] = { 'a', 'b', 'c', '\0' },
8071 t[] = { 'a', 'b', 'c' };
8073 The contents of the arrays are modifiable. On the other hand, the declaration
8077 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
8078 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
8079 modify the contents of the array, the behavior is undefined.
8081 <p><a name="6.7.9p33" href="#6.7.9p33"><small>33</small></a>
8082 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
8085 enum { member_one, member_two };
8086 const char *nm[] = {
8087 [member_two] = "member two",
8088 [member_one] = "member one",
8092 <p><a name="6.7.9p34" href="#6.7.9p34"><small>34</small></a>
8093 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
8095 div_t answer = { .quot = 2, .rem = -1 };
8098 <p><a name="6.7.9p35" href="#6.7.9p35"><small>35</small></a>
8099 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
8100 might be misunderstood:
8102 struct { int a[3], b; } w[] =
8103 { [0].a = {1}, [1].a[0] = 2 };
8106 <p><a name="6.7.9p36" href="#6.7.9p36"><small>36</small></a>
8107 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
8110 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
8113 <p><a name="6.7.9p37" href="#6.7.9p37"><small>37</small></a>
8114 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
8115 than ten, some of the values provided by the first five initializers will be overridden by the second five.
8117 <p><a name="6.7.9p38" href="#6.7.9p38"><small>38</small></a>
8118 EXAMPLE 13 Any member of a union can be initialized:
8120 union { /* ... */ } u = { .any_member = 42 };
8123 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
8127 <p><small><a name="note148" href="#note148">148)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
8128 subobjects are initialized as usual, but the subaggregate or contained union does not become the
8129 current object: current objects are associated only with brace-enclosed initializer lists.
8131 <p><small><a name="note149" href="#note149">149)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
8132 the next subobject of an object containing the union.
8134 <p><small><a name="note150" href="#note150">150)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
8135 the surrounding brace pair. Note, too, that each separate designator list is independent.
8137 <p><small><a name="note151" href="#note151">151)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
8138 not be evaluated at all.
8140 <p><small><a name="note152" href="#note152">152)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
8143 <p><small><a href="#Contents">Contents</a></small>
8144 <h4><a name="6.7.10" href="#6.7.10">6.7.10 Static assertions</a></h4>
8146 <p><a name="6.7.10p1" href="#6.7.10p1"><small>1</small></a>
8148 static_assert-declaration:
8149 _Static_assert ( constant-expression , string-literal ) ;
8151 <p><b>Constraints</b>
8152 <p><a name="6.7.10p2" href="#6.7.10p2"><small>2</small></a>
8153 The constant expression shall compare unequal to 0.
8155 <p><a name="6.7.10p3" href="#6.7.10p3"><small>3</small></a>
8156 The constant expression shall be an integer constant expression. If the value of the
8157 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
8158 constraint is violated and the implementation shall produce a diagnostic message that
8159 includes the text of the string literal, except that characters not in the basic source
8160 character set are not required to appear in the message.
8161 <p><b> Forward references</b>: diagnostics (<a href="#7.2">7.2</a>).
8164 <p><small><a href="#Contents">Contents</a></small>
8165 <h3><a name="6.8" href="#6.8">6.8 Statements and blocks</a></h3>
8167 <p><a name="6.8p1" href="#6.8p1"><small>1</small></a>
8172 expression-statement
8178 <p><a name="6.8p2" href="#6.8p2"><small>2</small></a>
8179 A statement specifies an action to be performed. Except as indicated, statements are
8180 executed in sequence.
8181 <p><a name="6.8p3" href="#6.8p3"><small>3</small></a>
8182 A block allows a set of declarations and statements to be grouped into one syntactic unit.
8183 The initializers of objects that have automatic storage duration, and the variable length
8184 array declarators of ordinary identifiers with block scope, are evaluated and the values are
8185 stored in the objects (including storing an indeterminate value in objects without an
8186 initializer) each time the declaration is reached in the order of execution, as if it were a
8187 statement, and within each declaration in the order that declarators appear.
8188 <p><a name="6.8p4" href="#6.8p4"><small>4</small></a>
8189 A full expression is an expression that is not part of another expression or of a declarator.
8190 Each of the following is a full expression: an initializer that is not part of a compound
8191 literal; the expression in an expression statement; the controlling expression of a selection
8192 statement (if or switch); the controlling expression of a while or do statement; each
8193 of the (optional) expressions of a for statement; the (optional) expression in a return
8194 statement. There is a sequence point between the evaluation of a full expression and the
8195 evaluation of the next full expression to be evaluated.
8196 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
8197 (<a href="#6.8.4">6.8.4</a>), iteration statements (<a href="#6.8.5">6.8.5</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>).
8199 <p><small><a href="#Contents">Contents</a></small>
8200 <h4><a name="6.8.1" href="#6.8.1">6.8.1 Labeled statements</a></h4>
8202 <p><a name="6.8.1p1" href="#6.8.1p1"><small>1</small></a>
8205 identifier : statement
8206 case constant-expression : statement
8209 <p><b>Constraints</b>
8210 <p><a name="6.8.1p2" href="#6.8.1p2"><small>2</small></a>
8211 A case or default label shall appear only in a switch statement. Further
8212 constraints on such labels are discussed under the switch statement.
8214 <p><a name="6.8.1p3" href="#6.8.1p3"><small>3</small></a>
8215 Label names shall be unique within a function.
8217 <p><a name="6.8.1p4" href="#6.8.1p4"><small>4</small></a>
8218 Any statement may be preceded by a prefix that declares an identifier as a label name.
8219 Labels in themselves do not alter the flow of control, which continues unimpeded across
8221 <p><b> Forward references</b>: the goto statement (<a href="#6.8.6.1">6.8.6.1</a>), the switch statement (<a href="#6.8.4.2">6.8.4.2</a>).
8223 <p><small><a href="#Contents">Contents</a></small>
8224 <h4><a name="6.8.2" href="#6.8.2">6.8.2 Compound statement</a></h4>
8226 <p><a name="6.8.2p1" href="#6.8.2p1"><small>1</small></a>
8229 { block-item-list<sub>opt</sub> }
8232 block-item-list block-item
8238 <p><a name="6.8.2p2" href="#6.8.2p2"><small>2</small></a>
8239 A compound statement is a block.
8241 <p><small><a href="#Contents">Contents</a></small>
8242 <h4><a name="6.8.3" href="#6.8.3">6.8.3 Expression and null statements</a></h4>
8244 <p><a name="6.8.3p1" href="#6.8.3p1"><small>1</small></a>
8246 expression-statement:
8247 expression<sub>opt</sub> ;
8250 <p><a name="6.8.3p2" href="#6.8.3p2"><small>2</small></a>
8251 The expression in an expression statement is evaluated as a void expression for its side
8252 effects.<sup><a href="#note153"><b>153)</b></a></sup>
8253 <p><a name="6.8.3p3" href="#6.8.3p3"><small>3</small></a>
8254 A null statement (consisting of just a semicolon) performs no operations.
8255 <p><a name="6.8.3p4" href="#6.8.3p4"><small>4</small></a>
8256 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
8257 discarding of its value may be made explicit by converting the expression to a void expression by means of
8268 <p><a name="6.8.3p5" href="#6.8.3p5"><small>5</small></a>
8269 EXAMPLE 2 In the program fragment
8273 while (*s++ != '\0')
8276 a null statement is used to supply an empty loop body to the iteration statement.
8278 <p><a name="6.8.3p6" href="#6.8.3p6"><small>6</small></a>
8279 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
8295 <p><b> Forward references</b>: iteration statements (<a href="#6.8.5">6.8.5</a>).
8298 <p><small><a name="note153" href="#note153">153)</a> Such as assignments, and function calls which have side effects.
8301 <p><small><a href="#Contents">Contents</a></small>
8302 <h4><a name="6.8.4" href="#6.8.4">6.8.4 Selection statements</a></h4>
8304 <p><a name="6.8.4p1" href="#6.8.4p1"><small>1</small></a>
8306 selection-statement:
8307 if ( expression ) statement
8308 if ( expression ) statement else statement
8309 switch ( expression ) statement
8312 <p><a name="6.8.4p2" href="#6.8.4p2"><small>2</small></a>
8313 A selection statement selects among a set of statements depending on the value of a
8314 controlling expression.
8315 <p><a name="6.8.4p3" href="#6.8.4p3"><small>3</small></a>
8316 A selection statement is a block whose scope is a strict subset of the scope of its
8317 enclosing block. Each associated substatement is also a block whose scope is a strict
8318 subset of the scope of the selection statement.
8320 <p><small><a href="#Contents">Contents</a></small>
8321 <h5><a name="6.8.4.1" href="#6.8.4.1">6.8.4.1 The if statement</a></h5>
8322 <p><b>Constraints</b>
8323 <p><a name="6.8.4.1p1" href="#6.8.4.1p1"><small>1</small></a>
8324 The controlling expression of an if statement shall have scalar type.
8326 <p><a name="6.8.4.1p2" href="#6.8.4.1p2"><small>2</small></a>
8327 In both forms, the first substatement is executed if the expression compares unequal to 0.
8328 In the else form, the second substatement is executed if the expression compares equal
8330 to 0. If the first substatement is reached via a label, the second substatement is not
8332 <p><a name="6.8.4.1p3" href="#6.8.4.1p3"><small>3</small></a>
8333 An else is associated with the lexically nearest preceding if that is allowed by the
8336 <p><small><a href="#Contents">Contents</a></small>
8337 <h5><a name="6.8.4.2" href="#6.8.4.2">6.8.4.2 The switch statement</a></h5>
8338 <p><b>Constraints</b>
8339 <p><a name="6.8.4.2p1" href="#6.8.4.2p1"><small>1</small></a>
8340 The controlling expression of a switch statement shall have integer type.
8341 <p><a name="6.8.4.2p2" href="#6.8.4.2p2"><small>2</small></a>
8342 If a switch statement has an associated case or default label within the scope of an
8343 identifier with a variably modified type, the entire switch statement shall be within the
8344 scope of that identifier.<sup><a href="#note154"><b>154)</b></a></sup>
8345 <p><a name="6.8.4.2p3" href="#6.8.4.2p3"><small>3</small></a>
8346 The expression of each case label shall be an integer constant expression and no two of
8347 the case constant expressions in the same switch statement shall have the same value
8348 after conversion. There may be at most one default label in a switch statement.
8349 (Any enclosed switch statement may have a default label or case constant
8350 expressions with values that duplicate case constant expressions in the enclosing
8353 <p><a name="6.8.4.2p4" href="#6.8.4.2p4"><small>4</small></a>
8354 A switch statement causes control to jump to, into, or past the statement that is the
8355 switch body, depending on the value of a controlling expression, and on the presence of a
8356 default label and the values of any case labels on or in the switch body. A case or
8357 default label is accessible only within the closest enclosing switch statement.
8358 <p><a name="6.8.4.2p5" href="#6.8.4.2p5"><small>5</small></a>
8359 The integer promotions are performed on the controlling expression. The constant
8360 expression in each case label is converted to the promoted type of the controlling
8361 expression. If a converted value matches that of the promoted controlling expression,
8362 control jumps to the statement following the matched case label. Otherwise, if there is
8363 a default label, control jumps to the labeled statement. If no converted case constant
8364 expression matches and there is no default label, no part of the switch body is
8366 <p><b>Implementation limits</b>
8367 <p><a name="6.8.4.2p6" href="#6.8.4.2p6"><small>6</small></a>
8368 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, the implementation may limit the number of case values in a
8375 <p><a name="6.8.4.2p7" href="#6.8.4.2p7"><small>7</small></a>
8376 EXAMPLE In the artificial program fragment
8384 /* falls through into default code */
8389 the object whose identifier is i exists with automatic storage duration (within the block) but is never
8390 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
8391 access an indeterminate value. Similarly, the call to the function f cannot be reached.
8395 <p><small><a name="note154" href="#note154">154)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
8396 default label associated with the switch that is in the block containing the declaration.
8399 <p><small><a href="#Contents">Contents</a></small>
8400 <h4><a name="6.8.5" href="#6.8.5">6.8.5 Iteration statements</a></h4>
8402 <p><a name="6.8.5p1" href="#6.8.5p1"><small>1</small></a>
8404 iteration-statement:
8405 while ( expression ) statement
8406 do statement while ( expression ) ;
8407 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
8408 for ( declaration expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
8410 <p><b>Constraints</b>
8411 <p><a name="6.8.5p2" href="#6.8.5p2"><small>2</small></a>
8412 The controlling expression of an iteration statement shall have scalar type.
8413 <p><a name="6.8.5p3" href="#6.8.5p3"><small>3</small></a>
8414 The declaration part of a for statement shall only declare identifiers for objects having
8415 storage class auto or register.
8417 <p><a name="6.8.5p4" href="#6.8.5p4"><small>4</small></a>
8418 An iteration statement causes a statement called the loop body to be executed repeatedly
8419 until the controlling expression compares equal to 0. The repetition occurs regardless of
8420 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note155"><b>155)</b></a></sup>
8421 <p><a name="6.8.5p5" href="#6.8.5p5"><small>5</small></a>
8422 An iteration statement is a block whose scope is a strict subset of the scope of its
8423 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
8424 of the iteration statement.
8425 <p><a name="6.8.5p6" href="#6.8.5p6"><small>6</small></a>
8426 An iteration statement whose controlling expression is not a constant expression,<sup><a href="#note156"><b>156)</b></a></sup> that
8427 performs no input/output operations, does not access volatile objects, and performs no
8428 synchronization or atomic operations in its body, controlling expression, or (in the case of
8431 a for statement) its expression-3, may be assumed by the implementation to
8432 terminate.<sup><a href="#note157"><b>157)</b></a></sup>
8435 <p><small><a name="note155" href="#note155">155)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
8436 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
8438 <p><small><a name="note156" href="#note156">156)</a> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
8440 <p><small><a name="note157" href="#note157">157)</a> This is intended to allow compiler transformations such as removal of empty loops even when
8441 termination cannot be proven.
8444 <p><small><a href="#Contents">Contents</a></small>
8445 <h5><a name="6.8.5.1" href="#6.8.5.1">6.8.5.1 The while statement</a></h5>
8446 <p><a name="6.8.5.1p1" href="#6.8.5.1p1"><small>1</small></a>
8447 The evaluation of the controlling expression takes place before each execution of the loop
8450 <p><small><a href="#Contents">Contents</a></small>
8451 <h5><a name="6.8.5.2" href="#6.8.5.2">6.8.5.2 The do statement</a></h5>
8452 <p><a name="6.8.5.2p1" href="#6.8.5.2p1"><small>1</small></a>
8453 The evaluation of the controlling expression takes place after each execution of the loop
8456 <p><small><a href="#Contents">Contents</a></small>
8457 <h5><a name="6.8.5.3" href="#6.8.5.3">6.8.5.3 The for statement</a></h5>
8458 <p><a name="6.8.5.3p1" href="#6.8.5.3p1"><small>1</small></a>
8461 for ( clause-1 ; expression-2 ; expression-3 ) statement
8463 behaves as follows: The expression expression-2 is the controlling expression that is
8464 evaluated before each execution of the loop body. The expression expression-3 is
8465 evaluated as a void expression after each execution of the loop body. If clause-1 is a
8466 declaration, the scope of any identifiers it declares is the remainder of the declaration and
8467 the entire loop, including the other two expressions; it is reached in the order of execution
8468 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
8469 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note158"><b>158)</b></a></sup>
8470 <p><a name="6.8.5.3p2" href="#6.8.5.3p2"><small>2</small></a>
8471 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
8475 <p><small><a name="note158" href="#note158">158)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
8476 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
8477 such that execution of the loop continues until the expression compares equal to 0; and expression-3
8478 specifies an operation (such as incrementing) that is performed after each iteration.
8481 <p><small><a href="#Contents">Contents</a></small>
8482 <h4><a name="6.8.6" href="#6.8.6">6.8.6 Jump statements</a></h4>
8484 <p><a name="6.8.6p1" href="#6.8.6p1"><small>1</small></a>
8490 return expression<sub>opt</sub> ;
8498 <p><a name="6.8.6p2" href="#6.8.6p2"><small>2</small></a>
8499 A jump statement causes an unconditional jump to another place.
8501 <p><small><a href="#Contents">Contents</a></small>
8502 <h5><a name="6.8.6.1" href="#6.8.6.1">6.8.6.1 The goto statement</a></h5>
8503 <p><b>Constraints</b>
8504 <p><a name="6.8.6.1p1" href="#6.8.6.1p1"><small>1</small></a>
8505 The identifier in a goto statement shall name a label located somewhere in the enclosing
8506 function. A goto statement shall not jump from outside the scope of an identifier having
8507 a variably modified type to inside the scope of that identifier.
8509 <p><a name="6.8.6.1p2" href="#6.8.6.1p2"><small>2</small></a>
8510 A goto statement causes an unconditional jump to the statement prefixed by the named
8511 label in the enclosing function.
8512 <p><a name="6.8.6.1p3" href="#6.8.6.1p3"><small>3</small></a>
8513 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
8514 following outline presents one possible approach to a problem based on these three assumptions:
8516 <li> The general initialization code accesses objects only visible to the current function.
8517 <li> The general initialization code is too large to warrant duplication.
8518 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
8519 continue statements, for example.)
8525 // determine next operation
8527 if (need to reinitialize) {
8528 // reinitialize-only code
8531 // general initialization code
8535 // handle other operations
8540 <p><a name="6.8.6.1p4" href="#6.8.6.1p4"><small>4</small></a>
8541 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
8542 modified types. A jump within the scope, however, is permitted.
8544 goto lab3; // invalid: going INTO scope of VLA.
8547 a[j] = <a href="#4.4">4.4</a>;
8549 a[j] = <a href="#3.3">3.3</a>;
8550 goto lab4; // valid: going WITHIN scope of VLA.
8551 a[j] = <a href="#5.5">5.5</a>;
8553 a[j] = <a href="#6.6">6.6</a>;
8555 goto lab4; // invalid: going INTO scope of VLA.
8559 <p><small><a href="#Contents">Contents</a></small>
8560 <h5><a name="6.8.6.2" href="#6.8.6.2">6.8.6.2 The continue statement</a></h5>
8561 <p><b>Constraints</b>
8562 <p><a name="6.8.6.2p1" href="#6.8.6.2p1"><small>1</small></a>
8563 A continue statement shall appear only in or as a loop body.
8565 <p><a name="6.8.6.2p2" href="#6.8.6.2p2"><small>2</small></a>
8566 A continue statement causes a jump to the loop-continuation portion of the smallest
8567 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
8569 while (/* ... */) { do { for (/* ... */) {
8571 /* ... */ /* ... */ /* ... */
8572 continue; continue; continue;
8573 /* ... */ /* ... */ /* ... */
8575 contin: ; contin: ; contin: ;
8576 } } while (/* ... */); }
8577 unless the continue statement shown is in an enclosed iteration statement (in which
8578 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note159"><b>159)</b></a></sup>
8581 <p><small><a name="note159" href="#note159">159)</a> Following the contin: label is a null statement.
8584 <p><small><a href="#Contents">Contents</a></small>
8585 <h5><a name="6.8.6.3" href="#6.8.6.3">6.8.6.3 The break statement</a></h5>
8586 <p><b>Constraints</b>
8587 <p><a name="6.8.6.3p1" href="#6.8.6.3p1"><small>1</small></a>
8588 A break statement shall appear only in or as a switch body or loop body.
8590 <p><a name="6.8.6.3p2" href="#6.8.6.3p2"><small>2</small></a>
8591 A break statement terminates execution of the smallest enclosing switch or iteration
8598 <p><small><a href="#Contents">Contents</a></small>
8599 <h5><a name="6.8.6.4" href="#6.8.6.4">6.8.6.4 The return statement</a></h5>
8600 <p><b>Constraints</b>
8601 <p><a name="6.8.6.4p1" href="#6.8.6.4p1"><small>1</small></a>
8602 A return statement with an expression shall not appear in a function whose return type
8603 is void. A return statement without an expression shall only appear in a function
8604 whose return type is void.
8606 <p><a name="6.8.6.4p2" href="#6.8.6.4p2"><small>2</small></a>
8607 A return statement terminates execution of the current function and returns control to
8608 its caller. A function may have any number of return statements.
8609 <p><a name="6.8.6.4p3" href="#6.8.6.4p3"><small>3</small></a>
8610 If a return statement with an expression is executed, the value of the expression is
8611 returned to the caller as the value of the function call expression. If the expression has a
8612 type different from the return type of the function in which it appears, the value is
8613 converted as if by assignment to an object having the return type of the function.<sup><a href="#note160"><b>160)</b></a></sup>
8614 <p><a name="6.8.6.4p4" href="#6.8.6.4p4"><small>4</small></a>
8617 struct s { double i; } f(void);
8635 there is no undefined behavior, although there would be if the assignment were done directly (without using
8636 a function call to fetch the value).
8644 <p><small><a name="note160" href="#note160">160)</a> The return statement is not an assignment. The overlap restriction of subclause <a href="#6.5.16.1">6.5.16.1</a> does not
8645 apply to the case of function return. The representation of floating-point values may have wider range
8646 or precision than implied by the type; a cast may be used to remove this extra range and precision.
8649 <p><small><a href="#Contents">Contents</a></small>
8650 <h3><a name="6.9" href="#6.9">6.9 External definitions</a></h3>
8652 <p><a name="6.9p1" href="#6.9p1"><small>1</small></a>
8655 external-declaration
8656 translation-unit external-declaration
8657 external-declaration:
8661 <p><b>Constraints</b>
8662 <p><a name="6.9p2" href="#6.9p2"><small>2</small></a>
8663 The storage-class specifiers auto and register shall not appear in the declaration
8664 specifiers in an external declaration.
8665 <p><a name="6.9p3" href="#6.9p3"><small>3</small></a>
8666 There shall be no more than one external definition for each identifier declared with
8667 internal linkage in a translation unit. Moreover, if an identifier declared with internal
8668 linkage is used in an expression (other than as a part of the operand of a sizeof or
8669 _Alignof operator whose result is an integer constant), there shall be exactly one
8670 external definition for the identifier in the translation unit.
8672 <p><a name="6.9p4" href="#6.9p4"><small>4</small></a>
8673 As discussed in <a href="#5.1.1.1">5.1.1.1</a>, the unit of program text after preprocessing is a translation unit,
8674 which consists of a sequence of external declarations. These are described as ''external''
8675 because they appear outside any function (and hence have file scope). As discussed in
8676 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
8677 by the identifier is a definition.
8678 <p><a name="6.9p5" href="#6.9p5"><small>5</small></a>
8679 An external definition is an external declaration that is also a definition of a function
8680 (other than an inline definition) or an object. If an identifier declared with external
8681 linkage is used in an expression (other than as part of the operand of a sizeof or
8682 _Alignof operator whose result is an integer constant), somewhere in the entire
8683 program there shall be exactly one external definition for the identifier; otherwise, there
8684 shall be no more than one.<sup><a href="#note161"><b>161)</b></a></sup>
8692 <p><small><a name="note161" href="#note161">161)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
8693 external definition for it.
8696 <p><small><a href="#Contents">Contents</a></small>
8697 <h4><a name="6.9.1" href="#6.9.1">6.9.1 Function definitions</a></h4>
8699 <p><a name="6.9.1p1" href="#6.9.1p1"><small>1</small></a>
8701 function-definition:
8702 declaration-specifiers declarator declaration-list<sub>opt</sub> compound-statement
8705 declaration-list declaration
8707 <p><b>Constraints</b>
8708 <p><a name="6.9.1p2" href="#6.9.1p2"><small>2</small></a>
8709 The identifier declared in a function definition (which is the name of the function) shall
8710 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note162"><b>162)</b></a></sup>
8711 <p><a name="6.9.1p3" href="#6.9.1p3"><small>3</small></a>
8712 The return type of a function shall be void or a complete object type other than array
8714 <p><a name="6.9.1p4" href="#6.9.1p4"><small>4</small></a>
8715 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
8717 <p><a name="6.9.1p5" href="#6.9.1p5"><small>5</small></a>
8718 If the declarator includes a parameter type list, the declaration of each parameter shall
8719 include an identifier, except for the special case of a parameter list consisting of a single
8720 parameter of type void, in which case there shall not be an identifier. No declaration list
8722 <p><a name="6.9.1p6" href="#6.9.1p6"><small>6</small></a>
8723 If the declarator includes an identifier list, each declaration in the declaration list shall
8724 have at least one declarator, those declarators shall declare only identifiers from the
8725 identifier list, and every identifier in the identifier list shall be declared. An identifier
8726 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
8727 declaration list shall contain no storage-class specifier other than register and no
8734 <p><a name="6.9.1p7" href="#6.9.1p7"><small>7</small></a>
8735 The declarator in a function definition specifies the name of the function being defined
8736 and the identifiers of its parameters. If the declarator includes a parameter type list, the
8737 list also specifies the types of all the parameters; such a declarator also serves as a
8738 function prototype for later calls to the same function in the same translation unit. If the
8739 declarator includes an identifier list,<sup><a href="#note163"><b>163)</b></a></sup> the types of the parameters shall be declared in a
8740 following declaration list. In either case, the type of each parameter is adjusted as
8741 described in <a href="#6.7.6.3">6.7.6.3</a> for a parameter type list; the resulting type shall be a complete object
8743 <p><a name="6.9.1p8" href="#6.9.1p8"><small>8</small></a>
8744 If a function that accepts a variable number of arguments is defined without a parameter
8745 type list that ends with the ellipsis notation, the behavior is undefined.
8746 <p><a name="6.9.1p9" href="#6.9.1p9"><small>9</small></a>
8747 Each parameter has automatic storage duration; its identifier is an lvalue.<sup><a href="#note164"><b>164)</b></a></sup> The layout
8748 of the storage for parameters is unspecified.
8749 <p><a name="6.9.1p10" href="#6.9.1p10"><small>10</small></a>
8750 On entry to the function, the size expressions of each variably modified parameter are
8751 evaluated and the value of each argument expression is converted to the type of the
8752 corresponding parameter as if by assignment. (Array expressions and function
8753 designators as arguments were converted to pointers before the call.)
8754 <p><a name="6.9.1p11" href="#6.9.1p11"><small>11</small></a>
8755 After all parameters have been assigned, the compound statement that constitutes the
8756 body of the function definition is executed.
8757 <p><a name="6.9.1p12" href="#6.9.1p12"><small>12</small></a>
8758 If the } that terminates a function is reached, and the value of the function call is used by
8759 the caller, the behavior is undefined.
8760 <p><a name="6.9.1p13" href="#6.9.1p13"><small>13</small></a>
8761 EXAMPLE 1 In the following:
8763 extern int max(int a, int b)
8765 return a > b ? a : b;
8768 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
8769 function declarator; and
8771 { return a > b ? a : b; }
8773 is the function body. The following similar definition uses the identifier-list form for the parameter
8781 extern int max(a, b)
8784 return a > b ? a : b;
8787 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
8788 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
8789 to the function, whereas the second form does not.
8791 <p><a name="6.9.1p14" href="#6.9.1p14"><small>14</small></a>
8792 EXAMPLE 2 To pass one function to another, one might say
8798 Then the definition of g might read
8800 void g(int (*funcp)(void))
8803 (*funcp)(); /* or funcp(); ... */
8808 void g(int func(void))
8811 func(); /* or (*func)(); ... */
8817 <p><small><a name="note162" href="#note162">162)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
8820 typedef int F(void); // type F is ''function with no parameters
8822 F f, g; // f and g both have type compatible with F
8823 F f { /* ... */ } // WRONG: syntax/constraint error
8824 F g() { /* ... */ } // WRONG: declares that g returns a function
8825 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
8826 int g() { /* ... */ } // RIGHT: g has type compatible with F
8827 F *e(void) { /* ... */ } // e returns a pointer to a function
8828 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
8829 int (*fp)(void); // fp points to a function that has type F
8830 F *Fp; // Fp points to a function that has type F
8833 <p><small><a name="note163" href="#note163">163)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
8835 <p><small><a name="note164" href="#note164">164)</a> A parameter identifier cannot be redeclared in the function body except in an enclosed block.
8838 <p><small><a href="#Contents">Contents</a></small>
8839 <h4><a name="6.9.2" href="#6.9.2">6.9.2 External object definitions</a></h4>
8841 <p><a name="6.9.2p1" href="#6.9.2p1"><small>1</small></a>
8842 If the declaration of an identifier for an object has file scope and an initializer, the
8843 declaration is an external definition for the identifier.
8844 <p><a name="6.9.2p2" href="#6.9.2p2"><small>2</small></a>
8845 A declaration of an identifier for an object that has file scope without an initializer, and
8846 without a storage-class specifier or with the storage-class specifier static, constitutes a
8847 tentative definition. If a translation unit contains one or more tentative definitions for an
8848 identifier, and the translation unit contains no external definition for that identifier, then
8849 the behavior is exactly as if the translation unit contains a file scope declaration of that
8850 identifier, with the composite type as of the end of the translation unit, with an initializer
8852 <p><a name="6.9.2p3" href="#6.9.2p3"><small>3</small></a>
8853 If the declaration of an identifier for an object is a tentative definition and has internal
8854 linkage, the declared type shall not be an incomplete type.
8856 <p><a name="6.9.2p4" href="#6.9.2p4"><small>4</small></a>
8859 int i1 = 1; // definition, external linkage
8860 static int i2 = 2; // definition, internal linkage
8861 extern int i3 = 3; // definition, external linkage
8862 int i4; // tentative definition, external linkage
8863 static int i5; // tentative definition, internal linkage
8864 int i1; // valid tentative definition, refers to previous
8865 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
8866 int i3; // valid tentative definition, refers to previous
8867 int i4; // valid tentative definition, refers to previous
8868 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
8869 extern int i1; // refers to previous, whose linkage is external
8870 extern int i2; // refers to previous, whose linkage is internal
8871 extern int i3; // refers to previous, whose linkage is external
8872 extern int i4; // refers to previous, whose linkage is external
8873 extern int i5; // refers to previous, whose linkage is internal
8876 <p><a name="6.9.2p5" href="#6.9.2p5"><small>5</small></a>
8877 EXAMPLE 2 If at the end of the translation unit containing
8881 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
8882 zero on program startup.
8885 <p><small><a href="#Contents">Contents</a></small>
8886 <h3><a name="6.10" href="#6.10">6.10 Preprocessing directives</a></h3>
8888 <p><a name="6.10p1" href="#6.10p1"><small>1</small></a>
8902 if-group elif-groups<sub>opt</sub> else-group<sub>opt</sub> endif-line
8904 # if constant-expression new-line group<sub>opt</sub>
8905 # ifdef identifier new-line group<sub>opt</sub>
8906 # ifndef identifier new-line group<sub>opt</sub>
8909 elif-groups elif-group
8911 # elif constant-expression new-line group<sub>opt</sub>
8913 # else new-line group<sub>opt</sub>
8917 # include pp-tokens new-line
8918 # define identifier replacement-list new-line
8919 # define identifier lparen identifier-list<sub>opt</sub> )
8920 replacement-list new-line
8921 # define identifier lparen ... ) replacement-list new-line
8922 # define identifier lparen identifier-list , ... )
8923 replacement-list new-line
8924 # undef identifier new-line
8925 # line pp-tokens new-line
8926 # error pp-tokens<sub>opt</sub> new-line
8927 # pragma pp-tokens<sub>opt</sub> new-line
8930 pp-tokens<sub>opt</sub> new-line
8934 a ( character not immediately preceded by white-space
8936 pp-tokens<sub>opt</sub>
8939 pp-tokens preprocessing-token
8941 the new-line character
8943 <p><b>Description</b>
8944 <p><a name="6.10p2" href="#6.10p2"><small>2</small></a>
8945 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
8946 following constraints: The first token in the sequence is a # preprocessing token that (at
8947 the start of translation phase 4) is either the first character in the source file (optionally
8948 after white space containing no new-line characters) or that follows white space
8949 containing at least one new-line character. The last token in the sequence is the first new-
8950 line character that follows the first token in the sequence.<sup><a href="#note165"><b>165)</b></a></sup> A new-line character ends
8951 the preprocessing directive even if it occurs within what would otherwise be an
8954 invocation of a function-like macro.
8955 <p><a name="6.10p3" href="#6.10p3"><small>3</small></a>
8956 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
8957 with any of the directive names appearing in the syntax.
8958 <p><a name="6.10p4" href="#6.10p4"><small>4</small></a>
8959 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
8960 sequence of preprocessing tokens to occur between the directive name and the following
8962 <p><b>Constraints</b>
8963 <p><a name="6.10p5" href="#6.10p5"><small>5</small></a>
8964 The only white-space characters that shall appear between preprocessing tokens within a
8965 preprocessing directive (from just after the introducing # preprocessing token through
8966 just before the terminating new-line character) are space and horizontal-tab (including
8967 spaces that have replaced comments or possibly other white-space characters in
8968 translation phase 3).
8970 <p><a name="6.10p6" href="#6.10p6"><small>6</small></a>
8971 The implementation can process and skip sections of source files conditionally, include
8972 other source files, and replace macros. These capabilities are called preprocessing,
8973 because conceptually they occur before translation of the resulting translation unit.
8974 <p><a name="6.10p7" href="#6.10p7"><small>7</small></a>
8975 The preprocessing tokens within a preprocessing directive are not subject to macro
8976 expansion unless otherwise stated.
8977 <p><a name="6.10p8" href="#6.10p8"><small>8</small></a>
8981 EMPTY # include <file.h>
8983 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
8984 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
8989 <p><small><a name="note165" href="#note165">165)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
8990 significance, as all white space is equivalent except in certain situations during preprocessing (see the
8991 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
8994 <p><small><a href="#Contents">Contents</a></small>
8995 <h4><a name="6.10.1" href="#6.10.1">6.10.1 Conditional inclusion</a></h4>
8996 <p><b>Constraints</b>
8997 <p><a name="6.10.1p1" href="#6.10.1p1"><small>1</small></a>
8998 The expression that controls conditional inclusion shall be an integer constant expression
8999 except that: identifiers (including those lexically identical to keywords) are interpreted as
9000 described below;<sup><a href="#note166"><b>166)</b></a></sup> and it may contain unary operator expressions of the form
9006 defined ( identifier )
9008 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
9012 predefined or if it has been the subject of a #define preprocessing directive without an
9013 intervening #undef directive with the same subject identifier), 0 if it is not.
9014 <p><a name="6.10.1p2" href="#6.10.1p2"><small>2</small></a>
9015 Each preprocessing token that remains (in the list of preprocessing tokens that will
9016 become the controlling expression) after all macro replacements have occurred shall be in
9017 the lexical form of a token (<a href="#6.4">6.4</a>).
9019 <p><a name="6.10.1p3" href="#6.10.1p3"><small>3</small></a>
9020 Preprocessing directives of the forms
9022 # if constant-expression new-line group<sub>opt</sub>
9023 # elif constant-expression new-line group<sub>opt</sub>
9025 check whether the controlling constant expression evaluates to nonzero.
9026 <p><a name="6.10.1p4" href="#6.10.1p4"><small>4</small></a>
9027 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
9028 the controlling constant expression are replaced (except for those macro names modified
9029 by the defined unary operator), just as in normal text. If the token defined is
9030 generated as a result of this replacement process or use of the defined unary operator
9031 does not match one of the two specified forms prior to macro replacement, the behavior is
9032 undefined. After all replacements due to macro expansion and the defined unary
9033 operator have been performed, all remaining identifiers (including those lexically
9034 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
9035 token is converted into a token. The resulting tokens compose the controlling constant
9036 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
9037 token conversion and evaluation, all signed integer types and all unsigned integer types
9038 act as if they have the same representation as, respectively, the types intmax_t and
9039 uintmax_t defined in the header <a href="#7.20"><stdint.h></a>.<sup><a href="#note167"><b>167)</b></a></sup> This includes interpreting
9040 character constants, which may involve converting escape sequences into execution
9041 character set members. Whether the numeric value for these character constants matches
9042 the value obtained when an identical character constant occurs in an expression (other
9043 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note168"><b>168)</b></a></sup> Also, whether a
9044 single-character character constant may have a negative value is implementation-defined.
9050 <p><a name="6.10.1p5" href="#6.10.1p5"><small>5</small></a>
9051 Preprocessing directives of the forms
9053 # ifdef identifier new-line group<sub>opt</sub>
9054 # ifndef identifier new-line group<sub>opt</sub>
9056 check whether the identifier is or is not currently defined as a macro name. Their
9057 conditions are equivalent to #if defined identifier and #if !defined identifier
9059 <p><a name="6.10.1p6" href="#6.10.1p6"><small>6</small></a>
9060 Each directive's condition is checked in order. If it evaluates to false (zero), the group
9061 that it controls is skipped: directives are processed only through the name that determines
9062 the directive in order to keep track of the level of nested conditionals; the rest of the
9063 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
9064 group. Only the first group whose control condition evaluates to true (nonzero) is
9065 processed. If none of the conditions evaluates to true, and there is a #else directive, the
9066 group controlled by the #else is processed; lacking a #else directive, all the groups
9067 until the #endif are skipped.<sup><a href="#note169"><b>169)</b></a></sup>
9068 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>), source file inclusion (<a href="#6.10.2">6.10.2</a>), largest
9069 integer types (<a href="#7.20.1.5">7.20.1.5</a>).
9072 <p><small><a name="note166" href="#note166">166)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
9073 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
9075 <p><small><a name="note167" href="#note167">167)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
9076 0x8000 is signed and positive within a #if expression even though it would be unsigned in
9077 translation phase 7.
9079 <p><small><a name="note168" href="#note168">168)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
9080 evaluate to the same value in these two contexts.
9084 if ('z' - 'a' == 25)
9087 <p><small><a name="note169" href="#note169">169)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
9088 before the terminating new-line character. However, comments may appear anywhere in a source file,
9089 including within a preprocessing directive.
9092 <p><small><a href="#Contents">Contents</a></small>
9093 <h4><a name="6.10.2" href="#6.10.2">6.10.2 Source file inclusion</a></h4>
9094 <p><b>Constraints</b>
9095 <p><a name="6.10.2p1" href="#6.10.2p1"><small>1</small></a>
9096 A #include directive shall identify a header or source file that can be processed by the
9099 <p><a name="6.10.2p2" href="#6.10.2p2"><small>2</small></a>
9100 A preprocessing directive of the form
9102 # include <h-char-sequence> new-line
9104 searches a sequence of implementation-defined places for a header identified uniquely by
9105 the specified sequence between the < and > delimiters, and causes the replacement of that
9106 directive by the entire contents of the header. How the places are specified or the header
9107 identified is implementation-defined.
9108 <p><a name="6.10.2p3" href="#6.10.2p3"><small>3</small></a>
9109 A preprocessing directive of the form
9111 # include "q-char-sequence" new-line
9113 causes the replacement of that directive by the entire contents of the source file identified
9114 by the specified sequence between the " delimiters. The named source file is searched
9118 for in an implementation-defined manner. If this search is not supported, or if the search
9119 fails, the directive is reprocessed as if it read
9121 # include <h-char-sequence> new-line
9123 with the identical contained sequence (including > characters, if any) from the original
9125 <p><a name="6.10.2p4" href="#6.10.2p4"><small>4</small></a>
9126 A preprocessing directive of the form
9128 # include pp-tokens new-line
9130 (that does not match one of the two previous forms) is permitted. The preprocessing
9131 tokens after include in the directive are processed just as in normal text. (Each
9132 identifier currently defined as a macro name is replaced by its replacement list of
9133 preprocessing tokens.) The directive resulting after all replacements shall match one of
9134 the two previous forms.<sup><a href="#note170"><b>170)</b></a></sup> The method by which a sequence of preprocessing tokens
9135 between a < and a > preprocessing token pair or a pair of " characters is combined into a
9136 single header name preprocessing token is implementation-defined.
9137 <p><a name="6.10.2p5" href="#6.10.2p5"><small>5</small></a>
9138 The implementation shall provide unique mappings for sequences consisting of one or
9139 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
9140 first character shall not be a digit. The implementation may ignore distinctions of
9141 alphabetical case and restrict the mapping to eight significant characters before the
9143 <p><a name="6.10.2p6" href="#6.10.2p6"><small>6</small></a>
9144 A #include preprocessing directive may appear in a source file that has been read
9145 because of a #include directive in another file, up to an implementation-defined
9146 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
9147 <p><a name="6.10.2p7" href="#6.10.2p7"><small>7</small></a>
9148 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
9150 #include <a href="#7.21"><stdio.h></a>
9158 <p><a name="6.10.2p8" href="#6.10.2p8"><small>8</small></a>
9159 EXAMPLE 2 This illustrates macro-replaced #include directives:
9162 #define INCFILE "vers1.h"
9164 #define INCFILE "vers2.h" // and so on
9166 #define INCFILE "versN.h"
9171 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>).
9174 <p><small><a name="note170" href="#note170">170)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
9175 phases in <a href="#5.1.1.2">5.1.1.2</a>); thus, an expansion that results in two string literals is an invalid directive.
9178 <p><small><a href="#Contents">Contents</a></small>
9179 <h4><a name="6.10.3" href="#6.10.3">6.10.3 Macro replacement</a></h4>
9180 <p><b>Constraints</b>
9181 <p><a name="6.10.3p1" href="#6.10.3p1"><small>1</small></a>
9182 Two replacement lists are identical if and only if the preprocessing tokens in both have
9183 the same number, ordering, spelling, and white-space separation, where all white-space
9184 separations are considered identical.
9185 <p><a name="6.10.3p2" href="#6.10.3p2"><small>2</small></a>
9186 An identifier currently defined as an object-like macro shall not be redefined by another
9187 #define preprocessing directive unless the second definition is an object-like macro
9188 definition and the two replacement lists are identical. Likewise, an identifier currently
9189 defined as a function-like macro shall not be redefined by another #define
9190 preprocessing directive unless the second definition is a function-like macro definition
9191 that has the same number and spelling of parameters, and the two replacement lists are
9193 <p><a name="6.10.3p3" href="#6.10.3p3"><small>3</small></a>
9194 There shall be white-space between the identifier and the replacement list in the definition
9195 of an object-like macro.
9196 <p><a name="6.10.3p4" href="#6.10.3p4"><small>4</small></a>
9197 If the identifier-list in the macro definition does not end with an ellipsis, the number of
9198 arguments (including those arguments consisting of no preprocessing tokens) in an
9199 invocation of a function-like macro shall equal the number of parameters in the macro
9200 definition. Otherwise, there shall be more arguments in the invocation than there are
9201 parameters in the macro definition (excluding the ...). There shall exist a )
9202 preprocessing token that terminates the invocation.
9203 <p><a name="6.10.3p5" href="#6.10.3p5"><small>5</small></a>
9204 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
9205 macro that uses the ellipsis notation in the parameters.
9206 <p><a name="6.10.3p6" href="#6.10.3p6"><small>6</small></a>
9207 A parameter identifier in a function-like macro shall be uniquely declared within its
9210 <p><a name="6.10.3p7" href="#6.10.3p7"><small>7</small></a>
9211 The identifier immediately following the define is called the macro name. There is one
9212 name space for macro names. Any white-space characters preceding or following the
9213 replacement list of preprocessing tokens are not considered part of the replacement list
9215 for either form of macro.
9216 <p><a name="6.10.3p8" href="#6.10.3p8"><small>8</small></a>
9217 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
9218 a preprocessing directive could begin, the identifier is not subject to macro replacement.
9219 <p><a name="6.10.3p9" href="#6.10.3p9"><small>9</small></a>
9220 A preprocessing directive of the form
9222 # define identifier replacement-list new-line
9224 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note171"><b>171)</b></a></sup>
9225 to be replaced by the replacement list of preprocessing tokens that constitute the
9226 remainder of the directive. The replacement list is then rescanned for more macro names
9228 <p><a name="6.10.3p10" href="#6.10.3p10"><small>10</small></a>
9229 A preprocessing directive of the form
9231 # define identifier lparen identifier-list<sub>opt</sub> ) replacement-list new-line
9232 # define identifier lparen ... ) replacement-list new-line
9233 # define identifier lparen identifier-list , ... ) replacement-list new-line
9235 defines a function-like macro with parameters, whose use is similar syntactically to a
9236 function call. The parameters are specified by the optional list of identifiers, whose scope
9237 extends from their declaration in the identifier list until the new-line character that
9238 terminates the #define preprocessing directive. Each subsequent instance of the
9239 function-like macro name followed by a ( as the next preprocessing token introduces the
9240 sequence of preprocessing tokens that is replaced by the replacement list in the definition
9241 (an invocation of the macro). The replaced sequence of preprocessing tokens is
9242 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
9243 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
9244 tokens making up an invocation of a function-like macro, new-line is considered a normal
9245 white-space character.
9246 <p><a name="6.10.3p11" href="#6.10.3p11"><small>11</small></a>
9247 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
9248 forms the list of arguments for the function-like macro. The individual arguments within
9249 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
9250 between matching inner parentheses do not separate arguments. If there are sequences of
9251 preprocessing tokens within the list of arguments that would otherwise act as
9252 preprocessing directives,<sup><a href="#note172"><b>172)</b></a></sup> the behavior is undefined.
9253 <p><a name="6.10.3p12" href="#6.10.3p12"><small>12</small></a>
9254 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
9255 including any separating comma preprocessing tokens, are merged to form a single item:
9259 the variable arguments. The number of arguments so combined is such that, following
9260 merger, the number of arguments is one more than the number of parameters in the macro
9261 definition (excluding the ...).
9264 <p><small><a name="note171" href="#note171">171)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
9265 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
9266 are never scanned for macro names or parameters.
9268 <p><small><a name="note172" href="#note172">172)</a> Despite the name, a non-directive is a preprocessing directive.
9271 <p><small><a href="#Contents">Contents</a></small>
9272 <h5><a name="6.10.3.1" href="#6.10.3.1">6.10.3.1 Argument substitution</a></h5>
9273 <p><a name="6.10.3.1p1" href="#6.10.3.1p1"><small>1</small></a>
9274 After the arguments for the invocation of a function-like macro have been identified,
9275 argument substitution takes place. A parameter in the replacement list, unless preceded
9276 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
9277 replaced by the corresponding argument after all macros contained therein have been
9278 expanded. Before being substituted, each argument's preprocessing tokens are
9279 completely macro replaced as if they formed the rest of the preprocessing file; no other
9280 preprocessing tokens are available.
9281 <p><a name="6.10.3.1p2" href="#6.10.3.1p2"><small>2</small></a>
9282 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
9283 were a parameter, and the variable arguments shall form the preprocessing tokens used to
9286 <p><small><a href="#Contents">Contents</a></small>
9287 <h5><a name="6.10.3.2" href="#6.10.3.2">6.10.3.2 The # operator</a></h5>
9288 <p><b>Constraints</b>
9289 <p><a name="6.10.3.2p1" href="#6.10.3.2p1"><small>1</small></a>
9290 Each # preprocessing token in the replacement list for a function-like macro shall be
9291 followed by a parameter as the next preprocessing token in the replacement list.
9293 <p><a name="6.10.3.2p2" href="#6.10.3.2p2"><small>2</small></a>
9294 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
9295 token, both are replaced by a single character string literal preprocessing token that
9296 contains the spelling of the preprocessing token sequence for the corresponding
9297 argument. Each occurrence of white space between the argument's preprocessing tokens
9298 becomes a single space character in the character string literal. White space before the
9299 first preprocessing token and after the last preprocessing token composing the argument
9300 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
9301 is retained in the character string literal, except for special handling for producing the
9302 spelling of string literals and character constants: a \ character is inserted before each "
9303 and \ character of a character constant or string literal (including the delimiting "
9304 characters), except that it is implementation-defined whether a \ character is inserted
9305 before the \ character beginning a universal character name. If the replacement that
9306 results is not a valid character string literal, the behavior is undefined. The character
9307 string literal corresponding to an empty argument is "". The order of evaluation of # and
9308 ## operators is unspecified.
9311 <p><small><a href="#Contents">Contents</a></small>
9312 <h5><a name="6.10.3.3" href="#6.10.3.3">6.10.3.3 The ## operator</a></h5>
9313 <p><b>Constraints</b>
9314 <p><a name="6.10.3.3p1" href="#6.10.3.3p1"><small>1</small></a>
9315 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
9316 list for either form of macro definition.
9318 <p><a name="6.10.3.3p2" href="#6.10.3.3p2"><small>2</small></a>
9319 If, in the replacement list of a function-like macro, a parameter is immediately preceded
9320 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
9321 argument's preprocessing token sequence; however, if an argument consists of no
9322 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
9323 instead.<sup><a href="#note173"><b>173)</b></a></sup>
9324 <p><a name="6.10.3.3p3" href="#6.10.3.3p3"><small>3</small></a>
9325 For both object-like and function-like macro invocations, before the replacement list is
9326 reexamined for more macro names to replace, each instance of a ## preprocessing token
9327 in the replacement list (not from an argument) is deleted and the preceding preprocessing
9328 token is concatenated with the following preprocessing token. Placemarker
9329 preprocessing tokens are handled specially: concatenation of two placemarkers results in
9330 a single placemarker preprocessing token, and concatenation of a placemarker with a
9331 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
9332 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
9333 token is available for further macro replacement. The order of evaluation of ## operators
9335 <p><a name="6.10.3.3p4" href="#6.10.3.3p4"><small>4</small></a>
9336 EXAMPLE In the following fragment:
9338 #define hash_hash # ## #
9339 #define mkstr(a) # a
9340 #define in_between(a) mkstr(a)
9341 #define join(c, d) in_between(c hash_hash d)
9342 char p[] = join(x, y); // equivalent to
9343 // char p[] = "x ## y";
9345 The expansion produces, at various stages:
9348 in_between(x hash_hash y)
9353 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
9354 this new token is not the ## operator.
9360 <p><small><a name="note173" href="#note173">173)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
9361 exist only within translation phase 4.
9364 <p><small><a href="#Contents">Contents</a></small>
9365 <h5><a name="6.10.3.4" href="#6.10.3.4">6.10.3.4 Rescanning and further replacement</a></h5>
9366 <p><a name="6.10.3.4p1" href="#6.10.3.4p1"><small>1</small></a>
9367 After all parameters in the replacement list have been substituted and # and ##
9368 processing has taken place, all placemarker preprocessing tokens are removed. The
9369 resulting preprocessing token sequence is then rescanned, along with all subsequent
9370 preprocessing tokens of the source file, for more macro names to replace.
9371 <p><a name="6.10.3.4p2" href="#6.10.3.4p2"><small>2</small></a>
9372 If the name of the macro being replaced is found during this scan of the replacement list
9373 (not including the rest of the source file's preprocessing tokens), it is not replaced.
9374 Furthermore, if any nested replacements encounter the name of the macro being replaced,
9375 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
9376 available for further replacement even if they are later (re)examined in contexts in which
9377 that macro name preprocessing token would otherwise have been replaced.
9378 <p><a name="6.10.3.4p3" href="#6.10.3.4p3"><small>3</small></a>
9379 The resulting completely macro-replaced preprocessing token sequence is not processed
9380 as a preprocessing directive even if it resembles one, but all pragma unary operator
9381 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
9382 <p><a name="6.10.3.4p4" href="#6.10.3.4p4"><small>4</small></a>
9383 EXAMPLE There are cases where it is not clear whether a replacement is nested or not. For example,
9384 given the following macro definitions:
9393 may expand to either
9401 Strictly conforming programs are not permitted to depend on such unspecified behavior.
9404 <p><small><a href="#Contents">Contents</a></small>
9405 <h5><a name="6.10.3.5" href="#6.10.3.5">6.10.3.5 Scope of macro definitions</a></h5>
9406 <p><a name="6.10.3.5p1" href="#6.10.3.5p1"><small>1</small></a>
9407 A macro definition lasts (independent of block structure) until a corresponding #undef
9408 directive is encountered or (if none is encountered) until the end of the preprocessing
9409 translation unit. Macro definitions have no significance after translation phase 4.
9410 <p><a name="6.10.3.5p2" href="#6.10.3.5p2"><small>2</small></a>
9411 A preprocessing directive of the form
9413 # undef identifier new-line
9415 causes the specified identifier no longer to be defined as a macro name. It is ignored if
9416 the specified identifier is not currently defined as a macro name.
9417 <p><a name="6.10.3.5p3" href="#6.10.3.5p3"><small>3</small></a>
9418 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
9425 <p><a name="6.10.3.5p4" href="#6.10.3.5p4"><small>4</small></a>
9426 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
9427 It has the advantages of working for any compatible types of the arguments and of generating in-line code
9428 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
9429 arguments a second time (including side effects) and generating more code than a function if invoked
9430 several times. It also cannot have its address taken, as it has none.
9432 #define max(a, b) ((a) > (b) ? (a) : (b))
9434 The parentheses ensure that the arguments and the resulting expression are bound properly.
9436 <p><a name="6.10.3.5p5" href="#6.10.3.5p5"><small>5</small></a>
9437 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
9440 #define f(a) f(x * (a))
9451 #define r(x,y) x ## y
9453 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
9454 g(x+(3,4)-w) | h 5) & m
9456 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
9457 char c[2][6] = { str(hello), str() };
9461 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
9462 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
9463 int i[] = { 1, 23, 4, 5, };
9464 char c[2][6] = { "hello", "" };
9467 <p><a name="6.10.3.5p6" href="#6.10.3.5p6"><small>6</small></a>
9468 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
9473 #define xstr(s) str(s)
9474 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
9476 #define INCFILE(n) vers ## n
9477 #define glue(a, b) a ## b
9478 #define xglue(a, b) glue(a, b)
9479 #define HIGHLOW "hello"
9480 #define LOW LOW ", world"
9482 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
9483 == 0) str(: @\n), s);
9484 #include xstr(INCFILE(2).h)
9490 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
9492 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
9494 #include "vers2.h" (after macro replacement, before file access)
9498 or, after concatenation of the character string literals,
9500 printf("x1= %d, x2= %s", x1, x2);
9502 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
9504 #include "vers2.h" (after macro replacement, before file access)
9508 Space around the # and ## tokens in the macro definition is optional.
9510 <p><a name="6.10.3.5p7" href="#6.10.3.5p7"><small>7</small></a>
9511 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
9513 #define t(x,y,z) x ## y ## z
9514 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
9515 t(10,,), t(,11,), t(,,12), t(,,) };
9519 int j[] = { 123, 45, 67, 89,
9523 <p><a name="6.10.3.5p8" href="#6.10.3.5p8"><small>8</small></a>
9524 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
9526 #define OBJ_LIKE (1-1)
9527 #define OBJ_LIKE /* white space */ (1-1) /* other */
9528 #define FUNC_LIKE(a) ( a )
9529 #define FUNC_LIKE( a )( /* note the white space */ \
9530 a /* other stuff on this line
9533 But the following redefinitions are invalid:
9535 #define OBJ_LIKE (0) // different token sequence
9536 #define OBJ_LIKE (1 - 1) // different white space
9537 #define FUNC_LIKE(b) ( a ) // different parameter usage
9538 #define FUNC_LIKE(b) ( b ) // different parameter spelling
9541 <p><a name="6.10.3.5p9" href="#6.10.3.5p9"><small>9</small></a>
9542 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
9545 #define debug(...) fprintf(stderr, __VA_ARGS__)
9546 #define showlist(...) puts(#__VA_ARGS__)
9547 #define report(test, ...) ((test)?puts(#test):\
9548 printf(__VA_ARGS__))
9550 debug("X = %d\n", x);
9551 showlist(The first, second, and third items.);
9552 report(x>y, "x is %d but y is %d", x, y);
9556 fprintf(stderr, "Flag" );
9557 fprintf(stderr, "X = %d\n", x );
9558 puts( "The first, second, and third items." );
9559 ((x>y)?puts("x>y"):
9560 printf("x is %d but y is %d", x, y));
9564 <p><small><a href="#Contents">Contents</a></small>
9565 <h4><a name="6.10.4" href="#6.10.4">6.10.4 Line control</a></h4>
9566 <p><b>Constraints</b>
9567 <p><a name="6.10.4p1" href="#6.10.4p1"><small>1</small></a>
9568 The string literal of a #line directive, if present, shall be a character string literal.
9570 <p><a name="6.10.4p2" href="#6.10.4p2"><small>2</small></a>
9571 The line number of the current source line is one greater than the number of new-line
9572 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
9573 file to the current token.
9574 <p><a name="6.10.4p3" href="#6.10.4p3"><small>3</small></a>
9575 A preprocessing directive of the form
9577 # line digit-sequence new-line
9579 causes the implementation to behave as if the following sequence of source lines begins
9580 with a source line that has a line number as specified by the digit sequence (interpreted as
9581 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
9583 <p><a name="6.10.4p4" href="#6.10.4p4"><small>4</small></a>
9584 A preprocessing directive of the form
9586 # line digit-sequence "s-char-sequence<sub>opt</sub>" new-line
9588 sets the presumed line number similarly and changes the presumed name of the source
9589 file to be the contents of the character string literal.
9590 <p><a name="6.10.4p5" href="#6.10.4p5"><small>5</small></a>
9591 A preprocessing directive of the form
9593 # line pp-tokens new-line
9595 (that does not match one of the two previous forms) is permitted. The preprocessing
9596 tokens after line on the directive are processed just as in normal text (each identifier
9597 currently defined as a macro name is replaced by its replacement list of preprocessing
9598 tokens). The directive resulting after all replacements shall match one of the two
9599 previous forms and is then processed as appropriate.
9602 <p><small><a href="#Contents">Contents</a></small>
9603 <h4><a name="6.10.5" href="#6.10.5">6.10.5 Error directive</a></h4>
9605 <p><a name="6.10.5p1" href="#6.10.5p1"><small>1</small></a>
9606 A preprocessing directive of the form
9608 # error pp-tokens<sub>opt</sub> new-line
9610 causes the implementation to produce a diagnostic message that includes the specified
9611 sequence of preprocessing tokens.
9613 <p><small><a href="#Contents">Contents</a></small>
9614 <h4><a name="6.10.6" href="#6.10.6">6.10.6 Pragma directive</a></h4>
9616 <p><a name="6.10.6p1" href="#6.10.6p1"><small>1</small></a>
9617 A preprocessing directive of the form
9619 # pragma pp-tokens<sub>opt</sub> new-line
9621 where the preprocessing token STDC does not immediately follow pragma in the
9622 directive (prior to any macro replacement)<sup><a href="#note174"><b>174)</b></a></sup> causes the implementation to behave in an
9623 implementation-defined manner. The behavior might cause translation to fail or cause the
9624 translator or the resulting program to behave in a non-conforming manner. Any such
9625 pragma that is not recognized by the implementation is ignored.
9626 <p><a name="6.10.6p2" href="#6.10.6p2"><small>2</small></a>
9627 If the preprocessing token STDC does immediately follow pragma in the directive (prior
9628 to any macro replacement), then no macro replacement is performed on the directive, and
9629 the directive shall have one of the following forms<sup><a href="#note175"><b>175)</b></a></sup> whose meanings are described
9632 #pragma STDC FP_CONTRACT on-off-switch
9633 #pragma STDC FENV_ACCESS on-off-switch
9634 #pragma STDC CX_LIMITED_RANGE on-off-switch
9635 on-off-switch: one of
9638 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
9639 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
9647 <p><small><a name="note174" href="#note174">174)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
9648 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
9649 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
9650 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
9651 but is not required to.
9653 <p><small><a name="note175" href="#note175">175)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
9656 <p><small><a href="#Contents">Contents</a></small>
9657 <h4><a name="6.10.7" href="#6.10.7">6.10.7 Null directive</a></h4>
9659 <p><a name="6.10.7p1" href="#6.10.7p1"><small>1</small></a>
9660 A preprocessing directive of the form
9666 <p><small><a href="#Contents">Contents</a></small>
9667 <h4><a name="6.10.8" href="#6.10.8">6.10.8 Predefined macro names</a></h4>
9668 <p><a name="6.10.8p1" href="#6.10.8p1"><small>1</small></a>
9669 The values of the predefined macros listed in the following subclauses<sup><a href="#note176"><b>176)</b></a></sup> (except for
9670 __FILE__ and __LINE__) remain constant throughout the translation unit.
9671 <p><a name="6.10.8p2" href="#6.10.8p2"><small>2</small></a>
9672 None of these macro names, nor the identifier defined, shall be the subject of a
9673 #define or a #undef preprocessing directive. Any other predefined macro names
9674 shall begin with a leading underscore followed by an uppercase letter or a second
9676 <p><a name="6.10.8p3" href="#6.10.8p3"><small>3</small></a>
9677 The implementation shall not predefine the macro __cplusplus, nor shall it define it
9678 in any standard header.
9679 <p><b> Forward references</b>: standard headers (<a href="#7.1.2">7.1.2</a>).
9682 <p><small><a name="note176" href="#note176">176)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
9685 <p><small><a href="#Contents">Contents</a></small>
9686 <h5><a name="6.10.8.1" href="#6.10.8.1">6.10.8.1 Mandatory macros</a></h5>
9687 <p><a name="6.10.8.1p1" href="#6.10.8.1p1"><small>1</small></a>
9688 The following macro names shall be defined by the implementation:
9689 __DATE__ The date of translation of the preprocessing translation unit: a character
9691 string literal of the form "Mmm dd yyyy", where the names of the
9692 months are the same as those generated by the asctime function, and the
9693 first character of dd is a space character if the value is less than 10. If the
9694 date of translation is not available, an implementation-defined valid date
9697 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note177"><b>177)</b></a></sup>
9698 __LINE__ The presumed line number (within the current source file) of the current
9700 source line (an integer constant).<sup><a href="#note177"><b>177)</b></a></sup>
9702 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
9703 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
9705 implementation or the integer constant 0 if it is not.
9712 __STDC_VERSION__ The integer constant 201ymmL.<sup><a href="#note178"><b>178)</b></a></sup>
9713 __TIME__ The time of translation of the preprocessing translation unit: a character
9715 string literal of the form "hh:mm:ss" as in the time generated by the
9716 asctime function. If the time of translation is not available, an
9717 implementation-defined valid time shall be supplied.
9719 <p><b> Forward references</b>: the asctime function (<a href="#7.27.3.1">7.27.3.1</a>).
9722 <p><small><a name="note177" href="#note177">177)</a> The presumed source file name and line number can be changed by the #line directive.
9724 <p><small><a name="note178" href="#note178">178)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
9725 ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
9726 remain an integer constant of type long int that is increased with each revision of this International
9730 <p><small><a href="#Contents">Contents</a></small>
9731 <h5><a name="6.10.8.2" href="#6.10.8.2">6.10.8.2 Environment macros</a></h5>
9732 <p><a name="6.10.8.2p1" href="#6.10.8.2p1"><small>1</small></a>
9733 The following macro names are conditionally defined by the implementation:
9734 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
9736 199712L). If this symbol is defined, then every character in the Unicode
9737 required set, when stored in an object of type wchar_t, has the same
9738 value as the short identifier of that character. The Unicode required set
9739 consists of all the characters that are defined by ISO/IEC 10646, along with
9740 all amendments and technical corrigenda, as of the specified year and
9741 month. If some other encoding is used, the macro shall not be defined and
9742 the actual encoding used is implementation-defined.
9744 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
9746 the encoding for wchar_t, a member of the basic character set need not
9747 have a code value equal to its value when used as the lone character in an
9748 integer character constant.
9750 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
9752 char16_t are UTF-16 encoded. If some other encoding is used, the
9753 macro shall not be defined and the actual encoding used is implementation-
9756 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
9758 char32_t are UTF-32 encoded. If some other encoding is used, the
9759 macro shall not be defined and the actual encoding used is implementation-
9762 <p><b> Forward references</b>: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.28">7.28</a>).
9769 <p><small><a href="#Contents">Contents</a></small>
9770 <h5><a name="6.10.8.3" href="#6.10.8.3">6.10.8.3 Conditional feature macros</a></h5>
9771 <p><a name="6.10.8.3p1" href="#6.10.8.3p1"><small>1</small></a>
9772 The following macro names are conditionally defined by the implementation:
9773 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
9775 the specifications in <a href="#L">annex L</a> (Analyzability).
9777 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
9779 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).
9781 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
9783 adherence to the specifications in <a href="#G">annex G</a> (IEC 60559 compatible complex
9786 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
9788 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).<sup><a href="#note179"><b>179)</b></a></sup>
9790 __STDC_NO_ATOMICS__ The integer constant 1, intended to indicate that the
9792 implementation does not support atomic types (including the _Atomic
9793 type qualifier) and the <a href="#7.17"><stdatomic.h></a> header.
9795 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
9797 implementation does not support complex types or the <a href="#7.3"><complex.h></a>
9800 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
9802 implementation does not support the <a href="#7.26"><threads.h></a> header.
9804 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
9806 implementation does not support variable length arrays or variably
9809 <p><a name="6.10.8.3p2" href="#6.10.8.3p2"><small>2</small></a>
9810 An implementation that defines __STDC_NO_COMPLEX__ shall not define
9811 __STDC_IEC_559_COMPLEX__.
9819 <p><small><a name="note179" href="#note179">179)</a> The intention is that this will remain an integer constant of type long int that is increased with
9820 each revision of this International Standard.
9823 <p><small><a href="#Contents">Contents</a></small>
9824 <h4><a name="6.10.9" href="#6.10.9">6.10.9 Pragma operator</a></h4>
9826 <p><a name="6.10.9p1" href="#6.10.9p1"><small>1</small></a>
9827 A unary operator expression of the form:
9829 _Pragma ( string-literal )
9831 is processed as follows: The string literal is destringized by deleting any encoding prefix,
9832 deleting the leading and trailing double-quotes, replacing each escape sequence \" by a
9833 double-quote, and replacing each escape sequence \\ by a single backslash. The
9834 resulting sequence of characters is processed through translation phase 3 to produce
9835 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
9836 directive. The original four preprocessing tokens in the unary operator expression are
9838 <p><a name="6.10.9p2" href="#6.10.9p2"><small>2</small></a>
9839 EXAMPLE A directive of the form:
9841 #pragma listing on "..\listing.dir"
9843 can also be expressed as:
9845 _Pragma ( "listing on \"..\\listing.dir\"" )
9847 The latter form is processed in the same way whether it appears literally as shown, or results from macro
9851 #define LISTING(x) PRAGMA(listing on #x)
9852 #define PRAGMA(x) _Pragma(#x)
9853 LISTING ( ..\listing.dir )
9856 <p><small><a href="#Contents">Contents</a></small>
9857 <h3><a name="6.11" href="#6.11">6.11 Future language directions</a></h3>
9859 <p><small><a href="#Contents">Contents</a></small>
9860 <h4><a name="6.11.1" href="#6.11.1">6.11.1 Floating types</a></h4>
9861 <p><a name="6.11.1p1" href="#6.11.1p1"><small>1</small></a>
9862 Future standardization may include additional floating-point types, including those with
9863 greater range, precision, or both than long double.
9865 <p><small><a href="#Contents">Contents</a></small>
9866 <h4><a name="6.11.2" href="#6.11.2">6.11.2 Linkages of identifiers</a></h4>
9867 <p><a name="6.11.2p1" href="#6.11.2p1"><small>1</small></a>
9868 Declaring an identifier with internal linkage at file scope without the static storage-
9869 class specifier is an obsolescent feature.
9871 <p><small><a href="#Contents">Contents</a></small>
9872 <h4><a name="6.11.3" href="#6.11.3">6.11.3 External names</a></h4>
9873 <p><a name="6.11.3p1" href="#6.11.3p1"><small>1</small></a>
9874 Restriction of the significance of an external name to fewer than 255 characters
9875 (considering each universal character name or extended source character as a single
9876 character) is an obsolescent feature that is a concession to existing implementations.
9878 <p><small><a href="#Contents">Contents</a></small>
9879 <h4><a name="6.11.4" href="#6.11.4">6.11.4 Character escape sequences</a></h4>
9880 <p><a name="6.11.4p1" href="#6.11.4p1"><small>1</small></a>
9881 Lowercase letters as escape sequences are reserved for future standardization. Other
9882 characters may be used in extensions.
9884 <p><small><a href="#Contents">Contents</a></small>
9885 <h4><a name="6.11.5" href="#6.11.5">6.11.5 Storage-class specifiers</a></h4>
9886 <p><a name="6.11.5p1" href="#6.11.5p1"><small>1</small></a>
9887 The placement of a storage-class specifier other than at the beginning of the declaration
9888 specifiers in a declaration is an obsolescent feature.
9890 <p><small><a href="#Contents">Contents</a></small>
9891 <h4><a name="6.11.6" href="#6.11.6">6.11.6 Function declarators</a></h4>
9892 <p><a name="6.11.6p1" href="#6.11.6p1"><small>1</small></a>
9893 The use of function declarators with empty parentheses (not prototype-format parameter
9894 type declarators) is an obsolescent feature.
9896 <p><small><a href="#Contents">Contents</a></small>
9897 <h4><a name="6.11.7" href="#6.11.7">6.11.7 Function definitions</a></h4>
9898 <p><a name="6.11.7p1" href="#6.11.7p1"><small>1</small></a>
9899 The use of function definitions with separate parameter identifier and declaration lists
9900 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
9902 <p><small><a href="#Contents">Contents</a></small>
9903 <h4><a name="6.11.8" href="#6.11.8">6.11.8 Pragma directives</a></h4>
9904 <p><a name="6.11.8p1" href="#6.11.8p1"><small>1</small></a>
9905 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
9907 <p><small><a href="#Contents">Contents</a></small>
9908 <h4><a name="6.11.9" href="#6.11.9">6.11.9 Predefined macro names</a></h4>
9909 <p><a name="6.11.9p1" href="#6.11.9p1"><small>1</small></a>
9910 Macro names beginning with __STDC_ are reserved for future standardization.
9913 <p><small><a href="#Contents">Contents</a></small>
9914 <h2><a name="7" href="#7">7. Library</a></h2>
9916 <p><small><a href="#Contents">Contents</a></small>
9917 <h3><a name="7.1" href="#7.1">7.1 Introduction</a></h3>
9919 <p><small><a href="#Contents">Contents</a></small>
9920 <h4><a name="7.1.1" href="#7.1.1">7.1.1 Definitions of terms</a></h4>
9921 <p><a name="7.1.1p1" href="#7.1.1p1"><small>1</small></a>
9922 A string is a contiguous sequence of characters terminated by and including the first null
9923 character. The term multibyte string is sometimes used instead to emphasize special
9924 processing given to multibyte characters contained in the string or to avoid confusion
9925 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
9926 character. The length of a string is the number of bytes preceding the null character and
9927 the value of a string is the sequence of the values of the contained characters, in order.
9928 <p><a name="7.1.1p2" href="#7.1.1p2"><small>2</small></a>
9929 The decimal-point character is the character used by functions that convert floating-point
9930 numbers to or from character sequences to denote the beginning of the fractional part of
9931 such character sequences.<sup><a href="#note180"><b>180)</b></a></sup> It is represented in the text and examples by a period, but
9932 may be changed by the setlocale function.
9933 <p><a name="7.1.1p3" href="#7.1.1p3"><small>3</small></a>
9934 A null wide character is a wide character with code value zero.
9935 <p><a name="7.1.1p4" href="#7.1.1p4"><small>4</small></a>
9936 A wide string is a contiguous sequence of wide characters terminated by and including
9937 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
9938 addressed) wide character. The length of a wide string is the number of wide characters
9939 preceding the null wide character and the value of a wide string is the sequence of code
9940 values of the contained wide characters, in order.
9941 <p><a name="7.1.1p5" href="#7.1.1p5"><small>5</small></a>
9942 A shift sequence is a contiguous sequence of bytes within a multibyte string that
9943 (potentially) causes a change in shift state (see <a href="#5.2.1.2">5.2.1.2</a>). A shift sequence shall not have a
9944 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
9945 character.<sup><a href="#note181"><b>181)</b></a></sup>
9946 <p><b> Forward references</b>: character handling (<a href="#7.4">7.4</a>), the setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
9954 <p><small><a name="note180" href="#note180">180)</a> The functions that make use of the decimal-point character are the numeric conversion functions
9955 (<a href="#7.22.1">7.22.1</a>, <a href="#7.29.4.1">7.29.4.1</a>) and the formatted input/output functions (<a href="#7.21.6">7.21.6</a>, <a href="#7.29.2">7.29.2</a>).
9957 <p><small><a name="note181" href="#note181">181)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
9958 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
9959 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
9960 implementation's choice.
9963 <p><small><a href="#Contents">Contents</a></small>
9964 <h4><a name="7.1.2" href="#7.1.2">7.1.2 Standard headers</a></h4>
9965 <p><a name="7.1.2p1" href="#7.1.2p1"><small>1</small></a>
9966 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note182"><b>182)</b></a></sup>
9967 whose contents are made available by the #include preprocessing directive. The
9968 header declares a set of related functions, plus any necessary types and additional macros
9969 needed to facilitate their use. Declarations of types described in this clause shall not
9970 include type qualifiers, unless explicitly stated otherwise.
9971 <p><a name="7.1.2p2" href="#7.1.2p2"><small>2</small></a>
9972 The standard headers are<sup><a href="#note183"><b>183)</b></a></sup>
9974 <a href="#7.2"><assert.h></a> <a href="#7.12"><math.h></a> <a href="#7.22"><stdlib.h></a>
9975 <a href="#7.3"><complex.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.23"><stdnoreturn.h></a>
9976 <a href="#7.4"><ctype.h></a> <a href="#7.14"><signal.h></a> <a href="#7.24"><string.h></a>
9977 <a href="#7.5"><errno.h></a> <a href="#7.15"><stdalign.h></a> <a href="#7.25"><tgmath.h></a>
9978 <a href="#7.6"><fenv.h></a> <a href="#7.16"><stdarg.h></a> <a href="#7.26"><threads.h></a>
9979 <a href="#7.7"><float.h></a> <a href="#7.17"><stdatomic.h></a> <a href="#7.27"><time.h></a>
9980 <a href="#7.8"><inttypes.h></a> <a href="#7.18"><stdbool.h></a> <a href="#7.28"><uchar.h></a>
9981 <a href="#7.9"><iso646.h></a> <a href="#7.19"><stddef.h></a> <a href="#7.29"><wchar.h></a>
9982 <a href="#7.10"><limits.h></a> <a href="#7.20"><stdint.h></a> <a href="#7.30"><wctype.h></a>
9983 <a href="#7.11"><locale.h></a> <a href="#7.21"><stdio.h></a>
9985 <p><a name="7.1.2p3" href="#7.1.2p3"><small>3</small></a>
9986 If a file with the same name as one of the above < and > delimited sequences, not
9987 provided as part of the implementation, is placed in any of the standard places that are
9988 searched for included source files, the behavior is undefined.
9989 <p><a name="7.1.2p4" href="#7.1.2p4"><small>4</small></a>
9990 Standard headers may be included in any order; each may be included more than once in
9991 a given scope, with no effect different from being included only once, except that the
9992 effect of including <a href="#7.2"><assert.h></a> depends on the definition of NDEBUG (see <a href="#7.2">7.2</a>). If
9993 used, a header shall be included outside of any external declaration or definition, and it
9994 shall first be included before the first reference to any of the functions or objects it
9995 declares, or to any of the types or macros it defines. However, if an identifier is declared
9996 or defined in more than one header, the second and subsequent associated headers may be
9997 included after the initial reference to the identifier. The program shall not have any
9998 macros with names lexically identical to keywords currently defined prior to the inclusion
9999 of the header or when any macro defined in the header is expanded.
10000 <p><a name="7.1.2p5" href="#7.1.2p5"><small>5</small></a>
10001 Any definition of an object-like macro described in this clause shall expand to code that is
10002 fully protected by parentheses where necessary, so that it groups in an arbitrary
10003 expression as if it were a single identifier.
10007 <p><a name="7.1.2p6" href="#7.1.2p6"><small>6</small></a>
10008 Any declaration of a library function shall have external linkage.
10009 <p><a name="7.1.2p7" href="#7.1.2p7"><small>7</small></a>
10010 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
10011 <p><b> Forward references</b>: diagnostics (<a href="#7.2">7.2</a>).
10013 <p><b>Footnotes</b>
10014 <p><small><a name="note182" href="#note182">182)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
10015 necessarily valid source file names.
10017 <p><small><a name="note183" href="#note183">183)</a> The headers <a href="#7.3"><complex.h></a>, <a href="#7.17"><stdatomic.h></a>, and <a href="#7.26"><threads.h></a> are conditional features that
10018 implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.
10021 <p><small><a href="#Contents">Contents</a></small>
10022 <h4><a name="7.1.3" href="#7.1.3">7.1.3 Reserved identifiers</a></h4>
10023 <p><a name="7.1.3p1" href="#7.1.3p1"><small>1</small></a>
10024 Each header declares or defines all identifiers listed in its associated subclause, and
10025 optionally declares or defines identifiers listed in its associated future library directions
10026 subclause and identifiers which are always reserved either for any use or for use as file
10029 <li> All identifiers that begin with an underscore and either an uppercase letter or another
10030 underscore are always reserved for any use.
10031 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
10032 with file scope in both the ordinary and tag name spaces.
10033 <li> Each macro name in any of the following subclauses (including the future library
10034 directions) is reserved for use as specified if any of its associated headers is included;
10035 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
10036 <li> All identifiers with external linkage in any of the following subclauses (including the
10037 future library directions) and errno are always reserved for use as identifiers with
10038 external linkage.<sup><a href="#note184"><b>184)</b></a></sup>
10039 <li> Each identifier with file scope listed in any of the following subclauses (including the
10040 future library directions) is reserved for use as a macro name and as an identifier with
10041 file scope in the same name space if any of its associated headers is included.
10043 <p><a name="7.1.3p2" href="#7.1.3p2"><small>2</small></a>
10044 No other identifiers are reserved. If the program declares or defines an identifier in a
10045 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
10046 identifier as a macro name, the behavior is undefined.
10047 <p><a name="7.1.3p3" href="#7.1.3p3"><small>3</small></a>
10048 If the program removes (with #undef) any macro definition of an identifier in the first
10049 group listed above, the behavior is undefined.
10056 <p><b>Footnotes</b>
10057 <p><small><a name="note184" href="#note184">184)</a> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
10058 va_copy, and va_end.
10061 <p><small><a href="#Contents">Contents</a></small>
10062 <h4><a name="7.1.4" href="#7.1.4">7.1.4 Use of library functions</a></h4>
10063 <p><a name="7.1.4p1" href="#7.1.4p1"><small>1</small></a>
10064 Each of the following statements applies unless explicitly stated otherwise in the detailed
10065 descriptions that follow: If an argument to a function has an invalid value (such as a value
10066 outside the domain of the function, or a pointer outside the address space of the program,
10067 or a null pointer, or a pointer to non-modifiable storage when the corresponding
10068 parameter is not const-qualified) or a type (after promotion) not expected by a function
10069 with variable number of arguments, the behavior is undefined. If a function argument is
10070 described as being an array, the pointer actually passed to the function shall have a value
10071 such that all address computations and accesses to objects (that would be valid if the
10072 pointer did point to the first element of such an array) are in fact valid. Any function
10073 declared in a header may be additionally implemented as a function-like macro defined in
10074 the header, so if a library function is declared explicitly when its header is included, one
10075 of the techniques shown below can be used to ensure the declaration is not affected by
10076 such a macro. Any macro definition of a function can be suppressed locally by enclosing
10077 the name of the function in parentheses, because the name is then not followed by the left
10078 parenthesis that indicates expansion of a macro function name. For the same syntactic
10079 reason, it is permitted to take the address of a library function even if it is also defined as
10080 a macro.<sup><a href="#note185"><b>185)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
10081 actual function is referred to. Any invocation of a library function that is implemented as
10082 a macro shall expand to code that evaluates each of its arguments exactly once, fully
10083 protected by parentheses where necessary, so it is generally safe to use arbitrary
10084 expressions as arguments.<sup><a href="#note186"><b>186)</b></a></sup> Likewise, those function-like macros described in the
10085 following subclauses may be invoked in an expression anywhere a function with a
10086 compatible return type could be called.<sup><a href="#note187"><b>187)</b></a></sup> All object-like macros listed as expanding to
10090 integer constant expressions shall additionally be suitable for use in #if preprocessing
10092 <p><a name="7.1.4p2" href="#7.1.4p2"><small>2</small></a>
10093 Provided that a library function can be declared without reference to any type defined in a
10094 header, it is also permissible to declare the function and use it without including its
10096 <p><a name="7.1.4p3" href="#7.1.4p3"><small>3</small></a>
10097 There is a sequence point immediately before a library function returns.
10098 <p><a name="7.1.4p4" href="#7.1.4p4"><small>4</small></a>
10099 The functions in the standard library are not guaranteed to be reentrant and may modify
10100 objects with static or thread storage duration.<sup><a href="#note188"><b>188)</b></a></sup>
10101 <p><a name="7.1.4p5" href="#7.1.4p5"><small>5</small></a>
10102 Unless explicitly stated otherwise in the detailed descriptions that follow, library
10103 functions shall prevent data races as follows: A library function shall not directly or
10104 indirectly access objects accessible by threads other than the current thread unless the
10105 objects are accessed directly or indirectly via the function's arguments. A library
10106 function shall not directly or indirectly modify objects accessible by threads other than
10107 the current thread unless the objects are accessed directly or indirectly via the function's
10108 non-const arguments.<sup><a href="#note189"><b>189)</b></a></sup> Implementations may share their own internal objects between
10109 threads if the objects are not visible to users and are protected against data races.
10110 <p><a name="7.1.4p6" href="#7.1.4p6"><small>6</small></a>
10111 Unless otherwise specified, library functions shall perform all operations solely within the
10112 current thread if those operations have effects that are visible to users.<sup><a href="#note190"><b>190)</b></a></sup>
10113 <p><a name="7.1.4p7" href="#7.1.4p7"><small>7</small></a>
10114 EXAMPLE The function atoi may be used in any of several ways:
10116 <li> by use of its associated header (possibly generating a macro expansion)
10118 #include <a href="#7.22"><stdlib.h></a>
10123 <li> by use of its associated header (assuredly generating a true function reference)
10130 #include <a href="#7.22"><stdlib.h></a>
10138 #include <a href="#7.22"><stdlib.h></a>
10143 <li> by explicit declaration
10146 extern int atoi(const char *);
10153 <p><b>Footnotes</b>
10154 <p><small><a name="note185" href="#note185">185)</a> This means that an implementation shall provide an actual function for each library function, even if it
10155 also provides a macro for that function.
10157 <p><small><a name="note186" href="#note186">186)</a> Such macros might not contain the sequence points that the corresponding function calls do.
10159 <p><small><a name="note187" href="#note187">187)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
10160 implementations may provide special semantics for such names. For example, the identifier
10161 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
10162 appropriate header could specify
10165 #define abs(x) _BUILTIN_abs(x)
10167 for a compiler whose code generator will accept it.
10168 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
10174 whether the implementation's header provides a macro implementation of abs or a built-in
10175 implementation. The prototype for the function, which precedes and is hidden by any macro
10176 definition, is thereby revealed also.
10178 <p><small><a name="note188" href="#note188">188)</a> Thus, a signal handler cannot, in general, call standard library functions.
10180 <p><small><a name="note189" href="#note189">189)</a> This means, for example, that an implementation is not permitted to use a static object for internal
10181 purposes without synchronization because it could cause a data race even in programs that do not
10182 explicitly share objects between threads. Similarly, an implementation of memcpy is not permitted to
10183 copy bytes beyond the specified length of the destination object and then restore the original values
10184 because it could cause a data race if the program shared those bytes between threads.
10186 <p><small><a name="note190" href="#note190">190)</a> This allows implementations to parallelize operations if there are no visible side effects.
10189 <p><small><a href="#Contents">Contents</a></small>
10190 <h3><a name="7.2" href="#7.2">7.2 Diagnostics <assert.h></a></h3>
10191 <p><a name="7.2p1" href="#7.2p1"><small>1</small></a>
10192 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
10193 refers to another macro,
10197 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
10198 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
10201 #define assert(ignore) ((void)0)
10203 The assert macro is redefined according to the current state of NDEBUG each time that
10204 <a href="#7.2"><assert.h></a> is included.
10205 <p><a name="7.2p2" href="#7.2p2"><small>2</small></a>
10206 The assert macro shall be implemented as a macro, not as an actual function. If the
10207 macro definition is suppressed in order to access an actual function, the behavior is
10209 <p><a name="7.2p3" href="#7.2p3"><small>3</small></a>
10214 expands to _Static_assert.
10216 <p><small><a href="#Contents">Contents</a></small>
10217 <h4><a name="7.2.1" href="#7.2.1">7.2.1 Program diagnostics</a></h4>
10219 <p><small><a href="#Contents">Contents</a></small>
10220 <h5><a name="7.2.1.1" href="#7.2.1.1">7.2.1.1 The assert macro</a></h5>
10222 <p><a name="7.2.1.1p1" href="#7.2.1.1p1"><small>1</small></a>
10224 #include <a href="#7.2"><assert.h></a>
10225 void assert(scalar expression);
10227 <p><b>Description</b>
10228 <p><a name="7.2.1.1p2" href="#7.2.1.1p2"><small>2</small></a>
10229 The assert macro puts diagnostic tests into programs; it expands to a void expression.
10230 When it is executed, if expression (which shall have a scalar type) is false (that is,
10231 compares equal to 0), the assert macro writes information about the particular call that
10232 failed (including the text of the argument, the name of the source file, the source line
10233 number, and the name of the enclosing function -- the latter are respectively the values of
10234 the preprocessing macros __FILE__ and __LINE__ and of the identifier
10235 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note191"><b>191)</b></a></sup> It
10236 then calls the abort function.
10242 <p><a name="7.2.1.1p3" href="#7.2.1.1p3"><small>3</small></a>
10243 The assert macro returns no value.
10244 <p><b> Forward references</b>: the abort function (<a href="#7.22.4.1">7.22.4.1</a>).
10247 <p><b>Footnotes</b>
10248 <p><small><a name="note191" href="#note191">191)</a> The message written might be of the form:
10249 Assertion failed: expression, function abc, file xyz, line nnn.
10252 <p><small><a href="#Contents">Contents</a></small>
10253 <h3><a name="7.3" href="#7.3">7.3 Complex arithmetic <complex.h></a></h3>
10255 <p><small><a href="#Contents">Contents</a></small>
10256 <h4><a name="7.3.1" href="#7.3.1">7.3.1 Introduction</a></h4>
10257 <p><a name="7.3.1p1" href="#7.3.1p1"><small>1</small></a>
10258 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
10259 arithmetic.<sup><a href="#note192"><b>192)</b></a></sup>
10260 <p><a name="7.3.1p2" href="#7.3.1p2"><small>2</small></a>
10261 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
10262 this header nor support any of its facilities.
10263 <p><a name="7.3.1p3" href="#7.3.1p3"><small>3</small></a>
10264 Each synopsis specifies a family of functions consisting of a principal function with one
10265 or more double complex parameters and a double complex or double return
10266 value; and other functions with the same name but with f and l suffixes which are
10267 corresponding functions with float and long double parameters and return values.
10268 <p><a name="7.3.1p4" href="#7.3.1p4"><small>4</small></a>
10273 expands to _Complex; the macro
10277 expands to a constant expression of type const float _Complex, with the value of
10278 the imaginary unit.<sup><a href="#note193"><b>193)</b></a></sup>
10279 <p><a name="7.3.1p5" href="#7.3.1p5"><small>5</small></a>
10288 are defined if and only if the implementation supports imaginary types;<sup><a href="#note194"><b>194)</b></a></sup> if defined,
10289 they expand to _Imaginary and a constant expression of type const float
10290 _Imaginary with the value of the imaginary unit.
10291 <p><a name="7.3.1p6" href="#7.3.1p6"><small>6</small></a>
10296 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
10297 defined, I shall expand to _Complex_I.
10298 <p><a name="7.3.1p7" href="#7.3.1p7"><small>7</small></a>
10299 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
10300 redefine the macros complex, imaginary, and I.
10303 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
10305 <p><b>Footnotes</b>
10306 <p><small><a name="note192" href="#note192">192)</a> See ''future library directions'' (<a href="#7.31.1">7.31.1</a>).
10308 <p><small><a name="note193" href="#note193">193)</a> The imaginary unit is a number i such that i 2 = -1.
10310 <p><small><a name="note194" href="#note194">194)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
10313 <p><small><a href="#Contents">Contents</a></small>
10314 <h4><a name="7.3.2" href="#7.3.2">7.3.2 Conventions</a></h4>
10315 <p><a name="7.3.2p1" href="#7.3.2p1"><small>1</small></a>
10316 Values are interpreted as radians, not degrees. An implementation may set errno but is
10319 <p><small><a href="#Contents">Contents</a></small>
10320 <h4><a name="7.3.3" href="#7.3.3">7.3.3 Branch cuts</a></h4>
10321 <p><a name="7.3.3p1" href="#7.3.3p1"><small>1</small></a>
10322 Some of the functions below have branch cuts, across which the function is
10323 discontinuous. For implementations with a signed zero (including all IEC 60559
10324 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
10325 one side of a cut from another so the function is continuous (except for format
10326 limitations) as the cut is approached from either side. For example, for the square root
10327 function, which has a branch cut along the negative real axis, the top of the cut, with
10328 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
10329 imaginary part -0, maps to the negative imaginary axis.
10330 <p><a name="7.3.3p2" href="#7.3.3p2"><small>2</small></a>
10331 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
10332 sides of branch cuts. These implementations shall map a cut so the function is continuous
10333 as the cut is approached coming around the finite endpoint of the cut in a counter
10334 clockwise direction. (Branch cuts for the functions specified here have just one finite
10335 endpoint.) For example, for the square root function, coming counter clockwise around
10336 the finite endpoint of the cut along the negative real axis approaches the cut from above,
10337 so the cut maps to the positive imaginary axis.
10339 <p><small><a href="#Contents">Contents</a></small>
10340 <h4><a name="7.3.4" href="#7.3.4">7.3.4 The CX_LIMITED_RANGE pragma</a></h4>
10342 <p><a name="7.3.4p1" href="#7.3.4p1"><small>1</small></a>
10344 #include <a href="#7.3"><complex.h></a>
10345 #pragma STDC CX_LIMITED_RANGE on-off-switch
10347 <p><b>Description</b>
10348 <p><a name="7.3.4p2" href="#7.3.4p2"><small>2</small></a>
10349 The usual mathematical formulas for complex multiply, divide, and absolute value are
10350 problematic because of their treatment of infinities and because of undue overflow and
10351 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
10352 implementation that (where the state is ''on'') the usual mathematical formulas are
10353 acceptable.<sup><a href="#note195"><b>195)</b></a></sup> The pragma can occur either outside external declarations or preceding all
10354 explicit declarations and statements inside a compound statement. When outside external
10355 declarations, the pragma takes effect from its occurrence until another
10356 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
10357 When inside a compound statement, the pragma takes effect from its occurrence until
10358 another CX_LIMITED_RANGE pragma is encountered (including within a nested
10359 compound statement), or until the end of the compound statement; at the end of a
10360 compound statement the state for the pragma is restored to its condition just before the
10362 compound statement. If this pragma is used in any other context, the behavior is
10363 undefined. The default state for the pragma is ''off''.
10365 <p><b>Footnotes</b>
10366 <p><small><a name="note195" href="#note195">195)</a> The purpose of the pragma is to allow the implementation to use the formulas:
10369 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
10370 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
10371 | x + iy | = (sqrt) x 2 + y 2
10374 where the programmer can determine they are safe.
10377 <p><small><a href="#Contents">Contents</a></small>
10378 <h4><a name="7.3.5" href="#7.3.5">7.3.5 Trigonometric functions</a></h4>
10380 <p><small><a href="#Contents">Contents</a></small>
10381 <h5><a name="7.3.5.1" href="#7.3.5.1">7.3.5.1 The cacos functions</a></h5>
10383 <p><a name="7.3.5.1p1" href="#7.3.5.1p1"><small>1</small></a>
10385 #include <a href="#7.3"><complex.h></a>
10386 double complex cacos(double complex z);
10387 float complex cacosf(float complex z);
10388 long double complex cacosl(long double complex z);
10390 <p><b>Description</b>
10391 <p><a name="7.3.5.1p2" href="#7.3.5.1p2"><small>2</small></a>
10392 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
10393 interval [-1, +1] along the real axis.
10395 <p><a name="7.3.5.1p3" href="#7.3.5.1p3"><small>3</small></a>
10396 The cacos functions return the complex arc cosine value, in the range of a strip
10397 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
10400 <p><small><a href="#Contents">Contents</a></small>
10401 <h5><a name="7.3.5.2" href="#7.3.5.2">7.3.5.2 The casin functions</a></h5>
10403 <p><a name="7.3.5.2p1" href="#7.3.5.2p1"><small>1</small></a>
10405 #include <a href="#7.3"><complex.h></a>
10406 double complex casin(double complex z);
10407 float complex casinf(float complex z);
10408 long double complex casinl(long double complex z);
10410 <p><b>Description</b>
10411 <p><a name="7.3.5.2p2" href="#7.3.5.2p2"><small>2</small></a>
10412 The casin functions compute the complex arc sine of z, with branch cuts outside the
10413 interval [-1, +1] along the real axis.
10415 <p><a name="7.3.5.2p3" href="#7.3.5.2p3"><small>3</small></a>
10416 The casin functions return the complex arc sine value, in the range of a strip
10417 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10420 along the real axis.
10422 <p><small><a href="#Contents">Contents</a></small>
10423 <h5><a name="7.3.5.3" href="#7.3.5.3">7.3.5.3 The catan functions</a></h5>
10425 <p><a name="7.3.5.3p1" href="#7.3.5.3p1"><small>1</small></a>
10427 #include <a href="#7.3"><complex.h></a>
10428 double complex catan(double complex z);
10429 float complex catanf(float complex z);
10430 long double complex catanl(long double complex z);
10432 <p><b>Description</b>
10433 <p><a name="7.3.5.3p2" href="#7.3.5.3p2"><small>2</small></a>
10434 The catan functions compute the complex arc tangent of z, with branch cuts outside the
10435 interval [-i, +i] along the imaginary axis.
10437 <p><a name="7.3.5.3p3" href="#7.3.5.3p3"><small>3</small></a>
10438 The catan functions return the complex arc tangent value, in the range of a strip
10439 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10440 along the real axis.
10442 <p><small><a href="#Contents">Contents</a></small>
10443 <h5><a name="7.3.5.4" href="#7.3.5.4">7.3.5.4 The ccos functions</a></h5>
10445 <p><a name="7.3.5.4p1" href="#7.3.5.4p1"><small>1</small></a>
10447 #include <a href="#7.3"><complex.h></a>
10448 double complex ccos(double complex z);
10449 float complex ccosf(float complex z);
10450 long double complex ccosl(long double complex z);
10452 <p><b>Description</b>
10453 <p><a name="7.3.5.4p2" href="#7.3.5.4p2"><small>2</small></a>
10454 The ccos functions compute the complex cosine of z.
10456 <p><a name="7.3.5.4p3" href="#7.3.5.4p3"><small>3</small></a>
10457 The ccos functions return the complex cosine value.
10459 <p><small><a href="#Contents">Contents</a></small>
10460 <h5><a name="7.3.5.5" href="#7.3.5.5">7.3.5.5 The csin functions</a></h5>
10462 <p><a name="7.3.5.5p1" href="#7.3.5.5p1"><small>1</small></a>
10464 #include <a href="#7.3"><complex.h></a>
10465 double complex csin(double complex z);
10466 float complex csinf(float complex z);
10467 long double complex csinl(long double complex z);
10469 <p><b>Description</b>
10470 <p><a name="7.3.5.5p2" href="#7.3.5.5p2"><small>2</small></a>
10471 The csin functions compute the complex sine of z.
10474 <p><a name="7.3.5.5p3" href="#7.3.5.5p3"><small>3</small></a>
10475 The csin functions return the complex sine value.
10477 <p><small><a href="#Contents">Contents</a></small>
10478 <h5><a name="7.3.5.6" href="#7.3.5.6">7.3.5.6 The ctan functions</a></h5>
10480 <p><a name="7.3.5.6p1" href="#7.3.5.6p1"><small>1</small></a>
10482 #include <a href="#7.3"><complex.h></a>
10483 double complex ctan(double complex z);
10484 float complex ctanf(float complex z);
10485 long double complex ctanl(long double complex z);
10487 <p><b>Description</b>
10488 <p><a name="7.3.5.6p2" href="#7.3.5.6p2"><small>2</small></a>
10489 The ctan functions compute the complex tangent of z.
10491 <p><a name="7.3.5.6p3" href="#7.3.5.6p3"><small>3</small></a>
10492 The ctan functions return the complex tangent value.
10494 <p><small><a href="#Contents">Contents</a></small>
10495 <h4><a name="7.3.6" href="#7.3.6">7.3.6 Hyperbolic functions</a></h4>
10497 <p><small><a href="#Contents">Contents</a></small>
10498 <h5><a name="7.3.6.1" href="#7.3.6.1">7.3.6.1 The cacosh functions</a></h5>
10500 <p><a name="7.3.6.1p1" href="#7.3.6.1p1"><small>1</small></a>
10502 #include <a href="#7.3"><complex.h></a>
10503 double complex cacosh(double complex z);
10504 float complex cacoshf(float complex z);
10505 long double complex cacoshl(long double complex z);
10507 <p><b>Description</b>
10508 <p><a name="7.3.6.1p2" href="#7.3.6.1p2"><small>2</small></a>
10509 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
10510 cut at values less than 1 along the real axis.
10512 <p><a name="7.3.6.1p3" href="#7.3.6.1p3"><small>3</small></a>
10513 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
10514 half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
10517 <p><small><a href="#Contents">Contents</a></small>
10518 <h5><a name="7.3.6.2" href="#7.3.6.2">7.3.6.2 The casinh functions</a></h5>
10520 <p><a name="7.3.6.2p1" href="#7.3.6.2p1"><small>1</small></a>
10523 #include <a href="#7.3"><complex.h></a>
10524 double complex casinh(double complex z);
10525 float complex casinhf(float complex z);
10526 long double complex casinhl(long double complex z);
10528 <p><b>Description</b>
10529 <p><a name="7.3.6.2p2" href="#7.3.6.2p2"><small>2</small></a>
10530 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
10531 outside the interval [-i, +i] along the imaginary axis.
10533 <p><a name="7.3.6.2p3" href="#7.3.6.2p3"><small>3</small></a>
10534 The casinh functions return the complex arc hyperbolic sine value, in the range of a
10535 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10536 along the imaginary axis.
10538 <p><small><a href="#Contents">Contents</a></small>
10539 <h5><a name="7.3.6.3" href="#7.3.6.3">7.3.6.3 The catanh functions</a></h5>
10541 <p><a name="7.3.6.3p1" href="#7.3.6.3p1"><small>1</small></a>
10543 #include <a href="#7.3"><complex.h></a>
10544 double complex catanh(double complex z);
10545 float complex catanhf(float complex z);
10546 long double complex catanhl(long double complex z);
10548 <p><b>Description</b>
10549 <p><a name="7.3.6.3p2" href="#7.3.6.3p2"><small>2</small></a>
10550 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
10551 cuts outside the interval [-1, +1] along the real axis.
10553 <p><a name="7.3.6.3p3" href="#7.3.6.3p3"><small>3</small></a>
10554 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
10555 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10556 along the imaginary axis.
10558 <p><small><a href="#Contents">Contents</a></small>
10559 <h5><a name="7.3.6.4" href="#7.3.6.4">7.3.6.4 The ccosh functions</a></h5>
10561 <p><a name="7.3.6.4p1" href="#7.3.6.4p1"><small>1</small></a>
10563 #include <a href="#7.3"><complex.h></a>
10564 double complex ccosh(double complex z);
10565 float complex ccoshf(float complex z);
10566 long double complex ccoshl(long double complex z);
10568 <p><b>Description</b>
10569 <p><a name="7.3.6.4p2" href="#7.3.6.4p2"><small>2</small></a>
10570 The ccosh functions compute the complex hyperbolic cosine of z.
10572 <p><a name="7.3.6.4p3" href="#7.3.6.4p3"><small>3</small></a>
10573 The ccosh functions return the complex hyperbolic cosine value.
10576 <p><small><a href="#Contents">Contents</a></small>
10577 <h5><a name="7.3.6.5" href="#7.3.6.5">7.3.6.5 The csinh functions</a></h5>
10579 <p><a name="7.3.6.5p1" href="#7.3.6.5p1"><small>1</small></a>
10581 #include <a href="#7.3"><complex.h></a>
10582 double complex csinh(double complex z);
10583 float complex csinhf(float complex z);
10584 long double complex csinhl(long double complex z);
10586 <p><b>Description</b>
10587 <p><a name="7.3.6.5p2" href="#7.3.6.5p2"><small>2</small></a>
10588 The csinh functions compute the complex hyperbolic sine of z.
10590 <p><a name="7.3.6.5p3" href="#7.3.6.5p3"><small>3</small></a>
10591 The csinh functions return the complex hyperbolic sine value.
10593 <p><small><a href="#Contents">Contents</a></small>
10594 <h5><a name="7.3.6.6" href="#7.3.6.6">7.3.6.6 The ctanh functions</a></h5>
10596 <p><a name="7.3.6.6p1" href="#7.3.6.6p1"><small>1</small></a>
10598 #include <a href="#7.3"><complex.h></a>
10599 double complex ctanh(double complex z);
10600 float complex ctanhf(float complex z);
10601 long double complex ctanhl(long double complex z);
10603 <p><b>Description</b>
10604 <p><a name="7.3.6.6p2" href="#7.3.6.6p2"><small>2</small></a>
10605 The ctanh functions compute the complex hyperbolic tangent of z.
10607 <p><a name="7.3.6.6p3" href="#7.3.6.6p3"><small>3</small></a>
10608 The ctanh functions return the complex hyperbolic tangent value.
10610 <p><small><a href="#Contents">Contents</a></small>
10611 <h4><a name="7.3.7" href="#7.3.7">7.3.7 Exponential and logarithmic functions</a></h4>
10613 <p><small><a href="#Contents">Contents</a></small>
10614 <h5><a name="7.3.7.1" href="#7.3.7.1">7.3.7.1 The cexp functions</a></h5>
10616 <p><a name="7.3.7.1p1" href="#7.3.7.1p1"><small>1</small></a>
10618 #include <a href="#7.3"><complex.h></a>
10619 double complex cexp(double complex z);
10620 float complex cexpf(float complex z);
10621 long double complex cexpl(long double complex z);
10623 <p><b>Description</b>
10624 <p><a name="7.3.7.1p2" href="#7.3.7.1p2"><small>2</small></a>
10625 The cexp functions compute the complex base-e exponential of z.
10627 <p><a name="7.3.7.1p3" href="#7.3.7.1p3"><small>3</small></a>
10628 The cexp functions return the complex base-e exponential value.
10631 <p><small><a href="#Contents">Contents</a></small>
10632 <h5><a name="7.3.7.2" href="#7.3.7.2">7.3.7.2 The clog functions</a></h5>
10634 <p><a name="7.3.7.2p1" href="#7.3.7.2p1"><small>1</small></a>
10636 #include <a href="#7.3"><complex.h></a>
10637 double complex clog(double complex z);
10638 float complex clogf(float complex z);
10639 long double complex clogl(long double complex z);
10641 <p><b>Description</b>
10642 <p><a name="7.3.7.2p2" href="#7.3.7.2p2"><small>2</small></a>
10643 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
10644 cut along the negative real axis.
10646 <p><a name="7.3.7.2p3" href="#7.3.7.2p3"><small>3</small></a>
10647 The clog functions return the complex natural logarithm value, in the range of a strip
10648 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
10651 <p><small><a href="#Contents">Contents</a></small>
10652 <h4><a name="7.3.8" href="#7.3.8">7.3.8 Power and absolute-value functions</a></h4>
10654 <p><small><a href="#Contents">Contents</a></small>
10655 <h5><a name="7.3.8.1" href="#7.3.8.1">7.3.8.1 The cabs functions</a></h5>
10657 <p><a name="7.3.8.1p1" href="#7.3.8.1p1"><small>1</small></a>
10659 #include <a href="#7.3"><complex.h></a>
10660 double cabs(double complex z);
10661 float cabsf(float complex z);
10662 long double cabsl(long double complex z);
10664 <p><b>Description</b>
10665 <p><a name="7.3.8.1p2" href="#7.3.8.1p2"><small>2</small></a>
10666 The cabs functions compute the complex absolute value (also called norm, modulus, or
10669 <p><a name="7.3.8.1p3" href="#7.3.8.1p3"><small>3</small></a>
10670 The cabs functions return the complex absolute value.
10672 <p><small><a href="#Contents">Contents</a></small>
10673 <h5><a name="7.3.8.2" href="#7.3.8.2">7.3.8.2 The cpow functions</a></h5>
10675 <p><a name="7.3.8.2p1" href="#7.3.8.2p1"><small>1</small></a>
10678 #include <a href="#7.3"><complex.h></a>
10679 double complex cpow(double complex x, double complex y);
10680 float complex cpowf(float complex x, float complex y);
10681 long double complex cpowl(long double complex x,
10682 long double complex y);
10684 <p><b>Description</b>
10685 <p><a name="7.3.8.2p2" href="#7.3.8.2p2"><small>2</small></a>
10686 The cpow functions compute the complex power function xy , with a branch cut for the
10687 first parameter along the negative real axis.
10689 <p><a name="7.3.8.2p3" href="#7.3.8.2p3"><small>3</small></a>
10690 The cpow functions return the complex power function value.
10692 <p><small><a href="#Contents">Contents</a></small>
10693 <h5><a name="7.3.8.3" href="#7.3.8.3">7.3.8.3 The csqrt functions</a></h5>
10695 <p><a name="7.3.8.3p1" href="#7.3.8.3p1"><small>1</small></a>
10697 #include <a href="#7.3"><complex.h></a>
10698 double complex csqrt(double complex z);
10699 float complex csqrtf(float complex z);
10700 long double complex csqrtl(long double complex z);
10702 <p><b>Description</b>
10703 <p><a name="7.3.8.3p2" href="#7.3.8.3p2"><small>2</small></a>
10704 The csqrt functions compute the complex square root of z, with a branch cut along the
10705 negative real axis.
10707 <p><a name="7.3.8.3p3" href="#7.3.8.3p3"><small>3</small></a>
10708 The csqrt functions return the complex square root value, in the range of the right half-
10709 plane (including the imaginary axis).
10711 <p><small><a href="#Contents">Contents</a></small>
10712 <h4><a name="7.3.9" href="#7.3.9">7.3.9 Manipulation functions</a></h4>
10714 <p><small><a href="#Contents">Contents</a></small>
10715 <h5><a name="7.3.9.1" href="#7.3.9.1">7.3.9.1 The carg functions</a></h5>
10717 <p><a name="7.3.9.1p1" href="#7.3.9.1p1"><small>1</small></a>
10719 #include <a href="#7.3"><complex.h></a>
10720 double carg(double complex z);
10721 float cargf(float complex z);
10722 long double cargl(long double complex z);
10724 <p><b>Description</b>
10725 <p><a name="7.3.9.1p2" href="#7.3.9.1p2"><small>2</small></a>
10726 The carg functions compute the argument (also called phase angle) of z, with a branch
10727 cut along the negative real axis.
10729 <p><a name="7.3.9.1p3" href="#7.3.9.1p3"><small>3</small></a>
10730 The carg functions return the value of the argument in the interval [-pi , +pi ].
10733 <p><small><a href="#Contents">Contents</a></small>
10734 <h5><a name="7.3.9.2" href="#7.3.9.2">7.3.9.2 The cimag functions</a></h5>
10736 <p><a name="7.3.9.2p1" href="#7.3.9.2p1"><small>1</small></a>
10738 #include <a href="#7.3"><complex.h></a>
10739 double cimag(double complex z);
10740 float cimagf(float complex z);
10741 long double cimagl(long double complex z);
10743 <p><b>Description</b>
10744 <p><a name="7.3.9.2p2" href="#7.3.9.2p2"><small>2</small></a>
10745 The cimag functions compute the imaginary part of z.<sup><a href="#note196"><b>196)</b></a></sup>
10747 <p><a name="7.3.9.2p3" href="#7.3.9.2p3"><small>3</small></a>
10748 The cimag functions return the imaginary part value (as a real).
10750 <p><b>Footnotes</b>
10751 <p><small><a name="note196" href="#note196">196)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10754 <p><small><a href="#Contents">Contents</a></small>
10755 <h5><a name="7.3.9.3" href="#7.3.9.3">7.3.9.3 The CMPLX macros</a></h5>
10757 <p><a name="7.3.9.3p1" href="#7.3.9.3p1"><small>1</small></a>
10759 #include <a href="#7.3"><complex.h></a>
10760 double complex CMPLX(double x, double y);
10761 float complex CMPLXF(float x, float y);
10762 long double complex CMPLXL(long double x, long double y);
10764 <p><b>Description</b>
10765 <p><a name="7.3.9.3p2" href="#7.3.9.3p2"><small>2</small></a>
10766 The CMPLX macros expand to an expression of the specified complex type, with the real
10767 part having the (converted) value of x and the imaginary part having the (converted)
10768 value of y. The resulting expression shall be suitable for use as an initializer for an object
10769 with static or thread storage duration, provided both arguments are likewise suitable.
10771 <p><a name="7.3.9.3p3" href="#7.3.9.3p3"><small>3</small></a>
10772 The CMPLX macros return the complex value x + i y.
10773 <p><a name="7.3.9.3p4" href="#7.3.9.3p4"><small>4</small></a>
10774 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
10776 #define CMPLX(x, y) ((double complex)((double)(x) + \
10777 _Imaginary_I * (double)(y)))
10778 #define CMPLXF(x, y) ((float complex)((float)(x) + \
10779 _Imaginary_I * (float)(y)))
10780 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
10781 _Imaginary_I * (long double)(y)))
10789 <p><small><a href="#Contents">Contents</a></small>
10790 <h5><a name="7.3.9.4" href="#7.3.9.4">7.3.9.4 The conj functions</a></h5>
10792 <p><a name="7.3.9.4p1" href="#7.3.9.4p1"><small>1</small></a>
10794 #include <a href="#7.3"><complex.h></a>
10795 double complex conj(double complex z);
10796 float complex conjf(float complex z);
10797 long double complex conjl(long double complex z);
10799 <p><b>Description</b>
10800 <p><a name="7.3.9.4p2" href="#7.3.9.4p2"><small>2</small></a>
10801 The conj functions compute the complex conjugate of z, by reversing the sign of its
10804 <p><a name="7.3.9.4p3" href="#7.3.9.4p3"><small>3</small></a>
10805 The conj functions return the complex conjugate value.
10807 <p><small><a href="#Contents">Contents</a></small>
10808 <h5><a name="7.3.9.5" href="#7.3.9.5">7.3.9.5 The cproj functions</a></h5>
10810 <p><a name="7.3.9.5p1" href="#7.3.9.5p1"><small>1</small></a>
10812 #include <a href="#7.3"><complex.h></a>
10813 double complex cproj(double complex z);
10814 float complex cprojf(float complex z);
10815 long double complex cprojl(long double complex z);
10817 <p><b>Description</b>
10818 <p><a name="7.3.9.5p2" href="#7.3.9.5p2"><small>2</small></a>
10819 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
10820 z except that all complex infinities (even those with one infinite part and one NaN part)
10821 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
10824 INFINITY + I * copysign(0.0, cimag(z))
10827 <p><a name="7.3.9.5p3" href="#7.3.9.5p3"><small>3</small></a>
10828 The cproj functions return the value of the projection onto the Riemann sphere.
10830 <p><small><a href="#Contents">Contents</a></small>
10831 <h5><a name="7.3.9.6" href="#7.3.9.6">7.3.9.6 The creal functions</a></h5>
10833 <p><a name="7.3.9.6p1" href="#7.3.9.6p1"><small>1</small></a>
10835 #include <a href="#7.3"><complex.h></a>
10836 double creal(double complex z);
10837 float crealf(float complex z);
10838 long double creall(long double complex z);
10840 <p><b>Description</b>
10841 <p><a name="7.3.9.6p2" href="#7.3.9.6p2"><small>2</small></a>
10842 The creal functions compute the real part of z.<sup><a href="#note197"><b>197)</b></a></sup>
10845 <p><a name="7.3.9.6p3" href="#7.3.9.6p3"><small>3</small></a>
10846 The creal functions return the real part value.
10853 <p><b>Footnotes</b>
10854 <p><small><a name="note197" href="#note197">197)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10857 <p><small><a href="#Contents">Contents</a></small>
10858 <h3><a name="7.4" href="#7.4">7.4 Character handling <ctype.h></a></h3>
10859 <p><a name="7.4p1" href="#7.4p1"><small>1</small></a>
10860 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
10861 characters.<sup><a href="#note198"><b>198)</b></a></sup> In all cases the argument is an int, the value of which shall be
10862 representable as an unsigned char or shall equal the value of the macro EOF. If the
10863 argument has any other value, the behavior is undefined.
10864 <p><a name="7.4p2" href="#7.4p2"><small>2</small></a>
10865 The behavior of these functions is affected by the current locale. Those functions that
10866 have locale-specific aspects only when not in the "C" locale are noted below.
10867 <p><a name="7.4p3" href="#7.4p3"><small>3</small></a>
10868 The term printing character refers to a member of a locale-specific set of characters, each
10869 of which occupies one printing position on a display device; the term control character
10870 refers to a member of a locale-specific set of characters that are not printing
10871 characters.<sup><a href="#note199"><b>199)</b></a></sup> All letters and digits are printing characters.
10872 <p><b> Forward references</b>: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
10874 <p><b>Footnotes</b>
10875 <p><small><a name="note198" href="#note198">198)</a> See ''future library directions'' (<a href="#7.31.2">7.31.2</a>).
10877 <p><small><a name="note199" href="#note199">199)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
10878 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
10879 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
10882 <p><small><a href="#Contents">Contents</a></small>
10883 <h4><a name="7.4.1" href="#7.4.1">7.4.1 Character classification functions</a></h4>
10884 <p><a name="7.4.1p1" href="#7.4.1p1"><small>1</small></a>
10885 The functions in this subclause return nonzero (true) if and only if the value of the
10886 argument c conforms to that in the description of the function.
10888 <p><small><a href="#Contents">Contents</a></small>
10889 <h5><a name="7.4.1.1" href="#7.4.1.1">7.4.1.1 The isalnum function</a></h5>
10891 <p><a name="7.4.1.1p1" href="#7.4.1.1p1"><small>1</small></a>
10893 #include <a href="#7.4"><ctype.h></a>
10894 int isalnum(int c);
10896 <p><b>Description</b>
10897 <p><a name="7.4.1.1p2" href="#7.4.1.1p2"><small>2</small></a>
10898 The isalnum function tests for any character for which isalpha or isdigit is true.
10900 <p><small><a href="#Contents">Contents</a></small>
10901 <h5><a name="7.4.1.2" href="#7.4.1.2">7.4.1.2 The isalpha function</a></h5>
10903 <p><a name="7.4.1.2p1" href="#7.4.1.2p1"><small>1</small></a>
10905 #include <a href="#7.4"><ctype.h></a>
10906 int isalpha(int c);
10908 <p><b>Description</b>
10909 <p><a name="7.4.1.2p2" href="#7.4.1.2p2"><small>2</small></a>
10910 The isalpha function tests for any character for which isupper or islower is true,
10911 or any character that is one of a locale-specific set of alphabetic characters for which
10916 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note200"><b>200)</b></a></sup> In the "C" locale,
10917 isalpha returns true only for the characters for which isupper or islower is true.
10919 <p><b>Footnotes</b>
10920 <p><small><a name="note200" href="#note200">200)</a> The functions islower and isupper test true or false separately for each of these additional
10921 characters; all four combinations are possible.
10924 <p><small><a href="#Contents">Contents</a></small>
10925 <h5><a name="7.4.1.3" href="#7.4.1.3">7.4.1.3 The isblank function</a></h5>
10927 <p><a name="7.4.1.3p1" href="#7.4.1.3p1"><small>1</small></a>
10929 #include <a href="#7.4"><ctype.h></a>
10930 int isblank(int c);
10932 <p><b>Description</b>
10933 <p><a name="7.4.1.3p2" href="#7.4.1.3p2"><small>2</small></a>
10934 The isblank function tests for any character that is a standard blank character or is one
10935 of a locale-specific set of characters for which isspace is true and that is used to
10936 separate words within a line of text. The standard blank characters are the following:
10937 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
10938 for the standard blank characters.
10940 <p><small><a href="#Contents">Contents</a></small>
10941 <h5><a name="7.4.1.4" href="#7.4.1.4">7.4.1.4 The iscntrl function</a></h5>
10943 <p><a name="7.4.1.4p1" href="#7.4.1.4p1"><small>1</small></a>
10945 #include <a href="#7.4"><ctype.h></a>
10946 int iscntrl(int c);
10948 <p><b>Description</b>
10949 <p><a name="7.4.1.4p2" href="#7.4.1.4p2"><small>2</small></a>
10950 The iscntrl function tests for any control character.
10952 <p><small><a href="#Contents">Contents</a></small>
10953 <h5><a name="7.4.1.5" href="#7.4.1.5">7.4.1.5 The isdigit function</a></h5>
10955 <p><a name="7.4.1.5p1" href="#7.4.1.5p1"><small>1</small></a>
10957 #include <a href="#7.4"><ctype.h></a>
10958 int isdigit(int c);
10960 <p><b>Description</b>
10961 <p><a name="7.4.1.5p2" href="#7.4.1.5p2"><small>2</small></a>
10962 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
10964 <p><small><a href="#Contents">Contents</a></small>
10965 <h5><a name="7.4.1.6" href="#7.4.1.6">7.4.1.6 The isgraph function</a></h5>
10967 <p><a name="7.4.1.6p1" href="#7.4.1.6p1"><small>1</small></a>
10969 #include <a href="#7.4"><ctype.h></a>
10970 int isgraph(int c);
10977 <p><b>Description</b>
10978 <p><a name="7.4.1.6p2" href="#7.4.1.6p2"><small>2</small></a>
10979 The isgraph function tests for any printing character except space (' ').
10981 <p><small><a href="#Contents">Contents</a></small>
10982 <h5><a name="7.4.1.7" href="#7.4.1.7">7.4.1.7 The islower function</a></h5>
10984 <p><a name="7.4.1.7p1" href="#7.4.1.7p1"><small>1</small></a>
10986 #include <a href="#7.4"><ctype.h></a>
10987 int islower(int c);
10989 <p><b>Description</b>
10990 <p><a name="7.4.1.7p2" href="#7.4.1.7p2"><small>2</small></a>
10991 The islower function tests for any character that is a lowercase letter or is one of a
10992 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
10993 isspace is true. In the "C" locale, islower returns true only for the lowercase
10994 letters (as defined in <a href="#5.2.1">5.2.1</a>).
10996 <p><small><a href="#Contents">Contents</a></small>
10997 <h5><a name="7.4.1.8" href="#7.4.1.8">7.4.1.8 The isprint function</a></h5>
10999 <p><a name="7.4.1.8p1" href="#7.4.1.8p1"><small>1</small></a>
11001 #include <a href="#7.4"><ctype.h></a>
11002 int isprint(int c);
11004 <p><b>Description</b>
11005 <p><a name="7.4.1.8p2" href="#7.4.1.8p2"><small>2</small></a>
11006 The isprint function tests for any printing character including space (' ').
11008 <p><small><a href="#Contents">Contents</a></small>
11009 <h5><a name="7.4.1.9" href="#7.4.1.9">7.4.1.9 The ispunct function</a></h5>
11011 <p><a name="7.4.1.9p1" href="#7.4.1.9p1"><small>1</small></a>
11013 #include <a href="#7.4"><ctype.h></a>
11014 int ispunct(int c);
11016 <p><b>Description</b>
11017 <p><a name="7.4.1.9p2" href="#7.4.1.9p2"><small>2</small></a>
11018 The ispunct function tests for any printing character that is one of a locale-specific set
11019 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
11020 locale, ispunct returns true for every printing character for which neither isspace
11021 nor isalnum is true.
11023 <p><small><a href="#Contents">Contents</a></small>
11024 <h5><a name="7.4.1.10" href="#7.4.1.10">7.4.1.10 The isspace function</a></h5>
11026 <p><a name="7.4.1.10p1" href="#7.4.1.10p1"><small>1</small></a>
11028 #include <a href="#7.4"><ctype.h></a>
11029 int isspace(int c);
11031 <p><b>Description</b>
11032 <p><a name="7.4.1.10p2" href="#7.4.1.10p2"><small>2</small></a>
11033 The isspace function tests for any character that is a standard white-space character or
11034 is one of a locale-specific set of characters for which isalnum is false. The standard
11036 white-space characters are the following: space (' '), form feed ('\f'), new-line
11037 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
11038 "C" locale, isspace returns true only for the standard white-space characters.
11040 <p><small><a href="#Contents">Contents</a></small>
11041 <h5><a name="7.4.1.11" href="#7.4.1.11">7.4.1.11 The isupper function</a></h5>
11043 <p><a name="7.4.1.11p1" href="#7.4.1.11p1"><small>1</small></a>
11045 #include <a href="#7.4"><ctype.h></a>
11046 int isupper(int c);
11048 <p><b>Description</b>
11049 <p><a name="7.4.1.11p2" href="#7.4.1.11p2"><small>2</small></a>
11050 The isupper function tests for any character that is an uppercase letter or is one of a
11051 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
11052 isspace is true. In the "C" locale, isupper returns true only for the uppercase
11053 letters (as defined in <a href="#5.2.1">5.2.1</a>).
11055 <p><small><a href="#Contents">Contents</a></small>
11056 <h5><a name="7.4.1.12" href="#7.4.1.12">7.4.1.12 The isxdigit function</a></h5>
11058 <p><a name="7.4.1.12p1" href="#7.4.1.12p1"><small>1</small></a>
11060 #include <a href="#7.4"><ctype.h></a>
11061 int isxdigit(int c);
11063 <p><b>Description</b>
11064 <p><a name="7.4.1.12p2" href="#7.4.1.12p2"><small>2</small></a>
11065 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
11067 <p><small><a href="#Contents">Contents</a></small>
11068 <h4><a name="7.4.2" href="#7.4.2">7.4.2 Character case mapping functions</a></h4>
11070 <p><small><a href="#Contents">Contents</a></small>
11071 <h5><a name="7.4.2.1" href="#7.4.2.1">7.4.2.1 The tolower function</a></h5>
11073 <p><a name="7.4.2.1p1" href="#7.4.2.1p1"><small>1</small></a>
11075 #include <a href="#7.4"><ctype.h></a>
11076 int tolower(int c);
11078 <p><b>Description</b>
11079 <p><a name="7.4.2.1p2" href="#7.4.2.1p2"><small>2</small></a>
11080 The tolower function converts an uppercase letter to a corresponding lowercase letter.
11082 <p><a name="7.4.2.1p3" href="#7.4.2.1p3"><small>3</small></a>
11083 If the argument is a character for which isupper is true and there are one or more
11084 corresponding characters, as specified by the current locale, for which islower is true,
11085 the tolower function returns one of the corresponding characters (always the same one
11086 for any given locale); otherwise, the argument is returned unchanged.
11089 <p><small><a href="#Contents">Contents</a></small>
11090 <h5><a name="7.4.2.2" href="#7.4.2.2">7.4.2.2 The toupper function</a></h5>
11092 <p><a name="7.4.2.2p1" href="#7.4.2.2p1"><small>1</small></a>
11094 #include <a href="#7.4"><ctype.h></a>
11095 int toupper(int c);
11097 <p><b>Description</b>
11098 <p><a name="7.4.2.2p2" href="#7.4.2.2p2"><small>2</small></a>
11099 The toupper function converts a lowercase letter to a corresponding uppercase letter.
11101 <p><a name="7.4.2.2p3" href="#7.4.2.2p3"><small>3</small></a>
11102 If the argument is a character for which islower is true and there are one or more
11103 corresponding characters, as specified by the current locale, for which isupper is true,
11104 the toupper function returns one of the corresponding characters (always the same one
11105 for any given locale); otherwise, the argument is returned unchanged.
11108 <p><small><a href="#Contents">Contents</a></small>
11109 <h3><a name="7.5" href="#7.5">7.5 Errors <errno.h></a></h3>
11110 <p><a name="7.5p1" href="#7.5p1"><small>1</small></a>
11111 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
11113 <p><a name="7.5p2" href="#7.5p2"><small>2</small></a>
11120 which expand to integer constant expressions with type int, distinct positive values, and
11121 which are suitable for use in #if preprocessing directives; and
11125 which expands to a modifiable lvalue<sup><a href="#note201"><b>201)</b></a></sup> that has type int and thread local storage
11126 duration, the value of which is set to a positive error number by several library functions.
11127 If a macro definition is suppressed in order to access an actual object, or a program
11128 defines an identifier with the name errno, the behavior is undefined.
11129 <p><a name="7.5p3" href="#7.5p3"><small>3</small></a>
11130 The value of errno in the initial thread is zero at program startup (the initial value of
11131 errno in other threads is an indeterminate value), but is never set to zero by any library
11132 function.<sup><a href="#note202"><b>202)</b></a></sup> The value of errno may be set to nonzero by a library function call
11133 whether or not there is an error, provided the use of errno is not documented in the
11134 description of the function in this International Standard.
11135 <p><a name="7.5p4" href="#7.5p4"><small>4</small></a>
11136 Additional macro definitions, beginning with E and a digit or E and an uppercase
11137 letter,<sup><a href="#note203"><b>203)</b></a></sup> may also be specified by the implementation.
11144 <p><b>Footnotes</b>
11145 <p><small><a name="note201" href="#note201">201)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
11146 resulting from a function call (for example, *errno()).
11148 <p><small><a name="note202" href="#note202">202)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
11149 then inspect it before a subsequent library function call. Of course, a library function can save the
11150 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
11151 value is still zero just before the return.
11153 <p><small><a name="note203" href="#note203">203)</a> See ''future library directions'' (<a href="#7.31.3">7.31.3</a>).
11156 <p><small><a href="#Contents">Contents</a></small>
11157 <h3><a name="7.6" href="#7.6">7.6 Floating-point environment <fenv.h></a></h3>
11158 <p><a name="7.6p1" href="#7.6p1"><small>1</small></a>
11159 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
11160 provide access to the floating-point environment. The floating-point environment refers
11161 collectively to any floating-point status flags and control modes supported by the
11162 implementation.<sup><a href="#note204"><b>204)</b></a></sup> A floating-point status flag is a system variable whose value is set
11163 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
11164 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note205"><b>205)</b></a></sup> A floating-
11165 point control mode is a system variable whose value may be set by the user to affect the
11166 subsequent behavior of floating-point arithmetic.
11167 <p><a name="7.6p2" href="#7.6p2"><small>2</small></a>
11168 The floating-point environment has thread storage duration. The initial state for a
11169 thread's floating-point environment is the current state of the floating-point environment
11170 of the thread that creates it at the time of creation.
11171 <p><a name="7.6p3" href="#7.6p3"><small>3</small></a>
11172 Certain programming conventions support the intended model of use for the floating-
11173 point environment:<sup><a href="#note206"><b>206)</b></a></sup>
11175 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
11176 floating-point status flags, nor depend on the state of its caller's floating-point status
11177 flags unless the function is so documented;
11178 <li> a function call is assumed to require default floating-point control modes, unless its
11179 documentation promises otherwise;
11180 <li> a function call is assumed to have the potential for raising floating-point exceptions,
11181 unless its documentation promises otherwise.
11183 <p><a name="7.6p4" href="#7.6p4"><small>4</small></a>
11188 represents the entire floating-point environment.
11189 <p><a name="7.6p5" href="#7.6p5"><small>5</small></a>
11194 represents the floating-point status flags collectively, including any status the
11195 implementation associates with the flags.
11199 <p><a name="7.6p6" href="#7.6p6"><small>6</small></a>
11208 is defined if and only if the implementation supports the floating-point exception by
11209 means of the functions in 7.6.2.<sup><a href="#note207"><b>207)</b></a></sup> Additional implementation-defined floating-point
11210 exceptions, with macro definitions beginning with FE_ and an uppercase letter,<sup><a href="#note208"><b>208)</b></a></sup> may
11211 also be specified by the implementation. The defined macros expand to integer constant
11212 expressions with values such that bitwise ORs of all combinations of the macros result in
11213 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
11214 zero.<sup><a href="#note209"><b>209)</b></a></sup>
11215 <p><a name="7.6p7" href="#7.6p7"><small>7</small></a>
11220 is simply the bitwise OR of all floating-point exception macros defined by the
11221 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
11222 <p><a name="7.6p8" href="#7.6p8"><small>8</small></a>
11230 is defined if and only if the implementation supports getting and setting the represented
11231 rounding direction by means of the fegetround and fesetround functions.
11232 Additional implementation-defined rounding directions, with macro definitions beginning
11233 with FE_ and an uppercase letter,<sup><a href="#note210"><b>210)</b></a></sup> may also be specified by the implementation. The
11234 defined macros expand to integer constant expressions whose values are distinct
11235 nonnegative values.<sup><a href="#note211"><b>211)</b></a></sup>
11239 <p><a name="7.6p9" href="#7.6p9"><small>9</small></a>
11244 represents the default floating-point environment -- the one installed at program startup
11246 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
11248 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
11249 <p><a name="7.6p10" href="#7.6p10"><small>10</small></a>
11250 Additional implementation-defined environments, with macro definitions beginning with
11251 FE_ and an uppercase letter,<sup><a href="#note212"><b>212)</b></a></sup> and having type ''pointer to const-qualified fenv_t'',
11252 may also be specified by the implementation.
11254 <p><b>Footnotes</b>
11255 <p><small><a name="note204" href="#note204">204)</a> This header is designed to support the floating-point exception status flags and directed-rounding
11256 control modes required by IEC 60559, and other similar floating-point state information. It is also
11257 designed to facilitate code portability among all systems.
11259 <p><small><a name="note205" href="#note205">205)</a> A floating-point status flag is not an object and can be set more than once within an expression.
11261 <p><small><a name="note206" href="#note206">206)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
11262 unaware of them). The responsibilities associated with accessing the floating-point environment fall
11263 on the programmer or program that does so explicitly.
11265 <p><small><a name="note207" href="#note207">207)</a> The implementation supports a floating-point exception if there are circumstances where a call to at
11266 least one of the functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not
11267 necessary for all the functions to succeed all the time.
11269 <p><small><a name="note208" href="#note208">208)</a> See ''future library directions'' (<a href="#7.31.4">7.31.4</a>).
11271 <p><small><a name="note209" href="#note209">209)</a> The macros should be distinct powers of two.
11273 <p><small><a name="note210" href="#note210">210)</a> See ''future library directions'' (<a href="#7.31.4">7.31.4</a>).
11275 <p><small><a name="note211" href="#note211">211)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
11276 FLT_ROUNDS, they are not required to do so.
11278 <p><small><a name="note212" href="#note212">212)</a> See ''future library directions'' (<a href="#7.31.4">7.31.4</a>).
11281 <p><small><a href="#Contents">Contents</a></small>
11282 <h4><a name="7.6.1" href="#7.6.1">7.6.1 The FENV_ACCESS pragma</a></h4>
11284 <p><a name="7.6.1p1" href="#7.6.1p1"><small>1</small></a>
11286 #include <a href="#7.6"><fenv.h></a>
11287 #pragma STDC FENV_ACCESS on-off-switch
11289 <p><b>Description</b>
11290 <p><a name="7.6.1p2" href="#7.6.1p2"><small>2</small></a>
11291 The FENV_ACCESS pragma provides a means to inform the implementation when a
11292 program might access the floating-point environment to test floating-point status flags or
11293 run under non-default floating-point control modes.<sup><a href="#note213"><b>213)</b></a></sup> The pragma shall occur either
11294 outside external declarations or preceding all explicit declarations and statements inside a
11295 compound statement. When outside external declarations, the pragma takes effect from
11296 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
11297 the translation unit. When inside a compound statement, the pragma takes effect from its
11298 occurrence until another FENV_ACCESS pragma is encountered (including within a
11299 nested compound statement), or until the end of the compound statement; at the end of a
11300 compound statement the state for the pragma is restored to its condition just before the
11301 compound statement. If this pragma is used in any other context, the behavior is
11302 undefined. If part of a program tests floating-point status flags, sets floating-point control
11303 modes, or runs under non-default mode settings, but was translated with the state for the
11304 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
11305 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
11306 the program translated with FENV_ACCESS ''off'' to a part translated with
11307 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
11308 floating-point control modes have their default settings.)
11313 <p><a name="7.6.1p3" href="#7.6.1p3"><small>3</small></a>
11316 #include <a href="#7.6"><fenv.h></a>
11319 #pragma STDC FENV_ACCESS ON
11328 <p><a name="7.6.1p4" href="#7.6.1p4"><small>4</small></a>
11329 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
11330 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
11331 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note214"><b>214)</b></a></sup>
11334 <p><b>Footnotes</b>
11335 <p><small><a name="note213" href="#note213">213)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
11336 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
11337 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
11338 modes are in effect and the flags are not tested.
11340 <p><small><a name="note214" href="#note214">214)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
11341 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
11342 ''off'', just one evaluation of x + 1 would suffice.
11345 <p><small><a href="#Contents">Contents</a></small>
11346 <h4><a name="7.6.2" href="#7.6.2">7.6.2 Floating-point exceptions</a></h4>
11347 <p><a name="7.6.2p1" href="#7.6.2p1"><small>1</small></a>
11348 The following functions provide access to the floating-point status flags.<sup><a href="#note215"><b>215)</b></a></sup> The int
11349 input argument for the functions represents a subset of floating-point exceptions, and can
11350 be zero or the bitwise OR of one or more floating-point exception macros, for example
11351 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
11352 functions is undefined.
11354 <p><b>Footnotes</b>
11355 <p><small><a name="note215" href="#note215">215)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
11356 abstraction of flags that are either set or clear. An implementation may endow floating-point status
11357 flags with more information -- for example, the address of the code which first raised the floating-
11358 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
11362 <p><small><a href="#Contents">Contents</a></small>
11363 <h5><a name="7.6.2.1" href="#7.6.2.1">7.6.2.1 The feclearexcept function</a></h5>
11365 <p><a name="7.6.2.1p1" href="#7.6.2.1p1"><small>1</small></a>
11367 #include <a href="#7.6"><fenv.h></a>
11368 int feclearexcept(int excepts);
11370 <p><b>Description</b>
11371 <p><a name="7.6.2.1p2" href="#7.6.2.1p2"><small>2</small></a>
11372 The feclearexcept function attempts to clear the supported floating-point exceptions
11373 represented by its argument.
11375 <p><a name="7.6.2.1p3" href="#7.6.2.1p3"><small>3</small></a>
11376 The feclearexcept function returns zero if the excepts argument is zero or if all
11377 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
11382 <p><small><a href="#Contents">Contents</a></small>
11383 <h5><a name="7.6.2.2" href="#7.6.2.2">7.6.2.2 The fegetexceptflag function</a></h5>
11385 <p><a name="7.6.2.2p1" href="#7.6.2.2p1"><small>1</small></a>
11387 #include <a href="#7.6"><fenv.h></a>
11388 int fegetexceptflag(fexcept_t *flagp,
11391 <p><b>Description</b>
11392 <p><a name="7.6.2.2p2" href="#7.6.2.2p2"><small>2</small></a>
11393 The fegetexceptflag function attempts to store an implementation-defined
11394 representation of the states of the floating-point status flags indicated by the argument
11395 excepts in the object pointed to by the argument flagp.
11397 <p><a name="7.6.2.2p3" href="#7.6.2.2p3"><small>3</small></a>
11398 The fegetexceptflag function returns zero if the representation was successfully
11399 stored. Otherwise, it returns a nonzero value.
11401 <p><small><a href="#Contents">Contents</a></small>
11402 <h5><a name="7.6.2.3" href="#7.6.2.3">7.6.2.3 The feraiseexcept function</a></h5>
11404 <p><a name="7.6.2.3p1" href="#7.6.2.3p1"><small>1</small></a>
11406 #include <a href="#7.6"><fenv.h></a>
11407 int feraiseexcept(int excepts);
11409 <p><b>Description</b>
11410 <p><a name="7.6.2.3p2" href="#7.6.2.3p2"><small>2</small></a>
11411 The feraiseexcept function attempts to raise the supported floating-point exceptions
11412 represented by its argument.<sup><a href="#note216"><b>216)</b></a></sup> The order in which these floating-point exceptions are
11413 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
11414 additionally raises the ''inexact'' floating-point exception whenever it raises the
11415 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
11417 <p><a name="7.6.2.3p3" href="#7.6.2.3p3"><small>3</small></a>
11418 The feraiseexcept function returns zero if the excepts argument is zero or if all
11419 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
11426 <p><b>Footnotes</b>
11427 <p><small><a name="note216" href="#note216">216)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
11428 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
11429 in <a href="#F.8.6">F.8.6</a> is in the same spirit.
11432 <p><small><a href="#Contents">Contents</a></small>
11433 <h5><a name="7.6.2.4" href="#7.6.2.4">7.6.2.4 The fesetexceptflag function</a></h5>
11435 <p><a name="7.6.2.4p1" href="#7.6.2.4p1"><small>1</small></a>
11437 #include <a href="#7.6"><fenv.h></a>
11438 int fesetexceptflag(const fexcept_t *flagp,
11441 <p><b>Description</b>
11442 <p><a name="7.6.2.4p2" href="#7.6.2.4p2"><small>2</small></a>
11443 The fesetexceptflag function attempts to set the floating-point status flags
11444 indicated by the argument excepts to the states stored in the object pointed to by
11445 flagp. The value of *flagp shall have been set by a previous call to
11446 fegetexceptflag whose second argument represented at least those floating-point
11447 exceptions represented by the argument excepts. This function does not raise floating-
11448 point exceptions, but only sets the state of the flags.
11450 <p><a name="7.6.2.4p3" href="#7.6.2.4p3"><small>3</small></a>
11451 The fesetexceptflag function returns zero if the excepts argument is zero or if
11452 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
11455 <p><small><a href="#Contents">Contents</a></small>
11456 <h5><a name="7.6.2.5" href="#7.6.2.5">7.6.2.5 The fetestexcept function</a></h5>
11458 <p><a name="7.6.2.5p1" href="#7.6.2.5p1"><small>1</small></a>
11460 #include <a href="#7.6"><fenv.h></a>
11461 int fetestexcept(int excepts);
11463 <p><b>Description</b>
11464 <p><a name="7.6.2.5p2" href="#7.6.2.5p2"><small>2</small></a>
11465 The fetestexcept function determines which of a specified subset of the floating-
11466 point exception flags are currently set. The excepts argument specifies the floating-
11467 point status flags to be queried.<sup><a href="#note217"><b>217)</b></a></sup>
11469 <p><a name="7.6.2.5p3" href="#7.6.2.5p3"><small>3</small></a>
11470 The fetestexcept function returns the value of the bitwise OR of the floating-point
11471 exception macros corresponding to the currently set floating-point exceptions included in
11473 <p><a name="7.6.2.5p4" href="#7.6.2.5p4"><small>4</small></a>
11474 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
11481 #include <a href="#7.6"><fenv.h></a>
11484 #pragma STDC FENV_ACCESS ON
11486 feclearexcept(FE_INVALID | FE_OVERFLOW);
11487 // maybe raise exceptions
11488 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
11489 if (set_excepts & FE_INVALID) f();
11490 if (set_excepts & FE_OVERFLOW) g();
11496 <p><b>Footnotes</b>
11497 <p><small><a name="note217" href="#note217">217)</a> This mechanism allows testing several floating-point exceptions with just one function call.
11500 <p><small><a href="#Contents">Contents</a></small>
11501 <h4><a name="7.6.3" href="#7.6.3">7.6.3 Rounding</a></h4>
11502 <p><a name="7.6.3p1" href="#7.6.3p1"><small>1</small></a>
11503 The fegetround and fesetround functions provide control of rounding direction
11506 <p><small><a href="#Contents">Contents</a></small>
11507 <h5><a name="7.6.3.1" href="#7.6.3.1">7.6.3.1 The fegetround function</a></h5>
11509 <p><a name="7.6.3.1p1" href="#7.6.3.1p1"><small>1</small></a>
11511 #include <a href="#7.6"><fenv.h></a>
11512 int fegetround(void);
11514 <p><b>Description</b>
11515 <p><a name="7.6.3.1p2" href="#7.6.3.1p2"><small>2</small></a>
11516 The fegetround function gets the current rounding direction.
11518 <p><a name="7.6.3.1p3" href="#7.6.3.1p3"><small>3</small></a>
11519 The fegetround function returns the value of the rounding direction macro
11520 representing the current rounding direction or a negative value if there is no such
11521 rounding direction macro or the current rounding direction is not determinable.
11523 <p><small><a href="#Contents">Contents</a></small>
11524 <h5><a name="7.6.3.2" href="#7.6.3.2">7.6.3.2 The fesetround function</a></h5>
11526 <p><a name="7.6.3.2p1" href="#7.6.3.2p1"><small>1</small></a>
11528 #include <a href="#7.6"><fenv.h></a>
11529 int fesetround(int round);
11531 <p><b>Description</b>
11532 <p><a name="7.6.3.2p2" href="#7.6.3.2p2"><small>2</small></a>
11533 The fesetround function establishes the rounding direction represented by its
11534 argument round. If the argument is not equal to the value of a rounding direction macro,
11535 the rounding direction is not changed.
11537 <p><a name="7.6.3.2p3" href="#7.6.3.2p3"><small>3</small></a>
11538 The fesetround function returns zero if and only if the requested rounding direction
11541 <p><a name="7.6.3.2p4" href="#7.6.3.2p4"><small>4</small></a>
11542 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
11543 rounding direction fails.
11545 #include <a href="#7.6"><fenv.h></a>
11546 #include <a href="#7.2"><assert.h></a>
11547 void f(int round_dir)
11549 #pragma STDC FENV_ACCESS ON
11552 save_round = fegetround();
11553 setround_ok = fesetround(round_dir);
11554 assert(setround_ok == 0);
11556 fesetround(save_round);
11562 <p><small><a href="#Contents">Contents</a></small>
11563 <h4><a name="7.6.4" href="#7.6.4">7.6.4 Environment</a></h4>
11564 <p><a name="7.6.4p1" href="#7.6.4p1"><small>1</small></a>
11565 The functions in this section manage the floating-point environment -- status flags and
11566 control modes -- as one entity.
11568 <p><small><a href="#Contents">Contents</a></small>
11569 <h5><a name="7.6.4.1" href="#7.6.4.1">7.6.4.1 The fegetenv function</a></h5>
11571 <p><a name="7.6.4.1p1" href="#7.6.4.1p1"><small>1</small></a>
11573 #include <a href="#7.6"><fenv.h></a>
11574 int fegetenv(fenv_t *envp);
11576 <p><b>Description</b>
11577 <p><a name="7.6.4.1p2" href="#7.6.4.1p2"><small>2</small></a>
11578 The fegetenv function attempts to store the current floating-point environment in the
11579 object pointed to by envp.
11581 <p><a name="7.6.4.1p3" href="#7.6.4.1p3"><small>3</small></a>
11582 The fegetenv function returns zero if the environment was successfully stored.
11583 Otherwise, it returns a nonzero value.
11585 <p><small><a href="#Contents">Contents</a></small>
11586 <h5><a name="7.6.4.2" href="#7.6.4.2">7.6.4.2 The feholdexcept function</a></h5>
11588 <p><a name="7.6.4.2p1" href="#7.6.4.2p1"><small>1</small></a>
11590 #include <a href="#7.6"><fenv.h></a>
11591 int feholdexcept(fenv_t *envp);
11593 <p><b>Description</b>
11594 <p><a name="7.6.4.2p2" href="#7.6.4.2p2"><small>2</small></a>
11595 The feholdexcept function saves the current floating-point environment in the object
11596 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
11597 (continue on floating-point exceptions) mode, if available, for all floating-point
11598 exceptions.<sup><a href="#note218"><b>218)</b></a></sup>
11601 <p><a name="7.6.4.2p3" href="#7.6.4.2p3"><small>3</small></a>
11602 The feholdexcept function returns zero if and only if non-stop floating-point
11603 exception handling was successfully installed.
11605 <p><b>Footnotes</b>
11606 <p><small><a name="note218" href="#note218">218)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
11607 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
11608 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
11609 function to write routines that hide spurious floating-point exceptions from their callers.
11612 <p><small><a href="#Contents">Contents</a></small>
11613 <h5><a name="7.6.4.3" href="#7.6.4.3">7.6.4.3 The fesetenv function</a></h5>
11615 <p><a name="7.6.4.3p1" href="#7.6.4.3p1"><small>1</small></a>
11617 #include <a href="#7.6"><fenv.h></a>
11618 int fesetenv(const fenv_t *envp);
11620 <p><b>Description</b>
11621 <p><a name="7.6.4.3p2" href="#7.6.4.3p2"><small>2</small></a>
11622 The fesetenv function attempts to establish the floating-point environment represented
11623 by the object pointed to by envp. The argument envp shall point to an object set by a
11624 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
11625 Note that fesetenv merely installs the state of the floating-point status flags
11626 represented through its argument, and does not raise these floating-point exceptions.
11628 <p><a name="7.6.4.3p3" href="#7.6.4.3p3"><small>3</small></a>
11629 The fesetenv function returns zero if the environment was successfully established.
11630 Otherwise, it returns a nonzero value.
11632 <p><small><a href="#Contents">Contents</a></small>
11633 <h5><a name="7.6.4.4" href="#7.6.4.4">7.6.4.4 The feupdateenv function</a></h5>
11635 <p><a name="7.6.4.4p1" href="#7.6.4.4p1"><small>1</small></a>
11637 #include <a href="#7.6"><fenv.h></a>
11638 int feupdateenv(const fenv_t *envp);
11640 <p><b>Description</b>
11641 <p><a name="7.6.4.4p2" href="#7.6.4.4p2"><small>2</small></a>
11642 The feupdateenv function attempts to save the currently raised floating-point
11643 exceptions in its automatic storage, install the floating-point environment represented by
11644 the object pointed to by envp, and then raise the saved floating-point exceptions. The
11645 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
11646 or equal a floating-point environment macro.
11648 <p><a name="7.6.4.4p3" href="#7.6.4.4p3"><small>3</small></a>
11649 The feupdateenv function returns zero if all the actions were successfully carried out.
11650 Otherwise, it returns a nonzero value.
11656 <p><a name="7.6.4.4p4" href="#7.6.4.4p4"><small>4</small></a>
11657 EXAMPLE Hide spurious underflow floating-point exceptions:
11660 #include <a href="#7.6"><fenv.h></a>
11663 #pragma STDC FENV_ACCESS ON
11666 if (feholdexcept(&save_env))
11667 return /* indication of an environmental problem */;
11669 if (/* test spurious underflow */)
11670 if (feclearexcept(FE_UNDERFLOW))
11671 return /* indication of an environmental problem */;
11672 if (feupdateenv(&save_env))
11673 return /* indication of an environmental problem */;
11678 <p><small><a href="#Contents">Contents</a></small>
11679 <h3><a name="7.7" href="#7.7">7.7 Characteristics of floating types <float.h></a></h3>
11680 <p><a name="7.7p1" href="#7.7p1"><small>1</small></a>
11681 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
11682 parameters of the standard floating-point types.
11683 <p><a name="7.7p2" href="#7.7p2"><small>2</small></a>
11684 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11685 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
11688 <p><small><a href="#Contents">Contents</a></small>
11689 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
11690 <p><a name="7.8p1" href="#7.8p1"><small>1</small></a>
11691 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
11692 additional facilities provided by hosted implementations.
11693 <p><a name="7.8p2" href="#7.8p2"><small>2</small></a>
11694 It declares functions for manipulating greatest-width integers and converting numeric
11695 character strings to greatest-width integers, and it declares the type
11699 which is a structure type that is the type of the value returned by the imaxdiv function.
11700 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
11701 specifiers for use with the formatted input/output functions.<sup><a href="#note219"><b>219)</b></a></sup>
11702 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
11703 functions (<a href="#7.21.6">7.21.6</a>), formatted wide character input/output functions (<a href="#7.29.2">7.29.2</a>).
11705 <p><b>Footnotes</b>
11706 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.31.5">7.31.5</a>).
11709 <p><small><a href="#Contents">Contents</a></small>
11710 <h4><a name="7.8.1" href="#7.8.1">7.8.1 Macros for format specifiers</a></h4>
11711 <p><a name="7.8.1p1" href="#7.8.1p1"><small>1</small></a>
11712 Each of the following object-like macros expands to a character string literal containing a
11713 conversion specifier, possibly modified by a length modifier, suitable for use within the
11714 format argument of a formatted input/output function when converting the corresponding
11715 integer type. These macro names have the general form of PRI (character string literals
11716 for the fprintf and fwprintf family) or SCN (character string literals for the
11717 fscanf and fwscanf family),<sup><a href="#note220"><b>220)</b></a></sup> followed by the conversion specifier, followed by a
11718 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
11719 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
11720 format string to print the value of an integer of type int_fast32_t.
11721 <p><a name="7.8.1p2" href="#7.8.1p2"><small>2</small></a>
11722 The fprintf macros for signed integers are:
11724 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
11725 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
11727 <p><a name="7.8.1p3" href="#7.8.1p3"><small>3</small></a>
11728 The fprintf macros for unsigned integers are:
11730 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
11731 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
11732 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
11733 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
11735 <p><a name="7.8.1p4" href="#7.8.1p4"><small>4</small></a>
11736 The fscanf macros for signed integers are:
11742 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
11743 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
11745 <p><a name="7.8.1p5" href="#7.8.1p5"><small>5</small></a>
11746 The fscanf macros for unsigned integers are:
11748 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
11749 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
11750 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
11752 <p><a name="7.8.1p6" href="#7.8.1p6"><small>6</small></a>
11753 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
11754 fprintf macros shall be defined and the corresponding fscanf macros shall be
11755 defined unless the implementation does not have a suitable fscanf length modifier for
11757 <p><a name="7.8.1p7" href="#7.8.1p7"><small>7</small></a>
11760 #include <a href="#7.8"><inttypes.h></a>
11761 #include <a href="#7.29"><wchar.h></a>
11764 uintmax_t i = UINTMAX_MAX; // this type always exists
11765 wprintf(L"The largest integer value is %020"
11772 <p><b>Footnotes</b>
11773 <p><small><a name="note220" href="#note220">220)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
11774 different format specifiers may be required for fprintf and fscanf, even when the type is the
11778 <p><small><a href="#Contents">Contents</a></small>
11779 <h4><a name="7.8.2" href="#7.8.2">7.8.2 Functions for greatest-width integer types</a></h4>
11781 <p><small><a href="#Contents">Contents</a></small>
11782 <h5><a name="7.8.2.1" href="#7.8.2.1">7.8.2.1 The imaxabs function</a></h5>
11784 <p><a name="7.8.2.1p1" href="#7.8.2.1p1"><small>1</small></a>
11786 #include <a href="#7.8"><inttypes.h></a>
11787 intmax_t imaxabs(intmax_t j);
11789 <p><b>Description</b>
11790 <p><a name="7.8.2.1p2" href="#7.8.2.1p2"><small>2</small></a>
11791 The imaxabs function computes the absolute value of an integer j. If the result cannot
11792 be represented, the behavior is undefined.<sup><a href="#note221"><b>221)</b></a></sup>
11794 <p><a name="7.8.2.1p3" href="#7.8.2.1p3"><small>3</small></a>
11795 The imaxabs function returns the absolute value.
11802 <p><b>Footnotes</b>
11803 <p><small><a name="note221" href="#note221">221)</a> The absolute value of the most negative number cannot be represented in two's complement.
11806 <p><small><a href="#Contents">Contents</a></small>
11807 <h5><a name="7.8.2.2" href="#7.8.2.2">7.8.2.2 The imaxdiv function</a></h5>
11809 <p><a name="7.8.2.2p1" href="#7.8.2.2p1"><small>1</small></a>
11811 #include <a href="#7.8"><inttypes.h></a>
11812 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
11814 <p><b>Description</b>
11815 <p><a name="7.8.2.2p2" href="#7.8.2.2p2"><small>2</small></a>
11816 The imaxdiv function computes numer / denom and numer % denom in a single
11819 <p><a name="7.8.2.2p3" href="#7.8.2.2p3"><small>3</small></a>
11820 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
11821 quotient and the remainder. The structure shall contain (in either order) the members
11822 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
11823 either part of the result cannot be represented, the behavior is undefined.
11825 <p><small><a href="#Contents">Contents</a></small>
11826 <h5><a name="7.8.2.3" href="#7.8.2.3">7.8.2.3 The strtoimax and strtoumax functions</a></h5>
11828 <p><a name="7.8.2.3p1" href="#7.8.2.3p1"><small>1</small></a>
11830 #include <a href="#7.8"><inttypes.h></a>
11831 intmax_t strtoimax(const char * restrict nptr,
11832 char ** restrict endptr, int base);
11833 uintmax_t strtoumax(const char * restrict nptr,
11834 char ** restrict endptr, int base);
11836 <p><b>Description</b>
11837 <p><a name="7.8.2.3p2" href="#7.8.2.3p2"><small>2</small></a>
11838 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
11839 strtoul, and strtoull functions, except that the initial portion of the string is
11840 converted to intmax_t and uintmax_t representation, respectively.
11842 <p><a name="7.8.2.3p3" href="#7.8.2.3p3"><small>3</small></a>
11843 The strtoimax and strtoumax functions return the converted value, if any. If no
11844 conversion could be performed, zero is returned. If the correct value is outside the range
11845 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
11846 (according to the return type and sign of the value, if any), and the value of the macro
11847 ERANGE is stored in errno.
11848 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
11849 (<a href="#7.22.1.4">7.22.1.4</a>).
11852 <p><small><a href="#Contents">Contents</a></small>
11853 <h5><a name="7.8.2.4" href="#7.8.2.4">7.8.2.4 The wcstoimax and wcstoumax functions</a></h5>
11855 <p><a name="7.8.2.4p1" href="#7.8.2.4p1"><small>1</small></a>
11857 #include <a href="#7.19"><stddef.h></a> // for wchar_t
11858 #include <a href="#7.8"><inttypes.h></a>
11859 intmax_t wcstoimax(const wchar_t * restrict nptr,
11860 wchar_t ** restrict endptr, int base);
11861 uintmax_t wcstoumax(const wchar_t * restrict nptr,
11862 wchar_t ** restrict endptr, int base);
11864 <p><b>Description</b>
11865 <p><a name="7.8.2.4p2" href="#7.8.2.4p2"><small>2</small></a>
11866 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
11867 wcstoul, and wcstoull functions except that the initial portion of the wide string is
11868 converted to intmax_t and uintmax_t representation, respectively.
11870 <p><a name="7.8.2.4p3" href="#7.8.2.4p3"><small>3</small></a>
11871 The wcstoimax function returns the converted value, if any. If no conversion could be
11872 performed, zero is returned. If the correct value is outside the range of representable
11873 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
11874 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
11876 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
11877 (<a href="#7.29.4.1.2">7.29.4.1.2</a>).
11880 <p><small><a href="#Contents">Contents</a></small>
11881 <h3><a name="7.9" href="#7.9">7.9 Alternative spellings <iso646.h></a></h3>
11882 <p><a name="7.9p1" href="#7.9p1"><small>1</small></a>
11883 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
11884 to the corresponding tokens (on the right):
11900 <p><small><a href="#Contents">Contents</a></small>
11901 <h3><a name="7.10" href="#7.10">7.10 Sizes of integer types <limits.h></a></h3>
11902 <p><a name="7.10p1" href="#7.10p1"><small>1</small></a>
11903 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
11904 parameters of the standard integer types.
11905 <p><a name="7.10p2" href="#7.10p2"><small>2</small></a>
11906 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11907 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
11910 <p><small><a href="#Contents">Contents</a></small>
11911 <h3><a name="7.11" href="#7.11">7.11 Localization <locale.h></a></h3>
11912 <p><a name="7.11p1" href="#7.11p1"><small>1</small></a>
11913 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
11914 <p><a name="7.11p2" href="#7.11p2"><small>2</small></a>
11919 which contains members related to the formatting of numeric values. The structure shall
11920 contain at least the following members, in any order. The semantics of the members and
11921 their normal ranges are explained in <a href="#7.11.2.1">7.11.2.1</a>. In the "C" locale, the members shall have
11922 the values specified in the comments.
11925 char *decimal_point; // "."
11926 char *thousands_sep; // ""
11927 char *grouping; // ""
11928 char *mon_decimal_point; // ""
11929 char *mon_thousands_sep; // ""
11930 char *mon_grouping; // ""
11931 char *positive_sign; // ""
11932 char *negative_sign; // ""
11933 char *currency_symbol; // ""
11934 char frac_digits; // CHAR_MAX
11935 char p_cs_precedes; // CHAR_MAX
11936 char n_cs_precedes; // CHAR_MAX
11937 char p_sep_by_space; // CHAR_MAX
11938 char n_sep_by_space; // CHAR_MAX
11939 char p_sign_posn; // CHAR_MAX
11940 char n_sign_posn; // CHAR_MAX
11941 char *int_curr_symbol; // ""
11942 char int_frac_digits; // CHAR_MAX
11943 char int_p_cs_precedes; // CHAR_MAX
11944 char int_n_cs_precedes; // CHAR_MAX
11945 char int_p_sep_by_space; // CHAR_MAX
11946 char int_n_sep_by_space; // CHAR_MAX
11947 char int_p_sign_posn; // CHAR_MAX
11948 char int_n_sign_posn; // CHAR_MAX
11950 <p><a name="7.11p3" href="#7.11p3"><small>3</small></a>
11951 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
11960 which expand to integer constant expressions with distinct values, suitable for use as the
11961 first argument to the setlocale function.<sup><a href="#note222"><b>222)</b></a></sup> Additional macro definitions, beginning
11962 with the characters LC_ and an uppercase letter,<sup><a href="#note223"><b>223)</b></a></sup> may also be specified by the
11965 <p><b>Footnotes</b>
11966 <p><small><a name="note222" href="#note222">222)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
11968 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.31.6">7.31.6</a>).
11971 <p><small><a href="#Contents">Contents</a></small>
11972 <h4><a name="7.11.1" href="#7.11.1">7.11.1 Locale control</a></h4>
11974 <p><small><a href="#Contents">Contents</a></small>
11975 <h5><a name="7.11.1.1" href="#7.11.1.1">7.11.1.1 The setlocale function</a></h5>
11977 <p><a name="7.11.1.1p1" href="#7.11.1.1p1"><small>1</small></a>
11979 #include <a href="#7.11"><locale.h></a>
11980 char *setlocale(int category, const char *locale);
11982 <p><b>Description</b>
11983 <p><a name="7.11.1.1p2" href="#7.11.1.1p2"><small>2</small></a>
11984 The setlocale function selects the appropriate portion of the program's locale as
11985 specified by the category and locale arguments. The setlocale function may be
11986 used to change or query the program's entire current locale or portions thereof. The value
11987 LC_ALL for category names the program's entire locale; the other values for
11988 category name only a portion of the program's locale. LC_COLLATE affects the
11989 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
11990 the character handling functions<sup><a href="#note224"><b>224)</b></a></sup> and the multibyte and wide character functions.
11991 LC_MONETARY affects the monetary formatting information returned by the
11992 localeconv function. LC_NUMERIC affects the decimal-point character for the
11993 formatted input/output functions and the string conversion functions, as well as the
11994 nonmonetary formatting information returned by the localeconv function. LC_TIME
11995 affects the behavior of the strftime and wcsftime functions.
11996 <p><a name="7.11.1.1p3" href="#7.11.1.1p3"><small>3</small></a>
11997 A value of "C" for locale specifies the minimal environment for C translation; a value
11998 of "" for locale specifies the locale-specific native environment. Other
11999 implementation-defined strings may be passed as the second argument to setlocale.
12002 <p><a name="7.11.1.1p4" href="#7.11.1.1p4"><small>4</small></a>
12003 At program startup, the equivalent of
12005 setlocale(LC_ALL, "C");
12008 <p><a name="7.11.1.1p5" href="#7.11.1.1p5"><small>5</small></a>
12009 A call to the setlocale function may introduce a data race with other calls to the
12010 setlocale function or with calls to functions that are affected by the current locale.
12011 The implementation shall behave as if no library function calls the setlocale function.
12013 <p><a name="7.11.1.1p6" href="#7.11.1.1p6"><small>6</small></a>
12014 If a pointer to a string is given for locale and the selection can be honored, the
12015 setlocale function returns a pointer to the string associated with the specified
12016 category for the new locale. If the selection cannot be honored, the setlocale
12017 function returns a null pointer and the program's locale is not changed.
12018 <p><a name="7.11.1.1p7" href="#7.11.1.1p7"><small>7</small></a>
12019 A null pointer for locale causes the setlocale function to return a pointer to the
12020 string associated with the category for the program's current locale; the program's
12021 locale is not changed.<sup><a href="#note225"><b>225)</b></a></sup>
12022 <p><a name="7.11.1.1p8" href="#7.11.1.1p8"><small>8</small></a>
12023 The pointer to string returned by the setlocale function is such that a subsequent call
12024 with that string value and its associated category will restore that part of the program's
12025 locale. The string pointed to shall not be modified by the program, but may be
12026 overwritten by a subsequent call to the setlocale function.
12027 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
12028 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
12029 (<a href="#7.22.8">7.22.8</a>), numeric conversion functions (<a href="#7.22.1">7.22.1</a>), the strcoll function (<a href="#7.24.4.3">7.24.4.3</a>), the
12030 strftime function (<a href="#7.27.3.5">7.27.3.5</a>), the strxfrm function (<a href="#7.24.4.5">7.24.4.5</a>).
12032 <p><b>Footnotes</b>
12033 <p><small><a name="note224" href="#note224">224)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
12036 <p><small><a name="note225" href="#note225">225)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
12037 locale when category has the value LC_ALL.
12040 <p><small><a href="#Contents">Contents</a></small>
12041 <h4><a name="7.11.2" href="#7.11.2">7.11.2 Numeric formatting convention inquiry</a></h4>
12043 <p><small><a href="#Contents">Contents</a></small>
12044 <h5><a name="7.11.2.1" href="#7.11.2.1">7.11.2.1 The localeconv function</a></h5>
12046 <p><a name="7.11.2.1p1" href="#7.11.2.1p1"><small>1</small></a>
12048 #include <a href="#7.11"><locale.h></a>
12049 struct lconv *localeconv(void);
12051 <p><b>Description</b>
12052 <p><a name="7.11.2.1p2" href="#7.11.2.1p2"><small>2</small></a>
12053 The localeconv function sets the components of an object with type struct lconv
12054 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
12055 according to the rules of the current locale.
12060 <p><a name="7.11.2.1p3" href="#7.11.2.1p3"><small>3</small></a>
12061 The members of the structure with type char * are pointers to strings, any of which
12062 (except decimal_point) can point to "", to indicate that the value is not available in
12063 the current locale or is of zero length. Apart from grouping and mon_grouping, the
12064 strings shall start and end in the initial shift state. The members with type char are
12065 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
12066 available in the current locale. The members include the following:
12067 char *decimal_point
12069 The decimal-point character used to format nonmonetary quantities.
12071 char *thousands_sep
12073 The character used to separate groups of digits before the decimal-point
12074 character in formatted nonmonetary quantities.
12078 A string whose elements indicate the size of each group of digits in
12079 formatted nonmonetary quantities.
12081 char *mon_decimal_point
12083 The decimal-point used to format monetary quantities.
12085 char *mon_thousands_sep
12087 The separator for groups of digits before the decimal-point in formatted
12088 monetary quantities.
12092 A string whose elements indicate the size of each group of digits in
12093 formatted monetary quantities.
12095 char *positive_sign
12097 The string used to indicate a nonnegative-valued formatted monetary
12100 char *negative_sign
12102 The string used to indicate a negative-valued formatted monetary quantity.
12104 char *currency_symbol
12106 The local currency symbol applicable to the current locale.
12110 The number of fractional digits (those after the decimal-point) to be
12111 displayed in a locally formatted monetary quantity.
12116 Set to 1 or 0 if the currency_symbol respectively precedes or
12117 succeeds the value for a nonnegative locally formatted monetary quantity.
12121 Set to 1 or 0 if the currency_symbol respectively precedes or
12122 succeeds the value for a negative locally formatted monetary quantity.
12124 char p_sep_by_space
12126 Set to a value indicating the separation of the currency_symbol, the
12127 sign string, and the value for a nonnegative locally formatted monetary
12130 char n_sep_by_space
12132 Set to a value indicating the separation of the currency_symbol, the
12133 sign string, and the value for a negative locally formatted monetary
12138 Set to a value indicating the positioning of the positive_sign for a
12139 nonnegative locally formatted monetary quantity.
12143 Set to a value indicating the positioning of the negative_sign for a
12144 negative locally formatted monetary quantity.
12146 char *int_curr_symbol
12148 The international currency symbol applicable to the current locale. The
12149 first three characters contain the alphabetic international currency symbol
12150 in accordance with those specified in ISO 4217. The fourth character
12151 (immediately preceding the null character) is the character used to separate
12152 the international currency symbol from the monetary quantity.
12154 char int_frac_digits
12156 The number of fractional digits (those after the decimal-point) to be
12157 displayed in an internationally formatted monetary quantity.
12159 char int_p_cs_precedes
12161 Set to 1 or 0 if the int_curr_symbol respectively precedes or
12162 succeeds the value for a nonnegative internationally formatted monetary
12165 char int_n_cs_precedes
12167 Set to 1 or 0 if the int_curr_symbol respectively precedes or
12168 succeeds the value for a negative internationally formatted monetary
12171 char int_p_sep_by_space
12174 Set to a value indicating the separation of the int_curr_symbol, the
12175 sign string, and the value for a nonnegative internationally formatted
12178 char int_n_sep_by_space
12180 Set to a value indicating the separation of the int_curr_symbol, the
12181 sign string, and the value for a negative internationally formatted monetary
12184 char int_p_sign_posn
12186 Set to a value indicating the positioning of the positive_sign for a
12187 nonnegative internationally formatted monetary quantity.
12189 char int_n_sign_posn
12191 Set to a value indicating the positioning of the negative_sign for a
12192 negative internationally formatted monetary quantity.
12194 <p><a name="7.11.2.1p4" href="#7.11.2.1p4"><small>4</small></a>
12195 The elements of grouping and mon_grouping are interpreted according to the
12197 CHAR_MAX No further grouping is to be performed.
12198 0 The previous element is to be repeatedly used for the remainder of the
12202 other The integer value is the number of digits that compose the current group.
12204 The next element is examined to determine the size of the next group of
12205 digits before the current group.
12207 <p><a name="7.11.2.1p5" href="#7.11.2.1p5"><small>5</small></a>
12208 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
12209 and int_n_sep_by_space are interpreted according to the following:
12210 0 No space separates the currency symbol and value.
12211 1 If the currency symbol and sign string are adjacent, a space separates them from the
12213 value; otherwise, a space separates the currency symbol from the value.
12215 2 If the currency symbol and sign string are adjacent, a space separates them;
12217 otherwise, a space separates the sign string from the value.
12219 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
12220 int_curr_symbol is used instead of a space.
12221 <p><a name="7.11.2.1p6" href="#7.11.2.1p6"><small>6</small></a>
12222 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
12223 int_n_sign_posn are interpreted according to the following:
12224 0 Parentheses surround the quantity and currency symbol.
12225 1 The sign string precedes the quantity and currency symbol.
12226 2 The sign string succeeds the quantity and currency symbol.
12227 3 The sign string immediately precedes the currency symbol.
12228 4 The sign string immediately succeeds the currency symbol.
12230 <p><a name="7.11.2.1p7" href="#7.11.2.1p7"><small>7</small></a>
12231 The implementation shall behave as if no library function calls the localeconv
12234 <p><a name="7.11.2.1p8" href="#7.11.2.1p8"><small>8</small></a>
12235 The localeconv function returns a pointer to the filled-in object. The structure
12236 pointed to by the return value shall not be modified by the program, but may be
12237 overwritten by a subsequent call to the localeconv function. In addition, calls to the
12238 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
12239 overwrite the contents of the structure.
12240 <p><a name="7.11.2.1p9" href="#7.11.2.1p9"><small>9</small></a>
12241 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
12242 monetary quantities.
12244 Local format International format
12247 Country Positive Negative Positive Negative
12249 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
12250 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
12251 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
12252 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
12253 <p><a name="7.11.2.1p10" href="#7.11.2.1p10"><small>10</small></a>
12254 For these four countries, the respective values for the monetary members of the structure returned by
12255 localeconv could be:
12257 Country1 Country2 Country3 Country4
12260 mon_decimal_point "," "" "," "."
12261 mon_thousands_sep "." "." "." ","
12262 mon_grouping "\3" "\3" "\3" "\3"
12263 positive_sign "" "" "" ""
12264 negative_sign "-" "-" "-" "C"
12265 currency_symbol "mk" "L." "\u0192" "SFrs."
12266 frac_digits 2 0 2 2
12267 p_cs_precedes 0 1 1 1
12268 n_cs_precedes 0 1 1 1
12269 p_sep_by_space 1 0 1 0
12270 n_sep_by_space 1 0 2 0
12271 p_sign_posn 1 1 1 1
12272 n_sign_posn 1 1 4 2
12273 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
12274 int_frac_digits 2 0 2 2
12275 int_p_cs_precedes 1 1 1 1
12276 int_n_cs_precedes 1 1 1 1
12277 int_p_sep_by_space 1 1 1 1
12278 int_n_sep_by_space 2 1 2 1
12279 int_p_sign_posn 1 1 1 1
12280 int_n_sign_posn 4 1 4 2
12282 <p><a name="7.11.2.1p11" href="#7.11.2.1p11"><small>11</small></a>
12283 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
12284 affect the formatted value.
12289 p_cs_precedes p_sign_posn 0 1 2
12292 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
12293 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
12294 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
12295 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
12296 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
12301 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
12302 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
12303 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
12304 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
12305 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25
12308 <p><small><a href="#Contents">Contents</a></small>
12309 <h3><a name="7.12" href="#7.12">7.12 Mathematics <math.h></a></h3>
12310 <p><a name="7.12p1" href="#7.12p1"><small>1</small></a>
12311 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
12312 several macros. Most synopses specify a family of functions consisting of a principal
12313 function with one or more double parameters, a double return value, or both; and
12314 other functions with the same name but with f and l suffixes, which are corresponding
12315 functions with float and long double parameters, return values, or both.<sup><a href="#note226"><b>226)</b></a></sup>
12316 Integer arithmetic functions and conversion functions are discussed later.
12317 <p><a name="7.12p2" href="#7.12p2"><small>2</small></a>
12323 are floating types at least as wide as float and double, respectively, and such that
12324 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
12325 float_t and double_t are float and double, respectively; if
12326 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
12327 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
12328 otherwise implementation-defined.<sup><a href="#note227"><b>227)</b></a></sup>
12329 <p><a name="7.12p3" href="#7.12p3"><small>3</small></a>
12334 expands to a positive double constant expression, not necessarily representable as a
12340 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note228"><b>228)</b></a></sup>
12341 <p><a name="7.12p4" href="#7.12p4"><small>4</small></a>
12346 expands to a constant expression of type float representing positive or unsigned
12347 infinity, if available; else to a positive constant of type float that overflows at
12352 translation time.<sup><a href="#note229"><b>229)</b></a></sup>
12353 <p><a name="7.12p5" href="#7.12p5"><small>5</small></a>
12358 is defined if and only if the implementation supports quiet NaNs for the float type. It
12359 expands to a constant expression of type float representing a quiet NaN.
12360 <p><a name="7.12p6" href="#7.12p6"><small>6</small></a>
12361 The number classification macros
12369 represent the mutually exclusive kinds of floating-point values. They expand to integer
12370 constant expressions with distinct values. Additional implementation-defined floating-
12371 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
12372 may also be specified by the implementation.
12373 <p><a name="7.12p7" href="#7.12p7"><small>7</small></a>
12378 is optionally defined. If defined, it indicates that the fma function generally executes
12379 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note230"><b>230)</b></a></sup> The
12385 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
12386 these macros expand to the integer constant 1.
12387 <p><a name="7.12p8" href="#7.12p8"><small>8</small></a>
12393 expand to integer constant expressions whose values are returned by ilogb(x) if x is
12394 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
12395 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
12399 <p><a name="7.12p9" href="#7.12p9"><small>9</small></a>
12405 expand to the integer constants 1 and 2, respectively; the macro
12409 expands to an expression that has type int and the value MATH_ERRNO,
12410 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
12411 constant for the duration of the program. It is unspecified whether
12412 math_errhandling is a macro or an identifier with external linkage. If a macro
12413 definition is suppressed or a program defines an identifier with the name
12414 math_errhandling, the behavior is undefined. If the expression
12415 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
12416 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
12417 <a href="#7.6"><fenv.h></a>.
12419 <p><b>Footnotes</b>
12420 <p><small><a name="note226" href="#note226">226)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
12421 and return values in wider format than the synopsis prototype indicates.
12423 <p><small><a name="note227" href="#note227">227)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
12424 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
12425 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
12427 <p><small><a name="note228" href="#note228">228)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
12428 supports infinities.
12430 <p><small><a name="note229" href="#note229">229)</a> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
12432 <p><small><a name="note230" href="#note230">230)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
12433 directly with a hardware multiply-add instruction. Software implementations are expected to be
12434 substantially slower.
12437 <p><small><a href="#Contents">Contents</a></small>
12438 <h4><a name="7.12.1" href="#7.12.1">7.12.1 Treatment of error conditions</a></h4>
12439 <p><a name="7.12.1p1" href="#7.12.1p1"><small>1</small></a>
12440 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
12441 values of its input arguments, except where stated otherwise. Each function shall execute
12442 as if it were a single operation without raising SIGFPE and without generating any of the
12443 floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect
12444 the result of the function.
12445 <p><a name="7.12.1p2" href="#7.12.1p2"><small>2</small></a>
12446 For all functions, a domain error occurs if an input argument is outside the domain over
12447 which the mathematical function is defined. The description of each function lists any
12448 required domain errors; an implementation may define additional domain errors, provided
12449 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note231"><b>231)</b></a></sup> On a
12450 domain error, the function returns an implementation-defined value; if the integer
12451 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
12452 errno acquires the value EDOM; if the integer expression math_errhandling &
12453 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
12454 <p><a name="7.12.1p3" href="#7.12.1p3"><small>3</small></a>
12455 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
12456 mathematical function has an exact infinite result as the finite input argument(s) are
12457 approached in the limit (for example, log(0.0)). The description of each function lists
12458 any required pole errors; an implementation may define additional pole errors, provided
12459 that such errors are consistent with the mathematical definition of the function. On a pole
12460 error, the function returns an implementation-defined value; if the integer expression
12464 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
12465 acquires the value ERANGE; if the integer expression math_errhandling &
12466 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
12467 <p><a name="7.12.1p4" href="#7.12.1p4"><small>4</small></a>
12468 Likewise, a range error occurs if the mathematical result of the function cannot be
12469 represented in an object of the specified type, due to extreme magnitude.
12470 <p><a name="7.12.1p5" href="#7.12.1p5"><small>5</small></a>
12471 A floating result overflows if the magnitude of the mathematical result is finite but so
12472 large that the mathematical result cannot be represented without extraordinary roundoff
12473 error in an object of the specified type. If a floating result overflows and default rounding
12474 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or
12475 HUGE_VALL according to the return type, with the same sign as the correct value of the
12476 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
12477 the integer expression errno acquires the value ERANGE; if the integer expression
12478 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
12479 point exception is raised.
12480 <p><a name="7.12.1p6" href="#7.12.1p6"><small>6</small></a>
12481 The result underflows if the magnitude of the mathematical result is so small that the
12482 mathematical result cannot be represented, without extraordinary roundoff error, in an
12483 object of the specified type.<sup><a href="#note232"><b>232)</b></a></sup> If the result underflows, the function returns an
12484 implementation-defined value whose magnitude is no greater than the smallest
12485 normalized positive number in the specified type; if the integer expression
12486 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
12487 value ERANGE is implementation-defined; if the integer expression
12488 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
12489 floating-point exception is raised is implementation-defined.
12490 <p><a name="7.12.1p7" href="#7.12.1p7"><small>7</small></a>
12491 If a domain, pole, or range error occurs and the integer expression
12492 math_errhandling & MATH_ERRNO is zero,<sup><a href="#note233"><b>233)</b></a></sup> then errno shall either be set to
12493 the value corresponding to the error or left unmodified. If no such error occurs, errno
12494 shall be left unmodified regardless of the setting of math_errhandling.
12501 <p><b>Footnotes</b>
12502 <p><small><a name="note231" href="#note231">231)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
12503 error if the mathematical domain of the function does not include the infinity.
12505 <p><small><a name="note232" href="#note232">232)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
12506 also ''flush-to-zero'' underflow.
12508 <p><small><a name="note233" href="#note233">233)</a> Math errors are being indicated by the floating-point exception flags rather than by errno.
12511 <p><small><a href="#Contents">Contents</a></small>
12512 <h4><a name="7.12.2" href="#7.12.2">7.12.2 The FP_CONTRACT pragma</a></h4>
12514 <p><a name="7.12.2p1" href="#7.12.2p1"><small>1</small></a>
12516 #include <a href="#7.12"><math.h></a>
12517 #pragma STDC FP_CONTRACT on-off-switch
12519 <p><b>Description</b>
12520 <p><a name="7.12.2p2" href="#7.12.2p2"><small>2</small></a>
12521 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
12522 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
12523 either outside external declarations or preceding all explicit declarations and statements
12524 inside a compound statement. When outside external declarations, the pragma takes
12525 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
12526 the end of the translation unit. When inside a compound statement, the pragma takes
12527 effect from its occurrence until another FP_CONTRACT pragma is encountered
12528 (including within a nested compound statement), or until the end of the compound
12529 statement; at the end of a compound statement the state for the pragma is restored to its
12530 condition just before the compound statement. If this pragma is used in any other
12531 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
12532 implementation-defined.
12534 <p><small><a href="#Contents">Contents</a></small>
12535 <h4><a name="7.12.3" href="#7.12.3">7.12.3 Classification macros</a></h4>
12536 <p><a name="7.12.3p1" href="#7.12.3p1"><small>1</small></a>
12537 In the synopses in this subclause, real-floating indicates that the argument shall be an
12538 expression of real floating type.
12540 <p><small><a href="#Contents">Contents</a></small>
12541 <h5><a name="7.12.3.1" href="#7.12.3.1">7.12.3.1 The fpclassify macro</a></h5>
12543 <p><a name="7.12.3.1p1" href="#7.12.3.1p1"><small>1</small></a>
12545 #include <a href="#7.12"><math.h></a>
12546 int fpclassify(real-floating x);
12548 <p><b>Description</b>
12549 <p><a name="7.12.3.1p2" href="#7.12.3.1p2"><small>2</small></a>
12550 The fpclassify macro classifies its argument value as NaN, infinite, normal,
12551 subnormal, zero, or into another implementation-defined category. First, an argument
12552 represented in a format wider than its semantic type is converted to its semantic type.
12553 Then classification is based on the type of the argument.<sup><a href="#note234"><b>234)</b></a></sup>
12555 <p><a name="7.12.3.1p3" href="#7.12.3.1p3"><small>3</small></a>
12556 The fpclassify macro returns the value of the number classification macro
12557 appropriate to the value of its argument.
12562 <p><b>Footnotes</b>
12563 <p><small><a name="note234" href="#note234">234)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
12564 know the type that classification is based on. For example, a normal long double value might
12565 become subnormal when converted to double, and zero when converted to float.
12568 <p><small><a href="#Contents">Contents</a></small>
12569 <h5><a name="7.12.3.2" href="#7.12.3.2">7.12.3.2 The isfinite macro</a></h5>
12571 <p><a name="7.12.3.2p1" href="#7.12.3.2p1"><small>1</small></a>
12573 #include <a href="#7.12"><math.h></a>
12574 int isfinite(real-floating x);
12576 <p><b>Description</b>
12577 <p><a name="7.12.3.2p2" href="#7.12.3.2p2"><small>2</small></a>
12578 The isfinite macro determines whether its argument has a finite value (zero,
12579 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
12580 format wider than its semantic type is converted to its semantic type. Then determination
12581 is based on the type of the argument.
12583 <p><a name="7.12.3.2p3" href="#7.12.3.2p3"><small>3</small></a>
12584 The isfinite macro returns a nonzero value if and only if its argument has a finite
12587 <p><small><a href="#Contents">Contents</a></small>
12588 <h5><a name="7.12.3.3" href="#7.12.3.3">7.12.3.3 The isinf macro</a></h5>
12590 <p><a name="7.12.3.3p1" href="#7.12.3.3p1"><small>1</small></a>
12592 #include <a href="#7.12"><math.h></a>
12593 int isinf(real-floating x);
12595 <p><b>Description</b>
12596 <p><a name="7.12.3.3p2" href="#7.12.3.3p2"><small>2</small></a>
12597 The isinf macro determines whether its argument value is an infinity (positive or
12598 negative). First, an argument represented in a format wider than its semantic type is
12599 converted to its semantic type. Then determination is based on the type of the argument.
12601 <p><a name="7.12.3.3p3" href="#7.12.3.3p3"><small>3</small></a>
12602 The isinf macro returns a nonzero value if and only if its argument has an infinite
12605 <p><small><a href="#Contents">Contents</a></small>
12606 <h5><a name="7.12.3.4" href="#7.12.3.4">7.12.3.4 The isnan macro</a></h5>
12608 <p><a name="7.12.3.4p1" href="#7.12.3.4p1"><small>1</small></a>
12610 #include <a href="#7.12"><math.h></a>
12611 int isnan(real-floating x);
12613 <p><b>Description</b>
12614 <p><a name="7.12.3.4p2" href="#7.12.3.4p2"><small>2</small></a>
12615 The isnan macro determines whether its argument value is a NaN. First, an argument
12616 represented in a format wider than its semantic type is converted to its semantic type.
12617 Then determination is based on the type of the argument.<sup><a href="#note235"><b>235)</b></a></sup>
12622 <p><a name="7.12.3.4p3" href="#7.12.3.4p3"><small>3</small></a>
12623 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
12625 <p><b>Footnotes</b>
12626 <p><small><a name="note235" href="#note235">235)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
12627 NaNs in the evaluation type but not in the semantic type.
12630 <p><small><a href="#Contents">Contents</a></small>
12631 <h5><a name="7.12.3.5" href="#7.12.3.5">7.12.3.5 The isnormal macro</a></h5>
12633 <p><a name="7.12.3.5p1" href="#7.12.3.5p1"><small>1</small></a>
12635 #include <a href="#7.12"><math.h></a>
12636 int isnormal(real-floating x);
12638 <p><b>Description</b>
12639 <p><a name="7.12.3.5p2" href="#7.12.3.5p2"><small>2</small></a>
12640 The isnormal macro determines whether its argument value is normal (neither zero,
12641 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
12642 semantic type is converted to its semantic type. Then determination is based on the type
12645 <p><a name="7.12.3.5p3" href="#7.12.3.5p3"><small>3</small></a>
12646 The isnormal macro returns a nonzero value if and only if its argument has a normal
12649 <p><small><a href="#Contents">Contents</a></small>
12650 <h5><a name="7.12.3.6" href="#7.12.3.6">7.12.3.6 The signbit macro</a></h5>
12652 <p><a name="7.12.3.6p1" href="#7.12.3.6p1"><small>1</small></a>
12654 #include <a href="#7.12"><math.h></a>
12655 int signbit(real-floating x);
12657 <p><b>Description</b>
12658 <p><a name="7.12.3.6p2" href="#7.12.3.6p2"><small>2</small></a>
12659 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note236"><b>236)</b></a></sup>
12661 <p><a name="7.12.3.6p3" href="#7.12.3.6p3"><small>3</small></a>
12662 The signbit macro returns a nonzero value if and only if the sign of its argument value
12670 <p><b>Footnotes</b>
12671 <p><small><a name="note236" href="#note236">236)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
12672 unsigned, it is treated as positive.
12675 <p><small><a href="#Contents">Contents</a></small>
12676 <h4><a name="7.12.4" href="#7.12.4">7.12.4 Trigonometric functions</a></h4>
12678 <p><small><a href="#Contents">Contents</a></small>
12679 <h5><a name="7.12.4.1" href="#7.12.4.1">7.12.4.1 The acos functions</a></h5>
12681 <p><a name="7.12.4.1p1" href="#7.12.4.1p1"><small>1</small></a>
12683 #include <a href="#7.12"><math.h></a>
12684 double acos(double x);
12685 float acosf(float x);
12686 long double acosl(long double x);
12688 <p><b>Description</b>
12689 <p><a name="7.12.4.1p2" href="#7.12.4.1p2"><small>2</small></a>
12690 The acos functions compute the principal value of the arc cosine of x. A domain error
12691 occurs for arguments not in the interval [-1, +1].
12693 <p><a name="7.12.4.1p3" href="#7.12.4.1p3"><small>3</small></a>
12694 The acos functions return arccos x in the interval [0, pi ] radians.
12696 <p><small><a href="#Contents">Contents</a></small>
12697 <h5><a name="7.12.4.2" href="#7.12.4.2">7.12.4.2 The asin functions</a></h5>
12699 <p><a name="7.12.4.2p1" href="#7.12.4.2p1"><small>1</small></a>
12701 #include <a href="#7.12"><math.h></a>
12702 double asin(double x);
12703 float asinf(float x);
12704 long double asinl(long double x);
12706 <p><b>Description</b>
12707 <p><a name="7.12.4.2p2" href="#7.12.4.2p2"><small>2</small></a>
12708 The asin functions compute the principal value of the arc sine of x. A domain error
12709 occurs for arguments not in the interval [-1, +1].
12711 <p><a name="7.12.4.2p3" href="#7.12.4.2p3"><small>3</small></a>
12712 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
12714 <p><small><a href="#Contents">Contents</a></small>
12715 <h5><a name="7.12.4.3" href="#7.12.4.3">7.12.4.3 The atan functions</a></h5>
12717 <p><a name="7.12.4.3p1" href="#7.12.4.3p1"><small>1</small></a>
12719 #include <a href="#7.12"><math.h></a>
12720 double atan(double x);
12721 float atanf(float x);
12722 long double atanl(long double x);
12724 <p><b>Description</b>
12725 <p><a name="7.12.4.3p2" href="#7.12.4.3p2"><small>2</small></a>
12726 The atan functions compute the principal value of the arc tangent of x.
12729 <p><a name="7.12.4.3p3" href="#7.12.4.3p3"><small>3</small></a>
12730 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
12732 <p><small><a href="#Contents">Contents</a></small>
12733 <h5><a name="7.12.4.4" href="#7.12.4.4">7.12.4.4 The atan2 functions</a></h5>
12735 <p><a name="7.12.4.4p1" href="#7.12.4.4p1"><small>1</small></a>
12737 #include <a href="#7.12"><math.h></a>
12738 double atan2(double y, double x);
12739 float atan2f(float y, float x);
12740 long double atan2l(long double y, long double x);
12742 <p><b>Description</b>
12743 <p><a name="7.12.4.4p2" href="#7.12.4.4p2"><small>2</small></a>
12744 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
12745 arguments to determine the quadrant of the return value. A domain error may occur if
12746 both arguments are zero.
12748 <p><a name="7.12.4.4p3" href="#7.12.4.4p3"><small>3</small></a>
12749 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
12751 <p><small><a href="#Contents">Contents</a></small>
12752 <h5><a name="7.12.4.5" href="#7.12.4.5">7.12.4.5 The cos functions</a></h5>
12754 <p><a name="7.12.4.5p1" href="#7.12.4.5p1"><small>1</small></a>
12756 #include <a href="#7.12"><math.h></a>
12757 double cos(double x);
12758 float cosf(float x);
12759 long double cosl(long double x);
12761 <p><b>Description</b>
12762 <p><a name="7.12.4.5p2" href="#7.12.4.5p2"><small>2</small></a>
12763 The cos functions compute the cosine of x (measured in radians).
12765 <p><a name="7.12.4.5p3" href="#7.12.4.5p3"><small>3</small></a>
12766 The cos functions return cos x.
12768 <p><small><a href="#Contents">Contents</a></small>
12769 <h5><a name="7.12.4.6" href="#7.12.4.6">7.12.4.6 The sin functions</a></h5>
12771 <p><a name="7.12.4.6p1" href="#7.12.4.6p1"><small>1</small></a>
12773 #include <a href="#7.12"><math.h></a>
12774 double sin(double x);
12775 float sinf(float x);
12776 long double sinl(long double x);
12778 <p><b>Description</b>
12779 <p><a name="7.12.4.6p2" href="#7.12.4.6p2"><small>2</small></a>
12780 The sin functions compute the sine of x (measured in radians).
12783 <p><a name="7.12.4.6p3" href="#7.12.4.6p3"><small>3</small></a>
12784 The sin functions return sin x.
12786 <p><small><a href="#Contents">Contents</a></small>
12787 <h5><a name="7.12.4.7" href="#7.12.4.7">7.12.4.7 The tan functions</a></h5>
12789 <p><a name="7.12.4.7p1" href="#7.12.4.7p1"><small>1</small></a>
12791 #include <a href="#7.12"><math.h></a>
12792 double tan(double x);
12793 float tanf(float x);
12794 long double tanl(long double x);
12796 <p><b>Description</b>
12797 <p><a name="7.12.4.7p2" href="#7.12.4.7p2"><small>2</small></a>
12798 The tan functions return the tangent of x (measured in radians).
12800 <p><a name="7.12.4.7p3" href="#7.12.4.7p3"><small>3</small></a>
12801 The tan functions return tan x.
12803 <p><small><a href="#Contents">Contents</a></small>
12804 <h4><a name="7.12.5" href="#7.12.5">7.12.5 Hyperbolic functions</a></h4>
12806 <p><small><a href="#Contents">Contents</a></small>
12807 <h5><a name="7.12.5.1" href="#7.12.5.1">7.12.5.1 The acosh functions</a></h5>
12809 <p><a name="7.12.5.1p1" href="#7.12.5.1p1"><small>1</small></a>
12811 #include <a href="#7.12"><math.h></a>
12812 double acosh(double x);
12813 float acoshf(float x);
12814 long double acoshl(long double x);
12816 <p><b>Description</b>
12817 <p><a name="7.12.5.1p2" href="#7.12.5.1p2"><small>2</small></a>
12818 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
12819 error occurs for arguments less than 1.
12821 <p><a name="7.12.5.1p3" href="#7.12.5.1p3"><small>3</small></a>
12822 The acosh functions return arcosh x in the interval [0, +(inf)].
12824 <p><small><a href="#Contents">Contents</a></small>
12825 <h5><a name="7.12.5.2" href="#7.12.5.2">7.12.5.2 The asinh functions</a></h5>
12827 <p><a name="7.12.5.2p1" href="#7.12.5.2p1"><small>1</small></a>
12829 #include <a href="#7.12"><math.h></a>
12830 double asinh(double x);
12831 float asinhf(float x);
12832 long double asinhl(long double x);
12834 <p><b>Description</b>
12835 <p><a name="7.12.5.2p2" href="#7.12.5.2p2"><small>2</small></a>
12836 The asinh functions compute the arc hyperbolic sine of x.
12839 <p><a name="7.12.5.2p3" href="#7.12.5.2p3"><small>3</small></a>
12840 The asinh functions return arsinh x.
12842 <p><small><a href="#Contents">Contents</a></small>
12843 <h5><a name="7.12.5.3" href="#7.12.5.3">7.12.5.3 The atanh functions</a></h5>
12845 <p><a name="7.12.5.3p1" href="#7.12.5.3p1"><small>1</small></a>
12847 #include <a href="#7.12"><math.h></a>
12848 double atanh(double x);
12849 float atanhf(float x);
12850 long double atanhl(long double x);
12852 <p><b>Description</b>
12853 <p><a name="7.12.5.3p2" href="#7.12.5.3p2"><small>2</small></a>
12854 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
12855 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
12858 <p><a name="7.12.5.3p3" href="#7.12.5.3p3"><small>3</small></a>
12859 The atanh functions return artanh x.
12861 <p><small><a href="#Contents">Contents</a></small>
12862 <h5><a name="7.12.5.4" href="#7.12.5.4">7.12.5.4 The cosh functions</a></h5>
12864 <p><a name="7.12.5.4p1" href="#7.12.5.4p1"><small>1</small></a>
12866 #include <a href="#7.12"><math.h></a>
12867 double cosh(double x);
12868 float coshf(float x);
12869 long double coshl(long double x);
12871 <p><b>Description</b>
12872 <p><a name="7.12.5.4p2" href="#7.12.5.4p2"><small>2</small></a>
12873 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
12874 magnitude of x is too large.
12876 <p><a name="7.12.5.4p3" href="#7.12.5.4p3"><small>3</small></a>
12877 The cosh functions return cosh x.
12879 <p><small><a href="#Contents">Contents</a></small>
12880 <h5><a name="7.12.5.5" href="#7.12.5.5">7.12.5.5 The sinh functions</a></h5>
12882 <p><a name="7.12.5.5p1" href="#7.12.5.5p1"><small>1</small></a>
12884 #include <a href="#7.12"><math.h></a>
12885 double sinh(double x);
12886 float sinhf(float x);
12887 long double sinhl(long double x);
12889 <p><b>Description</b>
12890 <p><a name="7.12.5.5p2" href="#7.12.5.5p2"><small>2</small></a>
12891 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
12892 magnitude of x is too large.
12895 <p><a name="7.12.5.5p3" href="#7.12.5.5p3"><small>3</small></a>
12896 The sinh functions return sinh x.
12898 <p><small><a href="#Contents">Contents</a></small>
12899 <h5><a name="7.12.5.6" href="#7.12.5.6">7.12.5.6 The tanh functions</a></h5>
12901 <p><a name="7.12.5.6p1" href="#7.12.5.6p1"><small>1</small></a>
12903 #include <a href="#7.12"><math.h></a>
12904 double tanh(double x);
12905 float tanhf(float x);
12906 long double tanhl(long double x);
12908 <p><b>Description</b>
12909 <p><a name="7.12.5.6p2" href="#7.12.5.6p2"><small>2</small></a>
12910 The tanh functions compute the hyperbolic tangent of x.
12912 <p><a name="7.12.5.6p3" href="#7.12.5.6p3"><small>3</small></a>
12913 The tanh functions return tanh x.
12915 <p><small><a href="#Contents">Contents</a></small>
12916 <h4><a name="7.12.6" href="#7.12.6">7.12.6 Exponential and logarithmic functions</a></h4>
12918 <p><small><a href="#Contents">Contents</a></small>
12919 <h5><a name="7.12.6.1" href="#7.12.6.1">7.12.6.1 The exp functions</a></h5>
12921 <p><a name="7.12.6.1p1" href="#7.12.6.1p1"><small>1</small></a>
12923 #include <a href="#7.12"><math.h></a>
12924 double exp(double x);
12925 float expf(float x);
12926 long double expl(long double x);
12928 <p><b>Description</b>
12929 <p><a name="7.12.6.1p2" href="#7.12.6.1p2"><small>2</small></a>
12930 The exp functions compute the base-e exponential of x. A range error occurs if the
12931 magnitude of x is too large.
12933 <p><a name="7.12.6.1p3" href="#7.12.6.1p3"><small>3</small></a>
12934 The exp functions return ex .
12936 <p><small><a href="#Contents">Contents</a></small>
12937 <h5><a name="7.12.6.2" href="#7.12.6.2">7.12.6.2 The exp2 functions</a></h5>
12939 <p><a name="7.12.6.2p1" href="#7.12.6.2p1"><small>1</small></a>
12941 #include <a href="#7.12"><math.h></a>
12942 double exp2(double x);
12943 float exp2f(float x);
12944 long double exp2l(long double x);
12946 <p><b>Description</b>
12947 <p><a name="7.12.6.2p2" href="#7.12.6.2p2"><small>2</small></a>
12948 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
12949 magnitude of x is too large.
12952 <p><a name="7.12.6.2p3" href="#7.12.6.2p3"><small>3</small></a>
12953 The exp2 functions return 2x .
12955 <p><small><a href="#Contents">Contents</a></small>
12956 <h5><a name="7.12.6.3" href="#7.12.6.3">7.12.6.3 The expm1 functions</a></h5>
12958 <p><a name="7.12.6.3p1" href="#7.12.6.3p1"><small>1</small></a>
12960 #include <a href="#7.12"><math.h></a>
12961 double expm1(double x);
12962 float expm1f(float x);
12963 long double expm1l(long double x);
12965 <p><b>Description</b>
12966 <p><a name="7.12.6.3p2" href="#7.12.6.3p2"><small>2</small></a>
12967 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
12968 error occurs if x is too large.<sup><a href="#note237"><b>237)</b></a></sup>
12970 <p><a name="7.12.6.3p3" href="#7.12.6.3p3"><small>3</small></a>
12971 The expm1 functions return ex - 1.
12973 <p><b>Footnotes</b>
12974 <p><small><a name="note237" href="#note237">237)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
12977 <p><small><a href="#Contents">Contents</a></small>
12978 <h5><a name="7.12.6.4" href="#7.12.6.4">7.12.6.4 The frexp functions</a></h5>
12980 <p><a name="7.12.6.4p1" href="#7.12.6.4p1"><small>1</small></a>
12982 #include <a href="#7.12"><math.h></a>
12983 double frexp(double value, int *exp);
12984 float frexpf(float value, int *exp);
12985 long double frexpl(long double value, int *exp);
12987 <p><b>Description</b>
12988 <p><a name="7.12.6.4p2" href="#7.12.6.4p2"><small>2</small></a>
12989 The frexp functions break a floating-point number into a normalized fraction and an
12990 integral power of 2. They store the integer in the int object pointed to by exp.
12992 <p><a name="7.12.6.4p3" href="#7.12.6.4p3"><small>3</small></a>
12993 If value is not a floating-point number or if the integral power of 2 is outside the range
12994 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
12995 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
12996 If value is zero, both parts of the result are zero.
13003 <p><small><a href="#Contents">Contents</a></small>
13004 <h5><a name="7.12.6.5" href="#7.12.6.5">7.12.6.5 The ilogb functions</a></h5>
13006 <p><a name="7.12.6.5p1" href="#7.12.6.5p1"><small>1</small></a>
13008 #include <a href="#7.12"><math.h></a>
13009 int ilogb(double x);
13010 int ilogbf(float x);
13011 int ilogbl(long double x);
13013 <p><b>Description</b>
13014 <p><a name="7.12.6.5p2" href="#7.12.6.5p2"><small>2</small></a>
13015 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
13016 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
13017 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
13018 the corresponding logb function and casting the returned value to type int. A domain
13019 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
13020 the range of the return type, the numeric result is unspecified.
13022 <p><a name="7.12.6.5p3" href="#7.12.6.5p3"><small>3</small></a>
13023 The ilogb functions return the exponent of x as a signed int value.
13024 <p><b> Forward references</b>: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
13026 <p><small><a href="#Contents">Contents</a></small>
13027 <h5><a name="7.12.6.6" href="#7.12.6.6">7.12.6.6 The ldexp functions</a></h5>
13029 <p><a name="7.12.6.6p1" href="#7.12.6.6p1"><small>1</small></a>
13031 #include <a href="#7.12"><math.h></a>
13032 double ldexp(double x, int exp);
13033 float ldexpf(float x, int exp);
13034 long double ldexpl(long double x, int exp);
13036 <p><b>Description</b>
13037 <p><a name="7.12.6.6p2" href="#7.12.6.6p2"><small>2</small></a>
13038 The ldexp functions multiply a floating-point number by an integral power of 2. A
13039 range error may occur.
13041 <p><a name="7.12.6.6p3" href="#7.12.6.6p3"><small>3</small></a>
13042 The ldexp functions return x x 2exp .
13044 <p><small><a href="#Contents">Contents</a></small>
13045 <h5><a name="7.12.6.7" href="#7.12.6.7">7.12.6.7 The log functions</a></h5>
13047 <p><a name="7.12.6.7p1" href="#7.12.6.7p1"><small>1</small></a>
13050 #include <a href="#7.12"><math.h></a>
13051 double log(double x);
13052 float logf(float x);
13053 long double logl(long double x);
13055 <p><b>Description</b>
13056 <p><a name="7.12.6.7p2" href="#7.12.6.7p2"><small>2</small></a>
13057 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
13058 the argument is negative. A pole error may occur if the argument is zero.
13060 <p><a name="7.12.6.7p3" href="#7.12.6.7p3"><small>3</small></a>
13061 The log functions return loge x.
13063 <p><small><a href="#Contents">Contents</a></small>
13064 <h5><a name="7.12.6.8" href="#7.12.6.8">7.12.6.8 The log10 functions</a></h5>
13066 <p><a name="7.12.6.8p1" href="#7.12.6.8p1"><small>1</small></a>
13068 #include <a href="#7.12"><math.h></a>
13069 double log10(double x);
13070 float log10f(float x);
13071 long double log10l(long double x);
13073 <p><b>Description</b>
13074 <p><a name="7.12.6.8p2" href="#7.12.6.8p2"><small>2</small></a>
13075 The log10 functions compute the base-10 (common) logarithm of x. A domain error
13076 occurs if the argument is negative. A pole error may occur if the argument is zero.
13078 <p><a name="7.12.6.8p3" href="#7.12.6.8p3"><small>3</small></a>
13079 The log10 functions return log10 x.
13081 <p><small><a href="#Contents">Contents</a></small>
13082 <h5><a name="7.12.6.9" href="#7.12.6.9">7.12.6.9 The log1p functions</a></h5>
13084 <p><a name="7.12.6.9p1" href="#7.12.6.9p1"><small>1</small></a>
13086 #include <a href="#7.12"><math.h></a>
13087 double log1p(double x);
13088 float log1pf(float x);
13089 long double log1pl(long double x);
13091 <p><b>Description</b>
13092 <p><a name="7.12.6.9p2" href="#7.12.6.9p2"><small>2</small></a>
13093 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note238"><b>238)</b></a></sup>
13094 A domain error occurs if the argument is less than -1. A pole error may occur if the
13095 argument equals -1.
13097 <p><a name="7.12.6.9p3" href="#7.12.6.9p3"><small>3</small></a>
13098 The log1p functions return loge (1 + x).
13105 <p><b>Footnotes</b>
13106 <p><small><a name="note238" href="#note238">238)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
13109 <p><small><a href="#Contents">Contents</a></small>
13110 <h5><a name="7.12.6.10" href="#7.12.6.10">7.12.6.10 The log2 functions</a></h5>
13112 <p><a name="7.12.6.10p1" href="#7.12.6.10p1"><small>1</small></a>
13114 #include <a href="#7.12"><math.h></a>
13115 double log2(double x);
13116 float log2f(float x);
13117 long double log2l(long double x);
13119 <p><b>Description</b>
13120 <p><a name="7.12.6.10p2" href="#7.12.6.10p2"><small>2</small></a>
13121 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
13122 argument is less than zero. A pole error may occur if the argument is zero.
13124 <p><a name="7.12.6.10p3" href="#7.12.6.10p3"><small>3</small></a>
13125 The log2 functions return log2 x.
13127 <p><small><a href="#Contents">Contents</a></small>
13128 <h5><a name="7.12.6.11" href="#7.12.6.11">7.12.6.11 The logb functions</a></h5>
13130 <p><a name="7.12.6.11p1" href="#7.12.6.11p1"><small>1</small></a>
13132 #include <a href="#7.12"><math.h></a>
13133 double logb(double x);
13134 float logbf(float x);
13135 long double logbl(long double x);
13137 <p><b>Description</b>
13138 <p><a name="7.12.6.11p2" href="#7.12.6.11p2"><small>2</small></a>
13139 The logb functions extract the exponent of x, as a signed integer value in floating-point
13140 format. If x is subnormal it is treated as though it were normalized; thus, for positive
13143 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
13145 A domain error or pole error may occur if the argument is zero.
13147 <p><a name="7.12.6.11p3" href="#7.12.6.11p3"><small>3</small></a>
13148 The logb functions return the signed exponent of x.
13150 <p><small><a href="#Contents">Contents</a></small>
13151 <h5><a name="7.12.6.12" href="#7.12.6.12">7.12.6.12 The modf functions</a></h5>
13153 <p><a name="7.12.6.12p1" href="#7.12.6.12p1"><small>1</small></a>
13155 #include <a href="#7.12"><math.h></a>
13156 double modf(double value, double *iptr);
13157 float modff(float value, float *iptr);
13158 long double modfl(long double value, long double *iptr);
13160 <p><b>Description</b>
13161 <p><a name="7.12.6.12p2" href="#7.12.6.12p2"><small>2</small></a>
13162 The modf functions break the argument value into integral and fractional parts, each of
13163 which has the same type and sign as the argument. They store the integral part (in
13165 floating-point format) in the object pointed to by iptr.
13167 <p><a name="7.12.6.12p3" href="#7.12.6.12p3"><small>3</small></a>
13168 The modf functions return the signed fractional part of value.
13170 <p><small><a href="#Contents">Contents</a></small>
13171 <h5><a name="7.12.6.13" href="#7.12.6.13">7.12.6.13 The scalbn and scalbln functions</a></h5>
13173 <p><a name="7.12.6.13p1" href="#7.12.6.13p1"><small>1</small></a>
13175 #include <a href="#7.12"><math.h></a>
13176 double scalbn(double x, int n);
13177 float scalbnf(float x, int n);
13178 long double scalbnl(long double x, int n);
13179 double scalbln(double x, long int n);
13180 float scalblnf(float x, long int n);
13181 long double scalblnl(long double x, long int n);
13183 <p><b>Description</b>
13184 <p><a name="7.12.6.13p2" href="#7.12.6.13p2"><small>2</small></a>
13185 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
13186 normally by computing FLT_RADIXn explicitly. A range error may occur.
13188 <p><a name="7.12.6.13p3" href="#7.12.6.13p3"><small>3</small></a>
13189 The scalbn and scalbln functions return x x FLT_RADIXn .
13191 <p><small><a href="#Contents">Contents</a></small>
13192 <h4><a name="7.12.7" href="#7.12.7">7.12.7 Power and absolute-value functions</a></h4>
13194 <p><small><a href="#Contents">Contents</a></small>
13195 <h5><a name="7.12.7.1" href="#7.12.7.1">7.12.7.1 The cbrt functions</a></h5>
13197 <p><a name="7.12.7.1p1" href="#7.12.7.1p1"><small>1</small></a>
13199 #include <a href="#7.12"><math.h></a>
13200 double cbrt(double x);
13201 float cbrtf(float x);
13202 long double cbrtl(long double x);
13204 <p><b>Description</b>
13205 <p><a name="7.12.7.1p2" href="#7.12.7.1p2"><small>2</small></a>
13206 The cbrt functions compute the real cube root of x.
13208 <p><a name="7.12.7.1p3" href="#7.12.7.1p3"><small>3</small></a>
13209 The cbrt functions return x1/3 .
13212 <p><small><a href="#Contents">Contents</a></small>
13213 <h5><a name="7.12.7.2" href="#7.12.7.2">7.12.7.2 The fabs functions</a></h5>
13215 <p><a name="7.12.7.2p1" href="#7.12.7.2p1"><small>1</small></a>
13217 #include <a href="#7.12"><math.h></a>
13218 double fabs(double x);
13219 float fabsf(float x);
13220 long double fabsl(long double x);
13222 <p><b>Description</b>
13223 <p><a name="7.12.7.2p2" href="#7.12.7.2p2"><small>2</small></a>
13224 The fabs functions compute the absolute value of a floating-point number x.
13226 <p><a name="7.12.7.2p3" href="#7.12.7.2p3"><small>3</small></a>
13227 The fabs functions return | x |.
13229 <p><small><a href="#Contents">Contents</a></small>
13230 <h5><a name="7.12.7.3" href="#7.12.7.3">7.12.7.3 The hypot functions</a></h5>
13232 <p><a name="7.12.7.3p1" href="#7.12.7.3p1"><small>1</small></a>
13234 #include <a href="#7.12"><math.h></a>
13235 double hypot(double x, double y);
13236 float hypotf(float x, float y);
13237 long double hypotl(long double x, long double y);
13239 <p><b>Description</b>
13240 <p><a name="7.12.7.3p2" href="#7.12.7.3p2"><small>2</small></a>
13241 The hypot functions compute the square root of the sum of the squares of x and y,
13242 without undue overflow or underflow. A range error may occur.
13243 <p><a name="7.12.7.3p3" href="#7.12.7.3p3"><small>3</small></a>
13245 <p><a name="7.12.7.3p4" href="#7.12.7.3p4"><small>4</small></a>
13246 The hypot functions return (sqrt)x2 + y2 .
13252 <p><small><a href="#Contents">Contents</a></small>
13253 <h5><a name="7.12.7.4" href="#7.12.7.4">7.12.7.4 The pow functions</a></h5>
13255 <p><a name="7.12.7.4p1" href="#7.12.7.4p1"><small>1</small></a>
13257 #include <a href="#7.12"><math.h></a>
13258 double pow(double x, double y);
13259 float powf(float x, float y);
13260 long double powl(long double x, long double y);
13262 <p><b>Description</b>
13263 <p><a name="7.12.7.4p2" href="#7.12.7.4p2"><small>2</small></a>
13264 The pow functions compute x raised to the power y. A domain error occurs if x is finite
13265 and negative and y is finite and not an integer value. A range error may occur. A domain
13266 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
13267 zero and y is less than zero.
13270 <p><a name="7.12.7.4p3" href="#7.12.7.4p3"><small>3</small></a>
13271 The pow functions return xy .
13273 <p><small><a href="#Contents">Contents</a></small>
13274 <h5><a name="7.12.7.5" href="#7.12.7.5">7.12.7.5 The sqrt functions</a></h5>
13276 <p><a name="7.12.7.5p1" href="#7.12.7.5p1"><small>1</small></a>
13278 #include <a href="#7.12"><math.h></a>
13279 double sqrt(double x);
13280 float sqrtf(float x);
13281 long double sqrtl(long double x);
13283 <p><b>Description</b>
13284 <p><a name="7.12.7.5p2" href="#7.12.7.5p2"><small>2</small></a>
13285 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
13286 the argument is less than zero.
13288 <p><a name="7.12.7.5p3" href="#7.12.7.5p3"><small>3</small></a>
13289 The sqrt functions return (sqrt)x.
13295 <p><small><a href="#Contents">Contents</a></small>
13296 <h4><a name="7.12.8" href="#7.12.8">7.12.8 Error and gamma functions</a></h4>
13298 <p><small><a href="#Contents">Contents</a></small>
13299 <h5><a name="7.12.8.1" href="#7.12.8.1">7.12.8.1 The erf functions</a></h5>
13301 <p><a name="7.12.8.1p1" href="#7.12.8.1p1"><small>1</small></a>
13303 #include <a href="#7.12"><math.h></a>
13304 double erf(double x);
13305 float erff(float x);
13306 long double erfl(long double x);
13308 <p><b>Description</b>
13309 <p><a name="7.12.8.1p2" href="#7.12.8.1p2"><small>2</small></a>
13310 The erf functions compute the error function of x.
13312 <p><a name="7.12.8.1p3" href="#7.12.8.1p3"><small>3</small></a>
13318 The erf functions return erf x =
13326 <p><small><a href="#Contents">Contents</a></small>
13327 <h5><a name="7.12.8.2" href="#7.12.8.2">7.12.8.2 The erfc functions</a></h5>
13329 <p><a name="7.12.8.2p1" href="#7.12.8.2p1"><small>1</small></a>
13331 #include <a href="#7.12"><math.h></a>
13332 double erfc(double x);
13333 float erfcf(float x);
13334 long double erfcl(long double x);
13336 <p><b>Description</b>
13337 <p><a name="7.12.8.2p2" href="#7.12.8.2p2"><small>2</small></a>
13338 The erfc functions compute the complementary error function of x. A range error
13339 occurs if x is too large.
13342 <p><a name="7.12.8.2p3" href="#7.12.8.2p3"><small>3</small></a>
13348 The erfc functions return erfc x = 1 - erf x =
13356 <p><small><a href="#Contents">Contents</a></small>
13357 <h5><a name="7.12.8.3" href="#7.12.8.3">7.12.8.3 The lgamma functions</a></h5>
13359 <p><a name="7.12.8.3p1" href="#7.12.8.3p1"><small>1</small></a>
13361 #include <a href="#7.12"><math.h></a>
13362 double lgamma(double x);
13363 float lgammaf(float x);
13364 long double lgammal(long double x);
13366 <p><b>Description</b>
13367 <p><a name="7.12.8.3p2" href="#7.12.8.3p2"><small>2</small></a>
13368 The lgamma functions compute the natural logarithm of the absolute value of gamma of
13369 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
13372 <p><a name="7.12.8.3p3" href="#7.12.8.3p3"><small>3</small></a>
13373 The lgamma functions return loge | (Gamma)(x) |.
13375 <p><small><a href="#Contents">Contents</a></small>
13376 <h5><a name="7.12.8.4" href="#7.12.8.4">7.12.8.4 The tgamma functions</a></h5>
13378 <p><a name="7.12.8.4p1" href="#7.12.8.4p1"><small>1</small></a>
13380 #include <a href="#7.12"><math.h></a>
13381 double tgamma(double x);
13382 float tgammaf(float x);
13383 long double tgammal(long double x);
13385 <p><b>Description</b>
13386 <p><a name="7.12.8.4p2" href="#7.12.8.4p2"><small>2</small></a>
13387 The tgamma functions compute the gamma function of x. A domain error or pole error
13388 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
13389 too large and may occur if the magnitude of x is too small.
13391 <p><a name="7.12.8.4p3" href="#7.12.8.4p3"><small>3</small></a>
13392 The tgamma functions return (Gamma)(x).
13395 <p><small><a href="#Contents">Contents</a></small>
13396 <h4><a name="7.12.9" href="#7.12.9">7.12.9 Nearest integer functions</a></h4>
13398 <p><small><a href="#Contents">Contents</a></small>
13399 <h5><a name="7.12.9.1" href="#7.12.9.1">7.12.9.1 The ceil functions</a></h5>
13401 <p><a name="7.12.9.1p1" href="#7.12.9.1p1"><small>1</small></a>
13403 #include <a href="#7.12"><math.h></a>
13404 double ceil(double x);
13405 float ceilf(float x);
13406 long double ceill(long double x);
13408 <p><b>Description</b>
13409 <p><a name="7.12.9.1p2" href="#7.12.9.1p2"><small>2</small></a>
13410 The ceil functions compute the smallest integer value not less than x.
13412 <p><a name="7.12.9.1p3" href="#7.12.9.1p3"><small>3</small></a>
13413 The ceil functions return [^x^], expressed as a floating-point number.
13415 <p><small><a href="#Contents">Contents</a></small>
13416 <h5><a name="7.12.9.2" href="#7.12.9.2">7.12.9.2 The floor functions</a></h5>
13418 <p><a name="7.12.9.2p1" href="#7.12.9.2p1"><small>1</small></a>
13420 #include <a href="#7.12"><math.h></a>
13421 double floor(double x);
13422 float floorf(float x);
13423 long double floorl(long double x);
13425 <p><b>Description</b>
13426 <p><a name="7.12.9.2p2" href="#7.12.9.2p2"><small>2</small></a>
13427 The floor functions compute the largest integer value not greater than x.
13429 <p><a name="7.12.9.2p3" href="#7.12.9.2p3"><small>3</small></a>
13430 The floor functions return [_x_], expressed as a floating-point number.
13432 <p><small><a href="#Contents">Contents</a></small>
13433 <h5><a name="7.12.9.3" href="#7.12.9.3">7.12.9.3 The nearbyint functions</a></h5>
13435 <p><a name="7.12.9.3p1" href="#7.12.9.3p1"><small>1</small></a>
13437 #include <a href="#7.12"><math.h></a>
13438 double nearbyint(double x);
13439 float nearbyintf(float x);
13440 long double nearbyintl(long double x);
13442 <p><b>Description</b>
13443 <p><a name="7.12.9.3p2" href="#7.12.9.3p2"><small>2</small></a>
13444 The nearbyint functions round their argument to an integer value in floating-point
13445 format, using the current rounding direction and without raising the ''inexact'' floating-
13449 <p><a name="7.12.9.3p3" href="#7.12.9.3p3"><small>3</small></a>
13450 The nearbyint functions return the rounded integer value.
13452 <p><small><a href="#Contents">Contents</a></small>
13453 <h5><a name="7.12.9.4" href="#7.12.9.4">7.12.9.4 The rint functions</a></h5>
13455 <p><a name="7.12.9.4p1" href="#7.12.9.4p1"><small>1</small></a>
13457 #include <a href="#7.12"><math.h></a>
13458 double rint(double x);
13459 float rintf(float x);
13460 long double rintl(long double x);
13462 <p><b>Description</b>
13463 <p><a name="7.12.9.4p2" href="#7.12.9.4p2"><small>2</small></a>
13464 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
13465 rint functions may raise the ''inexact'' floating-point exception if the result differs in
13466 value from the argument.
13468 <p><a name="7.12.9.4p3" href="#7.12.9.4p3"><small>3</small></a>
13469 The rint functions return the rounded integer value.
13471 <p><small><a href="#Contents">Contents</a></small>
13472 <h5><a name="7.12.9.5" href="#7.12.9.5">7.12.9.5 The lrint and llrint functions</a></h5>
13474 <p><a name="7.12.9.5p1" href="#7.12.9.5p1"><small>1</small></a>
13476 #include <a href="#7.12"><math.h></a>
13477 long int lrint(double x);
13478 long int lrintf(float x);
13479 long int lrintl(long double x);
13480 long long int llrint(double x);
13481 long long int llrintf(float x);
13482 long long int llrintl(long double x);
13484 <p><b>Description</b>
13485 <p><a name="7.12.9.5p2" href="#7.12.9.5p2"><small>2</small></a>
13486 The lrint and llrint functions round their argument to the nearest integer value,
13487 rounding according to the current rounding direction. If the rounded value is outside the
13488 range of the return type, the numeric result is unspecified and a domain error or range
13491 <p><a name="7.12.9.5p3" href="#7.12.9.5p3"><small>3</small></a>
13492 The lrint and llrint functions return the rounded integer value.
13495 <p><small><a href="#Contents">Contents</a></small>
13496 <h5><a name="7.12.9.6" href="#7.12.9.6">7.12.9.6 The round functions</a></h5>
13498 <p><a name="7.12.9.6p1" href="#7.12.9.6p1"><small>1</small></a>
13500 #include <a href="#7.12"><math.h></a>
13501 double round(double x);
13502 float roundf(float x);
13503 long double roundl(long double x);
13505 <p><b>Description</b>
13506 <p><a name="7.12.9.6p2" href="#7.12.9.6p2"><small>2</small></a>
13507 The round functions round their argument to the nearest integer value in floating-point
13508 format, rounding halfway cases away from zero, regardless of the current rounding
13511 <p><a name="7.12.9.6p3" href="#7.12.9.6p3"><small>3</small></a>
13512 The round functions return the rounded integer value.
13514 <p><small><a href="#Contents">Contents</a></small>
13515 <h5><a name="7.12.9.7" href="#7.12.9.7">7.12.9.7 The lround and llround functions</a></h5>
13517 <p><a name="7.12.9.7p1" href="#7.12.9.7p1"><small>1</small></a>
13519 #include <a href="#7.12"><math.h></a>
13520 long int lround(double x);
13521 long int lroundf(float x);
13522 long int lroundl(long double x);
13523 long long int llround(double x);
13524 long long int llroundf(float x);
13525 long long int llroundl(long double x);
13527 <p><b>Description</b>
13528 <p><a name="7.12.9.7p2" href="#7.12.9.7p2"><small>2</small></a>
13529 The lround and llround functions round their argument to the nearest integer value,
13530 rounding halfway cases away from zero, regardless of the current rounding direction. If
13531 the rounded value is outside the range of the return type, the numeric result is unspecified
13532 and a domain error or range error may occur.
13534 <p><a name="7.12.9.7p3" href="#7.12.9.7p3"><small>3</small></a>
13535 The lround and llround functions return the rounded integer value.
13537 <p><small><a href="#Contents">Contents</a></small>
13538 <h5><a name="7.12.9.8" href="#7.12.9.8">7.12.9.8 The trunc functions</a></h5>
13540 <p><a name="7.12.9.8p1" href="#7.12.9.8p1"><small>1</small></a>
13543 #include <a href="#7.12"><math.h></a>
13544 double trunc(double x);
13545 float truncf(float x);
13546 long double truncl(long double x);
13548 <p><b>Description</b>
13549 <p><a name="7.12.9.8p2" href="#7.12.9.8p2"><small>2</small></a>
13550 The trunc functions round their argument to the integer value, in floating format,
13551 nearest to but no larger in magnitude than the argument.
13553 <p><a name="7.12.9.8p3" href="#7.12.9.8p3"><small>3</small></a>
13554 The trunc functions return the truncated integer value.
13556 <p><small><a href="#Contents">Contents</a></small>
13557 <h4><a name="7.12.10" href="#7.12.10">7.12.10 Remainder functions</a></h4>
13559 <p><small><a href="#Contents">Contents</a></small>
13560 <h5><a name="7.12.10.1" href="#7.12.10.1">7.12.10.1 The fmod functions</a></h5>
13562 <p><a name="7.12.10.1p1" href="#7.12.10.1p1"><small>1</small></a>
13564 #include <a href="#7.12"><math.h></a>
13565 double fmod(double x, double y);
13566 float fmodf(float x, float y);
13567 long double fmodl(long double x, long double y);
13569 <p><b>Description</b>
13570 <p><a name="7.12.10.1p2" href="#7.12.10.1p2"><small>2</small></a>
13571 The fmod functions compute the floating-point remainder of x/y.
13573 <p><a name="7.12.10.1p3" href="#7.12.10.1p3"><small>3</small></a>
13574 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
13575 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
13576 whether a domain error occurs or the fmod functions return zero is implementation-
13579 <p><small><a href="#Contents">Contents</a></small>
13580 <h5><a name="7.12.10.2" href="#7.12.10.2">7.12.10.2 The remainder functions</a></h5>
13582 <p><a name="7.12.10.2p1" href="#7.12.10.2p1"><small>1</small></a>
13584 #include <a href="#7.12"><math.h></a>
13585 double remainder(double x, double y);
13586 float remainderf(float x, float y);
13587 long double remainderl(long double x, long double y);
13589 <p><b>Description</b>
13590 <p><a name="7.12.10.2p2" href="#7.12.10.2p2"><small>2</small></a>
13591 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note239"><b>239)</b></a></sup>
13598 <p><a name="7.12.10.2p3" href="#7.12.10.2p3"><small>3</small></a>
13599 The remainder functions return x REM y. If y is zero, whether a domain error occurs
13600 or the functions return zero is implementation defined.
13602 <p><b>Footnotes</b>
13603 <p><small><a name="note239" href="#note239">239)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
13604 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
13605 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for
13606 all implementations.
13609 <p><small><a href="#Contents">Contents</a></small>
13610 <h5><a name="7.12.10.3" href="#7.12.10.3">7.12.10.3 The remquo functions</a></h5>
13612 <p><a name="7.12.10.3p1" href="#7.12.10.3p1"><small>1</small></a>
13614 #include <a href="#7.12"><math.h></a>
13615 double remquo(double x, double y, int *quo);
13616 float remquof(float x, float y, int *quo);
13617 long double remquol(long double x, long double y,
13620 <p><b>Description</b>
13621 <p><a name="7.12.10.3p2" href="#7.12.10.3p2"><small>2</small></a>
13622 The remquo functions compute the same remainder as the remainder functions. In
13623 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
13624 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
13625 n is an implementation-defined integer greater than or equal to 3.
13627 <p><a name="7.12.10.3p3" href="#7.12.10.3p3"><small>3</small></a>
13628 The remquo functions return x REM y. If y is zero, the value stored in the object
13629 pointed to by quo is unspecified and whether a domain error occurs or the functions
13630 return zero is implementation defined.
13632 <p><small><a href="#Contents">Contents</a></small>
13633 <h4><a name="7.12.11" href="#7.12.11">7.12.11 Manipulation functions</a></h4>
13635 <p><small><a href="#Contents">Contents</a></small>
13636 <h5><a name="7.12.11.1" href="#7.12.11.1">7.12.11.1 The copysign functions</a></h5>
13638 <p><a name="7.12.11.1p1" href="#7.12.11.1p1"><small>1</small></a>
13640 #include <a href="#7.12"><math.h></a>
13641 double copysign(double x, double y);
13642 float copysignf(float x, float y);
13643 long double copysignl(long double x, long double y);
13645 <p><b>Description</b>
13646 <p><a name="7.12.11.1p2" href="#7.12.11.1p2"><small>2</small></a>
13647 The copysign functions produce a value with the magnitude of x and the sign of y.
13648 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
13649 represent a signed zero but do not treat negative zero consistently in arithmetic
13650 operations, the copysign functions regard the sign of zero as positive.
13652 <p><a name="7.12.11.1p3" href="#7.12.11.1p3"><small>3</small></a>
13653 The copysign functions return a value with the magnitude of x and the sign of y.
13656 <p><small><a href="#Contents">Contents</a></small>
13657 <h5><a name="7.12.11.2" href="#7.12.11.2">7.12.11.2 The nan functions</a></h5>
13659 <p><a name="7.12.11.2p1" href="#7.12.11.2p1"><small>1</small></a>
13661 #include <a href="#7.12"><math.h></a>
13662 double nan(const char *tagp);
13663 float nanf(const char *tagp);
13664 long double nanl(const char *tagp);
13666 <p><b>Description</b>
13667 <p><a name="7.12.11.2p2" href="#7.12.11.2p2"><small>2</small></a>
13668 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
13669 sequence)", (char**) NULL); the call nan("") is equivalent to
13670 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
13671 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
13672 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
13675 <p><a name="7.12.11.2p3" href="#7.12.11.2p3"><small>3</small></a>
13676 The nan functions return a quiet NaN, if available, with content indicated through tagp.
13677 If the implementation does not support quiet NaNs, the functions return zero.
13678 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13680 <p><small><a href="#Contents">Contents</a></small>
13681 <h5><a name="7.12.11.3" href="#7.12.11.3">7.12.11.3 The nextafter functions</a></h5>
13683 <p><a name="7.12.11.3p1" href="#7.12.11.3p1"><small>1</small></a>
13685 #include <a href="#7.12"><math.h></a>
13686 double nextafter(double x, double y);
13687 float nextafterf(float x, float y);
13688 long double nextafterl(long double x, long double y);
13690 <p><b>Description</b>
13691 <p><a name="7.12.11.3p2" href="#7.12.11.3p2"><small>2</small></a>
13692 The nextafter functions determine the next representable value, in the type of the
13693 function, after x in the direction of y, where x and y are first converted to the type of the
13694 function.<sup><a href="#note240"><b>240)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
13695 if the magnitude of x is the largest finite value representable in the type and the result is
13696 infinite or not representable in the type.
13698 <p><a name="7.12.11.3p3" href="#7.12.11.3p3"><small>3</small></a>
13699 The nextafter functions return the next representable value in the specified format
13700 after x in the direction of y.
13705 <p><b>Footnotes</b>
13706 <p><small><a name="note240" href="#note240">240)</a> The argument values are converted to the type of the function, even by a macro implementation of the
13710 <p><small><a href="#Contents">Contents</a></small>
13711 <h5><a name="7.12.11.4" href="#7.12.11.4">7.12.11.4 The nexttoward functions</a></h5>
13713 <p><a name="7.12.11.4p1" href="#7.12.11.4p1"><small>1</small></a>
13715 #include <a href="#7.12"><math.h></a>
13716 double nexttoward(double x, long double y);
13717 float nexttowardf(float x, long double y);
13718 long double nexttowardl(long double x, long double y);
13720 <p><b>Description</b>
13721 <p><a name="7.12.11.4p2" href="#7.12.11.4p2"><small>2</small></a>
13722 The nexttoward functions are equivalent to the nextafter functions except that the
13723 second parameter has type long double and the functions return y converted to the
13724 type of the function if x equals y.<sup><a href="#note241"><b>241)</b></a></sup>
13726 <p><b>Footnotes</b>
13727 <p><small><a name="note241" href="#note241">241)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
13728 range or precision in a floating second argument.
13731 <p><small><a href="#Contents">Contents</a></small>
13732 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
13734 <p><small><a href="#Contents">Contents</a></small>
13735 <h5><a name="7.12.12.1" href="#7.12.12.1">7.12.12.1 The fdim functions</a></h5>
13737 <p><a name="7.12.12.1p1" href="#7.12.12.1p1"><small>1</small></a>
13739 #include <a href="#7.12"><math.h></a>
13740 double fdim(double x, double y);
13741 float fdimf(float x, float y);
13742 long double fdiml(long double x, long double y);
13744 <p><b>Description</b>
13745 <p><a name="7.12.12.1p2" href="#7.12.12.1p2"><small>2</small></a>
13746 The fdim functions determine the positive difference between their arguments:
13752 A range error may occur.
13754 <p><a name="7.12.12.1p3" href="#7.12.12.1p3"><small>3</small></a>
13755 The fdim functions return the positive difference value.
13757 <p><small><a href="#Contents">Contents</a></small>
13758 <h5><a name="7.12.12.2" href="#7.12.12.2">7.12.12.2 The fmax functions</a></h5>
13760 <p><a name="7.12.12.2p1" href="#7.12.12.2p1"><small>1</small></a>
13762 #include <a href="#7.12"><math.h></a>
13763 double fmax(double x, double y);
13764 float fmaxf(float x, float y);
13765 long double fmaxl(long double x, long double y);
13771 <p><b>Description</b>
13772 <p><a name="7.12.12.2p2" href="#7.12.12.2p2"><small>2</small></a>
13773 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note242"><b>242)</b></a></sup>
13775 <p><a name="7.12.12.2p3" href="#7.12.12.2p3"><small>3</small></a>
13776 The fmax functions return the maximum numeric value of their arguments.
13778 <p><b>Footnotes</b>
13779 <p><small><a name="note242" href="#note242">242)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
13780 fmax functions choose the numeric value. See <a href="#F.10.9.2">F.10.9.2</a>.
13783 <p><small><a href="#Contents">Contents</a></small>
13784 <h5><a name="7.12.12.3" href="#7.12.12.3">7.12.12.3 The fmin functions</a></h5>
13786 <p><a name="7.12.12.3p1" href="#7.12.12.3p1"><small>1</small></a>
13788 #include <a href="#7.12"><math.h></a>
13789 double fmin(double x, double y);
13790 float fminf(float x, float y);
13791 long double fminl(long double x, long double y);
13793 <p><b>Description</b>
13794 <p><a name="7.12.12.3p2" href="#7.12.12.3p2"><small>2</small></a>
13795 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note243"><b>243)</b></a></sup>
13797 <p><a name="7.12.12.3p3" href="#7.12.12.3p3"><small>3</small></a>
13798 The fmin functions return the minimum numeric value of their arguments.
13800 <p><b>Footnotes</b>
13801 <p><small><a name="note243" href="#note243">243)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
13804 <p><small><a href="#Contents">Contents</a></small>
13805 <h4><a name="7.12.13" href="#7.12.13">7.12.13 Floating multiply-add</a></h4>
13807 <p><small><a href="#Contents">Contents</a></small>
13808 <h5><a name="7.12.13.1" href="#7.12.13.1">7.12.13.1 The fma functions</a></h5>
13810 <p><a name="7.12.13.1p1" href="#7.12.13.1p1"><small>1</small></a>
13812 #include <a href="#7.12"><math.h></a>
13813 double fma(double x, double y, double z);
13814 float fmaf(float x, float y, float z);
13815 long double fmal(long double x, long double y,
13818 <p><b>Description</b>
13819 <p><a name="7.12.13.1p2" href="#7.12.13.1p2"><small>2</small></a>
13820 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
13821 the value (as if) to infinite precision and round once to the result format, according to the
13822 current rounding mode. A range error may occur.
13824 <p><a name="7.12.13.1p3" href="#7.12.13.1p3"><small>3</small></a>
13825 The fma functions return (x x y) + z, rounded as one ternary operation.
13832 <p><small><a href="#Contents">Contents</a></small>
13833 <h4><a name="7.12.14" href="#7.12.14">7.12.14 Comparison macros</a></h4>
13834 <p><a name="7.12.14p1" href="#7.12.14p1"><small>1</small></a>
13835 The relational and equality operators support the usual mathematical relationships
13836 between numeric values. For any ordered pair of numeric values exactly one of the
13837 relationships -- less, greater, and equal -- is true. Relational operators may raise the
13838 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
13839 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note244"><b>244)</b></a></sup> The following
13840 subclauses provide macros that are quiet (non floating-point exception raising) versions
13841 of the relational operators, and other comparison macros that facilitate writing efficient
13842 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
13843 the synopses in this subclause, real-floating indicates that the argument shall be an
13844 expression of real floating type<sup><a href="#note245"><b>245)</b></a></sup> (both arguments need not have the same type).<sup><a href="#note246"><b>246)</b></a></sup>
13846 <p><b>Footnotes</b>
13847 <p><small><a name="note244" href="#note244">244)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
13848 the operands compare unordered, as an error indicator for programs written without consideration of
13849 NaNs; the result in these cases is false.
13851 <p><small><a name="note245" href="#note245">245)</a> If any argument is of integer type, or any other type that is not a real floating type, the behavior is
13854 <p><small><a name="note246" href="#note246">246)</a> Whether an argument represented in a format wider than its semantic type is converted to the semantic
13855 type is unspecified.
13858 <p><small><a href="#Contents">Contents</a></small>
13859 <h5><a name="7.12.14.1" href="#7.12.14.1">7.12.14.1 The isgreater macro</a></h5>
13861 <p><a name="7.12.14.1p1" href="#7.12.14.1p1"><small>1</small></a>
13863 #include <a href="#7.12"><math.h></a>
13864 int isgreater(real-floating x, real-floating y);
13866 <p><b>Description</b>
13867 <p><a name="7.12.14.1p2" href="#7.12.14.1p2"><small>2</small></a>
13868 The isgreater macro determines whether its first argument is greater than its second
13869 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
13870 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
13871 exception when x and y are unordered.
13873 <p><a name="7.12.14.1p3" href="#7.12.14.1p3"><small>3</small></a>
13874 The isgreater macro returns the value of (x) > (y).
13876 <p><small><a href="#Contents">Contents</a></small>
13877 <h5><a name="7.12.14.2" href="#7.12.14.2">7.12.14.2 The isgreaterequal macro</a></h5>
13879 <p><a name="7.12.14.2p1" href="#7.12.14.2p1"><small>1</small></a>
13881 #include <a href="#7.12"><math.h></a>
13882 int isgreaterequal(real-floating x, real-floating y);
13889 <p><b>Description</b>
13890 <p><a name="7.12.14.2p2" href="#7.12.14.2p2"><small>2</small></a>
13891 The isgreaterequal macro determines whether its first argument is greater than or
13892 equal to its second argument. The value of isgreaterequal(x, y) is always equal
13893 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
13894 not raise the ''invalid'' floating-point exception when x and y are unordered.
13896 <p><a name="7.12.14.2p3" href="#7.12.14.2p3"><small>3</small></a>
13897 The isgreaterequal macro returns the value of (x) >= (y).
13899 <p><small><a href="#Contents">Contents</a></small>
13900 <h5><a name="7.12.14.3" href="#7.12.14.3">7.12.14.3 The isless macro</a></h5>
13902 <p><a name="7.12.14.3p1" href="#7.12.14.3p1"><small>1</small></a>
13904 #include <a href="#7.12"><math.h></a>
13905 int isless(real-floating x, real-floating y);
13907 <p><b>Description</b>
13908 <p><a name="7.12.14.3p2" href="#7.12.14.3p2"><small>2</small></a>
13909 The isless macro determines whether its first argument is less than its second
13910 argument. The value of isless(x, y) is always equal to (x) < (y); however,
13911 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
13912 exception when x and y are unordered.
13914 <p><a name="7.12.14.3p3" href="#7.12.14.3p3"><small>3</small></a>
13915 The isless macro returns the value of (x) < (y).
13917 <p><small><a href="#Contents">Contents</a></small>
13918 <h5><a name="7.12.14.4" href="#7.12.14.4">7.12.14.4 The islessequal macro</a></h5>
13920 <p><a name="7.12.14.4p1" href="#7.12.14.4p1"><small>1</small></a>
13922 #include <a href="#7.12"><math.h></a>
13923 int islessequal(real-floating x, real-floating y);
13925 <p><b>Description</b>
13926 <p><a name="7.12.14.4p2" href="#7.12.14.4p2"><small>2</small></a>
13927 The islessequal macro determines whether its first argument is less than or equal to
13928 its second argument. The value of islessequal(x, y) is always equal to
13929 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
13930 the ''invalid'' floating-point exception when x and y are unordered.
13932 <p><a name="7.12.14.4p3" href="#7.12.14.4p3"><small>3</small></a>
13933 The islessequal macro returns the value of (x) <= (y).
13936 <p><small><a href="#Contents">Contents</a></small>
13937 <h5><a name="7.12.14.5" href="#7.12.14.5">7.12.14.5 The islessgreater macro</a></h5>
13939 <p><a name="7.12.14.5p1" href="#7.12.14.5p1"><small>1</small></a>
13941 #include <a href="#7.12"><math.h></a>
13942 int islessgreater(real-floating x, real-floating y);
13944 <p><b>Description</b>
13945 <p><a name="7.12.14.5p2" href="#7.12.14.5p2"><small>2</small></a>
13946 The islessgreater macro determines whether its first argument is less than or
13947 greater than its second argument. The islessgreater(x, y) macro is similar to
13948 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
13949 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
13952 <p><a name="7.12.14.5p3" href="#7.12.14.5p3"><small>3</small></a>
13953 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
13955 <p><small><a href="#Contents">Contents</a></small>
13956 <h5><a name="7.12.14.6" href="#7.12.14.6">7.12.14.6 The isunordered macro</a></h5>
13958 <p><a name="7.12.14.6p1" href="#7.12.14.6p1"><small>1</small></a>
13960 #include <a href="#7.12"><math.h></a>
13961 int isunordered(real-floating x, real-floating y);
13963 <p><b>Description</b>
13964 <p><a name="7.12.14.6p2" href="#7.12.14.6p2"><small>2</small></a>
13965 The isunordered macro determines whether its arguments are unordered.
13967 <p><a name="7.12.14.6p3" href="#7.12.14.6p3"><small>3</small></a>
13968 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
13971 <p><small><a href="#Contents">Contents</a></small>
13972 <h3><a name="7.13" href="#7.13">7.13 Nonlocal jumps <setjmp.h></a></h3>
13973 <p><a name="7.13p1" href="#7.13p1"><small>1</small></a>
13974 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
13975 one type, for bypassing the normal function call and return discipline.<sup><a href="#note247"><b>247)</b></a></sup>
13976 <p><a name="7.13p2" href="#7.13p2"><small>2</small></a>
13977 The type declared is
13981 which is an array type suitable for holding the information needed to restore a calling
13982 environment. The environment of a call to the setjmp macro consists of information
13983 sufficient for a call to the longjmp function to return execution to the correct block and
13984 invocation of that block, were it called recursively. It does not include the state of the
13985 floating-point status flags, of open files, or of any other component of the abstract
13987 <p><a name="7.13p3" href="#7.13p3"><small>3</small></a>
13988 It is unspecified whether setjmp is a macro or an identifier declared with external
13989 linkage. If a macro definition is suppressed in order to access an actual function, or a
13990 program defines an external identifier with the name setjmp, the behavior is undefined.
13992 <p><b>Footnotes</b>
13993 <p><small><a name="note247" href="#note247">247)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
13997 <p><small><a href="#Contents">Contents</a></small>
13998 <h4><a name="7.13.1" href="#7.13.1">7.13.1 Save calling environment</a></h4>
14000 <p><small><a href="#Contents">Contents</a></small>
14001 <h5><a name="7.13.1.1" href="#7.13.1.1">7.13.1.1 The setjmp macro</a></h5>
14003 <p><a name="7.13.1.1p1" href="#7.13.1.1p1"><small>1</small></a>
14005 #include <a href="#7.13"><setjmp.h></a>
14006 int setjmp(jmp_buf env);
14008 <p><b>Description</b>
14009 <p><a name="7.13.1.1p2" href="#7.13.1.1p2"><small>2</small></a>
14010 The setjmp macro saves its calling environment in its jmp_buf argument for later use
14011 by the longjmp function.
14013 <p><a name="7.13.1.1p3" href="#7.13.1.1p3"><small>3</small></a>
14014 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
14015 return is from a call to the longjmp function, the setjmp macro returns a nonzero
14017 <p><b>Environmental limits</b>
14018 <p><a name="7.13.1.1p4" href="#7.13.1.1p4"><small>4</small></a>
14019 An invocation of the setjmp macro shall appear only in one of the following contexts:
14021 <li> the entire controlling expression of a selection or iteration statement;
14022 <li> one operand of a relational or equality operator with the other operand an integer
14023 constant expression, with the resulting expression being the entire controlling
14027 expression of a selection or iteration statement;
14028 <li> the operand of a unary ! operator with the resulting expression being the entire
14029 controlling expression of a selection or iteration statement; or
14030 <li> the entire expression of an expression statement (possibly cast to void).
14032 <p><a name="7.13.1.1p5" href="#7.13.1.1p5"><small>5</small></a>
14033 If the invocation appears in any other context, the behavior is undefined.
14035 <p><small><a href="#Contents">Contents</a></small>
14036 <h4><a name="7.13.2" href="#7.13.2">7.13.2 Restore calling environment</a></h4>
14038 <p><small><a href="#Contents">Contents</a></small>
14039 <h5><a name="7.13.2.1" href="#7.13.2.1">7.13.2.1 The longjmp function</a></h5>
14041 <p><a name="7.13.2.1p1" href="#7.13.2.1p1"><small>1</small></a>
14043 #include <a href="#7.13"><setjmp.h></a>
14044 _Noreturn void longjmp(jmp_buf env, int val);
14046 <p><b>Description</b>
14047 <p><a name="7.13.2.1p2" href="#7.13.2.1p2"><small>2</small></a>
14048 The longjmp function restores the environment saved by the most recent invocation of
14049 the setjmp macro in the same invocation of the program with the corresponding
14050 jmp_buf argument. If there has been no such invocation, or if the invocation was from
14051 another thread of execution, or if the function containing the invocation of the setjmp
14052 macro has terminated execution<sup><a href="#note248"><b>248)</b></a></sup> in the interim, or if the invocation of the setjmp
14053 macro was within the scope of an identifier with variably modified type and execution has
14054 left that scope in the interim, the behavior is undefined.
14055 <p><a name="7.13.2.1p3" href="#7.13.2.1p3"><small>3</small></a>
14056 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note249"><b>249)</b></a></sup>
14057 have state, as of the time the longjmp function was called, except that the values of
14058 objects of automatic storage duration that are local to the function containing the
14059 invocation of the corresponding setjmp macro that do not have volatile-qualified type
14060 and have been changed between the setjmp invocation and longjmp call are
14063 <p><a name="7.13.2.1p4" href="#7.13.2.1p4"><small>4</small></a>
14064 After longjmp is completed, thread execution continues as if the corresponding
14065 invocation of the setjmp macro had just returned the value specified by val. The
14066 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
14067 the setjmp macro returns the value 1.
14068 <p><a name="7.13.2.1p5" href="#7.13.2.1p5"><small>5</small></a>
14069 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
14070 might cause memory associated with a variable length array object to be squandered.
14077 #include <a href="#7.13"><setjmp.h></a>
14084 int x[n]; // valid: f is not terminated
14090 int a[n]; // a may remain allocated
14095 int b[n]; // b may remain allocated
14096 longjmp(buf, 2); // might cause memory loss
14100 <p><b>Footnotes</b>
14101 <p><small><a name="note248" href="#note248">248)</a> For example, by executing a return statement or because another longjmp call has caused a
14102 transfer to a setjmp invocation in a function earlier in the set of nested calls.
14104 <p><small><a name="note249" href="#note249">249)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
14107 <p><small><a href="#Contents">Contents</a></small>
14108 <h3><a name="7.14" href="#7.14">7.14 Signal handling <signal.h></a></h3>
14109 <p><a name="7.14p1" href="#7.14p1"><small>1</small></a>
14110 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
14111 for handling various signals (conditions that may be reported during program execution).
14112 <p><a name="7.14p2" href="#7.14p2"><small>2</small></a>
14113 The type defined is
14117 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
14118 an atomic entity, even in the presence of asynchronous interrupts.
14119 <p><a name="7.14p3" href="#7.14p3"><small>3</small></a>
14120 The macros defined are
14126 which expand to constant expressions with distinct values that have type compatible with
14127 the second argument to, and the return value of, the signal function, and whose values
14128 compare unequal to the address of any declarable function; and the following, which
14129 expand to positive integer constant expressions with type int and distinct values that are
14130 the signal numbers, each corresponding to the specified condition:
14132 SIGABRT abnormal termination, such as is initiated by the abort function
14133 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
14134 resulting in overflow
14135 SIGILL detection of an invalid function image, such as an invalid instruction
14136 SIGINT receipt of an interactive attention signal
14137 SIGSEGV an invalid access to storage
14138 SIGTERM a termination request sent to the program
14140 <p><a name="7.14p4" href="#7.14p4"><small>4</small></a>
14141 An implementation need not generate any of these signals, except as a result of explicit
14142 calls to the raise function. Additional signals and pointers to undeclarable functions,
14143 with macro definitions beginning, respectively, with the letters SIG and an uppercase
14144 letter or with SIG_ and an uppercase letter,<sup><a href="#note250"><b>250)</b></a></sup> may also be specified by the
14145 implementation. The complete set of signals, their semantics, and their default handling
14146 is implementation-defined; all signal numbers shall be positive.
14153 <p><b>Footnotes</b>
14154 <p><small><a name="note250" href="#note250">250)</a> See ''future library directions'' (<a href="#7.31.7">7.31.7</a>). The names of the signal numbers reflect the following terms
14155 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
14159 <p><small><a href="#Contents">Contents</a></small>
14160 <h4><a name="7.14.1" href="#7.14.1">7.14.1 Specify signal handling</a></h4>
14162 <p><small><a href="#Contents">Contents</a></small>
14163 <h5><a name="7.14.1.1" href="#7.14.1.1">7.14.1.1 The signal function</a></h5>
14165 <p><a name="7.14.1.1p1" href="#7.14.1.1p1"><small>1</small></a>
14167 #include <a href="#7.14"><signal.h></a>
14168 void (*signal(int sig, void (*func)(int)))(int);
14170 <p><b>Description</b>
14171 <p><a name="7.14.1.1p2" href="#7.14.1.1p2"><small>2</small></a>
14172 The signal function chooses one of three ways in which receipt of the signal number
14173 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
14174 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
14175 Otherwise, func shall point to a function to be called when that signal occurs. An
14176 invocation of such a function because of a signal, or (recursively) of any further functions
14177 called by that invocation (other than functions in the standard library),<sup><a href="#note251"><b>251)</b></a></sup> is called a
14179 <p><a name="7.14.1.1p3" href="#7.14.1.1p3"><small>3</small></a>
14180 When a signal occurs and func points to a function, it is implementation-defined
14181 whether the equivalent of signal(sig, SIG_DFL); is executed or the
14182 implementation prevents some implementation-defined set of signals (at least including
14183 sig) from occurring until the current signal handling has completed; in the case of
14184 SIGILL, the implementation may alternatively define that no action is taken. Then the
14185 equivalent of (*func)(sig); is executed. If and when the function returns, if the
14186 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
14187 value corresponding to a computational exception, the behavior is undefined; otherwise
14188 the program will resume execution at the point it was interrupted.
14189 <p><a name="7.14.1.1p4" href="#7.14.1.1p4"><small>4</small></a>
14190 If the signal occurs as the result of calling the abort or raise function, the signal
14191 handler shall not call the raise function.
14192 <p><a name="7.14.1.1p5" href="#7.14.1.1p5"><small>5</small></a>
14193 If the signal occurs other than as the result of calling the abort or raise function, the
14194 behavior is undefined if the signal handler refers to any object with static or thread
14195 storage duration that is not a lock-free atomic object other than by assigning a value to an
14196 object declared as volatile sig_atomic_t, or the signal handler calls any function
14197 in the standard library other than the abort function, the _Exit function, the
14198 quick_exit function, or the signal function with the first argument equal to the
14199 signal number corresponding to the signal that caused the invocation of the handler.
14200 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
14201 value of errno is indeterminate.<sup><a href="#note252"><b>252)</b></a></sup>
14205 <p><a name="7.14.1.1p6" href="#7.14.1.1p6"><small>6</small></a>
14206 At program startup, the equivalent of
14208 signal(sig, SIG_IGN);
14210 may be executed for some signals selected in an implementation-defined manner; the
14213 signal(sig, SIG_DFL);
14215 is executed for all other signals defined by the implementation.
14216 <p><a name="7.14.1.1p7" href="#7.14.1.1p7"><small>7</small></a>
14217 Use of this function in a multi-threaded program results in undefined behavior. The
14218 implementation shall behave as if no library function calls the signal function.
14220 <p><a name="7.14.1.1p8" href="#7.14.1.1p8"><small>8</small></a>
14221 If the request can be honored, the signal function returns the value of func for the
14222 most recent successful call to signal for the specified signal sig. Otherwise, a value of
14223 SIG_ERR is returned and a positive value is stored in errno.
14224 <p><b> Forward references</b>: the abort function (<a href="#7.22.4.1">7.22.4.1</a>), the exit function (<a href="#7.22.4.4">7.22.4.4</a>), the
14225 _Exit function (<a href="#7.22.4.5">7.22.4.5</a>), the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
14227 <p><b>Footnotes</b>
14228 <p><small><a name="note251" href="#note251">251)</a> This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler
14229 called via the abort function).
14231 <p><small><a name="note252" href="#note252">252)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
14234 <p><small><a href="#Contents">Contents</a></small>
14235 <h4><a name="7.14.2" href="#7.14.2">7.14.2 Send signal</a></h4>
14237 <p><small><a href="#Contents">Contents</a></small>
14238 <h5><a name="7.14.2.1" href="#7.14.2.1">7.14.2.1 The raise function</a></h5>
14240 <p><a name="7.14.2.1p1" href="#7.14.2.1p1"><small>1</small></a>
14242 #include <a href="#7.14"><signal.h></a>
14243 int raise(int sig);
14245 <p><b>Description</b>
14246 <p><a name="7.14.2.1p2" href="#7.14.2.1p2"><small>2</small></a>
14247 The raise function carries out the actions described in <a href="#7.14.1.1">7.14.1.1</a> for the signal sig. If a
14248 signal handler is called, the raise function shall not return until after the signal handler
14251 <p><a name="7.14.2.1p3" href="#7.14.2.1p3"><small>3</small></a>
14252 The raise function returns zero if successful, nonzero if unsuccessful.
14255 <p><small><a href="#Contents">Contents</a></small>
14256 <h3><a name="7.15" href="#7.15">7.15 Alignment <stdalign.h></a></h3>
14257 <p><a name="7.15p1" href="#7.15p1"><small>1</small></a>
14258 The header <a href="#7.15"><stdalign.h></a> defines four macros.
14259 <p><a name="7.15p2" href="#7.15p2"><small>2</small></a>
14264 expands to _Alignas; the macro
14268 expands to _Alignof.
14269 <p><a name="7.15p3" href="#7.15p3"><small>3</small></a>
14270 The remaining macros are suitable for use in #if preprocessing directives. They are
14272 __alignas_is_defined
14276 __alignof_is_defined
14278 which both expand to the integer constant 1.
14281 <p><small><a href="#Contents">Contents</a></small>
14282 <h3><a name="7.16" href="#7.16">7.16 Variable arguments <stdarg.h></a></h3>
14283 <p><a name="7.16p1" href="#7.16p1"><small>1</small></a>
14284 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
14285 through a list of arguments whose number and types are not known to the called function
14286 when it is translated.
14287 <p><a name="7.16p2" href="#7.16p2"><small>2</small></a>
14288 A function may be called with a variable number of arguments of varying types. As
14289 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
14290 parameter plays a special role in the access mechanism, and will be designated parmN in
14292 <p><a name="7.16p3" href="#7.16p3"><small>3</small></a>
14293 The type declared is
14297 which is a complete object type suitable for holding information needed by the macros
14298 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
14299 desired, the called function shall declare an object (generally referred to as ap in this
14300 subclause) having type va_list. The object ap may be passed as an argument to
14301 another function; if that function invokes the va_arg macro with parameter ap, the
14302 value of ap in the calling function is indeterminate and shall be passed to the va_end
14303 macro prior to any further reference to ap.<sup><a href="#note253"><b>253)</b></a></sup>
14305 <p><b>Footnotes</b>
14306 <p><small><a name="note253" href="#note253">253)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
14307 case the original function may make further use of the original list after the other function returns.
14310 <p><small><a href="#Contents">Contents</a></small>
14311 <h4><a name="7.16.1" href="#7.16.1">7.16.1 Variable argument list access macros</a></h4>
14312 <p><a name="7.16.1p1" href="#7.16.1p1"><small>1</small></a>
14313 The va_start and va_arg macros described in this subclause shall be implemented
14314 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
14315 identifiers declared with external linkage. If a macro definition is suppressed in order to
14316 access an actual function, or a program defines an external identifier with the same name,
14317 the behavior is undefined. Each invocation of the va_start and va_copy macros
14318 shall be matched by a corresponding invocation of the va_end macro in the same
14321 <p><small><a href="#Contents">Contents</a></small>
14322 <h5><a name="7.16.1.1" href="#7.16.1.1">7.16.1.1 The va_arg macro</a></h5>
14324 <p><a name="7.16.1.1p1" href="#7.16.1.1p1"><small>1</small></a>
14326 #include <a href="#7.16"><stdarg.h></a>
14327 type va_arg(va_list ap, type);
14329 <p><b>Description</b>
14330 <p><a name="7.16.1.1p2" href="#7.16.1.1p2"><small>2</small></a>
14331 The va_arg macro expands to an expression that has the specified type and the value of
14332 the next argument in the call. The parameter ap shall have been initialized by the
14333 va_start or va_copy macro (without an intervening invocation of the va_end
14336 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
14337 values of successive arguments are returned in turn. The parameter type shall be a type
14338 name specified such that the type of a pointer to an object that has the specified type can
14339 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
14340 type is not compatible with the type of the actual next argument (as promoted according
14341 to the default argument promotions), the behavior is undefined, except for the following
14344 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
14345 type, and the value is representable in both types;
14346 <li> one type is pointer to void and the other is a pointer to a character type.
14349 <p><a name="7.16.1.1p3" href="#7.16.1.1p3"><small>3</small></a>
14350 The first invocation of the va_arg macro after that of the va_start macro returns the
14351 value of the argument after that specified by parmN . Successive invocations return the
14352 values of the remaining arguments in succession.
14354 <p><small><a href="#Contents">Contents</a></small>
14355 <h5><a name="7.16.1.2" href="#7.16.1.2">7.16.1.2 The va_copy macro</a></h5>
14357 <p><a name="7.16.1.2p1" href="#7.16.1.2p1"><small>1</small></a>
14359 #include <a href="#7.16"><stdarg.h></a>
14360 void va_copy(va_list dest, va_list src);
14362 <p><b>Description</b>
14363 <p><a name="7.16.1.2p2" href="#7.16.1.2p2"><small>2</small></a>
14364 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
14365 been applied to dest followed by the same sequence of uses of the va_arg macro as
14366 had previously been used to reach the present state of src. Neither the va_copy nor
14367 va_start macro shall be invoked to reinitialize dest without an intervening
14368 invocation of the va_end macro for the same dest.
14370 <p><a name="7.16.1.2p3" href="#7.16.1.2p3"><small>3</small></a>
14371 The va_copy macro returns no value.
14373 <p><small><a href="#Contents">Contents</a></small>
14374 <h5><a name="7.16.1.3" href="#7.16.1.3">7.16.1.3 The va_end macro</a></h5>
14376 <p><a name="7.16.1.3p1" href="#7.16.1.3p1"><small>1</small></a>
14378 #include <a href="#7.16"><stdarg.h></a>
14379 void va_end(va_list ap);
14381 <p><b>Description</b>
14382 <p><a name="7.16.1.3p2" href="#7.16.1.3p2"><small>2</small></a>
14383 The va_end macro facilitates a normal return from the function whose variable
14384 argument list was referred to by the expansion of the va_start macro, or the function
14385 containing the expansion of the va_copy macro, that initialized the va_list ap. The
14386 va_end macro may modify ap so that it is no longer usable (without being reinitialized
14388 by the va_start or va_copy macro). If there is no corresponding invocation of the
14389 va_start or va_copy macro, or if the va_end macro is not invoked before the
14390 return, the behavior is undefined.
14392 <p><a name="7.16.1.3p3" href="#7.16.1.3p3"><small>3</small></a>
14393 The va_end macro returns no value.
14395 <p><small><a href="#Contents">Contents</a></small>
14396 <h5><a name="7.16.1.4" href="#7.16.1.4">7.16.1.4 The va_start macro</a></h5>
14398 <p><a name="7.16.1.4p1" href="#7.16.1.4p1"><small>1</small></a>
14400 #include <a href="#7.16"><stdarg.h></a>
14401 void va_start(va_list ap, parmN);
14403 <p><b>Description</b>
14404 <p><a name="7.16.1.4p2" href="#7.16.1.4p2"><small>2</small></a>
14405 The va_start macro shall be invoked before any access to the unnamed arguments.
14406 <p><a name="7.16.1.4p3" href="#7.16.1.4p3"><small>3</small></a>
14407 The va_start macro initializes ap for subsequent use by the va_arg and va_end
14408 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
14409 without an intervening invocation of the va_end macro for the same ap.
14410 <p><a name="7.16.1.4p4" href="#7.16.1.4p4"><small>4</small></a>
14411 The parameter parmN is the identifier of the rightmost parameter in the variable
14412 parameter list in the function definition (the one just before the , ...). If the parameter
14413 parmN is declared with the register storage class, with a function or array type, or
14414 with a type that is not compatible with the type that results after application of the default
14415 argument promotions, the behavior is undefined.
14417 <p><a name="7.16.1.4p5" href="#7.16.1.4p5"><small>5</small></a>
14418 The va_start macro returns no value.
14419 <p><a name="7.16.1.4p6" href="#7.16.1.4p6"><small>6</small></a>
14420 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
14421 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
14422 pointers is specified by the first argument to f1.
14425 #include <a href="#7.16"><stdarg.h></a>
14427 void f1(int n_ptrs, ...)
14430 char *array[MAXARGS];
14432 if (n_ptrs > MAXARGS)
14434 va_start(ap, n_ptrs);
14435 while (ptr_no < n_ptrs)
14436 array[ptr_no++] = va_arg(ap, char *);
14441 Each call to f1 is required to have visible the definition of the function or a declaration such as
14446 <p><a name="7.16.1.4p7" href="#7.16.1.4p7"><small>7</small></a>
14447 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
14448 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
14449 is gathered again and passed to function f4.
14452 #include <a href="#7.16"><stdarg.h></a>
14454 void f3(int n_ptrs, int f4_after, ...)
14456 va_list ap, ap_save;
14457 char *array[MAXARGS];
14459 if (n_ptrs > MAXARGS)
14461 va_start(ap, f4_after);
14462 while (ptr_no < n_ptrs) {
14463 array[ptr_no++] = va_arg(ap, char *);
14464 if (ptr_no == f4_after)
14465 va_copy(ap_save, ap);
14469 // Now process the saved copy.
14470 n_ptrs -= f4_after;
14472 while (ptr_no < n_ptrs)
14473 array[ptr_no++] = va_arg(ap_save, char *);
14479 <p><small><a href="#Contents">Contents</a></small>
14480 <h3><a name="7.17" href="#7.17">7.17 Atomics <stdatomic.h></a></h3>
14482 <p><small><a href="#Contents">Contents</a></small>
14483 <h4><a name="7.17.1" href="#7.17.1">7.17.1 Introduction</a></h4>
14484 <p><a name="7.17.1p1" href="#7.17.1p1"><small>1</small></a>
14485 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
14486 functions for performing atomic operations on data shared between threads.<sup><a href="#note254"><b>254)</b></a></sup>
14487 <p><a name="7.17.1p2" href="#7.17.1p2"><small>2</small></a>
14488 Implementations that define the macro __STDC_NO_ATOMICS__ need not provide
14489 this header nor support any of its facilities.
14490 <p><a name="7.17.1p3" href="#7.17.1p3"><small>3</small></a>
14491 The macros defined are the atomic lock-free macros
14493 ATOMIC_BOOL_LOCK_FREE
14494 ATOMIC_CHAR_LOCK_FREE
14495 ATOMIC_CHAR16_T_LOCK_FREE
14496 ATOMIC_CHAR32_T_LOCK_FREE
14497 ATOMIC_WCHAR_T_LOCK_FREE
14498 ATOMIC_SHORT_LOCK_FREE
14499 ATOMIC_INT_LOCK_FREE
14500 ATOMIC_LONG_LOCK_FREE
14501 ATOMIC_LLONG_LOCK_FREE
14502 ATOMIC_POINTER_LOCK_FREE
14504 which indicate the lock-free property of the corresponding atomic types (both signed and
14509 which expands to an initializer for an object of type atomic_flag.
14510 <p><a name="7.17.1p4" href="#7.17.1p4"><small>4</small></a>
14515 which is an enumerated type whose enumerators identify memory ordering constraints;
14519 which is a structure type representing a lock-free, primitive atomic flag; and several *
14520 atomic analogs of integer types.
14521 <p><a name="7.17.1p5" href="#7.17.1p5"><small>5</small></a>
14522 In the following synopses:
14524 <li> An A refers to one of the atomic types.
14525 <li> A C refers to its corresponding non-atomic type. *
14526 <li> An M refers to the type of the other argument for arithmetic operations. For atomic
14527 integer types, M is C. For atomic pointer types, M is ptrdiff_t.
14530 <li> The functions not ending in _explicit have the same semantics as the
14531 corresponding _explicit function with memory_order_seq_cst for the
14532 memory_order argument.
14534 <p><a name="7.17.1p6" href="#7.17.1p6"><small>6</small></a>
14535 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
14536 changed in the standard. This qualification means that volatility is preserved when applying these
14537 operations to volatile objects.
14540 <p><b>Footnotes</b>
14541 <p><small><a name="note254" href="#note254">254)</a> See ''future library directions'' (<a href="#7.31.8">7.31.8</a>).
14544 <p><small><a href="#Contents">Contents</a></small>
14545 <h4><a name="7.17.2" href="#7.17.2">7.17.2 Initialization</a></h4>
14547 <p><small><a href="#Contents">Contents</a></small>
14548 <h5><a name="7.17.2.1" href="#7.17.2.1">7.17.2.1 The ATOMIC_VAR_INIT macro</a></h5>
14550 <p><a name="7.17.2.1p1" href="#7.17.2.1p1"><small>1</small></a>
14552 #include <a href="#7.17"><stdatomic.h></a>
14553 #define ATOMIC_VAR_INIT(C value)
14555 <p><b>Description</b>
14556 <p><a name="7.17.2.1p2" href="#7.17.2.1p2"><small>2</small></a>
14557 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
14558 atomic object of a type that is initialization-compatible with value. An atomic object
14559 with automatic storage duration that is not explicitly initialized using
14560 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
14561 initialization for objects with static or thread-local storage duration is guaranteed to
14562 produce a valid state.
14563 <p><a name="7.17.2.1p3" href="#7.17.2.1p3"><small>3</small></a>
14564 Concurrent access to the variable being initialized, even via an atomic operation,
14565 constitutes a data race.
14566 <p><a name="7.17.2.1p4" href="#7.17.2.1p4"><small>4</small></a>
14569 atomic_int guide = ATOMIC_VAR_INIT(42);
14573 <p><small><a href="#Contents">Contents</a></small>
14574 <h5><a name="7.17.2.2" href="#7.17.2.2">7.17.2.2 The atomic_init generic function</a></h5>
14576 <p><a name="7.17.2.2p1" href="#7.17.2.2p1"><small>1</small></a>
14578 #include <a href="#7.17"><stdatomic.h></a>
14579 void atomic_init(volatile A *obj, C value);
14581 <p><b>Description</b>
14582 <p><a name="7.17.2.2p2" href="#7.17.2.2p2"><small>2</small></a>
14583 The atomic_init generic function initializes the atomic object pointed to by obj to
14584 the value value, while also initializing any additional state that the implementation
14585 might need to carry for the atomic object.
14586 <p><a name="7.17.2.2p3" href="#7.17.2.2p3"><small>3</small></a>
14587 Although this function initializes an atomic object, it does not avoid data races;
14588 concurrent access to the variable being initialized, even via an atomic operation,
14589 constitutes a data race.
14592 <p><a name="7.17.2.2p4" href="#7.17.2.2p4"><small>4</small></a>
14593 The atomic_init generic function returns no value.
14594 <p><a name="7.17.2.2p5" href="#7.17.2.2p5"><small>5</small></a>
14598 atomic_init(&guide, 42);
14602 <p><small><a href="#Contents">Contents</a></small>
14603 <h4><a name="7.17.3" href="#7.17.3">7.17.3 Order and consistency</a></h4>
14604 <p><a name="7.17.3p1" href="#7.17.3p1"><small>1</small></a>
14605 The enumerated type memory_order specifies the detailed regular (non-atomic)
14606 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
14607 ordering. Its enumeration constants are as follows:<sup><a href="#note255"><b>255)</b></a></sup>
14609 memory_order_relaxed
14610 memory_order_consume
14611 memory_order_acquire
14612 memory_order_release
14613 memory_order_acq_rel
14614 memory_order_seq_cst
14616 <p><a name="7.17.3p2" href="#7.17.3p2"><small>2</small></a>
14617 For memory_order_relaxed, no operation orders memory.
14618 <p><a name="7.17.3p3" href="#7.17.3p3"><small>3</small></a>
14619 For memory_order_release, memory_order_acq_rel, and
14620 memory_order_seq_cst, a store operation performs a release operation on the
14621 affected memory location.
14622 <p><a name="7.17.3p4" href="#7.17.3p4"><small>4</small></a>
14623 For memory_order_acquire, memory_order_acq_rel, and
14624 memory_order_seq_cst, a load operation performs an acquire operation on the
14625 affected memory location.
14626 <p><a name="7.17.3p5" href="#7.17.3p5"><small>5</small></a>
14627 For memory_order_consume, a load operation performs a consume operation on the
14628 affected memory location.
14629 <p><a name="7.17.3p6" href="#7.17.3p6"><small>6</small></a>
14630 There shall be a single total order S on all memory_order_seq_cst operations,
14631 consistent with the ''happens before'' order and modification orders for all affected
14632 locations, such that each memory_order_seq_cst operation B that loads a value
14633 from an atomic object M observes one of the following values:
14635 <li> the result of the last modification A of M that precedes B in S, if it exists, or
14636 <li> if A exists, the result of some modification of M in the visible sequence of side
14637 effects with respect to B that is not memory_order_seq_cst and that does not
14638 happen before A, or
14644 <li> if A does not exist, the result of some modification of M in the visible sequence of
14645 side effects with respect to B that is not memory_order_seq_cst.
14647 <p><a name="7.17.3p7" href="#7.17.3p7"><small>7</small></a>
14648 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
14649 an order that does include lock and unlock operations, since the ordering between those is already included
14650 in the ''happens before'' ordering.
14652 <p><a name="7.17.3p8" href="#7.17.3p8"><small>8</small></a>
14653 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
14654 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
14655 object be indivisible with respect to all other atomic accesses to that object.
14657 <p><a name="7.17.3p9" href="#7.17.3p9"><small>9</small></a>
14658 For an atomic operation B that reads the value of an atomic object M, if there is a
14659 memory_order_seq_cst fence X sequenced before B, then B observes either the
14660 last memory_order_seq_cst modification of M preceding X in the total order S or
14661 a later modification of M in its modification order.
14662 <p><a name="7.17.3p10" href="#7.17.3p10"><small>10</small></a>
14663 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14664 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
14665 before X and B follows X in S, then B observes either the effects of A or a later
14666 modification of M in its modification order.
14667 <p><a name="7.17.3p11" href="#7.17.3p11"><small>11</small></a>
14668 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14669 its value, if there are memory_order_seq_cst fences X and Y such that A is
14670 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
14671 either the effects of A or a later modification of M in its modification order.
14672 <p><a name="7.17.3p12" href="#7.17.3p12"><small>12</small></a>
14673 Atomic read-modify-write operations shall always read the last value (in the modification
14674 order) stored before the write associated with the read-modify-write operation.
14675 <p><a name="7.17.3p13" href="#7.17.3p13"><small>13</small></a>
14676 An atomic store shall only store a value that has been computed from constants and
14677 program input values by a finite sequence of program evaluations, such that each
14678 evaluation observes the values of variables as computed by the last prior assignment in
14679 the sequence.<sup><a href="#note256"><b>256)</b></a></sup> The ordering of evaluations in this sequence shall be such that
14681 <li> If an evaluation B observes a value computed by A in a different thread, then B does
14682 not happen before A.
14683 <li> If an evaluation A is included in the sequence, then all evaluations that assign to the
14684 same variable and happen before A are also included.
14686 <p><a name="7.17.3p14" href="#7.17.3p14"><small>14</small></a>
14687 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
14688 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
14689 sequence out of thread order. For example, with x and y initially zero,
14697 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14698 atomic_store_explicit(&x, r1, memory_order_relaxed);
14703 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14704 atomic_store_explicit(&y, 42, memory_order_relaxed);
14706 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
14708 atomic_store_explicit(&y, 42, memory_order_relaxed);
14709 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14710 atomic_store_explicit(&x, r1, memory_order_relaxed);
14711 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14716 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14717 atomic_store_explicit(&x, r1, memory_order_relaxed);
14722 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14723 atomic_store_explicit(&y, r2, memory_order_relaxed);
14725 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
14726 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
14727 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
14729 <p><b>Recommended practice</b>
14730 <p><a name="7.17.3p15" href="#7.17.3p15"><small>15</small></a>
14731 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
14732 with x and y initially zero:
14735 r1 = atomic_load_explicit(&x, memory_order_relaxed);
14737 atomic_store_explicit(&y, r1, memory_order_relaxed);
14742 r2 = atomic_load_explicit(&y, memory_order_relaxed);
14744 atomic_store_explicit(&x, 42, memory_order_relaxed);
14746 However, this is not useful behavior, and implementations should not allow it.
14747 <p><a name="7.17.3p16" href="#7.17.3p16"><small>16</small></a>
14748 Implementations should make atomic stores visible to atomic loads within a reasonable
14752 <p><b>Footnotes</b>
14753 <p><small><a name="note255" href="#note255">255)</a> See ''future library directions'' (<a href="#7.31.8">7.31.8</a>).
14755 <p><small><a name="note256" href="#note256">256)</a> Among other implications, atomic variables shall not decay.
14758 <p><small><a href="#Contents">Contents</a></small>
14759 <h5><a name="7.17.3.1" href="#7.17.3.1">7.17.3.1 The kill_dependency macro</a></h5>
14761 <p><a name="7.17.3.1p1" href="#7.17.3.1p1"><small>1</small></a>
14763 #include <a href="#7.17"><stdatomic.h></a>
14764 type kill_dependency(type y);
14766 <p><b>Description</b>
14767 <p><a name="7.17.3.1p2" href="#7.17.3.1p2"><small>2</small></a>
14768 The kill_dependency macro terminates a dependency chain; the argument does not
14769 carry a dependency to the return value.
14771 <p><a name="7.17.3.1p3" href="#7.17.3.1p3"><small>3</small></a>
14772 The kill_dependency macro returns the value of y.
14774 <p><small><a href="#Contents">Contents</a></small>
14775 <h4><a name="7.17.4" href="#7.17.4">7.17.4 Fences</a></h4>
14776 <p><a name="7.17.4p1" href="#7.17.4p1"><small>1</small></a>
14777 This subclause introduces synchronization primitives called fences. Fences can have
14778 acquire semantics, release semantics, or both. A fence with acquire semantics is called
14779 an acquire fence; a fence with release semantics is called a release fence.
14780 <p><a name="7.17.4p2" href="#7.17.4p2"><small>2</small></a>
14781 A release fence A synchronizes with an acquire fence B if there exist atomic operations
14782 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
14783 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
14784 written by any side effect in the hypothetical release sequence X would head if it were a
14786 <p><a name="7.17.4p3" href="#7.17.4p3"><small>3</small></a>
14787 A release fence A synchronizes with an atomic operation B that performs an acquire
14788 operation on an atomic object M if there exists an atomic operation X such that A is
14789 sequenced before X, X modifies M, and B reads the value written by X or a value written
14790 by any side effect in the hypothetical release sequence X would head if it were a release
14792 <p><a name="7.17.4p4" href="#7.17.4p4"><small>4</small></a>
14793 An atomic operation A that is a release operation on an atomic object M synchronizes
14794 with an acquire fence B if there exists some atomic operation X on M such that X is
14795 sequenced before B and reads the value written by A or a value written by any side effect
14796 in the release sequence headed by A.
14798 <p><small><a href="#Contents">Contents</a></small>
14799 <h5><a name="7.17.4.1" href="#7.17.4.1">7.17.4.1 The atomic_thread_fence function</a></h5>
14801 <p><a name="7.17.4.1p1" href="#7.17.4.1p1"><small>1</small></a>
14803 #include <a href="#7.17"><stdatomic.h></a>
14804 void atomic_thread_fence(memory_order order);
14806 <p><b>Description</b>
14807 <p><a name="7.17.4.1p2" href="#7.17.4.1p2"><small>2</small></a>
14808 Depending on the value of order, this operation:
14810 <li> has no effects, if order == memory_order_relaxed;
14812 <li> is an acquire fence, if order == memory_order_acquire or order ==
14813 memory_order_consume;
14814 <li> is a release fence, if order == memory_order_release;
14815 <li> is both an acquire fence and a release fence, if order ==
14816 memory_order_acq_rel;
14817 <li> is a sequentially consistent acquire and release fence, if order ==
14818 memory_order_seq_cst.
14821 <p><a name="7.17.4.1p3" href="#7.17.4.1p3"><small>3</small></a>
14822 The atomic_thread_fence function returns no value.
14824 <p><small><a href="#Contents">Contents</a></small>
14825 <h5><a name="7.17.4.2" href="#7.17.4.2">7.17.4.2 The atomic_signal_fence function</a></h5>
14827 <p><a name="7.17.4.2p1" href="#7.17.4.2p1"><small>1</small></a>
14829 #include <a href="#7.17"><stdatomic.h></a>
14830 void atomic_signal_fence(memory_order order);
14832 <p><b>Description</b>
14833 <p><a name="7.17.4.2p2" href="#7.17.4.2p2"><small>2</small></a>
14834 Equivalent to atomic_thread_fence(order), except that the resulting ordering
14835 constraints are established only between a thread and a signal handler executed in the
14837 <p><a name="7.17.4.2p3" href="#7.17.4.2p3"><small>3</small></a>
14838 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
14839 performed by the thread become visible to the signal handler.
14841 <p><a name="7.17.4.2p4" href="#7.17.4.2p4"><small>4</small></a>
14842 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
14843 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
14844 have inserted are not emitted.
14847 <p><a name="7.17.4.2p5" href="#7.17.4.2p5"><small>5</small></a>
14848 The atomic_signal_fence function returns no value.
14850 <p><small><a href="#Contents">Contents</a></small>
14851 <h4><a name="7.17.5" href="#7.17.5">7.17.5 Lock-free property</a></h4>
14852 <p><a name="7.17.5p1" href="#7.17.5p1"><small>1</small></a>
14853 The atomic lock-free macros indicate the lock-free property of integer and address atomic
14854 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
14855 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
14856 <p><a name="7.17.5p2" href="#7.17.5p2"><small>2</small></a>
14857 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
14858 memory location via two different addresses will communicate atomically. The implementation should not
14859 depend on any per-process state. This restriction enables communication via memory mapped into a
14860 process more than once and memory shared between two processes.
14863 <p><small><a href="#Contents">Contents</a></small>
14864 <h5><a name="7.17.5.1" href="#7.17.5.1">7.17.5.1 The atomic_is_lock_free generic function</a></h5>
14866 <p><a name="7.17.5.1p1" href="#7.17.5.1p1"><small>1</small></a>
14868 #include <a href="#7.17"><stdatomic.h></a>
14869 _Bool atomic_is_lock_free(const volatile A *obj);
14871 <p><b>Description</b>
14872 <p><a name="7.17.5.1p2" href="#7.17.5.1p2"><small>2</small></a>
14873 The atomic_is_lock_free generic function indicates whether or not the object
14874 pointed to by obj is lock-free. *
14876 <p><a name="7.17.5.1p3" href="#7.17.5.1p3"><small>3</small></a>
14877 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
14878 object's operations are lock-free. The result of a lock-free query on one object cannot be
14879 inferred from the result of a lock-free query on another object.
14881 <p><small><a href="#Contents">Contents</a></small>
14882 <h4><a name="7.17.6" href="#7.17.6">7.17.6 Atomic integer types</a></h4>
14883 <p><a name="7.17.6p1" href="#7.17.6p1"><small>1</small></a>
14884 For each line in the following table,<sup><a href="#note257"><b>257)</b></a></sup> the atomic type name is declared as a type that
14885 has the same representation and alignment requirements as the corresponding direct
14886 type.<sup><a href="#note258"><b>258)</b></a></sup>
14893 Atomic type name Direct type
14894 atomic_bool _Atomic _Bool
14895 atomic_char _Atomic char
14896 atomic_schar _Atomic signed char
14897 atomic_uchar _Atomic unsigned char
14898 atomic_short _Atomic short
14899 atomic_ushort _Atomic unsigned short
14900 atomic_int _Atomic int
14901 atomic_uint _Atomic unsigned int
14902 atomic_long _Atomic long
14903 atomic_ulong _Atomic unsigned long
14904 atomic_llong _Atomic long long
14905 atomic_ullong _Atomic unsigned long long
14906 atomic_char16_t _Atomic char16_t
14907 atomic_char32_t _Atomic char32_t
14908 atomic_wchar_t _Atomic wchar_t
14909 atomic_int_least8_t _Atomic int_least8_t
14910 atomic_uint_least8_t _Atomic uint_least8_t
14911 atomic_int_least16_t _Atomic int_least16_t
14912 atomic_uint_least16_t _Atomic uint_least16_t
14913 atomic_int_least32_t _Atomic int_least32_t
14914 atomic_uint_least32_t _Atomic uint_least32_t
14915 atomic_int_least64_t _Atomic int_least64_t
14916 atomic_uint_least64_t _Atomic uint_least64_t
14917 atomic_int_fast8_t _Atomic int_fast8_t
14918 atomic_uint_fast8_t _Atomic uint_fast8_t
14919 atomic_int_fast16_t _Atomic int_fast16_t
14920 atomic_uint_fast16_t _Atomic uint_fast16_t
14921 atomic_int_fast32_t _Atomic int_fast32_t
14922 atomic_uint_fast32_t _Atomic uint_fast32_t
14923 atomic_int_fast64_t _Atomic int_fast64_t
14924 atomic_uint_fast64_t _Atomic uint_fast64_t
14925 atomic_intptr_t _Atomic intptr_t
14926 atomic_uintptr_t _Atomic uintptr_t
14927 atomic_size_t _Atomic size_t
14928 atomic_ptrdiff_t _Atomic ptrdiff_t
14929 atomic_intmax_t _Atomic intmax_t
14930 atomic_uintmax_t _Atomic uintmax_t
14932 <p><a name="7.17.6p2" href="#7.17.6p2"><small>2</small></a>
14933 The semantics of the operations on these types are defined in <a href="#7.17.7">7.17.7</a>. *
14935 <p><a name="7.17.6p3" href="#7.17.6p3"><small>3</small></a>
14936 NOTE The representation of atomic integer types need not have the same size as their corresponding
14937 regular types. They should have the same size whenever possible, as it eases effort required to port existing
14941 <p><b>Footnotes</b>
14942 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.31.8">7.31.8</a>).
14944 <p><small><a name="note258" href="#note258">258)</a> The same representation and alignment requirements are meant to imply interchangeability as
14945 arguments to functions, return values from functions, and members of unions.
14948 <p><small><a href="#Contents">Contents</a></small>
14949 <h4><a name="7.17.7" href="#7.17.7">7.17.7 Operations on atomic types</a></h4>
14950 <p><a name="7.17.7p1" href="#7.17.7p1"><small>1</small></a>
14951 There are only a few kinds of operations on atomic types, though there are many
14952 instances of those kinds. This subclause specifies each general kind.
14954 <p><small><a href="#Contents">Contents</a></small>
14955 <h5><a name="7.17.7.1" href="#7.17.7.1">7.17.7.1 The atomic_store generic functions</a></h5>
14957 <p><a name="7.17.7.1p1" href="#7.17.7.1p1"><small>1</small></a>
14959 #include <a href="#7.17"><stdatomic.h></a>
14960 void atomic_store(volatile A *object, C desired);
14961 void atomic_store_explicit(volatile A *object,
14962 C desired, memory_order order);
14964 <p><b>Description</b>
14965 <p><a name="7.17.7.1p2" href="#7.17.7.1p2"><small>2</small></a>
14966 The order argument shall not be memory_order_acquire,
14967 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
14968 value pointed to by object with the value of desired. Memory is affected according
14969 to the value of order.
14971 <p><a name="7.17.7.1p3" href="#7.17.7.1p3"><small>3</small></a>
14972 The atomic_store generic functions return no value.
14974 <p><small><a href="#Contents">Contents</a></small>
14975 <h5><a name="7.17.7.2" href="#7.17.7.2">7.17.7.2 The atomic_load generic functions</a></h5>
14977 <p><a name="7.17.7.2p1" href="#7.17.7.2p1"><small>1</small></a>
14979 #include <a href="#7.17"><stdatomic.h></a>
14980 C atomic_load(volatile A *object);
14981 C atomic_load_explicit(volatile A *object,
14982 memory_order order);
14984 <p><b>Description</b>
14985 <p><a name="7.17.7.2p2" href="#7.17.7.2p2"><small>2</small></a>
14986 The order argument shall not be memory_order_release nor
14987 memory_order_acq_rel. Memory is affected according to the value of order.
14989 Atomically returns the value pointed to by object.
14992 <p><small><a href="#Contents">Contents</a></small>
14993 <h5><a name="7.17.7.3" href="#7.17.7.3">7.17.7.3 The atomic_exchange generic functions</a></h5>
14995 <p><a name="7.17.7.3p1" href="#7.17.7.3p1"><small>1</small></a>
14997 #include <a href="#7.17"><stdatomic.h></a>
14998 C atomic_exchange(volatile A *object, C desired);
14999 C atomic_exchange_explicit(volatile A *object,
15000 C desired, memory_order order);
15002 <p><b>Description</b>
15003 <p><a name="7.17.7.3p2" href="#7.17.7.3p2"><small>2</small></a>
15004 Atomically replace the value pointed to by object with desired. Memory is affected
15005 according to the value of order. These operations are read-modify-write operations
15006 (<a href="#5.1.2.4">5.1.2.4</a>).
15008 <p><a name="7.17.7.3p3" href="#7.17.7.3p3"><small>3</small></a>
15009 Atomically returns the value pointed to by object immediately before the effects.
15011 <p><small><a href="#Contents">Contents</a></small>
15012 <h5><a name="7.17.7.4" href="#7.17.7.4">7.17.7.4 The atomic_compare_exchange generic functions</a></h5>
15014 <p><a name="7.17.7.4p1" href="#7.17.7.4p1"><small>1</small></a>
15016 #include <a href="#7.17"><stdatomic.h></a>
15017 _Bool atomic_compare_exchange_strong(volatile A *object,
15018 C *expected, C desired);
15019 _Bool atomic_compare_exchange_strong_explicit(
15020 volatile A *object, C *expected, C desired,
15021 memory_order success, memory_order failure);
15022 _Bool atomic_compare_exchange_weak(volatile A *object,
15023 C *expected, C desired);
15024 _Bool atomic_compare_exchange_weak_explicit(
15025 volatile A *object, C *expected, C desired,
15026 memory_order success, memory_order failure);
15028 <p><b>Description</b>
15029 <p><a name="7.17.7.4p2" href="#7.17.7.4p2"><small>2</small></a>
15030 The failure argument shall not be memory_order_release nor
15031 memory_order_acq_rel. The failure argument shall be no stronger than the
15032 success argument. Atomically, compares the value pointed to by object for equality
15033 with that in expected, and if true, replaces the value pointed to by object with
15034 desired, and if false, updates the value in expected with the value pointed to by
15035 object. Further, if the comparison is true, memory is affected according to the value of
15036 success, and if the comparison is false, memory is affected according to the value of
15037 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
15038 <p><a name="7.17.7.4p3" href="#7.17.7.4p3"><small>3</small></a>
15039 NOTE 1 For example, the effect of atomic_compare_exchange_strong is
15042 if (memcmp(object, expected, sizeof (*object)) == 0)
15043 memcpy(object, &desired, sizeof (*object));
15045 memcpy(expected, object, sizeof (*object));
15048 <p><a name="7.17.7.4p4" href="#7.17.7.4p4"><small>4</small></a>
15049 A weak compare-and-exchange operation may fail spuriously. That is, even when the
15050 contents of memory referred to by expected and object are equal, it may return zero
15051 and store back to expected the same memory contents that were originally there.
15052 <p><a name="7.17.7.4p5" href="#7.17.7.4p5"><small>5</small></a>
15053 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
15054 machines, e.g. load-locked store-conditional machines.
15056 <p><a name="7.17.7.4p6" href="#7.17.7.4p6"><small>6</small></a>
15057 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
15060 exp = atomic_load(&cur);
15062 des = function(exp);
15063 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
15065 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
15066 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
15067 strong one is preferable.
15070 <p><a name="7.17.7.4p7" href="#7.17.7.4p7"><small>7</small></a>
15071 The result of the comparison.
15073 <p><small><a href="#Contents">Contents</a></small>
15074 <h5><a name="7.17.7.5" href="#7.17.7.5">7.17.7.5 The atomic_fetch and modify generic functions</a></h5>
15075 <p><a name="7.17.7.5p1" href="#7.17.7.5p1"><small>1</small></a>
15076 The following operations perform arithmetic and bitwise computations. All of these
15077 operations are applicable to an object of any atomic integer type. None of these *
15078 operations is applicable to atomic_bool. The key, operator, and computation
15083 or | bitwise inclusive or
15084 xor ^ bitwise exclusive or
15085 and & bitwise and
15087 <p><a name="7.17.7.5p2" href="#7.17.7.5p2"><small>2</small></a>
15089 #include <a href="#7.17"><stdatomic.h></a>
15090 C atomic_fetch_key(volatile A *object, M operand);
15091 C atomic_fetch_key_explicit(volatile A *object,
15092 M operand, memory_order order);
15094 <p><b>Description</b>
15095 <p><a name="7.17.7.5p3" href="#7.17.7.5p3"><small>3</small></a>
15096 Atomically replaces the value pointed to by object with the result of the computation
15097 applied to the value pointed to by object and the given operand. Memory is affected
15099 according to the value of order. These operations are atomic read-modify-write
15100 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's
15101 complement representation with silent wrap-around on overflow; there are no undefined
15102 results. For address types, the result may be an undefined address, but the operations
15103 otherwise have no undefined behavior.
15105 <p><a name="7.17.7.5p4" href="#7.17.7.5p4"><small>4</small></a>
15106 Atomically, the value pointed to by object immediately before the effects.
15107 <p><a name="7.17.7.5p5" href="#7.17.7.5p5"><small>5</small></a>
15108 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
15109 operation of the corresponding op= compound assignment operators. The only differences are that the
15110 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
15111 compound assignment operator is the updated value of the object, whereas the value returned by the
15112 atomic_fetch and modify generic functions is the previous value of the atomic object.
15115 <p><small><a href="#Contents">Contents</a></small>
15116 <h4><a name="7.17.8" href="#7.17.8">7.17.8 Atomic flag type and operations</a></h4>
15117 <p><a name="7.17.8p1" href="#7.17.8p1"><small>1</small></a>
15118 The atomic_flag type provides the classic test-and-set functionality. It has two
15119 states, set and clear.
15120 <p><a name="7.17.8p2" href="#7.17.8p2"><small>2</small></a>
15121 Operations on an object of type atomic_flag shall be lock free.
15122 <p><a name="7.17.8p3" href="#7.17.8p3"><small>3</small></a>
15123 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
15124 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
15125 International standard. The remaining types can be emulated with atomic_flag, though with less than
15128 <p><a name="7.17.8p4" href="#7.17.8p4"><small>4</small></a>
15129 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
15130 clear state. An atomic_flag that is not explicitly initialized with
15131 ATOMIC_FLAG_INIT is initially in an indeterminate state.
15132 <p><a name="7.17.8p5" href="#7.17.8p5"><small>5</small></a>
15135 atomic_flag guard = ATOMIC_FLAG_INIT;
15139 <p><small><a href="#Contents">Contents</a></small>
15140 <h5><a name="7.17.8.1" href="#7.17.8.1">7.17.8.1 The atomic_flag_test_and_set functions</a></h5>
15142 <p><a name="7.17.8.1p1" href="#7.17.8.1p1"><small>1</small></a>
15144 #include <a href="#7.17"><stdatomic.h></a>
15145 _Bool atomic_flag_test_and_set(
15146 volatile atomic_flag *object);
15147 _Bool atomic_flag_test_and_set_explicit(
15148 volatile atomic_flag *object, memory_order order);
15150 <p><b>Description</b>
15151 <p><a name="7.17.8.1p2" href="#7.17.8.1p2"><small>2</small></a>
15152 Atomically sets the value pointed to by object to true. Memory is affected according
15153 to the value of order. These operations are atomic read-modify-write operations
15154 (<a href="#5.1.2.4">5.1.2.4</a>).
15157 <p><a name="7.17.8.1p3" href="#7.17.8.1p3"><small>3</small></a>
15158 Atomically, the value of the object immediately before the effects.
15160 <p><small><a href="#Contents">Contents</a></small>
15161 <h5><a name="7.17.8.2" href="#7.17.8.2">7.17.8.2 The atomic_flag_clear functions</a></h5>
15163 <p><a name="7.17.8.2p1" href="#7.17.8.2p1"><small>1</small></a>
15165 #include <a href="#7.17"><stdatomic.h></a>
15166 void atomic_flag_clear(volatile atomic_flag *object);
15167 void atomic_flag_clear_explicit(
15168 volatile atomic_flag *object, memory_order order);
15170 <p><b>Description</b>
15171 <p><a name="7.17.8.2p2" href="#7.17.8.2p2"><small>2</small></a>
15172 The order argument shall not be memory_order_acquire nor
15173 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
15174 Memory is affected according to the value of order.
15176 <p><a name="7.17.8.2p3" href="#7.17.8.2p3"><small>3</small></a>
15177 The atomic_flag_clear functions return no value.
15180 <p><small><a href="#Contents">Contents</a></small>
15181 <h3><a name="7.18" href="#7.18">7.18 Boolean type and values <stdbool.h></a></h3>
15182 <p><a name="7.18p1" href="#7.18p1"><small>1</small></a>
15183 The header <a href="#7.18"><stdbool.h></a> defines four macros.
15184 <p><a name="7.18p2" href="#7.18p2"><small>2</small></a>
15190 <p><a name="7.18p3" href="#7.18p3"><small>3</small></a>
15191 The remaining three macros are suitable for use in #if preprocessing directives. They
15196 which expands to the integer constant 1,
15200 which expands to the integer constant 0, and
15202 __bool_true_false_are_defined
15204 which expands to the integer constant 1.
15205 <p><a name="7.18p4" href="#7.18p4"><small>4</small></a>
15206 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
15207 redefine the macros bool, true, and false.<sup><a href="#note259"><b>259)</b></a></sup>
15214 <p><b>Footnotes</b>
15215 <p><small><a name="note259" href="#note259">259)</a> See ''future library directions'' (<a href="#7.31.9">7.31.9</a>).
15218 <p><small><a href="#Contents">Contents</a></small>
15219 <h3><a name="7.19" href="#7.19">7.19 Common definitions <stddef.h></a></h3>
15220 <p><a name="7.19p1" href="#7.19p1"><small>1</small></a>
15221 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
15222 Some are also defined in other headers, as noted in their respective subclauses.
15223 <p><a name="7.19p2" href="#7.19p2"><small>2</small></a>
15228 which is the signed integer type of the result of subtracting two pointers;
15232 which is the unsigned integer type of the result of the sizeof operator;
15236 which is an object type whose alignment is as great as is supported by the implementation
15237 in all contexts; and
15241 which is an integer type whose range of values can represent distinct codes for all
15242 members of the largest extended character set specified among the supported locales; the
15243 null character shall have the code value zero. Each member of the basic character set
15244 shall have a code value equal to its value when used as the lone character in an integer
15245 character constant if an implementation does not define
15246 __STDC_MB_MIGHT_NEQ_WC__.
15247 <p><a name="7.19p3" href="#7.19p3"><small>3</small></a>
15252 which expands to an implementation-defined null pointer constant; and
15254 offsetof(type, member-designator)
15256 which expands to an integer constant expression that has type size_t, the value of
15257 which is the offset in bytes, to the structure member (designated by member-designator),
15258 from the beginning of its structure (designated by type). The type and member designator
15259 shall be such that given
15263 then the expression &(t.member-designator) evaluates to an address constant. (If the
15264 specified member is a bit-field, the behavior is undefined.)
15265 <p><b>Recommended practice</b>
15266 <p><a name="7.19p4" href="#7.19p4"><small>4</small></a>
15267 The types used for size_t and ptrdiff_t should not have an integer conversion rank
15268 greater than that of signed long int unless the implementation supports objects
15269 large enough to make this necessary. *
15272 <p><small><a href="#Contents">Contents</a></small>
15273 <h3><a name="7.20" href="#7.20">7.20 Integer types <stdint.h></a></h3>
15274 <p><a name="7.20p1" href="#7.20p1"><small>1</small></a>
15275 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
15276 defines corresponding sets of macros.<sup><a href="#note260"><b>260)</b></a></sup> It also defines macros that specify limits of
15277 integer types corresponding to types defined in other standard headers.
15278 <p><a name="7.20p2" href="#7.20p2"><small>2</small></a>
15279 Types are defined in the following categories:
15281 <li> integer types having certain exact widths;
15282 <li> integer types having at least certain specified widths;
15283 <li> fastest integer types having at least certain specified widths;
15284 <li> integer types wide enough to hold pointers to objects;
15285 <li> integer types having greatest width.
15287 (Some of these types may denote the same type.)
15288 <p><a name="7.20p3" href="#7.20p3"><small>3</small></a>
15289 Corresponding macros specify limits of the declared types and construct suitable
15291 <p><a name="7.20p4" href="#7.20p4"><small>4</small></a>
15292 For each type described herein that the implementation provides,<sup><a href="#note261"><b>261)</b></a></sup> <a href="#7.20"><stdint.h></a> shall
15293 declare that typedef name and define the associated macros. Conversely, for each type
15294 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
15295 declare that typedef name nor shall it define the associated macros. An implementation
15296 shall provide those types described as ''required'', but need not provide any of the others
15297 (described as ''optional'').
15299 <p><b>Footnotes</b>
15300 <p><small><a name="note260" href="#note260">260)</a> See ''future library directions'' (<a href="#7.31.10">7.31.10</a>).
15302 <p><small><a name="note261" href="#note261">261)</a> Some of these types may denote implementation-defined extended integer types.
15305 <p><small><a href="#Contents">Contents</a></small>
15306 <h4><a name="7.20.1" href="#7.20.1">7.20.1 Integer types</a></h4>
15307 <p><a name="7.20.1p1" href="#7.20.1p1"><small>1</small></a>
15308 When typedef names differing only in the absence or presence of the initial u are defined,
15309 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
15310 implementation providing one of these corresponding types shall also provide the other.
15311 <p><a name="7.20.1p2" href="#7.20.1p2"><small>2</small></a>
15312 In the following descriptions, the symbol N represents an unsigned decimal integer with
15313 no leading zeros (e.g., 8 or 24, but not 04 or 048).
15320 <p><small><a href="#Contents">Contents</a></small>
15321 <h5><a name="7.20.1.1" href="#7.20.1.1">7.20.1.1 Exact-width integer types</a></h5>
15322 <p><a name="7.20.1.1p1" href="#7.20.1.1p1"><small>1</small></a>
15323 The typedef name intN_t designates a signed integer type with width N , no padding
15324 bits, and a two's complement representation. Thus, int8_t denotes such a signed
15325 integer type with a width of exactly 8 bits.
15326 <p><a name="7.20.1.1p2" href="#7.20.1.1p2"><small>2</small></a>
15327 The typedef name uintN_t designates an unsigned integer type with width N and no
15328 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
15330 <p><a name="7.20.1.1p3" href="#7.20.1.1p3"><small>3</small></a>
15331 These types are optional. However, if an implementation provides integer types with
15332 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
15333 two's complement representation, it shall define the corresponding typedef names.
15335 <p><small><a href="#Contents">Contents</a></small>
15336 <h5><a name="7.20.1.2" href="#7.20.1.2">7.20.1.2 Minimum-width integer types</a></h5>
15337 <p><a name="7.20.1.2p1" href="#7.20.1.2p1"><small>1</small></a>
15338 The typedef name int_leastN_t designates a signed integer type with a width of at
15339 least N , such that no signed integer type with lesser size has at least the specified width.
15340 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
15341 <p><a name="7.20.1.2p2" href="#7.20.1.2p2"><small>2</small></a>
15342 The typedef name uint_leastN_t designates an unsigned integer type with a width
15343 of at least N , such that no unsigned integer type with lesser size has at least the specified
15344 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
15346 <p><a name="7.20.1.2p3" href="#7.20.1.2p3"><small>3</small></a>
15347 The following types are required:
15349 int_least8_t uint_least8_t
15350 int_least16_t uint_least16_t
15351 int_least32_t uint_least32_t
15352 int_least64_t uint_least64_t
15354 All other types of this form are optional.
15356 <p><small><a href="#Contents">Contents</a></small>
15357 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 Fastest minimum-width integer types</a></h5>
15358 <p><a name="7.20.1.3p1" href="#7.20.1.3p1"><small>1</small></a>
15359 Each of the following types designates an integer type that is usually fastest<sup><a href="#note262"><b>262)</b></a></sup> to operate
15360 with among all integer types that have at least the specified width.
15361 <p><a name="7.20.1.3p2" href="#7.20.1.3p2"><small>2</small></a>
15362 The typedef name int_fastN_t designates the fastest signed integer type with a width
15363 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
15364 type with a width of at least N .
15370 <p><a name="7.20.1.3p3" href="#7.20.1.3p3"><small>3</small></a>
15371 The following types are required:
15373 int_fast8_t uint_fast8_t
15374 int_fast16_t uint_fast16_t
15375 int_fast32_t uint_fast32_t
15376 int_fast64_t uint_fast64_t
15378 All other types of this form are optional.
15380 <p><b>Footnotes</b>
15381 <p><small><a name="note262" href="#note262">262)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
15382 grounds for choosing one type over another, it will simply pick some integer type satisfying the
15383 signedness and width requirements.
15386 <p><small><a href="#Contents">Contents</a></small>
15387 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 Integer types capable of holding object pointers</a></h5>
15388 <p><a name="7.20.1.4p1" href="#7.20.1.4p1"><small>1</small></a>
15389 The following type designates a signed integer type with the property that any valid
15390 pointer to void can be converted to this type, then converted back to pointer to void,
15391 and the result will compare equal to the original pointer:
15395 The following type designates an unsigned integer type with the property that any valid
15396 pointer to void can be converted to this type, then converted back to pointer to void,
15397 and the result will compare equal to the original pointer:
15401 These types are optional.
15403 <p><small><a href="#Contents">Contents</a></small>
15404 <h5><a name="7.20.1.5" href="#7.20.1.5">7.20.1.5 Greatest-width integer types</a></h5>
15405 <p><a name="7.20.1.5p1" href="#7.20.1.5p1"><small>1</small></a>
15406 The following type designates a signed integer type capable of representing any value of
15407 any signed integer type:
15411 The following type designates an unsigned integer type capable of representing any value
15412 of any unsigned integer type:
15416 These types are required.
15418 <p><small><a href="#Contents">Contents</a></small>
15419 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Limits of specified-width integer types</a></h4>
15420 <p><a name="7.20.2p1" href="#7.20.2p1"><small>1</small></a>
15421 The following object-like macros specify the minimum and maximum limits of the types
15422 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
15423 <a href="#7.20.1">7.20.1</a>.
15424 <p><a name="7.20.2p2" href="#7.20.2p2"><small>2</small></a>
15425 Each instance of any defined macro shall be replaced by a constant expression suitable
15426 for use in #if preprocessing directives, and this expression shall have the same type as
15427 would an expression that is an object of the corresponding type converted according to
15428 the integer promotions. Its implementation-defined value shall be equal to or greater in
15429 magnitude (absolute value) than the corresponding value given below, with the same sign,
15430 except where stated to be exactly the given value.
15433 <p><small><a href="#Contents">Contents</a></small>
15434 <h5><a name="7.20.2.1" href="#7.20.2.1">7.20.2.1 Limits of exact-width integer types</a></h5>
15435 <p><a name="7.20.2.1p1" href="#7.20.2.1p1"><small>1</small></a>
15437 <li> minimum values of exact-width signed integer types
15439 INTN_MIN exactly -(2 N -1 )
15441 <li> maximum values of exact-width signed integer types
15443 INTN_MAX exactly 2 N -1 - 1
15445 <li> maximum values of exact-width unsigned integer types
15446 UINTN_MAX exactly 2 N - 1
15449 <p><small><a href="#Contents">Contents</a></small>
15450 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 Limits of minimum-width integer types</a></h5>
15451 <p><a name="7.20.2.2p1" href="#7.20.2.2p1"><small>1</small></a>
15453 <li> minimum values of minimum-width signed integer types
15455 INT_LEASTN_MIN -(2 N -1 - 1)
15457 <li> maximum values of minimum-width signed integer types
15459 INT_LEASTN_MAX 2 N -1 - 1
15461 <li> maximum values of minimum-width unsigned integer types
15462 UINT_LEASTN_MAX 2N - 1
15465 <p><small><a href="#Contents">Contents</a></small>
15466 <h5><a name="7.20.2.3" href="#7.20.2.3">7.20.2.3 Limits of fastest minimum-width integer types</a></h5>
15467 <p><a name="7.20.2.3p1" href="#7.20.2.3p1"><small>1</small></a>
15469 <li> minimum values of fastest minimum-width signed integer types
15471 INT_FASTN_MIN -(2 N -1 - 1)
15473 <li> maximum values of fastest minimum-width signed integer types
15474 INT_FASTN_MAX 2 N -1 - 1
15475 <li> maximum values of fastest minimum-width unsigned integer types
15476 UINT_FASTN_MAX 2N - 1
15479 <p><small><a href="#Contents">Contents</a></small>
15480 <h5><a name="7.20.2.4" href="#7.20.2.4">7.20.2.4 Limits of integer types capable of holding object pointers</a></h5>
15481 <p><a name="7.20.2.4p1" href="#7.20.2.4p1"><small>1</small></a>
15483 <li> minimum value of pointer-holding signed integer type
15485 INTPTR_MIN -(215 - 1)
15487 <li> maximum value of pointer-holding signed integer type
15489 <li> maximum value of pointer-holding unsigned integer type
15490 UINTPTR_MAX 216 - 1
15494 <p><small><a href="#Contents">Contents</a></small>
15495 <h5><a name="7.20.2.5" href="#7.20.2.5">7.20.2.5 Limits of greatest-width integer types</a></h5>
15496 <p><a name="7.20.2.5p1" href="#7.20.2.5p1"><small>1</small></a>
15498 <li> minimum value of greatest-width signed integer type
15499 INTMAX_MIN -(263 - 1)
15500 <li> maximum value of greatest-width signed integer type
15502 <li> maximum value of greatest-width unsigned integer type
15503 UINTMAX_MAX 264 - 1
15506 <p><small><a href="#Contents">Contents</a></small>
15507 <h4><a name="7.20.3" href="#7.20.3">7.20.3 Limits of other integer types</a></h4>
15508 <p><a name="7.20.3p1" href="#7.20.3p1"><small>1</small></a>
15509 The following object-like macros specify the minimum and maximum limits of integer
15510 types corresponding to types defined in other standard headers.
15511 <p><a name="7.20.3p2" href="#7.20.3p2"><small>2</small></a>
15512 Each instance of these macros shall be replaced by a constant expression suitable for use
15513 in #if preprocessing directives, and this expression shall have the same type as would an
15514 expression that is an object of the corresponding type converted according to the integer
15515 promotions. Its implementation-defined value shall be equal to or greater in magnitude
15516 (absolute value) than the corresponding value given below, with the same sign. An
15517 implementation shall define only the macros corresponding to those typedef names it
15518 actually provides.<sup><a href="#note263"><b>263)</b></a></sup>
15520 <li> limits of ptrdiff_t
15523 <li> limits of sig_atomic_t
15524 SIG_ATOMIC_MIN see below
15525 SIG_ATOMIC_MAX see below
15526 <li> limit of size_t
15528 <li> limits of wchar_t
15529 WCHAR_MIN see below
15530 WCHAR_MAX see below
15531 <li> limits of wint_t
15540 <p><a name="7.20.3p3" href="#7.20.3p3"><small>3</small></a>
15541 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
15542 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
15543 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
15544 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
15545 SIG_ATOMIC_MAX shall be no less than 255.
15546 <p><a name="7.20.3p4" href="#7.20.3p4"><small>4</small></a>
15547 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
15548 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
15549 otherwise, wchar_t is defined as an unsigned integer type, and the value of
15550 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note264"><b>264)</b></a></sup>
15551 <p><a name="7.20.3p5" href="#7.20.3p5"><small>5</small></a>
15552 If wint_t (see <a href="#7.29">7.29</a>) is defined as a signed integer type, the value of WINT_MIN shall
15553 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
15554 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
15555 shall be 0 and the value of WINT_MAX shall be no less than 65535.
15557 <p><b>Footnotes</b>
15558 <p><small><a name="note263" href="#note263">263)</a> A freestanding implementation need not provide all of these types.
15560 <p><small><a name="note264" href="#note264">264)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
15564 <p><small><a href="#Contents">Contents</a></small>
15565 <h4><a name="7.20.4" href="#7.20.4">7.20.4 Macros for integer constants</a></h4>
15566 <p><a name="7.20.4p1" href="#7.20.4p1"><small>1</small></a>
15567 The following function-like macros expand to integer constants suitable for initializing
15568 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
15569 macro name corresponds to a similar type name in <a href="#7.20.1.2">7.20.1.2</a> or <a href="#7.20.1.5">7.20.1.5</a>.
15570 <p><a name="7.20.4p2" href="#7.20.4p2"><small>2</small></a>
15571 The argument in any instance of these macros shall be an unsuffixed integer constant (as
15572 defined in <a href="#6.4.4.1">6.4.4.1</a>) with a value that does not exceed the limits for the corresponding type.
15573 <p><a name="7.20.4p3" href="#7.20.4p3"><small>3</small></a>
15574 Each invocation of one of these macros shall expand to an integer constant expression
15575 suitable for use in #if preprocessing directives. The type of the expression shall have
15576 the same type as would an expression of the corresponding type converted according to
15577 the integer promotions. The value of the expression shall be that of the argument.
15579 <p><small><a href="#Contents">Contents</a></small>
15580 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 Macros for minimum-width integer constants</a></h5>
15581 <p><a name="7.20.4.1p1" href="#7.20.4.1p1"><small>1</small></a>
15582 The macro INTN_C(value) shall expand to an integer constant expression
15583 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
15584 to an integer constant expression corresponding to the type uint_leastN_t. For
15585 example, if uint_least64_t is a name for the type unsigned long long int,
15586 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
15593 <p><small><a href="#Contents">Contents</a></small>
15594 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 Macros for greatest-width integer constants</a></h5>
15595 <p><a name="7.20.4.2p1" href="#7.20.4.2p1"><small>1</small></a>
15596 The following macro expands to an integer constant expression having the value specified
15597 by its argument and the type intmax_t:
15601 The following macro expands to an integer constant expression having the value specified
15602 by its argument and the type uintmax_t:
15608 <p><small><a href="#Contents">Contents</a></small>
15609 <h3><a name="7.21" href="#7.21">7.21 Input/output <stdio.h></a></h3>
15611 <p><small><a href="#Contents">Contents</a></small>
15612 <h4><a name="7.21.1" href="#7.21.1">7.21.1 Introduction</a></h4>
15613 <p><a name="7.21.1p1" href="#7.21.1p1"><small>1</small></a>
15614 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
15615 functions for performing input and output.
15616 <p><a name="7.21.1p2" href="#7.21.1p2"><small>2</small></a>
15617 The types declared are size_t (described in <a href="#7.19">7.19</a>);
15621 which is an object type capable of recording all the information needed to control a
15622 stream, including its file position indicator, a pointer to its associated buffer (if any), an
15623 error indicator that records whether a read/write error has occurred, and an end-of-file
15624 indicator that records whether the end of the file has been reached; and
15628 which is a complete object type other than an array type capable of recording all the
15629 information needed to specify uniquely every position within a file.
15630 <p><a name="7.21.1p3" href="#7.21.1p3"><small>3</small></a>
15631 The macros are NULL (described in <a href="#7.19">7.19</a>);
15637 which expand to integer constant expressions with distinct values, suitable for use as the
15638 third argument to the setvbuf function;
15642 which expands to an integer constant expression that is the size of the buffer used by the
15647 which expands to an integer constant expression, with type int and a negative value, that
15648 is returned by several functions to indicate end-of-file, that is, no more input from a
15653 which expands to an integer constant expression that is the minimum number of files that
15654 the implementation guarantees can be open simultaneously;
15658 which expands to an integer constant expression that is the size needed for an array of
15659 char large enough to hold the longest file name string that the implementation
15661 guarantees can be opened;<sup><a href="#note265"><b>265)</b></a></sup>
15665 which expands to an integer constant expression that is the size needed for an array of
15666 char large enough to hold a temporary file name string generated by the tmpnam
15673 which expand to integer constant expressions with distinct values, suitable for use as the
15674 third argument to the fseek function;
15678 which expands to an integer constant expression that is the minimum number of unique
15679 file names that can be generated by the tmpnam function;
15685 which are expressions of type ''pointer to FILE'' that point to the FILE objects
15686 associated, respectively, with the standard error, input, and output streams.
15687 <p><a name="7.21.1p4" href="#7.21.1p4"><small>4</small></a>
15688 The header <a href="#7.29"><wchar.h></a> declares a number of functions useful for wide character input
15689 and output. The wide character input/output functions described in that subclause
15690 provide operations analogous to most of those described here, except that the
15691 fundamental units internal to the program are wide characters. The external
15692 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
15693 described further in <a href="#7.21.3">7.21.3</a>.
15694 <p><a name="7.21.1p5" href="#7.21.1p5"><small>5</small></a>
15695 The input/output functions are given the following collective terms:
15697 <li> The wide character input functions -- those functions described in <a href="#7.29">7.29</a> that perform
15698 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
15699 fwscanf, wscanf, vfwscanf, and vwscanf.
15700 <li> The wide character output functions -- those functions described in <a href="#7.29">7.29</a> that perform
15701 output from wide characters and wide strings: fputwc, fputws, putwc,
15702 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
15706 <li> The wide character input/output functions -- the union of the ungetwc function, the
15707 wide character input functions, and the wide character output functions.
15708 <li> The byte input/output functions -- those functions described in this subclause that
15709 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
15710 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf,
15711 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
15713 <p><b> Forward references</b>: files (<a href="#7.21.3">7.21.3</a>), the fseek function (<a href="#7.21.9.2">7.21.9.2</a>), streams (<a href="#7.21.2">7.21.2</a>), the
15714 tmpnam function (<a href="#7.21.4.4">7.21.4.4</a>), <a href="#7.29"><wchar.h></a> (<a href="#7.29">7.29</a>).
15716 <p><b>Footnotes</b>
15717 <p><small><a name="note265" href="#note265">265)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
15718 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
15719 string. Of course, file name string contents are subject to other system-specific constraints; therefore
15720 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
15723 <p><small><a href="#Contents">Contents</a></small>
15724 <h4><a name="7.21.2" href="#7.21.2">7.21.2 Streams</a></h4>
15725 <p><a name="7.21.2p1" href="#7.21.2p1"><small>1</small></a>
15726 Input and output, whether to or from physical devices such as terminals and tape drives,
15727 or whether to or from files supported on structured storage devices, are mapped into
15728 logical data streams, whose properties are more uniform than their various inputs and
15729 outputs. Two forms of mapping are supported, for text streams and for binary
15730 streams.<sup><a href="#note266"><b>266)</b></a></sup>
15731 <p><a name="7.21.2p2" href="#7.21.2p2"><small>2</small></a>
15732 A text stream is an ordered sequence of characters composed into lines, each line
15733 consisting of zero or more characters plus a terminating new-line character. Whether the
15734 last line requires a terminating new-line character is implementation-defined. Characters
15735 may have to be added, altered, or deleted on input and output to conform to differing
15736 conventions for representing text in the host environment. Thus, there need not be a one-
15737 to-one correspondence between the characters in a stream and those in the external
15738 representation. Data read in from a text stream will necessarily compare equal to the data
15739 that were earlier written out to that stream only if: the data consist only of printing
15740 characters and the control characters horizontal tab and new-line; no new-line character is
15741 immediately preceded by space characters; and the last character is a new-line character.
15742 Whether space characters that are written out immediately before a new-line character
15743 appear when read in is implementation-defined.
15744 <p><a name="7.21.2p3" href="#7.21.2p3"><small>3</small></a>
15745 A binary stream is an ordered sequence of characters that can transparently record
15746 internal data. Data read in from a binary stream shall compare equal to the data that were
15747 earlier written out to that stream, under the same implementation. Such a stream may,
15748 however, have an implementation-defined number of null characters appended to the end
15750 <p><a name="7.21.2p4" href="#7.21.2p4"><small>4</small></a>
15751 Each stream has an orientation. After a stream is associated with an external file, but
15752 before any operations are performed on it, the stream is without orientation. Once a wide
15753 character input/output function has been applied to a stream without orientation, the
15757 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
15758 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
15759 Only a call to the freopen function or the fwide function can otherwise alter the
15760 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note267"><b>267)</b></a></sup>
15761 <p><a name="7.21.2p5" href="#7.21.2p5"><small>5</small></a>
15762 Byte input/output functions shall not be applied to a wide-oriented stream and wide
15763 character input/output functions shall not be applied to a byte-oriented stream. The
15764 remaining stream operations do not affect, and are not affected by, a stream's orientation,
15765 except for the following additional restrictions:
15767 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
15768 text and binary streams.
15769 <li> For wide-oriented streams, after a successful call to a file-positioning function that
15770 leaves the file position indicator prior to the end-of-file, a wide character output
15771 function can overwrite a partial multibyte character; any file contents beyond the
15772 byte(s) written are henceforth indeterminate.
15774 <p><a name="7.21.2p6" href="#7.21.2p6"><small>6</small></a>
15775 Each wide-oriented stream has an associated mbstate_t object that stores the current
15776 parse state of the stream. A successful call to fgetpos stores a representation of the
15777 value of this mbstate_t object as part of the value of the fpos_t object. A later
15778 successful call to fsetpos using the same stored fpos_t value restores the value of
15779 the associated mbstate_t object as well as the position within the controlled stream.
15780 <p><a name="7.21.2p7" href="#7.21.2p7"><small>7</small></a>
15781 Each stream has an associated lock that is used to prevent data races when multiple
15782 threads of execution access a stream, and to restrict the interleaving of stream operations
15783 performed by multiple threads. Only one thread may hold this lock at a time. The lock is
15784 reentrant: a single thread may hold the lock multiple times at a given time.
15785 <p><a name="7.21.2p8" href="#7.21.2p8"><small>8</small></a>
15786 All functions that read, write, position, or query the position of a stream lock the stream
15787 before accessing it. They release the lock associated with the stream when the access is
15789 <p><b>Environmental limits</b>
15790 <p><a name="7.21.2p9" href="#7.21.2p9"><small>9</small></a>
15791 An implementation shall support text files with lines containing at least 254 characters,
15792 including the terminating new-line character. The value of the macro BUFSIZ shall be at
15794 <p><b> Forward references</b>: the freopen function (<a href="#7.21.5.4">7.21.5.4</a>), the fwide function (<a href="#7.29.3.5">7.29.3.5</a>),
15795 mbstate_t (<a href="#7.30.1">7.30.1</a>), the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>), the fsetpos function
15796 (<a href="#7.21.9.3">7.21.9.3</a>).
15803 <p><b>Footnotes</b>
15804 <p><small><a name="note266" href="#note266">266)</a> An implementation need not distinguish between text streams and binary streams. In such an
15805 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
15808 <p><small><a name="note267" href="#note267">267)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
15811 <p><small><a href="#Contents">Contents</a></small>
15812 <h4><a name="7.21.3" href="#7.21.3">7.21.3 Files</a></h4>
15813 <p><a name="7.21.3p1" href="#7.21.3p1"><small>1</small></a>
15814 A stream is associated with an external file (which may be a physical device) by opening
15815 a file, which may involve creating a new file. Creating an existing file causes its former
15816 contents to be discarded, if necessary. If a file can support positioning requests (such as a
15817 disk file, as opposed to a terminal), then a file position indicator associated with the
15818 stream is positioned at the start (character number zero) of the file, unless the file is
15819 opened with append mode in which case it is implementation-defined whether the file
15820 position indicator is initially positioned at the beginning or the end of the file. The file
15821 position indicator is maintained by subsequent reads, writes, and positioning requests, to
15822 facilitate an orderly progression through the file.
15823 <p><a name="7.21.3p2" href="#7.21.3p2"><small>2</small></a>
15824 Binary files are not truncated, except as defined in <a href="#7.21.5.3">7.21.5.3</a>. Whether a write on a text
15825 stream causes the associated file to be truncated beyond that point is implementation-
15827 <p><a name="7.21.3p3" href="#7.21.3p3"><small>3</small></a>
15828 When a stream is unbuffered, characters are intended to appear from the source or at the
15829 destination as soon as possible. Otherwise characters may be accumulated and
15830 transmitted to or from the host environment as a block. When a stream is fully buffered,
15831 characters are intended to be transmitted to or from the host environment as a block when
15832 a buffer is filled. When a stream is line buffered, characters are intended to be
15833 transmitted to or from the host environment as a block when a new-line character is
15834 encountered. Furthermore, characters are intended to be transmitted as a block to the host
15835 environment when a buffer is filled, when input is requested on an unbuffered stream, or
15836 when input is requested on a line buffered stream that requires the transmission of
15837 characters from the host environment. Support for these characteristics is
15838 implementation-defined, and may be affected via the setbuf and setvbuf functions.
15839 <p><a name="7.21.3p4" href="#7.21.3p4"><small>4</small></a>
15840 A file may be disassociated from a controlling stream by closing the file. Output streams
15841 are flushed (any unwritten buffer contents are transmitted to the host environment) before
15842 the stream is disassociated from the file. The value of a pointer to a FILE object is
15843 indeterminate after the associated file is closed (including the standard text streams).
15844 Whether a file of zero length (on which no characters have been written by an output
15845 stream) actually exists is implementation-defined.
15846 <p><a name="7.21.3p5" href="#7.21.3p5"><small>5</small></a>
15847 The file may be subsequently reopened, by the same or another program execution, and
15848 its contents reclaimed or modified (if it can be repositioned at its start). If the main
15849 function returns to its original caller, or if the exit function is called, all open files are
15850 closed (hence all output streams are flushed) before program termination. Other paths to
15851 program termination, such as calling the abort function, need not close all files
15853 <p><a name="7.21.3p6" href="#7.21.3p6"><small>6</small></a>
15854 The address of the FILE object used to control a stream may be significant; a copy of a
15855 FILE object need not serve in place of the original.
15857 <p><a name="7.21.3p7" href="#7.21.3p7"><small>7</small></a>
15858 At program startup, three text streams are predefined and need not be opened explicitly
15860 <li> standard input (for reading conventional input), standard output (for writing
15862 conventional output), and standard error (for writing diagnostic output). As initially
15863 opened, the standard error stream is not fully buffered; the standard input and standard
15864 output streams are fully buffered if and only if the stream can be determined not to refer
15865 to an interactive device.
15866 <p><a name="7.21.3p8" href="#7.21.3p8"><small>8</small></a>
15867 Functions that open additional (nontemporary) files require a file name, which is a string.
15868 The rules for composing valid file names are implementation-defined. Whether the same
15869 file can be simultaneously open multiple times is also implementation-defined.
15870 <p><a name="7.21.3p9" href="#7.21.3p9"><small>9</small></a>
15871 Although both text and binary wide-oriented streams are conceptually sequences of wide
15872 characters, the external file associated with a wide-oriented stream is a sequence of
15873 multibyte characters, generalized as follows:
15875 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
15876 encodings valid for use internal to the program).
15877 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note268"><b>268)</b></a></sup>
15879 <p><a name="7.21.3p10" href="#7.21.3p10"><small>10</small></a>
15880 Moreover, the encodings used for multibyte characters may differ among files. Both the
15881 nature and choice of such encodings are implementation-defined.
15882 <p><a name="7.21.3p11" href="#7.21.3p11"><small>11</small></a>
15883 The wide character input functions read multibyte characters from the stream and convert
15884 them to wide characters as if they were read by successive calls to the fgetwc function.
15885 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
15886 described by the stream's own mbstate_t object. The byte input functions read
15887 characters from the stream as if by successive calls to the fgetc function.
15888 <p><a name="7.21.3p12" href="#7.21.3p12"><small>12</small></a>
15889 The wide character output functions convert wide characters to multibyte characters and
15890 write them to the stream as if they were written by successive calls to the fputwc
15891 function. Each conversion occurs as if by a call to the wcrtomb function, with the
15892 conversion state described by the stream's own mbstate_t object. The byte output
15893 functions write characters to the stream as if by successive calls to the fputc function.
15894 <p><a name="7.21.3p13" href="#7.21.3p13"><small>13</small></a>
15895 In some cases, some of the byte input/output functions also perform conversions between
15896 multibyte characters and wide characters. These conversions also occur as if by calls to
15897 the mbrtowc and wcrtomb functions.
15898 <p><a name="7.21.3p14" href="#7.21.3p14"><small>14</small></a>
15899 An encoding error occurs if the character sequence presented to the underlying
15900 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
15901 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
15905 multibyte character. The wide character input/output functions and the byte input/output
15906 functions store the value of the macro EILSEQ in errno if and only if an encoding error
15908 <p><b>Environmental limits</b>
15909 <p><a name="7.21.3p15" href="#7.21.3p15"><small>15</small></a>
15910 The value of FOPEN_MAX shall be at least eight, including the three standard text
15912 <p><b> Forward references</b>: the exit function (<a href="#7.22.4.4">7.22.4.4</a>), the fgetc function (<a href="#7.21.7.1">7.21.7.1</a>), the
15913 fopen function (<a href="#7.21.5.3">7.21.5.3</a>), the fputc function (<a href="#7.21.7.3">7.21.7.3</a>), the setbuf function
15914 (<a href="#7.21.5.5">7.21.5.5</a>), the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>), the fgetwc function (<a href="#7.29.3.1">7.29.3.1</a>), the
15915 fputwc function (<a href="#7.29.3.3">7.29.3.3</a>), conversion state (<a href="#7.29.6">7.29.6</a>), the mbrtowc function
15916 (<a href="#7.29.6.3.2">7.29.6.3.2</a>), the wcrtomb function (<a href="#7.29.6.3.3">7.29.6.3.3</a>).
15918 <p><b>Footnotes</b>
15919 <p><small><a name="note268" href="#note268">268)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
15920 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
15921 with state-dependent encoding that does not assuredly end in the initial shift state.
15924 <p><small><a href="#Contents">Contents</a></small>
15925 <h4><a name="7.21.4" href="#7.21.4">7.21.4 Operations on files</a></h4>
15927 <p><small><a href="#Contents">Contents</a></small>
15928 <h5><a name="7.21.4.1" href="#7.21.4.1">7.21.4.1 The remove function</a></h5>
15930 <p><a name="7.21.4.1p1" href="#7.21.4.1p1"><small>1</small></a>
15932 #include <a href="#7.21"><stdio.h></a>
15933 int remove(const char *filename);
15935 <p><b>Description</b>
15936 <p><a name="7.21.4.1p2" href="#7.21.4.1p2"><small>2</small></a>
15937 The remove function causes the file whose name is the string pointed to by filename
15938 to be no longer accessible by that name. A subsequent attempt to open that file using that
15939 name will fail, unless it is created anew. If the file is open, the behavior of the remove
15940 function is implementation-defined.
15942 <p><a name="7.21.4.1p3" href="#7.21.4.1p3"><small>3</small></a>
15943 The remove function returns zero if the operation succeeds, nonzero if it fails.
15945 <p><small><a href="#Contents">Contents</a></small>
15946 <h5><a name="7.21.4.2" href="#7.21.4.2">7.21.4.2 The rename function</a></h5>
15948 <p><a name="7.21.4.2p1" href="#7.21.4.2p1"><small>1</small></a>
15950 #include <a href="#7.21"><stdio.h></a>
15951 int rename(const char *old, const char *new);
15953 <p><b>Description</b>
15954 <p><a name="7.21.4.2p2" href="#7.21.4.2p2"><small>2</small></a>
15955 The rename function causes the file whose name is the string pointed to by old to be
15956 henceforth known by the name given by the string pointed to by new. The file named
15957 old is no longer accessible by that name. If a file named by the string pointed to by new
15958 exists prior to the call to the rename function, the behavior is implementation-defined.
15961 <p><a name="7.21.4.2p3" href="#7.21.4.2p3"><small>3</small></a>
15962 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note269"><b>269)</b></a></sup> in
15963 which case if the file existed previously it is still known by its original name.
15965 <p><b>Footnotes</b>
15966 <p><small><a name="note269" href="#note269">269)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
15967 or that it is necessary to copy its contents to effectuate its renaming.
15970 <p><small><a href="#Contents">Contents</a></small>
15971 <h5><a name="7.21.4.3" href="#7.21.4.3">7.21.4.3 The tmpfile function</a></h5>
15973 <p><a name="7.21.4.3p1" href="#7.21.4.3p1"><small>1</small></a>
15975 #include <a href="#7.21"><stdio.h></a>
15976 FILE *tmpfile(void);
15978 <p><b>Description</b>
15979 <p><a name="7.21.4.3p2" href="#7.21.4.3p2"><small>2</small></a>
15980 The tmpfile function creates a temporary binary file that is different from any other
15981 existing file and that will automatically be removed when it is closed or at program
15982 termination. If the program terminates abnormally, whether an open temporary file is
15983 removed is implementation-defined. The file is opened for update with "wb+" mode.
15984 <p><b>Recommended practice</b>
15985 <p><a name="7.21.4.3p3" href="#7.21.4.3p3"><small>3</small></a>
15986 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
15987 program (this limit may be shared with tmpnam) and there should be no limit on the
15988 number simultaneously open other than this limit and any limit on the number of open
15991 <p><a name="7.21.4.3p4" href="#7.21.4.3p4"><small>4</small></a>
15992 The tmpfile function returns a pointer to the stream of the file that it created. If the file
15993 cannot be created, the tmpfile function returns a null pointer.
15994 <p><b> Forward references</b>: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
15996 <p><small><a href="#Contents">Contents</a></small>
15997 <h5><a name="7.21.4.4" href="#7.21.4.4">7.21.4.4 The tmpnam function</a></h5>
15999 <p><a name="7.21.4.4p1" href="#7.21.4.4p1"><small>1</small></a>
16001 #include <a href="#7.21"><stdio.h></a>
16002 char *tmpnam(char *s);
16004 <p><b>Description</b>
16005 <p><a name="7.21.4.4p2" href="#7.21.4.4p2"><small>2</small></a>
16006 The tmpnam function generates a string that is a valid file name and that is not the same
16007 as the name of an existing file.<sup><a href="#note270"><b>270)</b></a></sup> The function is potentially capable of generating at
16011 least TMP_MAX different strings, but any or all of them may already be in use by existing
16012 files and thus not be suitable return values.
16013 <p><a name="7.21.4.4p3" href="#7.21.4.4p3"><small>3</small></a>
16014 The tmpnam function generates a different string each time it is called.
16015 <p><a name="7.21.4.4p4" href="#7.21.4.4p4"><small>4</small></a>
16016 Calls to the tmpnam function with a null pointer argument may introduce data races with
16017 each other. The implementation shall behave as if no library function calls the tmpnam
16020 <p><a name="7.21.4.4p5" href="#7.21.4.4p5"><small>5</small></a>
16021 If no suitable string can be generated, the tmpnam function returns a null pointer.
16022 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
16023 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
16024 function may modify the same object). If the argument is not a null pointer, it is assumed
16025 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
16026 in that array and returns the argument as its value.
16027 <p><b>Environmental limits</b>
16028 <p><a name="7.21.4.4p6" href="#7.21.4.4p6"><small>6</small></a>
16029 The value of the macro TMP_MAX shall be at least 25.
16031 <p><b>Footnotes</b>
16032 <p><small><a name="note270" href="#note270">270)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
16033 their names should not collide with those generated by conventional naming rules for the
16034 implementation. It is still necessary to use the remove function to remove such files when their use
16035 is ended, and before program termination.
16038 <p><small><a href="#Contents">Contents</a></small>
16039 <h4><a name="7.21.5" href="#7.21.5">7.21.5 File access functions</a></h4>
16041 <p><small><a href="#Contents">Contents</a></small>
16042 <h5><a name="7.21.5.1" href="#7.21.5.1">7.21.5.1 The fclose function</a></h5>
16044 <p><a name="7.21.5.1p1" href="#7.21.5.1p1"><small>1</small></a>
16046 #include <a href="#7.21"><stdio.h></a>
16047 int fclose(FILE *stream);
16049 <p><b>Description</b>
16050 <p><a name="7.21.5.1p2" href="#7.21.5.1p2"><small>2</small></a>
16051 A successful call to the fclose function causes the stream pointed to by stream to be
16052 flushed and the associated file to be closed. Any unwritten buffered data for the stream
16053 are delivered to the host environment to be written to the file; any unread buffered data
16054 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
16055 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
16056 (and deallocated if it was automatically allocated).
16058 <p><a name="7.21.5.1p3" href="#7.21.5.1p3"><small>3</small></a>
16059 The fclose function returns zero if the stream was successfully closed, or EOF if any
16060 errors were detected.
16063 <p><small><a href="#Contents">Contents</a></small>
16064 <h5><a name="7.21.5.2" href="#7.21.5.2">7.21.5.2 The fflush function</a></h5>
16066 <p><a name="7.21.5.2p1" href="#7.21.5.2p1"><small>1</small></a>
16068 #include <a href="#7.21"><stdio.h></a>
16069 int fflush(FILE *stream);
16071 <p><b>Description</b>
16072 <p><a name="7.21.5.2p2" href="#7.21.5.2p2"><small>2</small></a>
16073 If stream points to an output stream or an update stream in which the most recent
16074 operation was not input, the fflush function causes any unwritten data for that stream
16075 to be delivered to the host environment to be written to the file; otherwise, the behavior is
16077 <p><a name="7.21.5.2p3" href="#7.21.5.2p3"><small>3</small></a>
16078 If stream is a null pointer, the fflush function performs this flushing action on all
16079 streams for which the behavior is defined above.
16081 <p><a name="7.21.5.2p4" href="#7.21.5.2p4"><small>4</small></a>
16082 The fflush function sets the error indicator for the stream and returns EOF if a write
16083 error occurs, otherwise it returns zero.
16084 <p><b> Forward references</b>: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
16086 <p><small><a href="#Contents">Contents</a></small>
16087 <h5><a name="7.21.5.3" href="#7.21.5.3">7.21.5.3 The fopen function</a></h5>
16089 <p><a name="7.21.5.3p1" href="#7.21.5.3p1"><small>1</small></a>
16091 #include <a href="#7.21"><stdio.h></a>
16092 FILE *fopen(const char * restrict filename,
16093 const char * restrict mode);
16095 <p><b>Description</b>
16096 <p><a name="7.21.5.3p2" href="#7.21.5.3p2"><small>2</small></a>
16097 The fopen function opens the file whose name is the string pointed to by filename,
16098 and associates a stream with it.
16099 <p><a name="7.21.5.3p3" href="#7.21.5.3p3"><small>3</small></a>
16100 The argument mode points to a string. If the string is one of the following, the file is
16101 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note271"><b>271)</b></a></sup>
16102 r open text file for reading
16103 w truncate to zero length or create text file for writing
16104 wx create text file for writing
16105 a append; open or create text file for writing at end-of-file
16106 rb open binary file for reading
16107 wb truncate to zero length or create binary file for writing
16111 wbx create binary file for writing
16112 ab append; open or create binary file for writing at end-of-file
16113 r+ open text file for update (reading and writing)
16114 w+ truncate to zero length or create text file for update
16115 w+x create text file for update
16116 a+ append; open or create text file for update, writing at end-of-file
16117 r+b or rb+ open binary file for update (reading and writing)
16118 w+b or wb+ truncate to zero length or create binary file for update
16119 w+bx or wb+x create binary file for update
16120 a+b or ab+ append; open or create binary file for update, writing at end-of-file
16121 <p><a name="7.21.5.3p4" href="#7.21.5.3p4"><small>4</small></a>
16122 Opening a file with read mode ('r' as the first character in the mode argument) fails if
16123 the file does not exist or cannot be read.
16124 <p><a name="7.21.5.3p5" href="#7.21.5.3p5"><small>5</small></a>
16125 Opening a file with exclusive mode ('x' as the last character in the mode argument)
16126 fails if the file already exists or cannot be created. Otherwise, the file is created with
16127 exclusive (also known as non-shared) access to the extent that the underlying system
16128 supports exclusive access.
16129 <p><a name="7.21.5.3p6" href="#7.21.5.3p6"><small>6</small></a>
16130 Opening a file with append mode ('a' as the first character in the mode argument)
16131 causes all subsequent writes to the file to be forced to the then current end-of-file,
16132 regardless of intervening calls to the fseek function. In some implementations, opening
16133 a binary file with append mode ('b' as the second or third character in the above list of
16134 mode argument values) may initially position the file position indicator for the stream
16135 beyond the last data written, because of null character padding.
16136 <p><a name="7.21.5.3p7" href="#7.21.5.3p7"><small>7</small></a>
16137 When a file is opened with update mode ('+' as the second or third character in the
16138 above list of mode argument values), both input and output may be performed on the
16139 associated stream. However, output shall not be directly followed by input without an
16140 intervening call to the fflush function or to a file positioning function (fseek,
16141 fsetpos, or rewind), and input shall not be directly followed by output without an
16142 intervening call to a file positioning function, unless the input operation encounters end-
16143 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
16144 binary stream in some implementations.
16145 <p><a name="7.21.5.3p8" href="#7.21.5.3p8"><small>8</small></a>
16146 When opened, a stream is fully buffered if and only if it can be determined not to refer to
16147 an interactive device. The error and end-of-file indicators for the stream are cleared.
16149 <p><a name="7.21.5.3p9" href="#7.21.5.3p9"><small>9</small></a>
16150 The fopen function returns a pointer to the object controlling the stream. If the open
16151 operation fails, fopen returns a null pointer.
16152 <p><b> Forward references</b>: file positioning functions (<a href="#7.21.9">7.21.9</a>).
16155 <p><b>Footnotes</b>
16156 <p><small><a name="note271" href="#note271">271)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
16157 remaining characters, or it might use them to select different kinds of a file (some of which might not
16158 conform to the properties in <a href="#7.21.2">7.21.2</a>).
16161 <p><small><a href="#Contents">Contents</a></small>
16162 <h5><a name="7.21.5.4" href="#7.21.5.4">7.21.5.4 The freopen function</a></h5>
16164 <p><a name="7.21.5.4p1" href="#7.21.5.4p1"><small>1</small></a>
16166 #include <a href="#7.21"><stdio.h></a>
16167 FILE *freopen(const char * restrict filename,
16168 const char * restrict mode,
16169 FILE * restrict stream);
16171 <p><b>Description</b>
16172 <p><a name="7.21.5.4p2" href="#7.21.5.4p2"><small>2</small></a>
16173 The freopen function opens the file whose name is the string pointed to by filename
16174 and associates the stream pointed to by stream with it. The mode argument is used just
16175 as in the fopen function.<sup><a href="#note272"><b>272)</b></a></sup>
16176 <p><a name="7.21.5.4p3" href="#7.21.5.4p3"><small>3</small></a>
16177 If filename is a null pointer, the freopen function attempts to change the mode of
16178 the stream to that specified by mode, as if the name of the file currently associated with
16179 the stream had been used. It is implementation-defined which changes of mode are
16180 permitted (if any), and under what circumstances.
16181 <p><a name="7.21.5.4p4" href="#7.21.5.4p4"><small>4</small></a>
16182 The freopen function first attempts to close any file that is associated with the specified
16183 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
16184 stream are cleared.
16186 <p><a name="7.21.5.4p5" href="#7.21.5.4p5"><small>5</small></a>
16187 The freopen function returns a null pointer if the open operation fails. Otherwise,
16188 freopen returns the value of stream.
16190 <p><b>Footnotes</b>
16191 <p><small><a name="note272" href="#note272">272)</a> The primary use of the freopen function is to change the file associated with a standard text stream
16192 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
16193 returned by the fopen function may be assigned.
16196 <p><small><a href="#Contents">Contents</a></small>
16197 <h5><a name="7.21.5.5" href="#7.21.5.5">7.21.5.5 The setbuf function</a></h5>
16199 <p><a name="7.21.5.5p1" href="#7.21.5.5p1"><small>1</small></a>
16201 #include <a href="#7.21"><stdio.h></a>
16202 void setbuf(FILE * restrict stream,
16203 char * restrict buf);
16205 <p><b>Description</b>
16206 <p><a name="7.21.5.5p2" href="#7.21.5.5p2"><small>2</small></a>
16207 Except that it returns no value, the setbuf function is equivalent to the setvbuf
16208 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
16209 is a null pointer), with the value _IONBF for mode.
16216 <p><a name="7.21.5.5p3" href="#7.21.5.5p3"><small>3</small></a>
16217 The setbuf function returns no value.
16218 <p><b> Forward references</b>: the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
16220 <p><small><a href="#Contents">Contents</a></small>
16221 <h5><a name="7.21.5.6" href="#7.21.5.6">7.21.5.6 The setvbuf function</a></h5>
16223 <p><a name="7.21.5.6p1" href="#7.21.5.6p1"><small>1</small></a>
16225 #include <a href="#7.21"><stdio.h></a>
16226 int setvbuf(FILE * restrict stream,
16227 char * restrict buf,
16228 int mode, size_t size);
16230 <p><b>Description</b>
16231 <p><a name="7.21.5.6p2" href="#7.21.5.6p2"><small>2</small></a>
16232 The setvbuf function may be used only after the stream pointed to by stream has
16233 been associated with an open file and before any other operation (other than an
16234 unsuccessful call to setvbuf) is performed on the stream. The argument mode
16235 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
16236 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
16237 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
16238 used instead of a buffer allocated by the setvbuf function<sup><a href="#note273"><b>273)</b></a></sup> and the argument size
16239 specifies the size of the array; otherwise, size may determine the size of a buffer
16240 allocated by the setvbuf function. The contents of the array at any time are
16243 <p><a name="7.21.5.6p3" href="#7.21.5.6p3"><small>3</small></a>
16244 The setvbuf function returns zero on success, or nonzero if an invalid value is given
16245 for mode or if the request cannot be honored.
16252 <p><b>Footnotes</b>
16253 <p><small><a name="note273" href="#note273">273)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
16254 before a buffer that has automatic storage duration is deallocated upon block exit.
16257 <p><small><a href="#Contents">Contents</a></small>
16258 <h4><a name="7.21.6" href="#7.21.6">7.21.6 Formatted input/output functions</a></h4>
16259 <p><a name="7.21.6p1" href="#7.21.6p1"><small>1</small></a>
16260 The formatted input/output functions shall behave as if there is a sequence point after the
16261 actions associated with each specifier.<sup><a href="#note274"><b>274)</b></a></sup>
16263 <p><b>Footnotes</b>
16264 <p><small><a name="note274" href="#note274">274)</a> The fprintf functions perform writes to memory for the %n specifier.
16267 <p><small><a href="#Contents">Contents</a></small>
16268 <h5><a name="7.21.6.1" href="#7.21.6.1">7.21.6.1 The fprintf function</a></h5>
16270 <p><a name="7.21.6.1p1" href="#7.21.6.1p1"><small>1</small></a>
16272 #include <a href="#7.21"><stdio.h></a>
16273 int fprintf(FILE * restrict stream,
16274 const char * restrict format, ...);
16276 <p><b>Description</b>
16277 <p><a name="7.21.6.1p2" href="#7.21.6.1p2"><small>2</small></a>
16278 The fprintf function writes output to the stream pointed to by stream, under control
16279 of the string pointed to by format that specifies how subsequent arguments are
16280 converted for output. If there are insufficient arguments for the format, the behavior is
16281 undefined. If the format is exhausted while arguments remain, the excess arguments are
16282 evaluated (as always) but are otherwise ignored. The fprintf function returns when
16283 the end of the format string is encountered.
16284 <p><a name="7.21.6.1p3" href="#7.21.6.1p3"><small>3</small></a>
16285 The format shall be a multibyte character sequence, beginning and ending in its initial
16286 shift state. The format is composed of zero or more directives: ordinary multibyte
16287 characters (not %), which are copied unchanged to the output stream; and conversion
16288 specifications, each of which results in fetching zero or more subsequent arguments,
16289 converting them, if applicable, according to the corresponding conversion specifier, and
16290 then writing the result to the output stream.
16291 <p><a name="7.21.6.1p4" href="#7.21.6.1p4"><small>4</small></a>
16292 Each conversion specification is introduced by the character %. After the %, the following
16293 appear in sequence:
16295 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16297 <li> An optional minimum field width. If the converted value has fewer characters than the
16298 field width, it is padded with spaces (by default) on the left (or right, if the left
16299 adjustment flag, described later, has been given) to the field width. The field width
16300 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note275"><b>275)</b></a></sup>
16301 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16302 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16303 character for a, A, e, E, f, and F conversions, the maximum number of significant
16304 digits for the g and G conversions, or the maximum number of bytes to be written for
16308 s conversions. The precision takes the form of a period (.) followed either by an
16309 asterisk * (described later) or by an optional decimal integer; if only the period is
16310 specified, the precision is taken as zero. If a precision appears with any other
16311 conversion specifier, the behavior is undefined.
16312 <li> An optional length modifier that specifies the size of the argument.
16313 <li> A conversion specifier character that specifies the type of conversion to be applied.
16315 <p><a name="7.21.6.1p5" href="#7.21.6.1p5"><small>5</small></a>
16316 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16317 this case, an int argument supplies the field width or precision. The arguments
16318 specifying field width, or precision, or both, shall appear (in that order) before the
16319 argument (if any) to be converted. A negative field width argument is taken as a - flag
16320 followed by a positive field width. A negative precision argument is taken as if the
16321 precision were omitted.
16322 <p><a name="7.21.6.1p6" href="#7.21.6.1p6"><small>6</small></a>
16323 The flag characters and their meanings are:
16324 - The result of the conversion is left-justified within the field. (It is right-justified if
16326 this flag is not specified.)
16328 + The result of a signed conversion always begins with a plus or minus sign. (It
16330 begins with a sign only when a negative value is converted if this flag is not
16331 specified.)<sup><a href="#note276"><b>276)</b></a></sup>
16333 space If the first character of a signed conversion is not a sign, or if a signed conversion
16335 results in no characters, a space is prefixed to the result. If the space and + flags
16336 both appear, the space flag is ignored.
16338 # The result is converted to an ''alternative form''. For o conversion, it increases
16340 the precision, if and only if necessary, to force the first digit of the result to be a
16341 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16342 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
16343 and G conversions, the result of converting a floating-point number always
16344 contains a decimal-point character, even if no digits follow it. (Normally, a
16345 decimal-point character appears in the result of these conversions only if a digit
16346 follows it.) For g and G conversions, trailing zeros are not removed from the
16347 result. For other conversions, the behavior is undefined.
16349 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16351 (following any indication of sign or base) are used to pad to the field width rather
16352 than performing space padding, except when converting an infinity or NaN. If the
16353 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16359 conversions, if a precision is specified, the 0 flag is ignored. For other
16360 conversions, the behavior is undefined.
16362 <p><a name="7.21.6.1p7" href="#7.21.6.1p7"><small>7</small></a>
16363 The length modifiers and their meanings are:
16364 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16366 signed char or unsigned char argument (the argument will have
16367 been promoted according to the integer promotions, but its value shall be
16368 converted to signed char or unsigned char before printing); or that
16369 a following n conversion specifier applies to a pointer to a signed char
16372 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16374 short int or unsigned short int argument (the argument will
16375 have been promoted according to the integer promotions, but its value shall
16376 be converted to short int or unsigned short int before printing);
16377 or that a following n conversion specifier applies to a pointer to a short
16380 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16382 long int or unsigned long int argument; that a following n
16383 conversion specifier applies to a pointer to a long int argument; that a
16384 following c conversion specifier applies to a wint_t argument; that a
16385 following s conversion specifier applies to a pointer to a wchar_t
16386 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16389 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16391 long long int or unsigned long long int argument; or that a
16392 following n conversion specifier applies to a pointer to a long long int
16395 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16397 an intmax_t or uintmax_t argument; or that a following n conversion
16398 specifier applies to a pointer to an intmax_t argument.
16400 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16402 size_t or the corresponding signed integer type argument; or that a
16403 following n conversion specifier applies to a pointer to a signed integer type
16404 corresponding to size_t argument.
16406 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16409 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16410 following n conversion specifier applies to a pointer to a ptrdiff_t
16413 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16415 applies to a long double argument.
16417 If a length modifier appears with any conversion specifier other than as specified above,
16418 the behavior is undefined.
16419 <p><a name="7.21.6.1p8" href="#7.21.6.1p8"><small>8</small></a>
16420 The conversion specifiers and their meanings are:
16421 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16423 precision specifies the minimum number of digits to appear; if the value
16424 being converted can be represented in fewer digits, it is expanded with
16425 leading zeros. The default precision is 1. The result of converting a zero
16426 value with a precision of zero is no characters.
16428 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16430 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16431 letters abcdef are used for x conversion and the letters ABCDEF for X
16432 conversion. The precision specifies the minimum number of digits to appear;
16433 if the value being converted can be represented in fewer digits, it is expanded
16434 with leading zeros. The default precision is 1. The result of converting a
16435 zero value with a precision of zero is no characters.
16437 f,F A double argument representing a floating-point number is converted to
16439 decimal notation in the style [-]ddd.ddd, where the number of digits after
16440 the decimal-point character is equal to the precision specification. If the
16441 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16442 not specified, no decimal-point character appears. If a decimal-point
16443 character appears, at least one digit appears before it. The value is rounded to
16444 the appropriate number of digits.
16445 A double argument representing an infinity is converted in one of the styles
16446 [-]inf or [-]infinity -- which style is implementation-defined. A
16447 double argument representing a NaN is converted in one of the styles
16448 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
16449 any n-char-sequence, is implementation-defined. The F conversion specifier
16450 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
16451 respectively.<sup><a href="#note277"><b>277)</b></a></sup>
16453 e,E A double argument representing a floating-point number is converted in the
16455 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16456 argument is nonzero) before the decimal-point character and the number of
16457 digits after it is equal to the precision; if the precision is missing, it is taken as
16463 6; if the precision is zero and the # flag is not specified, no decimal-point
16464 character appears. The value is rounded to the appropriate number of digits.
16465 The E conversion specifier produces a number with E instead of e
16466 introducing the exponent. The exponent always contains at least two digits,
16467 and only as many more digits as necessary to represent the exponent. If the
16468 value is zero, the exponent is zero.
16469 A double argument representing an infinity or NaN is converted in the style
16470 of an f or F conversion specifier.
16472 g,G A double argument representing a floating-point number is converted in
16474 style f or e (or in style F or E in the case of a G conversion specifier),
16475 depending on the value converted and the precision. Let P equal the
16476 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16477 Then, if a conversion with style E would have an exponent of X:
16478 -- if P > X >= -4, the conversion is with style f (or F) and precision
16480 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16481 Finally, unless the # flag is used, any trailing zeros are removed from the
16482 fractional portion of the result and the decimal-point character is removed if
16483 there is no fractional portion remaining.
16484 A double argument representing an infinity or NaN is converted in the style
16485 of an f or F conversion specifier.
16487 a,A A double argument representing a floating-point number is converted in the
16489 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16490 nonzero if the argument is a normalized floating-point number and is
16491 otherwise unspecified) before the decimal-point character<sup><a href="#note278"><b>278)</b></a></sup> and the number
16492 of hexadecimal digits after it is equal to the precision; if the precision is
16493 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
16494 an exact representation of the value; if the precision is missing and
16495 FLT_RADIX is not a power of 2, then the precision is sufficient to
16503 distinguish<sup><a href="#note279"><b>279)</b></a></sup> values of type double, except that trailing zeros may be
16504 omitted; if the precision is zero and the # flag is not specified, no decimal-
16505 point character appears. The letters abcdef are used for a conversion and
16506 the letters ABCDEF for A conversion. The A conversion specifier produces a
16507 number with X and P instead of x and p. The exponent always contains at
16508 least one digit, and only as many more digits as necessary to represent the
16509 decimal exponent of 2. If the value is zero, the exponent is zero.
16510 A double argument representing an infinity or NaN is converted in the style
16511 of an f or F conversion specifier.
16513 c If no l length modifier is present, the int argument is converted to an
16515 unsigned char, and the resulting character is written.
16516 If an l length modifier is present, the wint_t argument is converted as if by
16517 an ls conversion specification with no precision and an argument that points
16518 to the initial element of a two-element array of wchar_t, the first element
16519 containing the wint_t argument to the lc conversion specification and the
16520 second a null wide character.
16522 s If no l length modifier is present, the argument shall be a pointer to the initial
16524 element of an array of character type.<sup><a href="#note280"><b>280)</b></a></sup> Characters from the array are
16525 written up to (but not including) the terminating null character. If the
16526 precision is specified, no more than that many bytes are written. If the
16527 precision is not specified or is greater than the size of the array, the array shall
16528 contain a null character.
16529 If an l length modifier is present, the argument shall be a pointer to the initial
16530 element of an array of wchar_t type. Wide characters from the array are
16531 converted to multibyte characters (each as if by a call to the wcrtomb
16532 function, with the conversion state described by an mbstate_t object
16533 initialized to zero before the first wide character is converted) up to and
16534 including a terminating null wide character. The resulting multibyte
16535 characters are written up to (but not including) the terminating null character
16536 (byte). If no precision is specified, the array shall contain a null wide
16537 character. If a precision is specified, no more than that many bytes are
16538 written (including shift sequences, if any), and the array shall contain a null
16539 wide character if, to equal the multibyte character sequence length given by
16544 the precision, the function would need to access a wide character one past the
16545 end of the array. In no case is a partial multibyte character written.<sup><a href="#note281"><b>281)</b></a></sup>
16547 p The argument shall be a pointer to void. The value of the pointer is
16549 converted to a sequence of printing characters, in an implementation-defined
16552 n The argument shall be a pointer to signed integer into which is written the
16554 number of characters written to the output stream so far by this call to
16555 fprintf. No argument is converted, but one is consumed. If the conversion
16556 specification includes any flags, a field width, or a precision, the behavior is
16559 % A % character is written. No argument is converted. The complete
16561 conversion specification shall be %%.
16563 <p><a name="7.21.6.1p9" href="#7.21.6.1p9"><small>9</small></a>
16564 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note282"><b>282)</b></a></sup> If any argument is
16565 not the correct type for the corresponding conversion specification, the behavior is
16567 <p><a name="7.21.6.1p10" href="#7.21.6.1p10"><small>10</small></a>
16568 In no case does a nonexistent or small field width cause truncation of a field; if the result
16569 of a conversion is wider than the field width, the field is expanded to contain the
16571 <p><a name="7.21.6.1p11" href="#7.21.6.1p11"><small>11</small></a>
16572 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16573 to a hexadecimal floating number with the given precision.
16574 <p><b>Recommended practice</b>
16575 <p><a name="7.21.6.1p12" href="#7.21.6.1p12"><small>12</small></a>
16576 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16577 representable in the given precision, the result should be one of the two adjacent numbers
16578 in hexadecimal floating style with the given precision, with the extra stipulation that the
16579 error should have a correct sign for the current rounding direction.
16580 <p><a name="7.21.6.1p13" href="#7.21.6.1p13"><small>13</small></a>
16581 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16582 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note283"><b>283)</b></a></sup> If the number of
16583 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16584 representable with DECIMAL_DIG digits, then the result should be an exact
16585 representation with trailing zeros. Otherwise, the source value is bounded by two
16586 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16590 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16591 the error should have a correct sign for the current rounding direction.
16593 <p><a name="7.21.6.1p14" href="#7.21.6.1p14"><small>14</small></a>
16594 The fprintf function returns the number of characters transmitted, or a negative value
16595 if an output or encoding error occurred.
16596 <p><b>Environmental limits</b>
16597 <p><a name="7.21.6.1p15" href="#7.21.6.1p15"><small>15</small></a>
16598 The number of characters that can be produced by any single conversion shall be at least
16600 <p><a name="7.21.6.1p16" href="#7.21.6.1p16"><small>16</small></a>
16601 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16604 #include <a href="#7.12"><math.h></a>
16605 #include <a href="#7.21"><stdio.h></a>
16607 char *weekday, *month; // pointers to strings
16608 int day, hour, min;
16609 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
16610 weekday, month, day, hour, min);
16611 fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
16614 <p><a name="7.21.6.1p17" href="#7.21.6.1p17"><small>17</small></a>
16615 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
16616 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
16617 the first of which is denoted here by a and the second by an uppercase letter.
16618 <p><a name="7.21.6.1p18" href="#7.21.6.1p18"><small>18</small></a>
16619 Given the following wide string with length seven,
16621 static wchar_t wstr[] = L" X Yabc Z W";
16625 fprintf(stdout, "|1234567890123|\n");
16626 fprintf(stdout, "|%13ls|\n", wstr);
16627 fprintf(stdout, "|%-13.9ls|\n", wstr);
16628 fprintf(stdout, "|%13.10ls|\n", wstr);
16629 fprintf(stdout, "|%13.11ls|\n", wstr);
16630 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
16631 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
16633 will print the following seven lines:
16644 <p><b> Forward references</b>: conversion state (<a href="#7.29.6">7.29.6</a>), the wcrtomb function (<a href="#7.29.6.3.3">7.29.6.3.3</a>).
16647 <p><b>Footnotes</b>
16648 <p><small><a name="note275" href="#note275">275)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
16650 <p><small><a name="note276" href="#note276">276)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
16651 include a minus sign.
16653 <p><small><a name="note277" href="#note277">277)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
16654 the # and 0 flag characters have no effect.
16656 <p><small><a name="note278" href="#note278">278)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
16657 that subsequent digits align to nibble (4-bit) boundaries.
16659 <p><small><a name="note279" href="#note279">279)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
16660 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16661 might suffice depending on the implementation's scheme for determining the digit to the left of the
16662 decimal-point character.
16664 <p><small><a name="note280" href="#note280">280)</a> No special provisions are made for multibyte characters.
16666 <p><small><a name="note281" href="#note281">281)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
16668 <p><small><a name="note282" href="#note282">282)</a> See ''future library directions'' (<a href="#7.31.11">7.31.11</a>).
16670 <p><small><a name="note283" href="#note283">283)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
16671 given format specifier. The number of significant digits is determined by the format specifier, and in
16672 the case of fixed-point conversion by the source value as well.
16675 <p><small><a href="#Contents">Contents</a></small>
16676 <h5><a name="7.21.6.2" href="#7.21.6.2">7.21.6.2 The fscanf function</a></h5>
16678 <p><a name="7.21.6.2p1" href="#7.21.6.2p1"><small>1</small></a>
16680 #include <a href="#7.21"><stdio.h></a>
16681 int fscanf(FILE * restrict stream,
16682 const char * restrict format, ...);
16684 <p><b>Description</b>
16685 <p><a name="7.21.6.2p2" href="#7.21.6.2p2"><small>2</small></a>
16686 The fscanf function reads input from the stream pointed to by stream, under control
16687 of the string pointed to by format that specifies the admissible input sequences and how
16688 they are to be converted for assignment, using subsequent arguments as pointers to the
16689 objects to receive the converted input. If there are insufficient arguments for the format,
16690 the behavior is undefined. If the format is exhausted while arguments remain, the excess
16691 arguments are evaluated (as always) but are otherwise ignored.
16692 <p><a name="7.21.6.2p3" href="#7.21.6.2p3"><small>3</small></a>
16693 The format shall be a multibyte character sequence, beginning and ending in its initial
16694 shift state. The format is composed of zero or more directives: one or more white-space
16695 characters, an ordinary multibyte character (neither % nor a white-space character), or a
16696 conversion specification. Each conversion specification is introduced by the character %.
16697 After the %, the following appear in sequence:
16699 <li> An optional assignment-suppressing character *.
16700 <li> An optional decimal integer greater than zero that specifies the maximum field width
16702 <li> An optional length modifier that specifies the size of the receiving object.
16703 <li> A conversion specifier character that specifies the type of conversion to be applied.
16705 <p><a name="7.21.6.2p4" href="#7.21.6.2p4"><small>4</small></a>
16706 The fscanf function executes each directive of the format in turn. When all directives
16707 have been executed, or if a directive fails (as detailed below), the function returns.
16708 Failures are described as input failures (due to the occurrence of an encoding error or the
16709 unavailability of input characters), or matching failures (due to inappropriate input).
16710 <p><a name="7.21.6.2p5" href="#7.21.6.2p5"><small>5</small></a>
16711 A directive composed of white-space character(s) is executed by reading input up to the
16712 first non-white-space character (which remains unread), or until no more characters can
16713 be read. The directive never fails.
16714 <p><a name="7.21.6.2p6" href="#7.21.6.2p6"><small>6</small></a>
16715 A directive that is an ordinary multibyte character is executed by reading the next
16716 characters of the stream. If any of those characters differ from the ones composing the
16717 directive, the directive fails and the differing and subsequent characters remain unread.
16718 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
16719 read, the directive fails.
16720 <p><a name="7.21.6.2p7" href="#7.21.6.2p7"><small>7</small></a>
16721 A directive that is a conversion specification defines a set of matching input sequences, as
16722 described below for each specifier. A conversion specification is executed in the
16725 <p><a name="7.21.6.2p8" href="#7.21.6.2p8"><small>8</small></a>
16726 Input white-space characters (as specified by the isspace function) are skipped, unless
16727 the specification includes a [, c, or n specifier.<sup><a href="#note284"><b>284)</b></a></sup>
16728 <p><a name="7.21.6.2p9" href="#7.21.6.2p9"><small>9</small></a>
16729 An input item is read from the stream, unless the specification includes an n specifier. An
16730 input item is defined as the longest sequence of input characters which does not exceed
16731 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note285"><b>285)</b></a></sup>
16732 The first character, if any, after the input item remains unread. If the length of the input
16733 item is zero, the execution of the directive fails; this condition is a matching failure unless
16734 end-of-file, an encoding error, or a read error prevented input from the stream, in which
16735 case it is an input failure.
16736 <p><a name="7.21.6.2p10" href="#7.21.6.2p10"><small>10</small></a>
16737 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
16738 count of input characters) is converted to a type appropriate to the conversion specifier. If
16739 the input item is not a matching sequence, the execution of the directive fails: this
16740 condition is a matching failure. Unless assignment suppression was indicated by a *, the
16741 result of the conversion is placed in the object pointed to by the first argument following
16742 the format argument that has not already received a conversion result. If this object
16743 does not have an appropriate type, or if the result of the conversion cannot be represented
16744 in the object, the behavior is undefined.
16745 <p><a name="7.21.6.2p11" href="#7.21.6.2p11"><small>11</small></a>
16746 The length modifiers and their meanings are:
16747 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16749 to an argument with type pointer to signed char or unsigned char.
16751 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16753 to an argument with type pointer to short int or unsigned short
16756 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16758 to an argument with type pointer to long int or unsigned long
16759 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
16760 an argument with type pointer to double; or that a following c, s, or [
16761 conversion specifier applies to an argument with type pointer to wchar_t.
16763 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16765 to an argument with type pointer to long long int or unsigned
16772 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16774 to an argument with type pointer to intmax_t or uintmax_t.
16776 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16778 to an argument with type pointer to size_t or the corresponding signed
16781 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16783 to an argument with type pointer to ptrdiff_t or the corresponding
16784 unsigned integer type.
16786 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16788 applies to an argument with type pointer to long double.
16790 If a length modifier appears with any conversion specifier other than as specified above,
16791 the behavior is undefined.
16792 <p><a name="7.21.6.2p12" href="#7.21.6.2p12"><small>12</small></a>
16793 The conversion specifiers and their meanings are:
16794 d Matches an optionally signed decimal integer, whose format is the same as
16796 expected for the subject sequence of the strtol function with the value 10
16797 for the base argument. The corresponding argument shall be a pointer to
16800 i Matches an optionally signed integer, whose format is the same as expected
16802 for the subject sequence of the strtol function with the value 0 for the
16803 base argument. The corresponding argument shall be a pointer to signed
16806 o Matches an optionally signed octal integer, whose format is the same as
16808 expected for the subject sequence of the strtoul function with the value 8
16809 for the base argument. The corresponding argument shall be a pointer to
16812 u Matches an optionally signed decimal integer, whose format is the same as
16814 expected for the subject sequence of the strtoul function with the value 10
16815 for the base argument. The corresponding argument shall be a pointer to
16818 x Matches an optionally signed hexadecimal integer, whose format is the same
16820 as expected for the subject sequence of the strtoul function with the value
16821 16 for the base argument. The corresponding argument shall be a pointer to
16824 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
16827 format is the same as expected for the subject sequence of the strtod
16828 function. The corresponding argument shall be a pointer to floating.
16830 c Matches a sequence of characters of exactly the number specified by the field
16832 width (1 if no field width is present in the directive).<sup><a href="#note286"><b>286)</b></a></sup>
16833 If no l length modifier is present, the corresponding argument shall be a
16834 pointer to the initial element of a character array large enough to accept the
16835 sequence. No null character is added.
16836 If an l length modifier is present, the input shall be a sequence of multibyte
16837 characters that begins in the initial shift state. Each multibyte character in the
16838 sequence is converted to a wide character as if by a call to the mbrtowc
16839 function, with the conversion state described by an mbstate_t object
16840 initialized to zero before the first multibyte character is converted. The
16841 corresponding argument shall be a pointer to the initial element of an array of
16842 wchar_t large enough to accept the resulting sequence of wide characters.
16843 No null wide character is added.
16845 s Matches a sequence of non-white-space characters.<sup><a href="#note286"><b>286)</b></a></sup>
16847 If no l length modifier is present, the corresponding argument shall be a
16848 pointer to the initial element of a character array large enough to accept the
16849 sequence and a terminating null character, which will be added automatically.
16850 If an l length modifier is present, the input shall be a sequence of multibyte
16851 characters that begins in the initial shift state. Each multibyte character is
16852 converted to a wide character as if by a call to the mbrtowc function, with
16853 the conversion state described by an mbstate_t object initialized to zero
16854 before the first multibyte character is converted. The corresponding argument
16855 shall be a pointer to the initial element of an array of wchar_t large enough
16856 to accept the sequence and the terminating null wide character, which will be
16857 added automatically.
16859 [ Matches a nonempty sequence of characters from a set of expected characters
16861 (the scanset).<sup><a href="#note286"><b>286)</b></a></sup>
16862 If no l length modifier is present, the corresponding argument shall be a
16863 pointer to the initial element of a character array large enough to accept the
16864 sequence and a terminating null character, which will be added automatically.
16865 If an l length modifier is present, the input shall be a sequence of multibyte
16866 characters that begins in the initial shift state. Each multibyte character is
16867 converted to a wide character as if by a call to the mbrtowc function, with
16868 the conversion state described by an mbstate_t object initialized to zero
16873 before the first multibyte character is converted. The corresponding argument
16874 shall be a pointer to the initial element of an array of wchar_t large enough
16875 to accept the sequence and the terminating null wide character, which will be
16876 added automatically.
16877 The conversion specifier includes all subsequent characters in the format
16878 string, up to and including the matching right bracket (]). The characters
16879 between the brackets (the scanlist) compose the scanset, unless the character
16880 after the left bracket is a circumflex (^), in which case the scanset contains all
16881 characters that do not appear in the scanlist between the circumflex and the
16882 right bracket. If the conversion specifier begins with [] or [^], the right
16883 bracket character is in the scanlist and the next following right bracket
16884 character is the matching right bracket that ends the specification; otherwise
16885 the first following right bracket character is the one that ends the
16886 specification. If a - character is in the scanlist and is not the first, nor the
16887 second where the first character is a ^, nor the last character, the behavior is
16888 implementation-defined.
16890 p Matches an implementation-defined set of sequences, which should be the
16892 same as the set of sequences that may be produced by the %p conversion of
16893 the fprintf function. The corresponding argument shall be a pointer to a
16894 pointer to void. The input item is converted to a pointer value in an
16895 implementation-defined manner. If the input item is a value converted earlier
16896 during the same program execution, the pointer that results shall compare
16897 equal to that value; otherwise the behavior of the %p conversion is undefined.
16899 n No input is consumed. The corresponding argument shall be a pointer to
16901 signed integer into which is to be written the number of characters read from
16902 the input stream so far by this call to the fscanf function. Execution of a
16903 %n directive does not increment the assignment count returned at the
16904 completion of execution of the fscanf function. No argument is converted,
16905 but one is consumed. If the conversion specification includes an assignment-
16906 suppressing character or a field width, the behavior is undefined.
16908 % Matches a single % character; no conversion or assignment occurs. The
16910 complete conversion specification shall be %%.
16912 <p><a name="7.21.6.2p13" href="#7.21.6.2p13"><small>13</small></a>
16913 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note287"><b>287)</b></a></sup>
16914 <p><a name="7.21.6.2p14" href="#7.21.6.2p14"><small>14</small></a>
16915 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16916 respectively, a, e, f, g, and x.
16921 <p><a name="7.21.6.2p15" href="#7.21.6.2p15"><small>15</small></a>
16922 Trailing white space (including new-line characters) is left unread unless matched by a
16923 directive. The success of literal matches and suppressed assignments is not directly
16924 determinable other than via the %n directive.
16926 <p><a name="7.21.6.2p16" href="#7.21.6.2p16"><small>16</small></a>
16927 The fscanf function returns the value of the macro EOF if an input failure occurs
16928 before the first conversion (if any) has completed. Otherwise, the function returns the
16929 number of input items assigned, which can be fewer than provided for, or even zero, in
16930 the event of an early matching failure.
16931 <p><a name="7.21.6.2p17" href="#7.21.6.2p17"><small>17</small></a>
16932 EXAMPLE 1 The call:
16934 #include <a href="#7.21"><stdio.h></a>
16936 int n, i; float x; char name[50];
16937 n = fscanf(stdin, "%d%f%s", &i, &x, name);
16939 with the input line:
16941 25 54.32E-1 thompson
16943 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16946 <p><a name="7.21.6.2p18" href="#7.21.6.2p18"><small>18</small></a>
16947 EXAMPLE 2 The call:
16949 #include <a href="#7.21"><stdio.h></a>
16951 int i; float x; char name[50];
16952 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
16958 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
16959 sequence 56\0. The next character read from the input stream will be a.
16961 <p><a name="7.21.6.2p19" href="#7.21.6.2p19"><small>19</small></a>
16962 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
16964 #include <a href="#7.21"><stdio.h></a>
16966 int count; float quant; char units[21], item[21];
16968 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
16969 fscanf(stdin,"%*[^\n]");
16970 } while (!feof(stdin) && !ferror(stdin));
16972 <p><a name="7.21.6.2p20" href="#7.21.6.2p20"><small>20</small></a>
16973 If the stdin stream contains the following lines:
16977 -12.8degrees Celsius
16983 the execution of the above example will be analogous to the following assignments:
16985 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
16987 quant = -12.8; strcpy(units, "degrees");
16988 count = 2; // "C" fails to match "o"
16989 count = 0; // "l" fails to match "%f"
16990 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
16992 count = 0; // "100e" fails to match "%f"
16996 <p><a name="7.21.6.2p21" href="#7.21.6.2p21"><small>21</small></a>
16999 #include <a href="#7.21"><stdio.h></a>
17001 int d1, d2, n1, n2, i;
17002 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
17004 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure, the value
17005 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
17007 <p><a name="7.21.6.2p22" href="#7.21.6.2p22"><small>22</small></a>
17008 EXAMPLE 5 The call:
17010 #include <a href="#7.21"><stdio.h></a>
17013 n = sscanf("foo % bar 42", "foo%%bar%d", &i);
17015 will assign to n the value 1 and to i the value 42 because input white-space characters are skipped for both
17016 the % and d conversion specifiers.
17018 <p><a name="7.21.6.2p23" href="#7.21.6.2p23"><small>23</small></a>
17019 EXAMPLE 6 In these examples, multibyte characters do have a state-dependent encoding, and the
17020 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
17021 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
17022 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
17023 entry into the alternate shift state.
17024 <p><a name="7.21.6.2p24" href="#7.21.6.2p24"><small>24</small></a>
17027 #include <a href="#7.21"><stdio.h></a>
17030 fscanf(stdin, "a%s", str);
17032 with the input line:
17034 a(uparrow) X Y(downarrow) bc
17036 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
17037 characters, in the more general case) appears to be a single-byte white-space character.
17038 <p><a name="7.21.6.2p25" href="#7.21.6.2p25"><small>25</small></a>
17039 In contrast, after the call:
17042 #include <a href="#7.21"><stdio.h></a>
17043 #include <a href="#7.19"><stddef.h></a>
17046 fscanf(stdin, "a%ls", wstr);
17048 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
17049 terminating null wide character.
17050 <p><a name="7.21.6.2p26" href="#7.21.6.2p26"><small>26</small></a>
17053 #include <a href="#7.21"><stdio.h></a>
17054 #include <a href="#7.19"><stddef.h></a>
17057 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
17059 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
17061 <p><a name="7.21.6.2p27" href="#7.21.6.2p27"><small>27</small></a>
17062 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
17063 character Y, after the call:
17065 #include <a href="#7.21"><stdio.h></a>
17066 #include <a href="#7.19"><stddef.h></a>
17069 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
17071 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
17072 multibyte character.
17074 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
17075 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
17076 (<a href="#7.29.6">7.29.6</a>), the wcrtomb function (<a href="#7.29.6.3.3">7.29.6.3.3</a>).
17078 <p><b>Footnotes</b>
17079 <p><small><a name="note284" href="#note284">284)</a> These white-space characters are not counted against a specified field width.
17081 <p><small><a name="note285" href="#note285">285)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
17082 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
17084 <p><small><a name="note286" href="#note286">286)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
17085 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
17086 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
17088 <p><small><a name="note287" href="#note287">287)</a> See ''future library directions'' (<a href="#7.31.11">7.31.11</a>).
17091 <p><small><a href="#Contents">Contents</a></small>
17092 <h5><a name="7.21.6.3" href="#7.21.6.3">7.21.6.3 The printf function</a></h5>
17094 <p><a name="7.21.6.3p1" href="#7.21.6.3p1"><small>1</small></a>
17096 #include <a href="#7.21"><stdio.h></a>
17097 int printf(const char * restrict format, ...);
17099 <p><b>Description</b>
17100 <p><a name="7.21.6.3p2" href="#7.21.6.3p2"><small>2</small></a>
17101 The printf function is equivalent to fprintf with the argument stdout interposed
17102 before the arguments to printf.
17104 <p><a name="7.21.6.3p3" href="#7.21.6.3p3"><small>3</small></a>
17105 The printf function returns the number of characters transmitted, or a negative value if
17106 an output or encoding error occurred.
17109 <p><small><a href="#Contents">Contents</a></small>
17110 <h5><a name="7.21.6.4" href="#7.21.6.4">7.21.6.4 The scanf function</a></h5>
17112 <p><a name="7.21.6.4p1" href="#7.21.6.4p1"><small>1</small></a>
17114 #include <a href="#7.21"><stdio.h></a>
17115 int scanf(const char * restrict format, ...);
17117 <p><b>Description</b>
17118 <p><a name="7.21.6.4p2" href="#7.21.6.4p2"><small>2</small></a>
17119 The scanf function is equivalent to fscanf with the argument stdin interposed
17120 before the arguments to scanf.
17122 <p><a name="7.21.6.4p3" href="#7.21.6.4p3"><small>3</small></a>
17123 The scanf function returns the value of the macro EOF if an input failure occurs before
17124 the first conversion (if any) has completed. Otherwise, the scanf function returns the
17125 number of input items assigned, which can be fewer than provided for, or even zero, in
17126 the event of an early matching failure.
17128 <p><small><a href="#Contents">Contents</a></small>
17129 <h5><a name="7.21.6.5" href="#7.21.6.5">7.21.6.5 The snprintf function</a></h5>
17131 <p><a name="7.21.6.5p1" href="#7.21.6.5p1"><small>1</small></a>
17133 #include <a href="#7.21"><stdio.h></a>
17134 int snprintf(char * restrict s, size_t n,
17135 const char * restrict format, ...);
17137 <p><b>Description</b>
17138 <p><a name="7.21.6.5p2" href="#7.21.6.5p2"><small>2</small></a>
17139 The snprintf function is equivalent to fprintf, except that the output is written into
17140 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
17141 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
17142 discarded rather than being written to the array, and a null character is written at the end
17143 of the characters actually written into the array. If copying takes place between objects
17144 that overlap, the behavior is undefined.
17146 <p><a name="7.21.6.5p3" href="#7.21.6.5p3"><small>3</small></a>
17147 The snprintf function returns the number of characters that would have been written
17148 had n been sufficiently large, not counting the terminating null character, or a negative
17149 value if an encoding error occurred. Thus, the null-terminated output has been
17150 completely written if and only if the returned value is nonnegative and less than n.
17152 <p><small><a href="#Contents">Contents</a></small>
17153 <h5><a name="7.21.6.6" href="#7.21.6.6">7.21.6.6 The sprintf function</a></h5>
17155 <p><a name="7.21.6.6p1" href="#7.21.6.6p1"><small>1</small></a>
17158 #include <a href="#7.21"><stdio.h></a>
17159 int sprintf(char * restrict s,
17160 const char * restrict format, ...);
17162 <p><b>Description</b>
17163 <p><a name="7.21.6.6p2" href="#7.21.6.6p2"><small>2</small></a>
17164 The sprintf function is equivalent to fprintf, except that the output is written into
17165 an array (specified by the argument s) rather than to a stream. A null character is written
17166 at the end of the characters written; it is not counted as part of the returned value. If
17167 copying takes place between objects that overlap, the behavior is undefined.
17169 <p><a name="7.21.6.6p3" href="#7.21.6.6p3"><small>3</small></a>
17170 The sprintf function returns the number of characters written in the array, not
17171 counting the terminating null character, or a negative value if an encoding error occurred.
17173 <p><small><a href="#Contents">Contents</a></small>
17174 <h5><a name="7.21.6.7" href="#7.21.6.7">7.21.6.7 The sscanf function</a></h5>
17176 <p><a name="7.21.6.7p1" href="#7.21.6.7p1"><small>1</small></a>
17178 #include <a href="#7.21"><stdio.h></a>
17179 int sscanf(const char * restrict s,
17180 const char * restrict format, ...);
17182 <p><b>Description</b>
17183 <p><a name="7.21.6.7p2" href="#7.21.6.7p2"><small>2</small></a>
17184 The sscanf function is equivalent to fscanf, except that input is obtained from a
17185 string (specified by the argument s) rather than from a stream. Reaching the end of the
17186 string is equivalent to encountering end-of-file for the fscanf function. If copying
17187 takes place between objects that overlap, the behavior is undefined.
17189 <p><a name="7.21.6.7p3" href="#7.21.6.7p3"><small>3</small></a>
17190 The sscanf function returns the value of the macro EOF if an input failure occurs
17191 before the first conversion (if any) has completed. Otherwise, the sscanf function
17192 returns the number of input items assigned, which can be fewer than provided for, or even
17193 zero, in the event of an early matching failure.
17195 <p><small><a href="#Contents">Contents</a></small>
17196 <h5><a name="7.21.6.8" href="#7.21.6.8">7.21.6.8 The vfprintf function</a></h5>
17198 <p><a name="7.21.6.8p1" href="#7.21.6.8p1"><small>1</small></a>
17200 #include <a href="#7.16"><stdarg.h></a>
17201 #include <a href="#7.21"><stdio.h></a>
17202 int vfprintf(FILE * restrict stream,
17203 const char * restrict format,
17206 <p><b>Description</b>
17207 <p><a name="7.21.6.8p2" href="#7.21.6.8p2"><small>2</small></a>
17208 The vfprintf function is equivalent to fprintf, with the variable argument list
17209 replaced by arg, which shall have been initialized by the va_start macro (and
17210 possibly subsequent va_arg calls). The vfprintf function does not invoke the
17212 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup>
17214 <p><a name="7.21.6.8p3" href="#7.21.6.8p3"><small>3</small></a>
17215 The vfprintf function returns the number of characters transmitted, or a negative
17216 value if an output or encoding error occurred.
17217 <p><a name="7.21.6.8p4" href="#7.21.6.8p4"><small>4</small></a>
17218 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
17220 #include <a href="#7.16"><stdarg.h></a>
17221 #include <a href="#7.21"><stdio.h></a>
17222 void error(char *function_name, char *format, ...)
17225 va_start(args, format);
17226 // print out name of function causing error
17227 fprintf(stderr, "ERROR in %s: ", function_name);
17228 // print out remainder of message
17229 vfprintf(stderr, format, args);
17235 <p><b>Footnotes</b>
17236 <p><small><a name="note288" href="#note288">288)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
17237 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
17240 <p><small><a href="#Contents">Contents</a></small>
17241 <h5><a name="7.21.6.9" href="#7.21.6.9">7.21.6.9 The vfscanf function</a></h5>
17243 <p><a name="7.21.6.9p1" href="#7.21.6.9p1"><small>1</small></a>
17245 #include <a href="#7.16"><stdarg.h></a>
17246 #include <a href="#7.21"><stdio.h></a>
17247 int vfscanf(FILE * restrict stream,
17248 const char * restrict format,
17251 <p><b>Description</b>
17252 <p><a name="7.21.6.9p2" href="#7.21.6.9p2"><small>2</small></a>
17253 The vfscanf function is equivalent to fscanf, with the variable argument list
17254 replaced by arg, which shall have been initialized by the va_start macro (and
17255 possibly subsequent va_arg calls). The vfscanf function does not invoke the
17256 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup>
17258 <p><a name="7.21.6.9p3" href="#7.21.6.9p3"><small>3</small></a>
17259 The vfscanf function returns the value of the macro EOF if an input failure occurs
17260 before the first conversion (if any) has completed. Otherwise, the vfscanf function
17261 returns the number of input items assigned, which can be fewer than provided for, or even
17262 zero, in the event of an early matching failure.
17268 <p><small><a href="#Contents">Contents</a></small>
17269 <h5><a name="7.21.6.10" href="#7.21.6.10">7.21.6.10 The vprintf function</a></h5>
17271 <p><a name="7.21.6.10p1" href="#7.21.6.10p1"><small>1</small></a>
17273 #include <a href="#7.16"><stdarg.h></a>
17274 #include <a href="#7.21"><stdio.h></a>
17275 int vprintf(const char * restrict format,
17278 <p><b>Description</b>
17279 <p><a name="7.21.6.10p2" href="#7.21.6.10p2"><small>2</small></a>
17280 The vprintf function is equivalent to printf, with the variable argument list
17281 replaced by arg, which shall have been initialized by the va_start macro (and
17282 possibly subsequent va_arg calls). The vprintf function does not invoke the
17283 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup>
17285 <p><a name="7.21.6.10p3" href="#7.21.6.10p3"><small>3</small></a>
17286 The vprintf function returns the number of characters transmitted, or a negative value
17287 if an output or encoding error occurred.
17289 <p><small><a href="#Contents">Contents</a></small>
17290 <h5><a name="7.21.6.11" href="#7.21.6.11">7.21.6.11 The vscanf function</a></h5>
17292 <p><a name="7.21.6.11p1" href="#7.21.6.11p1"><small>1</small></a>
17294 #include <a href="#7.16"><stdarg.h></a>
17295 #include <a href="#7.21"><stdio.h></a>
17296 int vscanf(const char * restrict format,
17299 <p><b>Description</b>
17300 <p><a name="7.21.6.11p2" href="#7.21.6.11p2"><small>2</small></a>
17301 The vscanf function is equivalent to scanf, with the variable argument list replaced
17302 by arg, which shall have been initialized by the va_start macro (and possibly
17303 subsequent va_arg calls). The vscanf function does not invoke the va_end
17304 macro.<sup><a href="#note288"><b>288)</b></a></sup>
17306 <p><a name="7.21.6.11p3" href="#7.21.6.11p3"><small>3</small></a>
17307 The vscanf function returns the value of the macro EOF if an input failure occurs
17308 before the first conversion (if any) has completed. Otherwise, the vscanf function
17309 returns the number of input items assigned, which can be fewer than provided for, or even
17310 zero, in the event of an early matching failure.
17313 <p><small><a href="#Contents">Contents</a></small>
17314 <h5><a name="7.21.6.12" href="#7.21.6.12">7.21.6.12 The vsnprintf function</a></h5>
17316 <p><a name="7.21.6.12p1" href="#7.21.6.12p1"><small>1</small></a>
17318 #include <a href="#7.16"><stdarg.h></a>
17319 #include <a href="#7.21"><stdio.h></a>
17320 int vsnprintf(char * restrict s, size_t n,
17321 const char * restrict format,
17324 <p><b>Description</b>
17325 <p><a name="7.21.6.12p2" href="#7.21.6.12p2"><small>2</small></a>
17326 The vsnprintf function is equivalent to snprintf, with the variable argument list
17327 replaced by arg, which shall have been initialized by the va_start macro (and
17328 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
17329 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup> If copying takes place between objects that overlap, the behavior is
17332 <p><a name="7.21.6.12p3" href="#7.21.6.12p3"><small>3</small></a>
17333 The vsnprintf function returns the number of characters that would have been written
17334 had n been sufficiently large, not counting the terminating null character, or a negative
17335 value if an encoding error occurred. Thus, the null-terminated output has been
17336 completely written if and only if the returned value is nonnegative and less than n.
17338 <p><small><a href="#Contents">Contents</a></small>
17339 <h5><a name="7.21.6.13" href="#7.21.6.13">7.21.6.13 The vsprintf function</a></h5>
17341 <p><a name="7.21.6.13p1" href="#7.21.6.13p1"><small>1</small></a>
17343 #include <a href="#7.16"><stdarg.h></a>
17344 #include <a href="#7.21"><stdio.h></a>
17345 int vsprintf(char * restrict s,
17346 const char * restrict format,
17349 <p><b>Description</b>
17350 <p><a name="7.21.6.13p2" href="#7.21.6.13p2"><small>2</small></a>
17351 The vsprintf function is equivalent to sprintf, with the variable argument list
17352 replaced by arg, which shall have been initialized by the va_start macro (and
17353 possibly subsequent va_arg calls). The vsprintf function does not invoke the
17354 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup> If copying takes place between objects that overlap, the behavior is
17357 <p><a name="7.21.6.13p3" href="#7.21.6.13p3"><small>3</small></a>
17358 The vsprintf function returns the number of characters written in the array, not
17359 counting the terminating null character, or a negative value if an encoding error occurred.
17362 <p><small><a href="#Contents">Contents</a></small>
17363 <h5><a name="7.21.6.14" href="#7.21.6.14">7.21.6.14 The vsscanf function</a></h5>
17365 <p><a name="7.21.6.14p1" href="#7.21.6.14p1"><small>1</small></a>
17367 #include <a href="#7.16"><stdarg.h></a>
17368 #include <a href="#7.21"><stdio.h></a>
17369 int vsscanf(const char * restrict s,
17370 const char * restrict format,
17373 <p><b>Description</b>
17374 <p><a name="7.21.6.14p2" href="#7.21.6.14p2"><small>2</small></a>
17375 The vsscanf function is equivalent to sscanf, with the variable argument list
17376 replaced by arg, which shall have been initialized by the va_start macro (and
17377 possibly subsequent va_arg calls). The vsscanf function does not invoke the
17378 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup>
17380 <p><a name="7.21.6.14p3" href="#7.21.6.14p3"><small>3</small></a>
17381 The vsscanf function returns the value of the macro EOF if an input failure occurs
17382 before the first conversion (if any) has completed. Otherwise, the vsscanf function
17383 returns the number of input items assigned, which can be fewer than provided for, or even
17384 zero, in the event of an early matching failure.
17386 <p><small><a href="#Contents">Contents</a></small>
17387 <h4><a name="7.21.7" href="#7.21.7">7.21.7 Character input/output functions</a></h4>
17389 <p><small><a href="#Contents">Contents</a></small>
17390 <h5><a name="7.21.7.1" href="#7.21.7.1">7.21.7.1 The fgetc function</a></h5>
17392 <p><a name="7.21.7.1p1" href="#7.21.7.1p1"><small>1</small></a>
17394 #include <a href="#7.21"><stdio.h></a>
17395 int fgetc(FILE *stream);
17397 <p><b>Description</b>
17398 <p><a name="7.21.7.1p2" href="#7.21.7.1p2"><small>2</small></a>
17399 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17400 next character is present, the fgetc function obtains that character as an unsigned
17401 char converted to an int and advances the associated file position indicator for the
17402 stream (if defined).
17404 <p><a name="7.21.7.1p3" href="#7.21.7.1p3"><small>3</small></a>
17405 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17406 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
17407 fgetc function returns the next character from the input stream pointed to by stream.
17408 If a read error occurs, the error indicator for the stream is set and the fgetc function
17409 returns EOF.<sup><a href="#note289"><b>289)</b></a></sup>
17414 <p><b>Footnotes</b>
17415 <p><small><a name="note289" href="#note289">289)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17418 <p><small><a href="#Contents">Contents</a></small>
17419 <h5><a name="7.21.7.2" href="#7.21.7.2">7.21.7.2 The fgets function</a></h5>
17421 <p><a name="7.21.7.2p1" href="#7.21.7.2p1"><small>1</small></a>
17423 #include <a href="#7.21"><stdio.h></a>
17424 char *fgets(char * restrict s, int n,
17425 FILE * restrict stream);
17427 <p><b>Description</b>
17428 <p><a name="7.21.7.2p2" href="#7.21.7.2p2"><small>2</small></a>
17429 The fgets function reads at most one less than the number of characters specified by n
17430 from the stream pointed to by stream into the array pointed to by s. No additional
17431 characters are read after a new-line character (which is retained) or after end-of-file. A
17432 null character is written immediately after the last character read into the array.
17434 <p><a name="7.21.7.2p3" href="#7.21.7.2p3"><small>3</small></a>
17435 The fgets function returns s if successful. If end-of-file is encountered and no
17436 characters have been read into the array, the contents of the array remain unchanged and a
17437 null pointer is returned. If a read error occurs during the operation, the array contents are
17438 indeterminate and a null pointer is returned.
17440 <p><small><a href="#Contents">Contents</a></small>
17441 <h5><a name="7.21.7.3" href="#7.21.7.3">7.21.7.3 The fputc function</a></h5>
17443 <p><a name="7.21.7.3p1" href="#7.21.7.3p1"><small>1</small></a>
17445 #include <a href="#7.21"><stdio.h></a>
17446 int fputc(int c, FILE *stream);
17448 <p><b>Description</b>
17449 <p><a name="7.21.7.3p2" href="#7.21.7.3p2"><small>2</small></a>
17450 The fputc function writes the character specified by c (converted to an unsigned
17451 char) to the output stream pointed to by stream, at the position indicated by the
17452 associated file position indicator for the stream (if defined), and advances the indicator
17453 appropriately. If the file cannot support positioning requests, or if the stream was opened
17454 with append mode, the character is appended to the output stream.
17456 <p><a name="7.21.7.3p3" href="#7.21.7.3p3"><small>3</small></a>
17457 The fputc function returns the character written. If a write error occurs, the error
17458 indicator for the stream is set and fputc returns EOF.
17460 <p><small><a href="#Contents">Contents</a></small>
17461 <h5><a name="7.21.7.4" href="#7.21.7.4">7.21.7.4 The fputs function</a></h5>
17463 <p><a name="7.21.7.4p1" href="#7.21.7.4p1"><small>1</small></a>
17466 #include <a href="#7.21"><stdio.h></a>
17467 int fputs(const char * restrict s,
17468 FILE * restrict stream);
17470 <p><b>Description</b>
17471 <p><a name="7.21.7.4p2" href="#7.21.7.4p2"><small>2</small></a>
17472 The fputs function writes the string pointed to by s to the stream pointed to by
17473 stream. The terminating null character is not written.
17475 <p><a name="7.21.7.4p3" href="#7.21.7.4p3"><small>3</small></a>
17476 The fputs function returns EOF if a write error occurs; otherwise it returns a
17479 <p><small><a href="#Contents">Contents</a></small>
17480 <h5><a name="7.21.7.5" href="#7.21.7.5">7.21.7.5 The getc function</a></h5>
17482 <p><a name="7.21.7.5p1" href="#7.21.7.5p1"><small>1</small></a>
17484 #include <a href="#7.21"><stdio.h></a>
17485 int getc(FILE *stream);
17487 <p><b>Description</b>
17488 <p><a name="7.21.7.5p2" href="#7.21.7.5p2"><small>2</small></a>
17489 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
17490 may evaluate stream more than once, so the argument should never be an expression
17493 <p><a name="7.21.7.5p3" href="#7.21.7.5p3"><small>3</small></a>
17494 The getc function returns the next character from the input stream pointed to by
17495 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
17496 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
17499 <p><small><a href="#Contents">Contents</a></small>
17500 <h5><a name="7.21.7.6" href="#7.21.7.6">7.21.7.6 The getchar function</a></h5>
17502 <p><a name="7.21.7.6p1" href="#7.21.7.6p1"><small>1</small></a>
17504 #include <a href="#7.21"><stdio.h></a>
17507 <p><b>Description</b>
17508 <p><a name="7.21.7.6p2" href="#7.21.7.6p2"><small>2</small></a>
17509 The getchar function is equivalent to getc with the argument stdin.
17511 <p><a name="7.21.7.6p3" href="#7.21.7.6p3"><small>3</small></a>
17512 The getchar function returns the next character from the input stream pointed to by
17513 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
17514 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
17515 getchar returns EOF.
17518 <p><small><a href="#Contents">Contents</a></small>
17519 <h5><a name="7.21.7.7" href="#7.21.7.7">7.21.7.7 The putc function</a></h5>
17521 <p><a name="7.21.7.7p1" href="#7.21.7.7p1"><small>1</small></a>
17523 #include <a href="#7.21"><stdio.h></a>
17524 int putc(int c, FILE *stream);
17526 <p><b>Description</b>
17527 <p><a name="7.21.7.7p2" href="#7.21.7.7p2"><small>2</small></a>
17528 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
17529 may evaluate stream more than once, so that argument should never be an expression
17532 <p><a name="7.21.7.7p3" href="#7.21.7.7p3"><small>3</small></a>
17533 The putc function returns the character written. If a write error occurs, the error
17534 indicator for the stream is set and putc returns EOF.
17536 <p><small><a href="#Contents">Contents</a></small>
17537 <h5><a name="7.21.7.8" href="#7.21.7.8">7.21.7.8 The putchar function</a></h5>
17539 <p><a name="7.21.7.8p1" href="#7.21.7.8p1"><small>1</small></a>
17541 #include <a href="#7.21"><stdio.h></a>
17542 int putchar(int c);
17544 <p><b>Description</b>
17545 <p><a name="7.21.7.8p2" href="#7.21.7.8p2"><small>2</small></a>
17546 The putchar function is equivalent to putc with the second argument stdout.
17548 <p><a name="7.21.7.8p3" href="#7.21.7.8p3"><small>3</small></a>
17549 The putchar function returns the character written. If a write error occurs, the error
17550 indicator for the stream is set and putchar returns EOF.
17552 <p><small><a href="#Contents">Contents</a></small>
17553 <h5><a name="7.21.7.9" href="#7.21.7.9">7.21.7.9 The puts function</a></h5>
17555 <p><a name="7.21.7.9p1" href="#7.21.7.9p1"><small>1</small></a>
17557 #include <a href="#7.21"><stdio.h></a>
17558 int puts(const char *s);
17560 <p><b>Description</b>
17561 <p><a name="7.21.7.9p2" href="#7.21.7.9p2"><small>2</small></a>
17562 The puts function writes the string pointed to by s to the stream pointed to by stdout,
17563 and appends a new-line character to the output. The terminating null character is not
17566 <p><a name="7.21.7.9p3" href="#7.21.7.9p3"><small>3</small></a>
17567 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
17571 <p><small><a href="#Contents">Contents</a></small>
17572 <h5><a name="7.21.7.10" href="#7.21.7.10">7.21.7.10 The ungetc function</a></h5>
17574 <p><a name="7.21.7.10p1" href="#7.21.7.10p1"><small>1</small></a>
17576 #include <a href="#7.21"><stdio.h></a>
17577 int ungetc(int c, FILE *stream);
17579 <p><b>Description</b>
17580 <p><a name="7.21.7.10p2" href="#7.21.7.10p2"><small>2</small></a>
17581 The ungetc function pushes the character specified by c (converted to an unsigned
17582 char) back onto the input stream pointed to by stream. Pushed-back characters will be
17583 returned by subsequent reads on that stream in the reverse order of their pushing. A
17584 successful intervening call (with the stream pointed to by stream) to a file positioning
17585 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
17586 stream. The external storage corresponding to the stream is unchanged.
17587 <p><a name="7.21.7.10p3" href="#7.21.7.10p3"><small>3</small></a>
17588 One character of pushback is guaranteed. If the ungetc function is called too many
17589 times on the same stream without an intervening read or file positioning operation on that
17590 stream, the operation may fail.
17591 <p><a name="7.21.7.10p4" href="#7.21.7.10p4"><small>4</small></a>
17592 If the value of c equals that of the macro EOF, the operation fails and the input stream is
17594 <p><a name="7.21.7.10p5" href="#7.21.7.10p5"><small>5</small></a>
17595 A successful call to the ungetc function clears the end-of-file indicator for the stream.
17596 The value of the file position indicator for the stream after reading or discarding all
17597 pushed-back characters shall be the same as it was before the characters were pushed
17598 back. For a text stream, the value of its file position indicator after a successful call to the
17599 ungetc function is unspecified until all pushed-back characters are read or discarded.
17600 For a binary stream, its file position indicator is decremented by each successful call to
17601 the ungetc function; if its value was zero before a call, it is indeterminate after the
17602 call.<sup><a href="#note290"><b>290)</b></a></sup>
17604 <p><a name="7.21.7.10p6" href="#7.21.7.10p6"><small>6</small></a>
17605 The ungetc function returns the character pushed back after conversion, or EOF if the
17607 <p><b> Forward references</b>: file positioning functions (<a href="#7.21.9">7.21.9</a>).
17614 <p><b>Footnotes</b>
17615 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.31.11">7.31.11</a>).
17618 <p><small><a href="#Contents">Contents</a></small>
17619 <h4><a name="7.21.8" href="#7.21.8">7.21.8 Direct input/output functions</a></h4>
17621 <p><small><a href="#Contents">Contents</a></small>
17622 <h5><a name="7.21.8.1" href="#7.21.8.1">7.21.8.1 The fread function</a></h5>
17624 <p><a name="7.21.8.1p1" href="#7.21.8.1p1"><small>1</small></a>
17626 #include <a href="#7.21"><stdio.h></a>
17627 size_t fread(void * restrict ptr,
17628 size_t size, size_t nmemb,
17629 FILE * restrict stream);
17631 <p><b>Description</b>
17632 <p><a name="7.21.8.1p2" href="#7.21.8.1p2"><small>2</small></a>
17633 The fread function reads, into the array pointed to by ptr, up to nmemb elements
17634 whose size is specified by size, from the stream pointed to by stream. For each
17635 object, size calls are made to the fgetc function and the results stored, in the order
17636 read, in an array of unsigned char exactly overlaying the object. The file position
17637 indicator for the stream (if defined) is advanced by the number of characters successfully
17638 read. If an error occurs, the resulting value of the file position indicator for the stream is
17639 indeterminate. If a partial element is read, its value is indeterminate.
17641 <p><a name="7.21.8.1p3" href="#7.21.8.1p3"><small>3</small></a>
17642 The fread function returns the number of elements successfully read, which may be
17643 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
17644 fread returns zero and the contents of the array and the state of the stream remain
17647 <p><small><a href="#Contents">Contents</a></small>
17648 <h5><a name="7.21.8.2" href="#7.21.8.2">7.21.8.2 The fwrite function</a></h5>
17650 <p><a name="7.21.8.2p1" href="#7.21.8.2p1"><small>1</small></a>
17652 #include <a href="#7.21"><stdio.h></a>
17653 size_t fwrite(const void * restrict ptr,
17654 size_t size, size_t nmemb,
17655 FILE * restrict stream);
17657 <p><b>Description</b>
17658 <p><a name="7.21.8.2p2" href="#7.21.8.2p2"><small>2</small></a>
17659 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
17660 whose size is specified by size, to the stream pointed to by stream. For each object,
17661 size calls are made to the fputc function, taking the values (in order) from an array of
17662 unsigned char exactly overlaying the object. The file position indicator for the
17663 stream (if defined) is advanced by the number of characters successfully written. If an
17664 error occurs, the resulting value of the file position indicator for the stream is
17668 <p><a name="7.21.8.2p3" href="#7.21.8.2p3"><small>3</small></a>
17669 The fwrite function returns the number of elements successfully written, which will be
17670 less than nmemb only if a write error is encountered. If size or nmemb is zero,
17671 fwrite returns zero and the state of the stream remains unchanged.
17673 <p><small><a href="#Contents">Contents</a></small>
17674 <h4><a name="7.21.9" href="#7.21.9">7.21.9 File positioning functions</a></h4>
17676 <p><small><a href="#Contents">Contents</a></small>
17677 <h5><a name="7.21.9.1" href="#7.21.9.1">7.21.9.1 The fgetpos function</a></h5>
17679 <p><a name="7.21.9.1p1" href="#7.21.9.1p1"><small>1</small></a>
17681 #include <a href="#7.21"><stdio.h></a>
17682 int fgetpos(FILE * restrict stream,
17683 fpos_t * restrict pos);
17685 <p><b>Description</b>
17686 <p><a name="7.21.9.1p2" href="#7.21.9.1p2"><small>2</small></a>
17687 The fgetpos function stores the current values of the parse state (if any) and file
17688 position indicator for the stream pointed to by stream in the object pointed to by pos.
17689 The values stored contain unspecified information usable by the fsetpos function for
17690 repositioning the stream to its position at the time of the call to the fgetpos function.
17692 <p><a name="7.21.9.1p3" href="#7.21.9.1p3"><small>3</small></a>
17693 If successful, the fgetpos function returns zero; on failure, the fgetpos function
17694 returns nonzero and stores an implementation-defined positive value in errno.
17695 <p><b> Forward references</b>: the fsetpos function (<a href="#7.21.9.3">7.21.9.3</a>).
17697 <p><small><a href="#Contents">Contents</a></small>
17698 <h5><a name="7.21.9.2" href="#7.21.9.2">7.21.9.2 The fseek function</a></h5>
17700 <p><a name="7.21.9.2p1" href="#7.21.9.2p1"><small>1</small></a>
17702 #include <a href="#7.21"><stdio.h></a>
17703 int fseek(FILE *stream, long int offset, int whence);
17705 <p><b>Description</b>
17706 <p><a name="7.21.9.2p2" href="#7.21.9.2p2"><small>2</small></a>
17707 The fseek function sets the file position indicator for the stream pointed to by stream.
17708 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
17709 <p><a name="7.21.9.2p3" href="#7.21.9.2p3"><small>3</small></a>
17710 For a binary stream, the new position, measured in characters from the beginning of the
17711 file, is obtained by adding offset to the position specified by whence. The specified
17712 position is the beginning of the file if whence is SEEK_SET, the current value of the file
17713 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
17714 meaningfully support fseek calls with a whence value of SEEK_END.
17715 <p><a name="7.21.9.2p4" href="#7.21.9.2p4"><small>4</small></a>
17716 For a text stream, either offset shall be zero, or offset shall be a value returned by
17717 an earlier successful call to the ftell function on a stream associated with the same file
17718 and whence shall be SEEK_SET.
17720 <p><a name="7.21.9.2p5" href="#7.21.9.2p5"><small>5</small></a>
17721 After determining the new position, a successful call to the fseek function undoes any
17722 effects of the ungetc function on the stream, clears the end-of-file indicator for the
17723 stream, and then establishes the new position. After a successful fseek call, the next
17724 operation on an update stream may be either input or output.
17726 <p><a name="7.21.9.2p6" href="#7.21.9.2p6"><small>6</small></a>
17727 The fseek function returns nonzero only for a request that cannot be satisfied.
17728 <p><b> Forward references</b>: the ftell function (<a href="#7.21.9.4">7.21.9.4</a>).
17730 <p><small><a href="#Contents">Contents</a></small>
17731 <h5><a name="7.21.9.3" href="#7.21.9.3">7.21.9.3 The fsetpos function</a></h5>
17733 <p><a name="7.21.9.3p1" href="#7.21.9.3p1"><small>1</small></a>
17735 #include <a href="#7.21"><stdio.h></a>
17736 int fsetpos(FILE *stream, const fpos_t *pos);
17738 <p><b>Description</b>
17739 <p><a name="7.21.9.3p2" href="#7.21.9.3p2"><small>2</small></a>
17740 The fsetpos function sets the mbstate_t object (if any) and file position indicator
17741 for the stream pointed to by stream according to the value of the object pointed to by
17742 pos, which shall be a value obtained from an earlier successful call to the fgetpos
17743 function on a stream associated with the same file. If a read or write error occurs, the
17744 error indicator for the stream is set and fsetpos fails.
17745 <p><a name="7.21.9.3p3" href="#7.21.9.3p3"><small>3</small></a>
17746 A successful call to the fsetpos function undoes any effects of the ungetc function
17747 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
17748 parse state and position. After a successful fsetpos call, the next operation on an
17749 update stream may be either input or output.
17751 <p><a name="7.21.9.3p4" href="#7.21.9.3p4"><small>4</small></a>
17752 If successful, the fsetpos function returns zero; on failure, the fsetpos function
17753 returns nonzero and stores an implementation-defined positive value in errno.
17755 <p><small><a href="#Contents">Contents</a></small>
17756 <h5><a name="7.21.9.4" href="#7.21.9.4">7.21.9.4 The ftell function</a></h5>
17758 <p><a name="7.21.9.4p1" href="#7.21.9.4p1"><small>1</small></a>
17760 #include <a href="#7.21"><stdio.h></a>
17761 long int ftell(FILE *stream);
17763 <p><b>Description</b>
17764 <p><a name="7.21.9.4p2" href="#7.21.9.4p2"><small>2</small></a>
17765 The ftell function obtains the current value of the file position indicator for the stream
17766 pointed to by stream. For a binary stream, the value is the number of characters from
17767 the beginning of the file. For a text stream, its file position indicator contains unspecified
17768 information, usable by the fseek function for returning the file position indicator for the
17769 stream to its position at the time of the ftell call; the difference between two such
17770 return values is not necessarily a meaningful measure of the number of characters written
17774 <p><a name="7.21.9.4p3" href="#7.21.9.4p3"><small>3</small></a>
17775 If successful, the ftell function returns the current value of the file position indicator
17776 for the stream. On failure, the ftell function returns -1L and stores an
17777 implementation-defined positive value in errno.
17779 <p><small><a href="#Contents">Contents</a></small>
17780 <h5><a name="7.21.9.5" href="#7.21.9.5">7.21.9.5 The rewind function</a></h5>
17782 <p><a name="7.21.9.5p1" href="#7.21.9.5p1"><small>1</small></a>
17784 #include <a href="#7.21"><stdio.h></a>
17785 void rewind(FILE *stream);
17787 <p><b>Description</b>
17788 <p><a name="7.21.9.5p2" href="#7.21.9.5p2"><small>2</small></a>
17789 The rewind function sets the file position indicator for the stream pointed to by
17790 stream to the beginning of the file. It is equivalent to
17792 (void)fseek(stream, 0L, SEEK_SET)
17794 except that the error indicator for the stream is also cleared.
17796 <p><a name="7.21.9.5p3" href="#7.21.9.5p3"><small>3</small></a>
17797 The rewind function returns no value.
17799 <p><small><a href="#Contents">Contents</a></small>
17800 <h4><a name="7.21.10" href="#7.21.10">7.21.10 Error-handling functions</a></h4>
17802 <p><small><a href="#Contents">Contents</a></small>
17803 <h5><a name="7.21.10.1" href="#7.21.10.1">7.21.10.1 The clearerr function</a></h5>
17805 <p><a name="7.21.10.1p1" href="#7.21.10.1p1"><small>1</small></a>
17807 #include <a href="#7.21"><stdio.h></a>
17808 void clearerr(FILE *stream);
17810 <p><b>Description</b>
17811 <p><a name="7.21.10.1p2" href="#7.21.10.1p2"><small>2</small></a>
17812 The clearerr function clears the end-of-file and error indicators for the stream pointed
17815 <p><a name="7.21.10.1p3" href="#7.21.10.1p3"><small>3</small></a>
17816 The clearerr function returns no value.
17819 <p><small><a href="#Contents">Contents</a></small>
17820 <h5><a name="7.21.10.2" href="#7.21.10.2">7.21.10.2 The feof function</a></h5>
17822 <p><a name="7.21.10.2p1" href="#7.21.10.2p1"><small>1</small></a>
17824 #include <a href="#7.21"><stdio.h></a>
17825 int feof(FILE *stream);
17827 <p><b>Description</b>
17828 <p><a name="7.21.10.2p2" href="#7.21.10.2p2"><small>2</small></a>
17829 The feof function tests the end-of-file indicator for the stream pointed to by stream.
17831 <p><a name="7.21.10.2p3" href="#7.21.10.2p3"><small>3</small></a>
17832 The feof function returns nonzero if and only if the end-of-file indicator is set for
17835 <p><small><a href="#Contents">Contents</a></small>
17836 <h5><a name="7.21.10.3" href="#7.21.10.3">7.21.10.3 The ferror function</a></h5>
17838 <p><a name="7.21.10.3p1" href="#7.21.10.3p1"><small>1</small></a>
17840 #include <a href="#7.21"><stdio.h></a>
17841 int ferror(FILE *stream);
17843 <p><b>Description</b>
17844 <p><a name="7.21.10.3p2" href="#7.21.10.3p2"><small>2</small></a>
17845 The ferror function tests the error indicator for the stream pointed to by stream.
17847 <p><a name="7.21.10.3p3" href="#7.21.10.3p3"><small>3</small></a>
17848 The ferror function returns nonzero if and only if the error indicator is set for
17851 <p><small><a href="#Contents">Contents</a></small>
17852 <h5><a name="7.21.10.4" href="#7.21.10.4">7.21.10.4 The perror function</a></h5>
17854 <p><a name="7.21.10.4p1" href="#7.21.10.4p1"><small>1</small></a>
17856 #include <a href="#7.21"><stdio.h></a>
17857 void perror(const char *s);
17859 <p><b>Description</b>
17860 <p><a name="7.21.10.4p2" href="#7.21.10.4p2"><small>2</small></a>
17861 The perror function maps the error number in the integer expression errno to an
17862 error message. It writes a sequence of characters to the standard error stream thus: first
17863 (if s is not a null pointer and the character pointed to by s is not the null character), the
17864 string pointed to by s followed by a colon (:) and a space; then an appropriate error
17865 message string followed by a new-line character. The contents of the error message
17866 strings are the same as those returned by the strerror function with argument errno.
17868 <p><a name="7.21.10.4p3" href="#7.21.10.4p3"><small>3</small></a>
17869 The perror function returns no value.
17870 <p><b> Forward references</b>: the strerror function (<a href="#7.24.6.2">7.24.6.2</a>).
17873 <p><small><a href="#Contents">Contents</a></small>
17874 <h3><a name="7.22" href="#7.22">7.22 General utilities <stdlib.h></a></h3>
17875 <p><a name="7.22p1" href="#7.22p1"><small>1</small></a>
17876 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
17877 defines several macros.<sup><a href="#note291"><b>291)</b></a></sup>
17878 <p><a name="7.22p2" href="#7.22p2"><small>2</small></a>
17879 The types declared are size_t and wchar_t (both described in <a href="#7.19">7.19</a>),
17883 which is a structure type that is the type of the value returned by the div function,
17887 which is a structure type that is the type of the value returned by the ldiv function, and
17891 which is a structure type that is the type of the value returned by the lldiv function.
17892 <p><a name="7.22p3" href="#7.22p3"><small>3</small></a>
17893 The macros defined are NULL (described in <a href="#7.19">7.19</a>);
17901 which expand to integer constant expressions that can be used as the argument to the
17902 exit function to return unsuccessful or successful termination status, respectively, to the
17907 which expands to an integer constant expression that is the maximum value returned by
17908 the rand function; and
17912 which expands to a positive integer expression with type size_t that is the maximum
17913 number of bytes in a multibyte character for the extended character set specified by the
17914 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
17921 <p><b>Footnotes</b>
17922 <p><small><a name="note291" href="#note291">291)</a> See ''future library directions'' (<a href="#7.31.12">7.31.12</a>).
17925 <p><small><a href="#Contents">Contents</a></small>
17926 <h4><a name="7.22.1" href="#7.22.1">7.22.1 Numeric conversion functions</a></h4>
17927 <p><a name="7.22.1p1" href="#7.22.1p1"><small>1</small></a>
17928 The functions atof, atoi, atol, and atoll need not affect the value of the integer
17929 expression errno on an error. If the value of the result cannot be represented, the
17930 behavior is undefined.
17932 <p><small><a href="#Contents">Contents</a></small>
17933 <h5><a name="7.22.1.1" href="#7.22.1.1">7.22.1.1 The atof function</a></h5>
17935 <p><a name="7.22.1.1p1" href="#7.22.1.1p1"><small>1</small></a>
17937 #include <a href="#7.22"><stdlib.h></a>
17938 double atof(const char *nptr);
17940 <p><b>Description</b>
17941 <p><a name="7.22.1.1p2" href="#7.22.1.1p2"><small>2</small></a>
17942 The atof function converts the initial portion of the string pointed to by nptr to
17943 double representation. Except for the behavior on error, it is equivalent to
17945 strtod(nptr, (char **)NULL)
17948 <p><a name="7.22.1.1p3" href="#7.22.1.1p3"><small>3</small></a>
17949 The atof function returns the converted value.
17950 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
17952 <p><small><a href="#Contents">Contents</a></small>
17953 <h5><a name="7.22.1.2" href="#7.22.1.2">7.22.1.2 The atoi, atol, and atoll functions</a></h5>
17955 <p><a name="7.22.1.2p1" href="#7.22.1.2p1"><small>1</small></a>
17957 #include <a href="#7.22"><stdlib.h></a>
17958 int atoi(const char *nptr);
17959 long int atol(const char *nptr);
17960 long long int atoll(const char *nptr);
17962 <p><b>Description</b>
17963 <p><a name="7.22.1.2p2" href="#7.22.1.2p2"><small>2</small></a>
17964 The atoi, atol, and atoll functions convert the initial portion of the string pointed
17965 to by nptr to int, long int, and long long int representation, respectively.
17966 Except for the behavior on error, they are equivalent to
17968 atoi: (int)strtol(nptr, (char **)NULL, 10)
17969 atol: strtol(nptr, (char **)NULL, 10)
17970 atoll: strtoll(nptr, (char **)NULL, 10)
17973 <p><a name="7.22.1.2p3" href="#7.22.1.2p3"><small>3</small></a>
17974 The atoi, atol, and atoll functions return the converted value.
17975 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
17976 (<a href="#7.22.1.4">7.22.1.4</a>).
17979 <p><small><a href="#Contents">Contents</a></small>
17980 <h5><a name="7.22.1.3" href="#7.22.1.3">7.22.1.3 The strtod, strtof, and strtold functions</a></h5>
17982 <p><a name="7.22.1.3p1" href="#7.22.1.3p1"><small>1</small></a>
17984 #include <a href="#7.22"><stdlib.h></a>
17985 double strtod(const char * restrict nptr,
17986 char ** restrict endptr);
17987 float strtof(const char * restrict nptr,
17988 char ** restrict endptr);
17989 long double strtold(const char * restrict nptr,
17990 char ** restrict endptr);
17992 <p><b>Description</b>
17993 <p><a name="7.22.1.3p2" href="#7.22.1.3p2"><small>2</small></a>
17994 The strtod, strtof, and strtold functions convert the initial portion of the string
17995 pointed to by nptr to double, float, and long double representation,
17996 respectively. First, they decompose the input string into three parts: an initial, possibly
17997 empty, sequence of white-space characters (as specified by the isspace function), a
17998 subject sequence resembling a floating-point constant or representing an infinity or NaN;
17999 and a final string of one or more unrecognized characters, including the terminating null
18000 character of the input string. Then, they attempt to convert the subject sequence to a
18001 floating-point number, and return the result.
18002 <p><a name="7.22.1.3p3" href="#7.22.1.3p3"><small>3</small></a>
18003 The expected form of the subject sequence is an optional plus or minus sign, then one of
18006 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
18007 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
18008 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
18009 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
18010 <li> INF or INFINITY, ignoring case
18011 <li> NAN or NAN(n-char-sequence<sub>opt</sub>), ignoring case in the NAN part, where:
18016 n-char-sequence digit
18017 n-char-sequence nondigit
18020 The subject sequence is defined as the longest initial subsequence of the input string,
18021 starting with the first non-white-space character, that is of the expected form. The subject
18022 sequence contains no characters if the input string is not of the expected form.
18023 <p><a name="7.22.1.3p4" href="#7.22.1.3p4"><small>4</small></a>
18024 If the subject sequence has the expected form for a floating-point number, the sequence of
18025 characters starting with the first digit or the decimal-point character (whichever occurs
18026 first) is interpreted as a floating constant according to the rules of <a href="#6.4.4.2">6.4.4.2</a>, except that the
18028 decimal-point character is used in place of a period, and that if neither an exponent part
18029 nor a decimal-point character appears in a decimal floating point number, or if a binary
18030 exponent part does not appear in a hexadecimal floating point number, an exponent part
18031 of the appropriate type with value zero is assumed to follow the last digit in the string. If
18032 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note292"><b>292)</b></a></sup>
18033 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
18034 the return type, else like a floating constant that is too large for the range of the return
18035 type. A character sequence NAN or NAN(n-char-sequence<sub>opt</sub>) is interpreted as a quiet
18036 NaN, if supported in the return type, else like a subject sequence part that does not have
18037 the expected form; the meaning of the n-char sequence is implementation-defined.<sup><a href="#note293"><b>293)</b></a></sup> A
18038 pointer to the final string is stored in the object pointed to by endptr, provided that
18039 endptr is not a null pointer.
18040 <p><a name="7.22.1.3p5" href="#7.22.1.3p5"><small>5</small></a>
18041 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
18042 value resulting from the conversion is correctly rounded.
18043 <p><a name="7.22.1.3p6" href="#7.22.1.3p6"><small>6</small></a>
18044 In other than the "C" locale, additional locale-specific subject sequence forms may be
18046 <p><a name="7.22.1.3p7" href="#7.22.1.3p7"><small>7</small></a>
18047 If the subject sequence is empty or does not have the expected form, no conversion is
18048 performed; the value of nptr is stored in the object pointed to by endptr, provided
18049 that endptr is not a null pointer.
18050 <p><b>Recommended practice</b>
18051 <p><a name="7.22.1.3p8" href="#7.22.1.3p8"><small>8</small></a>
18052 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
18053 the result is not exactly representable, the result should be one of the two numbers in the
18054 appropriate internal format that are adjacent to the hexadecimal floating source value,
18055 with the extra stipulation that the error should have a correct sign for the current rounding
18057 <p><a name="7.22.1.3p9" href="#7.22.1.3p9"><small>9</small></a>
18058 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
18059 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
18060 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
18061 consider the two bounding, adjacent decimal strings L and U, both having
18062 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
18063 The result should be one of the (equal or adjacent) values that would be obtained by
18064 correctly rounding L and U according to the current rounding direction, with the extra
18067 stipulation that the error with respect to D should have a correct sign for the current
18068 rounding direction.<sup><a href="#note294"><b>294)</b></a></sup>
18070 <p><a name="7.22.1.3p10" href="#7.22.1.3p10"><small>10</small></a>
18071 The functions return the converted value, if any. If no conversion could be performed,
18072 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
18073 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
18074 return type and sign of the value), and the value of the macro ERANGE is stored in
18075 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
18076 no greater than the smallest normalized positive number in the return type; whether
18077 errno acquires the value ERANGE is implementation-defined.
18079 <p><b>Footnotes</b>
18080 <p><small><a name="note292" href="#note292">292)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
18081 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
18082 methods may yield different results if rounding is toward positive or negative infinity. In either case,
18083 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
18085 <p><small><a name="note293" href="#note293">293)</a> An implementation may use the n-char sequence to determine extra information to be represented in
18086 the NaN's significand.
18088 <p><small><a name="note294" href="#note294">294)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
18089 to the same internal floating value, but if not will round to adjacent values.
18092 <p><small><a href="#Contents">Contents</a></small>
18093 <h5><a name="7.22.1.4" href="#7.22.1.4">7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
18095 <p><a name="7.22.1.4p1" href="#7.22.1.4p1"><small>1</small></a>
18097 #include <a href="#7.22"><stdlib.h></a>
18099 const char * restrict nptr,
18100 char ** restrict endptr,
18102 long long int strtoll(
18103 const char * restrict nptr,
18104 char ** restrict endptr,
18106 unsigned long int strtoul(
18107 const char * restrict nptr,
18108 char ** restrict endptr,
18110 unsigned long long int strtoull(
18111 const char * restrict nptr,
18112 char ** restrict endptr,
18115 <p><b>Description</b>
18116 <p><a name="7.22.1.4p2" href="#7.22.1.4p2"><small>2</small></a>
18117 The strtol, strtoll, strtoul, and strtoull functions convert the initial
18118 portion of the string pointed to by nptr to long int, long long int, unsigned
18119 long int, and unsigned long long int representation, respectively. First,
18120 they decompose the input string into three parts: an initial, possibly empty, sequence of
18121 white-space characters (as specified by the isspace function), a subject sequence
18125 resembling an integer represented in some radix determined by the value of base, and a
18126 final string of one or more unrecognized characters, including the terminating null
18127 character of the input string. Then, they attempt to convert the subject sequence to an
18128 integer, and return the result.
18129 <p><a name="7.22.1.4p3" href="#7.22.1.4p3"><small>3</small></a>
18130 If the value of base is zero, the expected form of the subject sequence is that of an
18131 integer constant as described in <a href="#6.4.4.1">6.4.4.1</a>, optionally preceded by a plus or minus sign, but
18132 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
18133 expected form of the subject sequence is a sequence of letters and digits representing an
18134 integer with the radix specified by base, optionally preceded by a plus or minus sign,
18135 but not including an integer suffix. The letters from a (or A) through z (or Z) are
18136 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
18137 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
18138 optionally precede the sequence of letters and digits, following the sign if present.
18139 <p><a name="7.22.1.4p4" href="#7.22.1.4p4"><small>4</small></a>
18140 The subject sequence is defined as the longest initial subsequence of the input string,
18141 starting with the first non-white-space character, that is of the expected form. The subject
18142 sequence contains no characters if the input string is empty or consists entirely of white
18143 space, or if the first non-white-space character is other than a sign or a permissible letter
18145 <p><a name="7.22.1.4p5" href="#7.22.1.4p5"><small>5</small></a>
18146 If the subject sequence has the expected form and the value of base is zero, the sequence
18147 of characters starting with the first digit is interpreted as an integer constant according to
18148 the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the value of base
18149 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
18150 as given above. If the subject sequence begins with a minus sign, the value resulting from
18151 the conversion is negated (in the return type). A pointer to the final string is stored in the
18152 object pointed to by endptr, provided that endptr is not a null pointer.
18153 <p><a name="7.22.1.4p6" href="#7.22.1.4p6"><small>6</small></a>
18154 In other than the "C" locale, additional locale-specific subject sequence forms may be
18156 <p><a name="7.22.1.4p7" href="#7.22.1.4p7"><small>7</small></a>
18157 If the subject sequence is empty or does not have the expected form, no conversion is
18158 performed; the value of nptr is stored in the object pointed to by endptr, provided
18159 that endptr is not a null pointer.
18161 <p><a name="7.22.1.4p8" href="#7.22.1.4p8"><small>8</small></a>
18162 The strtol, strtoll, strtoul, and strtoull functions return the converted
18163 value, if any. If no conversion could be performed, zero is returned. If the correct value
18164 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
18165 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
18166 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
18169 <p><small><a href="#Contents">Contents</a></small>
18170 <h4><a name="7.22.2" href="#7.22.2">7.22.2 Pseudo-random sequence generation functions</a></h4>
18172 <p><small><a href="#Contents">Contents</a></small>
18173 <h5><a name="7.22.2.1" href="#7.22.2.1">7.22.2.1 The rand function</a></h5>
18175 <p><a name="7.22.2.1p1" href="#7.22.2.1p1"><small>1</small></a>
18177 #include <a href="#7.22"><stdlib.h></a>
18180 <p><b>Description</b>
18181 <p><a name="7.22.2.1p2" href="#7.22.2.1p2"><small>2</small></a>
18182 The rand function computes a sequence of pseudo-random integers in the range 0 to
18183 RAND_MAX.<sup><a href="#note295"><b>295)</b></a></sup>
18184 <p><a name="7.22.2.1p3" href="#7.22.2.1p3"><small>3</small></a>
18185 The rand function is not required to avoid data races with other calls to pseudo-random
18186 sequence generation functions. The implementation shall behave as if no library function
18187 calls the rand function.
18189 <p><a name="7.22.2.1p4" href="#7.22.2.1p4"><small>4</small></a>
18190 The rand function returns a pseudo-random integer.
18191 <p><b>Environmental limits</b>
18192 <p><a name="7.22.2.1p5" href="#7.22.2.1p5"><small>5</small></a>
18193 The value of the RAND_MAX macro shall be at least 32767.
18195 <p><b>Footnotes</b>
18196 <p><small><a name="note295" href="#note295">295)</a> There are no guarantees as to the quality of the random sequence produced and some implementations
18197 are known to produce sequences with distressingly non-random low-order bits. Applications with
18198 particular requirements should use a generator that is known to be sufficient for their needs.
18201 <p><small><a href="#Contents">Contents</a></small>
18202 <h5><a name="7.22.2.2" href="#7.22.2.2">7.22.2.2 The srand function</a></h5>
18204 <p><a name="7.22.2.2p1" href="#7.22.2.2p1"><small>1</small></a>
18206 #include <a href="#7.22"><stdlib.h></a>
18207 void srand(unsigned int seed);
18209 <p><b>Description</b>
18210 <p><a name="7.22.2.2p2" href="#7.22.2.2p2"><small>2</small></a>
18211 The srand function uses the argument as a seed for a new sequence of pseudo-random
18212 numbers to be returned by subsequent calls to rand. If srand is then called with the
18213 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
18214 called before any calls to srand have been made, the same sequence shall be generated
18215 as when srand is first called with a seed value of 1.
18216 <p><a name="7.22.2.2p3" href="#7.22.2.2p3"><small>3</small></a>
18217 The srand function is not required to avoid data races with other calls to pseudo-
18218 random sequence generation functions. The implementation shall behave as if no library
18219 function calls the srand function.
18226 <p><a name="7.22.2.2p4" href="#7.22.2.2p4"><small>4</small></a>
18227 The srand function returns no value.
18228 <p><a name="7.22.2.2p5" href="#7.22.2.2p5"><small>5</small></a>
18229 EXAMPLE The following functions define a portable implementation of rand and srand.
18231 static unsigned long int next = 1;
18232 int rand(void) // RAND_MAX assumed to be 32767
18234 next = next * 1103515245 + 12345;
18235 return (unsigned int)(next/65536) % 32768;
18237 void srand(unsigned int seed)
18244 <p><small><a href="#Contents">Contents</a></small>
18245 <h4><a name="7.22.3" href="#7.22.3">7.22.3 Memory management functions</a></h4>
18246 <p><a name="7.22.3p1" href="#7.22.3p1"><small>1</small></a>
18247 The order and contiguity of storage allocated by successive calls to the
18248 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
18249 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
18250 a pointer to any type of object with a fundamental alignment requirement and then used
18251 to access such an object or an array of such objects in the space allocated (until the space
18252 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
18253 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
18254 any other object. The pointer returned points to the start (lowest byte address) of the
18255 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
18256 the space requested is zero, the behavior is implementation-defined: either a null pointer
18257 is returned, or the behavior is as if the size were some nonzero value, except that the
18258 returned pointer shall not be used to access an object.
18259 <p><a name="7.22.3p2" href="#7.22.3p2"><small>2</small></a>
18260 For purposes of determining the existence of a data race, memory allocation functions
18261 behave as though they accessed only memory locations accessible through their
18262 arguments and not other static duration storage. These functions may, however, visibly
18263 modify the storage that they allocate or deallocate. A call to free or realloc that
18264 deallocates a region p of memory synchronizes with any allocation call that allocates all
18265 or part of the region p. This synchronization occurs after any access of p by the
18266 deallocating function, and before any such access by the allocating function.
18268 <p><small><a href="#Contents">Contents</a></small>
18269 <h5><a name="7.22.3.1" href="#7.22.3.1">7.22.3.1 The aligned_alloc function</a></h5>
18271 <p><a name="7.22.3.1p1" href="#7.22.3.1p1"><small>1</small></a>
18274 #include <a href="#7.22"><stdlib.h></a>
18275 void *aligned_alloc(size_t alignment, size_t size);
18277 <p><b>Description</b>
18278 <p><a name="7.22.3.1p2" href="#7.22.3.1p2"><small>2</small></a>
18279 The aligned_alloc function allocates space for an object whose alignment is
18280 specified by alignment, whose size is specified by size, and whose value is
18281 indeterminate. The value of alignment shall be a valid alignment supported by the
18282 implementation and the value of size shall be an integral multiple of alignment.
18284 <p><a name="7.22.3.1p3" href="#7.22.3.1p3"><small>3</small></a>
18285 The aligned_alloc function returns either a null pointer or a pointer to the allocated
18288 <p><small><a href="#Contents">Contents</a></small>
18289 <h5><a name="7.22.3.2" href="#7.22.3.2">7.22.3.2 The calloc function</a></h5>
18291 <p><a name="7.22.3.2p1" href="#7.22.3.2p1"><small>1</small></a>
18293 #include <a href="#7.22"><stdlib.h></a>
18294 void *calloc(size_t nmemb, size_t size);
18296 <p><b>Description</b>
18297 <p><a name="7.22.3.2p2" href="#7.22.3.2p2"><small>2</small></a>
18298 The calloc function allocates space for an array of nmemb objects, each of whose size
18299 is size. The space is initialized to all bits zero.<sup><a href="#note296"><b>296)</b></a></sup>
18301 <p><a name="7.22.3.2p3" href="#7.22.3.2p3"><small>3</small></a>
18302 The calloc function returns either a null pointer or a pointer to the allocated space.
18304 <p><b>Footnotes</b>
18305 <p><small><a name="note296" href="#note296">296)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
18309 <p><small><a href="#Contents">Contents</a></small>
18310 <h5><a name="7.22.3.3" href="#7.22.3.3">7.22.3.3 The free function</a></h5>
18312 <p><a name="7.22.3.3p1" href="#7.22.3.3p1"><small>1</small></a>
18314 #include <a href="#7.22"><stdlib.h></a>
18315 void free(void *ptr);
18317 <p><b>Description</b>
18318 <p><a name="7.22.3.3p2" href="#7.22.3.3p2"><small>2</small></a>
18319 The free function causes the space pointed to by ptr to be deallocated, that is, made
18320 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
18321 the argument does not match a pointer earlier returned by a memory management
18322 function, or if the space has been deallocated by a call to free or realloc, the
18323 behavior is undefined.
18325 <p><a name="7.22.3.3p3" href="#7.22.3.3p3"><small>3</small></a>
18326 The free function returns no value.
18333 <p><small><a href="#Contents">Contents</a></small>
18334 <h5><a name="7.22.3.4" href="#7.22.3.4">7.22.3.4 The malloc function</a></h5>
18336 <p><a name="7.22.3.4p1" href="#7.22.3.4p1"><small>1</small></a>
18338 #include <a href="#7.22"><stdlib.h></a>
18339 void *malloc(size_t size);
18341 <p><b>Description</b>
18342 <p><a name="7.22.3.4p2" href="#7.22.3.4p2"><small>2</small></a>
18343 The malloc function allocates space for an object whose size is specified by size and
18344 whose value is indeterminate.
18346 <p><a name="7.22.3.4p3" href="#7.22.3.4p3"><small>3</small></a>
18347 The malloc function returns either a null pointer or a pointer to the allocated space.
18349 <p><small><a href="#Contents">Contents</a></small>
18350 <h5><a name="7.22.3.5" href="#7.22.3.5">7.22.3.5 The realloc function</a></h5>
18352 <p><a name="7.22.3.5p1" href="#7.22.3.5p1"><small>1</small></a>
18354 #include <a href="#7.22"><stdlib.h></a>
18355 void *realloc(void *ptr, size_t size);
18357 <p><b>Description</b>
18358 <p><a name="7.22.3.5p2" href="#7.22.3.5p2"><small>2</small></a>
18359 The realloc function deallocates the old object pointed to by ptr and returns a
18360 pointer to a new object that has the size specified by size. The contents of the new
18361 object shall be the same as that of the old object prior to deallocation, up to the lesser of
18362 the new and old sizes. Any bytes in the new object beyond the size of the old object have
18363 indeterminate values.
18364 <p><a name="7.22.3.5p3" href="#7.22.3.5p3"><small>3</small></a>
18365 If ptr is a null pointer, the realloc function behaves like the malloc function for the
18366 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
18367 management function, or if the space has been deallocated by a call to the free or
18368 realloc function, the behavior is undefined. If memory for the new object cannot be
18369 allocated, the old object is not deallocated and its value is unchanged.
18371 <p><a name="7.22.3.5p4" href="#7.22.3.5p4"><small>4</small></a>
18372 The realloc function returns a pointer to the new object (which may have the same
18373 value as a pointer to the old object), or a null pointer if the new object could not be
18377 <p><small><a href="#Contents">Contents</a></small>
18378 <h4><a name="7.22.4" href="#7.22.4">7.22.4 Communication with the environment</a></h4>
18380 <p><small><a href="#Contents">Contents</a></small>
18381 <h5><a name="7.22.4.1" href="#7.22.4.1">7.22.4.1 The abort function</a></h5>
18383 <p><a name="7.22.4.1p1" href="#7.22.4.1p1"><small>1</small></a>
18385 #include <a href="#7.22"><stdlib.h></a>
18386 _Noreturn void abort(void);
18388 <p><b>Description</b>
18389 <p><a name="7.22.4.1p2" href="#7.22.4.1p2"><small>2</small></a>
18390 The abort function causes abnormal program termination to occur, unless the signal
18391 SIGABRT is being caught and the signal handler does not return. Whether open streams
18392 with unwritten buffered data are flushed, open streams are closed, or temporary files are
18393 removed is implementation-defined. An implementation-defined form of the status
18394 unsuccessful termination is returned to the host environment by means of the function
18395 call raise(SIGABRT).
18397 <p><a name="7.22.4.1p3" href="#7.22.4.1p3"><small>3</small></a>
18398 The abort function does not return to its caller.
18400 <p><small><a href="#Contents">Contents</a></small>
18401 <h5><a name="7.22.4.2" href="#7.22.4.2">7.22.4.2 The atexit function</a></h5>
18403 <p><a name="7.22.4.2p1" href="#7.22.4.2p1"><small>1</small></a>
18405 #include <a href="#7.22"><stdlib.h></a>
18406 int atexit(void (*func)(void));
18408 <p><b>Description</b>
18409 <p><a name="7.22.4.2p2" href="#7.22.4.2p2"><small>2</small></a>
18410 The atexit function registers the function pointed to by func, to be called without
18411 arguments at normal program termination.<sup><a href="#note297"><b>297)</b></a></sup> It is unspecified whether a call to the
18412 atexit function that does not happen before the exit function is called will succeed.
18413 <p><b>Environmental limits</b>
18414 <p><a name="7.22.4.2p3" href="#7.22.4.2p3"><small>3</small></a>
18415 The implementation shall support the registration of at least 32 functions.
18417 <p><a name="7.22.4.2p4" href="#7.22.4.2p4"><small>4</small></a>
18418 The atexit function returns zero if the registration succeeds, nonzero if it fails.
18419 <p><b> Forward references</b>: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
18420 (<a href="#7.22.4.4">7.22.4.4</a>).
18427 <p><b>Footnotes</b>
18428 <p><small><a name="note297" href="#note297">297)</a> The atexit function registrations are distinct from the at_quick_exit registrations, so
18429 applications may need to call both registration functions with the same argument.
18432 <p><small><a href="#Contents">Contents</a></small>
18433 <h5><a name="7.22.4.3" href="#7.22.4.3">7.22.4.3 The at_quick_exit function</a></h5>
18435 <p><a name="7.22.4.3p1" href="#7.22.4.3p1"><small>1</small></a>
18437 #include <a href="#7.22"><stdlib.h></a>
18438 int at_quick_exit(void (*func)(void));
18440 <p><b>Description</b>
18441 <p><a name="7.22.4.3p2" href="#7.22.4.3p2"><small>2</small></a>
18442 The at_quick_exit function registers the function pointed to by func, to be called
18443 without arguments should quick_exit be called.<sup><a href="#note298"><b>298)</b></a></sup> It is unspecified whether a call to
18444 the at_quick_exit function that does not happen before the quick_exit function
18445 is called will succeed.
18446 <p><b>Environmental limits</b>
18447 <p><a name="7.22.4.3p3" href="#7.22.4.3p3"><small>3</small></a>
18448 The implementation shall support the registration of at least 32 functions.
18450 <p><a name="7.22.4.3p4" href="#7.22.4.3p4"><small>4</small></a>
18451 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
18453 <p><b> Forward references</b>: the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
18455 <p><b>Footnotes</b>
18456 <p><small><a name="note298" href="#note298">298)</a> The at_quick_exit function registrations are distinct from the atexit registrations, so
18457 applications may need to call both registration functions with the same argument.
18460 <p><small><a href="#Contents">Contents</a></small>
18461 <h5><a name="7.22.4.4" href="#7.22.4.4">7.22.4.4 The exit function</a></h5>
18463 <p><a name="7.22.4.4p1" href="#7.22.4.4p1"><small>1</small></a>
18465 #include <a href="#7.22"><stdlib.h></a>
18466 _Noreturn void exit(int status);
18468 <p><b>Description</b>
18469 <p><a name="7.22.4.4p2" href="#7.22.4.4p2"><small>2</small></a>
18470 The exit function causes normal program termination to occur. No functions registered
18471 by the at_quick_exit function are called. If a program calls the exit function
18472 more than once, or calls the quick_exit function in addition to the exit function, the
18473 behavior is undefined.
18474 <p><a name="7.22.4.4p3" href="#7.22.4.4p3"><small>3</small></a>
18475 First, all functions registered by the atexit function are called, in the reverse order of
18476 their registration,<sup><a href="#note299"><b>299)</b></a></sup> except that a function is called after any previously registered
18477 functions that had already been called at the time it was registered. If, during the call to
18478 any such function, a call to the longjmp function is made that would terminate the call
18479 to the registered function, the behavior is undefined.
18484 <p><a name="7.22.4.4p4" href="#7.22.4.4p4"><small>4</small></a>
18485 Next, all open streams with unwritten buffered data are flushed, all open streams are
18486 closed, and all files created by the tmpfile function are removed.
18487 <p><a name="7.22.4.4p5" href="#7.22.4.4p5"><small>5</small></a>
18488 Finally, control is returned to the host environment. If the value of status is zero or
18489 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
18490 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
18491 of the status unsuccessful termination is returned. Otherwise the status returned is
18492 implementation-defined.
18494 <p><a name="7.22.4.4p6" href="#7.22.4.4p6"><small>6</small></a>
18495 The exit function cannot return to its caller.
18497 <p><b>Footnotes</b>
18498 <p><small><a name="note299" href="#note299">299)</a> Each function is called as many times as it was registered, and in the correct order with respect to
18499 other registered functions.
18502 <p><small><a href="#Contents">Contents</a></small>
18503 <h5><a name="7.22.4.5" href="#7.22.4.5">7.22.4.5 The _Exit function</a></h5>
18505 <p><a name="7.22.4.5p1" href="#7.22.4.5p1"><small>1</small></a>
18507 #include <a href="#7.22"><stdlib.h></a>
18508 _Noreturn void _Exit(int status);
18510 <p><b>Description</b>
18511 <p><a name="7.22.4.5p2" href="#7.22.4.5p2"><small>2</small></a>
18512 The _Exit function causes normal program termination to occur and control to be
18513 returned to the host environment. No functions registered by the atexit function, the
18514 at_quick_exit function, or signal handlers registered by the signal function are
18515 called. The status returned to the host environment is determined in the same way as for
18516 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
18517 flushed, open streams are closed, or temporary files are removed is implementation-
18520 <p><a name="7.22.4.5p3" href="#7.22.4.5p3"><small>3</small></a>
18521 The _Exit function cannot return to its caller.
18523 <p><small><a href="#Contents">Contents</a></small>
18524 <h5><a name="7.22.4.6" href="#7.22.4.6">7.22.4.6 The getenv function</a></h5>
18526 <p><a name="7.22.4.6p1" href="#7.22.4.6p1"><small>1</small></a>
18528 #include <a href="#7.22"><stdlib.h></a>
18529 char *getenv(const char *name);
18531 <p><b>Description</b>
18532 <p><a name="7.22.4.6p2" href="#7.22.4.6p2"><small>2</small></a>
18533 The getenv function searches an environment list, provided by the host environment,
18534 for a string that matches the string pointed to by name. The set of environment names
18535 and the method for altering the environment list are implementation-defined. The
18536 getenv function need not avoid data races with other threads of execution that modify
18537 the environment list.<sup><a href="#note300"><b>300)</b></a></sup>
18540 <p><a name="7.22.4.6p3" href="#7.22.4.6p3"><small>3</small></a>
18541 The implementation shall behave as if no library function calls the getenv function.
18543 <p><a name="7.22.4.6p4" href="#7.22.4.6p4"><small>4</small></a>
18544 The getenv function returns a pointer to a string associated with the matched list
18545 member. The string pointed to shall not be modified by the program, but may be
18546 overwritten by a subsequent call to the getenv function. If the specified name cannot
18547 be found, a null pointer is returned.
18549 <p><b>Footnotes</b>
18550 <p><small><a name="note300" href="#note300">300)</a> Many implementations provide non-standard functions that modify the environment list.
18553 <p><small><a href="#Contents">Contents</a></small>
18554 <h5><a name="7.22.4.7" href="#7.22.4.7">7.22.4.7 The quick_exit function</a></h5>
18556 <p><a name="7.22.4.7p1" href="#7.22.4.7p1"><small>1</small></a>
18558 #include <a href="#7.22"><stdlib.h></a>
18559 _Noreturn void quick_exit(int status);
18561 <p><b>Description</b>
18562 <p><a name="7.22.4.7p2" href="#7.22.4.7p2"><small>2</small></a>
18563 The quick_exit function causes normal program termination to occur. No functions
18564 registered by the atexit function or signal handlers registered by the signal function
18565 are called. If a program calls the quick_exit function more than once, or calls the
18566 exit function in addition to the quick_exit function, the behavior is undefined. If a
18567 signal is raised while the quick_exit function is executing, the behavior is undefined.
18568 <p><a name="7.22.4.7p3" href="#7.22.4.7p3"><small>3</small></a>
18569 The quick_exit function first calls all functions registered by the at_quick_exit
18570 function, in the reverse order of their registration,<sup><a href="#note301"><b>301)</b></a></sup> except that a function is called after
18571 any previously registered functions that had already been called at the time it was
18572 registered. If, during the call to any such function, a call to the longjmp function is
18573 made that would terminate the call to the registered function, the behavior is undefined.
18574 <p><a name="7.22.4.7p4" href="#7.22.4.7p4"><small>4</small></a>
18575 Then control is returned to the host environment by means of the function call
18578 <p><a name="7.22.4.7p5" href="#7.22.4.7p5"><small>5</small></a>
18579 The quick_exit function cannot return to its caller.
18581 <p><b>Footnotes</b>
18582 <p><small><a name="note301" href="#note301">301)</a> Each function is called as many times as it was registered, and in the correct order with respect to
18583 other registered functions.
18586 <p><small><a href="#Contents">Contents</a></small>
18587 <h5><a name="7.22.4.8" href="#7.22.4.8">7.22.4.8 The system function</a></h5>
18589 <p><a name="7.22.4.8p1" href="#7.22.4.8p1"><small>1</small></a>
18591 #include <a href="#7.22"><stdlib.h></a>
18592 int system(const char *string);
18594 <p><b>Description</b>
18595 <p><a name="7.22.4.8p2" href="#7.22.4.8p2"><small>2</small></a>
18596 If string is a null pointer, the system function determines whether the host
18597 environment has a command processor. If string is not a null pointer, the system
18600 function passes the string pointed to by string to that command processor to be
18601 executed in a manner which the implementation shall document; this might then cause the
18602 program calling system to behave in a non-conforming manner or to terminate.
18604 <p><a name="7.22.4.8p3" href="#7.22.4.8p3"><small>3</small></a>
18605 If the argument is a null pointer, the system function returns nonzero only if a
18606 command processor is available. If the argument is not a null pointer, and the system
18607 function does return, it returns an implementation-defined value.
18609 <p><small><a href="#Contents">Contents</a></small>
18610 <h4><a name="7.22.5" href="#7.22.5">7.22.5 Searching and sorting utilities</a></h4>
18611 <p><a name="7.22.5p1" href="#7.22.5p1"><small>1</small></a>
18612 These utilities make use of a comparison function to search or sort arrays of unspecified
18613 type. Where an argument declared as size_t nmemb specifies the length of the array
18614 for a function, nmemb can have the value zero on a call to that function; the comparison
18615 function is not called, a search finds no matching element, and sorting performs no
18616 rearrangement. Pointer arguments on such a call shall still have valid values, as described
18617 in <a href="#7.1.4">7.1.4</a>.
18618 <p><a name="7.22.5p2" href="#7.22.5p2"><small>2</small></a>
18619 The implementation shall ensure that the second argument of the comparison function
18620 (when called from bsearch), or both arguments (when called from qsort), are
18621 pointers to elements of the array.<sup><a href="#note302"><b>302)</b></a></sup> The first argument when called from bsearch
18623 <p><a name="7.22.5p3" href="#7.22.5p3"><small>3</small></a>
18624 The comparison function shall not alter the contents of the array. The implementation
18625 may reorder elements of the array between calls to the comparison function, but shall not
18626 alter the contents of any individual element.
18627 <p><a name="7.22.5p4" href="#7.22.5p4"><small>4</small></a>
18628 When the same objects (consisting of size bytes, irrespective of their current positions
18629 in the array) are passed more than once to the comparison function, the results shall be
18630 consistent with one another. That is, for qsort they shall define a total ordering on the
18631 array, and for bsearch the same object shall always compare the same way with the
18633 <p><a name="7.22.5p5" href="#7.22.5p5"><small>5</small></a>
18634 A sequence point occurs immediately before and immediately after each call to the
18635 comparison function, and also between any call to the comparison function and any
18636 movement of the objects passed as arguments to that call.
18643 <p><b>Footnotes</b>
18644 <p><small><a name="note302" href="#note302">302)</a> That is, if the value passed is p, then the following expressions are always nonzero:
18647 ((char *)p - (char *)base) % size == 0
18648 (char *)p >= (char *)base
18649 (char *)p < (char *)base + nmemb * size
18653 <p><small><a href="#Contents">Contents</a></small>
18654 <h5><a name="7.22.5.1" href="#7.22.5.1">7.22.5.1 The bsearch function</a></h5>
18656 <p><a name="7.22.5.1p1" href="#7.22.5.1p1"><small>1</small></a>
18658 #include <a href="#7.22"><stdlib.h></a>
18659 void *bsearch(const void *key, const void *base,
18660 size_t nmemb, size_t size,
18661 int (*compar)(const void *, const void *));
18663 <p><b>Description</b>
18664 <p><a name="7.22.5.1p2" href="#7.22.5.1p2"><small>2</small></a>
18665 The bsearch function searches an array of nmemb objects, the initial element of which
18666 is pointed to by base, for an element that matches the object pointed to by key. The
18667 size of each element of the array is specified by size.
18668 <p><a name="7.22.5.1p3" href="#7.22.5.1p3"><small>3</small></a>
18669 The comparison function pointed to by compar is called with two arguments that point
18670 to the key object and to an array element, in that order. The function shall return an
18671 integer less than, equal to, or greater than zero if the key object is considered,
18672 respectively, to be less than, to match, or to be greater than the array element. The array
18673 shall consist of: all the elements that compare less than, all the elements that compare
18674 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note303"><b>303)</b></a></sup>
18676 <p><a name="7.22.5.1p4" href="#7.22.5.1p4"><small>4</small></a>
18677 The bsearch function returns a pointer to a matching element of the array, or a null
18678 pointer if no match is found. If two elements compare as equal, which element is
18679 matched is unspecified.
18681 <p><b>Footnotes</b>
18682 <p><small><a name="note303" href="#note303">303)</a> In practice, the entire array is sorted according to the comparison function.
18685 <p><small><a href="#Contents">Contents</a></small>
18686 <h5><a name="7.22.5.2" href="#7.22.5.2">7.22.5.2 The qsort function</a></h5>
18688 <p><a name="7.22.5.2p1" href="#7.22.5.2p1"><small>1</small></a>
18690 #include <a href="#7.22"><stdlib.h></a>
18691 void qsort(void *base, size_t nmemb, size_t size,
18692 int (*compar)(const void *, const void *));
18694 <p><b>Description</b>
18695 <p><a name="7.22.5.2p2" href="#7.22.5.2p2"><small>2</small></a>
18696 The qsort function sorts an array of nmemb objects, the initial element of which is
18697 pointed to by base. The size of each object is specified by size.
18698 <p><a name="7.22.5.2p3" href="#7.22.5.2p3"><small>3</small></a>
18699 The contents of the array are sorted into ascending order according to a comparison
18700 function pointed to by compar, which is called with two arguments that point to the
18701 objects being compared. The function shall return an integer less than, equal to, or
18702 greater than zero if the first argument is considered to be respectively less than, equal to,
18703 or greater than the second.
18707 <p><a name="7.22.5.2p4" href="#7.22.5.2p4"><small>4</small></a>
18708 If two elements compare as equal, their order in the resulting sorted array is unspecified.
18710 <p><a name="7.22.5.2p5" href="#7.22.5.2p5"><small>5</small></a>
18711 The qsort function returns no value.
18713 <p><small><a href="#Contents">Contents</a></small>
18714 <h4><a name="7.22.6" href="#7.22.6">7.22.6 Integer arithmetic functions</a></h4>
18716 <p><small><a href="#Contents">Contents</a></small>
18717 <h5><a name="7.22.6.1" href="#7.22.6.1">7.22.6.1 The abs, labs and llabs functions</a></h5>
18719 <p><a name="7.22.6.1p1" href="#7.22.6.1p1"><small>1</small></a>
18721 #include <a href="#7.22"><stdlib.h></a>
18723 long int labs(long int j);
18724 long long int llabs(long long int j);
18726 <p><b>Description</b>
18727 <p><a name="7.22.6.1p2" href="#7.22.6.1p2"><small>2</small></a>
18728 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
18729 result cannot be represented, the behavior is undefined.<sup><a href="#note304"><b>304)</b></a></sup>
18731 <p><a name="7.22.6.1p3" href="#7.22.6.1p3"><small>3</small></a>
18732 The abs, labs, and llabs, functions return the absolute value.
18734 <p><b>Footnotes</b>
18735 <p><small><a name="note304" href="#note304">304)</a> The absolute value of the most negative number cannot be represented in two's complement.
18738 <p><small><a href="#Contents">Contents</a></small>
18739 <h5><a name="7.22.6.2" href="#7.22.6.2">7.22.6.2 The div, ldiv, and lldiv functions</a></h5>
18741 <p><a name="7.22.6.2p1" href="#7.22.6.2p1"><small>1</small></a>
18743 #include <a href="#7.22"><stdlib.h></a>
18744 div_t div(int numer, int denom);
18745 ldiv_t ldiv(long int numer, long int denom);
18746 lldiv_t lldiv(long long int numer, long long int denom);
18748 <p><b>Description</b>
18749 <p><a name="7.22.6.2p2" href="#7.22.6.2p2"><small>2</small></a>
18750 The div, ldiv, and lldiv, functions compute numer / denom and numer %
18751 denom in a single operation.
18753 <p><a name="7.22.6.2p3" href="#7.22.6.2p3"><small>3</small></a>
18754 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
18755 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
18756 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
18757 each of which has the same type as the arguments numer and denom. If either part of
18758 the result cannot be represented, the behavior is undefined.
18765 <p><small><a href="#Contents">Contents</a></small>
18766 <h4><a name="7.22.7" href="#7.22.7">7.22.7 Multibyte/wide character conversion functions</a></h4>
18767 <p><a name="7.22.7p1" href="#7.22.7p1"><small>1</small></a>
18768 The behavior of the multibyte character functions is affected by the LC_CTYPE category
18769 of the current locale. For a state-dependent encoding, each function is placed into its
18770 initial conversion state at program startup and can be returned to that state by a call for
18771 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
18772 other than a null pointer cause the internal conversion state of the function to be altered as
18773 necessary. A call with s as a null pointer causes these functions to return a nonzero value
18774 if encodings have state dependency, and zero otherwise.<sup><a href="#note305"><b>305)</b></a></sup> Changing the LC_CTYPE
18775 category causes the conversion state of these functions to be indeterminate.
18777 <p><b>Footnotes</b>
18778 <p><small><a name="note305" href="#note305">305)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
18779 character codes, but are grouped with an adjacent multibyte character.
18782 <p><small><a href="#Contents">Contents</a></small>
18783 <h5><a name="7.22.7.1" href="#7.22.7.1">7.22.7.1 The mblen function</a></h5>
18785 <p><a name="7.22.7.1p1" href="#7.22.7.1p1"><small>1</small></a>
18787 #include <a href="#7.22"><stdlib.h></a>
18788 int mblen(const char *s, size_t n);
18790 <p><b>Description</b>
18791 <p><a name="7.22.7.1p2" href="#7.22.7.1p2"><small>2</small></a>
18792 If s is not a null pointer, the mblen function determines the number of bytes contained
18793 in the multibyte character pointed to by s. Except that the conversion state of the
18794 mbtowc function is not affected, it is equivalent to
18796 mbtowc((wchar_t *)0, (const char *)0, 0);
18797 mbtowc((wchar_t *)0, s, n);
18799 <p><a name="7.22.7.1p3" href="#7.22.7.1p3"><small>3</small></a>
18800 The implementation shall behave as if no library function calls the mblen function.
18802 <p><a name="7.22.7.1p4" href="#7.22.7.1p4"><small>4</small></a>
18803 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
18804 character encodings, respectively, do or do not have state-dependent encodings. If s is
18805 not a null pointer, the mblen function either returns 0 (if s points to the null character),
18806 or returns the number of bytes that are contained in the multibyte character (if the next n
18807 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
18808 multibyte character).
18809 <p><b> Forward references</b>: the mbtowc function (<a href="#7.22.7.2">7.22.7.2</a>).
18816 <p><small><a href="#Contents">Contents</a></small>
18817 <h5><a name="7.22.7.2" href="#7.22.7.2">7.22.7.2 The mbtowc function</a></h5>
18819 <p><a name="7.22.7.2p1" href="#7.22.7.2p1"><small>1</small></a>
18821 #include <a href="#7.22"><stdlib.h></a>
18822 int mbtowc(wchar_t * restrict pwc,
18823 const char * restrict s,
18826 <p><b>Description</b>
18827 <p><a name="7.22.7.2p2" href="#7.22.7.2p2"><small>2</small></a>
18828 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
18829 the byte pointed to by s to determine the number of bytes needed to complete the next
18830 multibyte character (including any shift sequences). If the function determines that the
18831 next multibyte character is complete and valid, it determines the value of the
18832 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18833 the object pointed to by pwc. If the corresponding wide character is the null wide
18834 character, the function is left in the initial conversion state.
18835 <p><a name="7.22.7.2p3" href="#7.22.7.2p3"><small>3</small></a>
18836 The implementation shall behave as if no library function calls the mbtowc function.
18838 <p><a name="7.22.7.2p4" href="#7.22.7.2p4"><small>4</small></a>
18839 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
18840 character encodings, respectively, do or do not have state-dependent encodings. If s is
18841 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
18842 or returns the number of bytes that are contained in the converted multibyte character (if
18843 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
18844 form a valid multibyte character).
18845 <p><a name="7.22.7.2p5" href="#7.22.7.2p5"><small>5</small></a>
18846 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
18849 <p><small><a href="#Contents">Contents</a></small>
18850 <h5><a name="7.22.7.3" href="#7.22.7.3">7.22.7.3 The wctomb function</a></h5>
18852 <p><a name="7.22.7.3p1" href="#7.22.7.3p1"><small>1</small></a>
18854 #include <a href="#7.22"><stdlib.h></a>
18855 int wctomb(char *s, wchar_t wc);
18857 <p><b>Description</b>
18858 <p><a name="7.22.7.3p2" href="#7.22.7.3p2"><small>2</small></a>
18859 The wctomb function determines the number of bytes needed to represent the multibyte
18860 character corresponding to the wide character given by wc (including any shift
18861 sequences), and stores the multibyte character representation in the array whose first
18862 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
18863 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
18864 sequence needed to restore the initial shift state, and the function is left in the initial
18867 <p><a name="7.22.7.3p3" href="#7.22.7.3p3"><small>3</small></a>
18868 The implementation shall behave as if no library function calls the wctomb function.
18870 <p><a name="7.22.7.3p4" href="#7.22.7.3p4"><small>4</small></a>
18871 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
18872 character encodings, respectively, do or do not have state-dependent encodings. If s is
18873 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
18874 to a valid multibyte character, or returns the number of bytes that are contained in the
18875 multibyte character corresponding to the value of wc.
18876 <p><a name="7.22.7.3p5" href="#7.22.7.3p5"><small>5</small></a>
18877 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
18879 <p><small><a href="#Contents">Contents</a></small>
18880 <h4><a name="7.22.8" href="#7.22.8">7.22.8 Multibyte/wide string conversion functions</a></h4>
18881 <p><a name="7.22.8p1" href="#7.22.8p1"><small>1</small></a>
18882 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
18883 the current locale.
18885 <p><small><a href="#Contents">Contents</a></small>
18886 <h5><a name="7.22.8.1" href="#7.22.8.1">7.22.8.1 The mbstowcs function</a></h5>
18888 <p><a name="7.22.8.1p1" href="#7.22.8.1p1"><small>1</small></a>
18890 #include <a href="#7.22"><stdlib.h></a>
18891 size_t mbstowcs(wchar_t * restrict pwcs,
18892 const char * restrict s,
18895 <p><b>Description</b>
18896 <p><a name="7.22.8.1p2" href="#7.22.8.1p2"><small>2</small></a>
18897 The mbstowcs function converts a sequence of multibyte characters that begins in the
18898 initial shift state from the array pointed to by s into a sequence of corresponding wide
18899 characters and stores not more than n wide characters into the array pointed to by pwcs.
18900 No multibyte characters that follow a null character (which is converted into a null wide
18901 character) will be examined or converted. Each multibyte character is converted as if by
18902 a call to the mbtowc function, except that the conversion state of the mbtowc function is
18904 <p><a name="7.22.8.1p3" href="#7.22.8.1p3"><small>3</small></a>
18905 No more than n elements will be modified in the array pointed to by pwcs. If copying
18906 takes place between objects that overlap, the behavior is undefined.
18908 <p><a name="7.22.8.1p4" href="#7.22.8.1p4"><small>4</small></a>
18909 If an invalid multibyte character is encountered, the mbstowcs function returns
18910 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
18911 elements modified, not including a terminating null wide character, if any.<sup><a href="#note306"><b>306)</b></a></sup>
18918 <p><b>Footnotes</b>
18919 <p><small><a name="note306" href="#note306">306)</a> The array will not be null-terminated if the value returned is n.
18922 <p><small><a href="#Contents">Contents</a></small>
18923 <h5><a name="7.22.8.2" href="#7.22.8.2">7.22.8.2 The wcstombs function</a></h5>
18925 <p><a name="7.22.8.2p1" href="#7.22.8.2p1"><small>1</small></a>
18927 #include <a href="#7.22"><stdlib.h></a>
18928 size_t wcstombs(char * restrict s,
18929 const wchar_t * restrict pwcs,
18932 <p><b>Description</b>
18933 <p><a name="7.22.8.2p2" href="#7.22.8.2p2"><small>2</small></a>
18934 The wcstombs function converts a sequence of wide characters from the array pointed
18935 to by pwcs into a sequence of corresponding multibyte characters that begins in the
18936 initial shift state, and stores these multibyte characters into the array pointed to by s,
18937 stopping if a multibyte character would exceed the limit of n total bytes or if a null
18938 character is stored. Each wide character is converted as if by a call to the wctomb
18939 function, except that the conversion state of the wctomb function is not affected.
18940 <p><a name="7.22.8.2p3" href="#7.22.8.2p3"><small>3</small></a>
18941 No more than n bytes will be modified in the array pointed to by s. If copying takes place
18942 between objects that overlap, the behavior is undefined.
18944 <p><a name="7.22.8.2p4" href="#7.22.8.2p4"><small>4</small></a>
18945 If a wide character is encountered that does not correspond to a valid multibyte character,
18946 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
18947 returns the number of bytes modified, not including a terminating null character, if
18948 any.<sup><a href="#note306"><b>306)</b></a></sup>
18951 <p><small><a href="#Contents">Contents</a></small>
18952 <h3><a name="7.23" href="#7.23">7.23 _Noreturn <stdnoreturn.h></a></h3>
18953 <p><a name="7.23p1" href="#7.23p1"><small>1</small></a>
18954 The header <a href="#7.23"><stdnoreturn.h></a> defines the macro
18958 which expands to _Noreturn.
18961 <p><small><a href="#Contents">Contents</a></small>
18962 <h3><a name="7.24" href="#7.24">7.24 String handling <string.h></a></h3>
18964 <p><small><a href="#Contents">Contents</a></small>
18965 <h4><a name="7.24.1" href="#7.24.1">7.24.1 String function conventions</a></h4>
18966 <p><a name="7.24.1p1" href="#7.24.1p1"><small>1</small></a>
18967 The header <a href="#7.24"><string.h></a> declares one type and several functions, and defines one
18968 macro useful for manipulating arrays of character type and other objects treated as arrays
18969 of character type.<sup><a href="#note307"><b>307)</b></a></sup> The type is size_t and the macro is NULL (both described in
18970 <a href="#7.19">7.19</a>). Various methods are used for determining the lengths of the arrays, but in all cases
18971 a char * or void * argument points to the initial (lowest addressed) character of the
18972 array. If an array is accessed beyond the end of an object, the behavior is undefined.
18973 <p><a name="7.24.1p2" href="#7.24.1p2"><small>2</small></a>
18974 Where an argument declared as size_t n specifies the length of the array for a
18975 function, n can have the value zero on a call to that function. Unless explicitly stated
18976 otherwise in the description of a particular function in this subclause, pointer arguments
18977 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
18978 function that locates a character finds no occurrence, a function that compares two
18979 character sequences returns zero, and a function that copies characters copies zero
18981 <p><a name="7.24.1p3" href="#7.24.1p3"><small>3</small></a>
18982 For all functions in this subclause, each character shall be interpreted as if it had the type
18983 unsigned char (and therefore every possible object representation is valid and has a
18986 <p><b>Footnotes</b>
18987 <p><small><a name="note307" href="#note307">307)</a> See ''future library directions'' (<a href="#7.31.13">7.31.13</a>).
18990 <p><small><a href="#Contents">Contents</a></small>
18991 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Copying functions</a></h4>
18993 <p><small><a href="#Contents">Contents</a></small>
18994 <h5><a name="7.24.2.1" href="#7.24.2.1">7.24.2.1 The memcpy function</a></h5>
18996 <p><a name="7.24.2.1p1" href="#7.24.2.1p1"><small>1</small></a>
18998 #include <a href="#7.24"><string.h></a>
18999 void *memcpy(void * restrict s1,
19000 const void * restrict s2,
19003 <p><b>Description</b>
19004 <p><a name="7.24.2.1p2" href="#7.24.2.1p2"><small>2</small></a>
19005 The memcpy function copies n characters from the object pointed to by s2 into the
19006 object pointed to by s1. If copying takes place between objects that overlap, the behavior
19009 <p><a name="7.24.2.1p3" href="#7.24.2.1p3"><small>3</small></a>
19010 The memcpy function returns the value of s1.
19017 <p><small><a href="#Contents">Contents</a></small>
19018 <h5><a name="7.24.2.2" href="#7.24.2.2">7.24.2.2 The memmove function</a></h5>
19020 <p><a name="7.24.2.2p1" href="#7.24.2.2p1"><small>1</small></a>
19022 #include <a href="#7.24"><string.h></a>
19023 void *memmove(void *s1, const void *s2, size_t n);
19025 <p><b>Description</b>
19026 <p><a name="7.24.2.2p2" href="#7.24.2.2p2"><small>2</small></a>
19027 The memmove function copies n characters from the object pointed to by s2 into the
19028 object pointed to by s1. Copying takes place as if the n characters from the object
19029 pointed to by s2 are first copied into a temporary array of n characters that does not
19030 overlap the objects pointed to by s1 and s2, and then the n characters from the
19031 temporary array are copied into the object pointed to by s1.
19033 <p><a name="7.24.2.2p3" href="#7.24.2.2p3"><small>3</small></a>
19034 The memmove function returns the value of s1.
19036 <p><small><a href="#Contents">Contents</a></small>
19037 <h5><a name="7.24.2.3" href="#7.24.2.3">7.24.2.3 The strcpy function</a></h5>
19039 <p><a name="7.24.2.3p1" href="#7.24.2.3p1"><small>1</small></a>
19041 #include <a href="#7.24"><string.h></a>
19042 char *strcpy(char * restrict s1,
19043 const char * restrict s2);
19045 <p><b>Description</b>
19046 <p><a name="7.24.2.3p2" href="#7.24.2.3p2"><small>2</small></a>
19047 The strcpy function copies the string pointed to by s2 (including the terminating null
19048 character) into the array pointed to by s1. If copying takes place between objects that
19049 overlap, the behavior is undefined.
19051 <p><a name="7.24.2.3p3" href="#7.24.2.3p3"><small>3</small></a>
19052 The strcpy function returns the value of s1.
19054 <p><small><a href="#Contents">Contents</a></small>
19055 <h5><a name="7.24.2.4" href="#7.24.2.4">7.24.2.4 The strncpy function</a></h5>
19057 <p><a name="7.24.2.4p1" href="#7.24.2.4p1"><small>1</small></a>
19059 #include <a href="#7.24"><string.h></a>
19060 char *strncpy(char * restrict s1,
19061 const char * restrict s2,
19064 <p><b>Description</b>
19065 <p><a name="7.24.2.4p2" href="#7.24.2.4p2"><small>2</small></a>
19066 The strncpy function copies not more than n characters (characters that follow a null
19067 character are not copied) from the array pointed to by s2 to the array pointed to by
19069 s1.<sup><a href="#note308"><b>308)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
19070 <p><a name="7.24.2.4p3" href="#7.24.2.4p3"><small>3</small></a>
19071 If the array pointed to by s2 is a string that is shorter than n characters, null characters
19072 are appended to the copy in the array pointed to by s1, until n characters in all have been
19075 <p><a name="7.24.2.4p4" href="#7.24.2.4p4"><small>4</small></a>
19076 The strncpy function returns the value of s1.
19078 <p><b>Footnotes</b>
19079 <p><small><a name="note308" href="#note308">308)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
19080 not be null-terminated.
19083 <p><small><a href="#Contents">Contents</a></small>
19084 <h4><a name="7.24.3" href="#7.24.3">7.24.3 Concatenation functions</a></h4>
19086 <p><small><a href="#Contents">Contents</a></small>
19087 <h5><a name="7.24.3.1" href="#7.24.3.1">7.24.3.1 The strcat function</a></h5>
19089 <p><a name="7.24.3.1p1" href="#7.24.3.1p1"><small>1</small></a>
19091 #include <a href="#7.24"><string.h></a>
19092 char *strcat(char * restrict s1,
19093 const char * restrict s2);
19095 <p><b>Description</b>
19096 <p><a name="7.24.3.1p2" href="#7.24.3.1p2"><small>2</small></a>
19097 The strcat function appends a copy of the string pointed to by s2 (including the
19098 terminating null character) to the end of the string pointed to by s1. The initial character
19099 of s2 overwrites the null character at the end of s1. If copying takes place between
19100 objects that overlap, the behavior is undefined.
19102 <p><a name="7.24.3.1p3" href="#7.24.3.1p3"><small>3</small></a>
19103 The strcat function returns the value of s1.
19105 <p><small><a href="#Contents">Contents</a></small>
19106 <h5><a name="7.24.3.2" href="#7.24.3.2">7.24.3.2 The strncat function</a></h5>
19108 <p><a name="7.24.3.2p1" href="#7.24.3.2p1"><small>1</small></a>
19110 #include <a href="#7.24"><string.h></a>
19111 char *strncat(char * restrict s1,
19112 const char * restrict s2,
19115 <p><b>Description</b>
19116 <p><a name="7.24.3.2p2" href="#7.24.3.2p2"><small>2</small></a>
19117 The strncat function appends not more than n characters (a null character and
19118 characters that follow it are not appended) from the array pointed to by s2 to the end of
19119 the string pointed to by s1. The initial character of s2 overwrites the null character at the
19120 end of s1. A terminating null character is always appended to the result.<sup><a href="#note309"><b>309)</b></a></sup> If copying
19123 takes place between objects that overlap, the behavior is undefined.
19125 <p><a name="7.24.3.2p3" href="#7.24.3.2p3"><small>3</small></a>
19126 The strncat function returns the value of s1.
19127 <p><b> Forward references</b>: the strlen function (<a href="#7.24.6.3">7.24.6.3</a>).
19129 <p><b>Footnotes</b>
19130 <p><small><a name="note309" href="#note309">309)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
19134 <p><small><a href="#Contents">Contents</a></small>
19135 <h4><a name="7.24.4" href="#7.24.4">7.24.4 Comparison functions</a></h4>
19136 <p><a name="7.24.4p1" href="#7.24.4p1"><small>1</small></a>
19137 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
19138 and strncmp is determined by the sign of the difference between the values of the first
19139 pair of characters (both interpreted as unsigned char) that differ in the objects being
19142 <p><small><a href="#Contents">Contents</a></small>
19143 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 The memcmp function</a></h5>
19145 <p><a name="7.24.4.1p1" href="#7.24.4.1p1"><small>1</small></a>
19147 #include <a href="#7.24"><string.h></a>
19148 int memcmp(const void *s1, const void *s2, size_t n);
19150 <p><b>Description</b>
19151 <p><a name="7.24.4.1p2" href="#7.24.4.1p2"><small>2</small></a>
19152 The memcmp function compares the first n characters of the object pointed to by s1 to
19153 the first n characters of the object pointed to by s2.<sup><a href="#note310"><b>310)</b></a></sup>
19155 <p><a name="7.24.4.1p3" href="#7.24.4.1p3"><small>3</small></a>
19156 The memcmp function returns an integer greater than, equal to, or less than zero,
19157 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
19160 <p><b>Footnotes</b>
19161 <p><small><a name="note310" href="#note310">310)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
19162 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
19166 <p><small><a href="#Contents">Contents</a></small>
19167 <h5><a name="7.24.4.2" href="#7.24.4.2">7.24.4.2 The strcmp function</a></h5>
19169 <p><a name="7.24.4.2p1" href="#7.24.4.2p1"><small>1</small></a>
19171 #include <a href="#7.24"><string.h></a>
19172 int strcmp(const char *s1, const char *s2);
19174 <p><b>Description</b>
19175 <p><a name="7.24.4.2p2" href="#7.24.4.2p2"><small>2</small></a>
19176 The strcmp function compares the string pointed to by s1 to the string pointed to by
19179 <p><a name="7.24.4.2p3" href="#7.24.4.2p3"><small>3</small></a>
19180 The strcmp function returns an integer greater than, equal to, or less than zero,
19181 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
19186 <p><small><a href="#Contents">Contents</a></small>
19187 <h5><a name="7.24.4.3" href="#7.24.4.3">7.24.4.3 The strcoll function</a></h5>
19189 <p><a name="7.24.4.3p1" href="#7.24.4.3p1"><small>1</small></a>
19191 #include <a href="#7.24"><string.h></a>
19192 int strcoll(const char *s1, const char *s2);
19194 <p><b>Description</b>
19195 <p><a name="7.24.4.3p2" href="#7.24.4.3p2"><small>2</small></a>
19196 The strcoll function compares the string pointed to by s1 to the string pointed to by
19197 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
19199 <p><a name="7.24.4.3p3" href="#7.24.4.3p3"><small>3</small></a>
19200 The strcoll function returns an integer greater than, equal to, or less than zero,
19201 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
19202 pointed to by s2 when both are interpreted as appropriate to the current locale.
19204 <p><small><a href="#Contents">Contents</a></small>
19205 <h5><a name="7.24.4.4" href="#7.24.4.4">7.24.4.4 The strncmp function</a></h5>
19207 <p><a name="7.24.4.4p1" href="#7.24.4.4p1"><small>1</small></a>
19209 #include <a href="#7.24"><string.h></a>
19210 int strncmp(const char *s1, const char *s2, size_t n);
19212 <p><b>Description</b>
19213 <p><a name="7.24.4.4p2" href="#7.24.4.4p2"><small>2</small></a>
19214 The strncmp function compares not more than n characters (characters that follow a
19215 null character are not compared) from the array pointed to by s1 to the array pointed to
19218 <p><a name="7.24.4.4p3" href="#7.24.4.4p3"><small>3</small></a>
19219 The strncmp function returns an integer greater than, equal to, or less than zero,
19220 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
19221 to, or less than the possibly null-terminated array pointed to by s2.
19223 <p><small><a href="#Contents">Contents</a></small>
19224 <h5><a name="7.24.4.5" href="#7.24.4.5">7.24.4.5 The strxfrm function</a></h5>
19226 <p><a name="7.24.4.5p1" href="#7.24.4.5p1"><small>1</small></a>
19228 #include <a href="#7.24"><string.h></a>
19229 size_t strxfrm(char * restrict s1,
19230 const char * restrict s2,
19233 <p><b>Description</b>
19234 <p><a name="7.24.4.5p2" href="#7.24.4.5p2"><small>2</small></a>
19235 The strxfrm function transforms the string pointed to by s2 and places the resulting
19236 string into the array pointed to by s1. The transformation is such that if the strcmp
19237 function is applied to two transformed strings, it returns a value greater than, equal to, or
19239 less than zero, corresponding to the result of the strcoll function applied to the same
19240 two original strings. No more than n characters are placed into the resulting array
19241 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
19242 be a null pointer. If copying takes place between objects that overlap, the behavior is
19245 <p><a name="7.24.4.5p3" href="#7.24.4.5p3"><small>3</small></a>
19246 The strxfrm function returns the length of the transformed string (not including the
19247 terminating null character). If the value returned is n or more, the contents of the array
19248 pointed to by s1 are indeterminate.
19249 <p><a name="7.24.4.5p4" href="#7.24.4.5p4"><small>4</small></a>
19250 EXAMPLE The value of the following expression is the size of the array needed to hold the
19251 transformation of the string pointed to by s.
19253 1 + strxfrm(NULL, s, 0)
19257 <p><small><a href="#Contents">Contents</a></small>
19258 <h4><a name="7.24.5" href="#7.24.5">7.24.5 Search functions</a></h4>
19260 <p><small><a href="#Contents">Contents</a></small>
19261 <h5><a name="7.24.5.1" href="#7.24.5.1">7.24.5.1 The memchr function</a></h5>
19263 <p><a name="7.24.5.1p1" href="#7.24.5.1p1"><small>1</small></a>
19265 #include <a href="#7.24"><string.h></a>
19266 void *memchr(const void *s, int c, size_t n);
19268 <p><b>Description</b>
19269 <p><a name="7.24.5.1p2" href="#7.24.5.1p2"><small>2</small></a>
19270 The memchr function locates the first occurrence of c (converted to an unsigned
19271 char) in the initial n characters (each interpreted as unsigned char) of the object
19272 pointed to by s. The implementation shall behave as if it reads the characters sequentially
19273 and stops as soon as a matching character is found.
19275 <p><a name="7.24.5.1p3" href="#7.24.5.1p3"><small>3</small></a>
19276 The memchr function returns a pointer to the located character, or a null pointer if the
19277 character does not occur in the object.
19279 <p><small><a href="#Contents">Contents</a></small>
19280 <h5><a name="7.24.5.2" href="#7.24.5.2">7.24.5.2 The strchr function</a></h5>
19282 <p><a name="7.24.5.2p1" href="#7.24.5.2p1"><small>1</small></a>
19284 #include <a href="#7.24"><string.h></a>
19285 char *strchr(const char *s, int c);
19287 <p><b>Description</b>
19288 <p><a name="7.24.5.2p2" href="#7.24.5.2p2"><small>2</small></a>
19289 The strchr function locates the first occurrence of c (converted to a char) in the
19290 string pointed to by s. The terminating null character is considered to be part of the
19294 <p><a name="7.24.5.2p3" href="#7.24.5.2p3"><small>3</small></a>
19295 The strchr function returns a pointer to the located character, or a null pointer if the
19296 character does not occur in the string.
19298 <p><small><a href="#Contents">Contents</a></small>
19299 <h5><a name="7.24.5.3" href="#7.24.5.3">7.24.5.3 The strcspn function</a></h5>
19301 <p><a name="7.24.5.3p1" href="#7.24.5.3p1"><small>1</small></a>
19303 #include <a href="#7.24"><string.h></a>
19304 size_t strcspn(const char *s1, const char *s2);
19306 <p><b>Description</b>
19307 <p><a name="7.24.5.3p2" href="#7.24.5.3p2"><small>2</small></a>
19308 The strcspn function computes the length of the maximum initial segment of the string
19309 pointed to by s1 which consists entirely of characters not from the string pointed to by
19312 <p><a name="7.24.5.3p3" href="#7.24.5.3p3"><small>3</small></a>
19313 The strcspn function returns the length of the segment.
19315 <p><small><a href="#Contents">Contents</a></small>
19316 <h5><a name="7.24.5.4" href="#7.24.5.4">7.24.5.4 The strpbrk function</a></h5>
19318 <p><a name="7.24.5.4p1" href="#7.24.5.4p1"><small>1</small></a>
19320 #include <a href="#7.24"><string.h></a>
19321 char *strpbrk(const char *s1, const char *s2);
19323 <p><b>Description</b>
19324 <p><a name="7.24.5.4p2" href="#7.24.5.4p2"><small>2</small></a>
19325 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
19326 character from the string pointed to by s2.
19328 <p><a name="7.24.5.4p3" href="#7.24.5.4p3"><small>3</small></a>
19329 The strpbrk function returns a pointer to the character, or a null pointer if no character
19330 from s2 occurs in s1.
19332 <p><small><a href="#Contents">Contents</a></small>
19333 <h5><a name="7.24.5.5" href="#7.24.5.5">7.24.5.5 The strrchr function</a></h5>
19335 <p><a name="7.24.5.5p1" href="#7.24.5.5p1"><small>1</small></a>
19337 #include <a href="#7.24"><string.h></a>
19338 char *strrchr(const char *s, int c);
19340 <p><b>Description</b>
19341 <p><a name="7.24.5.5p2" href="#7.24.5.5p2"><small>2</small></a>
19342 The strrchr function locates the last occurrence of c (converted to a char) in the
19343 string pointed to by s. The terminating null character is considered to be part of the
19347 <p><a name="7.24.5.5p3" href="#7.24.5.5p3"><small>3</small></a>
19348 The strrchr function returns a pointer to the character, or a null pointer if c does not
19349 occur in the string.
19351 <p><small><a href="#Contents">Contents</a></small>
19352 <h5><a name="7.24.5.6" href="#7.24.5.6">7.24.5.6 The strspn function</a></h5>
19354 <p><a name="7.24.5.6p1" href="#7.24.5.6p1"><small>1</small></a>
19356 #include <a href="#7.24"><string.h></a>
19357 size_t strspn(const char *s1, const char *s2);
19359 <p><b>Description</b>
19360 <p><a name="7.24.5.6p2" href="#7.24.5.6p2"><small>2</small></a>
19361 The strspn function computes the length of the maximum initial segment of the string
19362 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
19364 <p><a name="7.24.5.6p3" href="#7.24.5.6p3"><small>3</small></a>
19365 The strspn function returns the length of the segment.
19367 <p><small><a href="#Contents">Contents</a></small>
19368 <h5><a name="7.24.5.7" href="#7.24.5.7">7.24.5.7 The strstr function</a></h5>
19370 <p><a name="7.24.5.7p1" href="#7.24.5.7p1"><small>1</small></a>
19372 #include <a href="#7.24"><string.h></a>
19373 char *strstr(const char *s1, const char *s2);
19375 <p><b>Description</b>
19376 <p><a name="7.24.5.7p2" href="#7.24.5.7p2"><small>2</small></a>
19377 The strstr function locates the first occurrence in the string pointed to by s1 of the
19378 sequence of characters (excluding the terminating null character) in the string pointed to
19381 <p><a name="7.24.5.7p3" href="#7.24.5.7p3"><small>3</small></a>
19382 The strstr function returns a pointer to the located string, or a null pointer if the string
19383 is not found. If s2 points to a string with zero length, the function returns s1.
19385 <p><small><a href="#Contents">Contents</a></small>
19386 <h5><a name="7.24.5.8" href="#7.24.5.8">7.24.5.8 The strtok function</a></h5>
19388 <p><a name="7.24.5.8p1" href="#7.24.5.8p1"><small>1</small></a>
19390 #include <a href="#7.24"><string.h></a>
19391 char *strtok(char * restrict s1,
19392 const char * restrict s2);
19394 <p><b>Description</b>
19395 <p><a name="7.24.5.8p2" href="#7.24.5.8p2"><small>2</small></a>
19396 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
19397 sequence of tokens, each of which is delimited by a character from the string pointed to
19398 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
19399 sequence have a null first argument. The separator string pointed to by s2 may be
19400 different from call to call.
19402 <p><a name="7.24.5.8p3" href="#7.24.5.8p3"><small>3</small></a>
19403 The first call in the sequence searches the string pointed to by s1 for the first character
19404 that is not contained in the current separator string pointed to by s2. If no such character
19405 is found, then there are no tokens in the string pointed to by s1 and the strtok function
19406 returns a null pointer. If such a character is found, it is the start of the first token.
19407 <p><a name="7.24.5.8p4" href="#7.24.5.8p4"><small>4</small></a>
19408 The strtok function then searches from there for a character that is contained in the
19409 current separator string. If no such character is found, the current token extends to the
19410 end of the string pointed to by s1, and subsequent searches for a token will return a null
19411 pointer. If such a character is found, it is overwritten by a null character, which
19412 terminates the current token. The strtok function saves a pointer to the following
19413 character, from which the next search for a token will start.
19414 <p><a name="7.24.5.8p5" href="#7.24.5.8p5"><small>5</small></a>
19415 Each subsequent call, with a null pointer as the value of the first argument, starts
19416 searching from the saved pointer and behaves as described above.
19417 <p><a name="7.24.5.8p6" href="#7.24.5.8p6"><small>6</small></a>
19418 The strtok function is not required to avoid data races with other calls to the strtok
19419 function.<sup><a href="#note311"><b>311)</b></a></sup> The implementation shall behave as if no library function calls the strtok
19422 <p><a name="7.24.5.8p7" href="#7.24.5.8p7"><small>7</small></a>
19423 The strtok function returns a pointer to the first character of a token, or a null pointer
19424 if there is no token.
19425 <p><a name="7.24.5.8p8" href="#7.24.5.8p8"><small>8</small></a>
19428 #include <a href="#7.24"><string.h></a>
19429 static char str[] = "?a???b,,,#c";
19431 t = strtok(str, "?"); // t points to the token "a"
19432 t = strtok(NULL, ","); // t points to the token "??b"
19433 t = strtok(NULL, "#,"); // t points to the token "c"
19434 t = strtok(NULL, "?"); // t is a null pointer
19437 <p><b> Forward references</b>: The strtok_s function (<a href="#K.3.7.3.1">K.3.7.3.1</a>).
19444 <p><b>Footnotes</b>
19445 <p><small><a name="note311" href="#note311">311)</a> The strtok_s function can be used instead to avoid data races.
19448 <p><small><a href="#Contents">Contents</a></small>
19449 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Miscellaneous functions</a></h4>
19451 <p><small><a href="#Contents">Contents</a></small>
19452 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 The memset function</a></h5>
19454 <p><a name="7.24.6.1p1" href="#7.24.6.1p1"><small>1</small></a>
19456 #include <a href="#7.24"><string.h></a>
19457 void *memset(void *s, int c, size_t n);
19459 <p><b>Description</b>
19460 <p><a name="7.24.6.1p2" href="#7.24.6.1p2"><small>2</small></a>
19461 The memset function copies the value of c (converted to an unsigned char) into
19462 each of the first n characters of the object pointed to by s.
19464 <p><a name="7.24.6.1p3" href="#7.24.6.1p3"><small>3</small></a>
19465 The memset function returns the value of s.
19467 <p><small><a href="#Contents">Contents</a></small>
19468 <h5><a name="7.24.6.2" href="#7.24.6.2">7.24.6.2 The strerror function</a></h5>
19470 <p><a name="7.24.6.2p1" href="#7.24.6.2p1"><small>1</small></a>
19472 #include <a href="#7.24"><string.h></a>
19473 char *strerror(int errnum);
19475 <p><b>Description</b>
19476 <p><a name="7.24.6.2p2" href="#7.24.6.2p2"><small>2</small></a>
19477 The strerror function maps the number in errnum to a message string. Typically,
19478 the values for errnum come from errno, but strerror shall map any value of type
19480 <p><a name="7.24.6.2p3" href="#7.24.6.2p3"><small>3</small></a>
19481 The strerror function is not required to avoid data races with other calls to the
19482 strerror function.<sup><a href="#note312"><b>312)</b></a></sup> The implementation shall behave as if no library function calls
19483 the strerror function.
19485 <p><a name="7.24.6.2p4" href="#7.24.6.2p4"><small>4</small></a>
19486 The strerror function returns a pointer to the string, the contents of which are locale-
19487 specific. The array pointed to shall not be modified by the program, but may be
19488 overwritten by a subsequent call to the strerror function.
19489 <p><b> Forward references</b>: The strerror_s function (<a href="#K.3.7.4.2">K.3.7.4.2</a>).
19496 <p><b>Footnotes</b>
19497 <p><small><a name="note312" href="#note312">312)</a> The strerror_s function can be used instead to avoid data races.
19500 <p><small><a href="#Contents">Contents</a></small>
19501 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 The strlen function</a></h5>
19503 <p><a name="7.24.6.3p1" href="#7.24.6.3p1"><small>1</small></a>
19505 #include <a href="#7.24"><string.h></a>
19506 size_t strlen(const char *s);
19508 <p><b>Description</b>
19509 <p><a name="7.24.6.3p2" href="#7.24.6.3p2"><small>2</small></a>
19510 The strlen function computes the length of the string pointed to by s.
19512 <p><a name="7.24.6.3p3" href="#7.24.6.3p3"><small>3</small></a>
19513 The strlen function returns the number of characters that precede the terminating null
19517 <p><small><a href="#Contents">Contents</a></small>
19518 <h3><a name="7.25" href="#7.25">7.25 Type-generic math <tgmath.h></a></h3>
19519 <p><a name="7.25p1" href="#7.25p1"><small>1</small></a>
19520 The header <a href="#7.25"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
19521 defines several type-generic macros.
19522 <p><a name="7.25p2" href="#7.25p2"><small>2</small></a>
19523 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
19524 double) suffix, several have one or more parameters whose corresponding real type is
19525 double. For each such function, except modf, there is a corresponding type-generic
19526 macro.<sup><a href="#note313"><b>313)</b></a></sup> The parameters whose corresponding real type is double in the function
19527 synopsis are generic parameters. Use of the macro invokes a function whose
19528 corresponding real type and type domain are determined by the arguments for the generic
19529 parameters.<sup><a href="#note314"><b>314)</b></a></sup>
19530 <p><a name="7.25p3" href="#7.25p3"><small>3</small></a>
19531 Use of the macro invokes a function whose generic parameters have the corresponding
19532 real type determined as follows:
19534 <li> First, if any argument for generic parameters has type long double, the type
19535 determined is long double.
19536 <li> Otherwise, if any argument for generic parameters has type double or is of integer
19537 type, the type determined is double.
19538 <li> Otherwise, the type determined is float.
19540 <p><a name="7.25p4" href="#7.25p4"><small>4</small></a>
19541 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
19542 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
19543 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
19544 corresponding type-generic macro for fabs and cabs is fabs.
19551 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
19552 function function macro
19571 If at least one argument for a generic parameter is complex, then use of the macro invokes
19572 a complex function; otherwise, use of the macro invokes a real function.
19573 <p><a name="7.25p5" href="#7.25p5"><small>5</small></a>
19574 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
19575 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
19576 name as the function. These type-generic macros are:
19578 atan2 fma llround remainder
19579 cbrt fmax log10 remquo
19580 ceil fmin log1p rint
19581 copysign fmod log2 round
19582 erf frexp logb scalbn
19583 erfc hypot lrint scalbln
19584 exp2 ilogb lround tgamma
19585 expm1 ldexp nearbyint trunc
19586 fdim lgamma nextafter
19587 floor llrint nexttoward
19589 If all arguments for generic parameters are real, then use of the macro invokes a real
19590 function; otherwise, use of the macro results in undefined behavior.
19592 <p><a name="7.25p6" href="#7.25p6"><small>6</small></a>
19593 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
19594 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
19595 function. These type-generic macros are:
19600 Use of the macro with any real or complex argument invokes a complex function.
19601 <p><a name="7.25p7" href="#7.25p7"><small>7</small></a>
19602 EXAMPLE With the declarations
19604 #include <a href="#7.25"><tgmath.h></a>
19611 long double complex ldc;
19613 functions invoked by use of type-generic macros are shown in the following table:
19617 exp(n) exp(n), the function
19619 sin(d) sin(d), the function
19623 pow(ldc, f) cpowl(ldc, f)
19624 remainder(n, n) remainder(n, n), the function
19625 nextafter(d, f) nextafter(d, f), the function
19626 nexttoward(f, ld) nexttowardf(f, ld)
19627 copysign(n, ld) copysignl(n, ld)
19628 ceil(fc) undefined behavior
19629 rint(dc) undefined behavior
19630 fmax(ldc, ld) undefined behavior
19631 carg(n) carg(n), the function
19633 creal(d) creal(d), the function
19634 cimag(ld) cimagl(ld)
19636 carg(dc) carg(dc), the function
19637 cproj(ldc) cprojl(ldc)
19640 <p><b>Footnotes</b>
19641 <p><small><a name="note313" href="#note313">313)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
19642 make available the corresponding ordinary function.
19644 <p><small><a name="note314" href="#note314">314)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
19645 the behavior is undefined.
19648 <p><small><a href="#Contents">Contents</a></small>
19649 <h3><a name="7.26" href="#7.26">7.26 Threads <threads.h></a></h3>
19651 <p><small><a href="#Contents">Contents</a></small>
19652 <h4><a name="7.26.1" href="#7.26.1">7.26.1 Introduction</a></h4>
19653 <p><a name="7.26.1p1" href="#7.26.1p1"><small>1</small></a>
19654 The header <a href="#7.26"><threads.h></a> includes the header <a href="#7.27"><time.h></a>, defines macros, and
19655 declares types, enumeration constants, and functions that support multiple threads of
19656 execution.<sup><a href="#note315"><b>315)</b></a></sup>
19657 <p><a name="7.26.1p2" href="#7.26.1p2"><small>2</small></a>
19658 Implementations that define the macro __STDC_NO_THREADS__ need not provide
19659 this header nor support any of its facilities.
19660 <p><a name="7.26.1p3" href="#7.26.1p3"><small>3</small></a>
19665 which expands to _Thread_local;
19669 which expands to a value that can be used to initialize an object of type once_flag;
19672 TSS_DTOR_ITERATIONS
19674 which expands to an integer constant expression representing the maximum number of
19675 times that destructors will be called when a thread terminates.
19676 <p><a name="7.26.1p4" href="#7.26.1p4"><small>4</small></a>
19681 which is a complete object type that holds an identifier for a condition variable;
19685 which is a complete object type that holds an identifier for a thread;
19689 which is a complete object type that holds an identifier for a thread-specific storage
19694 which is a complete object type that holds an identifier for a mutex;
19698 which is the function pointer type void (*)(void*), used for a destructor for a
19699 thread-specific storage pointer;
19707 which is the function pointer type int (*)(void*) that is passed to thrd_create
19708 to create a new thread; and
19712 which is a complete object type that holds a flag for use by call_once.
19713 <p><a name="7.26.1p5" href="#7.26.1p5"><small>5</small></a>
19714 The enumeration constants are
19718 which is passed to mtx_init to create a mutex object that supports neither timeout nor
19723 which is passed to mtx_init to create a mutex object that supports recursive locking;
19727 which is passed to mtx_init to create a mutex object that supports timeout;
19731 which is returned by a timed wait function to indicate that the time specified in the call
19732 was reached without acquiring the requested resource;
19736 which is returned by a function to indicate that the requested operation succeeded;
19740 which is returned by a function to indicate that the requested operation failed because a
19741 resource requested by a test and return function is already in use;
19745 which is returned by a function to indicate that the requested operation failed; and
19749 which is returned by a function to indicate that the requested operation failed because it
19750 was unable to allocate memory.
19751 <p><b> Forward references</b>: date and time (<a href="#7.27">7.27</a>).
19754 <p><b>Footnotes</b>
19755 <p><small><a name="note315" href="#note315">315)</a> See ''future library directions'' (<a href="#7.31.15">7.31.15</a>).
19758 <p><small><a href="#Contents">Contents</a></small>
19759 <h4><a name="7.26.2" href="#7.26.2">7.26.2 Initialization functions</a></h4>
19761 <p><small><a href="#Contents">Contents</a></small>
19762 <h5><a name="7.26.2.1" href="#7.26.2.1">7.26.2.1 The call_once function</a></h5>
19764 <p><a name="7.26.2.1p1" href="#7.26.2.1p1"><small>1</small></a>
19766 #include <a href="#7.26"><threads.h></a>
19767 void call_once(once_flag *flag, void (*func)(void));
19769 <p><b>Description</b>
19770 <p><a name="7.26.2.1p2" href="#7.26.2.1p2"><small>2</small></a>
19771 The call_once function uses the once_flag pointed to by flag to ensure that
19772 func is called exactly once, the first time the call_once function is called with that
19773 value of flag. Completion of an effective call to the call_once function synchronizes
19774 with all subsequent calls to the call_once function with the same value of flag.
19776 <p><a name="7.26.2.1p3" href="#7.26.2.1p3"><small>3</small></a>
19777 The call_once function returns no value.
19779 <p><small><a href="#Contents">Contents</a></small>
19780 <h4><a name="7.26.3" href="#7.26.3">7.26.3 Condition variable functions</a></h4>
19782 <p><small><a href="#Contents">Contents</a></small>
19783 <h5><a name="7.26.3.1" href="#7.26.3.1">7.26.3.1 The cnd_broadcast function</a></h5>
19785 <p><a name="7.26.3.1p1" href="#7.26.3.1p1"><small>1</small></a>
19787 #include <a href="#7.26"><threads.h></a>
19788 int cnd_broadcast(cnd_t *cond);
19790 <p><b>Description</b>
19791 <p><a name="7.26.3.1p2" href="#7.26.3.1p2"><small>2</small></a>
19792 The cnd_broadcast function unblocks all of the threads that are blocked on the
19793 condition variable pointed to by cond at the time of the call. If no threads are blocked
19794 on the condition variable pointed to by cond at the time of the call, the function does
19797 <p><a name="7.26.3.1p3" href="#7.26.3.1p3"><small>3</small></a>
19798 The cnd_broadcast function returns thrd_success on success, or thrd_error
19799 if the request could not be honored.
19801 <p><small><a href="#Contents">Contents</a></small>
19802 <h5><a name="7.26.3.2" href="#7.26.3.2">7.26.3.2 The cnd_destroy function</a></h5>
19804 <p><a name="7.26.3.2p1" href="#7.26.3.2p1"><small>1</small></a>
19806 #include <a href="#7.26"><threads.h></a>
19807 void cnd_destroy(cnd_t *cond);
19809 <p><b>Description</b>
19810 <p><a name="7.26.3.2p2" href="#7.26.3.2p2"><small>2</small></a>
19811 The cnd_destroy function releases all resources used by the condition variable
19812 pointed to by cond. The cnd_destroy function requires that no threads be blocked
19813 waiting for the condition variable pointed to by cond.
19816 <p><a name="7.26.3.2p3" href="#7.26.3.2p3"><small>3</small></a>
19817 The cnd_destroy function returns no value.
19819 <p><small><a href="#Contents">Contents</a></small>
19820 <h5><a name="7.26.3.3" href="#7.26.3.3">7.26.3.3 The cnd_init function</a></h5>
19822 <p><a name="7.26.3.3p1" href="#7.26.3.3p1"><small>1</small></a>
19824 #include <a href="#7.26"><threads.h></a>
19825 int cnd_init(cnd_t *cond);
19827 <p><b>Description</b>
19828 <p><a name="7.26.3.3p2" href="#7.26.3.3p2"><small>2</small></a>
19829 The cnd_init function creates a condition variable. If it succeeds it sets the variable
19830 pointed to by cond to a value that uniquely identifies the newly created condition
19831 variable. A thread that calls cnd_wait on a newly created condition variable will
19834 <p><a name="7.26.3.3p3" href="#7.26.3.3p3"><small>3</small></a>
19835 The cnd_init function returns thrd_success on success, or thrd_nomem if no
19836 memory could be allocated for the newly created condition, or thrd_error if the
19837 request could not be honored.
19839 <p><small><a href="#Contents">Contents</a></small>
19840 <h5><a name="7.26.3.4" href="#7.26.3.4">7.26.3.4 The cnd_signal function</a></h5>
19842 <p><a name="7.26.3.4p1" href="#7.26.3.4p1"><small>1</small></a>
19844 #include <a href="#7.26"><threads.h></a>
19845 int cnd_signal(cnd_t *cond);
19847 <p><b>Description</b>
19848 <p><a name="7.26.3.4p2" href="#7.26.3.4p2"><small>2</small></a>
19849 The cnd_signal function unblocks one of the threads that are blocked on the
19850 condition variable pointed to by cond at the time of the call. If no threads are blocked
19851 on the condition variable at the time of the call, the function does nothing and return
19854 <p><a name="7.26.3.4p3" href="#7.26.3.4p3"><small>3</small></a>
19855 The cnd_signal function returns thrd_success on success or thrd_error if
19856 the request could not be honored.
19858 <p><small><a href="#Contents">Contents</a></small>
19859 <h5><a name="7.26.3.5" href="#7.26.3.5">7.26.3.5 The cnd_timedwait function</a></h5>
19861 <p><a name="7.26.3.5p1" href="#7.26.3.5p1"><small>1</small></a>
19864 #include <a href="#7.26"><threads.h></a>
19865 int cnd_timedwait(cnd_t *restrict cond,
19866 mtx_t *restrict mtx,
19867 const struct timespec *restrict ts);
19869 <p><b>Description</b>
19870 <p><a name="7.26.3.5p2" href="#7.26.3.5p2"><small>2</small></a>
19871 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
19872 endeavors to block until the condition variable pointed to by cond is signaled by a call to
19873 cnd_signal or to cnd_broadcast, or until after the TIME_UTC-based calendar
19874 time pointed to by ts. When the calling thread becomes unblocked it locks the variable
19875 pointed to by mtx before it returns. The cnd_timedwait function requires that the
19876 mutex pointed to by mtx be locked by the calling thread.
19878 <p><a name="7.26.3.5p3" href="#7.26.3.5p3"><small>3</small></a>
19879 The cnd_timedwait function returns thrd_success upon success, or
19880 thrd_timedout if the time specified in the call was reached without acquiring the
19881 requested resource, or thrd_error if the request could not be honored.
19883 <p><small><a href="#Contents">Contents</a></small>
19884 <h5><a name="7.26.3.6" href="#7.26.3.6">7.26.3.6 The cnd_wait function</a></h5>
19886 <p><a name="7.26.3.6p1" href="#7.26.3.6p1"><small>1</small></a>
19888 #include <a href="#7.26"><threads.h></a>
19889 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19891 <p><b>Description</b>
19892 <p><a name="7.26.3.6p2" href="#7.26.3.6p2"><small>2</small></a>
19893 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
19894 to block until the condition variable pointed to by cond is signaled by a call to
19895 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
19896 locks the mutex pointed to by mtx before it returns. The cnd_wait function requires
19897 that the mutex pointed to by mtx be locked by the calling thread.
19899 <p><a name="7.26.3.6p3" href="#7.26.3.6p3"><small>3</small></a>
19900 The cnd_wait function returns thrd_success on success or thrd_error if the
19901 request could not be honored.
19903 <p><small><a href="#Contents">Contents</a></small>
19904 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Mutex functions</a></h4>
19906 <p><small><a href="#Contents">Contents</a></small>
19907 <h5><a name="7.26.4.1" href="#7.26.4.1">7.26.4.1 The mtx_destroy function</a></h5>
19909 <p><a name="7.26.4.1p1" href="#7.26.4.1p1"><small>1</small></a>
19911 #include <a href="#7.26"><threads.h></a>
19912 void mtx_destroy(mtx_t *mtx);
19914 <p><b>Description</b>
19915 <p><a name="7.26.4.1p2" href="#7.26.4.1p2"><small>2</small></a>
19916 The mtx_destroy function releases any resources used by the mutex pointed to by
19917 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
19919 <p><a name="7.26.4.1p3" href="#7.26.4.1p3"><small>3</small></a>
19920 The mtx_destroy function returns no value.
19923 <p><small><a href="#Contents">Contents</a></small>
19924 <h5><a name="7.26.4.2" href="#7.26.4.2">7.26.4.2 The mtx_init function</a></h5>
19926 <p><a name="7.26.4.2p1" href="#7.26.4.2p1"><small>1</small></a>
19928 #include <a href="#7.26"><threads.h></a>
19929 int mtx_init(mtx_t *mtx, int type);
19931 <p><b>Description</b>
19932 <p><a name="7.26.4.2p2" href="#7.26.4.2p2"><small>2</small></a>
19933 The mtx_init function creates a mutex object with properties indicated by type,
19934 which must have one of the six values:
19935 mtx_plain for a simple non-recursive mutex,
19936 mtx_timed for a non-recursive mutex that supports timeout, *
19937 mtx_plain | mtx_recursive for a simple recursive mutex, or
19938 mtx_timed | mtx_recursive for a recursive mutex that supports timeout.
19939 <p><a name="7.26.4.2p3" href="#7.26.4.2p3"><small>3</small></a>
19940 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
19941 uniquely identifies the newly created mutex.
19943 <p><a name="7.26.4.2p4" href="#7.26.4.2p4"><small>4</small></a>
19944 The mtx_init function returns thrd_success on success, or thrd_error if the
19945 request could not be honored.
19947 <p><small><a href="#Contents">Contents</a></small>
19948 <h5><a name="7.26.4.3" href="#7.26.4.3">7.26.4.3 The mtx_lock function</a></h5>
19950 <p><a name="7.26.4.3p1" href="#7.26.4.3p1"><small>1</small></a>
19952 #include <a href="#7.26"><threads.h></a>
19953 int mtx_lock(mtx_t *mtx);
19955 <p><b>Description</b>
19956 <p><a name="7.26.4.3p2" href="#7.26.4.3p2"><small>2</small></a>
19957 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
19958 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
19959 on the same mutex shall synchronize with this operation.
19961 <p><a name="7.26.4.3p3" href="#7.26.4.3p3"><small>3</small></a>
19962 The mtx_lock function returns thrd_success on success, or thrd_error if the *
19963 request could not be honored.
19965 <p><small><a href="#Contents">Contents</a></small>
19966 <h5><a name="7.26.4.4" href="#7.26.4.4">7.26.4.4 The mtx_timedlock function</a></h5>
19968 <p><a name="7.26.4.4p1" href="#7.26.4.4p1"><small>1</small></a>
19971 #include <a href="#7.26"><threads.h></a>
19972 int mtx_timedlock(mtx_t *restrict mtx,
19973 const struct timespec *restrict ts);
19975 <p><b>Description</b>
19976 <p><a name="7.26.4.4p2" href="#7.26.4.4p2"><small>2</small></a>
19977 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
19978 mtx or until after the TIME_UTC-based calendar time pointed to by ts. The specified
19979 mutex shall support timeout. If the operation succeeds, prior calls to mtx_unlock on
19980 the same mutex shall synchronize with this operation.
19982 <p><a name="7.26.4.4p3" href="#7.26.4.4p3"><small>3</small></a>
19983 The mtx_timedlock function returns thrd_success on success, or
19984 thrd_timedout if the time specified was reached without acquiring the requested
19985 resource, or thrd_error if the request could not be honored.
19987 <p><small><a href="#Contents">Contents</a></small>
19988 <h5><a name="7.26.4.5" href="#7.26.4.5">7.26.4.5 The mtx_trylock function</a></h5>
19990 <p><a name="7.26.4.5p1" href="#7.26.4.5p1"><small>1</small></a>
19992 #include <a href="#7.26"><threads.h></a>
19993 int mtx_trylock(mtx_t *mtx);
19995 <p><b>Description</b>
19996 <p><a name="7.26.4.5p2" href="#7.26.4.5p2"><small>2</small></a>
19997 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. If the *
19998 mutex is already locked, the function returns without blocking. If the operation succeeds,
19999 prior calls to mtx_unlock on the same mutex shall synchronize with this operation.
20001 <p><a name="7.26.4.5p3" href="#7.26.4.5p3"><small>3</small></a>
20002 The mtx_trylock function returns thrd_success on success, or thrd_busy if
20003 the resource requested is already in use, or thrd_error if the request could not be
20006 <p><small><a href="#Contents">Contents</a></small>
20007 <h5><a name="7.26.4.6" href="#7.26.4.6">7.26.4.6 The mtx_unlock function</a></h5>
20009 <p><a name="7.26.4.6p1" href="#7.26.4.6p1"><small>1</small></a>
20011 #include <a href="#7.26"><threads.h></a>
20012 int mtx_unlock(mtx_t *mtx);
20014 <p><b>Description</b>
20015 <p><a name="7.26.4.6p2" href="#7.26.4.6p2"><small>2</small></a>
20016 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
20017 by mtx shall be locked by the calling thread.
20019 <p><a name="7.26.4.6p3" href="#7.26.4.6p3"><small>3</small></a>
20020 The mtx_unlock function returns thrd_success on success or thrd_error if
20021 the request could not be honored.
20024 <p><small><a href="#Contents">Contents</a></small>
20025 <h4><a name="7.26.5" href="#7.26.5">7.26.5 Thread functions</a></h4>
20027 <p><small><a href="#Contents">Contents</a></small>
20028 <h5><a name="7.26.5.1" href="#7.26.5.1">7.26.5.1 The thrd_create function</a></h5>
20030 <p><a name="7.26.5.1p1" href="#7.26.5.1p1"><small>1</small></a>
20032 #include <a href="#7.26"><threads.h></a>
20033 int thrd_create(thrd_t *thr, thrd_start_t func,
20036 <p><b>Description</b>
20037 <p><a name="7.26.5.1p2" href="#7.26.5.1p2"><small>2</small></a>
20038 The thrd_create function creates a new thread executing func(arg). If the
20039 thrd_create function succeeds, it sets the object pointed to by thr to the identifier of
20040 the newly created thread. (A thread's identifier may be reused for a different thread once
20041 the original thread has exited and either been detached or joined to another thread.) The
20042 completion of the thrd_create function synchronizes with the beginning of the
20043 execution of the new thread.
20045 <p><a name="7.26.5.1p3" href="#7.26.5.1p3"><small>3</small></a>
20046 The thrd_create function returns thrd_success on success, or thrd_nomem if
20047 no memory could be allocated for the thread requested, or thrd_error if the request
20048 could not be honored.
20050 <p><small><a href="#Contents">Contents</a></small>
20051 <h5><a name="7.26.5.2" href="#7.26.5.2">7.26.5.2 The thrd_current function</a></h5>
20053 <p><a name="7.26.5.2p1" href="#7.26.5.2p1"><small>1</small></a>
20055 #include <a href="#7.26"><threads.h></a>
20056 thrd_t thrd_current(void);
20058 <p><b>Description</b>
20059 <p><a name="7.26.5.2p2" href="#7.26.5.2p2"><small>2</small></a>
20060 The thrd_current function identifies the thread that called it.
20062 <p><a name="7.26.5.2p3" href="#7.26.5.2p3"><small>3</small></a>
20063 The thrd_current function returns the identifier of the thread that called it.
20065 <p><small><a href="#Contents">Contents</a></small>
20066 <h5><a name="7.26.5.3" href="#7.26.5.3">7.26.5.3 The thrd_detach function</a></h5>
20068 <p><a name="7.26.5.3p1" href="#7.26.5.3p1"><small>1</small></a>
20070 #include <a href="#7.26"><threads.h></a>
20071 int thrd_detach(thrd_t thr);
20073 <p><b>Description</b>
20074 <p><a name="7.26.5.3p2" href="#7.26.5.3p2"><small>2</small></a>
20075 The thrd_detach function tells the operating system to dispose of any resources
20076 allocated to the thread identified by thr when that thread terminates. The thread
20077 identified by thr shall not have been previously detached or joined with another thread.
20080 <p><a name="7.26.5.3p3" href="#7.26.5.3p3"><small>3</small></a>
20081 The thrd_detach function returns thrd_success on success or thrd_error if
20082 the request could not be honored.
20084 <p><small><a href="#Contents">Contents</a></small>
20085 <h5><a name="7.26.5.4" href="#7.26.5.4">7.26.5.4 The thrd_equal function</a></h5>
20087 <p><a name="7.26.5.4p1" href="#7.26.5.4p1"><small>1</small></a>
20089 #include <a href="#7.26"><threads.h></a>
20090 int thrd_equal(thrd_t thr0, thrd_t thr1);
20092 <p><b>Description</b>
20093 <p><a name="7.26.5.4p2" href="#7.26.5.4p2"><small>2</small></a>
20094 The thrd_equal function will determine whether the thread identified by thr0 refers
20095 to the thread identified by thr1.
20097 <p><a name="7.26.5.4p3" href="#7.26.5.4p3"><small>3</small></a>
20098 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
20099 different threads. Otherwise the thrd_equal function returns a nonzero value.
20101 <p><small><a href="#Contents">Contents</a></small>
20102 <h5><a name="7.26.5.5" href="#7.26.5.5">7.26.5.5 The thrd_exit function</a></h5>
20104 <p><a name="7.26.5.5p1" href="#7.26.5.5p1"><small>1</small></a>
20106 #include <a href="#7.26"><threads.h></a>
20107 _Noreturn void thrd_exit(int res);
20109 <p><b>Description</b>
20110 <p><a name="7.26.5.5p2" href="#7.26.5.5p2"><small>2</small></a>
20111 The thrd_exit function terminates execution of the calling thread and sets its result
20113 <p><a name="7.26.5.5p3" href="#7.26.5.5p3"><small>3</small></a>
20114 The program shall terminate normally after the last thread has been terminated. The
20115 behavior shall be as if the program called the exit function with the status
20116 EXIT_SUCCESS at thread termination time.
20118 <p><a name="7.26.5.5p4" href="#7.26.5.5p4"><small>4</small></a>
20119 The thrd_exit function returns no value.
20121 <p><small><a href="#Contents">Contents</a></small>
20122 <h5><a name="7.26.5.6" href="#7.26.5.6">7.26.5.6 The thrd_join function</a></h5>
20124 <p><a name="7.26.5.6p1" href="#7.26.5.6p1"><small>1</small></a>
20126 #include <a href="#7.26"><threads.h></a>
20127 int thrd_join(thrd_t thr, int *res);
20129 <p><b>Description</b>
20130 <p><a name="7.26.5.6p2" href="#7.26.5.6p2"><small>2</small></a>
20131 The thrd_join function joins the thread identified by thr with the current thread by
20132 blocking until the other thread has terminated. If the parameter res is not a null pointer,
20133 it stores the thread's result code in the integer pointed to by res. The termination of the
20135 other thread synchronizes with the completion of the thrd_join function. The thread
20136 identified by thr shall not have been previously detached or joined with another thread.
20138 <p><a name="7.26.5.6p3" href="#7.26.5.6p3"><small>3</small></a>
20139 The thrd_join function returns thrd_success on success or thrd_error if the
20140 request could not be honored.
20142 <p><small><a href="#Contents">Contents</a></small>
20143 <h5><a name="7.26.5.7" href="#7.26.5.7">7.26.5.7 The thrd_sleep function</a></h5>
20145 <p><a name="7.26.5.7p1" href="#7.26.5.7p1"><small>1</small></a>
20147 #include <a href="#7.26"><threads.h></a>
20148 int thrd_sleep(const struct timespec *duration,
20149 struct timespec *remaining);
20151 <p><b>Description</b>
20152 <p><a name="7.26.5.7p2" href="#7.26.5.7p2"><small>2</small></a>
20153 The thrd_sleep function suspends execution of the calling thread until either the
20154 interval specified by duration has elapsed or a signal which is not being ignored is
20155 received. If interrupted by a signal and the remaining argument is not null, the
20156 amount of time remaining (the requested interval minus the time actually slept) is stored
20157 in the interval it points to. The duration and remaining arguments may point to the
20159 <p><a name="7.26.5.7p3" href="#7.26.5.7p3"><small>3</small></a>
20160 The suspension time may be longer than requested because the interval is rounded up to
20161 an integer multiple of the sleep resolution or because of the scheduling of other activity
20162 by the system. But, except for the case of being interrupted by a signal, the suspension
20163 time shall not be less than that specified, as measured by the system clock TIME_UTC.
20165 <p><a name="7.26.5.7p4" href="#7.26.5.7p4"><small>4</small></a>
20166 The thrd_sleep function returns zero if the requested time has elapsed, -1 if it has
20167 been interrupted by a signal, or a negative value if it fails.
20169 <p><small><a href="#Contents">Contents</a></small>
20170 <h5><a name="7.26.5.8" href="#7.26.5.8">7.26.5.8 The thrd_yield function</a></h5>
20172 <p><a name="7.26.5.8p1" href="#7.26.5.8p1"><small>1</small></a>
20174 #include <a href="#7.26"><threads.h></a>
20175 void thrd_yield(void);
20177 <p><b>Description</b>
20178 <p><a name="7.26.5.8p2" href="#7.26.5.8p2"><small>2</small></a>
20179 The thrd_yield function endeavors to permit other threads to run, even if the current
20180 thread would ordinarily continue to run.
20182 <p><a name="7.26.5.8p3" href="#7.26.5.8p3"><small>3</small></a>
20183 The thrd_yield function returns no value.
20186 <p><small><a href="#Contents">Contents</a></small>
20187 <h4><a name="7.26.6" href="#7.26.6">7.26.6 Thread-specific storage functions</a></h4>
20189 <p><small><a href="#Contents">Contents</a></small>
20190 <h5><a name="7.26.6.1" href="#7.26.6.1">7.26.6.1 The tss_create function</a></h5>
20192 <p><a name="7.26.6.1p1" href="#7.26.6.1p1"><small>1</small></a>
20194 #include <a href="#7.26"><threads.h></a>
20195 int tss_create(tss_t *key, tss_dtor_t dtor);
20197 <p><b>Description</b>
20198 <p><a name="7.26.6.1p2" href="#7.26.6.1p2"><small>2</small></a>
20199 The tss_create function creates a thread-specific storage pointer with destructor
20200 dtor, which may be null.
20202 <p><a name="7.26.6.1p3" href="#7.26.6.1p3"><small>3</small></a>
20203 If the tss_create function is successful, it sets the thread-specific storage pointed to
20204 by key to a value that uniquely identifies the newly created pointer and returns
20205 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
20206 pointed to by key is set to an undefined value.
20208 <p><small><a href="#Contents">Contents</a></small>
20209 <h5><a name="7.26.6.2" href="#7.26.6.2">7.26.6.2 The tss_delete function</a></h5>
20211 <p><a name="7.26.6.2p1" href="#7.26.6.2p1"><small>1</small></a>
20213 #include <a href="#7.26"><threads.h></a>
20214 void tss_delete(tss_t key);
20216 <p><b>Description</b>
20217 <p><a name="7.26.6.2p2" href="#7.26.6.2p2"><small>2</small></a>
20218 The tss_delete function releases any resources used by the thread-specific storage
20221 <p><a name="7.26.6.2p3" href="#7.26.6.2p3"><small>3</small></a>
20222 The tss_delete function returns no value.
20224 <p><small><a href="#Contents">Contents</a></small>
20225 <h5><a name="7.26.6.3" href="#7.26.6.3">7.26.6.3 The tss_get function</a></h5>
20227 <p><a name="7.26.6.3p1" href="#7.26.6.3p1"><small>1</small></a>
20229 #include <a href="#7.26"><threads.h></a>
20230 void *tss_get(tss_t key);
20232 <p><b>Description</b>
20233 <p><a name="7.26.6.3p2" href="#7.26.6.3p2"><small>2</small></a>
20234 The tss_get function returns the value for the current thread held in the thread-specific
20235 storage identified by key.
20237 <p><a name="7.26.6.3p3" href="#7.26.6.3p3"><small>3</small></a>
20238 The tss_get function returns the value for the current thread if successful, or zero if
20242 <p><small><a href="#Contents">Contents</a></small>
20243 <h5><a name="7.26.6.4" href="#7.26.6.4">7.26.6.4 The tss_set function</a></h5>
20245 <p><a name="7.26.6.4p1" href="#7.26.6.4p1"><small>1</small></a>
20247 #include <a href="#7.26"><threads.h></a>
20248 int tss_set(tss_t key, void *val);
20250 <p><b>Description</b>
20251 <p><a name="7.26.6.4p2" href="#7.26.6.4p2"><small>2</small></a>
20252 The tss_set function sets the value for the current thread held in the thread-specific
20253 storage identified by key to val.
20255 <p><a name="7.26.6.4p3" href="#7.26.6.4p3"><small>3</small></a>
20256 The tss_set function returns thrd_success on success or thrd_error if the
20257 request could not be honored. *
20260 <p><small><a href="#Contents">Contents</a></small>
20261 <h3><a name="7.27" href="#7.27">7.27 Date and time <time.h></a></h3>
20263 <p><small><a href="#Contents">Contents</a></small>
20264 <h4><a name="7.27.1" href="#7.27.1">7.27.1 Components of time</a></h4>
20265 <p><a name="7.27.1p1" href="#7.27.1p1"><small>1</small></a>
20266 The header <a href="#7.27"><time.h></a> defines two macros, and declares several types and functions for
20267 manipulating time. Many functions deal with a calendar time that represents the current
20268 date (according to the Gregorian calendar) and time. Some functions deal with local
20269 time, which is the calendar time expressed for some specific time zone, and with Daylight
20270 Saving Time, which is a temporary change in the algorithm for determining local time.
20271 The local time zone and Daylight Saving Time are implementation-defined.
20272 <p><a name="7.27.1p2" href="#7.27.1p2"><small>2</small></a>
20273 The macros defined are NULL (described in <a href="#7.19">7.19</a>); *
20277 which expands to an expression with type clock_t (described below) that is the
20278 number per second of the value returned by the clock function; and
20282 which expands to an integer constant greater than 0 that designates the UTC time
20283 base.<sup><a href="#note316"><b>316)</b></a></sup>
20284 <p><a name="7.27.1p3" href="#7.27.1p3"><small>3</small></a>
20285 The types declared are size_t (described in <a href="#7.19">7.19</a>);
20293 which are real types capable of representing times;
20297 which holds an interval specified in seconds and nanoseconds (which may represent a
20298 calendar time based on a particular epoch); and
20302 which holds the components of a calendar time, called the broken-down time.
20303 <p><a name="7.27.1p4" href="#7.27.1p4"><small>4</small></a>
20304 The range and precision of times representable in clock_t and time_t are
20305 implementation-defined. The timespec structure shall contain at least the following
20306 members, in any order.<sup><a href="#note317"><b>317)</b></a></sup>
20312 time_t tv_sec; // whole seconds -- >= 0
20313 long tv_nsec; // nanoseconds -- [0, 999999999]
20315 The tm structure shall contain at least the following members, in any order. The
20316 semantics of the members and their normal ranges are expressed in the comments.<sup><a href="#note318"><b>318)</b></a></sup>
20318 int tm_sec; // seconds after the minute -- [0, 60]
20319 int tm_min; // minutes after the hour -- [0, 59]
20320 int tm_hour; // hours since midnight -- [0, 23]
20321 int tm_mday; // day of the month -- [1, 31]
20322 int tm_mon; // months since January -- [0, 11]
20323 int tm_year; // years since 1900
20324 int tm_wday; // days since Sunday -- [0, 6]
20325 int tm_yday; // days since January 1 -- [0, 365]
20326 int tm_isdst; // Daylight Saving Time flag
20328 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
20329 Saving Time is not in effect, and negative if the information is not available.
20331 <p><b>Footnotes</b>
20332 <p><small><a name="note316" href="#note316">316)</a> Implementations may define additional time bases, but are only required to support a real time clock
20335 <p><small><a name="note317" href="#note317">317)</a> The tv_sec member is a linear count of seconds and may not have the normal semantics of a
20336 time_t. The semantics of the members and their normal ranges are expressed in the comments.
20338 <p><small><a name="note318" href="#note318">318)</a> The range [0, 60] for tm_sec allows for a positive leap second.
20341 <p><small><a href="#Contents">Contents</a></small>
20342 <h4><a name="7.27.2" href="#7.27.2">7.27.2 Time manipulation functions</a></h4>
20344 <p><small><a href="#Contents">Contents</a></small>
20345 <h5><a name="7.27.2.1" href="#7.27.2.1">7.27.2.1 The clock function</a></h5>
20347 <p><a name="7.27.2.1p1" href="#7.27.2.1p1"><small>1</small></a>
20349 #include <a href="#7.27"><time.h></a>
20350 clock_t clock(void);
20352 <p><b>Description</b>
20353 <p><a name="7.27.2.1p2" href="#7.27.2.1p2"><small>2</small></a>
20354 The clock function determines the processor time used.
20356 <p><a name="7.27.2.1p3" href="#7.27.2.1p3"><small>3</small></a>
20357 The clock function returns the implementation's best approximation to the processor
20358 time used by the program since the beginning of an implementation-defined era related
20359 only to the program invocation. To determine the time in seconds, the value returned by
20360 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
20361 the processor time used is not available or its value cannot be represented, the function
20362 returns the value (clock_t)(-1).<sup><a href="#note319"><b>319)</b></a></sup>
20369 <p><b>Footnotes</b>
20370 <p><small><a name="note319" href="#note319">319)</a> In order to measure the time spent in a program, the clock function should be called at the start of
20371 the program and its return value subtracted from the value returned by subsequent calls.
20374 <p><small><a href="#Contents">Contents</a></small>
20375 <h5><a name="7.27.2.2" href="#7.27.2.2">7.27.2.2 The difftime function</a></h5>
20377 <p><a name="7.27.2.2p1" href="#7.27.2.2p1"><small>1</small></a>
20379 #include <a href="#7.27"><time.h></a>
20380 double difftime(time_t time1, time_t time0);
20382 <p><b>Description</b>
20383 <p><a name="7.27.2.2p2" href="#7.27.2.2p2"><small>2</small></a>
20384 The difftime function computes the difference between two calendar times: time1 -
20387 <p><a name="7.27.2.2p3" href="#7.27.2.2p3"><small>3</small></a>
20388 The difftime function returns the difference expressed in seconds as a double.
20390 <p><small><a href="#Contents">Contents</a></small>
20391 <h5><a name="7.27.2.3" href="#7.27.2.3">7.27.2.3 The mktime function</a></h5>
20393 <p><a name="7.27.2.3p1" href="#7.27.2.3p1"><small>1</small></a>
20395 #include <a href="#7.27"><time.h></a>
20396 time_t mktime(struct tm *timeptr);
20398 <p><b>Description</b>
20399 <p><a name="7.27.2.3p2" href="#7.27.2.3p2"><small>2</small></a>
20400 The mktime function converts the broken-down time, expressed as local time, in the
20401 structure pointed to by timeptr into a calendar time value with the same encoding as
20402 that of the values returned by the time function. The original values of the tm_wday
20403 and tm_yday components of the structure are ignored, and the original values of the
20404 other components are not restricted to the ranges indicated above.<sup><a href="#note320"><b>320)</b></a></sup> On successful
20405 completion, the values of the tm_wday and tm_yday components of the structure are
20406 set appropriately, and the other components are set to represent the specified calendar
20407 time, but with their values forced to the ranges indicated above; the final value of
20408 tm_mday is not set until tm_mon and tm_year are determined.
20410 <p><a name="7.27.2.3p3" href="#7.27.2.3p3"><small>3</small></a>
20411 The mktime function returns the specified calendar time encoded as a value of type
20412 time_t. If the calendar time cannot be represented, the function returns the value
20414 <p><a name="7.27.2.3p4" href="#7.27.2.3p4"><small>4</small></a>
20415 EXAMPLE What day of the week is July 4, 2001?
20422 #include <a href="#7.21"><stdio.h></a>
20423 #include <a href="#7.27"><time.h></a>
20424 static const char *const wday[] = {
20425 "Sunday", "Monday", "Tuesday", "Wednesday",
20426 "Thursday", "Friday", "Saturday", "-unknown-"
20428 struct tm time_str;
20430 time_str.tm_year = 2001 - 1900;
20431 time_str.tm_mon = 7 - 1;
20432 time_str.tm_mday = 4;
20433 time_str.tm_hour = 0;
20434 time_str.tm_min = 0;
20435 time_str.tm_sec = 1;
20436 time_str.tm_isdst = -1;
20437 if (mktime(&time_str) == (time_t)(-1))
20438 time_str.tm_wday = 7;
20439 printf("%s\n", wday[time_str.tm_wday]);
20443 <p><b>Footnotes</b>
20444 <p><small><a name="note320" href="#note320">320)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
20445 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
20446 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
20449 <p><small><a href="#Contents">Contents</a></small>
20450 <h5><a name="7.27.2.4" href="#7.27.2.4">7.27.2.4 The time function</a></h5>
20452 <p><a name="7.27.2.4p1" href="#7.27.2.4p1"><small>1</small></a>
20454 #include <a href="#7.27"><time.h></a>
20455 time_t time(time_t *timer);
20457 <p><b>Description</b>
20458 <p><a name="7.27.2.4p2" href="#7.27.2.4p2"><small>2</small></a>
20459 The time function determines the current calendar time. The encoding of the value is
20462 <p><a name="7.27.2.4p3" href="#7.27.2.4p3"><small>3</small></a>
20463 The time function returns the implementation's best approximation to the current
20464 calendar time. The value (time_t)(-1) is returned if the calendar time is not
20465 available. If timer is not a null pointer, the return value is also assigned to the object it
20468 <p><small><a href="#Contents">Contents</a></small>
20469 <h5><a name="7.27.2.5" href="#7.27.2.5">7.27.2.5 The timespec_get function</a></h5>
20471 <p><a name="7.27.2.5p1" href="#7.27.2.5p1"><small>1</small></a>
20473 #include <a href="#7.27"><time.h></a>
20474 int timespec_get(struct timespec *ts, int base);
20476 <p><b>Description</b>
20477 <p><a name="7.27.2.5p2" href="#7.27.2.5p2"><small>2</small></a>
20478 The timespec_get function sets the interval pointed to by ts to hold the current
20479 calendar time based on the specified time base.
20480 <p><a name="7.27.2.5p3" href="#7.27.2.5p3"><small>3</small></a>
20481 If base is TIME_UTC, the tv_sec member is set to the number of seconds since an
20482 implementation defined epoch, truncated to a whole value and the tv_nsec member is
20483 set to the integral number of nanoseconds, rounded to the resolution of the system
20485 clock.<sup><a href="#note321"><b>321)</b></a></sup>
20487 <p><a name="7.27.2.5p4" href="#7.27.2.5p4"><small>4</small></a>
20488 If the timespec_get function is successful it returns the nonzero value base;
20489 otherwise, it returns zero.
20491 <p><b>Footnotes</b>
20492 <p><small><a name="note321" href="#note321">321)</a> Although a struct timespec object describes times with nanosecond resolution, the available
20493 resolution is system dependent and may even be greater than 1 second.
20496 <p><small><a href="#Contents">Contents</a></small>
20497 <h4><a name="7.27.3" href="#7.27.3">7.27.3 Time conversion functions</a></h4>
20498 <p><a name="7.27.3p1" href="#7.27.3p1"><small>1</small></a>
20499 Except for the strftime function, these functions each return a pointer to one of two
20500 types of static objects: a broken-down time structure or an array of char. Execution of
20501 any of the functions that return a pointer to one of these object types may overwrite the
20502 information in any object of the same type pointed to by the value returned from any
20503 previous call to any of them and the functions are not required to avoid data races with
20504 each other.<sup><a href="#note322"><b>322)</b></a></sup> The implementation shall behave as if no other library functions call these
20507 <p><b>Footnotes</b>
20508 <p><small><a name="note322" href="#note322">322)</a> Alternative time conversion functions that do avoid data races are specified in <a href="#K.3.8.2">K.3.8.2</a>.
20511 <p><small><a href="#Contents">Contents</a></small>
20512 <h5><a name="7.27.3.1" href="#7.27.3.1">7.27.3.1 The asctime function</a></h5>
20514 <p><a name="7.27.3.1p1" href="#7.27.3.1p1"><small>1</small></a>
20516 #include <a href="#7.27"><time.h></a>
20517 char *asctime(const struct tm *timeptr);
20519 <p><b>Description</b>
20520 <p><a name="7.27.3.1p2" href="#7.27.3.1p2"><small>2</small></a>
20521 The asctime function converts the broken-down time in the structure pointed to by
20522 timeptr into a string in the form
20524 Sun Sep 16 01:03:52 1973\n\0
20526 using the equivalent of the following algorithm.
20527 char *asctime(const struct tm *timeptr)
20530 static const char wday_name[7][3] = {
20531 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
20533 static const char mon_name[12][3] = {
20534 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
20535 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
20537 static char result[26];
20544 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
20545 wday_name[timeptr->tm_wday],
20546 mon_name[timeptr->tm_mon],
20547 timeptr->tm_mday, timeptr->tm_hour,
20548 timeptr->tm_min, timeptr->tm_sec,
20549 1900 + timeptr->tm_year);
20553 <p><a name="7.27.3.1p3" href="#7.27.3.1p3"><small>3</small></a>
20554 If any of the members of the broken-down time contain values that are outside their
20555 normal ranges,<sup><a href="#note323"><b>323)</b></a></sup> the behavior of the asctime function is undefined. Likewise, if the
20556 calculated year exceeds four digits or is less than the year 1000, the behavior is
20559 <p><a name="7.27.3.1p4" href="#7.27.3.1p4"><small>4</small></a>
20560 The asctime function returns a pointer to the string.
20562 <p><b>Footnotes</b>
20563 <p><small><a name="note323" href="#note323">323)</a> See <a href="#7.27.1">7.27.1</a>.
20566 <p><small><a href="#Contents">Contents</a></small>
20567 <h5><a name="7.27.3.2" href="#7.27.3.2">7.27.3.2 The ctime function</a></h5>
20569 <p><a name="7.27.3.2p1" href="#7.27.3.2p1"><small>1</small></a>
20571 #include <a href="#7.27"><time.h></a>
20572 char *ctime(const time_t *timer);
20574 <p><b>Description</b>
20575 <p><a name="7.27.3.2p2" href="#7.27.3.2p2"><small>2</small></a>
20576 The ctime function converts the calendar time pointed to by timer to local time in the
20577 form of a string. It is equivalent to
20579 asctime(localtime(timer))
20582 <p><a name="7.27.3.2p3" href="#7.27.3.2p3"><small>3</small></a>
20583 The ctime function returns the pointer returned by the asctime function with that
20584 broken-down time as argument.
20585 <p><b> Forward references</b>: the localtime function (<a href="#7.27.3.4">7.27.3.4</a>).
20587 <p><small><a href="#Contents">Contents</a></small>
20588 <h5><a name="7.27.3.3" href="#7.27.3.3">7.27.3.3 The gmtime function</a></h5>
20590 <p><a name="7.27.3.3p1" href="#7.27.3.3p1"><small>1</small></a>
20592 #include <a href="#7.27"><time.h></a>
20593 struct tm *gmtime(const time_t *timer);
20600 <p><b>Description</b>
20601 <p><a name="7.27.3.3p2" href="#7.27.3.3p2"><small>2</small></a>
20602 The gmtime function converts the calendar time pointed to by timer into a broken-
20603 down time, expressed as UTC.
20605 <p><a name="7.27.3.3p3" href="#7.27.3.3p3"><small>3</small></a>
20606 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
20607 specified time cannot be converted to UTC.
20609 <p><small><a href="#Contents">Contents</a></small>
20610 <h5><a name="7.27.3.4" href="#7.27.3.4">7.27.3.4 The localtime function</a></h5>
20612 <p><a name="7.27.3.4p1" href="#7.27.3.4p1"><small>1</small></a>
20614 #include <a href="#7.27"><time.h></a>
20615 struct tm *localtime(const time_t *timer);
20617 <p><b>Description</b>
20618 <p><a name="7.27.3.4p2" href="#7.27.3.4p2"><small>2</small></a>
20619 The localtime function converts the calendar time pointed to by timer into a
20620 broken-down time, expressed as local time.
20622 <p><a name="7.27.3.4p3" href="#7.27.3.4p3"><small>3</small></a>
20623 The localtime function returns a pointer to the broken-down time, or a null pointer if
20624 the specified time cannot be converted to local time.
20626 <p><small><a href="#Contents">Contents</a></small>
20627 <h5><a name="7.27.3.5" href="#7.27.3.5">7.27.3.5 The strftime function</a></h5>
20629 <p><a name="7.27.3.5p1" href="#7.27.3.5p1"><small>1</small></a>
20631 #include <a href="#7.27"><time.h></a>
20632 size_t strftime(char * restrict s,
20634 const char * restrict format,
20635 const struct tm * restrict timeptr);
20637 <p><b>Description</b>
20638 <p><a name="7.27.3.5p2" href="#7.27.3.5p2"><small>2</small></a>
20639 The strftime function places characters into the array pointed to by s as controlled by
20640 the string pointed to by format. The format shall be a multibyte character sequence,
20641 beginning and ending in its initial shift state. The format string consists of zero or
20642 more conversion specifiers and ordinary multibyte characters. A conversion specifier
20643 consists of a % character, possibly followed by an E or O modifier character (described
20644 below), followed by a character that determines the behavior of the conversion specifier.
20645 All ordinary multibyte characters (including the terminating null character) are copied
20646 unchanged into the array. If copying takes place between objects that overlap, the
20647 behavior is undefined. No more than maxsize characters are placed into the array.
20648 <p><a name="7.27.3.5p3" href="#7.27.3.5p3"><small>3</small></a>
20649 Each conversion specifier is replaced by appropriate characters as described in the
20650 following list. The appropriate characters are determined using the LC_TIME category
20652 of the current locale and by the values of zero or more members of the broken-down time
20653 structure pointed to by timeptr, as specified in brackets in the description. If any of
20654 the specified values is outside the normal range, the characters stored are unspecified.
20655 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
20656 %A is replaced by the locale's full weekday name. [tm_wday]
20657 %b is replaced by the locale's abbreviated month name. [tm_mon]
20658 %B is replaced by the locale's full month name. [tm_mon]
20659 %c is replaced by the locale's appropriate date and time representation. [all specified
20661 in <a href="#7.27.1">7.27.1</a>]
20663 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
20665 number (00-99). [tm_year]
20667 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
20668 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
20669 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
20671 preceded by a space. [tm_mday]
20673 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
20677 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
20679 number (00-99). [tm_year, tm_wday, tm_yday]
20681 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
20683 [tm_year, tm_wday, tm_yday]
20685 %h is equivalent to ''%b''. [tm_mon]
20686 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
20687 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
20688 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
20689 %m is replaced by the month as a decimal number (01-12). [tm_mon]
20690 %M is replaced by the minute as a decimal number (00-59). [tm_min]
20691 %n is replaced by a new-line character.
20692 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
20694 12-hour clock. [tm_hour]
20696 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
20697 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
20698 %S is replaced by the second as a decimal number (00-60). [tm_sec]
20699 %t is replaced by a horizontal-tab character.
20700 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
20704 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
20708 %U is replaced by the week number of the year (the first Sunday as the first day of week
20710 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
20712 %V is replaced by the ISO 8601 week number (see below) as a decimal number
20715 (01-53). [tm_year, tm_wday, tm_yday]
20717 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
20721 %W is replaced by the week number of the year (the first Monday as the first day of
20723 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
20725 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.27.1">7.27.1</a>]
20726 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.27.1">7.27.1</a>]
20727 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
20731 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
20732 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
20734 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
20735 zone is determinable. [tm_isdst]
20737 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
20739 time zone is determinable. [tm_isdst]
20741 %% is replaced by %.
20742 <p><a name="7.27.3.5p4" href="#7.27.3.5p4"><small>4</small></a>
20743 Some conversion specifiers can be modified by the inclusion of an E or O modifier
20744 character to indicate an alternative format or specification. If the alternative format or
20745 specification does not exist for the current locale, the modifier is ignored.
20746 %Ec is replaced by the locale's alternative date and time representation.
20747 %EC is replaced by the name of the base year (period) in the locale's alternative
20751 %Ex is replaced by the locale's alternative date representation.
20752 %EX is replaced by the locale's alternative time representation.
20753 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
20757 %EY is replaced by the locale's full alternative year representation.
20758 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
20760 (filled as needed with leading zeros, or with leading spaces if there is no alternative
20763 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
20765 (filled as needed with leading spaces).
20767 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
20771 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
20775 %Om is replaced by the month, using the locale's alternative numeric symbols.
20776 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
20777 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
20778 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
20781 representation, where Monday is 1.
20783 %OU is replaced by the week number, using the locale's alternative numeric symbols.
20784 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
20788 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
20792 %OW is replaced by the week number of the year, using the locale's alternative numeric
20796 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
20800 <p><a name="7.27.3.5p5" href="#7.27.3.5p5"><small>5</small></a>
20801 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
20802 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
20803 which is also the week that includes the first Thursday of the year, and is also the first
20804 week that contains at least four days in the year. If the first Monday of January is the
20805 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
20806 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
20807 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
20808 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
20809 %V is replaced by 01.
20810 <p><a name="7.27.3.5p6" href="#7.27.3.5p6"><small>6</small></a>
20811 If a conversion specifier is not one of the above, the behavior is undefined.
20812 <p><a name="7.27.3.5p7" href="#7.27.3.5p7"><small>7</small></a>
20813 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
20814 following specifiers are:
20815 %a the first three characters of %A.
20816 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
20817 %b the first three characters of %B.
20818 %B one of ''January'', ''February'', ... , ''December''.
20819 %c equivalent to ''%a %b %e %T %Y''.
20820 %p one of ''AM'' or ''PM''.
20821 %r equivalent to ''%I:%M:%S %p''.
20822 %x equivalent to ''%m/%d/%y''.
20823 %X equivalent to %T.
20824 %Z implementation-defined.
20826 <p><a name="7.27.3.5p8" href="#7.27.3.5p8"><small>8</small></a>
20827 If the total number of resulting characters including the terminating null character is not
20828 more than maxsize, the strftime function returns the number of characters placed
20829 into the array pointed to by s not including the terminating null character. Otherwise,
20830 zero is returned and the contents of the array are indeterminate.
20833 <p><small><a href="#Contents">Contents</a></small>
20834 <h3><a name="7.28" href="#7.28">7.28 Unicode utilities <uchar.h></a></h3>
20835 <p><a name="7.28p1" href="#7.28p1"><small>1</small></a>
20836 The header <a href="#7.28"><uchar.h></a> declares types and functions for manipulating Unicode
20838 <p><a name="7.28p2" href="#7.28p2"><small>2</small></a>
20839 The types declared are mbstate_t (described in <a href="#7.30.1">7.30.1</a>) and size_t (described in
20840 <a href="#7.19">7.19</a>);
20844 which is an unsigned integer type used for 16-bit characters and is the same type as
20845 uint_least16_t (described in <a href="#7.20.1.2">7.20.1.2</a>); and
20849 which is an unsigned integer type used for 32-bit characters and is the same type as
20850 uint_least32_t (also described in <a href="#7.20.1.2">7.20.1.2</a>).
20852 <p><small><a href="#Contents">Contents</a></small>
20853 <h4><a name="7.28.1" href="#7.28.1">7.28.1 Restartable multibyte/wide character conversion functions</a></h4>
20854 <p><a name="7.28.1p1" href="#7.28.1p1"><small>1</small></a>
20855 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
20856 object that can completely describe the current conversion state of the associated
20857 multibyte character sequence, which the functions alter as necessary. If ps is a null
20858 pointer, each function uses its own internal mbstate_t object instead, which is
20859 initialized at program startup to the initial conversion state; the functions are not required
20860 to avoid data races with other calls to the same function in this case. The implementation
20861 behaves as if no library function calls these functions with a null pointer for ps.
20863 <p><small><a href="#Contents">Contents</a></small>
20864 <h5><a name="7.28.1.1" href="#7.28.1.1">7.28.1.1 The mbrtoc16 function</a></h5>
20866 <p><a name="7.28.1.1p1" href="#7.28.1.1p1"><small>1</small></a>
20868 #include <a href="#7.28"><uchar.h></a>
20869 size_t mbrtoc16(char16_t * restrict pc16,
20870 const char * restrict s, size_t n,
20871 mbstate_t * restrict ps);
20873 <p><b>Description</b>
20874 <p><a name="7.28.1.1p2" href="#7.28.1.1p2"><small>2</small></a>
20875 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
20877 mbrtoc16(NULL, "", 1, ps)
20879 In this case, the values of the parameters pc16 and n are ignored.
20880 <p><a name="7.28.1.1p3" href="#7.28.1.1p3"><small>3</small></a>
20881 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
20882 the byte pointed to by s to determine the number of bytes needed to complete the next
20883 multibyte character (including any shift sequences). If the function determines that the
20884 next multibyte character is complete and valid, it determines the values of the
20885 corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
20886 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
20888 store successive wide characters without consuming any additional input until all the
20889 characters have been stored. If the corresponding wide character is the null wide
20890 character, the resulting state described is the initial conversion state.
20892 <p><a name="7.28.1.1p4" href="#7.28.1.1p4"><small>4</small></a>
20893 The mbrtoc16 function returns the first of the following that applies (given the current
20895 0 if the next n or fewer bytes complete the multibyte character that
20897 corresponds to the null wide character (which is the value stored).
20899 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20901 character (which is the value stored); the value returned is the number
20902 of bytes that complete the multibyte character.
20904 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20906 bytes from the input have been consumed by this call).
20908 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
20910 multibyte character, and all n bytes have been processed (no value is
20911 stored).<sup><a href="#note324"><b>324)</b></a></sup>
20913 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
20915 do not contribute to a complete and valid multibyte character (no
20916 value is stored); the value of the macro EILSEQ is stored in errno,
20917 and the conversion state is unspecified.
20920 <p><b>Footnotes</b>
20921 <p><small><a name="note324" href="#note324">324)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
20922 sequence of redundant shift sequences (for implementations with state-dependent encodings).
20925 <p><small><a href="#Contents">Contents</a></small>
20926 <h5><a name="7.28.1.2" href="#7.28.1.2">7.28.1.2 The c16rtomb function</a></h5>
20928 <p><a name="7.28.1.2p1" href="#7.28.1.2p1"><small>1</small></a>
20930 #include <a href="#7.28"><uchar.h></a>
20931 size_t c16rtomb(char * restrict s, char16_t c16,
20932 mbstate_t * restrict ps);
20934 <p><b>Description</b>
20935 <p><a name="7.28.1.2p2" href="#7.28.1.2p2"><small>2</small></a>
20936 If s is a null pointer, the c16rtomb function is equivalent to the call
20938 c16rtomb(buf, L'\0', ps)
20940 where buf is an internal buffer.
20941 <p><a name="7.28.1.2p3" href="#7.28.1.2p3"><small>3</small></a>
20942 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
20943 to represent the multibyte character that corresponds to the wide character given by c16
20944 (including any shift sequences), and stores the multibyte character representation in the
20947 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
20948 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
20949 to restore the initial shift state; the resulting state described is the initial conversion state.
20951 <p><a name="7.28.1.2p4" href="#7.28.1.2p4"><small>4</small></a>
20952 The c16rtomb function returns the number of bytes stored in the array object (including
20953 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
20954 the function stores the value of the macro EILSEQ in errno and returns
20955 (size_t)(-1); the conversion state is unspecified.
20957 <p><small><a href="#Contents">Contents</a></small>
20958 <h5><a name="7.28.1.3" href="#7.28.1.3">7.28.1.3 The mbrtoc32 function</a></h5>
20960 <p><a name="7.28.1.3p1" href="#7.28.1.3p1"><small>1</small></a>
20962 #include <a href="#7.28"><uchar.h></a>
20963 size_t mbrtoc32(char32_t * restrict pc32,
20964 const char * restrict s, size_t n,
20965 mbstate_t * restrict ps);
20967 <p><b>Description</b>
20968 <p><a name="7.28.1.3p2" href="#7.28.1.3p2"><small>2</small></a>
20969 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
20971 mbrtoc32(NULL, "", 1, ps)
20973 In this case, the values of the parameters pc32 and n are ignored.
20974 <p><a name="7.28.1.3p3" href="#7.28.1.3p3"><small>3</small></a>
20975 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
20976 the byte pointed to by s to determine the number of bytes needed to complete the next
20977 multibyte character (including any shift sequences). If the function determines that the
20978 next multibyte character is complete and valid, it determines the values of the
20979 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
20980 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
20981 store successive wide characters without consuming any additional input until all the
20982 characters have been stored. If the corresponding wide character is the null wide
20983 character, the resulting state described is the initial conversion state.
20985 <p><a name="7.28.1.3p4" href="#7.28.1.3p4"><small>4</small></a>
20986 The mbrtoc32 function returns the first of the following that applies (given the current
20988 0 if the next n or fewer bytes complete the multibyte character that
20990 corresponds to the null wide character (which is the value stored).
20992 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20995 character (which is the value stored); the value returned is the number
20996 of bytes that complete the multibyte character.
20998 (size_t)(-3) if the next character resulting from a previous call has been stored (no
21000 bytes from the input have been consumed by this call).
21002 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
21004 multibyte character, and all n bytes have been processed (no value is
21005 stored).<sup><a href="#note325"><b>325)</b></a></sup>
21007 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
21009 do not contribute to a complete and valid multibyte character (no
21010 value is stored); the value of the macro EILSEQ is stored in errno,
21011 and the conversion state is unspecified.
21014 <p><b>Footnotes</b>
21015 <p><small><a name="note325" href="#note325">325)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
21016 sequence of redundant shift sequences (for implementations with state-dependent encodings).
21019 <p><small><a href="#Contents">Contents</a></small>
21020 <h5><a name="7.28.1.4" href="#7.28.1.4">7.28.1.4 The c32rtomb function</a></h5>
21022 <p><a name="7.28.1.4p1" href="#7.28.1.4p1"><small>1</small></a>
21024 #include <a href="#7.28"><uchar.h></a>
21025 size_t c32rtomb(char * restrict s, char32_t c32,
21026 mbstate_t * restrict ps);
21028 <p><b>Description</b>
21029 <p><a name="7.28.1.4p2" href="#7.28.1.4p2"><small>2</small></a>
21030 If s is a null pointer, the c32rtomb function is equivalent to the call
21032 c32rtomb(buf, L'\0', ps)
21034 where buf is an internal buffer.
21035 <p><a name="7.28.1.4p3" href="#7.28.1.4p3"><small>3</small></a>
21036 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
21037 to represent the multibyte character that corresponds to the wide character given by c32
21038 (including any shift sequences), and stores the multibyte character representation in the
21039 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
21040 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
21041 to restore the initial shift state; the resulting state described is the initial conversion state.
21043 <p><a name="7.28.1.4p4" href="#7.28.1.4p4"><small>4</small></a>
21044 The c32rtomb function returns the number of bytes stored in the array object (including
21045 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
21046 the function stores the value of the macro EILSEQ in errno and returns
21047 (size_t)(-1); the conversion state is unspecified.
21054 <p><small><a href="#Contents">Contents</a></small>
21055 <h3><a name="7.29" href="#7.29">7.29 Extended multibyte and wide character utilities <wchar.h></a></h3>
21057 <p><small><a href="#Contents">Contents</a></small>
21058 <h4><a name="7.29.1" href="#7.29.1">7.29.1 Introduction</a></h4>
21059 <p><a name="7.29.1p1" href="#7.29.1p1"><small>1</small></a>
21060 The header <a href="#7.29"><wchar.h></a> defines four macros, and declares four data types, one tag, and
21061 many functions.<sup><a href="#note326"><b>326)</b></a></sup>
21062 <p><a name="7.29.1p2" href="#7.29.1p2"><small>2</small></a>
21063 The types declared are wchar_t and size_t (both described in <a href="#7.19">7.19</a>);
21067 which is a complete object type other than an array type that can hold the conversion state
21068 information necessary to convert between sequences of multibyte characters and wide
21073 which is an integer type unchanged by default argument promotions that can hold any
21074 value corresponding to members of the extended character set, as well as at least one
21075 value that does not correspond to any member of the extended character set (see WEOF
21076 below);<sup><a href="#note327"><b>327)</b></a></sup> and
21080 which is declared as an incomplete structure type (the contents are described in <a href="#7.27.1">7.27.1</a>).
21081 <p><a name="7.29.1p3" href="#7.29.1p3"><small>3</small></a>
21082 The macros defined are NULL (described in <a href="#7.19">7.19</a>); WCHAR_MIN and WCHAR_MAX
21083 (described in <a href="#7.20.3">7.20.3</a>); and
21087 which expands to a constant expression of type wint_t whose value does not
21088 correspond to any member of the extended character set.<sup><a href="#note328"><b>328)</b></a></sup> It is accepted (and returned)
21089 by several functions in this subclause to indicate end-of-file, that is, no more input from a
21090 stream. It is also used as a wide character value that does not correspond to any member
21091 of the extended character set.
21092 <p><a name="7.29.1p4" href="#7.29.1p4"><small>4</small></a>
21093 The functions declared are grouped as follows:
21095 <li> Functions that perform input and output of wide characters, or multibyte characters,
21097 <li> Functions that provide wide string numeric conversion;
21098 <li> Functions that perform general wide string manipulation;
21102 <li> Functions for wide string date and time conversion; and
21103 <li> Functions that provide extended capabilities for conversion between multibyte and
21104 wide character sequences.
21106 <p><a name="7.29.1p5" href="#7.29.1p5"><small>5</small></a>
21107 Arguments to the functions in this subclause may point to arrays containing wchar_t
21108 values that do not correspond to members of the extended character set. Such values
21109 shall be processed according to the specified semantics, except that it is unspecified
21110 whether an encoding error occurs if such a value appears in the format string for a
21111 function in <a href="#7.29.2">7.29.2</a> or <a href="#7.29.5">7.29.5</a> and the specified semantics do not require that value to be
21112 processed by wcrtomb.
21113 <p><a name="7.29.1p6" href="#7.29.1p6"><small>6</small></a>
21114 Unless explicitly stated otherwise, if the execution of a function described in this
21115 subclause causes copying to take place between objects that overlap, the behavior is
21118 <p><b>Footnotes</b>
21119 <p><small><a name="note326" href="#note326">326)</a> See ''future library directions'' (<a href="#7.31.16">7.31.16</a>).
21121 <p><small><a name="note327" href="#note327">327)</a> wchar_t and wint_t can be the same integer type.
21123 <p><small><a name="note328" href="#note328">328)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
21126 <p><small><a href="#Contents">Contents</a></small>
21127 <h4><a name="7.29.2" href="#7.29.2">7.29.2 Formatted wide character input/output functions</a></h4>
21128 <p><a name="7.29.2p1" href="#7.29.2p1"><small>1</small></a>
21129 The formatted wide character input/output functions shall behave as if there is a sequence
21130 point after the actions associated with each specifier.<sup><a href="#note329"><b>329)</b></a></sup>
21132 <p><b>Footnotes</b>
21133 <p><small><a name="note329" href="#note329">329)</a> The fwprintf functions perform writes to memory for the %n specifier.
21136 <p><small><a href="#Contents">Contents</a></small>
21137 <h5><a name="7.29.2.1" href="#7.29.2.1">7.29.2.1 The fwprintf function</a></h5>
21139 <p><a name="7.29.2.1p1" href="#7.29.2.1p1"><small>1</small></a>
21141 #include <a href="#7.21"><stdio.h></a>
21142 #include <a href="#7.29"><wchar.h></a>
21143 int fwprintf(FILE * restrict stream,
21144 const wchar_t * restrict format, ...);
21146 <p><b>Description</b>
21147 <p><a name="7.29.2.1p2" href="#7.29.2.1p2"><small>2</small></a>
21148 The fwprintf function writes output to the stream pointed to by stream, under
21149 control of the wide string pointed to by format that specifies how subsequent arguments
21150 are converted for output. If there are insufficient arguments for the format, the behavior
21151 is undefined. If the format is exhausted while arguments remain, the excess arguments
21152 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
21153 when the end of the format string is encountered.
21154 <p><a name="7.29.2.1p3" href="#7.29.2.1p3"><small>3</small></a>
21155 The format is composed of zero or more directives: ordinary wide characters (not %),
21156 which are copied unchanged to the output stream; and conversion specifications, each of
21157 which results in fetching zero or more subsequent arguments, converting them, if
21158 applicable, according to the corresponding conversion specifier, and then writing the
21159 result to the output stream.
21164 <p><a name="7.29.2.1p4" href="#7.29.2.1p4"><small>4</small></a>
21165 Each conversion specification is introduced by the wide character %. After the %, the
21166 following appear in sequence:
21168 <li> Zero or more flags (in any order) that modify the meaning of the conversion
21170 <li> An optional minimum field width. If the converted value has fewer wide characters
21171 than the field width, it is padded with spaces (by default) on the left (or right, if the
21172 left adjustment flag, described later, has been given) to the field width. The field
21173 width takes the form of an asterisk * (described later) or a nonnegative decimal
21174 integer.<sup><a href="#note330"><b>330)</b></a></sup>
21175 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
21176 o, u, x, and X conversions, the number of digits to appear after the decimal-point
21177 wide character for a, A, e, E, f, and F conversions, the maximum number of
21178 significant digits for the g and G conversions, or the maximum number of wide
21179 characters to be written for s conversions. The precision takes the form of a period
21180 (.) followed either by an asterisk * (described later) or by an optional decimal
21181 integer; if only the period is specified, the precision is taken as zero. If a precision
21182 appears with any other conversion specifier, the behavior is undefined.
21183 <li> An optional length modifier that specifies the size of the argument.
21184 <li> A conversion specifier wide character that specifies the type of conversion to be
21187 <p><a name="7.29.2.1p5" href="#7.29.2.1p5"><small>5</small></a>
21188 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
21189 this case, an int argument supplies the field width or precision. The arguments
21190 specifying field width, or precision, or both, shall appear (in that order) before the
21191 argument (if any) to be converted. A negative field width argument is taken as a - flag
21192 followed by a positive field width. A negative precision argument is taken as if the
21193 precision were omitted.
21194 <p><a name="7.29.2.1p6" href="#7.29.2.1p6"><small>6</small></a>
21195 The flag wide characters and their meanings are:
21196 - The result of the conversion is left-justified within the field. (It is right-justified if
21198 this flag is not specified.)
21200 + The result of a signed conversion always begins with a plus or minus sign. (It
21202 begins with a sign only when a negative value is converted if this flag is not
21210 specified.)<sup><a href="#note331"><b>331)</b></a></sup>
21212 space If the first wide character of a signed conversion is not a sign, or if a signed
21214 conversion results in no wide characters, a space is prefixed to the result. If the
21215 space and + flags both appear, the space flag is ignored.
21217 # The result is converted to an ''alternative form''. For o conversion, it increases
21219 the precision, if and only if necessary, to force the first digit of the result to be a
21220 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
21221 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
21222 and G conversions, the result of converting a floating-point number always
21223 contains a decimal-point wide character, even if no digits follow it. (Normally, a
21224 decimal-point wide character appears in the result of these conversions only if a
21225 digit follows it.) For g and G conversions, trailing zeros are not removed from the
21226 result. For other conversions, the behavior is undefined.
21228 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
21230 (following any indication of sign or base) are used to pad to the field width rather
21231 than performing space padding, except when converting an infinity or NaN. If the
21232 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
21233 conversions, if a precision is specified, the 0 flag is ignored. For other
21234 conversions, the behavior is undefined.
21236 <p><a name="7.29.2.1p7" href="#7.29.2.1p7"><small>7</small></a>
21237 The length modifiers and their meanings are:
21238 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21240 signed char or unsigned char argument (the argument will have
21241 been promoted according to the integer promotions, but its value shall be
21242 converted to signed char or unsigned char before printing); or that
21243 a following n conversion specifier applies to a pointer to a signed char
21246 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21248 short int or unsigned short int argument (the argument will
21249 have been promoted according to the integer promotions, but its value shall
21250 be converted to short int or unsigned short int before printing);
21251 or that a following n conversion specifier applies to a pointer to a short
21254 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21256 long int or unsigned long int argument; that a following n
21257 conversion specifier applies to a pointer to a long int argument; that a
21263 following c conversion specifier applies to a wint_t argument; that a
21264 following s conversion specifier applies to a pointer to a wchar_t
21265 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
21268 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21270 long long int or unsigned long long int argument; or that a
21271 following n conversion specifier applies to a pointer to a long long int
21274 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
21276 an intmax_t or uintmax_t argument; or that a following n conversion
21277 specifier applies to a pointer to an intmax_t argument.
21279 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21281 size_t or the corresponding signed integer type argument; or that a
21282 following n conversion specifier applies to a pointer to a signed integer type
21283 corresponding to size_t argument.
21285 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21287 ptrdiff_t or the corresponding unsigned integer type argument; or that a
21288 following n conversion specifier applies to a pointer to a ptrdiff_t
21291 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
21293 applies to a long double argument.
21295 If a length modifier appears with any conversion specifier other than as specified above,
21296 the behavior is undefined.
21297 <p><a name="7.29.2.1p8" href="#7.29.2.1p8"><small>8</small></a>
21298 The conversion specifiers and their meanings are:
21299 d,i The int argument is converted to signed decimal in the style [-]dddd. The
21301 precision specifies the minimum number of digits to appear; if the value
21302 being converted can be represented in fewer digits, it is expanded with
21303 leading zeros. The default precision is 1. The result of converting a zero
21304 value with a precision of zero is no wide characters.
21306 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
21309 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
21310 letters abcdef are used for x conversion and the letters ABCDEF for X
21311 conversion. The precision specifies the minimum number of digits to appear;
21312 if the value being converted can be represented in fewer digits, it is expanded
21313 with leading zeros. The default precision is 1. The result of converting a
21314 zero value with a precision of zero is no wide characters.
21316 f,F A double argument representing a floating-point number is converted to
21318 decimal notation in the style [-]ddd.ddd, where the number of digits after
21319 the decimal-point wide character is equal to the precision specification. If the
21320 precision is missing, it is taken as 6; if the precision is zero and the # flag is
21321 not specified, no decimal-point wide character appears. If a decimal-point
21322 wide character appears, at least one digit appears before it. The value is
21323 rounded to the appropriate number of digits.
21324 A double argument representing an infinity is converted in one of the styles
21325 [-]inf or [-]infinity -- which style is implementation-defined. A
21326 double argument representing a NaN is converted in one of the styles
21327 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
21328 any n-wchar-sequence, is implementation-defined. The F conversion
21329 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
21330 nan, respectively.<sup><a href="#note332"><b>332)</b></a></sup>
21332 e,E A double argument representing a floating-point number is converted in the
21334 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
21335 argument is nonzero) before the decimal-point wide character and the number
21336 of digits after it is equal to the precision; if the precision is missing, it is taken
21337 as 6; if the precision is zero and the # flag is not specified, no decimal-point
21338 wide character appears. The value is rounded to the appropriate number of
21339 digits. The E conversion specifier produces a number with E instead of e
21340 introducing the exponent. The exponent always contains at least two digits,
21341 and only as many more digits as necessary to represent the exponent. If the
21342 value is zero, the exponent is zero.
21343 A double argument representing an infinity or NaN is converted in the style
21344 of an f or F conversion specifier.
21346 g,G A double argument representing a floating-point number is converted in
21348 style f or e (or in style F or E in the case of a G conversion specifier),
21349 depending on the value converted and the precision. Let P equal the
21350 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
21351 Then, if a conversion with style E would have an exponent of X:
21352 -- if P > X >= -4, the conversion is with style f (or F) and precision
21354 -- otherwise, the conversion is with style e (or E) and precision P - 1.
21355 Finally, unless the # flag is used, any trailing zeros are removed from the
21361 fractional portion of the result and the decimal-point wide character is
21362 removed if there is no fractional portion remaining.
21363 A double argument representing an infinity or NaN is converted in the style
21364 of an f or F conversion specifier.
21366 a,A A double argument representing a floating-point number is converted in the
21368 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
21369 nonzero if the argument is a normalized floating-point number and is
21370 otherwise unspecified) before the decimal-point wide character<sup><a href="#note333"><b>333)</b></a></sup> and the
21371 number of hexadecimal digits after it is equal to the precision; if the precision
21372 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
21373 for an exact representation of the value; if the precision is missing and
21374 FLT_RADIX is not a power of 2, then the precision is sufficient to
21375 distinguish<sup><a href="#note334"><b>334)</b></a></sup> values of type double, except that trailing zeros may be
21376 omitted; if the precision is zero and the # flag is not specified, no decimal-
21377 point wide character appears. The letters abcdef are used for a conversion
21378 and the letters ABCDEF for A conversion. The A conversion specifier
21379 produces a number with X and P instead of x and p. The exponent always
21380 contains at least one digit, and only as many more digits as necessary to
21381 represent the decimal exponent of 2. If the value is zero, the exponent is
21383 A double argument representing an infinity or NaN is converted in the style
21384 of an f or F conversion specifier.
21386 c If no l length modifier is present, the int argument is converted to a wide
21388 character as if by calling btowc and the resulting wide character is written.
21389 If an l length modifier is present, the wint_t argument is converted to
21390 wchar_t and written.
21392 s If no l length modifier is present, the argument shall be a pointer to the initial
21394 element of a character array containing a multibyte character sequence
21395 beginning in the initial shift state. Characters from the array are converted as
21396 if by repeated calls to the mbrtowc function, with the conversion state
21397 described by an mbstate_t object initialized to zero before the first
21398 multibyte character is converted, and written up to (but not including) the
21403 terminating null wide character. If the precision is specified, no more than
21404 that many wide characters are written. If the precision is not specified or is
21405 greater than the size of the converted array, the converted array shall contain a
21406 null wide character.
21407 If an l length modifier is present, the argument shall be a pointer to the initial
21408 element of an array of wchar_t type. Wide characters from the array are
21409 written up to (but not including) a terminating null wide character. If the
21410 precision is specified, no more than that many wide characters are written. If
21411 the precision is not specified or is greater than the size of the array, the array
21412 shall contain a null wide character.
21414 p The argument shall be a pointer to void. The value of the pointer is
21416 converted to a sequence of printing wide characters, in an implementation-
21419 n The argument shall be a pointer to signed integer into which is written the
21421 number of wide characters written to the output stream so far by this call to
21422 fwprintf. No argument is converted, but one is consumed. If the
21423 conversion specification includes any flags, a field width, or a precision, the
21424 behavior is undefined.
21426 % A % wide character is written. No argument is converted. The complete
21428 conversion specification shall be %%.
21430 <p><a name="7.29.2.1p9" href="#7.29.2.1p9"><small>9</small></a>
21431 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note335"><b>335)</b></a></sup> If any argument is
21432 not the correct type for the corresponding conversion specification, the behavior is
21434 <p><a name="7.29.2.1p10" href="#7.29.2.1p10"><small>10</small></a>
21435 In no case does a nonexistent or small field width cause truncation of a field; if the result
21436 of a conversion is wider than the field width, the field is expanded to contain the
21438 <p><a name="7.29.2.1p11" href="#7.29.2.1p11"><small>11</small></a>
21439 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
21440 to a hexadecimal floating number with the given precision.
21441 <p><b>Recommended practice</b>
21442 <p><a name="7.29.2.1p12" href="#7.29.2.1p12"><small>12</small></a>
21443 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
21444 representable in the given precision, the result should be one of the two adjacent numbers
21445 in hexadecimal floating style with the given precision, with the extra stipulation that the
21446 error should have a correct sign for the current rounding direction.
21447 <p><a name="7.29.2.1p13" href="#7.29.2.1p13"><small>13</small></a>
21448 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
21449 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note336"><b>336)</b></a></sup> If the number of
21452 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
21453 representable with DECIMAL_DIG digits, then the result should be an exact
21454 representation with trailing zeros. Otherwise, the source value is bounded by two
21455 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
21456 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
21457 the error should have a correct sign for the current rounding direction.
21459 <p><a name="7.29.2.1p14" href="#7.29.2.1p14"><small>14</small></a>
21460 The fwprintf function returns the number of wide characters transmitted, or a negative
21461 value if an output or encoding error occurred.
21462 <p><b>Environmental limits</b>
21463 <p><a name="7.29.2.1p15" href="#7.29.2.1p15"><small>15</small></a>
21464 The number of wide characters that can be produced by any single conversion shall be at
21466 <p><a name="7.29.2.1p16" href="#7.29.2.1p16"><small>16</small></a>
21467 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
21470 #include <a href="#7.12"><math.h></a>
21471 #include <a href="#7.21"><stdio.h></a>
21472 #include <a href="#7.29"><wchar.h></a>
21474 wchar_t *weekday, *month; // pointers to wide strings
21475 int day, hour, min;
21476 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
21477 weekday, month, day, hour, min);
21478 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
21481 <p><b> Forward references</b>: the btowc function (<a href="#7.29.6.1.1">7.29.6.1.1</a>), the mbrtowc function
21482 (<a href="#7.29.6.3.2">7.29.6.3.2</a>).
21484 <p><b>Footnotes</b>
21485 <p><small><a name="note330" href="#note330">330)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
21487 <p><small><a name="note331" href="#note331">331)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
21488 include a minus sign.
21490 <p><small><a name="note332" href="#note332">332)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
21491 meaning; the # and 0 flag wide characters have no effect.
21493 <p><small><a name="note333" href="#note333">333)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
21494 character so that subsequent digits align to nibble (4-bit) boundaries.
21496 <p><small><a name="note334" href="#note334">334)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
21497 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
21498 might suffice depending on the implementation's scheme for determining the digit to the left of the
21499 decimal-point wide character.
21501 <p><small><a name="note335" href="#note335">335)</a> See ''future library directions'' (<a href="#7.31.16">7.31.16</a>).
21503 <p><small><a name="note336" href="#note336">336)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
21504 given format specifier. The number of significant digits is determined by the format specifier, and in
21505 the case of fixed-point conversion by the source value as well.
21508 <p><small><a href="#Contents">Contents</a></small>
21509 <h5><a name="7.29.2.2" href="#7.29.2.2">7.29.2.2 The fwscanf function</a></h5>
21511 <p><a name="7.29.2.2p1" href="#7.29.2.2p1"><small>1</small></a>
21513 #include <a href="#7.21"><stdio.h></a>
21514 #include <a href="#7.29"><wchar.h></a>
21515 int fwscanf(FILE * restrict stream,
21516 const wchar_t * restrict format, ...);
21518 <p><b>Description</b>
21519 <p><a name="7.29.2.2p2" href="#7.29.2.2p2"><small>2</small></a>
21520 The fwscanf function reads input from the stream pointed to by stream, under
21521 control of the wide string pointed to by format that specifies the admissible input
21522 sequences and how they are to be converted for assignment, using subsequent arguments
21525 as pointers to the objects to receive the converted input. If there are insufficient
21526 arguments for the format, the behavior is undefined. If the format is exhausted while
21527 arguments remain, the excess arguments are evaluated (as always) but are otherwise
21529 <p><a name="7.29.2.2p3" href="#7.29.2.2p3"><small>3</small></a>
21530 The format is composed of zero or more directives: one or more white-space wide
21531 characters, an ordinary wide character (neither % nor a white-space wide character), or a
21532 conversion specification. Each conversion specification is introduced by the wide
21533 character %. After the %, the following appear in sequence:
21535 <li> An optional assignment-suppressing wide character *.
21536 <li> An optional decimal integer greater than zero that specifies the maximum field width
21537 (in wide characters).
21538 <li> An optional length modifier that specifies the size of the receiving object.
21539 <li> A conversion specifier wide character that specifies the type of conversion to be
21542 <p><a name="7.29.2.2p4" href="#7.29.2.2p4"><small>4</small></a>
21543 The fwscanf function executes each directive of the format in turn. When all directives
21544 have been executed, or if a directive fails (as detailed below), the function returns.
21545 Failures are described as input failures (due to the occurrence of an encoding error or the
21546 unavailability of input characters), or matching failures (due to inappropriate input).
21547 <p><a name="7.29.2.2p5" href="#7.29.2.2p5"><small>5</small></a>
21548 A directive composed of white-space wide character(s) is executed by reading input up to
21549 the first non-white-space wide character (which remains unread), or until no more wide
21550 characters can be read. The directive never fails.
21551 <p><a name="7.29.2.2p6" href="#7.29.2.2p6"><small>6</small></a>
21552 A directive that is an ordinary wide character is executed by reading the next wide
21553 character of the stream. If that wide character differs from the directive, the directive
21554 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
21555 of-file, an encoding error, or a read error prevents a wide character from being read, the
21557 <p><a name="7.29.2.2p7" href="#7.29.2.2p7"><small>7</small></a>
21558 A directive that is a conversion specification defines a set of matching input sequences, as
21559 described below for each specifier. A conversion specification is executed in the
21561 <p><a name="7.29.2.2p8" href="#7.29.2.2p8"><small>8</small></a>
21562 Input white-space wide characters (as specified by the iswspace function) are skipped,
21563 unless the specification includes a [, c, or n specifier.<sup><a href="#note337"><b>337)</b></a></sup>
21564 <p><a name="7.29.2.2p9" href="#7.29.2.2p9"><small>9</small></a>
21565 An input item is read from the stream, unless the specification includes an n specifier. An
21566 input item is defined as the longest sequence of input wide characters which does not
21567 exceed any specified field width and which is, or is a prefix of, a matching input
21571 sequence.<sup><a href="#note338"><b>338)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
21572 length of the input item is zero, the execution of the directive fails; this condition is a
21573 matching failure unless end-of-file, an encoding error, or a read error prevented input
21574 from the stream, in which case it is an input failure.
21575 <p><a name="7.29.2.2p10" href="#7.29.2.2p10"><small>10</small></a>
21576 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
21577 count of input wide characters) is converted to a type appropriate to the conversion
21578 specifier. If the input item is not a matching sequence, the execution of the directive fails:
21579 this condition is a matching failure. Unless assignment suppression was indicated by a *,
21580 the result of the conversion is placed in the object pointed to by the first argument
21581 following the format argument that has not already received a conversion result. If this
21582 object does not have an appropriate type, or if the result of the conversion cannot be
21583 represented in the object, the behavior is undefined.
21584 <p><a name="7.29.2.2p11" href="#7.29.2.2p11"><small>11</small></a>
21585 The length modifiers and their meanings are:
21586 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21588 to an argument with type pointer to signed char or unsigned char.
21590 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21592 to an argument with type pointer to short int or unsigned short
21595 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21597 to an argument with type pointer to long int or unsigned long
21598 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
21599 an argument with type pointer to double; or that a following c, s, or [
21600 conversion specifier applies to an argument with type pointer to wchar_t.
21602 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21604 to an argument with type pointer to long long int or unsigned
21607 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21609 to an argument with type pointer to intmax_t or uintmax_t.
21611 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21613 to an argument with type pointer to size_t or the corresponding signed
21616 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21618 to an argument with type pointer to ptrdiff_t or the corresponding
21619 unsigned integer type.
21624 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
21626 applies to an argument with type pointer to long double.
21628 If a length modifier appears with any conversion specifier other than as specified above,
21629 the behavior is undefined.
21630 <p><a name="7.29.2.2p12" href="#7.29.2.2p12"><small>12</small></a>
21631 The conversion specifiers and their meanings are:
21632 d Matches an optionally signed decimal integer, whose format is the same as
21634 expected for the subject sequence of the wcstol function with the value 10
21635 for the base argument. The corresponding argument shall be a pointer to
21638 i Matches an optionally signed integer, whose format is the same as expected
21640 for the subject sequence of the wcstol function with the value 0 for the
21641 base argument. The corresponding argument shall be a pointer to signed
21644 o Matches an optionally signed octal integer, whose format is the same as
21646 expected for the subject sequence of the wcstoul function with the value 8
21647 for the base argument. The corresponding argument shall be a pointer to
21650 u Matches an optionally signed decimal integer, whose format is the same as
21652 expected for the subject sequence of the wcstoul function with the value 10
21653 for the base argument. The corresponding argument shall be a pointer to
21656 x Matches an optionally signed hexadecimal integer, whose format is the same
21658 as expected for the subject sequence of the wcstoul function with the value
21659 16 for the base argument. The corresponding argument shall be a pointer to
21662 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
21664 format is the same as expected for the subject sequence of the wcstod
21665 function. The corresponding argument shall be a pointer to floating.
21667 c Matches a sequence of wide characters of exactly the number specified by the
21670 field width (1 if no field width is present in the directive).
21671 If no l length modifier is present, characters from the input field are
21672 converted as if by repeated calls to the wcrtomb function, with the
21673 conversion state described by an mbstate_t object initialized to zero
21674 before the first wide character is converted. The corresponding argument
21675 shall be a pointer to the initial element of a character array large enough to
21676 accept the sequence. No null character is added.
21677 If an l length modifier is present, the corresponding argument shall be a
21678 pointer to the initial element of an array of wchar_t large enough to accept
21679 the sequence. No null wide character is added.
21681 s Matches a sequence of non-white-space wide characters.
21683 If no l length modifier is present, characters from the input field are
21684 converted as if by repeated calls to the wcrtomb function, with the
21685 conversion state described by an mbstate_t object initialized to zero
21686 before the first wide character is converted. The corresponding argument
21687 shall be a pointer to the initial element of a character array large enough to
21688 accept the sequence and a terminating null character, which will be added
21690 If an l length modifier is present, the corresponding argument shall be a
21691 pointer to the initial element of an array of wchar_t large enough to accept
21692 the sequence and the terminating null wide character, which will be added
21695 [ Matches a nonempty sequence of wide characters from a set of expected
21698 characters (the scanset).
21699 If no l length modifier is present, characters from the input field are
21700 converted as if by repeated calls to the wcrtomb function, with the
21701 conversion state described by an mbstate_t object initialized to zero
21702 before the first wide character is converted. The corresponding argument
21703 shall be a pointer to the initial element of a character array large enough to
21704 accept the sequence and a terminating null character, which will be added
21706 If an l length modifier is present, the corresponding argument shall be a
21707 pointer to the initial element of an array of wchar_t large enough to accept
21708 the sequence and the terminating null wide character, which will be added
21710 The conversion specifier includes all subsequent wide characters in the
21711 format string, up to and including the matching right bracket (]). The wide
21712 characters between the brackets (the scanlist) compose the scanset, unless the
21713 wide character after the left bracket is a circumflex (^), in which case the
21714 scanset contains all wide characters that do not appear in the scanlist between
21715 the circumflex and the right bracket. If the conversion specifier begins with
21716 [] or [^], the right bracket wide character is in the scanlist and the next
21717 following right bracket wide character is the matching right bracket that ends
21718 the specification; otherwise the first following right bracket wide character is
21719 the one that ends the specification. If a - wide character is in the scanlist and
21720 is not the first, nor the second where the first wide character is a ^, nor the
21721 last character, the behavior is implementation-defined.
21723 p Matches an implementation-defined set of sequences, which should be the
21725 same as the set of sequences that may be produced by the %p conversion of
21726 the fwprintf function. The corresponding argument shall be a pointer to a
21727 pointer to void. The input item is converted to a pointer value in an
21728 implementation-defined manner. If the input item is a value converted earlier
21729 during the same program execution, the pointer that results shall compare
21730 equal to that value; otherwise the behavior of the %p conversion is undefined.
21732 n No input is consumed. The corresponding argument shall be a pointer to
21734 signed integer into which is to be written the number of wide characters read
21735 from the input stream so far by this call to the fwscanf function. Execution
21736 of a %n directive does not increment the assignment count returned at the
21737 completion of execution of the fwscanf function. No argument is
21738 converted, but one is consumed. If the conversion specification includes an
21739 assignment-suppressing wide character or a field width, the behavior is
21742 % Matches a single % wide character; no conversion or assignment occurs. The
21744 complete conversion specification shall be %%.
21746 <p><a name="7.29.2.2p13" href="#7.29.2.2p13"><small>13</small></a>
21747 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note339"><b>339)</b></a></sup>
21748 <p><a name="7.29.2.2p14" href="#7.29.2.2p14"><small>14</small></a>
21749 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
21750 respectively, a, e, f, g, and x.
21751 <p><a name="7.29.2.2p15" href="#7.29.2.2p15"><small>15</small></a>
21752 Trailing white space (including new-line wide characters) is left unread unless matched
21753 by a directive. The success of literal matches and suppressed assignments is not directly
21754 determinable other than via the %n directive.
21756 <p><a name="7.29.2.2p16" href="#7.29.2.2p16"><small>16</small></a>
21757 The fwscanf function returns the value of the macro EOF if an input failure occurs
21758 before the first conversion (if any) has completed. Otherwise, the function returns the
21759 number of input items assigned, which can be fewer than provided for, or even zero, in
21760 the event of an early matching failure.
21761 <p><a name="7.29.2.2p17" href="#7.29.2.2p17"><small>17</small></a>
21762 EXAMPLE 1 The call:
21764 #include <a href="#7.21"><stdio.h></a>
21765 #include <a href="#7.29"><wchar.h></a>
21767 int n, i; float x; wchar_t name[50];
21768 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
21774 with the input line:
21776 25 54.32E-1 thompson
21778 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
21781 <p><a name="7.29.2.2p18" href="#7.29.2.2p18"><small>18</small></a>
21782 EXAMPLE 2 The call:
21784 #include <a href="#7.21"><stdio.h></a>
21785 #include <a href="#7.29"><wchar.h></a>
21787 int i; float x; double y;
21788 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
21794 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
21795 56.0. The next wide character read from the input stream will be a.
21797 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.29.4.1.1">7.29.4.1.1</a>), the
21798 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.29.4.1.2">7.29.4.1.2</a>), the wcrtomb
21799 function (<a href="#7.29.6.3.3">7.29.6.3.3</a>).
21801 <p><b>Footnotes</b>
21802 <p><small><a name="note337" href="#note337">337)</a> These white-space wide characters are not counted against a specified field width.
21804 <p><small><a name="note338" href="#note338">338)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
21805 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
21807 <p><small><a name="note339" href="#note339">339)</a> See ''future library directions'' (<a href="#7.31.16">7.31.16</a>).
21810 <p><small><a href="#Contents">Contents</a></small>
21811 <h5><a name="7.29.2.3" href="#7.29.2.3">7.29.2.3 The swprintf function</a></h5>
21813 <p><a name="7.29.2.3p1" href="#7.29.2.3p1"><small>1</small></a>
21815 #include <a href="#7.29"><wchar.h></a>
21816 int swprintf(wchar_t * restrict s,
21818 const wchar_t * restrict format, ...);
21820 <p><b>Description</b>
21821 <p><a name="7.29.2.3p2" href="#7.29.2.3p2"><small>2</small></a>
21822 The swprintf function is equivalent to fwprintf, except that the argument s
21823 specifies an array of wide characters into which the generated output is to be written,
21824 rather than written to a stream. No more than n wide characters are written, including a
21825 terminating null wide character, which is always added (unless n is zero).
21827 <p><a name="7.29.2.3p3" href="#7.29.2.3p3"><small>3</small></a>
21828 The swprintf function returns the number of wide characters written in the array, not
21829 counting the terminating null wide character, or a negative value if an encoding error
21830 occurred or if n or more wide characters were requested to be written.
21833 <p><small><a href="#Contents">Contents</a></small>
21834 <h5><a name="7.29.2.4" href="#7.29.2.4">7.29.2.4 The swscanf function</a></h5>
21836 <p><a name="7.29.2.4p1" href="#7.29.2.4p1"><small>1</small></a>
21838 #include <a href="#7.29"><wchar.h></a>
21839 int swscanf(const wchar_t * restrict s,
21840 const wchar_t * restrict format, ...);
21842 <p><b>Description</b>
21843 <p><a name="7.29.2.4p2" href="#7.29.2.4p2"><small>2</small></a>
21844 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
21845 wide string from which the input is to be obtained, rather than from a stream. Reaching
21846 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
21849 <p><a name="7.29.2.4p3" href="#7.29.2.4p3"><small>3</small></a>
21850 The swscanf function returns the value of the macro EOF if an input failure occurs
21851 before the first conversion (if any) has completed. Otherwise, the swscanf function
21852 returns the number of input items assigned, which can be fewer than provided for, or even
21853 zero, in the event of an early matching failure.
21855 <p><small><a href="#Contents">Contents</a></small>
21856 <h5><a name="7.29.2.5" href="#7.29.2.5">7.29.2.5 The vfwprintf function</a></h5>
21858 <p><a name="7.29.2.5p1" href="#7.29.2.5p1"><small>1</small></a>
21860 #include <a href="#7.16"><stdarg.h></a>
21861 #include <a href="#7.21"><stdio.h></a>
21862 #include <a href="#7.29"><wchar.h></a>
21863 int vfwprintf(FILE * restrict stream,
21864 const wchar_t * restrict format,
21867 <p><b>Description</b>
21868 <p><a name="7.29.2.5p2" href="#7.29.2.5p2"><small>2</small></a>
21869 The vfwprintf function is equivalent to fwprintf, with the variable argument list
21870 replaced by arg, which shall have been initialized by the va_start macro (and
21871 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
21872 va_end macro.<sup><a href="#note340"><b>340)</b></a></sup>
21874 <p><a name="7.29.2.5p3" href="#7.29.2.5p3"><small>3</small></a>
21875 The vfwprintf function returns the number of wide characters transmitted, or a
21876 negative value if an output or encoding error occurred.
21882 <p><a name="7.29.2.5p4" href="#7.29.2.5p4"><small>4</small></a>
21883 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
21886 #include <a href="#7.16"><stdarg.h></a>
21887 #include <a href="#7.21"><stdio.h></a>
21888 #include <a href="#7.29"><wchar.h></a>
21889 void error(char *function_name, wchar_t *format, ...)
21892 va_start(args, format);
21893 // print out name of function causing error
21894 fwprintf(stderr, L"ERROR in %s: ", function_name);
21895 // print out remainder of message
21896 vfwprintf(stderr, format, args);
21902 <p><b>Footnotes</b>
21903 <p><small><a name="note340" href="#note340">340)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
21904 invoke the va_arg macro, the value of arg after the return is indeterminate.
21907 <p><small><a href="#Contents">Contents</a></small>
21908 <h5><a name="7.29.2.6" href="#7.29.2.6">7.29.2.6 The vfwscanf function</a></h5>
21910 <p><a name="7.29.2.6p1" href="#7.29.2.6p1"><small>1</small></a>
21912 #include <a href="#7.16"><stdarg.h></a>
21913 #include <a href="#7.21"><stdio.h></a>
21914 #include <a href="#7.29"><wchar.h></a>
21915 int vfwscanf(FILE * restrict stream,
21916 const wchar_t * restrict format,
21919 <p><b>Description</b>
21920 <p><a name="7.29.2.6p2" href="#7.29.2.6p2"><small>2</small></a>
21921 The vfwscanf function is equivalent to fwscanf, with the variable argument list
21922 replaced by arg, which shall have been initialized by the va_start macro (and
21923 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
21924 va_end macro.<sup><a href="#note340"><b>340)</b></a></sup>
21926 <p><a name="7.29.2.6p3" href="#7.29.2.6p3"><small>3</small></a>
21927 The vfwscanf function returns the value of the macro EOF if an input failure occurs
21928 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
21929 returns the number of input items assigned, which can be fewer than provided for, or even
21930 zero, in the event of an early matching failure.
21933 <p><small><a href="#Contents">Contents</a></small>
21934 <h5><a name="7.29.2.7" href="#7.29.2.7">7.29.2.7 The vswprintf function</a></h5>
21936 <p><a name="7.29.2.7p1" href="#7.29.2.7p1"><small>1</small></a>
21938 #include <a href="#7.16"><stdarg.h></a>
21939 #include <a href="#7.29"><wchar.h></a>
21940 int vswprintf(wchar_t * restrict s,
21942 const wchar_t * restrict format,
21945 <p><b>Description</b>
21946 <p><a name="7.29.2.7p2" href="#7.29.2.7p2"><small>2</small></a>
21947 The vswprintf function is equivalent to swprintf, with the variable argument list
21948 replaced by arg, which shall have been initialized by the va_start macro (and
21949 possibly subsequent va_arg calls). The vswprintf function does not invoke the
21950 va_end macro.<sup><a href="#note340"><b>340)</b></a></sup>
21952 <p><a name="7.29.2.7p3" href="#7.29.2.7p3"><small>3</small></a>
21953 The vswprintf function returns the number of wide characters written in the array, not
21954 counting the terminating null wide character, or a negative value if an encoding error
21955 occurred or if n or more wide characters were requested to be generated.
21957 <p><small><a href="#Contents">Contents</a></small>
21958 <h5><a name="7.29.2.8" href="#7.29.2.8">7.29.2.8 The vswscanf function</a></h5>
21960 <p><a name="7.29.2.8p1" href="#7.29.2.8p1"><small>1</small></a>
21962 #include <a href="#7.16"><stdarg.h></a>
21963 #include <a href="#7.29"><wchar.h></a>
21964 int vswscanf(const wchar_t * restrict s,
21965 const wchar_t * restrict format,
21968 <p><b>Description</b>
21969 <p><a name="7.29.2.8p2" href="#7.29.2.8p2"><small>2</small></a>
21970 The vswscanf function is equivalent to swscanf, with the variable argument list
21971 replaced by arg, which shall have been initialized by the va_start macro (and
21972 possibly subsequent va_arg calls). The vswscanf function does not invoke the
21973 va_end macro.<sup><a href="#note340"><b>340)</b></a></sup>
21975 <p><a name="7.29.2.8p3" href="#7.29.2.8p3"><small>3</small></a>
21976 The vswscanf function returns the value of the macro EOF if an input failure occurs
21977 before the first conversion (if any) has completed. Otherwise, the vswscanf function
21978 returns the number of input items assigned, which can be fewer than provided for, or even
21979 zero, in the event of an early matching failure.
21982 <p><small><a href="#Contents">Contents</a></small>
21983 <h5><a name="7.29.2.9" href="#7.29.2.9">7.29.2.9 The vwprintf function</a></h5>
21985 <p><a name="7.29.2.9p1" href="#7.29.2.9p1"><small>1</small></a>
21987 #include <a href="#7.16"><stdarg.h></a>
21988 #include <a href="#7.29"><wchar.h></a>
21989 int vwprintf(const wchar_t * restrict format,
21992 <p><b>Description</b>
21993 <p><a name="7.29.2.9p2" href="#7.29.2.9p2"><small>2</small></a>
21994 The vwprintf function is equivalent to wprintf, with the variable argument list
21995 replaced by arg, which shall have been initialized by the va_start macro (and
21996 possibly subsequent va_arg calls). The vwprintf function does not invoke the
21997 va_end macro.<sup><a href="#note340"><b>340)</b></a></sup>
21999 <p><a name="7.29.2.9p3" href="#7.29.2.9p3"><small>3</small></a>
22000 The vwprintf function returns the number of wide characters transmitted, or a negative
22001 value if an output or encoding error occurred.
22003 <p><small><a href="#Contents">Contents</a></small>
22004 <h5><a name="7.29.2.10" href="#7.29.2.10">7.29.2.10 The vwscanf function</a></h5>
22006 <p><a name="7.29.2.10p1" href="#7.29.2.10p1"><small>1</small></a>
22008 #include <a href="#7.16"><stdarg.h></a>
22009 #include <a href="#7.29"><wchar.h></a>
22010 int vwscanf(const wchar_t * restrict format,
22013 <p><b>Description</b>
22014 <p><a name="7.29.2.10p2" href="#7.29.2.10p2"><small>2</small></a>
22015 The vwscanf function is equivalent to wscanf, with the variable argument list
22016 replaced by arg, which shall have been initialized by the va_start macro (and
22017 possibly subsequent va_arg calls). The vwscanf function does not invoke the
22018 va_end macro.<sup><a href="#note340"><b>340)</b></a></sup>
22020 <p><a name="7.29.2.10p3" href="#7.29.2.10p3"><small>3</small></a>
22021 The vwscanf function returns the value of the macro EOF if an input failure occurs
22022 before the first conversion (if any) has completed. Otherwise, the vwscanf function
22023 returns the number of input items assigned, which can be fewer than provided for, or even
22024 zero, in the event of an early matching failure.
22027 <p><small><a href="#Contents">Contents</a></small>
22028 <h5><a name="7.29.2.11" href="#7.29.2.11">7.29.2.11 The wprintf function</a></h5>
22030 <p><a name="7.29.2.11p1" href="#7.29.2.11p1"><small>1</small></a>
22032 #include <a href="#7.29"><wchar.h></a>
22033 int wprintf(const wchar_t * restrict format, ...);
22035 <p><b>Description</b>
22036 <p><a name="7.29.2.11p2" href="#7.29.2.11p2"><small>2</small></a>
22037 The wprintf function is equivalent to fwprintf with the argument stdout
22038 interposed before the arguments to wprintf.
22040 <p><a name="7.29.2.11p3" href="#7.29.2.11p3"><small>3</small></a>
22041 The wprintf function returns the number of wide characters transmitted, or a negative
22042 value if an output or encoding error occurred.
22044 <p><small><a href="#Contents">Contents</a></small>
22045 <h5><a name="7.29.2.12" href="#7.29.2.12">7.29.2.12 The wscanf function</a></h5>
22047 <p><a name="7.29.2.12p1" href="#7.29.2.12p1"><small>1</small></a>
22049 #include <a href="#7.29"><wchar.h></a>
22050 int wscanf(const wchar_t * restrict format, ...);
22052 <p><b>Description</b>
22053 <p><a name="7.29.2.12p2" href="#7.29.2.12p2"><small>2</small></a>
22054 The wscanf function is equivalent to fwscanf with the argument stdin interposed
22055 before the arguments to wscanf.
22057 <p><a name="7.29.2.12p3" href="#7.29.2.12p3"><small>3</small></a>
22058 The wscanf function returns the value of the macro EOF if an input failure occurs
22059 before the first conversion (if any) has completed. Otherwise, the wscanf function
22060 returns the number of input items assigned, which can be fewer than provided for, or even
22061 zero, in the event of an early matching failure.
22063 <p><small><a href="#Contents">Contents</a></small>
22064 <h4><a name="7.29.3" href="#7.29.3">7.29.3 Wide character input/output functions</a></h4>
22066 <p><small><a href="#Contents">Contents</a></small>
22067 <h5><a name="7.29.3.1" href="#7.29.3.1">7.29.3.1 The fgetwc function</a></h5>
22069 <p><a name="7.29.3.1p1" href="#7.29.3.1p1"><small>1</small></a>
22071 #include <a href="#7.21"><stdio.h></a>
22072 #include <a href="#7.29"><wchar.h></a>
22073 wint_t fgetwc(FILE *stream);
22075 <p><b>Description</b>
22076 <p><a name="7.29.3.1p2" href="#7.29.3.1p2"><small>2</small></a>
22077 If the end-of-file indicator for the input stream pointed to by stream is not set and a
22078 next wide character is present, the fgetwc function obtains that wide character as a
22079 wchar_t converted to a wint_t and advances the associated file position indicator for
22080 the stream (if defined).
22083 <p><a name="7.29.3.1p3" href="#7.29.3.1p3"><small>3</small></a>
22084 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
22085 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
22086 the fgetwc function returns the next wide character from the input stream pointed to by
22087 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
22088 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
22089 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note341"><b>341)</b></a></sup>
22091 <p><b>Footnotes</b>
22092 <p><small><a name="note341" href="#note341">341)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
22093 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
22096 <p><small><a href="#Contents">Contents</a></small>
22097 <h5><a name="7.29.3.2" href="#7.29.3.2">7.29.3.2 The fgetws function</a></h5>
22099 <p><a name="7.29.3.2p1" href="#7.29.3.2p1"><small>1</small></a>
22101 #include <a href="#7.21"><stdio.h></a>
22102 #include <a href="#7.29"><wchar.h></a>
22103 wchar_t *fgetws(wchar_t * restrict s,
22104 int n, FILE * restrict stream);
22106 <p><b>Description</b>
22107 <p><a name="7.29.3.2p2" href="#7.29.3.2p2"><small>2</small></a>
22108 The fgetws function reads at most one less than the number of wide characters
22109 specified by n from the stream pointed to by stream into the array pointed to by s. No
22110 additional wide characters are read after a new-line wide character (which is retained) or
22111 after end-of-file. A null wide character is written immediately after the last wide
22112 character read into the array.
22114 <p><a name="7.29.3.2p3" href="#7.29.3.2p3"><small>3</small></a>
22115 The fgetws function returns s if successful. If end-of-file is encountered and no
22116 characters have been read into the array, the contents of the array remain unchanged and a
22117 null pointer is returned. If a read or encoding error occurs during the operation, the array
22118 contents are indeterminate and a null pointer is returned.
22120 <p><small><a href="#Contents">Contents</a></small>
22121 <h5><a name="7.29.3.3" href="#7.29.3.3">7.29.3.3 The fputwc function</a></h5>
22123 <p><a name="7.29.3.3p1" href="#7.29.3.3p1"><small>1</small></a>
22125 #include <a href="#7.21"><stdio.h></a>
22126 #include <a href="#7.29"><wchar.h></a>
22127 wint_t fputwc(wchar_t c, FILE *stream);
22129 <p><b>Description</b>
22130 <p><a name="7.29.3.3p2" href="#7.29.3.3p2"><small>2</small></a>
22131 The fputwc function writes the wide character specified by c to the output stream
22132 pointed to by stream, at the position indicated by the associated file position indicator
22133 for the stream (if defined), and advances the indicator appropriately. If the file cannot
22136 support positioning requests, or if the stream was opened with append mode, the
22137 character is appended to the output stream.
22139 <p><a name="7.29.3.3p3" href="#7.29.3.3p3"><small>3</small></a>
22140 The fputwc function returns the wide character written. If a write error occurs, the
22141 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
22142 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
22144 <p><small><a href="#Contents">Contents</a></small>
22145 <h5><a name="7.29.3.4" href="#7.29.3.4">7.29.3.4 The fputws function</a></h5>
22147 <p><a name="7.29.3.4p1" href="#7.29.3.4p1"><small>1</small></a>
22149 #include <a href="#7.21"><stdio.h></a>
22150 #include <a href="#7.29"><wchar.h></a>
22151 int fputws(const wchar_t * restrict s,
22152 FILE * restrict stream);
22154 <p><b>Description</b>
22155 <p><a name="7.29.3.4p2" href="#7.29.3.4p2"><small>2</small></a>
22156 The fputws function writes the wide string pointed to by s to the stream pointed to by
22157 stream. The terminating null wide character is not written.
22159 <p><a name="7.29.3.4p3" href="#7.29.3.4p3"><small>3</small></a>
22160 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
22161 returns a nonnegative value.
22163 <p><small><a href="#Contents">Contents</a></small>
22164 <h5><a name="7.29.3.5" href="#7.29.3.5">7.29.3.5 The fwide function</a></h5>
22166 <p><a name="7.29.3.5p1" href="#7.29.3.5p1"><small>1</small></a>
22168 #include <a href="#7.21"><stdio.h></a>
22169 #include <a href="#7.29"><wchar.h></a>
22170 int fwide(FILE *stream, int mode);
22172 <p><b>Description</b>
22173 <p><a name="7.29.3.5p2" href="#7.29.3.5p2"><small>2</small></a>
22174 The fwide function determines the orientation of the stream pointed to by stream. If
22175 mode is greater than zero, the function first attempts to make the stream wide oriented. If
22176 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note342"><b>342)</b></a></sup>
22177 Otherwise, mode is zero and the function does not alter the orientation of the stream.
22179 <p><a name="7.29.3.5p3" href="#7.29.3.5p3"><small>3</small></a>
22180 The fwide function returns a value greater than zero if, after the call, the stream has
22181 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
22182 stream has no orientation.
22187 <p><b>Footnotes</b>
22188 <p><small><a name="note342" href="#note342">342)</a> If the orientation of the stream has already been determined, fwide does not change it.
22191 <p><small><a href="#Contents">Contents</a></small>
22192 <h5><a name="7.29.3.6" href="#7.29.3.6">7.29.3.6 The getwc function</a></h5>
22194 <p><a name="7.29.3.6p1" href="#7.29.3.6p1"><small>1</small></a>
22196 #include <a href="#7.21"><stdio.h></a>
22197 #include <a href="#7.29"><wchar.h></a>
22198 wint_t getwc(FILE *stream);
22200 <p><b>Description</b>
22201 <p><a name="7.29.3.6p2" href="#7.29.3.6p2"><small>2</small></a>
22202 The getwc function is equivalent to fgetwc, except that if it is implemented as a
22203 macro, it may evaluate stream more than once, so the argument should never be an
22204 expression with side effects.
22206 <p><a name="7.29.3.6p3" href="#7.29.3.6p3"><small>3</small></a>
22207 The getwc function returns the next wide character from the input stream pointed to by
22210 <p><small><a href="#Contents">Contents</a></small>
22211 <h5><a name="7.29.3.7" href="#7.29.3.7">7.29.3.7 The getwchar function</a></h5>
22213 <p><a name="7.29.3.7p1" href="#7.29.3.7p1"><small>1</small></a>
22215 #include <a href="#7.29"><wchar.h></a>
22216 wint_t getwchar(void);
22218 <p><b>Description</b>
22219 <p><a name="7.29.3.7p2" href="#7.29.3.7p2"><small>2</small></a>
22220 The getwchar function is equivalent to getwc with the argument stdin.
22222 <p><a name="7.29.3.7p3" href="#7.29.3.7p3"><small>3</small></a>
22223 The getwchar function returns the next wide character from the input stream pointed to
22226 <p><small><a href="#Contents">Contents</a></small>
22227 <h5><a name="7.29.3.8" href="#7.29.3.8">7.29.3.8 The putwc function</a></h5>
22229 <p><a name="7.29.3.8p1" href="#7.29.3.8p1"><small>1</small></a>
22231 #include <a href="#7.21"><stdio.h></a>
22232 #include <a href="#7.29"><wchar.h></a>
22233 wint_t putwc(wchar_t c, FILE *stream);
22235 <p><b>Description</b>
22236 <p><a name="7.29.3.8p2" href="#7.29.3.8p2"><small>2</small></a>
22237 The putwc function is equivalent to fputwc, except that if it is implemented as a
22238 macro, it may evaluate stream more than once, so that argument should never be an
22239 expression with side effects.
22241 <p><a name="7.29.3.8p3" href="#7.29.3.8p3"><small>3</small></a>
22242 The putwc function returns the wide character written, or WEOF.
22245 <p><small><a href="#Contents">Contents</a></small>
22246 <h5><a name="7.29.3.9" href="#7.29.3.9">7.29.3.9 The putwchar function</a></h5>
22248 <p><a name="7.29.3.9p1" href="#7.29.3.9p1"><small>1</small></a>
22250 #include <a href="#7.29"><wchar.h></a>
22251 wint_t putwchar(wchar_t c);
22253 <p><b>Description</b>
22254 <p><a name="7.29.3.9p2" href="#7.29.3.9p2"><small>2</small></a>
22255 The putwchar function is equivalent to putwc with the second argument stdout.
22257 <p><a name="7.29.3.9p3" href="#7.29.3.9p3"><small>3</small></a>
22258 The putwchar function returns the character written, or WEOF.
22260 <p><small><a href="#Contents">Contents</a></small>
22261 <h5><a name="7.29.3.10" href="#7.29.3.10">7.29.3.10 The ungetwc function</a></h5>
22263 <p><a name="7.29.3.10p1" href="#7.29.3.10p1"><small>1</small></a>
22265 #include <a href="#7.21"><stdio.h></a>
22266 #include <a href="#7.29"><wchar.h></a>
22267 wint_t ungetwc(wint_t c, FILE *stream);
22269 <p><b>Description</b>
22270 <p><a name="7.29.3.10p2" href="#7.29.3.10p2"><small>2</small></a>
22271 The ungetwc function pushes the wide character specified by c back onto the input
22272 stream pointed to by stream. Pushed-back wide characters will be returned by
22273 subsequent reads on that stream in the reverse order of their pushing. A successful
22274 intervening call (with the stream pointed to by stream) to a file positioning function
22275 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
22276 stream. The external storage corresponding to the stream is unchanged.
22277 <p><a name="7.29.3.10p3" href="#7.29.3.10p3"><small>3</small></a>
22278 One wide character of pushback is guaranteed, even if the call to the ungetwc function
22279 follows just after a call to a formatted wide character input function fwscanf,
22280 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
22281 on the same stream without an intervening read or file positioning operation on that
22282 stream, the operation may fail.
22283 <p><a name="7.29.3.10p4" href="#7.29.3.10p4"><small>4</small></a>
22284 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
22286 <p><a name="7.29.3.10p5" href="#7.29.3.10p5"><small>5</small></a>
22287 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
22288 The value of the file position indicator for the stream after reading or discarding all
22289 pushed-back wide characters is the same as it was before the wide characters were pushed
22290 back. For a text or binary stream, the value of its file position indicator after a successful
22291 call to the ungetwc function is unspecified until all pushed-back wide characters are
22295 <p><a name="7.29.3.10p6" href="#7.29.3.10p6"><small>6</small></a>
22296 The ungetwc function returns the wide character pushed back, or WEOF if the operation
22299 <p><small><a href="#Contents">Contents</a></small>
22300 <h4><a name="7.29.4" href="#7.29.4">7.29.4 General wide string utilities</a></h4>
22301 <p><a name="7.29.4p1" href="#7.29.4p1"><small>1</small></a>
22302 The header <a href="#7.29"><wchar.h></a> declares a number of functions useful for wide string
22303 manipulation. Various methods are used for determining the lengths of the arrays, but in
22304 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
22305 array. If an array is accessed beyond the end of an object, the behavior is undefined.
22306 <p><a name="7.29.4p2" href="#7.29.4p2"><small>2</small></a>
22307 Where an argument declared as size_t n determines the length of the array for a
22308 function, n can have the value zero on a call to that function. Unless explicitly stated
22309 otherwise in the description of a particular function in this subclause, pointer arguments
22310 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
22311 function that locates a wide character finds no occurrence, a function that compares two
22312 wide character sequences returns zero, and a function that copies wide characters copies
22313 zero wide characters.
22315 <p><small><a href="#Contents">Contents</a></small>
22316 <h5><a name="7.29.4.1" href="#7.29.4.1">7.29.4.1 Wide string numeric conversion functions</a></h5>
22318 <p><small><a href="#Contents">Contents</a></small>
22319 <h5><a name="7.29.4.1.1" href="#7.29.4.1.1">7.29.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
22321 <p><a name="7.29.4.1.1p1" href="#7.29.4.1.1p1"><small>1</small></a>
22323 #include <a href="#7.29"><wchar.h></a>
22324 double wcstod(const wchar_t * restrict nptr,
22325 wchar_t ** restrict endptr);
22326 float wcstof(const wchar_t * restrict nptr,
22327 wchar_t ** restrict endptr);
22328 long double wcstold(const wchar_t * restrict nptr,
22329 wchar_t ** restrict endptr);
22331 <p><b>Description</b>
22332 <p><a name="7.29.4.1.1p2" href="#7.29.4.1.1p2"><small>2</small></a>
22333 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
22334 string pointed to by nptr to double, float, and long double representation,
22335 respectively. First, they decompose the input string into three parts: an initial, possibly
22336 empty, sequence of white-space wide characters (as specified by the iswspace
22337 function), a subject sequence resembling a floating-point constant or representing an
22338 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
22339 including the terminating null wide character of the input wide string. Then, they attempt
22340 to convert the subject sequence to a floating-point number, and return the result.
22341 <p><a name="7.29.4.1.1p3" href="#7.29.4.1.1p3"><small>3</small></a>
22342 The expected form of the subject sequence is an optional plus or minus sign, then one of
22346 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
22347 character, then an optional exponent part as defined for the corresponding single-byte
22348 characters in <a href="#6.4.4.2">6.4.4.2</a>;
22349 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
22350 decimal-point wide character, then an optional binary exponent part as defined in
22351 <a href="#6.4.4.2">6.4.4.2</a>;
22352 <li> INF or INFINITY, or any other wide string equivalent except for case
22353 <li> NAN or NAN(n-wchar-sequence<sub>opt</sub>), or any other wide string equivalent except for
22354 case in the NAN part, where:
22359 n-wchar-sequence digit
22360 n-wchar-sequence nondigit
22363 The subject sequence is defined as the longest initial subsequence of the input wide
22364 string, starting with the first non-white-space wide character, that is of the expected form.
22365 The subject sequence contains no wide characters if the input wide string is not of the
22367 <p><a name="7.29.4.1.1p4" href="#7.29.4.1.1p4"><small>4</small></a>
22368 If the subject sequence has the expected form for a floating-point number, the sequence of
22369 wide characters starting with the first digit or the decimal-point wide character
22370 (whichever occurs first) is interpreted as a floating constant according to the rules of
22371 <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
22372 if neither an exponent part nor a decimal-point wide character appears in a decimal
22373 floating point number, or if a binary exponent part does not appear in a hexadecimal
22374 floating point number, an exponent part of the appropriate type with value zero is
22375 assumed to follow the last digit in the string. If the subject sequence begins with a minus
22376 sign, the sequence is interpreted as negated.<sup><a href="#note343"><b>343)</b></a></sup> A wide character sequence INF or
22377 INFINITY is interpreted as an infinity, if representable in the return type, else like a
22378 floating constant that is too large for the range of the return type. A wide character
22379 sequence NAN or NAN(n-wchar-sequence<sub>opt</sub>) is interpreted as a quiet NaN, if supported
22380 in the return type, else like a subject sequence part that does not have the expected form;
22381 the meaning of the n-wchar sequence is implementation-defined.<sup><a href="#note344"><b>344)</b></a></sup> A pointer to the
22384 final wide string is stored in the object pointed to by endptr, provided that endptr is
22385 not a null pointer.
22386 <p><a name="7.29.4.1.1p5" href="#7.29.4.1.1p5"><small>5</small></a>
22387 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
22388 value resulting from the conversion is correctly rounded.
22389 <p><a name="7.29.4.1.1p6" href="#7.29.4.1.1p6"><small>6</small></a>
22390 In other than the "C" locale, additional locale-specific subject sequence forms may be
22392 <p><a name="7.29.4.1.1p7" href="#7.29.4.1.1p7"><small>7</small></a>
22393 If the subject sequence is empty or does not have the expected form, no conversion is
22394 performed; the value of nptr is stored in the object pointed to by endptr, provided
22395 that endptr is not a null pointer.
22396 <p><b>Recommended practice</b>
22397 <p><a name="7.29.4.1.1p8" href="#7.29.4.1.1p8"><small>8</small></a>
22398 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
22399 the result is not exactly representable, the result should be one of the two numbers in the
22400 appropriate internal format that are adjacent to the hexadecimal floating source value,
22401 with the extra stipulation that the error should have a correct sign for the current rounding
22403 <p><a name="7.29.4.1.1p9" href="#7.29.4.1.1p9"><small>9</small></a>
22404 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
22405 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
22406 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
22407 consider the two bounding, adjacent decimal strings L and U, both having
22408 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
22409 The result should be one of the (equal or adjacent) values that would be obtained by
22410 correctly rounding L and U according to the current rounding direction, with the extra
22411 stipulation that the error with respect to D should have a correct sign for the current
22412 rounding direction.<sup><a href="#note345"><b>345)</b></a></sup>
22414 <p><a name="7.29.4.1.1p10" href="#7.29.4.1.1p10"><small>10</small></a>
22415 The functions return the converted value, if any. If no conversion could be performed,
22416 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
22417 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
22418 return type and sign of the value), and the value of the macro ERANGE is stored in
22419 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
22420 no greater than the smallest normalized positive number in the return type; whether
22421 errno acquires the value ERANGE is implementation-defined.
22428 <p><b>Footnotes</b>
22429 <p><small><a name="note343" href="#note343">343)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
22430 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
22431 methods may yield different results if rounding is toward positive or negative infinity. In either case,
22432 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
22434 <p><small><a name="note344" href="#note344">344)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
22435 the NaN's significand.
22437 <p><small><a name="note345" href="#note345">345)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
22438 to the same internal floating value, but if not will round to adjacent values.
22441 <p><small><a href="#Contents">Contents</a></small>
22442 <h5><a name="7.29.4.1.2" href="#7.29.4.1.2">7.29.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
22444 <p><a name="7.29.4.1.2p1" href="#7.29.4.1.2p1"><small>1</small></a>
22446 #include <a href="#7.29"><wchar.h></a>
22448 const wchar_t * restrict nptr,
22449 wchar_t ** restrict endptr,
22451 long long int wcstoll(
22452 const wchar_t * restrict nptr,
22453 wchar_t ** restrict endptr,
22455 unsigned long int wcstoul(
22456 const wchar_t * restrict nptr,
22457 wchar_t ** restrict endptr,
22459 unsigned long long int wcstoull(
22460 const wchar_t * restrict nptr,
22461 wchar_t ** restrict endptr,
22464 <p><b>Description</b>
22465 <p><a name="7.29.4.1.2p2" href="#7.29.4.1.2p2"><small>2</small></a>
22466 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
22467 portion of the wide string pointed to by nptr to long int, long long int,
22468 unsigned long int, and unsigned long long int representation,
22469 respectively. First, they decompose the input string into three parts: an initial, possibly
22470 empty, sequence of white-space wide characters (as specified by the iswspace
22471 function), a subject sequence resembling an integer represented in some radix determined
22472 by the value of base, and a final wide string of one or more unrecognized wide
22473 characters, including the terminating null wide character of the input wide string. Then,
22474 they attempt to convert the subject sequence to an integer, and return the result.
22475 <p><a name="7.29.4.1.2p3" href="#7.29.4.1.2p3"><small>3</small></a>
22476 If the value of base is zero, the expected form of the subject sequence is that of an
22477 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
22478 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
22479 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
22480 is a sequence of letters and digits representing an integer with the radix specified by
22481 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
22482 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
22483 letters and digits whose ascribed values are less than that of base are permitted. If the
22484 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
22485 of letters and digits, following the sign if present.
22487 <p><a name="7.29.4.1.2p4" href="#7.29.4.1.2p4"><small>4</small></a>
22488 The subject sequence is defined as the longest initial subsequence of the input wide
22489 string, starting with the first non-white-space wide character, that is of the expected form.
22490 The subject sequence contains no wide characters if the input wide string is empty or
22491 consists entirely of white space, or if the first non-white-space wide character is other
22492 than a sign or a permissible letter or digit.
22493 <p><a name="7.29.4.1.2p5" href="#7.29.4.1.2p5"><small>5</small></a>
22494 If the subject sequence has the expected form and the value of base is zero, the sequence
22495 of wide characters starting with the first digit is interpreted as an integer constant
22496 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
22497 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
22498 letter its value as given above. If the subject sequence begins with a minus sign, the value
22499 resulting from the conversion is negated (in the return type). A pointer to the final wide
22500 string is stored in the object pointed to by endptr, provided that endptr is not a null
22502 <p><a name="7.29.4.1.2p6" href="#7.29.4.1.2p6"><small>6</small></a>
22503 In other than the "C" locale, additional locale-specific subject sequence forms may be
22505 <p><a name="7.29.4.1.2p7" href="#7.29.4.1.2p7"><small>7</small></a>
22506 If the subject sequence is empty or does not have the expected form, no conversion is
22507 performed; the value of nptr is stored in the object pointed to by endptr, provided
22508 that endptr is not a null pointer.
22510 <p><a name="7.29.4.1.2p8" href="#7.29.4.1.2p8"><small>8</small></a>
22511 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
22512 value, if any. If no conversion could be performed, zero is returned. If the correct value
22513 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
22514 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
22515 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
22517 <p><small><a href="#Contents">Contents</a></small>
22518 <h5><a name="7.29.4.2" href="#7.29.4.2">7.29.4.2 Wide string copying functions</a></h5>
22520 <p><small><a href="#Contents">Contents</a></small>
22521 <h5><a name="7.29.4.2.1" href="#7.29.4.2.1">7.29.4.2.1 The wcscpy function</a></h5>
22523 <p><a name="7.29.4.2.1p1" href="#7.29.4.2.1p1"><small>1</small></a>
22525 #include <a href="#7.29"><wchar.h></a>
22526 wchar_t *wcscpy(wchar_t * restrict s1,
22527 const wchar_t * restrict s2);
22529 <p><b>Description</b>
22530 <p><a name="7.29.4.2.1p2" href="#7.29.4.2.1p2"><small>2</small></a>
22531 The wcscpy function copies the wide string pointed to by s2 (including the terminating
22532 null wide character) into the array pointed to by s1.
22534 <p><a name="7.29.4.2.1p3" href="#7.29.4.2.1p3"><small>3</small></a>
22535 The wcscpy function returns the value of s1.
22538 <p><small><a href="#Contents">Contents</a></small>
22539 <h5><a name="7.29.4.2.2" href="#7.29.4.2.2">7.29.4.2.2 The wcsncpy function</a></h5>
22541 <p><a name="7.29.4.2.2p1" href="#7.29.4.2.2p1"><small>1</small></a>
22543 #include <a href="#7.29"><wchar.h></a>
22544 wchar_t *wcsncpy(wchar_t * restrict s1,
22545 const wchar_t * restrict s2,
22548 <p><b>Description</b>
22549 <p><a name="7.29.4.2.2p2" href="#7.29.4.2.2p2"><small>2</small></a>
22550 The wcsncpy function copies not more than n wide characters (those that follow a null
22551 wide character are not copied) from the array pointed to by s2 to the array pointed to by
22552 s1.<sup><a href="#note346"><b>346)</b></a></sup>
22553 <p><a name="7.29.4.2.2p3" href="#7.29.4.2.2p3"><small>3</small></a>
22554 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
22555 wide characters are appended to the copy in the array pointed to by s1, until n wide
22556 characters in all have been written.
22558 <p><a name="7.29.4.2.2p4" href="#7.29.4.2.2p4"><small>4</small></a>
22559 The wcsncpy function returns the value of s1.
22561 <p><b>Footnotes</b>
22562 <p><small><a name="note346" href="#note346">346)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
22563 result will not be null-terminated.
22566 <p><small><a href="#Contents">Contents</a></small>
22567 <h5><a name="7.29.4.2.3" href="#7.29.4.2.3">7.29.4.2.3 The wmemcpy function</a></h5>
22569 <p><a name="7.29.4.2.3p1" href="#7.29.4.2.3p1"><small>1</small></a>
22571 #include <a href="#7.29"><wchar.h></a>
22572 wchar_t *wmemcpy(wchar_t * restrict s1,
22573 const wchar_t * restrict s2,
22576 <p><b>Description</b>
22577 <p><a name="7.29.4.2.3p2" href="#7.29.4.2.3p2"><small>2</small></a>
22578 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
22579 object pointed to by s1.
22581 <p><a name="7.29.4.2.3p3" href="#7.29.4.2.3p3"><small>3</small></a>
22582 The wmemcpy function returns the value of s1.
22589 <p><small><a href="#Contents">Contents</a></small>
22590 <h5><a name="7.29.4.2.4" href="#7.29.4.2.4">7.29.4.2.4 The wmemmove function</a></h5>
22592 <p><a name="7.29.4.2.4p1" href="#7.29.4.2.4p1"><small>1</small></a>
22594 #include <a href="#7.29"><wchar.h></a>
22595 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
22598 <p><b>Description</b>
22599 <p><a name="7.29.4.2.4p2" href="#7.29.4.2.4p2"><small>2</small></a>
22600 The wmemmove function copies n wide characters from the object pointed to by s2 to
22601 the object pointed to by s1. Copying takes place as if the n wide characters from the
22602 object pointed to by s2 are first copied into a temporary array of n wide characters that
22603 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
22604 the temporary array are copied into the object pointed to by s1.
22606 <p><a name="7.29.4.2.4p3" href="#7.29.4.2.4p3"><small>3</small></a>
22607 The wmemmove function returns the value of s1.
22609 <p><small><a href="#Contents">Contents</a></small>
22610 <h5><a name="7.29.4.3" href="#7.29.4.3">7.29.4.3 Wide string concatenation functions</a></h5>
22612 <p><small><a href="#Contents">Contents</a></small>
22613 <h5><a name="7.29.4.3.1" href="#7.29.4.3.1">7.29.4.3.1 The wcscat function</a></h5>
22615 <p><a name="7.29.4.3.1p1" href="#7.29.4.3.1p1"><small>1</small></a>
22617 #include <a href="#7.29"><wchar.h></a>
22618 wchar_t *wcscat(wchar_t * restrict s1,
22619 const wchar_t * restrict s2);
22621 <p><b>Description</b>
22622 <p><a name="7.29.4.3.1p2" href="#7.29.4.3.1p2"><small>2</small></a>
22623 The wcscat function appends a copy of the wide string pointed to by s2 (including the
22624 terminating null wide character) to the end of the wide string pointed to by s1. The initial
22625 wide character of s2 overwrites the null wide character at the end of s1.
22627 <p><a name="7.29.4.3.1p3" href="#7.29.4.3.1p3"><small>3</small></a>
22628 The wcscat function returns the value of s1.
22630 <p><small><a href="#Contents">Contents</a></small>
22631 <h5><a name="7.29.4.3.2" href="#7.29.4.3.2">7.29.4.3.2 The wcsncat function</a></h5>
22633 <p><a name="7.29.4.3.2p1" href="#7.29.4.3.2p1"><small>1</small></a>
22635 #include <a href="#7.29"><wchar.h></a>
22636 wchar_t *wcsncat(wchar_t * restrict s1,
22637 const wchar_t * restrict s2,
22640 <p><b>Description</b>
22641 <p><a name="7.29.4.3.2p2" href="#7.29.4.3.2p2"><small>2</small></a>
22642 The wcsncat function appends not more than n wide characters (a null wide character
22643 and those that follow it are not appended) from the array pointed to by s2 to the end of
22645 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
22646 wide character at the end of s1. A terminating null wide character is always appended to
22647 the result.<sup><a href="#note347"><b>347)</b></a></sup>
22649 <p><a name="7.29.4.3.2p3" href="#7.29.4.3.2p3"><small>3</small></a>
22650 The wcsncat function returns the value of s1.
22652 <p><b>Footnotes</b>
22653 <p><small><a name="note347" href="#note347">347)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
22657 <p><small><a href="#Contents">Contents</a></small>
22658 <h5><a name="7.29.4.4" href="#7.29.4.4">7.29.4.4 Wide string comparison functions</a></h5>
22659 <p><a name="7.29.4.4p1" href="#7.29.4.4p1"><small>1</small></a>
22660 Unless explicitly stated otherwise, the functions described in this subclause order two
22661 wide characters the same way as two integers of the underlying integer type designated
22664 <p><small><a href="#Contents">Contents</a></small>
22665 <h5><a name="7.29.4.4.1" href="#7.29.4.4.1">7.29.4.4.1 The wcscmp function</a></h5>
22667 <p><a name="7.29.4.4.1p1" href="#7.29.4.4.1p1"><small>1</small></a>
22669 #include <a href="#7.29"><wchar.h></a>
22670 int wcscmp(const wchar_t *s1, const wchar_t *s2);
22672 <p><b>Description</b>
22673 <p><a name="7.29.4.4.1p2" href="#7.29.4.4.1p2"><small>2</small></a>
22674 The wcscmp function compares the wide string pointed to by s1 to the wide string
22677 <p><a name="7.29.4.4.1p3" href="#7.29.4.4.1p3"><small>3</small></a>
22678 The wcscmp function returns an integer greater than, equal to, or less than zero,
22679 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
22680 wide string pointed to by s2.
22682 <p><small><a href="#Contents">Contents</a></small>
22683 <h5><a name="7.29.4.4.2" href="#7.29.4.4.2">7.29.4.4.2 The wcscoll function</a></h5>
22685 <p><a name="7.29.4.4.2p1" href="#7.29.4.4.2p1"><small>1</small></a>
22687 #include <a href="#7.29"><wchar.h></a>
22688 int wcscoll(const wchar_t *s1, const wchar_t *s2);
22690 <p><b>Description</b>
22691 <p><a name="7.29.4.4.2p2" href="#7.29.4.4.2p2"><small>2</small></a>
22692 The wcscoll function compares the wide string pointed to by s1 to the wide string
22693 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
22696 <p><a name="7.29.4.4.2p3" href="#7.29.4.4.2p3"><small>3</small></a>
22697 The wcscoll function returns an integer greater than, equal to, or less than zero,
22698 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
22702 wide string pointed to by s2 when both are interpreted as appropriate to the current
22705 <p><small><a href="#Contents">Contents</a></small>
22706 <h5><a name="7.29.4.4.3" href="#7.29.4.4.3">7.29.4.4.3 The wcsncmp function</a></h5>
22708 <p><a name="7.29.4.4.3p1" href="#7.29.4.4.3p1"><small>1</small></a>
22710 #include <a href="#7.29"><wchar.h></a>
22711 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
22714 <p><b>Description</b>
22715 <p><a name="7.29.4.4.3p2" href="#7.29.4.4.3p2"><small>2</small></a>
22716 The wcsncmp function compares not more than n wide characters (those that follow a
22717 null wide character are not compared) from the array pointed to by s1 to the array
22720 <p><a name="7.29.4.4.3p3" href="#7.29.4.4.3p3"><small>3</small></a>
22721 The wcsncmp function returns an integer greater than, equal to, or less than zero,
22722 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
22723 to, or less than the possibly null-terminated array pointed to by s2.
22725 <p><small><a href="#Contents">Contents</a></small>
22726 <h5><a name="7.29.4.4.4" href="#7.29.4.4.4">7.29.4.4.4 The wcsxfrm function</a></h5>
22728 <p><a name="7.29.4.4.4p1" href="#7.29.4.4.4p1"><small>1</small></a>
22730 #include <a href="#7.29"><wchar.h></a>
22731 size_t wcsxfrm(wchar_t * restrict s1,
22732 const wchar_t * restrict s2,
22735 <p><b>Description</b>
22736 <p><a name="7.29.4.4.4p2" href="#7.29.4.4.4p2"><small>2</small></a>
22737 The wcsxfrm function transforms the wide string pointed to by s2 and places the
22738 resulting wide string into the array pointed to by s1. The transformation is such that if
22739 the wcscmp function is applied to two transformed wide strings, it returns a value greater
22740 than, equal to, or less than zero, corresponding to the result of the wcscoll function
22741 applied to the same two original wide strings. No more than n wide characters are placed
22742 into the resulting array pointed to by s1, including the terminating null wide character. If
22743 n is zero, s1 is permitted to be a null pointer.
22745 <p><a name="7.29.4.4.4p3" href="#7.29.4.4.4p3"><small>3</small></a>
22746 The wcsxfrm function returns the length of the transformed wide string (not including
22747 the terminating null wide character). If the value returned is n or greater, the contents of
22748 the array pointed to by s1 are indeterminate.
22749 <p><a name="7.29.4.4.4p4" href="#7.29.4.4.4p4"><small>4</small></a>
22750 EXAMPLE The value of the following expression is the length of the array needed to hold the
22751 transformation of the wide string pointed to by s:
22754 1 + wcsxfrm(NULL, s, 0)
22758 <p><small><a href="#Contents">Contents</a></small>
22759 <h5><a name="7.29.4.4.5" href="#7.29.4.4.5">7.29.4.4.5 The wmemcmp function</a></h5>
22761 <p><a name="7.29.4.4.5p1" href="#7.29.4.4.5p1"><small>1</small></a>
22763 #include <a href="#7.29"><wchar.h></a>
22764 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
22767 <p><b>Description</b>
22768 <p><a name="7.29.4.4.5p2" href="#7.29.4.4.5p2"><small>2</small></a>
22769 The wmemcmp function compares the first n wide characters of the object pointed to by
22770 s1 to the first n wide characters of the object pointed to by s2.
22772 <p><a name="7.29.4.4.5p3" href="#7.29.4.4.5p3"><small>3</small></a>
22773 The wmemcmp function returns an integer greater than, equal to, or less than zero,
22774 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
22777 <p><small><a href="#Contents">Contents</a></small>
22778 <h5><a name="7.29.4.5" href="#7.29.4.5">7.29.4.5 Wide string search functions</a></h5>
22780 <p><small><a href="#Contents">Contents</a></small>
22781 <h5><a name="7.29.4.5.1" href="#7.29.4.5.1">7.29.4.5.1 The wcschr function</a></h5>
22783 <p><a name="7.29.4.5.1p1" href="#7.29.4.5.1p1"><small>1</small></a>
22785 #include <a href="#7.29"><wchar.h></a>
22786 wchar_t *wcschr(const wchar_t *s, wchar_t c);
22788 <p><b>Description</b>
22789 <p><a name="7.29.4.5.1p2" href="#7.29.4.5.1p2"><small>2</small></a>
22790 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
22791 The terminating null wide character is considered to be part of the wide string.
22793 <p><a name="7.29.4.5.1p3" href="#7.29.4.5.1p3"><small>3</small></a>
22794 The wcschr function returns a pointer to the located wide character, or a null pointer if
22795 the wide character does not occur in the wide string.
22797 <p><small><a href="#Contents">Contents</a></small>
22798 <h5><a name="7.29.4.5.2" href="#7.29.4.5.2">7.29.4.5.2 The wcscspn function</a></h5>
22800 <p><a name="7.29.4.5.2p1" href="#7.29.4.5.2p1"><small>1</small></a>
22802 #include <a href="#7.29"><wchar.h></a>
22803 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
22805 <p><b>Description</b>
22806 <p><a name="7.29.4.5.2p2" href="#7.29.4.5.2p2"><small>2</small></a>
22807 The wcscspn function computes the length of the maximum initial segment of the wide
22808 string pointed to by s1 which consists entirely of wide characters not from the wide
22809 string pointed to by s2.
22812 <p><a name="7.29.4.5.2p3" href="#7.29.4.5.2p3"><small>3</small></a>
22813 The wcscspn function returns the length of the segment.
22815 <p><small><a href="#Contents">Contents</a></small>
22816 <h5><a name="7.29.4.5.3" href="#7.29.4.5.3">7.29.4.5.3 The wcspbrk function</a></h5>
22818 <p><a name="7.29.4.5.3p1" href="#7.29.4.5.3p1"><small>1</small></a>
22820 #include <a href="#7.29"><wchar.h></a>
22821 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
22823 <p><b>Description</b>
22824 <p><a name="7.29.4.5.3p2" href="#7.29.4.5.3p2"><small>2</small></a>
22825 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
22826 any wide character from the wide string pointed to by s2.
22828 <p><a name="7.29.4.5.3p3" href="#7.29.4.5.3p3"><small>3</small></a>
22829 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
22830 no wide character from s2 occurs in s1.
22832 <p><small><a href="#Contents">Contents</a></small>
22833 <h5><a name="7.29.4.5.4" href="#7.29.4.5.4">7.29.4.5.4 The wcsrchr function</a></h5>
22835 <p><a name="7.29.4.5.4p1" href="#7.29.4.5.4p1"><small>1</small></a>
22837 #include <a href="#7.29"><wchar.h></a>
22838 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
22840 <p><b>Description</b>
22841 <p><a name="7.29.4.5.4p2" href="#7.29.4.5.4p2"><small>2</small></a>
22842 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
22843 s. The terminating null wide character is considered to be part of the wide string.
22845 <p><a name="7.29.4.5.4p3" href="#7.29.4.5.4p3"><small>3</small></a>
22846 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
22847 not occur in the wide string.
22849 <p><small><a href="#Contents">Contents</a></small>
22850 <h5><a name="7.29.4.5.5" href="#7.29.4.5.5">7.29.4.5.5 The wcsspn function</a></h5>
22852 <p><a name="7.29.4.5.5p1" href="#7.29.4.5.5p1"><small>1</small></a>
22854 #include <a href="#7.29"><wchar.h></a>
22855 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
22857 <p><b>Description</b>
22858 <p><a name="7.29.4.5.5p2" href="#7.29.4.5.5p2"><small>2</small></a>
22859 The wcsspn function computes the length of the maximum initial segment of the wide
22860 string pointed to by s1 which consists entirely of wide characters from the wide string
22863 <p><a name="7.29.4.5.5p3" href="#7.29.4.5.5p3"><small>3</small></a>
22864 The wcsspn function returns the length of the segment.
22867 <p><small><a href="#Contents">Contents</a></small>
22868 <h5><a name="7.29.4.5.6" href="#7.29.4.5.6">7.29.4.5.6 The wcsstr function</a></h5>
22870 <p><a name="7.29.4.5.6p1" href="#7.29.4.5.6p1"><small>1</small></a>
22872 #include <a href="#7.29"><wchar.h></a>
22873 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
22875 <p><b>Description</b>
22876 <p><a name="7.29.4.5.6p2" href="#7.29.4.5.6p2"><small>2</small></a>
22877 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
22878 the sequence of wide characters (excluding the terminating null wide character) in the
22879 wide string pointed to by s2.
22881 <p><a name="7.29.4.5.6p3" href="#7.29.4.5.6p3"><small>3</small></a>
22882 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
22883 wide string is not found. If s2 points to a wide string with zero length, the function
22886 <p><small><a href="#Contents">Contents</a></small>
22887 <h5><a name="7.29.4.5.7" href="#7.29.4.5.7">7.29.4.5.7 The wcstok function</a></h5>
22889 <p><a name="7.29.4.5.7p1" href="#7.29.4.5.7p1"><small>1</small></a>
22891 #include <a href="#7.29"><wchar.h></a>
22892 wchar_t *wcstok(wchar_t * restrict s1,
22893 const wchar_t * restrict s2,
22894 wchar_t ** restrict ptr);
22896 <p><b>Description</b>
22897 <p><a name="7.29.4.5.7p2" href="#7.29.4.5.7p2"><small>2</small></a>
22898 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
22899 a sequence of tokens, each of which is delimited by a wide character from the wide string
22900 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
22901 which the wcstok function stores information necessary for it to continue scanning the
22903 <p><a name="7.29.4.5.7p3" href="#7.29.4.5.7p3"><small>3</small></a>
22904 The first call in a sequence has a non-null first argument and stores an initial value in the
22905 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
22906 the object pointed to by ptr is required to have the value stored by the previous call in
22907 the sequence, which is then updated. The separator wide string pointed to by s2 may be
22908 different from call to call.
22909 <p><a name="7.29.4.5.7p4" href="#7.29.4.5.7p4"><small>4</small></a>
22910 The first call in the sequence searches the wide string pointed to by s1 for the first wide
22911 character that is not contained in the current separator wide string pointed to by s2. If no
22912 such wide character is found, then there are no tokens in the wide string pointed to by s1
22913 and the wcstok function returns a null pointer. If such a wide character is found, it is
22914 the start of the first token.
22915 <p><a name="7.29.4.5.7p5" href="#7.29.4.5.7p5"><small>5</small></a>
22916 The wcstok function then searches from there for a wide character that is contained in
22917 the current separator wide string. If no such wide character is found, the current token
22919 extends to the end of the wide string pointed to by s1, and subsequent searches in the
22920 same wide string for a token return a null pointer. If such a wide character is found, it is
22921 overwritten by a null wide character, which terminates the current token.
22922 <p><a name="7.29.4.5.7p6" href="#7.29.4.5.7p6"><small>6</small></a>
22923 In all cases, the wcstok function stores sufficient information in the pointer pointed to
22924 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
22925 value for ptr, shall start searching just past the element overwritten by a null wide
22926 character (if any).
22928 <p><a name="7.29.4.5.7p7" href="#7.29.4.5.7p7"><small>7</small></a>
22929 The wcstok function returns a pointer to the first wide character of a token, or a null
22930 pointer if there is no token.
22931 <p><a name="7.29.4.5.7p8" href="#7.29.4.5.7p8"><small>8</small></a>
22934 #include <a href="#7.29"><wchar.h></a>
22935 static wchar_t str1[] = L"?a???b,,,#c";
22936 static wchar_t str2[] = L"\t \t";
22937 wchar_t *t, *ptr1, *ptr2;
22938 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
22939 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
22940 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
22941 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
22942 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
22946 <p><small><a href="#Contents">Contents</a></small>
22947 <h5><a name="7.29.4.5.8" href="#7.29.4.5.8">7.29.4.5.8 The wmemchr function</a></h5>
22949 <p><a name="7.29.4.5.8p1" href="#7.29.4.5.8p1"><small>1</small></a>
22951 #include <a href="#7.29"><wchar.h></a>
22952 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
22955 <p><b>Description</b>
22956 <p><a name="7.29.4.5.8p2" href="#7.29.4.5.8p2"><small>2</small></a>
22957 The wmemchr function locates the first occurrence of c in the initial n wide characters of
22958 the object pointed to by s.
22960 <p><a name="7.29.4.5.8p3" href="#7.29.4.5.8p3"><small>3</small></a>
22961 The wmemchr function returns a pointer to the located wide character, or a null pointer if
22962 the wide character does not occur in the object.
22965 <p><small><a href="#Contents">Contents</a></small>
22966 <h5><a name="7.29.4.6" href="#7.29.4.6">7.29.4.6 Miscellaneous functions</a></h5>
22968 <p><small><a href="#Contents">Contents</a></small>
22969 <h5><a name="7.29.4.6.1" href="#7.29.4.6.1">7.29.4.6.1 The wcslen function</a></h5>
22971 <p><a name="7.29.4.6.1p1" href="#7.29.4.6.1p1"><small>1</small></a>
22973 #include <a href="#7.29"><wchar.h></a>
22974 size_t wcslen(const wchar_t *s);
22976 <p><b>Description</b>
22977 <p><a name="7.29.4.6.1p2" href="#7.29.4.6.1p2"><small>2</small></a>
22978 The wcslen function computes the length of the wide string pointed to by s.
22980 <p><a name="7.29.4.6.1p3" href="#7.29.4.6.1p3"><small>3</small></a>
22981 The wcslen function returns the number of wide characters that precede the terminating
22982 null wide character.
22984 <p><small><a href="#Contents">Contents</a></small>
22985 <h5><a name="7.29.4.6.2" href="#7.29.4.6.2">7.29.4.6.2 The wmemset function</a></h5>
22987 <p><a name="7.29.4.6.2p1" href="#7.29.4.6.2p1"><small>1</small></a>
22989 #include <a href="#7.29"><wchar.h></a>
22990 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
22992 <p><b>Description</b>
22993 <p><a name="7.29.4.6.2p2" href="#7.29.4.6.2p2"><small>2</small></a>
22994 The wmemset function copies the value of c into each of the first n wide characters of
22995 the object pointed to by s.
22997 <p><a name="7.29.4.6.2p3" href="#7.29.4.6.2p3"><small>3</small></a>
22998 The wmemset function returns the value of s.
23000 <p><small><a href="#Contents">Contents</a></small>
23001 <h4><a name="7.29.5" href="#7.29.5">7.29.5 Wide character time conversion functions</a></h4>
23003 <p><small><a href="#Contents">Contents</a></small>
23004 <h5><a name="7.29.5.1" href="#7.29.5.1">7.29.5.1 The wcsftime function</a></h5>
23006 <p><a name="7.29.5.1p1" href="#7.29.5.1p1"><small>1</small></a>
23008 #include <a href="#7.27"><time.h></a>
23009 #include <a href="#7.29"><wchar.h></a>
23010 size_t wcsftime(wchar_t * restrict s,
23012 const wchar_t * restrict format,
23013 const struct tm * restrict timeptr);
23015 <p><b>Description</b>
23016 <p><a name="7.29.5.1p2" href="#7.29.5.1p2"><small>2</small></a>
23017 The wcsftime function is equivalent to the strftime function, except that:
23019 <li> The argument s points to the initial element of an array of wide characters into which
23020 the generated output is to be placed.
23022 <li> The argument maxsize indicates the limiting number of wide characters.
23023 <li> The argument format is a wide string and the conversion specifiers are replaced by
23024 corresponding sequences of wide characters.
23025 <li> The return value indicates the number of wide characters.
23028 <p><a name="7.29.5.1p3" href="#7.29.5.1p3"><small>3</small></a>
23029 If the total number of resulting wide characters including the terminating null wide
23030 character is not more than maxsize, the wcsftime function returns the number of
23031 wide characters placed into the array pointed to by s not including the terminating null
23032 wide character. Otherwise, zero is returned and the contents of the array are
23035 <p><small><a href="#Contents">Contents</a></small>
23036 <h4><a name="7.29.6" href="#7.29.6">7.29.6 Extended multibyte/wide character conversion utilities</a></h4>
23037 <p><a name="7.29.6p1" href="#7.29.6p1"><small>1</small></a>
23038 The header <a href="#7.29"><wchar.h></a> declares an extended set of functions useful for conversion
23039 between multibyte characters and wide characters.
23040 <p><a name="7.29.6p2" href="#7.29.6p2"><small>2</small></a>
23041 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.29.6.3">7.29.6.3</a> and
23042 <a href="#7.29.6.4">7.29.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
23043 to describe the current conversion state from a particular multibyte character sequence to
23044 a wide character sequence (or the reverse) under the rules of a particular setting for the
23045 LC_CTYPE category of the current locale.
23046 <p><a name="7.29.6p3" href="#7.29.6p3"><small>3</small></a>
23047 The initial conversion state corresponds, for a conversion in either direction, to the
23048 beginning of a new multibyte character in the initial shift state. A zero-valued
23049 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
23050 valued mbstate_t object can be used to initiate conversion involving any multibyte
23051 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
23052 been altered by any of the functions described in this subclause, and is then used with a
23053 different multibyte character sequence, or in the other conversion direction, or with a
23054 different LC_CTYPE category setting than on earlier function calls, the behavior is
23055 undefined.<sup><a href="#note348"><b>348)</b></a></sup>
23056 <p><a name="7.29.6p4" href="#7.29.6p4"><small>4</small></a>
23057 On entry, each function takes the described conversion state (either internal or pointed to
23058 by an argument) as current. The conversion state described by the referenced object is
23059 altered as needed to track the shift state, and the position within a multibyte character, for
23060 the associated multibyte character sequence.
23067 <p><b>Footnotes</b>
23068 <p><small><a name="note348" href="#note348">348)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
23069 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
23073 <p><small><a href="#Contents">Contents</a></small>
23074 <h5><a name="7.29.6.1" href="#7.29.6.1">7.29.6.1 Single-byte/wide character conversion functions</a></h5>
23076 <p><small><a href="#Contents">Contents</a></small>
23077 <h5><a name="7.29.6.1.1" href="#7.29.6.1.1">7.29.6.1.1 The btowc function</a></h5>
23079 <p><a name="7.29.6.1.1p1" href="#7.29.6.1.1p1"><small>1</small></a>
23081 #include <a href="#7.29"><wchar.h></a>
23082 wint_t btowc(int c);
23084 <p><b>Description</b>
23085 <p><a name="7.29.6.1.1p2" href="#7.29.6.1.1p2"><small>2</small></a>
23086 The btowc function determines whether c constitutes a valid single-byte character in the
23087 initial shift state.
23089 <p><a name="7.29.6.1.1p3" href="#7.29.6.1.1p3"><small>3</small></a>
23090 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
23091 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
23092 returns the wide character representation of that character.
23094 <p><small><a href="#Contents">Contents</a></small>
23095 <h5><a name="7.29.6.1.2" href="#7.29.6.1.2">7.29.6.1.2 The wctob function</a></h5>
23097 <p><a name="7.29.6.1.2p1" href="#7.29.6.1.2p1"><small>1</small></a>
23099 #include <a href="#7.29"><wchar.h></a>
23100 int wctob(wint_t c);
23102 <p><b>Description</b>
23103 <p><a name="7.29.6.1.2p2" href="#7.29.6.1.2p2"><small>2</small></a>
23104 The wctob function determines whether c corresponds to a member of the extended
23105 character set whose multibyte character representation is a single byte when in the initial
23108 <p><a name="7.29.6.1.2p3" href="#7.29.6.1.2p3"><small>3</small></a>
23109 The wctob function returns EOF if c does not correspond to a multibyte character with
23110 length one in the initial shift state. Otherwise, it returns the single-byte representation of
23111 that character as an unsigned char converted to an int.
23113 <p><small><a href="#Contents">Contents</a></small>
23114 <h5><a name="7.29.6.2" href="#7.29.6.2">7.29.6.2 Conversion state functions</a></h5>
23116 <p><small><a href="#Contents">Contents</a></small>
23117 <h5><a name="7.29.6.2.1" href="#7.29.6.2.1">7.29.6.2.1 The mbsinit function</a></h5>
23119 <p><a name="7.29.6.2.1p1" href="#7.29.6.2.1p1"><small>1</small></a>
23121 #include <a href="#7.29"><wchar.h></a>
23122 int mbsinit(const mbstate_t *ps);
23124 <p><b>Description</b>
23125 <p><a name="7.29.6.2.1p2" href="#7.29.6.2.1p2"><small>2</small></a>
23126 If ps is not a null pointer, the mbsinit function determines whether the referenced
23127 mbstate_t object describes an initial conversion state.
23130 <p><a name="7.29.6.2.1p3" href="#7.29.6.2.1p3"><small>3</small></a>
23131 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
23132 describes an initial conversion state; otherwise, it returns zero.
23134 <p><small><a href="#Contents">Contents</a></small>
23135 <h5><a name="7.29.6.3" href="#7.29.6.3">7.29.6.3 Restartable multibyte/wide character conversion functions</a></h5>
23136 <p><a name="7.29.6.3p1" href="#7.29.6.3p1"><small>1</small></a>
23137 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
23138 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
23139 pointer to mbstate_t that points to an object that can completely describe the current
23140 conversion state of the associated multibyte character sequence. If ps is a null pointer,
23141 each function uses its own internal mbstate_t object instead, which is initialized at
23142 program startup to the initial conversion state; the functions are not required to avoid data
23143 races with other calls to the same function in this case. The implementation behaves as if
23144 no library function calls these functions with a null pointer for ps.
23145 <p><a name="7.29.6.3p2" href="#7.29.6.3p2"><small>2</small></a>
23146 Also unlike their corresponding functions, the return value does not represent whether the
23147 encoding is state-dependent.
23149 <p><small><a href="#Contents">Contents</a></small>
23150 <h5><a name="7.29.6.3.1" href="#7.29.6.3.1">7.29.6.3.1 The mbrlen function</a></h5>
23152 <p><a name="7.29.6.3.1p1" href="#7.29.6.3.1p1"><small>1</small></a>
23154 #include <a href="#7.29"><wchar.h></a>
23155 size_t mbrlen(const char * restrict s,
23157 mbstate_t * restrict ps);
23159 <p><b>Description</b>
23160 <p><a name="7.29.6.3.1p2" href="#7.29.6.3.1p2"><small>2</small></a>
23161 The mbrlen function is equivalent to the call:
23163 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
23165 where internal is the mbstate_t object for the mbrlen function, except that the
23166 expression designated by ps is evaluated only once.
23168 <p><a name="7.29.6.3.1p3" href="#7.29.6.3.1p3"><small>3</small></a>
23169 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
23171 <p><b> Forward references</b>: the mbrtowc function (<a href="#7.29.6.3.2">7.29.6.3.2</a>).
23174 <p><small><a href="#Contents">Contents</a></small>
23175 <h5><a name="7.29.6.3.2" href="#7.29.6.3.2">7.29.6.3.2 The mbrtowc function</a></h5>
23177 <p><a name="7.29.6.3.2p1" href="#7.29.6.3.2p1"><small>1</small></a>
23179 #include <a href="#7.29"><wchar.h></a>
23180 size_t mbrtowc(wchar_t * restrict pwc,
23181 const char * restrict s,
23183 mbstate_t * restrict ps);
23185 <p><b>Description</b>
23186 <p><a name="7.29.6.3.2p2" href="#7.29.6.3.2p2"><small>2</small></a>
23187 If s is a null pointer, the mbrtowc function is equivalent to the call:
23189 mbrtowc(NULL, "", 1, ps)
23191 In this case, the values of the parameters pwc and n are ignored.
23192 <p><a name="7.29.6.3.2p3" href="#7.29.6.3.2p3"><small>3</small></a>
23193 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
23194 the byte pointed to by s to determine the number of bytes needed to complete the next
23195 multibyte character (including any shift sequences). If the function determines that the
23196 next multibyte character is complete and valid, it determines the value of the
23197 corresponding wide character and then, if pwc is not a null pointer, stores that value in
23198 the object pointed to by pwc. If the corresponding wide character is the null wide
23199 character, the resulting state described is the initial conversion state.
23201 <p><a name="7.29.6.3.2p4" href="#7.29.6.3.2p4"><small>4</small></a>
23202 The mbrtowc function returns the first of the following that applies (given the current
23204 0 if the next n or fewer bytes complete the multibyte character that
23206 corresponds to the null wide character (which is the value stored).
23208 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
23210 character (which is the value stored); the value returned is the number
23211 of bytes that complete the multibyte character.
23213 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
23215 multibyte character, and all n bytes have been processed (no value is
23216 stored).<sup><a href="#note349"><b>349)</b></a></sup>
23218 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
23220 do not contribute to a complete and valid multibyte character (no
23221 value is stored); the value of the macro EILSEQ is stored in errno,
23222 and the conversion state is unspecified.
23227 <p><b>Footnotes</b>
23228 <p><small><a name="note349" href="#note349">349)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
23229 sequence of redundant shift sequences (for implementations with state-dependent encodings).
23232 <p><small><a href="#Contents">Contents</a></small>
23233 <h5><a name="7.29.6.3.3" href="#7.29.6.3.3">7.29.6.3.3 The wcrtomb function</a></h5>
23235 <p><a name="7.29.6.3.3p1" href="#7.29.6.3.3p1"><small>1</small></a>
23237 #include <a href="#7.29"><wchar.h></a>
23238 size_t wcrtomb(char * restrict s,
23240 mbstate_t * restrict ps);
23242 <p><b>Description</b>
23243 <p><a name="7.29.6.3.3p2" href="#7.29.6.3.3p2"><small>2</small></a>
23244 If s is a null pointer, the wcrtomb function is equivalent to the call
23246 wcrtomb(buf, L'\0', ps)
23248 where buf is an internal buffer.
23249 <p><a name="7.29.6.3.3p3" href="#7.29.6.3.3p3"><small>3</small></a>
23250 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
23251 to represent the multibyte character that corresponds to the wide character given by wc
23252 (including any shift sequences), and stores the multibyte character representation in the
23253 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
23254 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
23255 to restore the initial shift state; the resulting state described is the initial conversion state.
23257 <p><a name="7.29.6.3.3p4" href="#7.29.6.3.3p4"><small>4</small></a>
23258 The wcrtomb function returns the number of bytes stored in the array object (including
23259 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
23260 the function stores the value of the macro EILSEQ in errno and returns
23261 (size_t)(-1); the conversion state is unspecified.
23263 <p><small><a href="#Contents">Contents</a></small>
23264 <h5><a name="7.29.6.4" href="#7.29.6.4">7.29.6.4 Restartable multibyte/wide string conversion functions</a></h5>
23265 <p><a name="7.29.6.4p1" href="#7.29.6.4p1"><small>1</small></a>
23266 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
23267 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
23268 mbstate_t that points to an object that can completely describe the current conversion
23269 state of the associated multibyte character sequence. If ps is a null pointer, each function
23270 uses its own internal mbstate_t object instead, which is initialized at program startup
23271 to the initial conversion state; the functions are not required to avoid data races with other
23272 calls to the same function in this case. The implementation behaves as if no library
23273 function calls these functions with a null pointer for ps.
23274 <p><a name="7.29.6.4p2" href="#7.29.6.4p2"><small>2</small></a>
23275 Also unlike their corresponding functions, the conversion source parameter, src, has a
23276 pointer-to-pointer type. When the function is storing the results of conversions (that is,
23277 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
23278 to reflect the amount of the source processed by that invocation.
23281 <p><small><a href="#Contents">Contents</a></small>
23282 <h5><a name="7.29.6.4.1" href="#7.29.6.4.1">7.29.6.4.1 The mbsrtowcs function</a></h5>
23284 <p><a name="7.29.6.4.1p1" href="#7.29.6.4.1p1"><small>1</small></a>
23286 #include <a href="#7.29"><wchar.h></a>
23287 size_t mbsrtowcs(wchar_t * restrict dst,
23288 const char ** restrict src,
23290 mbstate_t * restrict ps);
23292 <p><b>Description</b>
23293 <p><a name="7.29.6.4.1p2" href="#7.29.6.4.1p2"><small>2</small></a>
23294 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
23295 conversion state described by the object pointed to by ps, from the array indirectly
23296 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
23297 pointer, the converted characters are stored into the array pointed to by dst. Conversion
23298 continues up to and including a terminating null character, which is also stored.
23299 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
23300 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
23301 characters have been stored into the array pointed to by dst.<sup><a href="#note350"><b>350)</b></a></sup> Each conversion takes
23302 place as if by a call to the mbrtowc function.
23303 <p><a name="7.29.6.4.1p3" href="#7.29.6.4.1p3"><small>3</small></a>
23304 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
23305 pointer (if conversion stopped due to reaching a terminating null character) or the address
23306 just past the last multibyte character converted (if any). If conversion stopped due to
23307 reaching a terminating null character and if dst is not a null pointer, the resulting state
23308 described is the initial conversion state.
23310 <p><a name="7.29.6.4.1p4" href="#7.29.6.4.1p4"><small>4</small></a>
23311 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
23312 character, an encoding error occurs: the mbsrtowcs function stores the value of the
23313 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
23314 unspecified. Otherwise, it returns the number of multibyte characters successfully
23315 converted, not including the terminating null character (if any).
23322 <p><b>Footnotes</b>
23323 <p><small><a name="note350" href="#note350">350)</a> Thus, the value of len is ignored if dst is a null pointer.
23326 <p><small><a href="#Contents">Contents</a></small>
23327 <h5><a name="7.29.6.4.2" href="#7.29.6.4.2">7.29.6.4.2 The wcsrtombs function</a></h5>
23329 <p><a name="7.29.6.4.2p1" href="#7.29.6.4.2p1"><small>1</small></a>
23331 #include <a href="#7.29"><wchar.h></a>
23332 size_t wcsrtombs(char * restrict dst,
23333 const wchar_t ** restrict src,
23335 mbstate_t * restrict ps);
23337 <p><b>Description</b>
23338 <p><a name="7.29.6.4.2p2" href="#7.29.6.4.2p2"><small>2</small></a>
23339 The wcsrtombs function converts a sequence of wide characters from the array
23340 indirectly pointed to by src into a sequence of corresponding multibyte characters that
23341 begins in the conversion state described by the object pointed to by ps. If dst is not a
23342 null pointer, the converted characters are then stored into the array pointed to by dst.
23343 Conversion continues up to and including a terminating null wide character, which is also
23344 stored. Conversion stops earlier in two cases: when a wide character is reached that does
23345 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
23346 next multibyte character would exceed the limit of len total bytes to be stored into the
23347 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
23348 function.<sup><a href="#note351"><b>351)</b></a></sup>
23349 <p><a name="7.29.6.4.2p3" href="#7.29.6.4.2p3"><small>3</small></a>
23350 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
23351 pointer (if conversion stopped due to reaching a terminating null wide character) or the
23352 address just past the last wide character converted (if any). If conversion stopped due to
23353 reaching a terminating null wide character, the resulting state described is the initial
23356 <p><a name="7.29.6.4.2p4" href="#7.29.6.4.2p4"><small>4</small></a>
23357 If conversion stops because a wide character is reached that does not correspond to a
23358 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
23359 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
23360 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
23361 character sequence, not including the terminating null character (if any).
23368 <p><b>Footnotes</b>
23369 <p><small><a name="note351" href="#note351">351)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
23370 include those necessary to reach the initial shift state immediately before the null byte.
23373 <p><small><a href="#Contents">Contents</a></small>
23374 <h3><a name="7.30" href="#7.30">7.30 Wide character classification and mapping utilities <wctype.h></a></h3>
23376 <p><small><a href="#Contents">Contents</a></small>
23377 <h4><a name="7.30.1" href="#7.30.1">7.30.1 Introduction</a></h4>
23378 <p><a name="7.30.1p1" href="#7.30.1p1"><small>1</small></a>
23379 The header <a href="#7.30"><wctype.h></a> defines one macro, and declares three data types and many
23380 functions.<sup><a href="#note352"><b>352)</b></a></sup>
23381 <p><a name="7.30.1p2" href="#7.30.1p2"><small>2</small></a>
23382 The types declared are
23386 described in <a href="#7.29.1">7.29.1</a>;
23390 which is a scalar type that can hold values which represent locale-specific character
23395 which is a scalar type that can hold values which represent locale-specific character
23397 <p><a name="7.30.1p3" href="#7.30.1p3"><small>3</small></a>
23398 The macro defined is WEOF (described in <a href="#7.29.1">7.29.1</a>).
23399 <p><a name="7.30.1p4" href="#7.30.1p4"><small>4</small></a>
23400 The functions declared are grouped as follows:
23402 <li> Functions that provide wide character classification;
23403 <li> Extensible functions that provide wide character classification;
23404 <li> Functions that provide wide character case mapping;
23405 <li> Extensible functions that provide wide character mapping.
23407 <p><a name="7.30.1p5" href="#7.30.1p5"><small>5</small></a>
23408 For all functions described in this subclause that accept an argument of type wint_t, the
23409 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
23410 this argument has any other value, the behavior is undefined.
23411 <p><a name="7.30.1p6" href="#7.30.1p6"><small>6</small></a>
23412 The behavior of these functions is affected by the LC_CTYPE category of the current
23420 <p><b>Footnotes</b>
23421 <p><small><a name="note352" href="#note352">352)</a> See ''future library directions'' (<a href="#7.31.17">7.31.17</a>).
23424 <p><small><a href="#Contents">Contents</a></small>
23425 <h4><a name="7.30.2" href="#7.30.2">7.30.2 Wide character classification utilities</a></h4>
23426 <p><a name="7.30.2p1" href="#7.30.2p1"><small>1</small></a>
23427 The header <a href="#7.30"><wctype.h></a> declares several functions useful for classifying wide
23429 <p><a name="7.30.2p2" href="#7.30.2p2"><small>2</small></a>
23430 The term printing wide character refers to a member of a locale-specific set of wide
23431 characters, each of which occupies at least one printing position on a display device. The
23432 term control wide character refers to a member of a locale-specific set of wide characters
23433 that are not printing wide characters.
23435 <p><small><a href="#Contents">Contents</a></small>
23436 <h5><a name="7.30.2.1" href="#7.30.2.1">7.30.2.1 Wide character classification functions</a></h5>
23437 <p><a name="7.30.2.1p1" href="#7.30.2.1p1"><small>1</small></a>
23438 The functions in this subclause return nonzero (true) if and only if the value of the
23439 argument wc conforms to that in the description of the function.
23440 <p><a name="7.30.2.1p2" href="#7.30.2.1p2"><small>2</small></a>
23441 Each of the following functions returns true for each wide character that corresponds (as
23442 if by a call to the wctob function) to a single-byte character for which the corresponding
23443 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
23444 iswpunct functions may differ with respect to wide characters other than L' ' that are
23445 both printing and white-space wide characters.<sup><a href="#note353"><b>353)</b></a></sup>
23446 <p><b> Forward references</b>: the wctob function (<a href="#7.29.6.1.2">7.29.6.1.2</a>).
23448 <p><b>Footnotes</b>
23449 <p><small><a name="note353" href="#note353">353)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
23450 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
23451 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
23452 && iswspace(wc) is true, but not both.
23455 <p><small><a href="#Contents">Contents</a></small>
23456 <h5><a name="7.30.2.1.1" href="#7.30.2.1.1">7.30.2.1.1 The iswalnum function</a></h5>
23458 <p><a name="7.30.2.1.1p1" href="#7.30.2.1.1p1"><small>1</small></a>
23460 #include <a href="#7.30"><wctype.h></a>
23461 int iswalnum(wint_t wc);
23463 <p><b>Description</b>
23464 <p><a name="7.30.2.1.1p2" href="#7.30.2.1.1p2"><small>2</small></a>
23465 The iswalnum function tests for any wide character for which iswalpha or
23468 <p><small><a href="#Contents">Contents</a></small>
23469 <h5><a name="7.30.2.1.2" href="#7.30.2.1.2">7.30.2.1.2 The iswalpha function</a></h5>
23471 <p><a name="7.30.2.1.2p1" href="#7.30.2.1.2p1"><small>1</small></a>
23473 #include <a href="#7.30"><wctype.h></a>
23474 int iswalpha(wint_t wc);
23476 <p><b>Description</b>
23477 <p><a name="7.30.2.1.2p2" href="#7.30.2.1.2p2"><small>2</small></a>
23478 The iswalpha function tests for any wide character for which iswupper or
23479 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
23482 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
23483 is true.<sup><a href="#note354"><b>354)</b></a></sup>
23485 <p><b>Footnotes</b>
23486 <p><small><a name="note354" href="#note354">354)</a> The functions iswlower and iswupper test true or false separately for each of these additional
23487 wide characters; all four combinations are possible.
23490 <p><small><a href="#Contents">Contents</a></small>
23491 <h5><a name="7.30.2.1.3" href="#7.30.2.1.3">7.30.2.1.3 The iswblank function</a></h5>
23493 <p><a name="7.30.2.1.3p1" href="#7.30.2.1.3p1"><small>1</small></a>
23495 #include <a href="#7.30"><wctype.h></a>
23496 int iswblank(wint_t wc);
23498 <p><b>Description</b>
23499 <p><a name="7.30.2.1.3p2" href="#7.30.2.1.3p2"><small>2</small></a>
23500 The iswblank function tests for any wide character that is a standard blank wide
23501 character or is one of a locale-specific set of wide characters for which iswspace is true
23502 and that is used to separate words within a line of text. The standard blank wide
23503 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
23504 locale, iswblank returns true only for the standard blank characters.
23506 <p><small><a href="#Contents">Contents</a></small>
23507 <h5><a name="7.30.2.1.4" href="#7.30.2.1.4">7.30.2.1.4 The iswcntrl function</a></h5>
23509 <p><a name="7.30.2.1.4p1" href="#7.30.2.1.4p1"><small>1</small></a>
23511 #include <a href="#7.30"><wctype.h></a>
23512 int iswcntrl(wint_t wc);
23514 <p><b>Description</b>
23515 <p><a name="7.30.2.1.4p2" href="#7.30.2.1.4p2"><small>2</small></a>
23516 The iswcntrl function tests for any control wide character.
23518 <p><small><a href="#Contents">Contents</a></small>
23519 <h5><a name="7.30.2.1.5" href="#7.30.2.1.5">7.30.2.1.5 The iswdigit function</a></h5>
23521 <p><a name="7.30.2.1.5p1" href="#7.30.2.1.5p1"><small>1</small></a>
23523 #include <a href="#7.30"><wctype.h></a>
23524 int iswdigit(wint_t wc);
23526 <p><b>Description</b>
23527 <p><a name="7.30.2.1.5p2" href="#7.30.2.1.5p2"><small>2</small></a>
23528 The iswdigit function tests for any wide character that corresponds to a decimal-digit
23529 character (as defined in <a href="#5.2.1">5.2.1</a>).
23531 <p><small><a href="#Contents">Contents</a></small>
23532 <h5><a name="7.30.2.1.6" href="#7.30.2.1.6">7.30.2.1.6 The iswgraph function</a></h5>
23534 <p><a name="7.30.2.1.6p1" href="#7.30.2.1.6p1"><small>1</small></a>
23536 #include <a href="#7.30"><wctype.h></a>
23537 int iswgraph(wint_t wc);
23544 <p><b>Description</b>
23545 <p><a name="7.30.2.1.6p2" href="#7.30.2.1.6p2"><small>2</small></a>
23546 The iswgraph function tests for any wide character for which iswprint is true and
23547 iswspace is false.<sup><a href="#note355"><b>355)</b></a></sup>
23549 <p><b>Footnotes</b>
23550 <p><small><a name="note355" href="#note355">355)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
23551 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
23552 characters other than ' '.
23555 <p><small><a href="#Contents">Contents</a></small>
23556 <h5><a name="7.30.2.1.7" href="#7.30.2.1.7">7.30.2.1.7 The iswlower function</a></h5>
23558 <p><a name="7.30.2.1.7p1" href="#7.30.2.1.7p1"><small>1</small></a>
23560 #include <a href="#7.30"><wctype.h></a>
23561 int iswlower(wint_t wc);
23563 <p><b>Description</b>
23564 <p><a name="7.30.2.1.7p2" href="#7.30.2.1.7p2"><small>2</small></a>
23565 The iswlower function tests for any wide character that corresponds to a lowercase
23566 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
23567 iswdigit, iswpunct, or iswspace is true.
23569 <p><small><a href="#Contents">Contents</a></small>
23570 <h5><a name="7.30.2.1.8" href="#7.30.2.1.8">7.30.2.1.8 The iswprint function</a></h5>
23572 <p><a name="7.30.2.1.8p1" href="#7.30.2.1.8p1"><small>1</small></a>
23574 #include <a href="#7.30"><wctype.h></a>
23575 int iswprint(wint_t wc);
23577 <p><b>Description</b>
23578 <p><a name="7.30.2.1.8p2" href="#7.30.2.1.8p2"><small>2</small></a>
23579 The iswprint function tests for any printing wide character.
23581 <p><small><a href="#Contents">Contents</a></small>
23582 <h5><a name="7.30.2.1.9" href="#7.30.2.1.9">7.30.2.1.9 The iswpunct function</a></h5>
23584 <p><a name="7.30.2.1.9p1" href="#7.30.2.1.9p1"><small>1</small></a>
23586 #include <a href="#7.30"><wctype.h></a>
23587 int iswpunct(wint_t wc);
23589 <p><b>Description</b>
23590 <p><a name="7.30.2.1.9p2" href="#7.30.2.1.9p2"><small>2</small></a>
23591 The iswpunct function tests for any printing wide character that is one of a locale-
23592 specific set of punctuation wide characters for which neither iswspace nor iswalnum
23593 is true.<sup><a href="#note355"><b>355)</b></a></sup>
23595 <p><small><a href="#Contents">Contents</a></small>
23596 <h5><a name="7.30.2.1.10" href="#7.30.2.1.10">7.30.2.1.10 The iswspace function</a></h5>
23598 <p><a name="7.30.2.1.10p1" href="#7.30.2.1.10p1"><small>1</small></a>
23600 #include <a href="#7.30"><wctype.h></a>
23601 int iswspace(wint_t wc);
23607 <p><b>Description</b>
23608 <p><a name="7.30.2.1.10p2" href="#7.30.2.1.10p2"><small>2</small></a>
23609 The iswspace function tests for any wide character that corresponds to a locale-specific
23610 set of white-space wide characters for which none of iswalnum, iswgraph, or
23613 <p><small><a href="#Contents">Contents</a></small>
23614 <h5><a name="7.30.2.1.11" href="#7.30.2.1.11">7.30.2.1.11 The iswupper function</a></h5>
23616 <p><a name="7.30.2.1.11p1" href="#7.30.2.1.11p1"><small>1</small></a>
23618 #include <a href="#7.30"><wctype.h></a>
23619 int iswupper(wint_t wc);
23621 <p><b>Description</b>
23622 <p><a name="7.30.2.1.11p2" href="#7.30.2.1.11p2"><small>2</small></a>
23623 The iswupper function tests for any wide character that corresponds to an uppercase
23624 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
23625 iswdigit, iswpunct, or iswspace is true.
23627 <p><small><a href="#Contents">Contents</a></small>
23628 <h5><a name="7.30.2.1.12" href="#7.30.2.1.12">7.30.2.1.12 The iswxdigit function</a></h5>
23630 <p><a name="7.30.2.1.12p1" href="#7.30.2.1.12p1"><small>1</small></a>
23632 #include <a href="#7.30"><wctype.h></a>
23633 int iswxdigit(wint_t wc);
23635 <p><b>Description</b>
23636 <p><a name="7.30.2.1.12p2" href="#7.30.2.1.12p2"><small>2</small></a>
23637 The iswxdigit function tests for any wide character that corresponds to a
23638 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
23640 <p><small><a href="#Contents">Contents</a></small>
23641 <h5><a name="7.30.2.2" href="#7.30.2.2">7.30.2.2 Extensible wide character classification functions</a></h5>
23642 <p><a name="7.30.2.2p1" href="#7.30.2.2p1"><small>1</small></a>
23643 The functions wctype and iswctype provide extensible wide character classification
23644 as well as testing equivalent to that performed by the functions described in the previous
23645 subclause (<a href="#7.30.2.1">7.30.2.1</a>).
23647 <p><small><a href="#Contents">Contents</a></small>
23648 <h5><a name="7.30.2.2.1" href="#7.30.2.2.1">7.30.2.2.1 The iswctype function</a></h5>
23650 <p><a name="7.30.2.2.1p1" href="#7.30.2.2.1p1"><small>1</small></a>
23652 #include <a href="#7.30"><wctype.h></a>
23653 int iswctype(wint_t wc, wctype_t desc);
23655 <p><b>Description</b>
23656 <p><a name="7.30.2.2.1p2" href="#7.30.2.2.1p2"><small>2</small></a>
23657 The iswctype function determines whether the wide character wc has the property
23658 described by desc. The current setting of the LC_CTYPE category shall be the same as
23659 during the call to wctype that returned the value desc.
23660 <p><a name="7.30.2.2.1p3" href="#7.30.2.2.1p3"><small>3</small></a>
23661 Each of the following expressions has a truth-value equivalent to the call to the wide
23662 character classification function (<a href="#7.30.2.1">7.30.2.1</a>) in the comment that follows the expression:
23665 iswctype(wc, wctype("alnum")) // iswalnum(wc)
23666 iswctype(wc, wctype("alpha")) // iswalpha(wc)
23667 iswctype(wc, wctype("blank")) // iswblank(wc)
23668 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
23669 iswctype(wc, wctype("digit")) // iswdigit(wc)
23670 iswctype(wc, wctype("graph")) // iswgraph(wc)
23671 iswctype(wc, wctype("lower")) // iswlower(wc)
23672 iswctype(wc, wctype("print")) // iswprint(wc)
23673 iswctype(wc, wctype("punct")) // iswpunct(wc)
23674 iswctype(wc, wctype("space")) // iswspace(wc)
23675 iswctype(wc, wctype("upper")) // iswupper(wc)
23676 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
23679 <p><a name="7.30.2.2.1p4" href="#7.30.2.2.1p4"><small>4</small></a>
23680 The iswctype function returns nonzero (true) if and only if the value of the wide
23681 character wc has the property described by desc. If desc is zero, the iswctype
23682 function returns zero (false).
23683 <p><b> Forward references</b>: the wctype function (<a href="#7.30.2.2.2">7.30.2.2.2</a>).
23685 <p><small><a href="#Contents">Contents</a></small>
23686 <h5><a name="7.30.2.2.2" href="#7.30.2.2.2">7.30.2.2.2 The wctype function</a></h5>
23688 <p><a name="7.30.2.2.2p1" href="#7.30.2.2.2p1"><small>1</small></a>
23690 #include <a href="#7.30"><wctype.h></a>
23691 wctype_t wctype(const char *property);
23693 <p><b>Description</b>
23694 <p><a name="7.30.2.2.2p2" href="#7.30.2.2.2p2"><small>2</small></a>
23695 The wctype function constructs a value with type wctype_t that describes a class of
23696 wide characters identified by the string argument property.
23697 <p><a name="7.30.2.2.2p3" href="#7.30.2.2.2p3"><small>3</small></a>
23698 The strings listed in the description of the iswctype function shall be valid in all
23699 locales as property arguments to the wctype function.
23701 <p><a name="7.30.2.2.2p4" href="#7.30.2.2.2p4"><small>4</small></a>
23702 If property identifies a valid class of wide characters according to the LC_CTYPE
23703 category of the current locale, the wctype function returns a nonzero value that is valid
23704 as the second argument to the iswctype function; otherwise, it returns zero.
23707 <p><small><a href="#Contents">Contents</a></small>
23708 <h4><a name="7.30.3" href="#7.30.3">7.30.3 Wide character case mapping utilities</a></h4>
23709 <p><a name="7.30.3p1" href="#7.30.3p1"><small>1</small></a>
23710 The header <a href="#7.30"><wctype.h></a> declares several functions useful for mapping wide characters.
23712 <p><small><a href="#Contents">Contents</a></small>
23713 <h5><a name="7.30.3.1" href="#7.30.3.1">7.30.3.1 Wide character case mapping functions</a></h5>
23715 <p><small><a href="#Contents">Contents</a></small>
23716 <h5><a name="7.30.3.1.1" href="#7.30.3.1.1">7.30.3.1.1 The towlower function</a></h5>
23718 <p><a name="7.30.3.1.1p1" href="#7.30.3.1.1p1"><small>1</small></a>
23720 #include <a href="#7.30"><wctype.h></a>
23721 wint_t towlower(wint_t wc);
23723 <p><b>Description</b>
23724 <p><a name="7.30.3.1.1p2" href="#7.30.3.1.1p2"><small>2</small></a>
23725 The towlower function converts an uppercase letter to a corresponding lowercase letter.
23727 <p><a name="7.30.3.1.1p3" href="#7.30.3.1.1p3"><small>3</small></a>
23728 If the argument is a wide character for which iswupper is true and there are one or
23729 more corresponding wide characters, as specified by the current locale, for which
23730 iswlower is true, the towlower function returns one of the corresponding wide
23731 characters (always the same one for any given locale); otherwise, the argument is
23732 returned unchanged.
23734 <p><small><a href="#Contents">Contents</a></small>
23735 <h5><a name="7.30.3.1.2" href="#7.30.3.1.2">7.30.3.1.2 The towupper function</a></h5>
23737 <p><a name="7.30.3.1.2p1" href="#7.30.3.1.2p1"><small>1</small></a>
23739 #include <a href="#7.30"><wctype.h></a>
23740 wint_t towupper(wint_t wc);
23742 <p><b>Description</b>
23743 <p><a name="7.30.3.1.2p2" href="#7.30.3.1.2p2"><small>2</small></a>
23744 The towupper function converts a lowercase letter to a corresponding uppercase letter.
23746 <p><a name="7.30.3.1.2p3" href="#7.30.3.1.2p3"><small>3</small></a>
23747 If the argument is a wide character for which iswlower is true and there are one or
23748 more corresponding wide characters, as specified by the current locale, for which
23749 iswupper is true, the towupper function returns one of the corresponding wide
23750 characters (always the same one for any given locale); otherwise, the argument is
23751 returned unchanged.
23753 <p><small><a href="#Contents">Contents</a></small>
23754 <h5><a name="7.30.3.2" href="#7.30.3.2">7.30.3.2 Extensible wide character case mapping functions</a></h5>
23755 <p><a name="7.30.3.2p1" href="#7.30.3.2p1"><small>1</small></a>
23756 The functions wctrans and towctrans provide extensible wide character mapping as
23757 well as case mapping equivalent to that performed by the functions described in the
23758 previous subclause (<a href="#7.30.3.1">7.30.3.1</a>).
23761 <p><small><a href="#Contents">Contents</a></small>
23762 <h5><a name="7.30.3.2.1" href="#7.30.3.2.1">7.30.3.2.1 The towctrans function</a></h5>
23764 <p><a name="7.30.3.2.1p1" href="#7.30.3.2.1p1"><small>1</small></a>
23766 #include <a href="#7.30"><wctype.h></a>
23767 wint_t towctrans(wint_t wc, wctrans_t desc);
23769 <p><b>Description</b>
23770 <p><a name="7.30.3.2.1p2" href="#7.30.3.2.1p2"><small>2</small></a>
23771 The towctrans function maps the wide character wc using the mapping described by
23772 desc. The current setting of the LC_CTYPE category shall be the same as during the call
23773 to wctrans that returned the value desc.
23774 <p><a name="7.30.3.2.1p3" href="#7.30.3.2.1p3"><small>3</small></a>
23775 Each of the following expressions behaves the same as the call to the wide character case
23776 mapping function (<a href="#7.30.3.1">7.30.3.1</a>) in the comment that follows the expression:
23778 towctrans(wc, wctrans("tolower")) // towlower(wc)
23779 towctrans(wc, wctrans("toupper")) // towupper(wc)
23782 <p><a name="7.30.3.2.1p4" href="#7.30.3.2.1p4"><small>4</small></a>
23783 The towctrans function returns the mapped value of wc using the mapping described
23784 by desc. If desc is zero, the towctrans function returns the value of wc.
23786 <p><small><a href="#Contents">Contents</a></small>
23787 <h5><a name="7.30.3.2.2" href="#7.30.3.2.2">7.30.3.2.2 The wctrans function</a></h5>
23789 <p><a name="7.30.3.2.2p1" href="#7.30.3.2.2p1"><small>1</small></a>
23791 #include <a href="#7.30"><wctype.h></a>
23792 wctrans_t wctrans(const char *property);
23794 <p><b>Description</b>
23795 <p><a name="7.30.3.2.2p2" href="#7.30.3.2.2p2"><small>2</small></a>
23796 The wctrans function constructs a value with type wctrans_t that describes a
23797 mapping between wide characters identified by the string argument property.
23798 <p><a name="7.30.3.2.2p3" href="#7.30.3.2.2p3"><small>3</small></a>
23799 The strings listed in the description of the towctrans function shall be valid in all
23800 locales as property arguments to the wctrans function.
23802 <p><a name="7.30.3.2.2p4" href="#7.30.3.2.2p4"><small>4</small></a>
23803 If property identifies a valid mapping of wide characters according to the LC_CTYPE
23804 category of the current locale, the wctrans function returns a nonzero value that is valid
23805 as the second argument to the towctrans function; otherwise, it returns zero.
23808 <p><small><a href="#Contents">Contents</a></small>
23809 <h3><a name="7.31" href="#7.31">7.31 Future library directions</a></h3>
23810 <p><a name="7.31p1" href="#7.31p1"><small>1</small></a>
23811 The following names are grouped under individual headers for convenience. All external
23812 names described below are reserved no matter what headers are included by the program.
23814 <p><small><a href="#Contents">Contents</a></small>
23815 <h4><a name="7.31.1" href="#7.31.1">7.31.1 Complex arithmetic <complex.h></a></h4>
23816 <p><a name="7.31.1p1" href="#7.31.1p1"><small>1</small></a>
23820 cerfc clog10 clgamma
23821 cexp2 clog1p ctgamma
23823 and the same names suffixed with f or l may be added to the declarations in the
23824 <a href="#7.3"><complex.h></a> header.
23826 <p><small><a href="#Contents">Contents</a></small>
23827 <h4><a name="7.31.2" href="#7.31.2">7.31.2 Character handling <ctype.h></a></h4>
23828 <p><a name="7.31.2p1" href="#7.31.2p1"><small>1</small></a>
23829 Function names that begin with either is or to, and a lowercase letter may be added to
23830 the declarations in the <a href="#7.4"><ctype.h></a> header.
23832 <p><small><a href="#Contents">Contents</a></small>
23833 <h4><a name="7.31.3" href="#7.31.3">7.31.3 Errors <errno.h></a></h4>
23834 <p><a name="7.31.3p1" href="#7.31.3p1"><small>1</small></a>
23835 Macros that begin with E and a digit or E and an uppercase letter may be added to the
23836 macros defined in the <a href="#7.5"><errno.h></a> header.
23838 <p><small><a href="#Contents">Contents</a></small>
23839 <h4><a name="7.31.4" href="#7.31.4">7.31.4 Floating-point environment <fenv.h></a></h4>
23840 <p><a name="7.31.4p1" href="#7.31.4p1"><small>1</small></a>
23841 Macros that begin with FE_ and an uppercase letter may be added to the macros defined
23842 in the <a href="#7.6"><fenv.h></a> header.
23844 <p><small><a href="#Contents">Contents</a></small>
23845 <h4><a name="7.31.5" href="#7.31.5">7.31.5 Format conversion of integer types <inttypes.h></a></h4>
23846 <p><a name="7.31.5p1" href="#7.31.5p1"><small>1</small></a>
23847 Macros that begin with either PRI or SCN, and either a lowercase letter or X may be
23848 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
23850 <p><small><a href="#Contents">Contents</a></small>
23851 <h4><a name="7.31.6" href="#7.31.6">7.31.6 Localization <locale.h></a></h4>
23852 <p><a name="7.31.6p1" href="#7.31.6p1"><small>1</small></a>
23853 Macros that begin with LC_ and an uppercase letter may be added to the macros defined
23854 in the <a href="#7.11"><locale.h></a> header.
23856 <p><small><a href="#Contents">Contents</a></small>
23857 <h4><a name="7.31.7" href="#7.31.7">7.31.7 Signal handling <signal.h></a></h4>
23858 <p><a name="7.31.7p1" href="#7.31.7p1"><small>1</small></a>
23859 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
23860 letter may be added to the macros defined in the <a href="#7.14"><signal.h></a> header.
23862 <p><small><a href="#Contents">Contents</a></small>
23863 <h4><a name="7.31.8" href="#7.31.8">7.31.8 Atomics <stdatomic.h></a></h4>
23864 <p><a name="7.31.8p1" href="#7.31.8p1"><small>1</small></a>
23865 Macros that begin with ATOMIC_ and an uppercase letter may be added to the macros
23866 defined in the <a href="#7.17"><stdatomic.h></a> header. Typedef names that begin with either
23867 atomic_ or memory_, and a lowercase letter may be added to the declarations in the
23868 <a href="#7.17"><stdatomic.h></a> header. Enumeration constants that begin with memory_order_
23870 and a lowercase letter may be added to the definition of the memory_order type in the
23871 <a href="#7.17"><stdatomic.h></a> header. Function names that begin with atomic_ and a lowercase
23872 letter may be added to the declarations in the <a href="#7.17"><stdatomic.h></a> header.
23874 <p><small><a href="#Contents">Contents</a></small>
23875 <h4><a name="7.31.9" href="#7.31.9">7.31.9 Boolean type and values <stdbool.h></a></h4>
23876 <p><a name="7.31.9p1" href="#7.31.9p1"><small>1</small></a>
23877 The ability to undefine and perhaps then redefine the macros bool, true, and false is
23878 an obsolescent feature.
23880 <p><small><a href="#Contents">Contents</a></small>
23881 <h4><a name="7.31.10" href="#7.31.10">7.31.10 Integer types <stdint.h></a></h4>
23882 <p><a name="7.31.10p1" href="#7.31.10p1"><small>1</small></a>
23883 Typedef names beginning with int or uint and ending with _t may be added to the
23884 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
23885 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
23886 <a href="#7.20"><stdint.h></a> header.
23888 <p><small><a href="#Contents">Contents</a></small>
23889 <h4><a name="7.31.11" href="#7.31.11">7.31.11 Input/output <stdio.h></a></h4>
23890 <p><a name="7.31.11p1" href="#7.31.11p1"><small>1</small></a>
23891 Lowercase letters may be added to the conversion specifiers and length modifiers in
23892 fprintf and fscanf. Other characters may be used in extensions.
23893 <p><a name="7.31.11p2" href="#7.31.11p2"><small>2</small></a>
23894 The use of ungetc on a binary stream where the file position indicator is zero prior to
23895 the call is an obsolescent feature.
23897 <p><small><a href="#Contents">Contents</a></small>
23898 <h4><a name="7.31.12" href="#7.31.12">7.31.12 General utilities <stdlib.h></a></h4>
23899 <p><a name="7.31.12p1" href="#7.31.12p1"><small>1</small></a>
23900 Function names that begin with str and a lowercase letter may be added to the
23901 declarations in the <a href="#7.22"><stdlib.h></a> header.
23903 <p><small><a href="#Contents">Contents</a></small>
23904 <h4><a name="7.31.13" href="#7.31.13">7.31.13 String handling <string.h></a></h4>
23905 <p><a name="7.31.13p1" href="#7.31.13p1"><small>1</small></a>
23906 Function names that begin with str, mem, or wcs and a lowercase letter may be added
23907 to the declarations in the <a href="#7.24"><string.h></a> header.
23909 <p><small><a href="#Contents">Contents</a></small>
23910 <h4><a name="7.31.14" href="#7.31.14">7.31.14 Date and time <time.h></a></h4>
23911 Macros beginning with TIME_ and an uppercase letter may be added to the macros in the
23912 <a href="#7.27"><time.h></a> header.
23914 <p><small><a href="#Contents">Contents</a></small>
23915 <h4><a name="7.31.15" href="#7.31.15">7.31.15 Threads <threads.h></a></h4>
23916 <p><a name="7.31.15p1" href="#7.31.15p1"><small>1</small></a>
23917 Function names, type names, and enumeration constants that begin with either cnd_,
23918 mtx_, thrd_, or tss_, and a lowercase letter may be added to the declarations in the
23919 <a href="#7.26"><threads.h></a> header.
23921 <p><small><a href="#Contents">Contents</a></small>
23922 <h4><a name="7.31.16" href="#7.31.16">7.31.16 Extended multibyte and wide character utilities <wchar.h></a></h4>
23923 <p><a name="7.31.16p1" href="#7.31.16p1"><small>1</small></a>
23924 Function names that begin with wcs and a lowercase letter may be added to the
23925 declarations in the <a href="#7.29"><wchar.h></a> header.
23926 <p><a name="7.31.16p2" href="#7.31.16p2"><small>2</small></a>
23927 Lowercase letters may be added to the conversion specifiers and length modifiers in
23928 fwprintf and fwscanf. Other characters may be used in extensions.
23931 <p><small><a href="#Contents">Contents</a></small>
23932 <h4><a name="7.31.17" href="#7.31.17">7.31.17 Wide character classification and mapping utilities</a></h4>
23933 <a href="#7.30"><wctype.h></a>
23934 <p><a name="7.31.17p1" href="#7.31.17p1"><small>1</small></a>
23935 Function names that begin with is or to and a lowercase letter may be added to the
23936 declarations in the <a href="#7.30"><wctype.h></a> header.
23939 <p><small><a href="#Contents">Contents</a></small>
23940 <h2><a name="A" href="#A">Annex A</a></h2>
23943 Language syntax summary
23945 <p><a name="Ap1" href="#Ap1"><small>1</small></a>
23946 NOTE The notation is described in <a href="#6.1">6.1</a>.
23949 <p><small><a href="#Contents">Contents</a></small>
23950 <h3><a name="A.1" href="#A.1">A.1 Lexical grammar</a></h3>
23952 <p><small><a href="#Contents">Contents</a></small>
23953 <h4><a name="A.1.1" href="#A.1.1">A.1.1 Lexical elements</a></h4>
23954 (<a href="#6.4">6.4</a>) token:
23962 (<a href="#6.4">6.4</a>) preprocessing-token:
23971 each non-white-space character that cannot be one of the above
23974 <p><small><a href="#Contents">Contents</a></small>
23975 <h4><a name="A.1.2" href="#A.1.2">A.1.2 Keywords</a></h4>
23976 (<a href="#6.4.1">6.4.1</a>) keyword: one of
23982 const register _Alignas
23983 continue restrict _Alignof
23984 default return _Atomic
23986 double signed _Complex
23987 else sizeof _Generic
23988 enum static _Imaginary
23989 extern struct _Noreturn
23990 float switch _Static_assert
23991 for typedef _Thread_local
23995 <p><small><a href="#Contents">Contents</a></small>
23996 <h4><a name="A.1.3" href="#A.1.3">A.1.3 Identifiers</a></h4>
23997 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
23999 identifier-nondigit
24000 identifier identifier-nondigit
24003 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
24006 universal-character-name
24007 other implementation-defined characters
24009 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
24011 _ a b c d e f g h i j k l m
24012 n o p q r s t u v w x y z
24013 A B C D E F G H I J K L M
24014 N O P Q R S T U V W X Y Z
24016 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
24019 0 1 2 3 4 5 6 7 8 9
24022 <p><small><a href="#Contents">Contents</a></small>
24023 <h4><a name="A.1.4" href="#A.1.4">A.1.4 Universal character names</a></h4>
24024 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
24027 \U hex-quad hex-quad
24029 (<a href="#6.4.3">6.4.3</a>) hex-quad:
24031 hexadecimal-digit hexadecimal-digit
24032 hexadecimal-digit hexadecimal-digit
24035 <p><small><a href="#Contents">Contents</a></small>
24036 <h4><a name="A.1.5" href="#A.1.5">A.1.5 Constants</a></h4>
24037 (<a href="#6.4.4">6.4.4</a>) constant:
24041 enumeration-constant
24044 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
24046 decimal-constant integer-suffix<sub>opt</sub>
24047 octal-constant integer-suffix<sub>opt</sub>
24048 hexadecimal-constant integer-suffix<sub>opt</sub>
24050 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
24053 decimal-constant digit
24055 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
24058 octal-constant octal-digit
24060 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
24062 hexadecimal-prefix hexadecimal-digit
24063 hexadecimal-constant hexadecimal-digit
24065 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
24069 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
24073 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
24078 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
24080 0 1 2 3 4 5 6 7 8 9
24084 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
24086 unsigned-suffix long-suffix<sub>opt</sub>
24087 unsigned-suffix long-long-suffix
24088 long-suffix unsigned-suffix<sub>opt</sub>
24089 long-long-suffix unsigned-suffix<sub>opt</sub>
24091 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
24095 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
24099 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
24103 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
24105 decimal-floating-constant
24106 hexadecimal-floating-constant
24108 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
24110 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
24111 digit-sequence exponent-part floating-suffix<sub>opt</sub>
24113 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
24115 hexadecimal-prefix hexadecimal-fractional-constant
24116 binary-exponent-part floating-suffix<sub>opt</sub>
24117 hexadecimal-prefix hexadecimal-digit-sequence
24118 binary-exponent-part floating-suffix<sub>opt</sub>
24120 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
24122 digit-sequence<sub>opt</sub> . digit-sequence
24125 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
24127 e sign<sub>opt</sub> digit-sequence
24128 E sign<sub>opt</sub> digit-sequence
24130 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
24135 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
24138 digit-sequence digit
24140 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
24142 hexadecimal-digit-sequence<sub>opt</sub> .
24143 hexadecimal-digit-sequence
24144 hexadecimal-digit-sequence .
24146 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
24148 p sign<sub>opt</sub> digit-sequence
24149 P sign<sub>opt</sub> digit-sequence
24151 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
24154 hexadecimal-digit-sequence hexadecimal-digit
24156 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
24160 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
24164 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
24166 ' c-char-sequence '
24167 L' c-char-sequence '
24168 u' c-char-sequence '
24169 U' c-char-sequence '
24171 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
24174 c-char-sequence c-char
24176 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
24178 any member of the source character set except
24179 the single-quote ', backslash \, or new-line character
24182 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
24185 simple-escape-sequence
24186 octal-escape-sequence
24187 hexadecimal-escape-sequence
24188 universal-character-name
24190 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
24193 \a \b \f \n \r \t \v
24195 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
24198 \ octal-digit octal-digit
24199 \ octal-digit octal-digit octal-digit
24201 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
24203 \x hexadecimal-digit
24204 hexadecimal-escape-sequence hexadecimal-digit
24207 <p><small><a href="#Contents">Contents</a></small>
24208 <h4><a name="A.1.6" href="#A.1.6">A.1.6 String literals</a></h4>
24209 (<a href="#6.4.5">6.4.5</a>) string-literal:
24211 encoding-prefix<sub>opt</sub> " s-char-sequence<sub>opt</sub> "
24213 (<a href="#6.4.5">6.4.5</a>) encoding-prefix:
24220 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
24223 s-char-sequence s-char
24225 (<a href="#6.4.5">6.4.5</a>) s-char:
24227 any member of the source character set except
24228 the double-quote ", backslash \, or new-line character
24232 <p><small><a href="#Contents">Contents</a></small>
24233 <h4><a name="A.1.7" href="#A.1.7">A.1.7 Punctuators</a></h4>
24234 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
24237 [ ] ( ) { } . ->
24238 ++ -- & * + - ~ !
24239 / % << >> < > <= >= == != ^ | && ||
24241 = *= /= %= += -= <<= >>= &= ^= |=
24243 <: :> <% %> %: %:%:
24246 <p><small><a href="#Contents">Contents</a></small>
24247 <h4><a name="A.1.8" href="#A.1.8">A.1.8 Header names</a></h4>
24248 (<a href="#6.4.7">6.4.7</a>) header-name:
24250 < h-char-sequence >
24251 " q-char-sequence "
24253 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
24256 h-char-sequence h-char
24258 (<a href="#6.4.7">6.4.7</a>) h-char:
24260 any member of the source character set except
24261 the new-line character and >
24263 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
24266 q-char-sequence q-char
24268 (<a href="#6.4.7">6.4.7</a>) q-char:
24270 any member of the source character set except
24271 the new-line character and "
24274 <p><small><a href="#Contents">Contents</a></small>
24275 <h4><a name="A.1.9" href="#A.1.9">A.1.9 Preprocessing numbers</a></h4>
24276 (<a href="#6.4.8">6.4.8</a>) pp-number:
24282 pp-number identifier-nondigit
24290 <p><small><a href="#Contents">Contents</a></small>
24291 <h3><a name="A.2" href="#A.2">A.2 Phrase structure grammar</a></h3>
24293 <p><small><a href="#Contents">Contents</a></small>
24294 <h4><a name="A.2.1" href="#A.2.1">A.2.1 Expressions</a></h4>
24295 (<a href="#6.5.1">6.5.1</a>) primary-expression:
24303 (<a href="#6.5.1.1">6.5.1.1</a>) generic-selection:
24305 _Generic ( assignment-expression , generic-assoc-list )
24307 (<a href="#6.5.1.1">6.5.1.1</a>) generic-assoc-list:
24309 generic-association
24310 generic-assoc-list , generic-association
24312 (<a href="#6.5.1.1">6.5.1.1</a>) generic-association:
24314 type-name : assignment-expression
24315 default : assignment-expression
24317 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
24320 postfix-expression [ expression ]
24321 postfix-expression ( argument-expression-list<sub>opt</sub> )
24322 postfix-expression . identifier
24323 postfix-expression -> identifier
24324 postfix-expression ++
24325 postfix-expression --
24326 ( type-name ) { initializer-list }
24327 ( type-name ) { initializer-list , }
24329 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
24331 assignment-expression
24332 argument-expression-list , assignment-expression
24334 (<a href="#6.5.3">6.5.3</a>) unary-expression:
24338 ++ unary-expression
24339 -- unary-expression
24340 unary-operator cast-expression
24341 sizeof unary-expression
24342 sizeof ( type-name )
24343 _Alignof ( type-name )
24345 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
24349 (<a href="#6.5.4">6.5.4</a>) cast-expression:
24352 ( type-name ) cast-expression
24354 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
24357 multiplicative-expression * cast-expression
24358 multiplicative-expression / cast-expression
24359 multiplicative-expression % cast-expression
24361 (<a href="#6.5.6">6.5.6</a>) additive-expression:
24363 multiplicative-expression
24364 additive-expression + multiplicative-expression
24365 additive-expression - multiplicative-expression
24367 (<a href="#6.5.7">6.5.7</a>) shift-expression:
24369 additive-expression
24370 shift-expression << additive-expression
24371 shift-expression >> additive-expression
24373 (<a href="#6.5.8">6.5.8</a>) relational-expression:
24376 relational-expression < shift-expression
24377 relational-expression > shift-expression
24378 relational-expression <= shift-expression
24379 relational-expression >= shift-expression
24381 (<a href="#6.5.9">6.5.9</a>) equality-expression:
24383 relational-expression
24384 equality-expression == relational-expression
24385 equality-expression != relational-expression
24387 (<a href="#6.5.10">6.5.10</a>) AND-expression:
24389 equality-expression
24390 AND-expression & equality-expression
24392 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
24396 exclusive-OR-expression ^ AND-expression
24398 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
24400 exclusive-OR-expression
24401 inclusive-OR-expression | exclusive-OR-expression
24403 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
24405 inclusive-OR-expression
24406 logical-AND-expression && inclusive-OR-expression
24408 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
24410 logical-AND-expression
24411 logical-OR-expression || logical-AND-expression
24413 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
24415 logical-OR-expression
24416 logical-OR-expression ? expression : conditional-expression
24418 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
24420 conditional-expression
24421 unary-expression assignment-operator assignment-expression
24423 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
24425 = *= /= %= += -= <<= >>= &= ^= |=
24427 (<a href="#6.5.17">6.5.17</a>) expression:
24429 assignment-expression
24430 expression , assignment-expression
24432 (<a href="#6.6">6.6</a>) constant-expression:
24434 conditional-expression
24437 <p><small><a href="#Contents">Contents</a></small>
24438 <h4><a name="A.2.2" href="#A.2.2">A.2.2 Declarations</a></h4>
24439 (<a href="#6.7">6.7</a>) declaration:
24441 declaration-specifiers init-declarator-list<sub>opt</sub> ;
24442 static_assert-declaration
24444 (<a href="#6.7">6.7</a>) declaration-specifiers:
24446 storage-class-specifier declaration-specifiers<sub>opt</sub>
24447 type-specifier declaration-specifiers<sub>opt</sub>
24448 type-qualifier declaration-specifiers<sub>opt</sub>
24449 function-specifier declaration-specifiers<sub>opt</sub>
24450 alignment-specifier declaration-specifiers<sub>opt</sub>
24452 (<a href="#6.7">6.7</a>) init-declarator-list:
24456 init-declarator-list , init-declarator
24458 (<a href="#6.7">6.7</a>) init-declarator:
24461 declarator = initializer
24463 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
24472 (<a href="#6.7.2">6.7.2</a>) type-specifier:
24485 atomic-type-specifier
24486 struct-or-union-specifier
24490 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
24492 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
24493 struct-or-union identifier
24495 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
24500 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
24503 struct-declaration-list struct-declaration
24505 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
24508 specifier-qualifier-list struct-declarator-list<sub>opt</sub> ;
24509 static_assert-declaration
24511 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
24513 type-specifier specifier-qualifier-list<sub>opt</sub>
24514 type-qualifier specifier-qualifier-list<sub>opt</sub>
24516 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
24519 struct-declarator-list , struct-declarator
24521 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
24524 declarator<sub>opt</sub> : constant-expression
24526 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
24528 enum identifier<sub>opt</sub> { enumerator-list }
24529 enum identifier<sub>opt</sub> { enumerator-list , }
24532 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
24535 enumerator-list , enumerator
24537 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
24539 enumeration-constant
24540 enumeration-constant = constant-expression
24542 (<a href="#6.7.2.4">6.7.2.4</a>) atomic-type-specifier:
24544 _Atomic ( type-name )
24546 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
24553 (<a href="#6.7.4">6.7.4</a>) function-specifier:
24558 (<a href="#6.7.5">6.7.5</a>) alignment-specifier:
24560 _Alignas ( type-name )
24561 _Alignas ( constant-expression )
24563 (<a href="#6.7.6">6.7.6</a>) declarator:
24566 pointer<sub>opt</sub> direct-declarator
24568 (<a href="#6.7.6">6.7.6</a>) direct-declarator:
24572 direct-declarator [ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
24573 direct-declarator [ static type-qualifier-list<sub>opt</sub> assignment-expression ]
24574 direct-declarator [ type-qualifier-list static assignment-expression ]
24575 direct-declarator [ type-qualifier-list<sub>opt</sub> * ]
24576 direct-declarator ( parameter-type-list )
24577 direct-declarator ( identifier-list<sub>opt</sub> )
24579 (<a href="#6.7.6">6.7.6</a>) pointer:
24581 * type-qualifier-list<sub>opt</sub>
24582 * type-qualifier-list<sub>opt</sub> pointer
24584 (<a href="#6.7.6">6.7.6</a>) type-qualifier-list:
24587 type-qualifier-list type-qualifier
24589 (<a href="#6.7.6">6.7.6</a>) parameter-type-list:
24592 parameter-list , ...
24594 (<a href="#6.7.6">6.7.6</a>) parameter-list:
24596 parameter-declaration
24597 parameter-list , parameter-declaration
24599 (<a href="#6.7.6">6.7.6</a>) parameter-declaration:
24601 declaration-specifiers declarator
24602 declaration-specifiers abstract-declarator<sub>opt</sub>
24604 (<a href="#6.7.6">6.7.6</a>) identifier-list:
24607 identifier-list , identifier
24609 (<a href="#6.7.7">6.7.7</a>) type-name:
24611 specifier-qualifier-list abstract-declarator<sub>opt</sub>
24613 (<a href="#6.7.7">6.7.7</a>) abstract-declarator:
24617 pointer<sub>opt</sub> direct-abstract-declarator
24619 (<a href="#6.7.7">6.7.7</a>) direct-abstract-declarator:
24621 ( abstract-declarator )
24622 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list<sub>opt</sub>
24623 assignment-expression<sub>opt</sub> ]
24624 direct-abstract-declarator<sub>opt</sub> [ static type-qualifier-list<sub>opt</sub>
24625 assignment-expression ]
24626 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list static
24627 assignment-expression ]
24628 direct-abstract-declarator<sub>opt</sub> [ * ]
24629 direct-abstract-declarator<sub>opt</sub> ( parameter-type-list<sub>opt</sub> )
24631 (<a href="#6.7.8">6.7.8</a>) typedef-name:
24635 (<a href="#6.7.9">6.7.9</a>) initializer:
24637 assignment-expression
24638 { initializer-list }
24639 { initializer-list , }
24641 (<a href="#6.7.9">6.7.9</a>) initializer-list:
24643 designation<sub>opt</sub> initializer
24644 initializer-list , designation<sub>opt</sub> initializer
24646 (<a href="#6.7.9">6.7.9</a>) designation:
24650 (<a href="#6.7.9">6.7.9</a>) designator-list:
24653 designator-list designator
24655 (<a href="#6.7.9">6.7.9</a>) designator:
24657 [ constant-expression ]
24660 (<a href="#6.7.10">6.7.10</a>) static_assert-declaration:
24663 _Static_assert ( constant-expression , string-literal ) ;
24666 <p><small><a href="#Contents">Contents</a></small>
24667 <h4><a name="A.2.3" href="#A.2.3">A.2.3 Statements</a></h4>
24668 (<a href="#6.8">6.8</a>) statement:
24672 expression-statement
24673 selection-statement
24674 iteration-statement
24677 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
24679 identifier : statement
24680 case constant-expression : statement
24681 default : statement
24683 (<a href="#6.8.2">6.8.2</a>) compound-statement:
24685 { block-item-list<sub>opt</sub> }
24687 (<a href="#6.8.2">6.8.2</a>) block-item-list:
24690 block-item-list block-item
24692 (<a href="#6.8.2">6.8.2</a>) block-item:
24697 (<a href="#6.8.3">6.8.3</a>) expression-statement:
24699 expression<sub>opt</sub> ;
24701 (<a href="#6.8.4">6.8.4</a>) selection-statement:
24703 if ( expression ) statement
24704 if ( expression ) statement else statement
24705 switch ( expression ) statement
24707 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
24709 while ( expression ) statement
24710 do statement while ( expression ) ;
24711 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
24712 for ( declaration expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
24714 (<a href="#6.8.6">6.8.6</a>) jump-statement:
24720 return expression<sub>opt</sub> ;
24723 <p><small><a href="#Contents">Contents</a></small>
24724 <h4><a name="A.2.4" href="#A.2.4">A.2.4 External definitions</a></h4>
24725 (<a href="#6.9">6.9</a>) translation-unit:
24727 external-declaration
24728 translation-unit external-declaration
24730 (<a href="#6.9">6.9</a>) external-declaration:
24732 function-definition
24735 (<a href="#6.9.1">6.9.1</a>) function-definition:
24737 declaration-specifiers declarator declaration-list<sub>opt</sub> compound-statement
24739 (<a href="#6.9.1">6.9.1</a>) declaration-list:
24742 declaration-list declaration
24745 <p><small><a href="#Contents">Contents</a></small>
24746 <h3><a name="A.3" href="#A.3">A.3 Preprocessing directives</a></h3>
24747 (<a href="#6.10">6.10</a>) preprocessing-file:
24749 group<sub>opt</sub>
24751 (<a href="#6.10">6.10</a>) group:
24756 (<a href="#6.10">6.10</a>) group-part:
24763 (<a href="#6.10">6.10</a>) if-section:
24765 if-group elif-groups<sub>opt</sub> else-group<sub>opt</sub> endif-line
24767 (<a href="#6.10">6.10</a>) if-group:
24769 # if constant-expression new-line group<sub>opt</sub>
24770 # ifdef identifier new-line group<sub>opt</sub>
24771 # ifndef identifier new-line group<sub>opt</sub>
24773 (<a href="#6.10">6.10</a>) elif-groups:
24776 elif-groups elif-group
24778 (<a href="#6.10">6.10</a>) elif-group:
24781 # elif constant-expression new-line group<sub>opt</sub>
24783 (<a href="#6.10">6.10</a>) else-group:
24785 # else new-line group<sub>opt</sub>
24787 (<a href="#6.10">6.10</a>) endif-line:
24791 (<a href="#6.10">6.10</a>) control-line:
24793 # include pp-tokens new-line
24794 # define identifier replacement-list new-line
24795 # define identifier lparen identifier-list<sub>opt</sub> )
24796 replacement-list new-line
24797 # define identifier lparen ... ) replacement-list new-line
24798 # define identifier lparen identifier-list , ... )
24799 replacement-list new-line
24800 # undef identifier new-line
24801 # line pp-tokens new-line
24802 # error pp-tokens<sub>opt</sub> new-line
24803 # pragma pp-tokens<sub>opt</sub> new-line
24806 (<a href="#6.10">6.10</a>) text-line:
24808 pp-tokens<sub>opt</sub> new-line
24810 (<a href="#6.10">6.10</a>) non-directive:
24814 (<a href="#6.10">6.10</a>) lparen:
24816 a ( character not immediately preceded by white-space
24818 (<a href="#6.10">6.10</a>) replacement-list:
24820 pp-tokens<sub>opt</sub>
24822 (<a href="#6.10">6.10</a>) pp-tokens:
24824 preprocessing-token
24825 pp-tokens preprocessing-token
24827 (<a href="#6.10">6.10</a>) new-line:
24830 the new-line character
24833 <p><small><a href="#Contents">Contents</a></small>
24834 <h2><a name="B" href="#B">Annex B</a></h2>
24840 <p><small><a href="#Contents">Contents</a></small>
24841 <h3><a name="B.1" href="#B.1">B.1 Diagnostics <assert.h></a></h3>
24845 void assert(scalar expression);
24848 <p><small><a href="#Contents">Contents</a></small>
24849 <h3><a name="B.2" href="#B.2">B.2 Complex <complex.h></a></h3>
24853 __STDC_NO_COMPLEX__ imaginary
24854 complex _Imaginary_I
24856 #pragma STDC CX_LIMITED_RANGE on-off-switch
24857 double complex cacos(double complex z);
24858 float complex cacosf(float complex z);
24859 long double complex cacosl(long double complex z);
24860 double complex casin(double complex z);
24861 float complex casinf(float complex z);
24862 long double complex casinl(long double complex z);
24863 double complex catan(double complex z);
24864 float complex catanf(float complex z);
24865 long double complex catanl(long double complex z);
24866 double complex ccos(double complex z);
24867 float complex ccosf(float complex z);
24868 long double complex ccosl(long double complex z);
24869 double complex csin(double complex z);
24870 float complex csinf(float complex z);
24871 long double complex csinl(long double complex z);
24872 double complex ctan(double complex z);
24873 float complex ctanf(float complex z);
24874 long double complex ctanl(long double complex z);
24875 double complex cacosh(double complex z);
24876 float complex cacoshf(float complex z);
24877 long double complex cacoshl(long double complex z);
24878 double complex casinh(double complex z);
24879 float complex casinhf(float complex z);
24880 long double complex casinhl(long double complex z);
24881 double complex catanh(double complex z);
24882 float complex catanhf(float complex z);
24883 long double complex catanhl(long double complex z);
24884 double complex ccosh(double complex z);
24885 float complex ccoshf(float complex z);
24886 long double complex ccoshl(long double complex z);
24887 double complex csinh(double complex z);
24888 float complex csinhf(float complex z);
24889 long double complex csinhl(long double complex z);
24890 double complex ctanh(double complex z);
24891 float complex ctanhf(float complex z);
24892 long double complex ctanhl(long double complex z);
24893 double complex cexp(double complex z);
24894 float complex cexpf(float complex z);
24895 long double complex cexpl(long double complex z);
24896 double complex clog(double complex z);
24897 float complex clogf(float complex z);
24898 long double complex clogl(long double complex z);
24899 double cabs(double complex z);
24900 float cabsf(float complex z);
24901 long double cabsl(long double complex z);
24902 double complex cpow(double complex x, double complex y);
24903 float complex cpowf(float complex x, float complex y);
24904 long double complex cpowl(long double complex x,
24905 long double complex y);
24906 double complex csqrt(double complex z);
24907 float complex csqrtf(float complex z);
24908 long double complex csqrtl(long double complex z);
24909 double carg(double complex z);
24910 float cargf(float complex z);
24911 long double cargl(long double complex z);
24912 double cimag(double complex z);
24913 float cimagf(float complex z);
24914 long double cimagl(long double complex z);
24915 double complex CMPLX(double x, double y);
24916 float complex CMPLXF(float x, float y);
24917 long double complex CMPLXL(long double x, long double y);
24918 double complex conj(double complex z);
24919 float complex conjf(float complex z);
24920 long double complex conjl(long double complex z);
24921 double complex cproj(double complex z);
24922 float complex cprojf(float complex z);
24923 long double complex cprojl(long double complex z);
24924 double creal(double complex z);
24925 float crealf(float complex z);
24926 long double creall(long double complex z);
24929 <p><small><a href="#Contents">Contents</a></small>
24930 <h3><a name="B.3" href="#B.3">B.3 Character handling <ctype.h></a></h3>
24932 int isalnum(int c);
24933 int isalpha(int c);
24934 int isblank(int c);
24935 int iscntrl(int c);
24936 int isdigit(int c);
24937 int isgraph(int c);
24938 int islower(int c);
24939 int isprint(int c);
24940 int ispunct(int c);
24941 int isspace(int c);
24942 int isupper(int c);
24943 int isxdigit(int c);
24944 int tolower(int c);
24945 int toupper(int c);
24948 <p><small><a href="#Contents">Contents</a></small>
24949 <h3><a name="B.4" href="#B.4">B.4 Errors <errno.h></a></h3>
24951 EDOM EILSEQ ERANGE errno
24952 __STDC_WANT_LIB_EXT1__
24956 <p><small><a href="#Contents">Contents</a></small>
24957 <h3><a name="B.5" href="#B.5">B.5 Floating-point environment <fenv.h></a></h3>
24960 fenv_t FE_OVERFLOW FE_TOWARDZERO
24961 fexcept_t FE_UNDERFLOW FE_UPWARD
24962 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
24963 FE_INEXACT FE_DOWNWARD
24964 FE_INVALID FE_TONEAREST
24965 #pragma STDC FENV_ACCESS on-off-switch
24966 int feclearexcept(int excepts);
24967 int fegetexceptflag(fexcept_t *flagp, int excepts);
24968 int feraiseexcept(int excepts);
24969 int fesetexceptflag(const fexcept_t *flagp,
24971 int fetestexcept(int excepts);
24972 int fegetround(void);
24973 int fesetround(int round);
24974 int fegetenv(fenv_t *envp);
24975 int feholdexcept(fenv_t *envp);
24976 int fesetenv(const fenv_t *envp);
24977 int feupdateenv(const fenv_t *envp);
24980 <p><small><a href="#Contents">Contents</a></small>
24981 <h3><a name="B.6" href="#B.6">B.6 Characteristics of floating types <float.h></a></h3>
24983 FLT_ROUNDS DBL_DIG FLT_MAX
24984 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
24985 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
24986 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
24987 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
24988 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
24989 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
24990 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
24991 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
24992 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
24993 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
24994 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
24995 DECIMAL_DIG DBL_MAX_10_EXP
24996 FLT_DIG LDBL_MAX_10_EXP
24999 <p><small><a href="#Contents">Contents</a></small>
25000 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
25004 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
25005 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
25006 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
25007 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
25008 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
25009 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
25010 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
25011 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
25012 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
25013 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
25014 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
25015 intmax_t imaxabs(intmax_t j);
25016 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
25017 intmax_t strtoimax(const char * restrict nptr,
25018 char ** restrict endptr, int base);
25019 uintmax_t strtoumax(const char * restrict nptr,
25020 char ** restrict endptr, int base);
25021 intmax_t wcstoimax(const wchar_t * restrict nptr,
25022 wchar_t ** restrict endptr, int base);
25023 uintmax_t wcstoumax(const wchar_t * restrict nptr,
25024 wchar_t ** restrict endptr, int base);
25027 <p><small><a href="#Contents">Contents</a></small>
25028 <h3><a name="B.8" href="#B.8">B.8 Alternative spellings <iso646.h></a></h3>
25030 and bitor not_eq xor
25031 and_eq compl or xor_eq
25035 <p><small><a href="#Contents">Contents</a></small>
25036 <h3><a name="B.9" href="#B.9">B.9 Sizes of integer types <limits.h></a></h3>
25038 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
25039 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
25040 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
25041 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
25042 CHAR_MIN USHRT_MAX LONG_MAX
25045 <p><small><a href="#Contents">Contents</a></small>
25046 <h3><a name="B.10" href="#B.10">B.10 Localization <locale.h></a></h3>
25048 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
25049 NULL LC_COLLATE LC_MONETARY LC_TIME
25050 char *setlocale(int category, const char *locale);
25051 struct lconv *localeconv(void);
25054 <p><small><a href="#Contents">Contents</a></small>
25055 <h3><a name="B.11" href="#B.11">B.11 Mathematics <math.h></a></h3>
25062 float_t FP_INFINITE FP_FAST_FMAL
25063 double_t FP_NAN FP_ILOGB0
25064 HUGE_VAL FP_NORMAL FP_ILOGBNAN
25065 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
25066 HUGE_VALL FP_ZERO MATH_ERREXCEPT
25067 INFINITY FP_FAST_FMA math_errhandling
25069 #pragma STDC FP_CONTRACT on-off-switch
25070 int fpclassify(real-floating x);
25071 int isfinite(real-floating x);
25072 int isinf(real-floating x);
25073 int isnan(real-floating x);
25074 int isnormal(real-floating x);
25075 int signbit(real-floating x);
25076 double acos(double x);
25077 float acosf(float x);
25078 long double acosl(long double x);
25079 double asin(double x);
25080 float asinf(float x);
25081 long double asinl(long double x);
25082 double atan(double x);
25083 float atanf(float x);
25084 long double atanl(long double x);
25085 double atan2(double y, double x);
25086 float atan2f(float y, float x);
25087 long double atan2l(long double y, long double x);
25088 double cos(double x);
25089 float cosf(float x);
25090 long double cosl(long double x);
25091 double sin(double x);
25092 float sinf(float x);
25093 long double sinl(long double x);
25094 double tan(double x);
25095 float tanf(float x);
25096 long double tanl(long double x);
25097 double acosh(double x);
25098 float acoshf(float x);
25099 long double acoshl(long double x);
25100 double asinh(double x);
25101 float asinhf(float x);
25102 long double asinhl(long double x);
25103 double atanh(double x);
25104 float atanhf(float x);
25105 long double atanhl(long double x);
25106 double cosh(double x);
25107 float coshf(float x);
25108 long double coshl(long double x);
25109 double sinh(double x);
25110 float sinhf(float x);
25111 long double sinhl(long double x);
25112 double tanh(double x);
25113 float tanhf(float x);
25114 long double tanhl(long double x);
25115 double exp(double x);
25116 float expf(float x);
25117 long double expl(long double x);
25118 double exp2(double x);
25119 float exp2f(float x);
25120 long double exp2l(long double x);
25121 double expm1(double x);
25122 float expm1f(float x);
25123 long double expm1l(long double x);
25124 double frexp(double value, int *exp);
25125 float frexpf(float value, int *exp);
25126 long double frexpl(long double value, int *exp);
25127 int ilogb(double x);
25128 int ilogbf(float x);
25129 int ilogbl(long double x);
25130 double ldexp(double x, int exp);
25131 float ldexpf(float x, int exp);
25132 long double ldexpl(long double x, int exp);
25133 double log(double x);
25134 float logf(float x);
25135 long double logl(long double x);
25136 double log10(double x);
25137 float log10f(float x);
25138 long double log10l(long double x);
25139 double log1p(double x);
25140 float log1pf(float x);
25141 long double log1pl(long double x);
25142 double log2(double x);
25143 float log2f(float x);
25144 long double log2l(long double x);
25145 double logb(double x);
25146 float logbf(float x);
25147 long double logbl(long double x);
25148 double modf(double value, double *iptr);
25149 float modff(float value, float *iptr);
25150 long double modfl(long double value, long double *iptr);
25151 double scalbn(double x, int n);
25152 float scalbnf(float x, int n);
25153 long double scalbnl(long double x, int n);
25154 double scalbln(double x, long int n);
25155 float scalblnf(float x, long int n);
25156 long double scalblnl(long double x, long int n);
25157 double cbrt(double x);
25158 float cbrtf(float x);
25159 long double cbrtl(long double x);
25160 double fabs(double x);
25161 float fabsf(float x);
25162 long double fabsl(long double x);
25163 double hypot(double x, double y);
25164 float hypotf(float x, float y);
25165 long double hypotl(long double x, long double y);
25166 double pow(double x, double y);
25167 float powf(float x, float y);
25168 long double powl(long double x, long double y);
25169 double sqrt(double x);
25170 float sqrtf(float x);
25171 long double sqrtl(long double x);
25172 double erf(double x);
25173 float erff(float x);
25174 long double erfl(long double x);
25175 double erfc(double x);
25176 float erfcf(float x);
25177 long double erfcl(long double x);
25178 double lgamma(double x);
25179 float lgammaf(float x);
25180 long double lgammal(long double x);
25181 double tgamma(double x);
25182 float tgammaf(float x);
25183 long double tgammal(long double x);
25184 double ceil(double x);
25185 float ceilf(float x);
25186 long double ceill(long double x);
25187 double floor(double x);
25188 float floorf(float x);
25189 long double floorl(long double x);
25190 double nearbyint(double x);
25191 float nearbyintf(float x);
25192 long double nearbyintl(long double x);
25193 double rint(double x);
25194 float rintf(float x);
25195 long double rintl(long double x);
25196 long int lrint(double x);
25197 long int lrintf(float x);
25198 long int lrintl(long double x);
25199 long long int llrint(double x);
25200 long long int llrintf(float x);
25201 long long int llrintl(long double x);
25202 double round(double x);
25203 float roundf(float x);
25204 long double roundl(long double x);
25205 long int lround(double x);
25206 long int lroundf(float x);
25207 long int lroundl(long double x);
25208 long long int llround(double x);
25209 long long int llroundf(float x);
25210 long long int llroundl(long double x);
25211 double trunc(double x);
25212 float truncf(float x);
25213 long double truncl(long double x);
25214 double fmod(double x, double y);
25215 float fmodf(float x, float y);
25216 long double fmodl(long double x, long double y);
25217 double remainder(double x, double y);
25218 float remainderf(float x, float y);
25219 long double remainderl(long double x, long double y);
25220 double remquo(double x, double y, int *quo);
25221 float remquof(float x, float y, int *quo);
25222 long double remquol(long double x, long double y,
25224 double copysign(double x, double y);
25225 float copysignf(float x, float y);
25226 long double copysignl(long double x, long double y);
25227 double nan(const char *tagp);
25228 float nanf(const char *tagp);
25229 long double nanl(const char *tagp);
25230 double nextafter(double x, double y);
25231 float nextafterf(float x, float y);
25232 long double nextafterl(long double x, long double y);
25233 double nexttoward(double x, long double y);
25234 float nexttowardf(float x, long double y);
25235 long double nexttowardl(long double x, long double y);
25236 double fdim(double x, double y);
25237 float fdimf(float x, float y);
25238 long double fdiml(long double x, long double y);
25239 double fmax(double x, double y);
25240 float fmaxf(float x, float y);
25241 long double fmaxl(long double x, long double y);
25242 double fmin(double x, double y);
25243 float fminf(float x, float y);
25244 long double fminl(long double x, long double y);
25245 double fma(double x, double y, double z);
25246 float fmaf(float x, float y, float z);
25247 long double fmal(long double x, long double y,
25249 int isgreater(real-floating x, real-floating y);
25250 int isgreaterequal(real-floating x, real-floating y);
25251 int isless(real-floating x, real-floating y);
25252 int islessequal(real-floating x, real-floating y);
25253 int islessgreater(real-floating x, real-floating y);
25254 int isunordered(real-floating x, real-floating y);
25257 <p><small><a href="#Contents">Contents</a></small>
25258 <h3><a name="B.12" href="#B.12">B.12 Nonlocal jumps <setjmp.h></a></h3>
25261 int setjmp(jmp_buf env);
25262 _Noreturn void longjmp(jmp_buf env, int val);
25265 <p><small><a href="#Contents">Contents</a></small>
25266 <h3><a name="B.13" href="#B.13">B.13 Signal handling <signal.h></a></h3>
25269 sig_atomic_t SIG_IGN SIGILL SIGTERM
25270 SIG_DFL SIGABRT SIGINT
25271 SIG_ERR SIGFPE SIGSEGV
25272 void (*signal(int sig, void (*func)(int)))(int);
25273 int raise(int sig);
25276 <p><small><a href="#Contents">Contents</a></small>
25277 <h3><a name="B.14" href="#B.14">B.14 Alignment <stdalign.h></a></h3>
25280 __alignas_is_defined
25283 <p><small><a href="#Contents">Contents</a></small>
25284 <h3><a name="B.15" href="#B.15">B.15 Variable arguments <stdarg.h></a></h3>
25287 type va_arg(va_list ap, type);
25288 void va_copy(va_list dest, va_list src);
25289 void va_end(va_list ap);
25290 void va_start(va_list ap, parmN);
25293 <p><small><a href="#Contents">Contents</a></small>
25294 <h3><a name="B.16" href="#B.16">B.16 Atomics <stdatomic.h></a></h3>
25298 ATOMIC_BOOL_LOCK_FREE atomic_uint
25299 ATOMIC_CHAR_LOCK_FREE atomic_long
25300 ATOMIC_CHAR16_T_LOCK_FREE atomic_ulong
25301 ATOMIC_CHAR32_T_LOCK_FREE atomic_llong
25302 ATOMIC_WCHAR_T_LOCK_FREE atomic_ullong
25303 ATOMIC_SHORT_LOCK_FREE atomic_char16_t
25304 ATOMIC_INT_LOCK_FREE atomic_char32_t
25305 ATOMIC_LONG_LOCK_FREE atomic_wchar_t
25306 ATOMIC_LLONG_LOCK_FREE atomic_int_least8_t
25307 ATOMIC_POINTER_LOCK_FREE atomic_uint_least8_t
25308 ATOMIC_FLAG_INIT atomic_int_least16_t
25309 memory_order atomic_uint_least16_t
25310 atomic_flag atomic_int_least32_t
25311 memory_order_relaxed * atomic_uint_least32_t
25312 memory_order_consume atomic_int_least64_t
25313 memory_order_acquire atomic_uint_least64_t
25314 memory_order_release atomic_int_fast8_t
25315 memory_order_acq_rel atomic_uint_fast8_t
25316 memory_order_seq_cst atomic_int_fast16_t
25317 atomic_bool atomic_uint_fast16_t
25318 atomic_char atomic_int_fast32_t
25319 atomic_schar atomic_uint_fast32_t
25320 atomic_uchar atomic_int_fast64_t
25321 atomic_short atomic_uint_fast64_t
25322 atomic_ushort atomic_intptr_t
25323 atomic_int atomic_uintptr_t
25324 atomic_size_t atomic_intmax_t
25325 atomic_ptrdiff_t atomic_uintmax_t
25326 #define ATOMIC_VAR_INIT(C value)
25327 void atomic_init(volatile A *obj, C value);
25328 type kill_dependency(type y);
25329 void atomic_thread_fence(memory_order order);
25330 void atomic_signal_fence(memory_order order);
25331 _Bool atomic_is_lock_free(const volatile A *obj);
25332 void atomic_store(volatile A *object, C desired);
25333 void atomic_store_explicit(volatile A *object,
25334 C desired, memory_order order);
25335 C atomic_load(volatile A *object);
25336 C atomic_load_explicit(volatile A *object,
25337 memory_order order);
25338 C atomic_exchange(volatile A *object, C desired);
25339 C atomic_exchange_explicit(volatile A *object,
25340 C desired, memory_order order);
25341 _Bool atomic_compare_exchange_strong(volatile A *object,
25342 C *expected, C desired);
25343 _Bool atomic_compare_exchange_strong_explicit(
25344 volatile A *object, C *expected, C desired,
25345 memory_order success, memory_order failure);
25346 _Bool atomic_compare_exchange_weak(volatile A *object,
25347 C *expected, C desired);
25348 _Bool atomic_compare_exchange_weak_explicit(
25349 volatile A *object, C *expected, C desired,
25350 memory_order success, memory_order failure);
25351 C atomic_fetch_key(volatile A *object, M operand);
25352 C atomic_fetch_key_explicit(volatile A *object,
25353 M operand, memory_order order);
25354 _Bool atomic_flag_test_and_set(
25355 volatile atomic_flag *object);
25356 _Bool atomic_flag_test_and_set_explicit(
25357 volatile atomic_flag *object, memory_order order);
25358 void atomic_flag_clear(volatile atomic_flag *object);
25359 void atomic_flag_clear_explicit(
25360 volatile atomic_flag *object, memory_order order);
25363 <p><small><a href="#Contents">Contents</a></small>
25364 <h3><a name="B.17" href="#B.17">B.17 Boolean type and values <stdbool.h></a></h3>
25369 __bool_true_false_are_defined
25372 <p><small><a href="#Contents">Contents</a></small>
25373 <h3><a name="B.18" href="#B.18">B.18 Common definitions <stddef.h></a></h3>
25375 ptrdiff_t max_align_t NULL
25377 offsetof(type, member-designator)
25378 __STDC_WANT_LIB_EXT1__
25382 <p><small><a href="#Contents">Contents</a></small>
25383 <h3><a name="B.19" href="#B.19">B.19 Integer types <stdint.h></a></h3>
25386 intN_t INT_LEASTN_MIN PTRDIFF_MAX
25387 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
25388 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
25389 uint_leastN_t INT_FASTN_MIN SIZE_MAX
25390 int_fastN_t INT_FASTN_MAX WCHAR_MIN
25391 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
25392 intptr_t INTPTR_MIN WINT_MIN
25393 uintptr_t INTPTR_MAX WINT_MAX
25394 intmax_t UINTPTR_MAX INTN_C(value)
25395 uintmax_t INTMAX_MIN UINTN_C(value)
25396 INTN_MIN INTMAX_MAX INTMAX_C(value)
25397 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
25398 UINTN_MAX PTRDIFF_MIN
25399 __STDC_WANT_LIB_EXT1__
25403 <p><small><a href="#Contents">Contents</a></small>
25404 <h3><a name="B.20" href="#B.20">B.20 Input/output <stdio.h></a></h3>
25409 size_t _IOLBF FILENAME_MAX TMP_MAX
25410 FILE _IONBF L_tmpnam stderr
25411 fpos_t BUFSIZ SEEK_CUR stdin
25412 NULL EOF SEEK_END stdout
25413 _IOFBF FOPEN_MAX SEEK_SET
25414 int remove(const char *filename);
25415 int rename(const char *old, const char *new);
25416 FILE *tmpfile(void);
25417 char *tmpnam(char *s);
25418 int fclose(FILE *stream);
25419 int fflush(FILE *stream);
25420 FILE *fopen(const char * restrict filename,
25421 const char * restrict mode);
25422 FILE *freopen(const char * restrict filename,
25423 const char * restrict mode,
25424 FILE * restrict stream);
25425 void setbuf(FILE * restrict stream,
25426 char * restrict buf);
25427 int setvbuf(FILE * restrict stream,
25428 char * restrict buf,
25429 int mode, size_t size);
25430 int fprintf(FILE * restrict stream,
25431 const char * restrict format, ...);
25432 int fscanf(FILE * restrict stream,
25433 const char * restrict format, ...);
25434 int printf(const char * restrict format, ...);
25435 int scanf(const char * restrict format, ...);
25436 int snprintf(char * restrict s, size_t n,
25437 const char * restrict format, ...);
25438 int sprintf(char * restrict s,
25439 const char * restrict format, ...);
25440 int sscanf(const char * restrict s,
25441 const char * restrict format, ...);
25442 int vfprintf(FILE * restrict stream,
25443 const char * restrict format, va_list arg);
25444 int vfscanf(FILE * restrict stream,
25445 const char * restrict format, va_list arg);
25446 int vprintf(const char * restrict format, va_list arg);
25447 int vscanf(const char * restrict format, va_list arg);
25448 int vsnprintf(char * restrict s, size_t n,
25449 const char * restrict format, va_list arg);
25450 int vsprintf(char * restrict s,
25451 const char * restrict format, va_list arg);
25452 int vsscanf(const char * restrict s,
25453 const char * restrict format, va_list arg);
25454 int fgetc(FILE *stream);
25455 char *fgets(char * restrict s, int n,
25456 FILE * restrict stream);
25457 int fputc(int c, FILE *stream);
25458 int fputs(const char * restrict s,
25459 FILE * restrict stream);
25460 int getc(FILE *stream);
25462 int putc(int c, FILE *stream);
25463 int putchar(int c);
25464 int puts(const char *s);
25465 int ungetc(int c, FILE *stream);
25466 size_t fread(void * restrict ptr,
25467 size_t size, size_t nmemb,
25468 FILE * restrict stream);
25469 size_t fwrite(const void * restrict ptr,
25470 size_t size, size_t nmemb,
25471 FILE * restrict stream);
25472 int fgetpos(FILE * restrict stream,
25473 fpos_t * restrict pos);
25474 int fseek(FILE *stream, long int offset, int whence);
25475 int fsetpos(FILE *stream, const fpos_t *pos);
25476 long int ftell(FILE *stream);
25477 void rewind(FILE *stream);
25478 void clearerr(FILE *stream);
25479 int feof(FILE *stream);
25480 int ferror(FILE *stream);
25481 void perror(const char *s);
25482 __STDC_WANT_LIB_EXT1__
25483 L_tmpnam_s TMP_MAX_S errno_t rsize_t
25484 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
25485 errno_t tmpnam_s(char *s, rsize_t maxsize);
25486 errno_t fopen_s(FILE * restrict * restrict streamptr,
25487 const char * restrict filename,
25488 const char * restrict mode);
25489 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
25490 const char * restrict filename,
25491 const char * restrict mode,
25492 FILE * restrict stream);
25493 int fprintf_s(FILE * restrict stream,
25494 const char * restrict format, ...);
25495 int fscanf_s(FILE * restrict stream,
25496 const char * restrict format, ...);
25497 int printf_s(const char * restrict format, ...);
25498 int scanf_s(const char * restrict format, ...);
25499 int snprintf_s(char * restrict s, rsize_t n,
25500 const char * restrict format, ...);
25501 int sprintf_s(char * restrict s, rsize_t n,
25502 const char * restrict format, ...);
25503 int sscanf_s(const char * restrict s,
25504 const char * restrict format, ...);
25505 int vfprintf_s(FILE * restrict stream,
25506 const char * restrict format,
25508 int vfscanf_s(FILE * restrict stream,
25509 const char * restrict format,
25511 int vprintf_s(const char * restrict format,
25513 int vscanf_s(const char * restrict format,
25515 int vsnprintf_s(char * restrict s, rsize_t n,
25516 const char * restrict format,
25518 int vsprintf_s(char * restrict s, rsize_t n,
25519 const char * restrict format,
25521 int vsscanf_s(const char * restrict s,
25522 const char * restrict format,
25524 char *gets_s(char *s, rsize_t n);
25527 <p><small><a href="#Contents">Contents</a></small>
25528 <h3><a name="B.21" href="#B.21">B.21 General utilities <stdlib.h></a></h3>
25532 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
25533 wchar_t lldiv_t EXIT_SUCCESS
25534 div_t NULL RAND_MAX
25535 double atof(const char *nptr);
25536 int atoi(const char *nptr);
25537 long int atol(const char *nptr);
25538 long long int atoll(const char *nptr);
25539 double strtod(const char * restrict nptr,
25540 char ** restrict endptr);
25541 float strtof(const char * restrict nptr,
25542 char ** restrict endptr);
25543 long double strtold(const char * restrict nptr,
25544 char ** restrict endptr);
25545 long int strtol(const char * restrict nptr,
25546 char ** restrict endptr, int base);
25547 long long int strtoll(const char * restrict nptr,
25548 char ** restrict endptr, int base);
25549 unsigned long int strtoul(
25550 const char * restrict nptr,
25551 char ** restrict endptr, int base);
25552 unsigned long long int strtoull(
25553 const char * restrict nptr,
25554 char ** restrict endptr, int base);
25556 void srand(unsigned int seed);
25557 void *aligned_alloc(size_t alignment, size_t size);
25558 void *calloc(size_t nmemb, size_t size);
25559 void free(void *ptr);
25560 void *malloc(size_t size);
25561 void *realloc(void *ptr, size_t size);
25562 _Noreturn void abort(void);
25563 int atexit(void (*func)(void));
25564 int at_quick_exit(void (*func)(void));
25565 _Noreturn void exit(int status);
25566 _Noreturn void _Exit(int status);
25567 char *getenv(const char *name);
25568 _Noreturn void quick_exit(int status);
25569 int system(const char *string);
25570 void *bsearch(const void *key, const void *base,
25571 size_t nmemb, size_t size,
25572 int (*compar)(const void *, const void *));
25573 void qsort(void *base, size_t nmemb, size_t size,
25574 int (*compar)(const void *, const void *));
25576 long int labs(long int j);
25577 long long int llabs(long long int j);
25578 div_t div(int numer, int denom);
25579 ldiv_t ldiv(long int numer, long int denom);
25580 lldiv_t lldiv(long long int numer,
25581 long long int denom);
25582 int mblen(const char *s, size_t n);
25583 int mbtowc(wchar_t * restrict pwc,
25584 const char * restrict s, size_t n);
25585 int wctomb(char *s, wchar_t wchar);
25586 size_t mbstowcs(wchar_t * restrict pwcs,
25587 const char * restrict s, size_t n);
25588 size_t wcstombs(char * restrict s,
25589 const wchar_t * restrict pwcs, size_t n);
25590 __STDC_WANT_LIB_EXT1__
25593 constraint_handler_t
25594 constraint_handler_t set_constraint_handler_s(
25595 constraint_handler_t handler);
25596 void abort_handler_s(
25597 const char * restrict msg,
25598 void * restrict ptr,
25600 void ignore_handler_s(
25601 const char * restrict msg,
25602 void * restrict ptr,
25604 errno_t getenv_s(size_t * restrict len,
25605 char * restrict value, rsize_t maxsize,
25606 const char * restrict name);
25607 void *bsearch_s(const void *key, const void *base,
25608 rsize_t nmemb, rsize_t size,
25609 int (*compar)(const void *k, const void *y,
25612 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
25613 int (*compar)(const void *x, const void *y,
25616 errno_t wctomb_s(int * restrict status,
25620 errno_t mbstowcs_s(size_t * restrict retval,
25621 wchar_t * restrict dst, rsize_t dstmax,
25622 const char * restrict src, rsize_t len);
25623 errno_t wcstombs_s(size_t * restrict retval,
25624 char * restrict dst, rsize_t dstmax,
25625 const wchar_t * restrict src, rsize_t len);
25628 <p><small><a href="#Contents">Contents</a></small>
25629 <h3><a name="B.22" href="#B.22">B.22 _Noreturn <stdnoreturn.h></a></h3>
25634 <p><small><a href="#Contents">Contents</a></small>
25635 <h3><a name="B.23" href="#B.23">B.23 String handling <string.h></a></h3>
25641 void *memcpy(void * restrict s1,
25642 const void * restrict s2, size_t n);
25643 void *memmove(void *s1, const void *s2, size_t n);
25644 char *strcpy(char * restrict s1,
25645 const char * restrict s2);
25646 char *strncpy(char * restrict s1,
25647 const char * restrict s2, size_t n);
25648 char *strcat(char * restrict s1,
25649 const char * restrict s2);
25650 char *strncat(char * restrict s1,
25651 const char * restrict s2, size_t n);
25652 int memcmp(const void *s1, const void *s2, size_t n);
25653 int strcmp(const char *s1, const char *s2);
25654 int strcoll(const char *s1, const char *s2);
25655 int strncmp(const char *s1, const char *s2, size_t n);
25656 size_t strxfrm(char * restrict s1,
25657 const char * restrict s2, size_t n);
25658 void *memchr(const void *s, int c, size_t n);
25659 char *strchr(const char *s, int c);
25660 size_t strcspn(const char *s1, const char *s2);
25661 char *strpbrk(const char *s1, const char *s2);
25662 char *strrchr(const char *s, int c);
25663 size_t strspn(const char *s1, const char *s2);
25664 char *strstr(const char *s1, const char *s2);
25665 char *strtok(char * restrict s1,
25666 const char * restrict s2);
25667 void *memset(void *s, int c, size_t n);
25668 char *strerror(int errnum);
25669 size_t strlen(const char *s);
25670 __STDC_WANT_LIB_EXT1__
25673 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
25674 const void * restrict s2, rsize_t n);
25675 errno_t memmove_s(void *s1, rsize_t s1max,
25676 const void *s2, rsize_t n);
25677 errno_t strcpy_s(char * restrict s1,
25679 const char * restrict s2);
25680 errno_t strncpy_s(char * restrict s1,
25682 const char * restrict s2,
25684 errno_t strcat_s(char * restrict s1,
25686 const char * restrict s2);
25687 errno_t strncat_s(char * restrict s1,
25689 const char * restrict s2,
25691 char *strtok_s(char * restrict s1,
25692 rsize_t * restrict s1max,
25693 const char * restrict s2,
25694 char ** restrict ptr);
25695 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
25696 errno_t strerror_s(char *s, rsize_t maxsize,
25698 size_t strerrorlen_s(errno_t errnum);
25699 size_t strnlen_s(const char *s, size_t maxsize);
25702 <p><small><a href="#Contents">Contents</a></small>
25703 <h3><a name="B.24" href="#B.24">B.24 Type-generic math <tgmath.h></a></h3>
25705 acos sqrt fmod nextafter
25706 asin fabs frexp nexttoward
25707 atan atan2 hypot remainder
25708 acosh cbrt ilogb remquo
25709 asinh ceil ldexp rint
25710 atanh copysign lgamma round
25711 cos erf llrint scalbn
25712 sin erfc llround scalbln
25713 tan exp2 log10 tgamma
25714 cosh expm1 log1p trunc
25715 sinh fdim log2 carg
25716 tanh floor logb cimag
25718 log fmax lround cproj
25719 pow fmin nearbyint creal
25722 <p><small><a href="#Contents">Contents</a></small>
25723 <h3><a name="B.25" href="#B.25">B.25 Threads <threads.h></a></h3>
25726 thread_local once_flag
25727 ONCE_FLAG_INIT mtx_plain *
25728 TSS_DTOR_ITERATIONS mtx_recursive
25730 thrd_t thrd_timedout
25733 tss_dtor_t thrd_error
25734 thrd_start_t thrd_nomem
25735 void call_once(once_flag *flag, void (*func)(void));
25736 int cnd_broadcast(cnd_t *cond);
25737 void cnd_destroy(cnd_t *cond);
25738 int cnd_init(cnd_t *cond);
25739 int cnd_signal(cnd_t *cond);
25740 int cnd_timedwait(cnd_t *restrict cond,
25741 mtx_t *restrict mtx,
25742 const struct timespec *restrict ts);
25743 int cnd_wait(cnd_t *cond, mtx_t *mtx);
25744 void mtx_destroy(mtx_t *mtx);
25745 int mtx_init(mtx_t *mtx, int type);
25746 int mtx_lock(mtx_t *mtx);
25747 int mtx_timedlock(mtx_t *restrict mtx,
25748 const struct timespec *restrict ts);
25749 int mtx_trylock(mtx_t *mtx);
25750 int mtx_unlock(mtx_t *mtx);
25751 int thrd_create(thrd_t *thr, thrd_start_t func,
25753 thrd_t thrd_current(void);
25754 int thrd_detach(thrd_t thr);
25755 int thrd_equal(thrd_t thr0, thrd_t thr1);
25756 _Noreturn void thrd_exit(int res);
25757 int thrd_join(thrd_t thr, int *res);
25758 int thrd_sleep(const struct timespec *duration,
25759 struct timespec *remaining);
25760 void thrd_yield(void);
25761 int tss_create(tss_t *key, tss_dtor_t dtor);
25762 void tss_delete(tss_t key);
25763 void *tss_get(tss_t key);
25764 int tss_set(tss_t key, void *val);
25767 <p><small><a href="#Contents">Contents</a></small>
25768 <h3><a name="B.26" href="#B.26">B.26 Date and time <time.h></a></h3>
25771 NULL size_t struct timespec
25772 CLOCKS_PER_SEC clock_t struct tm
25774 clock_t clock(void);
25775 double difftime(time_t time1, time_t time0);
25776 time_t mktime(struct tm *timeptr);
25777 time_t time(time_t *timer);
25778 int timespec_get(timespec *ts, int base);
25779 char *asctime(const struct tm *timeptr);
25780 char *ctime(const time_t *timer);
25781 struct tm *gmtime(const time_t *timer);
25782 struct tm *localtime(const time_t *timer);
25783 size_t strftime(char * restrict s,
25785 const char * restrict format,
25786 const struct tm * restrict timeptr);
25787 __STDC_WANT_LIB_EXT1__
25790 errno_t asctime_s(char *s, rsize_t maxsize,
25791 const struct tm *timeptr);
25792 errno_t ctime_s(char *s, rsize_t maxsize,
25793 const time_t *timer);
25794 struct tm *gmtime_s(const time_t * restrict timer,
25795 struct tm * restrict result);
25796 struct tm *localtime_s(const time_t * restrict timer,
25797 struct tm * restrict result);
25800 <p><small><a href="#Contents">Contents</a></small>
25801 <h3><a name="B.27" href="#B.27">B.27 Unicode utilities <uchar.h></a></h3>
25803 mbstate_t size_t char16_t char32_t
25804 size_t mbrtoc16(char16_t * restrict pc16,
25805 const char * restrict s, size_t n,
25806 mbstate_t * restrict ps);
25807 size_t c16rtomb(char * restrict s, char16_t c16,
25808 mbstate_t * restrict ps);
25809 size_t mbrtoc32(char32_t * restrict pc32,
25810 const char * restrict s, size_t n,
25811 mbstate_t * restrict ps);
25812 size_t c32rtomb(char * restrict s, char32_t c32,
25813 mbstate_t * restrict ps);
25816 <p><small><a href="#Contents">Contents</a></small>
25817 <h3><a name="B.28" href="#B.28">B.28 Extended multibyte/wide character utilities <wchar.h></a></h3>
25824 wchar_t wint_t WCHAR_MAX
25825 size_t struct tm WCHAR_MIN
25826 mbstate_t NULL WEOF
25827 int fwprintf(FILE * restrict stream,
25828 const wchar_t * restrict format, ...);
25829 int fwscanf(FILE * restrict stream,
25830 const wchar_t * restrict format, ...);
25831 int swprintf(wchar_t * restrict s, size_t n,
25832 const wchar_t * restrict format, ...);
25833 int swscanf(const wchar_t * restrict s,
25834 const wchar_t * restrict format, ...);
25835 int vfwprintf(FILE * restrict stream,
25836 const wchar_t * restrict format, va_list arg);
25837 int vfwscanf(FILE * restrict stream,
25838 const wchar_t * restrict format, va_list arg);
25839 int vswprintf(wchar_t * restrict s, size_t n,
25840 const wchar_t * restrict format, va_list arg);
25841 int vswscanf(const wchar_t * restrict s,
25842 const wchar_t * restrict format, va_list arg);
25843 int vwprintf(const wchar_t * restrict format,
25845 int vwscanf(const wchar_t * restrict format,
25847 int wprintf(const wchar_t * restrict format, ...);
25848 int wscanf(const wchar_t * restrict format, ...);
25849 wint_t fgetwc(FILE *stream);
25850 wchar_t *fgetws(wchar_t * restrict s, int n,
25851 FILE * restrict stream);
25852 wint_t fputwc(wchar_t c, FILE *stream);
25853 int fputws(const wchar_t * restrict s,
25854 FILE * restrict stream);
25855 int fwide(FILE *stream, int mode);
25856 wint_t getwc(FILE *stream);
25857 wint_t getwchar(void);
25858 wint_t putwc(wchar_t c, FILE *stream);
25859 wint_t putwchar(wchar_t c);
25860 wint_t ungetwc(wint_t c, FILE *stream);
25861 double wcstod(const wchar_t * restrict nptr,
25862 wchar_t ** restrict endptr);
25863 float wcstof(const wchar_t * restrict nptr,
25864 wchar_t ** restrict endptr);
25865 long double wcstold(const wchar_t * restrict nptr,
25866 wchar_t ** restrict endptr);
25867 long int wcstol(const wchar_t * restrict nptr,
25868 wchar_t ** restrict endptr, int base);
25869 long long int wcstoll(const wchar_t * restrict nptr,
25870 wchar_t ** restrict endptr, int base);
25871 unsigned long int wcstoul(const wchar_t * restrict nptr,
25872 wchar_t ** restrict endptr, int base);
25873 unsigned long long int wcstoull(
25874 const wchar_t * restrict nptr,
25875 wchar_t ** restrict endptr, int base);
25876 wchar_t *wcscpy(wchar_t * restrict s1,
25877 const wchar_t * restrict s2);
25878 wchar_t *wcsncpy(wchar_t * restrict s1,
25879 const wchar_t * restrict s2, size_t n);
25880 wchar_t *wmemcpy(wchar_t * restrict s1,
25881 const wchar_t * restrict s2, size_t n);
25882 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
25884 wchar_t *wcscat(wchar_t * restrict s1,
25885 const wchar_t * restrict s2);
25886 wchar_t *wcsncat(wchar_t * restrict s1,
25887 const wchar_t * restrict s2, size_t n);
25888 int wcscmp(const wchar_t *s1, const wchar_t *s2);
25889 int wcscoll(const wchar_t *s1, const wchar_t *s2);
25890 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
25892 size_t wcsxfrm(wchar_t * restrict s1,
25893 const wchar_t * restrict s2, size_t n);
25894 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
25896 wchar_t *wcschr(const wchar_t *s, wchar_t c);
25897 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
25898 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
25899 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
25900 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
25901 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
25902 wchar_t *wcstok(wchar_t * restrict s1,
25903 const wchar_t * restrict s2,
25904 wchar_t ** restrict ptr);
25905 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
25906 size_t wcslen(const wchar_t *s);
25907 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
25908 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
25909 const wchar_t * restrict format,
25910 const struct tm * restrict timeptr);
25911 wint_t btowc(int c);
25912 int wctob(wint_t c);
25913 int mbsinit(const mbstate_t *ps);
25914 size_t mbrlen(const char * restrict s, size_t n,
25915 mbstate_t * restrict ps);
25916 size_t mbrtowc(wchar_t * restrict pwc,
25917 const char * restrict s, size_t n,
25918 mbstate_t * restrict ps);
25919 size_t wcrtomb(char * restrict s, wchar_t wc,
25920 mbstate_t * restrict ps);
25921 size_t mbsrtowcs(wchar_t * restrict dst,
25922 const char ** restrict src, size_t len,
25923 mbstate_t * restrict ps);
25924 size_t wcsrtombs(char * restrict dst,
25925 const wchar_t ** restrict src, size_t len,
25926 mbstate_t * restrict ps);
25927 __STDC_WANT_LIB_EXT1__
25930 int fwprintf_s(FILE * restrict stream,
25931 const wchar_t * restrict format, ...);
25932 int fwscanf_s(FILE * restrict stream,
25933 const wchar_t * restrict format, ...);
25934 int snwprintf_s(wchar_t * restrict s,
25936 const wchar_t * restrict format, ...);
25937 int swprintf_s(wchar_t * restrict s, rsize_t n,
25938 const wchar_t * restrict format, ...);
25939 int swscanf_s(const wchar_t * restrict s,
25940 const wchar_t * restrict format, ...);
25941 int vfwprintf_s(FILE * restrict stream,
25942 const wchar_t * restrict format,
25944 int vfwscanf_s(FILE * restrict stream,
25945 const wchar_t * restrict format, va_list arg);
25946 int vsnwprintf_s(wchar_t * restrict s,
25948 const wchar_t * restrict format,
25950 int vswprintf_s(wchar_t * restrict s,
25952 const wchar_t * restrict format,
25954 int vswscanf_s(const wchar_t * restrict s,
25955 const wchar_t * restrict format,
25957 int vwprintf_s(const wchar_t * restrict format,
25959 int vwscanf_s(const wchar_t * restrict format,
25961 int wprintf_s(const wchar_t * restrict format, ...);
25962 int wscanf_s(const wchar_t * restrict format, ...);
25963 errno_t wcscpy_s(wchar_t * restrict s1,
25965 const wchar_t * restrict s2);
25966 errno_t wcsncpy_s(wchar_t * restrict s1,
25968 const wchar_t * restrict s2,
25970 errno_t wmemcpy_s(wchar_t * restrict s1,
25972 const wchar_t * restrict s2,
25974 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
25975 const wchar_t *s2, rsize_t n);
25976 errno_t wcscat_s(wchar_t * restrict s1,
25978 const wchar_t * restrict s2);
25979 errno_t wcsncat_s(wchar_t * restrict s1,
25981 const wchar_t * restrict s2,
25983 wchar_t *wcstok_s(wchar_t * restrict s1,
25984 rsize_t * restrict s1max,
25985 const wchar_t * restrict s2,
25986 wchar_t ** restrict ptr);
25987 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
25988 errno_t wcrtomb_s(size_t * restrict retval,
25989 char * restrict s, rsize_t smax,
25990 wchar_t wc, mbstate_t * restrict ps);
25991 errno_t mbsrtowcs_s(size_t * restrict retval,
25992 wchar_t * restrict dst, rsize_t dstmax,
25993 const char ** restrict src, rsize_t len,
25994 mbstate_t * restrict ps);
25995 errno_t wcsrtombs_s(size_t * restrict retval,
25996 char * restrict dst, rsize_t dstmax,
25997 const wchar_t ** restrict src, rsize_t len,
25998 mbstate_t * restrict ps);
26001 <p><small><a href="#Contents">Contents</a></small>
26002 <h3><a name="B.29" href="#B.29">B.29 Wide character classification and mapping utilities <wctype.h></a></h3>
26005 wint_t wctrans_t wctype_t WEOF
26006 int iswalnum(wint_t wc);
26007 int iswalpha(wint_t wc);
26008 int iswblank(wint_t wc);
26009 int iswcntrl(wint_t wc);
26010 int iswdigit(wint_t wc);
26011 int iswgraph(wint_t wc);
26012 int iswlower(wint_t wc);
26013 int iswprint(wint_t wc);
26014 int iswpunct(wint_t wc);
26015 int iswspace(wint_t wc);
26016 int iswupper(wint_t wc);
26017 int iswxdigit(wint_t wc);
26018 int iswctype(wint_t wc, wctype_t desc);
26019 wctype_t wctype(const char *property);
26020 wint_t towlower(wint_t wc);
26021 wint_t towupper(wint_t wc);
26022 wint_t towctrans(wint_t wc, wctrans_t desc);
26023 wctrans_t wctrans(const char *property);
26026 <p><small><a href="#Contents">Contents</a></small>
26027 <h2><a name="C" href="#C">Annex C</a></h2>
26032 <p><a name="Cp1" href="#Cp1"><small>1</small></a>
26033 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
26035 <li> Between the evaluations of the function designator and actual arguments in a function
26036 call and the actual call. (<a href="#6.5.2.2">6.5.2.2</a>).
26037 <li> Between the evaluations of the first and second operands of the following operators:
26038 logical AND && (<a href="#6.5.13">6.5.13</a>); logical OR || (<a href="#6.5.14">6.5.14</a>); comma , (<a href="#6.5.17">6.5.17</a>).
26039 <li> Between the evaluations of the first operand of the conditional ? : operator and
26040 whichever of the second and third operands is evaluated (<a href="#6.5.15">6.5.15</a>).
26041 <li> The end of a full declarator: declarators (<a href="#6.7.6">6.7.6</a>);
26042 <li> Between the evaluation of a full expression and the next full expression to be
26043 evaluated. The following are full expressions: an initializer that is not part of a
26044 compound literal (<a href="#6.7.9">6.7.9</a>); the expression in an expression statement (<a href="#6.8.3">6.8.3</a>); the
26045 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
26046 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
26047 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
26048 statement (<a href="#6.8.6.4">6.8.6.4</a>).
26049 <li> Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
26050 <li> After the actions associated with each formatted input/output function conversion
26051 specifier (<a href="#7.21.6">7.21.6</a>, <a href="#7.29.2">7.29.2</a>).
26052 <li> Immediately before and immediately after each call to a comparison function, and
26053 also between any call to a comparison function and any movement of the objects
26054 passed as arguments to that call (<a href="#7.22.5">7.22.5</a>).
26058 <p><small><a href="#Contents">Contents</a></small>
26059 <h2><a name="D" href="#D">Annex D</a></h2>
26062 Universal character names for identifiers
26064 <p><a name="Dp1" href="#Dp1"><small>1</small></a>
26065 This clause lists the hexadecimal code values that are valid in universal character names
26068 <p><small><a href="#Contents">Contents</a></small>
26069 <h3><a name="D.1" href="#D.1">D.1 Ranges of characters allowed</a></h3>
26070 <p><a name="D.1p1" href="#D.1p1"><small>1</small></a>
26071 00A8, 00AA, 00AD, 00AF, 00B2-00B5, 00B7-00BA, 00BC-00BE, 00C0-00D6,
26072 00D8-00F6, 00F8-00FF
26073 <p><a name="D.1p2" href="#D.1p2"><small>2</small></a>
26074 0100-167F, 1681-180D, 180F-1FFF
26075 <p><a name="D.1p3" href="#D.1p3"><small>3</small></a>
26076 200B-200D, 202A-202E, 203F-2040, 2054, 2060-206F
26077 <p><a name="D.1p4" href="#D.1p4"><small>4</small></a>
26078 2070-218F, 2460-24FF, 2776-2793, 2C00-2DFF, 2E80-2FFF
26079 <p><a name="D.1p5" href="#D.1p5"><small>5</small></a>
26080 3004-3007, 3021-302F, 3031-303F
26081 <p><a name="D.1p6" href="#D.1p6"><small>6</small></a>
26083 <p><a name="D.1p7" href="#D.1p7"><small>7</small></a>
26084 F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
26085 <p><a name="D.1p8" href="#D.1p8"><small>8</small></a>
26086 10000-1FFFD, 20000-2FFFD, 30000-3FFFD, 40000-4FFFD, 50000-5FFFD,
26087 60000-6FFFD, 70000-7FFFD, 80000-8FFFD, 90000-9FFFD, A0000-AFFFD,
26088 B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
26090 <p><small><a href="#Contents">Contents</a></small>
26091 <h3><a name="D.2" href="#D.2">D.2 Ranges of characters disallowed initially</a></h3>
26092 <p><a name="D.2p1" href="#D.2p1"><small>1</small></a>
26093 0300-036F, 1DC0-1DFF, 20D0-20FF, FE20-FE2F
26096 <p><small><a href="#Contents">Contents</a></small>
26097 <h2><a name="E" href="#E">Annex E</a></h2>
26100 Implementation limits
26102 <p><a name="Ep1" href="#Ep1"><small>1</small></a>
26103 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
26104 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
26105 with the same sign. The values shall all be constant expressions suitable for use in #if
26106 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
26109 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
26110 #define CHAR_MIN 0 or SCHAR_MIN
26111 #define INT_MAX +32767
26112 #define INT_MIN -32767
26113 #define LONG_MAX +2147483647
26114 #define LONG_MIN -2147483647
26115 #define LLONG_MAX +9223372036854775807
26116 #define LLONG_MIN -9223372036854775807
26117 #define MB_LEN_MAX 1
26118 #define SCHAR_MAX +127
26119 #define SCHAR_MIN -127
26120 #define SHRT_MAX +32767
26121 #define SHRT_MIN -32767
26122 #define UCHAR_MAX 255
26123 #define USHRT_MAX 65535
26124 #define UINT_MAX 65535
26125 #define ULONG_MAX 4294967295
26126 #define ULLONG_MAX 18446744073709551615
26128 <p><a name="Ep2" href="#Ep2"><small>2</small></a>
26129 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
26130 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
26131 directives; all floating values shall be constant expressions. The components are
26132 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
26133 <p><a name="Ep3" href="#Ep3"><small>3</small></a>
26134 The values given in the following list shall be replaced by implementation-defined
26137 #define FLT_EVAL_METHOD
26140 <p><a name="Ep4" href="#Ep4"><small>4</small></a>
26141 The values given in the following list shall be replaced by implementation-defined
26142 constant expressions that are greater or equal in magnitude (absolute value) to those
26143 shown, with the same sign:
26146 #define DLB_DECIMAL_DIG 10
26148 #define DBL_MANT_DIG
26149 #define DBL_MAX_10_EXP +37
26150 #define DBL_MAX_EXP
26151 #define DBL_MIN_10_EXP -37
26152 #define DBL_MIN_EXP
26153 #define DECIMAL_DIG 10
26154 #define FLT_DECIMAL_DIG 6
26156 #define FLT_MANT_DIG
26157 #define FLT_MAX_10_EXP +37
26158 #define FLT_MAX_EXP
26159 #define FLT_MIN_10_EXP -37
26160 #define FLT_MIN_EXP
26161 #define FLT_RADIX 2
26162 #define LDLB_DECIMAL_DIG 10
26163 #define LDBL_DIG 10
26164 #define LDBL_MANT_DIG
26165 #define LDBL_MAX_10_EXP +37
26166 #define LDBL_MAX_EXP
26167 #define LDBL_MIN_10_EXP -37
26168 #define LDBL_MIN_EXP
26170 <p><a name="Ep5" href="#Ep5"><small>5</small></a>
26171 The values given in the following list shall be replaced by implementation-defined
26172 constant expressions with values that are greater than or equal to those shown:
26174 #define DBL_MAX 1E+37
26175 #define FLT_MAX 1E+37
26176 #define LDBL_MAX 1E+37
26178 <p><a name="Ep6" href="#Ep6"><small>6</small></a>
26179 The values given in the following list shall be replaced by implementation-defined
26180 constant expressions with (positive) values that are less than or equal to those shown:
26183 #define DBL_EPSILON 1E-9
26184 #define DBL_MIN 1E-37
26185 #define FLT_EPSILON 1E-5
26186 #define FLT_MIN 1E-37
26187 #define LDBL_EPSILON 1E-9
26188 #define LDBL_MIN 1E-37
26191 <p><small><a href="#Contents">Contents</a></small>
26192 <h2><a name="F" href="#F">Annex F</a></h2>
26195 IEC 60559 floating-point arithmetic
26198 <p><small><a href="#Contents">Contents</a></small>
26199 <h3><a name="F.1" href="#F.1">F.1 Introduction</a></h3>
26200 <p><a name="F.1p1" href="#F.1p1"><small>1</small></a>
26201 This annex specifies C language support for the IEC 60559 floating-point standard. The
26202 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
26203 microprocessor systems, second edition (IEC 60559:1989), previously designated
26204 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
26205 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
26206 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
26207 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
26208 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
26209 defines __STDC_IEC_559__ shall conform to the specifications in this annex.<sup><a href="#note356"><b>356)</b></a></sup>
26210 Where a binding between the C language and IEC 60559 is indicated, the
26211 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
26212 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
26213 within the range of representable values.
26215 <p><b>Footnotes</b>
26216 <p><small><a name="note356" href="#note356">356)</a> Implementations that do not define __STDC_IEC_559__ are not required to conform to these
26220 <p><small><a href="#Contents">Contents</a></small>
26221 <h3><a name="F.2" href="#F.2">F.2 Types</a></h3>
26222 <p><a name="F.2p1" href="#F.2p1"><small>1</small></a>
26223 The C floating types match the IEC 60559 formats as follows:
26225 <li> The float type matches the IEC 60559 single format.
26226 <li> The double type matches the IEC 60559 double format.
26227 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note357"><b>357)</b></a></sup> else a
26228 non-IEC 60559 extended format, else the IEC 60559 double format.
26230 Any non-IEC 60559 extended format used for the long double type shall have more
26231 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note358"><b>358)</b></a></sup>
26237 <p><b>Recommended practice</b>
26238 <p><a name="F.2p2" href="#F.2p2"><small>2</small></a>
26239 The long double type should match an IEC 60559 extended format.
26241 <p><b>Footnotes</b>
26242 <p><small><a name="note357" href="#note357">357)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
26243 and quadruple 128-bit IEC 60559 formats.
26245 <p><small><a name="note358" href="#note358">358)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
26249 <p><small><a href="#Contents">Contents</a></small>
26250 <h4><a name="F.2.1" href="#F.2.1">F.2.1 Infinities, signed zeros, and NaNs</a></h4>
26251 <p><a name="F.2.1p1" href="#F.2.1p1"><small>1</small></a>
26252 This specification does not define the behavior of signaling NaNs.<sup><a href="#note359"><b>359)</b></a></sup> It generally uses
26253 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
26254 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
26256 <p><b>Footnotes</b>
26257 <p><small><a name="note359" href="#note359">359)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
26258 sufficient for closure of the arithmetic.
26261 <p><small><a href="#Contents">Contents</a></small>
26262 <h3><a name="F.3" href="#F.3">F.3 Operators and functions</a></h3>
26263 <p><a name="F.3p1" href="#F.3p1"><small>1</small></a>
26264 C operators and functions provide IEC 60559 required and recommended facilities as
26267 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
26269 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
26270 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
26271 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
26272 with additional information.
26273 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
26274 floating-point number to an integer value (in the same precision). The nearbyint
26275 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
26276 Appendix to ANSI/IEEE 854.
26277 <li> The conversions for floating types provide the IEC 60559 conversions between
26278 floating-point precisions.
26279 <li> The conversions from integer to floating types provide the IEC 60559 conversions
26280 from integer to floating point.
26281 <li> The conversions from floating to integer types provide IEC 60559-like conversions
26282 but always round toward zero.
26283 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
26284 conversions, which honor the directed rounding mode, from floating point to the
26285 long int and long long int integer formats. The lrint and llrint
26286 functions can be used to implement IEC 60559 conversions from floating to other
26288 <li> The translation time conversion of floating constants and the strtod, strtof,
26289 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
26293 <a href="#7.21"><stdio.h></a>, and <a href="#7.29"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
26294 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
26295 Appendix to ANSI/IEEE 854.
26296 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
26297 identifies a need for additional comparison predicates to facilitate writing code that
26298 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
26299 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
26300 supplement the language operators to address this need. The islessgreater and
26301 isunordered macros provide respectively a quiet version of the <> predicate and
26302 the unordered predicate recommended in the Appendix to IEC 60559.
26303 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
26304 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
26305 exception status flags. The fegetexceptflag and fesetexceptflag
26306 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
26307 one time. These functions are used in conjunction with the type fexcept_t and the
26308 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
26309 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
26310 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
26311 to select among the IEC 60559 directed rounding modes represented by the rounding
26312 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
26313 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
26314 IEC 60559 directed rounding modes.
26315 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
26316 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
26317 the IEC 60559 status flags and control modes.
26318 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
26319 recommended in the Appendix to IEC 60559.
26320 <li> The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
26321 Appendix to IEC 60559.
26322 <li> The unary minus (-) operator provides the unary minus (-) operation recommended
26323 in the Appendix to IEC 60559.
26324 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
26325 recommended in the Appendix to IEC 60559.
26326 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
26327 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
26328 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
26329 function recommended in the Appendix to IEC 60559 (but with a minor change to
26331 better handle signed zeros).
26332 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
26333 the Appendix to IEC 60559.
26334 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
26335 Appendix to IEC 60559.
26336 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
26337 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
26338 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
26339 function recommended in the Appendix to IEC 60559 (except that the classification
26340 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
26343 <p><small><a href="#Contents">Contents</a></small>
26344 <h3><a name="F.4" href="#F.4">F.4 Floating to integer conversion</a></h3>
26345 <p><a name="F.4p1" href="#F.4p1"><small>1</small></a>
26346 If the integer type is _Bool, <a href="#6.3.1.2">6.3.1.2</a> applies and no floating-point exceptions are raised
26347 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
26348 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
26349 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
26350 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
26351 exceed the range of the integer type raises no floating-point exceptions; whether
26352 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
26353 unspecified.<sup><a href="#note360"><b>360)</b></a></sup>
26355 <p><b>Footnotes</b>
26356 <p><small><a name="note360" href="#note360">360)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
26357 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
26358 cases where it matters, library functions can be used to effect such conversions with or without raising
26359 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
26360 <a href="#7.12"><math.h></a>.
26363 <p><small><a href="#Contents">Contents</a></small>
26364 <h3><a name="F.5" href="#F.5">F.5 Binary-decimal conversion</a></h3>
26365 <p><a name="F.5p1" href="#F.5p1"><small>1</small></a>
26366 Conversion from the widest supported IEC 60559 format to decimal with
26367 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note361"><b>361)</b></a></sup>
26368 <p><a name="F.5p2" href="#F.5p2"><small>2</small></a>
26369 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
26370 particular, conversion between any supported IEC 60559 format and decimal with
26371 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
26372 rounding mode), which assures that conversion from the widest supported IEC 60559
26373 format to decimal with DECIMAL_DIG digits and back is the identity function.
26378 <p><a name="F.5p3" href="#F.5p3"><small>3</small></a>
26379 Functions such as strtod that convert character sequences to floating types honor the
26380 rounding direction. Hence, if the rounding direction might be upward or downward, the
26381 implementation cannot convert a minus-signed sequence by negating the converted
26384 <p><b>Footnotes</b>
26385 <p><small><a name="note361" href="#note361">361)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
26386 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
26387 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
26388 DBL_DIG are 18 and 15, respectively, for these formats.)
26391 <p><small><a href="#Contents">Contents</a></small>
26392 <h3><a name="F.6" href="#F.6">F.6 The return statement</a></h3>
26393 If the return expression is evaluated in a floating-point format different from the return
26394 type, the expression is converted as if by assignment<sup><a href="#note362"><b>362)</b></a></sup> to the return type of the function
26395 and the resulting value is returned to the caller.
26397 <p><b>Footnotes</b>
26398 <p><small><a name="note362" href="#note362">362)</a> Assignment removes any extra range and precision.
26401 <p><small><a href="#Contents">Contents</a></small>
26402 <h3><a name="F.7" href="#F.7">F.7 Contracted expressions</a></h3>
26403 <p><a name="F.7p1" href="#F.7p1"><small>1</small></a>
26404 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
26405 zeros, subnormals, and the rounding directions in a manner consistent with the basic
26406 arithmetic operations covered by IEC 60559.
26407 <p><b>Recommended practice</b>
26408 <p><a name="F.7p2" href="#F.7p2"><small>2</small></a>
26409 A contracted expression should raise floating-point exceptions in a manner generally
26410 consistent with the basic arithmetic operations.
26412 <p><small><a href="#Contents">Contents</a></small>
26413 <h3><a name="F.8" href="#F.8">F.8 Floating-point environment</a></h3>
26414 <p><a name="F.8p1" href="#F.8p1"><small>1</small></a>
26415 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
26416 point exception status flags and directed-rounding control modes. It includes also
26417 IEC 60559 dynamic rounding precision and trap enablement modes, if the
26418 implementation supports them.<sup><a href="#note363"><b>363)</b></a></sup>
26420 <p><b>Footnotes</b>
26421 <p><small><a name="note363" href="#note363">363)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
26424 <p><small><a href="#Contents">Contents</a></small>
26425 <h4><a name="F.8.1" href="#F.8.1">F.8.1 Environment management</a></h4>
26426 <p><a name="F.8.1p1" href="#F.8.1p1"><small>1</small></a>
26427 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
26428 status flags, and that rounding control modes can be set explicitly to affect result values of
26429 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
26430 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
26431 which respect sequence points.<sup><a href="#note364"><b>364)</b></a></sup>
26438 <p><b>Footnotes</b>
26439 <p><small><a name="note364" href="#note364">364)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
26440 point control modes will be the default ones and the floating-point status flags will not be tested,
26441 which allows certain optimizations (see <a href="#F.9">F.9</a>).
26444 <p><small><a href="#Contents">Contents</a></small>
26445 <h4><a name="F.8.2" href="#F.8.2">F.8.2 Translation</a></h4>
26446 <p><a name="F.8.2p1" href="#F.8.2p1"><small>1</small></a>
26447 During translation the IEC 60559 default modes are in effect:
26449 <li> The rounding direction mode is rounding to nearest.
26450 <li> The rounding precision mode (if supported) is set so that results are not shortened.
26451 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
26453 <p><b>Recommended practice</b>
26454 <p><a name="F.8.2p2" href="#F.8.2p2"><small>2</small></a>
26455 The implementation should produce a diagnostic message for each translation-time
26456 floating-point exception, other than ''inexact'';<sup><a href="#note365"><b>365)</b></a></sup> the implementation should then
26457 proceed with the translation of the program.
26459 <p><b>Footnotes</b>
26460 <p><small><a name="note365" href="#note365">365)</a> As floating constants are converted to appropriate internal representations at translation time, their
26461 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
26462 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
26463 strtod, provide execution-time conversion of numeric strings.
26466 <p><small><a href="#Contents">Contents</a></small>
26467 <h4><a name="F.8.3" href="#F.8.3">F.8.3 Execution</a></h4>
26468 <p><a name="F.8.3p1" href="#F.8.3p1"><small>1</small></a>
26469 At program startup the floating-point environment is initialized as prescribed by
26472 <li> All floating-point exception status flags are cleared.
26473 <li> The rounding direction mode is rounding to nearest.
26474 <li> The dynamic rounding precision mode (if supported) is set so that results are not
26476 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
26479 <p><small><a href="#Contents">Contents</a></small>
26480 <h4><a name="F.8.4" href="#F.8.4">F.8.4 Constant expressions</a></h4>
26481 <p><a name="F.8.4p1" href="#F.8.4p1"><small>1</small></a>
26482 An arithmetic constant expression of floating type, other than one in an initializer for an
26483 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
26484 it is affected by any operative floating-point control modes and raises floating-point
26485 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
26486 is ''on'').<sup><a href="#note366"><b>366)</b></a></sup>
26487 <p><a name="F.8.4p2" href="#F.8.4p2"><small>2</small></a>
26494 #include <a href="#7.6"><fenv.h></a>
26495 #pragma STDC FENV_ACCESS ON
26498 float w[] = { 0.0/0.0 }; // raises an exception
26499 static float x = 0.0/0.0; // does not raise an exception
26500 float y = 0.0/0.0; // raises an exception
26501 double z = 0.0/0.0; // raises an exception
26505 <p><a name="F.8.4p3" href="#F.8.4p3"><small>3</small></a>
26506 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
26507 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
26511 <p><b>Footnotes</b>
26512 <p><small><a name="note366" href="#note366">366)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
26513 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
26514 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
26515 efficiency of translation-time evaluation through static initialization, such as
26518 const static double one_third = 1.0/3.0;
26522 <p><small><a href="#Contents">Contents</a></small>
26523 <h4><a name="F.8.5" href="#F.8.5">F.8.5 Initialization</a></h4>
26524 <p><a name="F.8.5p1" href="#F.8.5p1"><small>1</small></a>
26525 All computation for automatic initialization is done (as if) at execution time; thus, it is
26526 affected by any operative modes and raises floating-point exceptions as required by
26527 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
26528 for initialization of objects that have static or thread storage duration is done (as if) at
26530 <p><a name="F.8.5p2" href="#F.8.5p2"><small>2</small></a>
26533 #include <a href="#7.6"><fenv.h></a>
26534 #pragma STDC FENV_ACCESS ON
26537 float u[] = { 1.1e75 }; // raises exceptions
26538 static float v = 1.1e75; // does not raise exceptions
26539 float w = 1.1e75; // raises exceptions
26540 double x = 1.1e75; // may raise exceptions
26541 float y = 1.1e75f; // may raise exceptions
26542 long double z = 1.1e75; // does not raise exceptions
26546 <p><a name="F.8.5p3" href="#F.8.5p3"><small>3</small></a>
26547 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
26548 done at translation time. The automatic initialization of u and w require an execution-time conversion to
26549 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
26550 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
26551 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note367"><b>367)</b></a></sup> The
26552 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
26553 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
26558 their internal representations occur at translation time in all cases.
26561 <p><b>Footnotes</b>
26562 <p><small><a name="note367" href="#note367">367)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
26563 For example, the automatic initialization
26566 double_t x = 1.1e75;
26568 could be done at translation time, regardless of the expression evaluation method.
26571 <p><small><a href="#Contents">Contents</a></small>
26572 <h4><a name="F.8.6" href="#F.8.6">F.8.6 Changing the environment</a></h4>
26573 <p><a name="F.8.6p1" href="#F.8.6p1"><small>1</small></a>
26574 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
26575 change floating-point status flags and control modes just as indicated by their
26576 specifications (including conformance to IEC 60559). They do not change flags or modes
26577 (so as to be detectable by the user) in any other cases.
26578 <p><a name="F.8.6p2" href="#F.8.6p2"><small>2</small></a>
26579 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
26580 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
26581 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
26582 before ''inexact''.
26584 <p><small><a href="#Contents">Contents</a></small>
26585 <h3><a name="F.9" href="#F.9">F.9 Optimization</a></h3>
26586 <p><a name="F.9p1" href="#F.9p1"><small>1</small></a>
26587 This section identifies code transformations that might subvert IEC 60559-specified
26588 behavior, and others that do not.
26590 <p><small><a href="#Contents">Contents</a></small>
26591 <h4><a name="F.9.1" href="#F.9.1">F.9.1 Global transformations</a></h4>
26592 <p><a name="F.9.1p1" href="#F.9.1p1"><small>1</small></a>
26593 Floating-point arithmetic operations and external function calls may entail side effects
26594 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
26595 ''on''. The flags and modes in the floating-point environment may be regarded as global
26596 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
26598 <p><a name="F.9.1p2" href="#F.9.1p2"><small>2</small></a>
26599 Concern about side effects may inhibit code motion and removal of seemingly useless
26600 code. For example, in
26602 #include <a href="#7.6"><fenv.h></a>
26603 #pragma STDC FENV_ACCESS ON
26607 for (i = 0; i < n; i++) x + 1;
26611 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
26612 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
26613 course these optimizations are valid if the implementation can rule out the nettlesome
26615 <p><a name="F.9.1p3" href="#F.9.1p3"><small>3</small></a>
26616 This specification does not require support for trap handlers that maintain information
26617 about the order or count of floating-point exceptions. Therefore, between function calls,
26618 floating-point exceptions need not be precise: the actual order and number of occurrences
26619 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
26621 the preceding loop could be treated as
26623 if (0 < n) x + 1;
26626 <p><small><a href="#Contents">Contents</a></small>
26627 <h4><a name="F.9.2" href="#F.9.2">F.9.2 Expression transformations</a></h4>
26628 <p><a name="F.9.2p1" href="#F.9.2p1"><small>1</small></a>
26629 x/2 <-> x x 0.5 Although similar transformations involving inexact constants
26631 generally do not yield numerically equivalent expressions, if the
26632 constants are exact then such transformations can be made on
26633 IEC 60559 machines and others that round perfectly.
26635 1 x x and x/1 -> x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
26637 machines, among others).<sup><a href="#note368"><b>368)</b></a></sup>
26639 x/x -> 1.0 The expressions x/x and 1.0 are not equivalent if x can be zero,
26643 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
26645 IEC 60559 machines, among others).
26647 x - y <-> -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
26649 is +0 but -(1 - 1) is -0 (in the default rounding direction).<sup><a href="#note369"><b>369)</b></a></sup>
26651 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
26655 0 x x -> 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
26659 x+0-> x The expressions x + 0 and x are not equivalent if x is -0, because
26661 (-0) + (+0) yields +0 (in the default rounding direction), not -0.
26663 x-0-> x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
26665 +0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
26666 FENV_ACCESS pragma is ''off'', promising default rounding, then
26667 the implementation can replace x - 0 by x, even if x might be zero.
26669 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
26671 -(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
26677 <p><b>Footnotes</b>
26678 <p><small><a name="note368" href="#note368">368)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
26679 other transformations that remove arithmetic operators.
26681 <p><small><a name="note369" href="#note369">369)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
26685 1/(1/ (+-) (inf)) is (+-) (inf)
26690 conj(csqrt(z)) is csqrt(conj(z)),
26695 <p><small><a href="#Contents">Contents</a></small>
26696 <h4><a name="F.9.3" href="#F.9.3">F.9.3 Relational operators</a></h4>
26697 <p><a name="F.9.3p1" href="#F.9.3p1"><small>1</small></a>
26698 x != x -> false The expression x != x is true if x is a NaN.
26699 x = x -> true The expression x = x is false if x is a NaN.
26700 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
26702 expressions are not equivalent because of side effects when x or y is a
26703 NaN and the state of the FENV_ACCESS pragma is ''on''. This
26704 transformation, which would be desirable if extra code were required
26705 to cause the ''invalid'' floating-point exception for unordered cases,
26706 could be performed provided the state of the FENV_ACCESS pragma
26709 The sense of relational operators shall be maintained. This includes handling unordered
26710 cases as expressed by the source code.
26711 <p><a name="F.9.3p2" href="#F.9.3p2"><small>2</small></a>
26714 // calls g and raises ''invalid'' if a and b are unordered
26720 is not equivalent to
26722 // calls f and raises ''invalid'' if a and b are unordered
26730 // calls f without raising ''invalid'' if a and b are unordered
26731 if (isgreaterequal(a,b))
26736 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
26738 // calls g without raising ''invalid'' if a and b are unordered
26744 but is equivalent to
26754 <p><small><a href="#Contents">Contents</a></small>
26755 <h4><a name="F.9.4" href="#F.9.4">F.9.4 Constant arithmetic</a></h4>
26756 <p><a name="F.9.4p1" href="#F.9.4p1"><small>1</small></a>
26757 The implementation shall honor floating-point exceptions raised by execution-time
26758 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
26759 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
26760 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
26761 further check is required to assure that changing the rounding direction to downward does
26762 not alter the sign of the result,<sup><a href="#note370"><b>370)</b></a></sup> and implementations that support dynamic rounding
26763 precision modes shall assure further that the result of the operation raises no floating-
26764 point exception when converted to the semantic type of the operation.
26766 <p><b>Footnotes</b>
26767 <p><small><a name="note370" href="#note370">370)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
26770 <p><small><a href="#Contents">Contents</a></small>
26771 <h3><a name="F.10" href="#F.10">F.10 Mathematics <math.h></a></h3>
26772 <p><a name="F.10p1" href="#F.10p1"><small>1</small></a>
26773 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
26774 for IEC 60559 implementations.
26775 <p><a name="F.10p2" href="#F.10p2"><small>2</small></a>
26776 The Standard C macro HUGE_VAL and its float and long double analogs,
26777 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
26779 <p><a name="F.10p3" href="#F.10p3"><small>3</small></a>
26780 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
26781 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
26782 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
26783 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
26784 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
26785 <p><a name="F.10p4" href="#F.10p4"><small>4</small></a>
26786 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
26788 <p><a name="F.10p5" href="#F.10p5"><small>5</small></a>
26789 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
26790 subsequent subclauses of this annex.
26791 <p><a name="F.10p6" href="#F.10p6"><small>6</small></a>
26792 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
26793 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
26794 whose magnitude is too large.
26795 <p><a name="F.10p7" href="#F.10p7"><small>7</small></a>
26796 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
26797 subnormal or zero) and suffers loss of accuracy.<sup><a href="#note371"><b>371)</b></a></sup>
26801 <p><a name="F.10p8" href="#F.10p8"><small>8</small></a>
26802 Whether or when library functions raise the ''inexact'' floating-point exception is
26803 unspecified, unless explicitly specified otherwise.
26804 <p><a name="F.10p9" href="#F.10p9"><small>9</small></a>
26805 Whether or when library functions raise an undeserved ''underflow'' floating-point
26806 exception is unspecified.<sup><a href="#note372"><b>372)</b></a></sup> Otherwise, as implied by <a href="#F.8.6">F.8.6</a>, the <a href="#7.12"><math.h></a> functions do
26807 not raise spurious floating-point exceptions (detectable by the user), other than the
26808 ''inexact'' floating-point exception.
26809 <p><a name="F.10p10" href="#F.10p10"><small>10</small></a>
26810 Whether the functions honor the rounding direction mode is implementation-defined,
26811 unless explicitly specified otherwise.
26812 <p><a name="F.10p11" href="#F.10p11"><small>11</small></a>
26813 Functions with a NaN argument return a NaN result and raise no floating-point exception,
26814 except where stated otherwise.
26815 <p><a name="F.10p12" href="#F.10p12"><small>12</small></a>
26816 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
26817 For families of functions, the specifications apply to all of the functions even though only
26818 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
26819 occurs in both an argument and the result, the result has the same sign as the argument.
26820 <p><b>Recommended practice</b>
26821 <p><a name="F.10p13" href="#F.10p13"><small>13</small></a>
26822 If a function with one or more NaN arguments returns a NaN result, the result should be
26823 the same as one of the NaN arguments (after possible type conversion), except perhaps
26826 <p><b>Footnotes</b>
26827 <p><small><a name="note371" href="#note371">371)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
26828 when the floating-point exception is raised.
26830 <p><small><a name="note372" href="#note372">372)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
26831 avoiding them would be too costly.
26834 <p><small><a href="#Contents">Contents</a></small>
26835 <h4><a name="F.10.1" href="#F.10.1">F.10.1 Trigonometric functions</a></h4>
26837 <p><small><a href="#Contents">Contents</a></small>
26838 <h5><a name="F.10.1.1" href="#F.10.1.1">F.10.1.1 The acos functions</a></h5>
26839 <p><a name="F.10.1.1p1" href="#F.10.1.1p1"><small>1</small></a>
26841 <li> acos(1) returns +0.
26842 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
26846 <p><small><a href="#Contents">Contents</a></small>
26847 <h5><a name="F.10.1.2" href="#F.10.1.2">F.10.1.2 The asin functions</a></h5>
26848 <p><a name="F.10.1.2p1" href="#F.10.1.2p1"><small>1</small></a>
26850 <li> asin((+-)0) returns (+-)0.
26851 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
26860 <p><small><a href="#Contents">Contents</a></small>
26861 <h5><a name="F.10.1.3" href="#F.10.1.3">F.10.1.3 The atan functions</a></h5>
26862 <p><a name="F.10.1.3p1" href="#F.10.1.3p1"><small>1</small></a>
26864 <li> atan((+-)0) returns (+-)0.
26865 <li> atan((+-)(inf)) returns (+-)pi /2.
26868 <p><small><a href="#Contents">Contents</a></small>
26869 <h5><a name="F.10.1.4" href="#F.10.1.4">F.10.1.4 The atan2 functions</a></h5>
26870 <p><a name="F.10.1.4p1" href="#F.10.1.4p1"><small>1</small></a>
26872 <li> atan2((+-)0, -0) returns (+-)pi .<sup><a href="#note373"><b>373)</b></a></sup>
26873 <li> atan2((+-)0, +0) returns (+-)0.
26874 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
26875 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
26876 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
26877 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
26878 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
26879 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
26880 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
26881 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
26882 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
26885 <p><b>Footnotes</b>
26886 <p><small><a name="note373" href="#note373">373)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
26887 the ''divide-by-zero'' floating-point exception.
26890 <p><small><a href="#Contents">Contents</a></small>
26891 <h5><a name="F.10.1.5" href="#F.10.1.5">F.10.1.5 The cos functions</a></h5>
26892 <p><a name="F.10.1.5p1" href="#F.10.1.5p1"><small>1</small></a>
26894 <li> cos((+-)0) returns 1.
26895 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26898 <p><small><a href="#Contents">Contents</a></small>
26899 <h5><a name="F.10.1.6" href="#F.10.1.6">F.10.1.6 The sin functions</a></h5>
26900 <p><a name="F.10.1.6p1" href="#F.10.1.6p1"><small>1</small></a>
26902 <li> sin((+-)0) returns (+-)0.
26903 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26906 <p><small><a href="#Contents">Contents</a></small>
26907 <h5><a name="F.10.1.7" href="#F.10.1.7">F.10.1.7 The tan functions</a></h5>
26908 <p><a name="F.10.1.7p1" href="#F.10.1.7p1"><small>1</small></a>
26910 <li> tan((+-)0) returns (+-)0.
26911 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26919 <p><small><a href="#Contents">Contents</a></small>
26920 <h4><a name="F.10.2" href="#F.10.2">F.10.2 Hyperbolic functions</a></h4>
26922 <p><small><a href="#Contents">Contents</a></small>
26923 <h5><a name="F.10.2.1" href="#F.10.2.1">F.10.2.1 The acosh functions</a></h5>
26924 <p><a name="F.10.2.1p1" href="#F.10.2.1p1"><small>1</small></a>
26926 <li> acosh(1) returns +0.
26927 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
26928 <li> acosh(+(inf)) returns +(inf).
26931 <p><small><a href="#Contents">Contents</a></small>
26932 <h5><a name="F.10.2.2" href="#F.10.2.2">F.10.2.2 The asinh functions</a></h5>
26933 <p><a name="F.10.2.2p1" href="#F.10.2.2p1"><small>1</small></a>
26935 <li> asinh((+-)0) returns (+-)0.
26936 <li> asinh((+-)(inf)) returns (+-)(inf).
26939 <p><small><a href="#Contents">Contents</a></small>
26940 <h5><a name="F.10.2.3" href="#F.10.2.3">F.10.2.3 The atanh functions</a></h5>
26941 <p><a name="F.10.2.3p1" href="#F.10.2.3p1"><small>1</small></a>
26943 <li> atanh((+-)0) returns (+-)0.
26944 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
26945 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
26949 <p><small><a href="#Contents">Contents</a></small>
26950 <h5><a name="F.10.2.4" href="#F.10.2.4">F.10.2.4 The cosh functions</a></h5>
26951 <p><a name="F.10.2.4p1" href="#F.10.2.4p1"><small>1</small></a>
26953 <li> cosh((+-)0) returns 1.
26954 <li> cosh((+-)(inf)) returns +(inf).
26957 <p><small><a href="#Contents">Contents</a></small>
26958 <h5><a name="F.10.2.5" href="#F.10.2.5">F.10.2.5 The sinh functions</a></h5>
26959 <p><a name="F.10.2.5p1" href="#F.10.2.5p1"><small>1</small></a>
26961 <li> sinh((+-)0) returns (+-)0.
26962 <li> sinh((+-)(inf)) returns (+-)(inf).
26965 <p><small><a href="#Contents">Contents</a></small>
26966 <h5><a name="F.10.2.6" href="#F.10.2.6">F.10.2.6 The tanh functions</a></h5>
26967 <p><a name="F.10.2.6p1" href="#F.10.2.6p1"><small>1</small></a>
26969 <li> tanh((+-)0) returns (+-)0.
26970 <li> tanh((+-)(inf)) returns (+-)1.
26973 <p><small><a href="#Contents">Contents</a></small>
26974 <h4><a name="F.10.3" href="#F.10.3">F.10.3 Exponential and logarithmic functions</a></h4>
26976 <p><small><a href="#Contents">Contents</a></small>
26977 <h5><a name="F.10.3.1" href="#F.10.3.1">F.10.3.1 The exp functions</a></h5>
26978 <p><a name="F.10.3.1p1" href="#F.10.3.1p1"><small>1</small></a>
26980 <li> exp((+-)0) returns 1.
26981 <li> exp(-(inf)) returns +0.
26982 <li> exp(+(inf)) returns +(inf).
26986 <p><small><a href="#Contents">Contents</a></small>
26987 <h5><a name="F.10.3.2" href="#F.10.3.2">F.10.3.2 The exp2 functions</a></h5>
26988 <p><a name="F.10.3.2p1" href="#F.10.3.2p1"><small>1</small></a>
26990 <li> exp2((+-)0) returns 1.
26991 <li> exp2(-(inf)) returns +0.
26992 <li> exp2(+(inf)) returns +(inf).
26995 <p><small><a href="#Contents">Contents</a></small>
26996 <h5><a name="F.10.3.3" href="#F.10.3.3">F.10.3.3 The expm1 functions</a></h5>
26997 <p><a name="F.10.3.3p1" href="#F.10.3.3p1"><small>1</small></a>
26999 <li> expm1((+-)0) returns (+-)0.
27000 <li> expm1(-(inf)) returns -1.
27001 <li> expm1(+(inf)) returns +(inf).
27004 <p><small><a href="#Contents">Contents</a></small>
27005 <h5><a name="F.10.3.4" href="#F.10.3.4">F.10.3.4 The frexp functions</a></h5>
27006 <p><a name="F.10.3.4p1" href="#F.10.3.4p1"><small>1</small></a>
27008 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
27009 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
27011 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
27012 (and returns a NaN).
27014 <p><a name="F.10.3.4p2" href="#F.10.3.4p2"><small>2</small></a>
27015 frexp raises no floating-point exceptions.
27016 <p><a name="F.10.3.4p3" href="#F.10.3.4p3"><small>3</small></a>
27017 When the radix of the argument is a power of 2, the returned value is exact and is
27018 independent of the current rounding direction mode.
27019 <p><a name="F.10.3.4p4" href="#F.10.3.4p4"><small>4</small></a>
27020 On a binary system, the body of the frexp function might be
27023 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
27024 return scalbn(value, -(*exp));
27028 <p><small><a href="#Contents">Contents</a></small>
27029 <h5><a name="F.10.3.5" href="#F.10.3.5">F.10.3.5 The ilogb functions</a></h5>
27030 <p><a name="F.10.3.5p1" href="#F.10.3.5p1"><small>1</small></a>
27031 When the correct result is representable in the range of the return type, the returned value
27032 is exact and is independent of the current rounding direction mode.
27033 <p><a name="F.10.3.5p2" href="#F.10.3.5p2"><small>2</small></a>
27034 If the correct result is outside the range of the return type, the numeric result is
27035 unspecified and the ''invalid'' floating-point exception is raised.
27036 <p><a name="F.10.3.5p3" href="#F.10.3.5p3"><small>3</small></a>
27037 ilogb(x), for x zero, infinite, or NaN, raises the ''invalid'' floating-point exception and
27038 returns the value specified in <a href="#7.12.6.5">7.12.6.5</a>.
27041 <p><small><a href="#Contents">Contents</a></small>
27042 <h5><a name="F.10.3.6" href="#F.10.3.6">F.10.3.6 The ldexp functions</a></h5>
27043 <p><a name="F.10.3.6p1" href="#F.10.3.6p1"><small>1</small></a>
27044 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
27046 <p><small><a href="#Contents">Contents</a></small>
27047 <h5><a name="F.10.3.7" href="#F.10.3.7">F.10.3.7 The log functions</a></h5>
27048 <p><a name="F.10.3.7p1" href="#F.10.3.7p1"><small>1</small></a>
27050 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
27051 <li> log(1) returns +0.
27052 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
27053 <li> log(+(inf)) returns +(inf).
27056 <p><small><a href="#Contents">Contents</a></small>
27057 <h5><a name="F.10.3.8" href="#F.10.3.8">F.10.3.8 The log10 functions</a></h5>
27058 <p><a name="F.10.3.8p1" href="#F.10.3.8p1"><small>1</small></a>
27060 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
27061 <li> log10(1) returns +0.
27062 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
27063 <li> log10(+(inf)) returns +(inf).
27066 <p><small><a href="#Contents">Contents</a></small>
27067 <h5><a name="F.10.3.9" href="#F.10.3.9">F.10.3.9 The log1p functions</a></h5>
27068 <p><a name="F.10.3.9p1" href="#F.10.3.9p1"><small>1</small></a>
27070 <li> log1p((+-)0) returns (+-)0.
27071 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
27072 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
27074 <li> log1p(+(inf)) returns +(inf).
27077 <p><small><a href="#Contents">Contents</a></small>
27078 <h5><a name="F.10.3.10" href="#F.10.3.10">F.10.3.10 The log2 functions</a></h5>
27079 <p><a name="F.10.3.10p1" href="#F.10.3.10p1"><small>1</small></a>
27081 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
27082 <li> log2(1) returns +0.
27083 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
27084 <li> log2(+(inf)) returns +(inf).
27087 <p><small><a href="#Contents">Contents</a></small>
27088 <h5><a name="F.10.3.11" href="#F.10.3.11">F.10.3.11 The logb functions</a></h5>
27089 <p><a name="F.10.3.11p1" href="#F.10.3.11p1"><small>1</small></a>
27091 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
27092 <li> logb((+-)(inf)) returns +(inf).
27094 <p><a name="F.10.3.11p2" href="#F.10.3.11p2"><small>2</small></a>
27095 The returned value is exact and is independent of the current rounding direction mode.
27098 <p><small><a href="#Contents">Contents</a></small>
27099 <h5><a name="F.10.3.12" href="#F.10.3.12">F.10.3.12 The modf functions</a></h5>
27100 <p><a name="F.10.3.12p1" href="#F.10.3.12p1"><small>1</small></a>
27102 <li> modf((+-)x, iptr) returns a result with the same sign as x.
27103 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
27104 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
27107 <p><a name="F.10.3.12p2" href="#F.10.3.12p2"><small>2</small></a>
27108 The returned values are exact and are independent of the current rounding direction
27110 <p><a name="F.10.3.12p3" href="#F.10.3.12p3"><small>3</small></a>
27111 modf behaves as though implemented by
27113 #include <a href="#7.12"><math.h></a>
27114 #include <a href="#7.6"><fenv.h></a>
27115 #pragma STDC FENV_ACCESS ON
27116 double modf(double value, double *iptr)
27118 int save_round = fegetround();
27119 fesetround(FE_TOWARDZERO);
27120 *iptr = nearbyint(value);
27121 fesetround(save_round);
27123 isinf(value) ? 0.0 :
27124 value - (*iptr), value);
27128 <p><small><a href="#Contents">Contents</a></small>
27129 <h5><a name="F.10.3.13" href="#F.10.3.13">F.10.3.13 The scalbn and scalbln functions</a></h5>
27130 <p><a name="F.10.3.13p1" href="#F.10.3.13p1"><small>1</small></a>
27132 <li> scalbn((+-)0, n) returns (+-)0.
27133 <li> scalbn(x, 0) returns x.
27134 <li> scalbn((+-)(inf), n) returns (+-)(inf).
27136 <p><a name="F.10.3.13p2" href="#F.10.3.13p2"><small>2</small></a>
27137 If the calculation does not overflow or underflow, the returned value is exact and
27138 independent of the current rounding direction mode.
27141 <p><small><a href="#Contents">Contents</a></small>
27142 <h4><a name="F.10.4" href="#F.10.4">F.10.4 Power and absolute value functions</a></h4>
27144 <p><small><a href="#Contents">Contents</a></small>
27145 <h5><a name="F.10.4.1" href="#F.10.4.1">F.10.4.1 The cbrt functions</a></h5>
27146 <p><a name="F.10.4.1p1" href="#F.10.4.1p1"><small>1</small></a>
27148 <li> cbrt((+-)0) returns (+-)0.
27149 <li> cbrt((+-)(inf)) returns (+-)(inf).
27152 <p><small><a href="#Contents">Contents</a></small>
27153 <h5><a name="F.10.4.2" href="#F.10.4.2">F.10.4.2 The fabs functions</a></h5>
27154 <p><a name="F.10.4.2p1" href="#F.10.4.2p1"><small>1</small></a>
27156 <li> fabs((+-)0) returns +0.
27157 <li> fabs((+-)(inf)) returns +(inf).
27159 <p><a name="F.10.4.2p2" href="#F.10.4.2p2"><small>2</small></a>
27160 The returned value is exact and is independent of the current rounding direction mode.
27162 <p><small><a href="#Contents">Contents</a></small>
27163 <h5><a name="F.10.4.3" href="#F.10.4.3">F.10.4.3 The hypot functions</a></h5>
27164 <p><a name="F.10.4.3p1" href="#F.10.4.3p1"><small>1</small></a>
27166 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
27167 <li> hypot(x, (+-)0) is equivalent to fabs(x).
27168 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
27171 <p><small><a href="#Contents">Contents</a></small>
27172 <h5><a name="F.10.4.4" href="#F.10.4.4">F.10.4.4 The pow functions</a></h5>
27173 <p><a name="F.10.4.4p1" href="#F.10.4.4p1"><small>1</small></a>
27175 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
27176 for y an odd integer < 0.
27177 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
27178 for y < 0, finite, and not an odd integer.
27179 <li> pow((+-)0, -(inf)) returns +(inf) and may raise the ''divide-by-zero'' floating-point
27181 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
27182 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
27183 <li> pow(-1, (+-)(inf)) returns 1.
27184 <li> pow(+1, y) returns 1 for any y, even a NaN.
27185 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
27186 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
27187 finite x < 0 and finite non-integer y.
27188 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
27189 <li> pow(x, -(inf)) returns +0 for | x | > 1.
27190 <li> pow(x, +(inf)) returns +0 for | x | < 1.
27191 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
27193 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
27194 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
27195 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
27196 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
27197 <li> pow(+(inf), y) returns +0 for y < 0.
27198 <li> pow(+(inf), y) returns +(inf) for y > 0.
27201 <p><small><a href="#Contents">Contents</a></small>
27202 <h5><a name="F.10.4.5" href="#F.10.4.5">F.10.4.5 The sqrt functions</a></h5>
27203 <p><a name="F.10.4.5p1" href="#F.10.4.5p1"><small>1</small></a>
27204 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
27205 is dependent on the current rounding direction mode.
27207 <p><small><a href="#Contents">Contents</a></small>
27208 <h4><a name="F.10.5" href="#F.10.5">F.10.5 Error and gamma functions</a></h4>
27210 <p><small><a href="#Contents">Contents</a></small>
27211 <h5><a name="F.10.5.1" href="#F.10.5.1">F.10.5.1 The erf functions</a></h5>
27212 <p><a name="F.10.5.1p1" href="#F.10.5.1p1"><small>1</small></a>
27214 <li> erf((+-)0) returns (+-)0.
27215 <li> erf((+-)(inf)) returns (+-)1.
27218 <p><small><a href="#Contents">Contents</a></small>
27219 <h5><a name="F.10.5.2" href="#F.10.5.2">F.10.5.2 The erfc functions</a></h5>
27220 <p><a name="F.10.5.2p1" href="#F.10.5.2p1"><small>1</small></a>
27222 <li> erfc(-(inf)) returns 2.
27223 <li> erfc(+(inf)) returns +0.
27226 <p><small><a href="#Contents">Contents</a></small>
27227 <h5><a name="F.10.5.3" href="#F.10.5.3">F.10.5.3 The lgamma functions</a></h5>
27228 <p><a name="F.10.5.3p1" href="#F.10.5.3p1"><small>1</small></a>
27230 <li> lgamma(1) returns +0.
27231 <li> lgamma(2) returns +0.
27232 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
27233 x a negative integer or zero.
27234 <li> lgamma(-(inf)) returns +(inf).
27235 <li> lgamma(+(inf)) returns +(inf).
27238 <p><small><a href="#Contents">Contents</a></small>
27239 <h5><a name="F.10.5.4" href="#F.10.5.4">F.10.5.4 The tgamma functions</a></h5>
27240 <p><a name="F.10.5.4p1" href="#F.10.5.4p1"><small>1</small></a>
27242 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
27243 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
27245 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
27246 <li> tgamma(+(inf)) returns +(inf).
27250 <p><small><a href="#Contents">Contents</a></small>
27251 <h4><a name="F.10.6" href="#F.10.6">F.10.6 Nearest integer functions</a></h4>
27253 <p><small><a href="#Contents">Contents</a></small>
27254 <h5><a name="F.10.6.1" href="#F.10.6.1">F.10.6.1 The ceil functions</a></h5>
27255 <p><a name="F.10.6.1p1" href="#F.10.6.1p1"><small>1</small></a>
27257 <li> ceil((+-)0) returns (+-)0.
27258 <li> ceil((+-)(inf)) returns (+-)(inf).
27260 <p><a name="F.10.6.1p2" href="#F.10.6.1p2"><small>2</small></a>
27261 The returned value is independent of the current rounding direction mode.
27262 <p><a name="F.10.6.1p3" href="#F.10.6.1p3"><small>3</small></a>
27263 The double version of ceil behaves as though implemented by
27265 #include <a href="#7.12"><math.h></a>
27266 #include <a href="#7.6"><fenv.h></a>
27267 #pragma STDC FENV_ACCESS ON
27268 double ceil(double x)
27271 int save_round = fegetround();
27272 fesetround(FE_UPWARD);
27273 result = rint(x); // or nearbyint instead of rint
27274 fesetround(save_round);
27278 <p><a name="F.10.6.1p4" href="#F.10.6.1p4"><small>4</small></a>
27279 The ceil functions may, but are not required to, raise the ''inexact'' floating-point
27280 exception for finite non-integer arguments, as this implementation does.
27282 <p><small><a href="#Contents">Contents</a></small>
27283 <h5><a name="F.10.6.2" href="#F.10.6.2">F.10.6.2 The floor functions</a></h5>
27284 <p><a name="F.10.6.2p1" href="#F.10.6.2p1"><small>1</small></a>
27286 <li> floor((+-)0) returns (+-)0.
27287 <li> floor((+-)(inf)) returns (+-)(inf).
27289 <p><a name="F.10.6.2p2" href="#F.10.6.2p2"><small>2</small></a>
27290 The returned value and is independent of the current rounding direction mode.
27291 <p><a name="F.10.6.2p3" href="#F.10.6.2p3"><small>3</small></a>
27292 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>. The floor functions may, but are
27293 not required to, raise the ''inexact'' floating-point exception for finite non-integer
27294 arguments, as that implementation does.
27296 <p><small><a href="#Contents">Contents</a></small>
27297 <h5><a name="F.10.6.3" href="#F.10.6.3">F.10.6.3 The nearbyint functions</a></h5>
27298 <p><a name="F.10.6.3p1" href="#F.10.6.3p1"><small>1</small></a>
27299 The nearbyint functions use IEC 60559 rounding according to the current rounding
27300 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
27301 value from the argument.
27303 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
27304 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
27308 <p><small><a href="#Contents">Contents</a></small>
27309 <h5><a name="F.10.6.4" href="#F.10.6.4">F.10.6.4 The rint functions</a></h5>
27310 <p><a name="F.10.6.4p1" href="#F.10.6.4p1"><small>1</small></a>
27311 The rint functions differ from the nearbyint functions only in that they do raise the
27312 ''inexact'' floating-point exception if the result differs in value from the argument.
27314 <p><small><a href="#Contents">Contents</a></small>
27315 <h5><a name="F.10.6.5" href="#F.10.6.5">F.10.6.5 The lrint and llrint functions</a></h5>
27316 <p><a name="F.10.6.5p1" href="#F.10.6.5p1"><small>1</small></a>
27317 The lrint and llrint functions provide floating-to-integer conversion as prescribed
27318 by IEC 60559. They round according to the current rounding direction. If the rounded
27319 value is outside the range of the return type, the numeric result is unspecified and the
27320 ''invalid'' floating-point exception is raised. When they raise no other floating-point
27321 exception and the result differs from the argument, they raise the ''inexact'' floating-point
27324 <p><small><a href="#Contents">Contents</a></small>
27325 <h5><a name="F.10.6.6" href="#F.10.6.6">F.10.6.6 The round functions</a></h5>
27326 <p><a name="F.10.6.6p1" href="#F.10.6.6p1"><small>1</small></a>
27328 <li> round((+-)0) returns (+-)0.
27329 <li> round((+-)(inf)) returns (+-)(inf).
27331 <p><a name="F.10.6.6p2" href="#F.10.6.6p2"><small>2</small></a>
27332 The returned value is independent of the current rounding direction mode.
27333 <p><a name="F.10.6.6p3" href="#F.10.6.6p3"><small>3</small></a>
27334 The double version of round behaves as though implemented by
27336 #include <a href="#7.12"><math.h></a>
27337 #include <a href="#7.6"><fenv.h></a>
27338 #pragma STDC FENV_ACCESS ON
27339 double round(double x)
27343 feholdexcept(&save_env);
27345 if (fetestexcept(FE_INEXACT)) {
27346 fesetround(FE_TOWARDZERO);
27347 result = rint(copysign(0.5 + fabs(x), x));
27349 feupdateenv(&save_env);
27353 The round functions may, but are not required to, raise the ''inexact'' floating-point
27354 exception for finite non-integer numeric arguments, as this implementation does.
27357 <p><small><a href="#Contents">Contents</a></small>
27358 <h5><a name="F.10.6.7" href="#F.10.6.7">F.10.6.7 The lround and llround functions</a></h5>
27359 <p><a name="F.10.6.7p1" href="#F.10.6.7p1"><small>1</small></a>
27360 The lround and llround functions differ from the lrint and llrint functions
27361 with the default rounding direction just in that the lround and llround functions
27362 round halfway cases away from zero and need not raise the ''inexact'' floating-point
27363 exception for non-integer arguments that round to within the range of the return type.
27365 <p><small><a href="#Contents">Contents</a></small>
27366 <h5><a name="F.10.6.8" href="#F.10.6.8">F.10.6.8 The trunc functions</a></h5>
27367 <p><a name="F.10.6.8p1" href="#F.10.6.8p1"><small>1</small></a>
27368 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
27369 rounding direction). The returned value is exact.
27371 <li> trunc((+-)0) returns (+-)0.
27372 <li> trunc((+-)(inf)) returns (+-)(inf).
27374 <p><a name="F.10.6.8p2" href="#F.10.6.8p2"><small>2</small></a>
27375 The returned value is independent of the current rounding direction mode. The trunc
27376 functions may, but are not required to, raise the ''inexact'' floating-point exception for
27377 finite non-integer arguments.
27379 <p><small><a href="#Contents">Contents</a></small>
27380 <h4><a name="F.10.7" href="#F.10.7">F.10.7 Remainder functions</a></h4>
27382 <p><small><a href="#Contents">Contents</a></small>
27383 <h5><a name="F.10.7.1" href="#F.10.7.1">F.10.7.1 The fmod functions</a></h5>
27384 <p><a name="F.10.7.1p1" href="#F.10.7.1p1"><small>1</small></a>
27386 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
27387 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
27388 infinite or y zero (and neither is a NaN).
27389 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
27391 <p><a name="F.10.7.1p2" href="#F.10.7.1p2"><small>2</small></a>
27392 When subnormal results are supported, the returned value is exact and is independent of
27393 the current rounding direction mode.
27394 <p><a name="F.10.7.1p3" href="#F.10.7.1p3"><small>3</small></a>
27395 The double version of fmod behaves as though implemented by
27398 #include <a href="#7.12"><math.h></a>
27399 #include <a href="#7.6"><fenv.h></a>
27400 #pragma STDC FENV_ACCESS ON
27401 double fmod(double x, double y)
27404 result = remainder(fabs(x), (y = fabs(y)));
27405 if (signbit(result)) result += y;
27406 return copysign(result, x);
27410 <p><small><a href="#Contents">Contents</a></small>
27411 <h5><a name="F.10.7.2" href="#F.10.7.2">F.10.7.2 The remainder functions</a></h5>
27412 <p><a name="F.10.7.2p1" href="#F.10.7.2p1"><small>1</small></a>
27413 The remainder functions are fully specified as a basic arithmetic operation in
27415 <p><a name="F.10.7.2p2" href="#F.10.7.2p2"><small>2</small></a>
27416 When subnormal results are supported, the returned value is exact and is independent of
27417 the current rounding direction mode.
27419 <p><small><a href="#Contents">Contents</a></small>
27420 <h5><a name="F.10.7.3" href="#F.10.7.3">F.10.7.3 The remquo functions</a></h5>
27421 <p><a name="F.10.7.3p1" href="#F.10.7.3p1"><small>1</small></a>
27422 The remquo functions follow the specifications for the remainder functions. They
27423 have no further specifications special to IEC 60559 implementations.
27424 <p><a name="F.10.7.3p2" href="#F.10.7.3p2"><small>2</small></a>
27425 When subnormal results are supported, the returned value is exact and is independent of
27426 the current rounding direction mode.
27428 <p><small><a href="#Contents">Contents</a></small>
27429 <h4><a name="F.10.8" href="#F.10.8">F.10.8 Manipulation functions</a></h4>
27431 <p><small><a href="#Contents">Contents</a></small>
27432 <h5><a name="F.10.8.1" href="#F.10.8.1">F.10.8.1 The copysign functions</a></h5>
27433 <p><a name="F.10.8.1p1" href="#F.10.8.1p1"><small>1</small></a>
27434 copysign is specified in the Appendix to IEC 60559.
27435 <p><a name="F.10.8.1p2" href="#F.10.8.1p2"><small>2</small></a>
27436 The returned value is exact and is independent of the current rounding direction mode.
27438 <p><small><a href="#Contents">Contents</a></small>
27439 <h5><a name="F.10.8.2" href="#F.10.8.2">F.10.8.2 The nan functions</a></h5>
27440 <p><a name="F.10.8.2p1" href="#F.10.8.2p1"><small>1</small></a>
27441 All IEC 60559 implementations support quiet NaNs, in all floating formats.
27442 <p><a name="F.10.8.2p2" href="#F.10.8.2p2"><small>2</small></a>
27443 The returned value is exact and is independent of the current rounding direction mode.
27445 <p><small><a href="#Contents">Contents</a></small>
27446 <h5><a name="F.10.8.3" href="#F.10.8.3">F.10.8.3 The nextafter functions</a></h5>
27447 <p><a name="F.10.8.3p1" href="#F.10.8.3p1"><small>1</small></a>
27449 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
27450 for x finite and the function value infinite.
27451 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
27452 exceptions for the function value subnormal or zero and x != y.
27454 <p><a name="F.10.8.3p2" href="#F.10.8.3p2"><small>2</small></a>
27455 Even though underflow or overflow can occur, the returned value is independent of the
27456 current rounding direction mode.
27458 <p><small><a href="#Contents">Contents</a></small>
27459 <h5><a name="F.10.8.4" href="#F.10.8.4">F.10.8.4 The nexttoward functions</a></h5>
27460 <p><a name="F.10.8.4p1" href="#F.10.8.4p1"><small>1</small></a>
27461 No additional requirements beyond those on nextafter.
27462 <p><a name="F.10.8.4p2" href="#F.10.8.4p2"><small>2</small></a>
27463 Even though underflow or overflow can occur, the returned value is independent of the
27464 current rounding direction mode.
27467 <p><small><a href="#Contents">Contents</a></small>
27468 <h4><a name="F.10.9" href="#F.10.9">F.10.9 Maximum, minimum, and positive difference functions</a></h4>
27470 <p><small><a href="#Contents">Contents</a></small>
27471 <h5><a name="F.10.9.1" href="#F.10.9.1">F.10.9.1 The fdim functions</a></h5>
27472 <p><a name="F.10.9.1p1" href="#F.10.9.1p1"><small>1</small></a>
27473 No additional requirements.
27475 <p><small><a href="#Contents">Contents</a></small>
27476 <h5><a name="F.10.9.2" href="#F.10.9.2">F.10.9.2 The fmax functions</a></h5>
27477 <p><a name="F.10.9.2p1" href="#F.10.9.2p1"><small>1</small></a>
27478 If just one argument is a NaN, the fmax functions return the other argument (if both
27479 arguments are NaNs, the functions return a NaN).
27480 <p><a name="F.10.9.2p2" href="#F.10.9.2p2"><small>2</small></a>
27481 The returned value is exact and is independent of the current rounding direction mode.
27482 <p><a name="F.10.9.2p3" href="#F.10.9.2p3"><small>3</small></a>
27483 The body of the fmax function might be<sup><a href="#note374"><b>374)</b></a></sup>
27485 { return (isgreaterequal(x, y) ||
27486 isnan(y)) ? x : y; }
27489 <p><b>Footnotes</b>
27490 <p><small><a name="note374" href="#note374">374)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
27491 return +0; however, implementation in software might be impractical.
27494 <p><small><a href="#Contents">Contents</a></small>
27495 <h5><a name="F.10.9.3" href="#F.10.9.3">F.10.9.3 The fmin functions</a></h5>
27496 <p><a name="F.10.9.3p1" href="#F.10.9.3p1"><small>1</small></a>
27497 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
27498 <p><a name="F.10.9.3p2" href="#F.10.9.3p2"><small>2</small></a>
27499 The returned value is exact and is independent of the current rounding direction mode.
27501 <p><small><a href="#Contents">Contents</a></small>
27502 <h4><a name="F.10.10" href="#F.10.10">F.10.10 Floating multiply-add</a></h4>
27504 <p><small><a href="#Contents">Contents</a></small>
27505 <h5><a name="F.10.10.1" href="#F.10.10.1">F.10.10.1 The fma functions</a></h5>
27506 <p><a name="F.10.10.1p1" href="#F.10.10.1p1"><small>1</small></a>
27508 <li> fma(x, y, z) computes xy + z, correctly rounded once.
27509 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
27510 exception if one of x and y is infinite, the other is zero, and z is a NaN.
27511 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
27512 one of x and y is infinite, the other is zero, and z is not a NaN.
27513 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
27514 times y is an exact infinity and z is also an infinity but with the opposite sign.
27522 <p><small><a href="#Contents">Contents</a></small>
27523 <h4><a name="F.10.11" href="#F.10.11">F.10.11 Comparison macros</a></h4>
27524 <p><a name="F.10.11p1" href="#F.10.11p1"><small>1</small></a>
27525 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
27526 equivalent result values, even if argument values are represented in wider formats. Thus,
27527 comparison macro arguments represented in formats wider than their semantic types are
27528 not converted to the semantic types, unless the wide evaluation method converts operands
27529 of relational operators to their semantic types. The standard wide evaluation methods
27530 characterized by FLT_EVAL_METHOD equal to 1 or 2 (<a href="#5.2.4.2.2">5.2.4.2.2</a>), do not convert
27531 operands of relational operators to their semantic types.
27534 <p><small><a href="#Contents">Contents</a></small>
27535 <h2><a name="G" href="#G">Annex G</a></h2>
27538 IEC 60559-compatible complex arithmetic
27541 <p><small><a href="#Contents">Contents</a></small>
27542 <h3><a name="G.1" href="#G.1">G.1 Introduction</a></h3>
27543 <p><a name="G.1p1" href="#G.1p1"><small>1</small></a>
27544 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
27545 IEC 60559 real floating-point arithmetic. An implementation that defines
27546 __STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<sup><a href="#note375"><b>375)</b></a></sup>
27548 <p><b>Footnotes</b>
27549 <p><small><a name="note375" href="#note375">375)</a> Implementations that do not define __STDC_IEC_559_COMPLEX__ are not required to conform
27550 to these specifications.
27553 <p><small><a href="#Contents">Contents</a></small>
27554 <h3><a name="G.2" href="#G.2">G.2 Types</a></h3>
27555 <p><a name="G.2p1" href="#G.2p1"><small>1</small></a>
27556 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
27557 used as a type specifier within declaration specifiers in the same way as _Complex is
27558 (thus, _Imaginary float is a valid type name).
27559 <p><a name="G.2p2" href="#G.2p2"><small>2</small></a>
27560 There are three imaginary types, designated as float _Imaginary, double
27561 _Imaginary, and long double _Imaginary. The imaginary types (along with
27562 the real floating and complex types) are floating types.
27563 <p><a name="G.2p3" href="#G.2p3"><small>3</small></a>
27564 For imaginary types, the corresponding real type is given by deleting the keyword
27565 _Imaginary from the type name.
27566 <p><a name="G.2p4" href="#G.2p4"><small>4</small></a>
27567 Each imaginary type has the same representation and alignment requirements as the
27568 corresponding real type. The value of an object of imaginary type is the value of the real
27569 representation times the imaginary unit.
27570 <p><a name="G.2p5" href="#G.2p5"><small>5</small></a>
27571 The imaginary type domain comprises the imaginary types.
27573 <p><small><a href="#Contents">Contents</a></small>
27574 <h3><a name="G.3" href="#G.3">G.3 Conventions</a></h3>
27575 <p><a name="G.3p1" href="#G.3p1"><small>1</small></a>
27576 A complex or imaginary value with at least one infinite part is regarded as an infinity
27577 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
27578 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
27579 a zero if each of its parts is a zero.
27586 <p><small><a href="#Contents">Contents</a></small>
27587 <h3><a name="G.4" href="#G.4">G.4 Conversions</a></h3>
27589 <p><small><a href="#Contents">Contents</a></small>
27590 <h4><a name="G.4.1" href="#G.4.1">G.4.1 Imaginary types</a></h4>
27591 <p><a name="G.4.1p1" href="#G.4.1p1"><small>1</small></a>
27592 Conversions among imaginary types follow rules analogous to those for real floating
27595 <p><small><a href="#Contents">Contents</a></small>
27596 <h4><a name="G.4.2" href="#G.4.2">G.4.2 Real and imaginary</a></h4>
27597 <p><a name="G.4.2p1" href="#G.4.2p1"><small>1</small></a>
27598 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note376"><b>376)</b></a></sup> the
27599 result is a positive zero.
27600 <p><a name="G.4.2p2" href="#G.4.2p2"><small>2</small></a>
27601 When a value of real type is converted to an imaginary type, the result is a positive
27604 <p><b>Footnotes</b>
27605 <p><small><a name="note376" href="#note376">376)</a> See <a href="#6.3.1.2">6.3.1.2</a>.
27608 <p><small><a href="#Contents">Contents</a></small>
27609 <h4><a name="G.4.3" href="#G.4.3">G.4.3 Imaginary and complex</a></h4>
27610 <p><a name="G.4.3p1" href="#G.4.3p1"><small>1</small></a>
27611 When a value of imaginary type is converted to a complex type, the real part of the
27612 complex result value is a positive zero and the imaginary part of the complex result value
27613 is determined by the conversion rules for the corresponding real types.
27614 <p><a name="G.4.3p2" href="#G.4.3p2"><small>2</small></a>
27615 When a value of complex type is converted to an imaginary type, the real part of the
27616 complex value is discarded and the value of the imaginary part is converted according to
27617 the conversion rules for the corresponding real types.
27619 <p><small><a href="#Contents">Contents</a></small>
27620 <h3><a name="G.5" href="#G.5">G.5 Binary operators</a></h3>
27621 <p><a name="G.5p1" href="#G.5p1"><small>1</small></a>
27622 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
27623 operation with an imaginary operand.
27624 <p><a name="G.5p2" href="#G.5p2"><small>2</small></a>
27625 For most operand types, the value of the result of a binary operator with an imaginary or
27626 complex operand is completely determined, with reference to real arithmetic, by the usual
27627 mathematical formula. For some operand types, the usual mathematical formula is
27628 problematic because of its treatment of infinities and because of undue overflow or
27629 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
27630 not completely determined.
27637 <p><small><a href="#Contents">Contents</a></small>
27638 <h4><a name="G.5.1" href="#G.5.1">G.5.1 Multiplicative operators</a></h4>
27639 <p><b>Semantics</b>
27640 <p><a name="G.5.1p1" href="#G.5.1p1"><small>1</small></a>
27641 If one operand has real type and the other operand has imaginary type, then the result has
27642 imaginary type. If both operands have imaginary type, then the result has real type. (If
27643 either operand has complex type, then the result has complex type.)
27644 <p><a name="G.5.1p2" href="#G.5.1p2"><small>2</small></a>
27645 If the operands are not both complex, then the result and floating-point exception
27646 behavior of the * operator is defined by the usual mathematical formula:
27652 x xu i(xv) (xu) + i(xv)
27656 iy i(yu) -yv (-yv) + i(yu)
27660 x + iy (xu) + i(yu) (-yv) + i(xv)
27662 <p><a name="G.5.1p3" href="#G.5.1p3"><small>3</small></a>
27663 If the second operand is not complex, then the result and floating-point exception
27664 behavior of the / operator is defined by the usual mathematical formula:
27678 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
27680 <p><a name="G.5.1p4" href="#G.5.1p4"><small>4</small></a>
27681 The * and / operators satisfy the following infinity properties for all real, imaginary, and
27682 complex operands:<sup><a href="#note377"><b>377)</b></a></sup>
27684 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
27685 infinity, then the result of the * operator is an infinity;
27686 <li> if the first operand is an infinity and the second operand is a finite number, then the
27687 result of the / operator is an infinity;
27688 <li> if the first operand is a finite number and the second operand is an infinity, then the
27689 result of the / operator is a zero;
27695 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
27696 a zero, then the result of the / operator is an infinity.
27698 <p><a name="G.5.1p5" href="#G.5.1p5"><small>5</small></a>
27699 If both operands of the * operator are complex or if the second operand of the / operator
27700 is complex, the operator raises floating-point exceptions if appropriate for the calculation
27701 of the parts of the result, and may raise spurious floating-point exceptions.
27702 <p><a name="G.5.1p6" href="#G.5.1p6"><small>6</small></a>
27703 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
27704 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
27707 #include <a href="#7.12"><math.h></a>
27708 #include <a href="#7.3"><complex.h></a>
27709 /* Multiply z * w ... */
27710 double complex _Cmultd(double complex z, double complex w)
27712 #pragma STDC FP_CONTRACT OFF
27713 double a, b, c, d, ac, bd, ad, bc, x, y;
27714 a = creal(z); b = cimag(z);
27715 c = creal(w); d = cimag(w);
27716 ac = a * c; bd = b * d;
27717 ad = a * d; bc = b * c;
27718 x = ac - bd; y = ad + bc;
27719 if (isnan(x) && isnan(y)) {
27720 /* Recover infinities that computed as NaN+iNaN ... */
27722 if (isinf(a) || isinf(b)) { // z is infinite
27723 /* "Box" the infinity and change NaNs in the other factor to 0 */
27724 a = copysign(isinf(a) ? 1.0 : 0.0, a);
27725 b = copysign(isinf(b) ? 1.0 : 0.0, b);
27726 if (isnan(c)) c = copysign(0.0, c);
27727 if (isnan(d)) d = copysign(0.0, d);
27730 if (isinf(c) || isinf(d)) { // w is infinite
27731 /* "Box" the infinity and change NaNs in the other factor to 0 */
27732 c = copysign(isinf(c) ? 1.0 : 0.0, c);
27733 d = copysign(isinf(d) ? 1.0 : 0.0, d);
27734 if (isnan(a)) a = copysign(0.0, a);
27735 if (isnan(b)) b = copysign(0.0, b);
27738 if (!recalc && (isinf(ac) || isinf(bd) ||
27739 isinf(ad) || isinf(bc))) {
27740 /* Recover infinities from overflow by changing NaNs to 0 ... */
27741 if (isnan(a)) a = copysign(0.0, a);
27742 if (isnan(b)) b = copysign(0.0, b);
27743 if (isnan(c)) c = copysign(0.0, c);
27744 if (isnan(d)) d = copysign(0.0, d);
27748 x = INFINITY * ( a * c - b * d );
27749 y = INFINITY * ( a * d + b * c );
27755 <p><a name="G.5.1p7" href="#G.5.1p7"><small>7</small></a>
27756 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
27757 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
27759 <p><a name="G.5.1p8" href="#G.5.1p8"><small>8</small></a>
27760 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
27763 #include <a href="#7.12"><math.h></a>
27764 #include <a href="#7.3"><complex.h></a>
27765 /* Divide z / w ... */
27766 double complex _Cdivd(double complex z, double complex w)
27768 #pragma STDC FP_CONTRACT OFF
27769 double a, b, c, d, logbw, denom, x, y;
27771 a = creal(z); b = cimag(z);
27772 c = creal(w); d = cimag(w);
27773 logbw = logb(fmax(fabs(c), fabs(d)));
27774 if (isfinite(logbw)) {
27775 ilogbw = (int)logbw;
27776 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
27778 denom = c * c + d * d;
27779 x = scalbn((a * c + b * d) / denom, -ilogbw);
27780 y = scalbn((b * c - a * d) / denom, -ilogbw);
27781 /* Recover infinities and zeros that computed as NaN+iNaN; */
27782 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
27783 if (isnan(x) && isnan(y)) {
27784 if ((denom == 0.0) &&
27785 (!isnan(a) || !isnan(b))) {
27786 x = copysign(INFINITY, c) * a;
27787 y = copysign(INFINITY, c) * b;
27789 else if ((isinf(a) || isinf(b)) &&
27790 isfinite(c) && isfinite(d)) {
27791 a = copysign(isinf(a) ? 1.0 : 0.0, a);
27792 b = copysign(isinf(b) ? 1.0 : 0.0, b);
27793 x = INFINITY * ( a * c + b * d );
27794 y = INFINITY * ( b * c - a * d );
27796 else if ((logbw == INFINITY) &&
27797 isfinite(a) && isfinite(b)) {
27798 c = copysign(isinf(c) ? 1.0 : 0.0, c);
27799 d = copysign(isinf(d) ? 1.0 : 0.0, d);
27800 x = 0.0 * ( a * c + b * d );
27801 y = 0.0 * ( b * c - a * d );
27807 <p><a name="G.5.1p9" href="#G.5.1p9"><small>9</small></a>
27808 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
27809 for multiplication. In the spirit of the multiplication example above, this code does not defend against
27810 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
27811 with division, provides better roundoff characteristics.
27814 <p><b>Footnotes</b>
27815 <p><small><a name="note377" href="#note377">377)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
27816 (at least where the state for CX_LIMITED_RANGE is ''off'').
27819 <p><small><a href="#Contents">Contents</a></small>
27820 <h4><a name="G.5.2" href="#G.5.2">G.5.2 Additive operators</a></h4>
27821 <p><b>Semantics</b>
27822 <p><a name="G.5.2p1" href="#G.5.2p1"><small>1</small></a>
27823 If both operands have imaginary type, then the result has imaginary type. (If one operand
27824 has real type and the other operand has imaginary type, or if either operand has complex
27825 type, then the result has complex type.)
27826 <p><a name="G.5.2p2" href="#G.5.2p2"><small>2</small></a>
27827 In all cases the result and floating-point exception behavior of a + or - operator is defined
27828 by the usual mathematical formula:
27834 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
27838 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
27842 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
27845 <p><small><a href="#Contents">Contents</a></small>
27846 <h3><a name="G.6" href="#G.6">G.6 Complex arithmetic <complex.h></a></h3>
27847 <p><a name="G.6p1" href="#G.6p1"><small>1</small></a>
27856 are defined, respectively, as _Imaginary and a constant expression of type const
27857 float _Imaginary with the value of the imaginary unit. The macro
27861 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
27862 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
27864 <p><a name="G.6p2" href="#G.6p2"><small>2</small></a>
27865 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
27866 particularly suited to IEC 60559 implementations. For families of functions, the
27867 specifications apply to all of the functions even though only the principal function is
27869 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
27870 and the result, the result has the same sign as the argument.
27871 <p><a name="G.6p3" href="#G.6p3"><small>3</small></a>
27872 The functions are continuous onto both sides of their branch cuts, taking into account the
27873 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. -
27874 <p><a name="G.6p4" href="#G.6p4"><small>4</small></a>
27875 Since complex and imaginary values are composed of real values, each function may be
27876 regarded as computing real values from real values. Except as noted, the functions treat
27877 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
27878 manner consistent with the specifications for real functions in F.10.<sup><a href="#note378"><b>378)</b></a></sup>
27879 <p><a name="G.6p5" href="#G.6p5"><small>5</small></a>
27880 The functions cimag, conj, cproj, and creal are fully specified for all
27881 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
27883 <p><a name="G.6p6" href="#G.6p6"><small>6</small></a>
27884 Each of the functions cabs and carg is specified by a formula in terms of a real
27885 function (whose special cases are covered in <a href="#F">annex F</a>):
27887 cabs(x + iy) = hypot(x, y)
27888 carg(x + iy) = atan2(y, x)
27890 <p><a name="G.6p7" href="#G.6p7"><small>7</small></a>
27891 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
27892 a formula in terms of other complex functions (whose special cases are specified below):
27894 casin(z) = -i casinh(iz)
27895 catan(z) = -i catanh(iz)
27896 ccos(z) = ccosh(iz)
27897 csin(z) = -i csinh(iz)
27898 ctan(z) = -i ctanh(iz)
27900 <p><a name="G.6p8" href="#G.6p8"><small>8</small></a>
27901 For the other functions, the following subclauses specify behavior for special cases,
27902 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
27903 families of functions, the specifications apply to all of the functions even though only the
27904 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
27905 specifications for the upper half-plane imply the specifications for the lower half-plane; if
27906 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
27907 specifications for the first quadrant imply the specifications for the other three quadrants.
27908 <p><a name="G.6p9" href="#G.6p9"><small>9</small></a>
27909 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
27916 <p><b>Footnotes</b>
27917 <p><small><a name="note378" href="#note378">378)</a> As noted in <a href="#G.3">G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its
27918 other part is a NaN.
27921 <p><small><a href="#Contents">Contents</a></small>
27922 <h4><a name="G.6.1" href="#G.6.1">G.6.1 Trigonometric functions</a></h4>
27924 <p><small><a href="#Contents">Contents</a></small>
27925 <h5><a name="G.6.1.1" href="#G.6.1.1">G.6.1.1 The cacos functions</a></h5>
27926 <p><a name="G.6.1.1p1" href="#G.6.1.1p1"><small>1</small></a>
27928 <li> cacos(conj(z)) = conj(cacos(z)).
27929 <li> cacos((+-)0 + i0) returns pi /2 - i0.
27930 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
27931 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
27932 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27933 point exception, for nonzero finite x.
27934 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
27935 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
27936 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
27937 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
27938 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
27939 result is unspecified).
27940 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27941 point exception, for finite y.
27942 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
27943 <li> cacos(NaN + iNaN) returns NaN + iNaN.
27946 <p><small><a href="#Contents">Contents</a></small>
27947 <h4><a name="G.6.2" href="#G.6.2">G.6.2 Hyperbolic functions</a></h4>
27949 <p><small><a href="#Contents">Contents</a></small>
27950 <h5><a name="G.6.2.1" href="#G.6.2.1">G.6.2.1 The cacosh functions</a></h5>
27951 <p><a name="G.6.2.1p1" href="#G.6.2.1p1"><small>1</small></a>
27953 <li> cacosh(conj(z)) = conj(cacosh(z)).
27954 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
27955 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
27956 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27957 floating-point exception, for finite x.
27958 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
27959 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
27960 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
27961 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
27962 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
27964 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27965 floating-point exception, for finite y.
27966 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
27967 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
27970 <p><small><a href="#Contents">Contents</a></small>
27971 <h5><a name="G.6.2.2" href="#G.6.2.2">G.6.2.2 The casinh functions</a></h5>
27972 <p><a name="G.6.2.2p1" href="#G.6.2.2p1"><small>1</small></a>
27974 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
27975 <li> casinh(+0 + i0) returns 0 + i0.
27976 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
27977 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27978 floating-point exception, for finite x.
27979 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
27980 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
27981 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
27982 <li> casinh(NaN + i0) returns NaN + i0.
27983 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27984 floating-point exception, for finite nonzero y.
27985 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
27987 <li> casinh(NaN + iNaN) returns NaN + iNaN.
27990 <p><small><a href="#Contents">Contents</a></small>
27991 <h5><a name="G.6.2.3" href="#G.6.2.3">G.6.2.3 The catanh functions</a></h5>
27992 <p><a name="G.6.2.3p1" href="#G.6.2.3p1"><small>1</small></a>
27994 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
27995 <li> catanh(+0 + i0) returns +0 + i0.
27996 <li> catanh(+0 + iNaN) returns +0 + iNaN.
27997 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
27999 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
28000 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
28001 floating-point exception, for nonzero finite x.
28002 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
28003 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
28004 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
28006 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
28007 floating-point exception, for finite y.
28008 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
28010 <li> catanh(NaN + iNaN) returns NaN + iNaN.
28013 <p><small><a href="#Contents">Contents</a></small>
28014 <h5><a name="G.6.2.4" href="#G.6.2.4">G.6.2.4 The ccosh functions</a></h5>
28015 <p><a name="G.6.2.4p1" href="#G.6.2.4p1"><small>1</small></a>
28017 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
28018 <li> ccosh(+0 + i0) returns 1 + i0.
28019 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
28020 result is unspecified) and raises the ''invalid'' floating-point exception.
28021 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
28022 result is unspecified).
28023 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28024 exception, for finite nonzero x.
28025 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28026 point exception, for finite nonzero x.
28027 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
28028 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
28029 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
28030 unspecified) and raises the ''invalid'' floating-point exception.
28031 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
28032 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
28033 result is unspecified).
28034 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28035 point exception, for all nonzero numbers y.
28036 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
28039 <p><small><a href="#Contents">Contents</a></small>
28040 <h5><a name="G.6.2.5" href="#G.6.2.5">G.6.2.5 The csinh functions</a></h5>
28041 <p><a name="G.6.2.5p1" href="#G.6.2.5p1"><small>1</small></a>
28043 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
28044 <li> csinh(+0 + i0) returns +0 + i0.
28045 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
28046 unspecified) and raises the ''invalid'' floating-point exception.
28047 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
28050 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28051 exception, for positive finite x.
28052 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28053 point exception, for finite nonzero x.
28054 <li> csinh(+(inf) + i0) returns +(inf) + i0.
28055 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
28056 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
28057 unspecified) and raises the ''invalid'' floating-point exception.
28058 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
28060 <li> csinh(NaN + i0) returns NaN + i0.
28061 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28062 point exception, for all nonzero numbers y.
28063 <li> csinh(NaN + iNaN) returns NaN + iNaN.
28066 <p><small><a href="#Contents">Contents</a></small>
28067 <h5><a name="G.6.2.6" href="#G.6.2.6">G.6.2.6 The ctanh functions</a></h5>
28068 <p><a name="G.6.2.6p1" href="#G.6.2.6p1"><small>1</small></a>
28070 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
28071 <li> ctanh(+0 + i0) returns +0 + i0.
28072 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28073 exception, for finite x.
28074 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28075 point exception, for finite x.
28076 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
28077 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
28079 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
28080 result is unspecified).
28081 <li> ctanh(NaN + i0) returns NaN + i0.
28082 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28083 point exception, for all nonzero numbers y.
28084 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
28088 <p><small><a href="#Contents">Contents</a></small>
28089 <h4><a name="G.6.3" href="#G.6.3">G.6.3 Exponential and logarithmic functions</a></h4>
28091 <p><small><a href="#Contents">Contents</a></small>
28092 <h5><a name="G.6.3.1" href="#G.6.3.1">G.6.3.1 The cexp functions</a></h5>
28093 <p><a name="G.6.3.1p1" href="#G.6.3.1p1"><small>1</small></a>
28095 <li> cexp(conj(z)) = conj(cexp(z)).
28096 <li> cexp((+-)0 + i0) returns 1 + i0.
28097 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28098 exception, for finite x.
28099 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28100 point exception, for finite x.
28101 <li> cexp(+(inf) + i0) returns +(inf) + i0.
28102 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
28103 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
28104 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
28105 the result are unspecified).
28106 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
28107 exception (where the sign of the real part of the result is unspecified).
28108 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
28109 of the result are unspecified).
28110 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
28112 <li> cexp(NaN + i0) returns NaN + i0.
28113 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28114 point exception, for all nonzero numbers y.
28115 <li> cexp(NaN + iNaN) returns NaN + iNaN.
28118 <p><small><a href="#Contents">Contents</a></small>
28119 <h5><a name="G.6.3.2" href="#G.6.3.2">G.6.3.2 The clog functions</a></h5>
28120 <p><a name="G.6.3.2p1" href="#G.6.3.2p1"><small>1</small></a>
28122 <li> clog(conj(z)) = conj(clog(z)).
28123 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
28125 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
28127 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
28128 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28129 point exception, for finite x.
28131 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
28132 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
28133 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
28134 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
28135 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
28136 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28137 point exception, for finite y.
28138 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
28139 <li> clog(NaN + iNaN) returns NaN + iNaN.
28142 <p><small><a href="#Contents">Contents</a></small>
28143 <h4><a name="G.6.4" href="#G.6.4">G.6.4 Power and absolute-value functions</a></h4>
28145 <p><small><a href="#Contents">Contents</a></small>
28146 <h5><a name="G.6.4.1" href="#G.6.4.1">G.6.4.1 The cpow functions</a></h5>
28147 <p><a name="G.6.4.1p1" href="#G.6.4.1p1"><small>1</small></a>
28148 The cpow functions raise floating-point exceptions if appropriate for the calculation of
28149 the parts of the result, and may also raise spurious floating-point exceptions.<sup><a href="#note379"><b>379)</b></a></sup>
28151 <p><b>Footnotes</b>
28152 <p><small><a name="note379" href="#note379">379)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
28153 implementations that treat special cases more carefully.
28156 <p><small><a href="#Contents">Contents</a></small>
28157 <h5><a name="G.6.4.2" href="#G.6.4.2">G.6.4.2 The csqrt functions</a></h5>
28158 <p><a name="G.6.4.2p1" href="#G.6.4.2p1"><small>1</small></a>
28160 <li> csqrt(conj(z)) = conj(csqrt(z)).
28161 <li> csqrt((+-)0 + i0) returns +0 + i0.
28162 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
28163 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28164 point exception, for finite x.
28165 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
28166 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
28167 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
28168 result is unspecified).
28169 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
28170 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28171 point exception, for finite y.
28172 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
28180 <p><small><a href="#Contents">Contents</a></small>
28181 <h3><a name="G.7" href="#G.7">G.7 Type-generic math <tgmath.h></a></h3>
28182 <p><a name="G.7p1" href="#G.7p1"><small>1</small></a>
28183 Type-generic macros that accept complex arguments also accept imaginary arguments. If
28184 an argument is imaginary, the macro expands to an expression whose type is real,
28185 imaginary, or complex, as appropriate for the particular function: if the argument is
28186 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
28187 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
28188 the types of the others are complex.
28189 <p><a name="G.7p2" href="#G.7p2"><small>2</small></a>
28190 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
28191 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
28196 sin(iy) = i sinh(y)
28197 tan(iy) = i tanh(y)
28199 sinh(iy) = i sin(y)
28200 tanh(iy) = i tan(y)
28201 asin(iy) = i asinh(y)
28202 atan(iy) = i atanh(y)
28203 asinh(iy) = i asin(y)
28204 atanh(iy) = i atan(y)
28207 <p><small><a href="#Contents">Contents</a></small>
28208 <h2><a name="H" href="#H">Annex H</a></h2>
28211 Language independent arithmetic
28214 <p><small><a href="#Contents">Contents</a></small>
28215 <h3><a name="H.1" href="#H.1">H.1 Introduction</a></h3>
28216 <p><a name="H.1p1" href="#H.1p1"><small>1</small></a>
28217 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
28218 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
28219 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
28221 <p><small><a href="#Contents">Contents</a></small>
28222 <h3><a name="H.2" href="#H.2">H.2 Types</a></h3>
28223 <p><a name="H.2p1" href="#H.2p1"><small>1</small></a>
28224 The relevant C arithmetic types meet the requirements of LIA-1 types if an
28225 implementation adds notification of exceptional arithmetic operations and meets the 1
28226 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
28228 <p><small><a href="#Contents">Contents</a></small>
28229 <h4><a name="H.2.1" href="#H.2.1">H.2.1 Boolean type</a></h4>
28230 <p><a name="H.2.1p1" href="#H.2.1p1"><small>1</small></a>
28231 The LIA-1 data type Boolean is implemented by the C data type bool with values of
28232 true and false, all from <a href="#7.18"><stdbool.h></a>.
28234 <p><small><a href="#Contents">Contents</a></small>
28235 <h4><a name="H.2.2" href="#H.2.2">H.2.2 Integer types</a></h4>
28236 <p><a name="H.2.2p1" href="#H.2.2p1"><small>1</small></a>
28237 The signed C integer types int, long int, long long int, and the corresponding
28238 unsigned types are compatible with LIA-1. If an implementation adds support for the
28239 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
28240 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
28241 in that overflows or out-of-bounds results silently wrap. An implementation that defines
28242 signed integer types as also being modulo need not detect integer overflow, in which case,
28243 only integer divide-by-zero need be detected.
28244 <p><a name="H.2.2p2" href="#H.2.2p2"><small>2</small></a>
28245 The parameters for the integer data types can be accessed by the following:
28246 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
28250 minint INT_MIN, LONG_MIN, LLONG_MIN
28251 <p><a name="H.2.2p3" href="#H.2.2p3"><small>3</small></a>
28252 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
28253 is always 0 for the unsigned types, and is not provided for those types.
28256 <p><small><a href="#Contents">Contents</a></small>
28257 <h5><a name="H.2.2.1" href="#H.2.2.1">H.2.2.1 Integer operations</a></h5>
28258 <p><a name="H.2.2.1p1" href="#H.2.2.1p1"><small>1</small></a>
28259 The integer operations on integer types are the following:
28266 absI abs(x), labs(x), llabs(x)
28273 where x and y are expressions of the same integer type.
28275 <p><small><a href="#Contents">Contents</a></small>
28276 <h4><a name="H.2.3" href="#H.2.3">H.2.3 Floating-point types</a></h4>
28277 <p><a name="H.2.3p1" href="#H.2.3p1"><small>1</small></a>
28278 The C floating-point types float, double, and long double are compatible with
28279 LIA-1. If an implementation adds support for the LIA-1 exceptional values
28280 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
28281 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
28282 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
28285 <p><small><a href="#Contents">Contents</a></small>
28286 <h5><a name="H.2.3.1" href="#H.2.3.1">H.2.3.1 Floating-point parameters</a></h5>
28287 <p><a name="H.2.3.1p1" href="#H.2.3.1p1"><small>1</small></a>
28288 The parameters for a floating point data type can be accessed by the following:
28290 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
28291 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
28292 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
28293 <p><a name="H.2.3.1p2" href="#H.2.3.1p2"><small>2</small></a>
28294 The derived constants for the floating point types are accessed by the following:
28296 fmax FLT_MAX, DBL_MAX, LDBL_MAX
28297 fminN FLT_MIN, DBL_MIN, LDBL_MIN
28298 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
28299 rnd_style FLT_ROUNDS
28301 <p><small><a href="#Contents">Contents</a></small>
28302 <h5><a name="H.2.3.2" href="#H.2.3.2">H.2.3.2 Floating-point operations</a></h5>
28303 <p><a name="H.2.3.2p1" href="#H.2.3.2p1"><small>1</small></a>
28304 The floating-point operations on floating-point types are the following:
28310 absF fabsf(x), fabs(x), fabsl(x)
28311 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
28312 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
28314 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
28316 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
28317 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
28324 where x and y are expressions of the same floating point type, n is of type int, and li
28325 is of type long int.
28327 <p><small><a href="#Contents">Contents</a></small>
28328 <h5><a name="H.2.3.3" href="#H.2.3.3">H.2.3.3 Rounding styles</a></h5>
28329 <p><a name="H.2.3.3p1" href="#H.2.3.3p1"><small>1</small></a>
28330 The C Standard requires all floating types to use the same radix and rounding style, so
28331 that only one identifier for each is provided to map to LIA-1.
28332 <p><a name="H.2.3.3p2" href="#H.2.3.3p2"><small>2</small></a>
28333 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
28334 truncate FLT_ROUNDS == 0
28336 nearest FLT_ROUNDS == 1
28337 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
28338 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
28339 in all relevant LIA-1 operations, not just addition as in C.
28341 <p><small><a href="#Contents">Contents</a></small>
28342 <h4><a name="H.2.4" href="#H.2.4">H.2.4 Type conversions</a></h4>
28343 <p><a name="H.2.4p1" href="#H.2.4p1"><small>1</small></a>
28344 The LIA-1 type conversions are the following type casts:
28345 cvtI' -> I (int)i, (long int)i, (long long int)i,
28347 (unsigned int)i, (unsigned long int)i,
28348 (unsigned long long int)i
28350 cvtF -> I (int)x, (long int)x, (long long int)x,
28352 (unsigned int)x, (unsigned long int)x,
28353 (unsigned long long int)x
28355 cvtI -> F (float)i, (double)i, (long double)i
28356 cvtF' -> F (float)x, (double)x, (long double)x
28357 <p><a name="H.2.4p2" href="#H.2.4p2"><small>2</small></a>
28358 In the above conversions from floating to integer, the use of (cast)x can be replaced with
28359 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
28360 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
28361 conversion functions, lrint(), llrint(), lround(), and llround(), can be
28362 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
28363 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
28364 <p><a name="H.2.4p3" href="#H.2.4p3"><small>3</small></a>
28365 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
28366 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
28367 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
28368 to 65535.0 which can then be cast to unsigned short int. But, the
28369 remainder() function is not useful for doing silent wrapping to signed integer types,
28370 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
28371 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
28373 <p><a name="H.2.4p4" href="#H.2.4p4"><small>4</small></a>
28374 C's conversions (casts) from floating-point to floating-point can meet LIA-1
28375 requirements if an implementation uses round-to-nearest (IEC 60559 default).
28376 <p><a name="H.2.4p5" href="#H.2.4p5"><small>5</small></a>
28377 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
28378 implementation uses round-to-nearest.
28381 <p><small><a href="#Contents">Contents</a></small>
28382 <h3><a name="H.3" href="#H.3">H.3 Notification</a></h3>
28383 <p><a name="H.3p1" href="#H.3p1"><small>1</small></a>
28384 Notification is the process by which a user or program is informed that an exceptional
28385 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
28386 allows an implementation to cause a notification to occur when any arithmetic operation
28387 returns an exceptional value as defined in LIA-1 clause 5.
28389 <p><small><a href="#Contents">Contents</a></small>
28390 <h4><a name="H.3.1" href="#H.3.1">H.3.1 Notification alternatives</a></h4>
28391 <p><a name="H.3.1p1" href="#H.3.1p1"><small>1</small></a>
28392 LIA-1 requires at least the following two alternatives for handling of notifications:
28393 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
28395 <p><a name="H.3.1p2" href="#H.3.1p2"><small>2</small></a>
28396 An implementation need only support a given notification alternative for the entire
28397 program. An implementation may support the ability to switch between notification
28398 alternatives during execution, but is not required to do so. An implementation can
28399 provide separate selection for each kind of notification, but this is not required.
28400 <p><a name="H.3.1p3" href="#H.3.1p3"><small>3</small></a>
28401 C allows an implementation to provide notification. C's SIGFPE (for traps) and
28402 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
28403 can provide LIA-1 notification.
28404 <p><a name="H.3.1p4" href="#H.3.1p4"><small>4</small></a>
28405 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
28406 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
28407 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
28408 and-resume behavior with the same constraint.
28410 <p><small><a href="#Contents">Contents</a></small>
28411 <h5><a name="H.3.1.1" href="#H.3.1.1">H.3.1.1 Indicators</a></h5>
28412 <p><a name="H.3.1.1p1" href="#H.3.1.1p1"><small>1</small></a>
28413 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
28414 <p><a name="H.3.1.1p2" href="#H.3.1.1p2"><small>2</small></a>
28415 The following mapping is for floating-point types:
28416 undefined FE_INVALID, FE_DIVBYZERO
28417 floating_overflow FE_OVERFLOW
28418 underflow FE_UNDERFLOW
28419 <p><a name="H.3.1.1p3" href="#H.3.1.1p3"><small>3</small></a>
28420 The floating-point indicator interrogation and manipulation operations are:
28421 set_indicators feraiseexcept(i)
28422 clear_indicators feclearexcept(i)
28423 test_indicators fetestexcept(i)
28424 current_indicators fetestexcept(FE_ALL_EXCEPT)
28425 where i is an expression of type int representing a subset of the LIA-1 indicators.
28426 <p><a name="H.3.1.1p4" href="#H.3.1.1p4"><small>4</small></a>
28427 C allows an implementation to provide the following LIA-1 required behavior: at
28428 program termination if any indicator is set the implementation shall send an unambiguous
28430 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
28431 <p><a name="H.3.1.1p5" href="#H.3.1.1p5"><small>5</small></a>
28432 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
28433 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
28436 <p><small><a href="#Contents">Contents</a></small>
28437 <h5><a name="H.3.1.2" href="#H.3.1.2">H.3.1.2 Traps</a></h5>
28438 <p><a name="H.3.1.2p1" href="#H.3.1.2p1"><small>1</small></a>
28439 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
28440 math library functions (which are not permitted to invoke a user's signal handler for
28441 SIGFPE). An implementation can provide an alternative of notification through
28442 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
28443 <p><a name="H.3.1.2p2" href="#H.3.1.2p2"><small>2</small></a>
28444 LIA-1 does not require that traps be precise.
28445 <p><a name="H.3.1.2p3" href="#H.3.1.2p3"><small>3</small></a>
28446 C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions,
28447 if there is any signal raised for them.
28448 <p><a name="H.3.1.2p4" href="#H.3.1.2p4"><small>4</small></a>
28449 C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
28450 exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
28451 allows trap-and-terminate (either default implementation behavior or user replacement for
28452 it) or trap-and-resume, at the programmer's option.
28455 <p><small><a href="#Contents">Contents</a></small>
28456 <h2><a name="I" href="#I">Annex I</a></h2>
28461 <p><a name="Ip1" href="#Ip1"><small>1</small></a>
28462 An implementation may generate warnings in many situations, none of which are
28463 specified as part of this International Standard. The following are a few of the more
28465 <p><a name="Ip2" href="#Ip2"><small>2</small></a>
28467 <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>).
28468 <li> A block with initialization of an object that has automatic storage duration is jumped
28469 into (<a href="#6.2.4">6.2.4</a>).
28470 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
28471 int or a double to an int, or a pointer to void to a pointer to any type other than
28472 a character type (<a href="#6.3">6.3</a>).
28473 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
28474 (<a href="#6.4.4.2">6.4.4.2</a>).
28475 <li> An integer character constant includes more than one character or a wide character
28476 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
28477 <li> The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
28478 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
28479 lvalue in one operand, and a side effect to, or an access to the value of, the identical
28480 lvalue in the other operand (<a href="#6.5">6.5</a>).
28481 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
28482 <li> The arguments in a function call do not agree in number and type with those of the
28483 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
28484 <li> An object is defined but not used (<a href="#6.7">6.7</a>).
28485 <li> A value is given to an object of an enumerated type other than by assignment of an
28486 enumeration constant that is a member of that type, or an enumeration object that has
28487 the same type, or the value of a function that returns the same enumerated type
28488 (<a href="#6.7.2.2">6.7.2.2</a>).
28489 <li> An aggregate has a partly bracketed initialization (<a href="#6.7.8">6.7.8</a>).
28490 <li> A statement cannot be reached (<a href="#6.8">6.8</a>).
28491 <li> A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
28492 <li> A constant expression is used as the controlling expression of a selection statement
28493 (<a href="#6.8.4">6.8.4</a>).
28495 <li> An incorrectly formed preprocessing group is encountered while skipping a
28496 preprocessing group (<a href="#6.10.1">6.10.1</a>).
28497 <li> An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
28501 <p><small><a href="#Contents">Contents</a></small>
28502 <h2><a name="J" href="#J">Annex J</a></h2>
28507 <p><a name="Jp1" href="#Jp1"><small>1</small></a>
28508 This annex collects some information about portability that appears in this International
28511 <p><small><a href="#Contents">Contents</a></small>
28512 <h3><a name="J.1" href="#J.1">J.1 Unspecified behavior</a></h3>
28513 <p><a name="J.1p1" href="#J.1p1"><small>1</small></a>
28514 The following are unspecified:
28516 <li> The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
28517 <li> The termination status returned to the hosted environment if the return type of main
28518 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
28519 <li> The values of objects that are neither lock-free atomic objects nor of type volatile
28520 sig_atomic_t and the state of the floating-point environment, when the
28521 processing of the abstract machine is interrupted by receipt of a signal (<a href="#5.1.2.3">5.1.2.3</a>).
28522 <li> The behavior of the display device if a printing character is written when the active
28523 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
28524 <li> The behavior of the display device if a backspace character is written when the active
28525 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
28526 <li> The behavior of the display device if a horizontal tab character is written when the
28527 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
28528 <li> The behavior of the display device if a vertical tab character is written when the active
28529 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
28530 <li> How an extended source character that does not correspond to a universal character
28531 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
28532 <li> Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
28533 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
28534 <li> The values of bytes that correspond to union members other than the one last stored
28535 into (<a href="#6.2.6.1">6.2.6.1</a>).
28536 <li> The representation used when storing a value in an object that has more than one
28537 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
28538 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
28539 <li> Whether certain operators can generate negative zeros and whether a negative zero
28540 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
28542 <li> Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
28543 <li> The order in which subexpressions are evaluated and the order in which side effects
28544 take place, except as specified for the function-call (), &&, ||, ? :, and comma
28545 operators (<a href="#6.5">6.5</a>).
28546 <li> The order in which the function designator, arguments, and subexpressions within the
28547 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
28548 <li> The order of side effects among compound literal initialization list expressions
28549 (<a href="#6.5.2.5">6.5.2.5</a>).
28550 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
28551 <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>).
28552 <li> Whether a call to an inline function uses the inline definition or the external definition
28553 of the function (<a href="#6.7.4">6.7.4</a>).
28554 <li> Whether or not a size expression is evaluated when it is part of the operand of a
28555 sizeof operator and changing the value of the size expression would not affect the
28556 result of the operator (<a href="#6.7.6.2">6.7.6.2</a>).
28557 <li> The order in which any side effects occur among the initialization list expressions in
28558 an initializer (<a href="#6.7.9">6.7.9</a>).
28559 <li> The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
28560 <li> When a fully expanded macro replacement list contains a function-like macro name
28561 as its last preprocessing token and the next preprocessing token from the source file is
28562 a (, and the fully expanded replacement of that macro ends with the name of the first
28563 macro and the next preprocessing token from the source file is again a (, whether that
28564 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
28565 <li> The order in which # and ## operations are evaluated during macro substitution
28566 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
28567 <li> The state of the floating-point status flags when execution passes from a part of the
28568 program translated with FENV_ACCESS ''off'' to a part translated with
28569 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
28570 <li> The order in which feraiseexcept raises floating-point exceptions, except as
28571 stated in <a href="#F.8.6">F.8.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
28572 <li> Whether math_errhandling is a macro or an identifier with external linkage
28573 (<a href="#7.12">7.12</a>).
28574 <li> The results of the frexp functions when the specified value is not a floating-point
28575 number (<a href="#7.12.6.4">7.12.6.4</a>).
28577 <li> The numeric result of the ilogb functions when the correct value is outside the
28578 range of the return type (<a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.10.3.5">F.10.3.5</a>).
28579 <li> The result of rounding when the value is out of range (<a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.5">F.10.6.5</a>).
28580 <li> The value stored by the remquo functions in the object pointed to by quo when y is
28581 zero (<a href="#7.12.10.3">7.12.10.3</a>).
28582 <li> Whether a comparison macro argument that is represented in a format wider than its
28583 semantic type is converted to the semantic type (<a href="#7.12.14">7.12.14</a>).
28584 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
28585 <li> Whether va_copy and va_end are macros or identifiers with external linkage
28586 (<a href="#7.16.1">7.16.1</a>).
28587 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
28588 number is printed with an a or A conversion specifier (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
28589 <li> The value of the file position indicator after a successful call to the ungetc function
28590 for a text stream, or the ungetwc function for any stream, until all pushed-back
28591 characters are read or discarded (<a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.29.3.10">7.29.3.10</a>).
28592 <li> The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
28593 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.21.9.4">7.21.9.4</a>).
28594 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
28595 functions convert a minus-signed sequence to a negative number directly or by
28596 negating the value resulting from converting the corresponding unsigned sequence
28597 (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>).
28598 <li> The order and contiguity of storage allocated by successive calls to the calloc,
28599 malloc, and realloc functions (<a href="#7.22.3">7.22.3</a>).
28600 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
28601 realloc function when 0 bytes was requested (<a href="#7.22.3">7.22.3</a>).
28602 <li> Whether a call to the atexit function that does not happen before the exit
28603 function is called will succeed (<a href="#7.22.4.2">7.22.4.2</a>).
28604 <li> Whether a call to the at_quick_exit function that does not happen before the
28605 quick_exit function is called will succeed (<a href="#7.22.4.3">7.22.4.3</a>).
28606 <li> Which of two elements that compare as equal is matched by the bsearch function
28607 (<a href="#7.22.5.1">7.22.5.1</a>).
28608 <li> The order of two elements that compare as equal in an array sorted by the qsort
28609 function (<a href="#7.22.5.2">7.22.5.2</a>).
28611 <li> The encoding of the calendar time returned by the time function (<a href="#7.27.2.4">7.27.2.4</a>).
28612 <li> The characters stored by the strftime or wcsftime function if any of the time
28613 values being converted is outside the normal range (<a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.5.1">7.29.5.1</a>).
28614 <li> Whether an encoding error occurs if a wchar_t value that does not correspond to a
28615 member of the extended character set appears in the format string for a function in
28616 <a href="#7.29.2">7.29.2</a> or <a href="#7.29.5">7.29.5</a> and the specified semantics do not require that value to be processed
28617 by wcrtomb (<a href="#7.29.1">7.29.1</a>).
28618 <li> The conversion state after an encoding error occurs (<a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>,
28619 <a href="#7.29.6.4.2">7.29.6.4.2</a>,
28620 <li> The resulting value when the ''invalid'' floating-point exception is raised during
28621 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
28622 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
28623 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
28624 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
28625 exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
28626 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
28627 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
28628 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
28629 <li> The numeric result returned by the lrint, llrint, lround, and llround
28630 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
28631 <a href="#F.10.6.7">F.10.6.7</a>).
28632 <li> The sign of one part of the complex result of several math functions for certain
28633 special cases in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>, <a href="#G.6.2.3">G.6.2.3</a>,
28634 <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>).
28637 <p><small><a href="#Contents">Contents</a></small>
28638 <h3><a name="J.2" href="#J.2">J.2 Undefined behavior</a></h3>
28639 <p><a name="J.2p1" href="#J.2p1"><small>1</small></a>
28640 The behavior is undefined in the following circumstances:
28642 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
28644 <li> A nonempty source file does not end in a new-line character which is not immediately
28645 preceded by a backslash character or ends in a partial preprocessing token or
28646 comment (<a href="#5.1.1.2">5.1.1.2</a>).
28647 <li> Token concatenation produces a character sequence matching the syntax of a
28648 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
28649 <li> A program in a hosted environment does not define a function named main using one
28650 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
28652 <li> The execution of a program contains a data race (<a href="#5.1.2.4">5.1.2.4</a>).
28653 <li> A character not in the basic source character set is encountered in a source file, except
28654 in an identifier, a character constant, a string literal, a header name, a comment, or a
28655 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
28656 <li> An identifier, comment, string literal, character constant, or header name contains an
28657 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>).
28658 <li> The same identifier has both internal and external linkage in the same translation unit
28659 (<a href="#6.2.2">6.2.2</a>).
28660 <li> An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
28661 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
28662 <li> The value of an object with automatic storage duration is used while it is
28663 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.8">6.8</a>).
28664 <li> A trap representation is read by an lvalue expression that does not have character type
28665 (<a href="#6.2.6.1">6.2.6.1</a>).
28666 <li> A trap representation is produced by a side effect that modifies any part of the object
28667 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
28668 <li> The operands to certain operators are such that they could produce a negative zero
28669 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
28670 <li> Two declarations of the same object or function specify types that are not compatible
28671 (<a href="#6.2.7">6.2.7</a>).
28672 <li> A program requires the formation of a composite type from a variable length array
28673 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
28674 <li> Conversion to or from an integer type produces a value outside the range that can be
28675 represented (<a href="#6.3.1.4">6.3.1.4</a>).
28676 <li> Demotion of one real floating type to another produces a value outside the range that
28677 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
28678 <li> An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
28679 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
28680 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
28681 <li> An lvalue designating an object of automatic storage duration that could have been
28682 declared with the register storage class is used in a context that requires the value
28683 of the designated object, but the object is uninitialized. (<a href="#6.3.2.1">6.3.2.1</a>).
28684 <li> An lvalue having array type is converted to a pointer to the initial element of the
28685 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
28687 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
28688 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
28689 <li> Conversion of a pointer to an integer type produces a value outside the range that can
28690 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
28691 <li> Conversion between two pointer types produces a result that is incorrectly aligned
28692 (<a href="#6.3.2.3">6.3.2.3</a>).
28693 <li> A pointer is used to call a function whose type is not compatible with the referenced
28694 type (<a href="#6.3.2.3">6.3.2.3</a>).
28695 <li> An unmatched ' or " character is encountered on a logical source line during
28696 tokenization (<a href="#6.4">6.4</a>).
28697 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
28698 than as a keyword (<a href="#6.4.1">6.4.1</a>).
28699 <li> A universal character name in an identifier does not designate a character whose
28700 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
28701 <li> The initial character of an identifier is a universal character name designating a digit
28702 (<a href="#6.4.2.1">6.4.2.1</a>).
28703 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
28704 <li> The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
28705 <li> The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
28706 <li> The characters ', \, ", //, or /* occur in the sequence between the < and >
28707 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
28708 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
28709 <li> A side effect on a scalar object is unsequenced relative to either a different side effect
28710 on the same scalar object or a value computation using the value of the same scalar
28711 object (<a href="#6.5">6.5</a>).
28712 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
28713 <li> An object has its stored value accessed other than by an lvalue of an allowable type
28714 (<a href="#6.5">6.5</a>).
28715 <li> For a call to a function without a function prototype in scope, the number of
28716 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
28717 <li> For call to a function without a function prototype in scope where the function is
28718 defined with a function prototype, either the prototype ends with an ellipsis or the
28719 types of the arguments after promotion are not compatible with the types of the
28720 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
28722 <li> For a call to a function without a function prototype in scope where the function is not
28723 defined with a function prototype, the types of the arguments after promotion are not
28724 compatible with those of the parameters after promotion (with certain exceptions)
28725 (<a href="#6.5.2.2">6.5.2.2</a>).
28726 <li> A function is defined with a type that is not compatible with the type (of the
28727 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
28728 <li> A member of an atomic structure or union is accessed (<a href="#6.5.2.3">6.5.2.3</a>).
28729 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
28730 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
28731 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
28732 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
28733 integer type produces a result that does not point into, or just beyond, the same array
28734 object (<a href="#6.5.6">6.5.6</a>).
28735 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
28736 integer type produces a result that points just beyond the array object and is used as
28737 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
28738 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
28739 (<a href="#6.5.6">6.5.6</a>).
28740 <li> An array subscript is out of range, even if an object is apparently accessible with the
28741 given subscript (as in the lvalue expression a[1][7] given the declaration int
28742 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
28743 <li> The result of subtracting two pointers is not representable in an object of type
28744 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
28745 <li> An expression is shifted by a negative number or by an amount greater than or equal
28746 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
28747 <li> An expression having signed promoted type is left-shifted and either the value of the
28748 expression is negative or the result of shifting would be not be representable in the
28749 promoted type (<a href="#6.5.7">6.5.7</a>).
28750 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
28751 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
28752 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
28753 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
28754 <li> An expression that is required to be an integer constant expression does not have an
28755 integer type; has operands that are not integer constants, enumeration constants,
28756 character constants, sizeof expressions whose results are integer constants,
28758 _Alignof expressions, or immediately-cast floating constants; or contains casts
28759 (outside operands to sizeof and _Alignof operators) other than conversions of
28760 arithmetic types to integer types (<a href="#6.6">6.6</a>).
28761 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
28762 following: an arithmetic constant expression, a null pointer constant, an address
28763 constant, or an address constant for a complete object type plus or minus an integer
28764 constant expression (<a href="#6.6">6.6</a>).
28765 <li> An arithmetic constant expression does not have arithmetic type; has operands that
28766 are not integer constants, floating constants, enumeration constants, character
28767 constants, sizeof expressions whose results are integer constants, or _Alignof
28768 expressions; or contains casts (outside operands to sizeof or _Alignof operators)
28769 other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
28770 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
28771 address &, or indirection * operator or a pointer cast in creating an address constant
28772 (<a href="#6.6">6.6</a>).
28773 <li> An identifier for an object is declared with no linkage and the type of the object is
28774 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
28775 <li> A function is declared at block scope with an explicit storage-class specifier other
28776 than extern (<a href="#6.7.1">6.7.1</a>).
28777 <li> A structure or union is defined without any named members (including those
28778 specified indirectly via anonymous structures and unions) (<a href="#6.7.2.1">6.7.2.1</a>).
28779 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
28780 member of a structure when the referenced object provides no elements for that array
28781 (<a href="#6.7.2.1">6.7.2.1</a>).
28782 <li> When the complete type is needed, an incomplete structure or union type is not
28783 completed in the same scope by another declaration of the tag that defines the content
28784 (<a href="#6.7.2.3">6.7.2.3</a>).
28785 <li> An attempt is made to modify an object defined with a const-qualified type through
28786 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
28787 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
28788 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
28789 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
28790 <li> Two qualified types that are required to be compatible do not have the identically
28791 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
28792 <li> An object which has been modified is accessed through a restrict-qualified pointer to
28793 a const-qualified type, or through a restrict-qualified pointer and another pointer that
28795 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
28796 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
28797 whose associated block neither began execution before the block associated with this
28798 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
28799 <li> A function with external linkage is declared with an inline function specifier, but is
28800 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
28801 <li> A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
28802 <li> The definition of an object has an alignment specifier and another declaration of that
28803 object has a different alignment specifier (<a href="#6.7.5">6.7.5</a>).
28804 <li> Declarations of an object in different translation units have different alignment
28805 specifiers (<a href="#6.7.5">6.7.5</a>).
28806 <li> Two pointer types that are required to be compatible are not identically qualified, or
28807 are not pointers to compatible types (<a href="#6.7.6.1">6.7.6.1</a>).
28808 <li> The size expression in an array declaration is not a constant expression and evaluates
28809 at program execution time to a nonpositive value (<a href="#6.7.6.2">6.7.6.2</a>).
28810 <li> In a context requiring two array types to be compatible, they do not have compatible
28811 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
28812 <li> A declaration of an array parameter includes the keyword static within the [ and
28813 ] and the corresponding argument does not provide access to the first element of an
28814 array with at least the specified number of elements (<a href="#6.7.6.3">6.7.6.3</a>).
28815 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
28816 parameter type list (<a href="#6.7.6.3">6.7.6.3</a>).
28817 <li> In a context requiring two function types to be compatible, they do not have
28818 compatible return types, or their parameters disagree in use of the ellipsis terminator
28819 or the number and type of parameters (after default argument promotion, when there
28820 is no parameter type list or when one type is specified by a function definition with an
28821 identifier list) (<a href="#6.7.6.3">6.7.6.3</a>).
28822 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
28823 <li> The initializer for a scalar is neither a single expression nor a single expression
28824 enclosed in braces (<a href="#6.7.9">6.7.9</a>).
28825 <li> The initializer for a structure or union object that has automatic storage duration is
28826 neither an initializer list nor a single expression that has compatible structure or union
28827 type (<a href="#6.7.9">6.7.9</a>).
28828 <li> The initializer for an aggregate or union, other than an array initialized by a string
28829 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
28831 <li> An identifier with external linkage is used, but in the program there does not exist
28832 exactly one external definition for the identifier, or the identifier is not used and there
28833 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
28834 <li> A function definition includes an identifier list, but the types of the parameters are not
28835 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
28836 <li> An adjusted parameter type in a function definition is not a complete object type
28837 (<a href="#6.9.1">6.9.1</a>).
28838 <li> A function that accepts a variable number of arguments is defined without a
28839 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
28840 <li> The } that terminates a function is reached, and the value of the function call is used
28841 by the caller (<a href="#6.9.1">6.9.1</a>).
28842 <li> An identifier for an object with internal linkage and an incomplete type is declared
28843 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
28844 <li> The token defined is generated during the expansion of a #if or #elif
28845 preprocessing directive, or the use of the defined unary operator does not match
28846 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
28847 <li> The #include preprocessing directive that results after expansion does not match
28848 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
28849 <li> The character sequence in an #include preprocessing directive does not start with a
28850 letter (<a href="#6.10.2">6.10.2</a>).
28851 <li> There are sequences of preprocessing tokens within the list of macro arguments that
28852 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
28853 <li> The result of the preprocessing operator # is not a valid character string literal
28854 (<a href="#6.10.3.2">6.10.3.2</a>).
28855 <li> The result of the preprocessing operator ## is not a valid preprocessing token
28856 (<a href="#6.10.3.3">6.10.3.3</a>).
28857 <li> The #line preprocessing directive that results after expansion does not match one of
28858 the two well-defined forms, or its digit sequence specifies zero or a number greater
28859 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
28860 <li> A non-STDC #pragma preprocessing directive that is documented as causing
28861 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
28862 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
28863 forms (<a href="#6.10.6">6.10.6</a>).
28864 <li> The name of a predefined macro, or the identifier defined, is the subject of a
28865 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
28867 <li> An attempt is made to copy an object to an overlapping object by use of a library
28868 function, other than as explicitly allowed (e.g., memmove) (clause 7).
28869 <li> A file with the same name as one of the standard headers, not provided as part of the
28870 implementation, is placed in any of the standard places that are searched for included
28871 source files (<a href="#7.1.2">7.1.2</a>).
28872 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
28873 <li> A function, object, type, or macro that is specified as being declared or defined by
28874 some standard header is used before any header that declares or defines it is included
28875 (<a href="#7.1.2">7.1.2</a>).
28876 <li> A standard header is included while a macro is defined with the same name as a
28877 keyword (<a href="#7.1.2">7.1.2</a>).
28878 <li> The program attempts to declare a library function itself, rather than via a standard
28879 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
28880 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
28881 (<a href="#7.1.3">7.1.3</a>).
28882 <li> The program removes the definition of a macro whose name begins with an
28883 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
28884 <li> An argument to a library function has an invalid value or a type not expected by a
28885 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
28886 <li> The pointer passed to a library function array parameter does not have a value such
28887 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
28888 <li> The macro definition of assert is suppressed in order to access an actual function
28889 (<a href="#7.2">7.2</a>).
28890 <li> The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
28891 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
28892 any context other than outside all external declarations or preceding all explicit
28893 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>).
28894 <li> The value of an argument to a character handling function is neither equal to the value
28895 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
28896 <li> A macro definition of errno is suppressed in order to access an actual object, or the
28897 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
28898 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
28899 or runs under non-default mode settings, but was translated with the state for the
28900 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
28902 <li> The exception-mask argument for one of the functions that provide access to the
28903 floating-point status flags has a nonzero value not obtained by bitwise OR of the
28904 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
28905 <li> The fesetexceptflag function is used to set floating-point status flags that were
28906 not specified in the call to the fegetexceptflag function that provided the value
28907 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
28908 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
28909 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>).
28910 <li> The value of the result of an integer arithmetic or conversion function cannot be
28911 represented (<a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.22.6.1">7.22.6.1</a>, <a href="#7.22.6.2">7.22.6.2</a>, <a href="#7.22.1">7.22.1</a>).
28912 <li> The program modifies the string pointed to by the value returned by the setlocale
28913 function (<a href="#7.11.1.1">7.11.1.1</a>).
28914 <li> The program modifies the structure pointed to by the value returned by the
28915 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
28916 <li> A macro definition of math_errhandling is suppressed or the program defines
28917 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
28918 <li> An argument to a floating-point classification or comparison macro is not of real
28919 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
28920 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
28921 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
28922 <li> An invocation of the setjmp macro occurs other than in an allowed context
28923 (<a href="#7.13.2.1">7.13.2.1</a>).
28924 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
28925 <li> After a longjmp, there is an attempt to access the value of an object of automatic
28926 storage duration that does not have volatile-qualified type, local to the function
28927 containing the invocation of the corresponding setjmp macro, that was changed
28928 between the setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
28929 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
28930 <li> A signal handler returns when the signal corresponded to a computational exception
28931 (<a href="#7.14.1.1">7.14.1.1</a>).
28932 <li> A signal handler called in response to SIGFPE, SIGILL, SIGSEGV, or any other
28933 implementation-defined value corresponding to a computational exception returns
28934 (<a href="#7.14.1.1">7.14.1.1</a>).
28935 <li> A signal occurs as the result of calling the abort or raise function, and the signal
28936 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
28938 <li> A signal occurs other than as the result of calling the abort or raise function, and
28939 the signal handler refers to an object with static or thread storage duration that is not a
28940 lock-free atomic object other than by assigning a value to an object declared as
28941 volatile sig_atomic_t, or calls any function in the standard library other
28942 than the abort function, the _Exit function, the quick_exit function, or the
28943 signal function (for the same signal number) (<a href="#7.14.1.1">7.14.1.1</a>).
28944 <li> The value of errno is referred to after a signal occurred other than as the result of
28945 calling the abort or raise function and the corresponding signal handler obtained
28946 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
28947 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
28948 <li> The signal function is used in a multi-threaded program (<a href="#7.14.1.1">7.14.1.1</a>).
28949 <li> A function with a variable number of arguments attempts to access its varying
28950 arguments other than through a properly declared and initialized va_list object, or
28951 before the va_start macro is invoked (<a href="#7.16">7.16</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#7.16.1.4">7.16.1.4</a>).
28952 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
28953 that invoked the macro va_arg with the same parameter (<a href="#7.16">7.16</a>).
28954 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
28955 order to access an actual function, or the program defines an external identifier with
28956 the name va_copy or va_end (<a href="#7.16.1">7.16.1</a>).
28957 <li> The va_start or va_copy macro is invoked without a corresponding invocation
28958 of the va_end macro in the same function, or vice versa (<a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>,
28959 <a href="#7.16.1.4">7.16.1.4</a>).
28960 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
28961 that type can be obtained simply by postfixing a * (<a href="#7.16.1.1">7.16.1.1</a>).
28962 <li> The va_arg macro is invoked when there is no actual next argument, or with a
28963 specified type that is not compatible with the promoted type of the actual next
28964 argument, with certain exceptions (<a href="#7.16.1.1">7.16.1.1</a>).
28965 <li> The va_copy or va_start macro is called to initialize a va_list that was
28966 previously initialized by either macro without an intervening invocation of the
28967 va_end macro for the same va_list (<a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.4">7.16.1.4</a>).
28968 <li> The parameter parmN of a va_start macro is declared with the register
28969 storage class, with a function or array type, or with a type that is not compatible with
28970 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
28971 <li> The member designator parameter of an offsetof macro is an invalid right
28972 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
28974 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
28975 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
28976 corresponding type (<a href="#7.20.4">7.20.4</a>).
28977 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
28978 input/output function is applied to a byte-oriented stream (<a href="#7.21.2">7.21.2</a>).
28979 <li> Use is made of any portion of a file beyond the most recent wide character written to
28980 a wide-oriented stream (<a href="#7.21.2">7.21.2</a>).
28981 <li> The value of a pointer to a FILE object is used after the associated file is closed
28982 (<a href="#7.21.3">7.21.3</a>).
28983 <li> The stream for the fflush function points to an input stream or to an update stream
28984 in which the most recent operation was input (<a href="#7.21.5.2">7.21.5.2</a>).
28985 <li> The string pointed to by the mode argument in a call to the fopen function does not
28986 exactly match one of the specified character sequences (<a href="#7.21.5.3">7.21.5.3</a>).
28987 <li> An output operation on an update stream is followed by an input operation without an
28988 intervening call to the fflush function or a file positioning function, or an input
28989 operation on an update stream is followed by an output operation with an intervening
28990 call to a file positioning function (<a href="#7.21.5.3">7.21.5.3</a>).
28991 <li> An attempt is made to use the contents of the array that was supplied in a call to the
28992 setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
28993 <li> There are insufficient arguments for the format in a call to one of the formatted
28994 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
28995 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
28996 <li> The format in a call to one of the formatted input/output functions or to the
28997 strftime or wcsftime function is not a valid multibyte character sequence that
28998 begins and ends in its initial shift state (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>,
28999 <a href="#7.29.5.1">7.29.5.1</a>).
29000 <li> In a call to one of the formatted output functions, a precision appears with a
29001 conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29002 <li> A conversion specification for a formatted output function uses an asterisk to denote
29003 an argument-supplied field width or precision, but the corresponding argument is not
29004 provided (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29005 <li> A conversion specification for a formatted output function uses a # or 0 flag with a
29006 conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29007 <li> A conversion specification for one of the formatted input/output functions uses a
29008 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
29009 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29011 <li> An s conversion specifier is encountered by one of the formatted output functions,
29012 and the argument is missing the null terminator (unless a precision is specified that
29013 does not require null termination) (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29014 <li> An n conversion specification for one of the formatted input/output functions includes
29015 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
29016 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29017 <li> A % conversion specifier is encountered by one of the formatted input/output
29018 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
29019 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29020 <li> An invalid conversion specification is found in the format for one of the formatted
29021 input/output functions, or the strftime or wcsftime function (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
29022 <a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.5.1">7.29.5.1</a>).
29023 <li> The number of characters or wide characters transmitted by a formatted output
29024 function (or written to an array, or that would have been written to an array) is greater
29025 than INT_MAX (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29026 <li> The number of input items assigned by a formatted input function is greater than
29027 INT_MAX (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29028 <li> The result of a conversion by one of the formatted input functions cannot be
29029 represented in the corresponding object, or the receiving object does not have an
29030 appropriate type (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29031 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
29032 functions, and the array pointed to by the corresponding argument is not large enough
29033 to accept the input sequence (and a null terminator if the conversion specifier is s or
29034 [) (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29035 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
29036 formatted input functions, but the input is not a valid multibyte character sequence
29037 that begins in the initial shift state (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29038 <li> The input item for a %p conversion by one of the formatted input functions is not a
29039 value converted earlier during the same program execution (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29040 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
29041 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
29042 vwscanf function is called with an improperly initialized va_list argument, or
29043 the argument is used (other than in an invocation of va_end) after the function
29044 returns (<a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>,
29045 <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>).
29046 <li> The contents of the array supplied in a call to the fgets or fgetws function are
29047 used after a read error occurred (<a href="#7.21.7.2">7.21.7.2</a>, <a href="#7.29.3.2">7.29.3.2</a>).
29049 <li> The file position indicator for a binary stream is used after a call to the ungetc
29050 function where its value was zero before the call (<a href="#7.21.7.10">7.21.7.10</a>).
29051 <li> The file position indicator for a stream is used after an error occurred during a call to
29052 the fread or fwrite function (<a href="#7.21.8.1">7.21.8.1</a>, <a href="#7.21.8.2">7.21.8.2</a>).
29053 <li> A partial element read by a call to the fread function is used (<a href="#7.21.8.1">7.21.8.1</a>).
29054 <li> The fseek function is called for a text stream with a nonzero offset and either the
29055 offset was not returned by a previous successful call to the ftell function on a
29056 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
29057 <li> The fsetpos function is called to set a position that was not returned by a previous
29058 successful call to the fgetpos function on a stream associated with the same file
29059 (<a href="#7.21.9.3">7.21.9.3</a>).
29060 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
29061 with a zero requested size is used to access an object (<a href="#7.22.3">7.22.3</a>).
29062 <li> The value of a pointer that refers to space deallocated by a call to the free or
29063 realloc function is used (<a href="#7.22.3">7.22.3</a>).
29064 <li> The alignment requested of the aligned_alloc function is not valid or not
29065 supported by the implementation, or the size requested is not an integral multiple of
29066 the alignment (<a href="#7.22.3.1">7.22.3.1</a>).
29067 <li> The pointer argument to the free or realloc function does not match a pointer
29068 earlier returned by a memory management function, or the space has been deallocated
29069 by a call to free or realloc (<a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a>).
29070 <li> The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
29071 <li> The value of any bytes in a new object allocated by the realloc function beyond
29072 the size of the old object are used (<a href="#7.22.3.5">7.22.3.5</a>).
29073 <li> The program calls the exit or quick_exit function more than once, or calls both
29074 functions (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
29075 <li> During the call to a function registered with the atexit or at_quick_exit
29076 function, a call is made to the longjmp function that would terminate the call to the
29077 registered function (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
29078 <li> The string set up by the getenv or strerror function is modified by the program
29079 (<a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.24.6.2">7.24.6.2</a>).
29080 <li> A signal is raised while the quick_exit function is executing (<a href="#7.22.4.7">7.22.4.7</a>).
29081 <li> A command is executed through the system function in a way that is documented as
29082 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
29084 <li> A searching or sorting utility function is called with an invalid pointer argument, even
29085 if the number of elements is zero (<a href="#7.22.5">7.22.5</a>).
29086 <li> The comparison function called by a searching or sorting utility function alters the
29087 contents of the array being searched or sorted, or returns ordering values
29088 inconsistently (<a href="#7.22.5">7.22.5</a>).
29089 <li> The array being searched by the bsearch function does not have its elements in
29090 proper order (<a href="#7.22.5.1">7.22.5.1</a>).
29091 <li> The current conversion state is used by a multibyte/wide character conversion
29092 function after changing the LC_CTYPE category (<a href="#7.22.7">7.22.7</a>).
29093 <li> A string or wide string utility function is instructed to access an array beyond the end
29094 of an object (<a href="#7.24.1">7.24.1</a>, <a href="#7.29.4">7.29.4</a>).
29095 <li> A string or wide string utility function is called with an invalid pointer argument, even
29096 if the length is zero (<a href="#7.24.1">7.24.1</a>, <a href="#7.29.4">7.29.4</a>).
29097 <li> The contents of the destination array are used after a call to the strxfrm,
29098 strftime, wcsxfrm, or wcsftime function in which the specified length was
29099 too small to hold the entire null-terminated result (<a href="#7.24.4.5">7.24.4.5</a>, <a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.4.4.4">7.29.4.4.4</a>,
29100 <a href="#7.29.5.1">7.29.5.1</a>).
29101 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
29102 (<a href="#7.24.5.8">7.24.5.8</a>, <a href="#7.29.4.5.7">7.29.4.5.7</a>).
29103 <li> The type of an argument to a type-generic macro is not compatible with the type of
29104 the corresponding parameter of the selected function (<a href="#7.25">7.25</a>).
29105 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
29106 has no corresponding complex function (<a href="#7.25">7.25</a>).
29107 <li> At least one member of the broken-down time passed to asctime contains a value
29108 outside its normal range, or the calculated year exceeds four digits or is less than the
29109 year 1000 (<a href="#7.27.3.1">7.27.3.1</a>).
29110 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
29111 fwprintf function does not point to a valid multibyte character sequence that
29112 begins in the initial shift state (<a href="#7.29.2.11">7.29.2.11</a>).
29113 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
29114 value stored by the previous call for the same wide string (<a href="#7.29.4.5.7">7.29.4.5.7</a>).
29115 <li> An mbstate_t object is used inappropriately (<a href="#7.29.6">7.29.6</a>).
29116 <li> The value of an argument of type wint_t to a wide character classification or case
29117 mapping function is neither equal to the value of WEOF nor representable as a
29118 wchar_t (<a href="#7.30.1">7.30.1</a>).
29120 <li> The iswctype function is called using a different LC_CTYPE category from the
29121 one in effect for the call to the wctype function that returned the description
29122 (<a href="#7.30.2.2.1">7.30.2.2.1</a>).
29123 <li> The towctrans function is called using a different LC_CTYPE category from the
29124 one in effect for the call to the wctrans function that returned the description
29125 (<a href="#7.30.3.2.1">7.30.3.2.1</a>).
29128 <p><small><a href="#Contents">Contents</a></small>
29129 <h3><a name="J.3" href="#J.3">J.3 Implementation-defined behavior</a></h3>
29130 <p><a name="J.3p1" href="#J.3p1"><small>1</small></a>
29131 A conforming implementation is required to document its choice of behavior in each of
29132 the areas listed in this subclause. The following are implementation-defined:
29134 <p><small><a href="#Contents">Contents</a></small>
29135 <h4><a name="J.3.1" href="#J.3.1">J.3.1 Translation</a></h4>
29136 <p><a name="J.3.1p1" href="#J.3.1p1"><small>1</small></a>
29138 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
29139 <li> Whether each nonempty sequence of white-space characters other than new-line is
29140 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
29143 <p><small><a href="#Contents">Contents</a></small>
29144 <h4><a name="J.3.2" href="#J.3.2">J.3.2 Environment</a></h4>
29145 <p><a name="J.3.2p1" href="#J.3.2p1"><small>1</small></a>
29147 <li> The mapping between physical source file multibyte characters and the source
29148 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
29149 <li> The name and type of the function called at program startup in a freestanding
29150 environment (<a href="#5.1.2.1">5.1.2.1</a>).
29151 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
29152 <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>).
29153 <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>).
29154 <li> What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
29155 <li> Whether a program can have more than one thread of execution in a freestanding
29156 environment (<a href="#5.1.2.4">5.1.2.4</a>).
29157 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
29158 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
29159 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
29160 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
29161 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
29162 <li> The set of environment names and the method for altering the environment list used
29163 by the getenv function (<a href="#7.22.4.6">7.22.4.6</a>).
29164 <li> The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
29168 <p><small><a href="#Contents">Contents</a></small>
29169 <h4><a name="J.3.3" href="#J.3.3">J.3.3 Identifiers</a></h4>
29170 <p><a name="J.3.3p1" href="#J.3.3p1"><small>1</small></a>
29172 <li> Which additional multibyte characters may appear in identifiers and their
29173 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
29174 <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>).
29177 <p><small><a href="#Contents">Contents</a></small>
29178 <h4><a name="J.3.4" href="#J.3.4">J.3.4 Characters</a></h4>
29179 <p><a name="J.3.4p1" href="#J.3.4p1"><small>1</small></a>
29181 <li> The number of bits in a byte (<a href="#3.6">3.6</a>).
29182 <li> The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
29183 <li> The unique value of the member of the execution character set produced for each of
29184 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
29185 <li> The value of a char object into which has been stored any character other than a
29186 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
29187 <li> Which of signed char or unsigned char has the same range, representation,
29188 and behavior as ''plain'' char (<a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>).
29189 <li> The mapping of members of the source character set (in character constants and string
29190 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>).
29191 <li> The value of an integer character constant containing more than one character or
29192 containing a character or escape sequence that does not map to a single-byte
29193 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
29194 <li> The value of a wide character constant containing more than one multibyte character
29195 or a single multibyte character that maps to multiple members of the extended
29196 execution character set, or containing a multibyte character or escape sequence not
29197 represented in the extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
29198 <li> The current locale used to convert a wide character constant consisting of a single
29199 multibyte character that maps to a member of the extended execution character set
29200 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
29201 <li> Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
29202 the treatment of the resulting multibyte character sequence (<a href="#6.4.5">6.4.5</a>).
29203 <li> The current locale used to convert a wide string literal into corresponding wide
29204 character codes (<a href="#6.4.5">6.4.5</a>).
29205 <li> The value of a string literal containing a multibyte character or escape sequence not
29206 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
29207 <li> The encoding of any of wchar_t, char16_t, and char32_t where the
29208 corresponding standard encoding macro (__STDC_ISO_10646__,
29209 __STDC_UTF_16__, or __STDC_UTF_32__) is not defined (<a href="#6.10.8.2">6.10.8.2</a>).
29213 <p><small><a href="#Contents">Contents</a></small>
29214 <h4><a name="J.3.5" href="#J.3.5">J.3.5 Integers</a></h4>
29215 <p><a name="J.3.5p1" href="#J.3.5p1"><small>1</small></a>
29217 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
29218 <li> Whether signed integer types are represented using sign and magnitude, two's
29219 complement, or ones' complement, and whether the extraordinary value is a trap
29220 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
29221 <li> The rank of any extended integer type relative to another extended integer type with
29222 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
29223 <li> The result of, or the signal raised by, converting an integer to a signed integer type
29224 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
29225 <li> The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
29228 <p><small><a href="#Contents">Contents</a></small>
29229 <h4><a name="J.3.6" href="#J.3.6">J.3.6 Floating point</a></h4>
29230 <p><a name="J.3.6p1" href="#J.3.6p1"><small>1</small></a>
29232 <li> The accuracy of the floating-point operations and of the library functions in
29233 <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>).
29234 <li> The accuracy of the conversions between floating-point internal representations and
29235 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
29236 <a href="#7.22"><stdlib.h></a>, and <a href="#7.29"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
29237 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
29238 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
29239 <li> The evaluation methods characterized by non-standard negative values of
29240 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
29241 <li> The direction of rounding when an integer is converted to a floating-point number that
29242 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
29243 <li> The direction of rounding when a floating-point number is converted to a narrower
29244 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
29245 <li> How the nearest representable value or the larger or smaller representable value
29246 immediately adjacent to the nearest representable value is chosen for certain floating
29247 constants (<a href="#6.4.4.2">6.4.4.2</a>).
29248 <li> Whether and how floating expressions are contracted when not disallowed by the
29249 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
29250 <li> The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
29251 <li> Additional floating-point exceptions, rounding modes, environments, and
29252 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
29253 <li> The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>).
29257 <p><small><a href="#Contents">Contents</a></small>
29258 <h4><a name="J.3.7" href="#J.3.7">J.3.7 Arrays and pointers</a></h4>
29259 <p><a name="J.3.7p1" href="#J.3.7p1"><small>1</small></a>
29261 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
29262 <li> The size of the result of subtracting two pointers to elements of the same array
29263 (<a href="#6.5.6">6.5.6</a>).
29266 <p><small><a href="#Contents">Contents</a></small>
29267 <h4><a name="J.3.8" href="#J.3.8">J.3.8 Hints</a></h4>
29268 <p><a name="J.3.8p1" href="#J.3.8p1"><small>1</small></a>
29270 <li> The extent to which suggestions made by using the register storage-class
29271 specifier are effective (<a href="#6.7.1">6.7.1</a>).
29272 <li> The extent to which suggestions made by using the inline function specifier are
29273 effective (<a href="#6.7.4">6.7.4</a>).
29276 <p><small><a href="#Contents">Contents</a></small>
29277 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
29278 <p><a name="J.3.9p1" href="#J.3.9p1"><small>1</small></a>
29280 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
29281 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
29282 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
29283 (<a href="#6.7.2.1">6.7.2.1</a>).
29284 <li> Whether atomic types are permitted for bit-fields (<a href="#6.7.2.1">6.7.2.1</a>).
29285 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
29286 <li> The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
29287 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
29288 no problem unless binary data written by one implementation is read by another.
29289 <li> The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
29292 <p><small><a href="#Contents">Contents</a></small>
29293 <h4><a name="J.3.10" href="#J.3.10">J.3.10 Qualifiers</a></h4>
29294 <p><a name="J.3.10p1" href="#J.3.10p1"><small>1</small></a>
29296 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
29299 <p><small><a href="#Contents">Contents</a></small>
29300 <h4><a name="J.3.11" href="#J.3.11">J.3.11 Preprocessing directives</a></h4>
29301 <p><a name="J.3.11p1" href="#J.3.11p1"><small>1</small></a>
29303 <li> The locations within #pragma directives where header name preprocessing tokens
29304 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
29305 <li> How sequences in both forms of header names are mapped to headers or external
29306 source file names (<a href="#6.4.7">6.4.7</a>).
29307 <li> Whether the value of a character constant in a constant expression that controls
29308 conditional inclusion matches the value of the same character constant in the
29309 execution character set (<a href="#6.10.1">6.10.1</a>).
29310 <li> Whether the value of a single-character character constant in a constant expression
29311 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
29313 <li> The places that are searched for an included < > delimited header, and how the places
29314 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
29315 <li> How the named source file is searched for in an included " " delimited header
29316 (<a href="#6.10.2">6.10.2</a>).
29317 <li> The method by which preprocessing tokens (possibly resulting from macro
29318 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
29319 <li> The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
29320 <li> Whether the # operator inserts a \ character before the \ character that begins a
29321 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
29322 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
29323 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
29324 time of translation are not available (<a href="#6.10.8.1">6.10.8.1</a>).
29327 <p><small><a href="#Contents">Contents</a></small>
29328 <h4><a name="J.3.12" href="#J.3.12">J.3.12 Library functions</a></h4>
29329 <p><a name="J.3.12p1" href="#J.3.12p1"><small>1</small></a>
29331 <li> Any library facilities available to a freestanding program, other than the minimal set
29332 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
29333 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
29334 <li> The representation of the floating-point status flags stored by the
29335 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
29336 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
29337 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
29338 (<a href="#7.6.2.3">7.6.2.3</a>).
29339 <li> Strings other than "C" and "" that may be passed as the second argument to the
29340 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
29341 <li> The types defined for float_t and double_t when the value of the
29342 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
29343 <li> Domain errors for the mathematics functions, other than those required by this
29344 International Standard (<a href="#7.12.1">7.12.1</a>).
29345 <li> The values returned by the mathematics functions on domain errors or pole errors
29346 (<a href="#7.12.1">7.12.1</a>).
29347 <li> The values returned by the mathematics functions on underflow range errors, whether
29348 errno is set to the value of the macro ERANGE when the integer expression
29349 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
29350 floating-point exception is raised when the integer expression math_errhandling
29351 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
29353 <li> Whether a domain error occurs or zero is returned when an fmod function has a
29354 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
29355 <li> Whether a domain error occurs or zero is returned when a remainder function has
29356 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
29357 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
29358 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
29359 <li> Whether a domain error occurs or zero is returned when a remquo function has a
29360 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
29361 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
29362 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>).
29363 <li> The null pointer constant to which the macro NULL expands (<a href="#7.19">7.19</a>).
29364 <li> Whether the last line of a text stream requires a terminating new-line character
29365 (<a href="#7.21.2">7.21.2</a>).
29366 <li> Whether space characters that are written out to a text stream immediately before a
29367 new-line character appear when read in (<a href="#7.21.2">7.21.2</a>).
29368 <li> The number of null characters that may be appended to data written to a binary
29369 stream (<a href="#7.21.2">7.21.2</a>).
29370 <li> Whether the file position indicator of an append-mode stream is initially positioned at
29371 the beginning or end of the file (<a href="#7.21.3">7.21.3</a>).
29372 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
29373 point (<a href="#7.21.3">7.21.3</a>).
29374 <li> The characteristics of file buffering (<a href="#7.21.3">7.21.3</a>).
29375 <li> Whether a zero-length file actually exists (<a href="#7.21.3">7.21.3</a>).
29376 <li> The rules for composing valid file names (<a href="#7.21.3">7.21.3</a>).
29377 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
29378 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
29379 <li> The effect of the remove function on an open file (<a href="#7.21.4.1">7.21.4.1</a>).
29380 <li> The effect if a file with the new name exists prior to a call to the rename function
29381 (<a href="#7.21.4.2">7.21.4.2</a>).
29382 <li> Whether an open temporary file is removed upon abnormal program termination
29383 (<a href="#7.21.4.3">7.21.4.3</a>).
29384 <li> Which changes of mode are permitted (if any), and under what circumstances
29385 (<a href="#7.21.5.4">7.21.5.4</a>).
29387 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
29388 sequence printed for a NaN (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29389 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
29390 <a href="#7.29.2.1">7.29.2.1</a>).
29391 <li> The interpretation of a - character that is neither the first nor the last character, nor
29392 the second where a ^ character is the first, in the scanlist for %[ conversion in the
29393 fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29394 <li> The set of sequences matched by a %p conversion and the interpretation of the
29395 corresponding input item in the fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29396 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
29397 functions on failure (<a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.9.4">7.21.9.4</a>).
29398 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
29399 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
29400 function (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>).
29401 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
29402 function sets errno to ERANGE when underflow occurs (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>).
29403 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
29404 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
29405 <li> Whether open streams with unwritten buffered data are flushed, open streams are
29406 closed, or temporary files are removed when the abort or _Exit function is called
29407 (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.5">7.22.4.5</a>).
29408 <li> The termination status returned to the host environment by the abort, exit,
29409 _Exit, or quick_exit function (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>).
29410 <li> The value returned by the system function when its argument is not a null pointer
29411 (<a href="#7.22.4.8">7.22.4.8</a>).
29412 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.27">7.27</a>). *
29413 <li> The local time zone and Daylight Saving Time (<a href="#7.27.1">7.27.1</a>).
29414 <li> The era for the clock function (<a href="#7.27.2.1">7.27.2.1</a>).
29415 <li> The TIME_UTC epoch (<a href="#7.27.2.5">7.27.2.5</a>).
29416 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
29417 functions in the "C" locale (<a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.5.1">7.29.5.1</a>).
29418 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
29419 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
29423 <p><small><a href="#Contents">Contents</a></small>
29424 <h4><a name="J.3.13" href="#J.3.13">J.3.13 Architecture</a></h4>
29425 <p><a name="J.3.13p1" href="#J.3.13p1"><small>1</small></a>
29427 <li> The values or expressions assigned to the macros specified in the headers
29428 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.20"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.20.2">7.20.2</a>, <a href="#7.20.3">7.20.3</a>).
29429 <li> The result of attempting to indirectly access an object with automatic or thread
29430 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
29431 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
29432 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
29433 <li> Whether any extended alignments are supported and the contexts in which they are
29434 supported (<a href="#6.2.8">6.2.8</a>).
29435 <li> Valid alignment values other than those returned by an _Alignof expression for
29436 fundamental types, if any (<a href="#6.2.8">6.2.8</a>).
29437 <li> The value of the result of the sizeof and _Alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
29440 <p><small><a href="#Contents">Contents</a></small>
29441 <h3><a name="J.4" href="#J.4">J.4 Locale-specific behavior</a></h3>
29442 <p><a name="J.4p1" href="#J.4p1"><small>1</small></a>
29443 The following characteristics of a hosted environment are locale-specific and are required
29444 to be documented by the implementation:
29446 <li> Additional members of the source and execution character sets beyond the basic
29447 character set (<a href="#5.2.1">5.2.1</a>).
29448 <li> The presence, meaning, and representation of additional multibyte characters in the
29449 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
29450 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
29451 <li> The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
29452 <li> The decimal-point character (<a href="#7.1.1">7.1.1</a>).
29453 <li> The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.30.2">7.30.2</a>).
29454 <li> The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.30.2">7.30.2</a>).
29455 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
29456 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
29457 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>,
29458 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.2.1.10">7.30.2.1.10</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>).
29459 <li> The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
29460 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
29461 <a href="#7.29.4.1">7.29.4.1</a>).
29462 <li> The collation sequence of the execution character set (<a href="#7.24.4.3">7.24.4.3</a>, <a href="#7.29.4.4.2">7.29.4.4.2</a>).
29464 <li> The contents of the error message strings set up by the strerror function
29465 (<a href="#7.24.6.2">7.24.6.2</a>).
29466 <li> The formats for time and date (<a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.5.1">7.29.5.1</a>).
29467 <li> Character mappings that are supported by the towctrans function (<a href="#7.30.1">7.30.1</a>).
29468 <li> Character classifications that are supported by the iswctype function (<a href="#7.30.1">7.30.1</a>).
29471 <p><small><a href="#Contents">Contents</a></small>
29472 <h3><a name="J.5" href="#J.5">J.5 Common extensions</a></h3>
29473 <p><a name="J.5p1" href="#J.5p1"><small>1</small></a>
29474 The following extensions are widely used in many systems, but are not portable to all
29475 implementations. The inclusion of any extension that may cause a strictly conforming
29476 program to become invalid renders an implementation nonconforming. Examples of such
29477 extensions are new keywords, extra library functions declared in standard headers, or
29478 predefined macros with names that do not begin with an underscore.
29480 <p><small><a href="#Contents">Contents</a></small>
29481 <h4><a name="J.5.1" href="#J.5.1">J.5.1 Environment arguments</a></h4>
29482 <p><a name="J.5.1p1" href="#J.5.1p1"><small>1</small></a>
29483 In a hosted environment, the main function receives a third argument, char *envp[],
29484 that points to a null-terminated array of pointers to char, each of which points to a string
29485 that provides information about the environment for this execution of the program
29486 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
29488 <p><small><a href="#Contents">Contents</a></small>
29489 <h4><a name="J.5.2" href="#J.5.2">J.5.2 Specialized identifiers</a></h4>
29490 <p><a name="J.5.2p1" href="#J.5.2p1"><small>1</small></a>
29491 Characters other than the underscore _, letters, and digits, that are not part of the basic
29492 source character set (such as the dollar sign $, or characters in national character sets)
29493 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
29495 <p><small><a href="#Contents">Contents</a></small>
29496 <h4><a name="J.5.3" href="#J.5.3">J.5.3 Lengths and cases of identifiers</a></h4>
29497 <p><a name="J.5.3p1" href="#J.5.3p1"><small>1</small></a>
29498 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
29500 <p><small><a href="#Contents">Contents</a></small>
29501 <h4><a name="J.5.4" href="#J.5.4">J.5.4 Scopes of identifiers</a></h4>
29502 <p><a name="J.5.4p1" href="#J.5.4p1"><small>1</small></a>
29503 A function identifier, or the identifier of an object the declaration of which contains the
29504 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
29506 <p><small><a href="#Contents">Contents</a></small>
29507 <h4><a name="J.5.5" href="#J.5.5">J.5.5 Writable string literals</a></h4>
29508 <p><a name="J.5.5p1" href="#J.5.5p1"><small>1</small></a>
29509 String literals are modifiable (in which case, identical string literals should denote distinct
29510 objects) (<a href="#6.4.5">6.4.5</a>).
29513 <p><small><a href="#Contents">Contents</a></small>
29514 <h4><a name="J.5.6" href="#J.5.6">J.5.6 Other arithmetic types</a></h4>
29515 <p><a name="J.5.6p1" href="#J.5.6p1"><small>1</small></a>
29516 Additional arithmetic types, such as __int128 or double double, and their
29517 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
29518 more range or precision than long double, may be used for evaluating expressions of
29519 other floating types, and may be used to define float_t or double_t. Additional
29520 floating types may also have less range or precision than float.
29522 <p><small><a href="#Contents">Contents</a></small>
29523 <h4><a name="J.5.7" href="#J.5.7">J.5.7 Function pointer casts</a></h4>
29524 <p><a name="J.5.7p1" href="#J.5.7p1"><small>1</small></a>
29525 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
29526 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
29527 <p><a name="J.5.7p2" href="#J.5.7p2"><small>2</small></a>
29528 A pointer to a function may be cast to a pointer to an object or to void, allowing a
29529 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
29531 <p><small><a href="#Contents">Contents</a></small>
29532 <h4><a name="J.5.8" href="#J.5.8">J.5.8 Extended bit-field types</a></h4>
29533 <p><a name="J.5.8p1" href="#J.5.8p1"><small>1</small></a>
29534 A bit-field may be declared with a type other than _Bool, unsigned int, or
29535 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
29537 <p><small><a href="#Contents">Contents</a></small>
29538 <h4><a name="J.5.9" href="#J.5.9">J.5.9 The fortran keyword</a></h4>
29539 <p><a name="J.5.9p1" href="#J.5.9p1"><small>1</small></a>
29540 The fortran function specifier may be used in a function declaration to indicate that
29541 calls suitable for FORTRAN should be generated, or that a different representation for the
29542 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
29544 <p><small><a href="#Contents">Contents</a></small>
29545 <h4><a name="J.5.10" href="#J.5.10">J.5.10 The asm keyword</a></h4>
29546 <p><a name="J.5.10p1" href="#J.5.10p1"><small>1</small></a>
29547 The asm keyword may be used to insert assembly language directly into the translator
29548 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
29550 asm ( character-string-literal );
29553 <p><small><a href="#Contents">Contents</a></small>
29554 <h4><a name="J.5.11" href="#J.5.11">J.5.11 Multiple external definitions</a></h4>
29555 <p><a name="J.5.11p1" href="#J.5.11p1"><small>1</small></a>
29556 There may be more than one external definition for the identifier of an object, with or
29557 without the explicit use of the keyword extern; if the definitions disagree, or more than
29558 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
29561 <p><small><a href="#Contents">Contents</a></small>
29562 <h4><a name="J.5.12" href="#J.5.12">J.5.12 Predefined macro names</a></h4>
29563 <p><a name="J.5.12p1" href="#J.5.12p1"><small>1</small></a>
29564 Macro names that do not begin with an underscore, describing the translation and
29565 execution environments, are defined by the implementation before translation begins
29566 (<a href="#6.10.8">6.10.8</a>).
29568 <p><small><a href="#Contents">Contents</a></small>
29569 <h4><a name="J.5.13" href="#J.5.13">J.5.13 Floating-point status flags</a></h4>
29570 <p><a name="J.5.13p1" href="#J.5.13p1"><small>1</small></a>
29571 If any floating-point status flags are set on normal termination after all calls to functions
29572 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
29573 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
29575 <p><small><a href="#Contents">Contents</a></small>
29576 <h4><a name="J.5.14" href="#J.5.14">J.5.14 Extra arguments for signal handlers</a></h4>
29577 <p><a name="J.5.14p1" href="#J.5.14p1"><small>1</small></a>
29578 Handlers for specific signals are called with extra arguments in addition to the signal
29579 number (<a href="#7.14.1.1">7.14.1.1</a>).
29581 <p><small><a href="#Contents">Contents</a></small>
29582 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
29583 <p><a name="J.5.15p1" href="#J.5.15p1"><small>1</small></a>
29584 Additional mappings from files to streams are supported (<a href="#7.21.2">7.21.2</a>).
29585 <p><a name="J.5.15p2" href="#J.5.15p2"><small>2</small></a>
29586 Additional file-opening modes may be specified by characters appended to the mode
29587 argument of the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
29589 <p><small><a href="#Contents">Contents</a></small>
29590 <h4><a name="J.5.16" href="#J.5.16">J.5.16 Defined file position indicator</a></h4>
29591 <p><a name="J.5.16p1" href="#J.5.16p1"><small>1</small></a>
29592 The file position indicator is decremented by each successful call to the ungetc or
29593 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.21.7.10">7.21.7.10</a>,
29594 <a href="#7.29.3.10">7.29.3.10</a>).
29596 <p><small><a href="#Contents">Contents</a></small>
29597 <h4><a name="J.5.17" href="#J.5.17">J.5.17 Math error reporting</a></h4>
29598 <p><a name="J.5.17p1" href="#J.5.17p1"><small>1</small></a>
29599 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
29600 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
29601 <a href="#7.12">7.12</a>).
29604 <p><small><a href="#Contents">Contents</a></small>
29605 <h2><a name="K" href="#K">Annex K</a></h2>
29608 Bounds-checking interfaces
29611 <p><small><a href="#Contents">Contents</a></small>
29612 <h3><a name="K.1" href="#K.1">K.1 Background</a></h3>
29613 <p><a name="K.1p1" href="#K.1p1"><small>1</small></a>
29614 Traditionally, the C Library has contained many functions that trust the programmer to
29615 provide output character arrays big enough to hold the result being produced. Not only
29616 do these functions not check that the arrays are big enough, they frequently lack the
29617 information needed to perform such checks. While it is possible to write safe, robust, and
29618 error-free code using the existing library, the library tends to promote programming styles
29619 that lead to mysterious failures if a result is too big for the provided array.
29620 <p><a name="K.1p2" href="#K.1p2"><small>2</small></a>
29621 A common programming style is to declare character arrays large enough to handle most
29622 practical cases. However, if these arrays are not large enough to handle the resulting
29623 strings, data can be written past the end of the array overwriting other data and program
29624 structures. The program never gets any indication that a problem exists, and so never has
29625 a chance to recover or to fail gracefully.
29626 <p><a name="K.1p3" href="#K.1p3"><small>3</small></a>
29627 Worse, this style of programming has compromised the security of computers and
29628 networks. Buffer overflows can often be exploited to run arbitrary code with the
29629 permissions of the vulnerable (defective) program.
29630 <p><a name="K.1p4" href="#K.1p4"><small>4</small></a>
29631 If the programmer writes runtime checks to verify lengths before calling library
29632 functions, then those runtime checks frequently duplicate work done inside the library
29633 functions, which discover string lengths as a side effect of doing their job.
29634 <p><a name="K.1p5" href="#K.1p5"><small>5</small></a>
29635 This annex provides alternative library functions that promote safer, more secure
29636 programming. The alternative functions verify that output buffers are large enough for
29637 the intended result and return a failure indicator if they are not. Data is never written past
29638 the end of an array. All string results are null terminated.
29639 <p><a name="K.1p6" href="#K.1p6"><small>6</small></a>
29640 This annex also addresses another problem that complicates writing robust code:
29641 functions that are not reentrant because they return pointers to static objects owned by the
29642 function. Such functions can be troublesome since a previously returned result can
29643 change if the function is called again, perhaps by another thread.
29646 <p><small><a href="#Contents">Contents</a></small>
29647 <h3><a name="K.2" href="#K.2">K.2 Scope</a></h3>
29648 <p><a name="K.2p1" href="#K.2p1"><small>1</small></a>
29649 This annex specifies a series of optional extensions that can be useful in the mitigation of
29650 security vulnerabilities in programs, and comprise new functions, macros, and types
29651 declared or defined in existing standard headers.
29652 <p><a name="K.2p2" href="#K.2p2"><small>2</small></a>
29653 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
29654 specifications in this annex.<sup><a href="#note380"><b>380)</b></a></sup>
29655 <p><a name="K.2p3" href="#K.2p3"><small>3</small></a>
29656 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
29657 subclauses of clause 7.
29659 <p><b>Footnotes</b>
29660 <p><small><a name="note380" href="#note380">380)</a> Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
29664 <p><small><a href="#Contents">Contents</a></small>
29665 <h3><a name="K.3" href="#K.3">K.3 Library</a></h3>
29667 <p><small><a href="#Contents">Contents</a></small>
29668 <h4><a name="K.3.1" href="#K.3.1">K.3.1 Introduction</a></h4>
29670 <p><small><a href="#Contents">Contents</a></small>
29671 <h5><a name="K.3.1.1" href="#K.3.1.1">K.3.1.1 Standard headers</a></h5>
29672 <p><a name="K.3.1.1p1" href="#K.3.1.1p1"><small>1</small></a>
29673 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
29674 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
29675 defined as a macro which expands to the integer constant 0 at the point in the source file
29676 where the appropriate header is first included.
29677 <p><a name="K.3.1.1p2" href="#K.3.1.1p2"><small>2</small></a>
29678 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
29679 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
29680 defined as a macro which expands to the integer constant 1 at the point in the source file
29681 where the appropriate header is first included.<sup><a href="#note381"><b>381)</b></a></sup>
29682 <p><a name="K.3.1.1p3" href="#K.3.1.1p3"><small>3</small></a>
29683 It is implementation-defined whether the functions, macros, and types declared or defined
29684 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
29685 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
29686 where the appropriate header is first included.<sup><a href="#note382"><b>382)</b></a></sup>
29687 <p><a name="K.3.1.1p4" href="#K.3.1.1p4"><small>4</small></a>
29688 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
29689 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
29690 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
29691 implementation shall issue a diagnostic as if a preprocessor error directive were used.
29696 <p><b>Footnotes</b>
29697 <p><small><a name="note381" href="#note381">381)</a> Future revisions of this International Standard may define meanings for other values of
29698 __STDC_WANT_LIB_EXT1__.
29700 <p><small><a name="note382" href="#note382">382)</a> Subclause <a href="#7.1.3">7.1.3</a> reserves certain names and patterns of names that an implementation may use in
29701 headers. All other names are not reserved, and a conforming implementation is not permitted to use
29702 them. While some of the names defined in <a href="#K.3">K.3</a> and its subclauses are reserved, others are not. If an
29703 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
29704 implementation is not conforming.
29707 <p><small><a href="#Contents">Contents</a></small>
29708 <h5><a name="K.3.1.2" href="#K.3.1.2">K.3.1.2 Reserved identifiers</a></h5>
29709 <p><a name="K.3.1.2p1" href="#K.3.1.2p1"><small>1</small></a>
29710 Each macro name in any of the following subclauses is reserved for use as specified if it
29711 is defined by any of its associated headers when included; unless explicitly stated
29712 otherwise (see <a href="#7.1.4">7.1.4</a>).
29713 <p><a name="K.3.1.2p2" href="#K.3.1.2p2"><small>2</small></a>
29714 All identifiers with external linkage in any of the following subclauses are reserved for
29715 use as identifiers with external linkage if any of them are used by the program. None of
29716 them are reserved if none of them are used.
29717 <p><a name="K.3.1.2p3" href="#K.3.1.2p3"><small>3</small></a>
29718 Each identifier with file scope listed in any of the following subclauses is reserved for use
29719 as a macro name and as an identifier with file scope in the same name space if it is
29720 defined by any of its associated headers when included.
29722 <p><small><a href="#Contents">Contents</a></small>
29723 <h5><a name="K.3.1.3" href="#K.3.1.3">K.3.1.3 Use of errno</a></h5>
29724 <p><a name="K.3.1.3p1" href="#K.3.1.3p1"><small>1</small></a>
29725 An implementation may set errno for the functions defined in this annex, but is not
29728 <p><small><a href="#Contents">Contents</a></small>
29729 <h5><a name="K.3.1.4" href="#K.3.1.4">K.3.1.4 Runtime-constraint violations</a></h5>
29730 <p><a name="K.3.1.4p1" href="#K.3.1.4p1"><small>1</small></a>
29731 Most functions in this annex include as part of their specification a list of runtime-
29732 constraints. These runtime-constraints are requirements on the program using the
29733 library.<sup><a href="#note383"><b>383)</b></a></sup>
29734 <p><a name="K.3.1.4p2" href="#K.3.1.4p2"><small>2</small></a>
29735 Implementations shall verify that the runtime-constraints for a function are not violated
29736 by the program. If a runtime-constraint is violated, the implementation shall call the
29737 currently registered runtime-constraint handler (see set_constraint_handler_s
29738 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
29739 function result in only one call to the runtime-constraint handler. It is unspecified which
29740 one of the multiple runtime-constraint violations cause the handler to be called.
29741 <p><a name="K.3.1.4p3" href="#K.3.1.4p3"><small>3</small></a>
29742 If the runtime-constraints section for a function states an action to be performed when a
29743 runtime-constraint violation occurs, the function shall perform the action before calling
29744 the runtime-constraint handler. If the runtime-constraints section lists actions that are
29745 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
29746 the function both before calling the handler and after the handler returns.
29747 <p><a name="K.3.1.4p4" href="#K.3.1.4p4"><small>4</small></a>
29748 The runtime-constraint handler might not return. If the handler does return, the library
29749 function whose runtime-constraint was violated shall return some indication of failure as
29750 given by the returns section in the function's specification.
29756 <p><b>Footnotes</b>
29757 <p><small><a name="note383" href="#note383">383)</a> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
29758 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
29759 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
29760 from the definition of undefined behavior.
29763 <p><small><a href="#Contents">Contents</a></small>
29764 <h4><a name="K.3.2" href="#K.3.2">K.3.2 Errors <errno.h></a></h4>
29765 <p><a name="K.3.2p1" href="#K.3.2p1"><small>1</small></a>
29766 The header <a href="#7.5"><errno.h></a> defines a type.
29767 <p><a name="K.3.2p2" href="#K.3.2p2"><small>2</small></a>
29772 which is type int.<sup><a href="#note384"><b>384)</b></a></sup>
29774 <p><b>Footnotes</b>
29775 <p><small><a name="note384" href="#note384">384)</a> As a matter of programming style, errno_t may be used as the type of something that deals only
29776 with the values that might be found in errno. For example, a function which returns the value of
29777 errno might be declared as having the return type errno_t.
29780 <p><small><a href="#Contents">Contents</a></small>
29781 <h4><a name="K.3.3" href="#K.3.3">K.3.3 Common definitions <stddef.h></a></h4>
29782 <p><a name="K.3.3p1" href="#K.3.3p1"><small>1</small></a>
29783 The header <a href="#7.19"><stddef.h></a> defines a type.
29784 <p><a name="K.3.3p2" href="#K.3.3p2"><small>2</small></a>
29789 which is the type size_t.<sup><a href="#note385"><b>385)</b></a></sup>
29791 <p><b>Footnotes</b>
29792 <p><small><a name="note385" href="#note385">385)</a> See the description of the RSIZE_MAX macro in <a href="#7.20"><stdint.h></a>.
29795 <p><small><a href="#Contents">Contents</a></small>
29796 <h4><a name="K.3.4" href="#K.3.4">K.3.4 Integer types <stdint.h></a></h4>
29797 <p><a name="K.3.4p1" href="#K.3.4p1"><small>1</small></a>
29798 The header <a href="#7.20"><stdint.h></a> defines a macro.
29799 <p><a name="K.3.4p2" href="#K.3.4p2"><small>2</small></a>
29804 which expands to a value<sup><a href="#note386"><b>386)</b></a></sup> of type size_t. Functions that have parameters of type
29805 rsize_t consider it a runtime-constraint violation if the values of those parameters are
29806 greater than RSIZE_MAX.
29807 <p><b>Recommended practice</b>
29808 <p><a name="K.3.4p3" href="#K.3.4p3"><small>3</small></a>
29809 Extremely large object sizes are frequently a sign that an object's size was calculated
29810 incorrectly. For example, negative numbers appear as very large positive numbers when
29811 converted to an unsigned type like size_t. Also, some implementations do not support
29812 objects as large as the maximum value that can be represented by type size_t.
29813 <p><a name="K.3.4p4" href="#K.3.4p4"><small>4</small></a>
29814 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
29815 programming errors. For implementations targeting machines with large address spaces,
29816 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
29817 object supported or (SIZE_MAX >> 1), even if this limit is smaller than the size of
29818 some legitimate, but very large, objects. Implementations targeting machines with small
29819 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
29822 is no object size that is considered a runtime-constraint violation.
29824 <p><b>Footnotes</b>
29825 <p><small><a name="note386" href="#note386">386)</a> The macro RSIZE_MAX need not expand to a constant expression.
29828 <p><small><a href="#Contents">Contents</a></small>
29829 <h4><a name="K.3.5" href="#K.3.5">K.3.5 Input/output <stdio.h></a></h4>
29830 <p><a name="K.3.5p1" href="#K.3.5p1"><small>1</small></a>
29831 The header <a href="#7.21"><stdio.h></a> defines several macros and two types.
29832 <p><a name="K.3.5p2" href="#K.3.5p2"><small>2</small></a>
29837 which expands to an integer constant expression that is the size needed for an array of
29838 char large enough to hold a temporary file name string generated by the tmpnam_s
29843 which expands to an integer constant expression that is the maximum number of unique
29844 file names that can be generated by the tmpnam_s function.
29845 <p><a name="K.3.5p3" href="#K.3.5p3"><small>3</small></a>
29850 which is type int; and
29854 which is the type size_t.
29856 <p><small><a href="#Contents">Contents</a></small>
29857 <h5><a name="K.3.5.1" href="#K.3.5.1">K.3.5.1 Operations on files</a></h5>
29859 <p><small><a href="#Contents">Contents</a></small>
29860 <h5><a name="K.3.5.1.1" href="#K.3.5.1.1">K.3.5.1.1 The tmpfile_s function</a></h5>
29862 <p><a name="K.3.5.1.1p1" href="#K.3.5.1.1p1"><small>1</small></a>
29864 #define __STDC_WANT_LIB_EXT1__ 1
29865 #include <a href="#7.21"><stdio.h></a>
29866 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
29868 Runtime-constraints
29869 <p><a name="K.3.5.1.1p2" href="#K.3.5.1.1p2"><small>2</small></a>
29870 streamptr shall not be a null pointer.
29871 <p><a name="K.3.5.1.1p3" href="#K.3.5.1.1p3"><small>3</small></a>
29872 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
29873 <p><b>Description</b>
29874 <p><a name="K.3.5.1.1p4" href="#K.3.5.1.1p4"><small>4</small></a>
29875 The tmpfile_s function creates a temporary binary file that is different from any other
29876 existing file and that will automatically be removed when it is closed or at program
29877 termination. If the program terminates abnormally, whether an open temporary file is
29878 removed is implementation-defined. The file is opened for update with "wb+" mode
29879 with the meaning that mode has in the fopen_s function (including the mode's effect
29880 on exclusive access and file permissions).
29882 <p><a name="K.3.5.1.1p5" href="#K.3.5.1.1p5"><small>5</small></a>
29883 If the file was created successfully, then the pointer to FILE pointed to by streamptr
29884 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
29885 to FILE pointed to by streamptr will be set to a null pointer.
29886 <p><b>Recommended practice</b>
29887 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
29888 the program (this limit may be shared with tmpnam_s) and there should be no limit on
29889 the number simultaneously open other than this limit and any limit on the number of open
29892 <p><a name="K.3.5.1.1p6" href="#K.3.5.1.1p6"><small>6</small></a>
29893 The tmpfile_s function returns zero if it created the file. If it did not create the file or
29894 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
29896 <p><small><a href="#Contents">Contents</a></small>
29897 <h5><a name="K.3.5.1.2" href="#K.3.5.1.2">K.3.5.1.2 The tmpnam_s function</a></h5>
29899 <p><a name="K.3.5.1.2p1" href="#K.3.5.1.2p1"><small>1</small></a>
29901 #define __STDC_WANT_LIB_EXT1__ 1
29902 #include <a href="#7.21"><stdio.h></a>
29903 errno_t tmpnam_s(char *s, rsize_t maxsize);
29905 Runtime-constraints
29906 <p><a name="K.3.5.1.2p2" href="#K.3.5.1.2p2"><small>2</small></a>
29907 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
29908 maxsize shall be greater than the length of the generated file name string.
29909 <p><b>Description</b>
29910 <p><a name="K.3.5.1.2p3" href="#K.3.5.1.2p3"><small>3</small></a>
29911 The tmpnam_s function generates a string that is a valid file name and that is not the
29912 same as the name of an existing file.<sup><a href="#note387"><b>387)</b></a></sup> The function is potentially capable of generating
29913 TMP_MAX_S different strings, but any or all of them may already be in use by existing
29914 files and thus not be suitable return values. The lengths of these strings shall be less than
29915 the value of the L_tmpnam_s macro.
29916 <p><a name="K.3.5.1.2p4" href="#K.3.5.1.2p4"><small>4</small></a>
29917 The tmpnam_s function generates a different string each time it is called.
29918 <p><a name="K.3.5.1.2p5" href="#K.3.5.1.2p5"><small>5</small></a>
29919 It is assumed that s points to an array of at least maxsize characters. This array will be
29920 set to generated string, as specified below.
29925 <p><a name="K.3.5.1.2p6" href="#K.3.5.1.2p6"><small>6</small></a>
29926 The implementation shall behave as if no library function except tmpnam calls the
29927 tmpnam_s function.<sup><a href="#note388"><b>388)</b></a></sup>
29928 <p><b>Recommended practice</b>
29929 <p><a name="K.3.5.1.2p7" href="#K.3.5.1.2p7"><small>7</small></a>
29930 After a program obtains a file name using the tmpnam_s function and before the
29931 program creates a file with that name, the possibility exists that someone else may create
29932 a file with that same name. To avoid this race condition, the tmpfile_s function
29933 should be used instead of tmpnam_s when possible. One situation that requires the use
29934 of the tmpnam_s function is when the program needs to create a temporary directory
29935 rather than a temporary file.
29937 <p><a name="K.3.5.1.2p8" href="#K.3.5.1.2p8"><small>8</small></a>
29938 If no suitable string can be generated, or if there is a runtime-constraint violation, the
29939 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
29940 is greater than zero) and returns a nonzero value.
29941 <p><a name="K.3.5.1.2p9" href="#K.3.5.1.2p9"><small>9</small></a>
29942 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
29944 <p><b>Environmental limits</b>
29945 <p><a name="K.3.5.1.2p10" href="#K.3.5.1.2p10"><small>10</small></a>
29946 The value of the macro TMP_MAX_S shall be at least 25.
29948 <p><b>Footnotes</b>
29949 <p><small><a name="note387" href="#note387">387)</a> Files created using strings generated by the tmpnam_s function are temporary only in the sense that
29950 their names should not collide with those generated by conventional naming rules for the
29951 implementation. It is still necessary to use the remove function to remove such files when their use
29952 is ended, and before program termination. Implementations should take care in choosing the patterns
29953 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
29954 race condition and possible conflict when multiple programs run simultaneously by the same user
29955 generate the same temporary file names.
29957 <p><small><a name="note388" href="#note388">388)</a> An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
29958 convention for temporary files), but this is not required.
29961 <p><small><a href="#Contents">Contents</a></small>
29962 <h5><a name="K.3.5.2" href="#K.3.5.2">K.3.5.2 File access functions</a></h5>
29964 <p><small><a href="#Contents">Contents</a></small>
29965 <h5><a name="K.3.5.2.1" href="#K.3.5.2.1">K.3.5.2.1 The fopen_s function</a></h5>
29967 <p><a name="K.3.5.2.1p1" href="#K.3.5.2.1p1"><small>1</small></a>
29969 #define __STDC_WANT_LIB_EXT1__ 1
29970 #include <a href="#7.21"><stdio.h></a>
29971 errno_t fopen_s(FILE * restrict * restrict streamptr,
29972 const char * restrict filename,
29973 const char * restrict mode);
29975 Runtime-constraints
29976 <p><a name="K.3.5.2.1p2" href="#K.3.5.2.1p2"><small>2</small></a>
29977 None of streamptr, filename, or mode shall be a null pointer.
29978 <p><a name="K.3.5.2.1p3" href="#K.3.5.2.1p3"><small>3</small></a>
29979 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
29980 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
29987 <p><b>Description</b>
29988 <p><a name="K.3.5.2.1p4" href="#K.3.5.2.1p4"><small>4</small></a>
29989 The fopen_s function opens the file whose name is the string pointed to by
29990 filename, and associates a stream with it.
29991 <p><a name="K.3.5.2.1p5" href="#K.3.5.2.1p5"><small>5</small></a>
29992 The mode string shall be as described for fopen, with the addition that modes starting
29993 with the character 'w' or 'a' may be preceded by the character 'u', see below:
29994 uw truncate to zero length or create text file for writing, default
29998 uwx create text file for writing, default permissions
29999 ua append; open or create text file for writing at end-of-file, default
30003 uwb truncate to zero length or create binary file for writing, default
30007 uwbx create binary file for writing, default permissions
30008 uab append; open or create binary file for writing at end-of-file, default
30012 uw+ truncate to zero length or create text file for update, default
30016 uw+x create text file for update, default permissions
30017 ua+ append; open or create text file for update, writing at end-of-file,
30019 default permissions
30021 uw+b or uwb+ truncate to zero length or create binary file for update, default
30025 uw+bx or uwb+x create binary file for update, default permissions
30026 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
30028 default permissions
30030 <p><a name="K.3.5.2.1p6" href="#K.3.5.2.1p6"><small>6</small></a>
30031 Opening a file with exclusive mode ('x' as the last character in the mode argument)
30032 fails if the file already exists or cannot be created.
30033 <p><a name="K.3.5.2.1p7" href="#K.3.5.2.1p7"><small>7</small></a>
30034 To the extent that the underlying system supports the concepts, files opened for writing
30035 shall be opened with exclusive (also known as non-shared) access. If the file is being
30036 created, and the first character of the mode string is not 'u', to the extent that the
30037 underlying system supports it, the file shall have a file permission that prevents other
30038 users on the system from accessing the file. If the file is being created and first character
30039 of the mode string is 'u', then by the time the file has been closed, it shall have the
30040 system default file access permissions.<sup><a href="#note389"><b>389)</b></a></sup>
30041 <p><a name="K.3.5.2.1p8" href="#K.3.5.2.1p8"><small>8</small></a>
30042 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
30043 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
30047 to FILE pointed to by streamptr will be set to a null pointer.
30049 <p><a name="K.3.5.2.1p9" href="#K.3.5.2.1p9"><small>9</small></a>
30050 The fopen_s function returns zero if it opened the file. If it did not open the file or if
30051 there was a runtime-constraint violation, fopen_s returns a nonzero value.
30053 <p><b>Footnotes</b>
30054 <p><small><a name="note389" href="#note389">389)</a> These are the same permissions that the file would have been created with by fopen.
30057 <p><small><a href="#Contents">Contents</a></small>
30058 <h5><a name="K.3.5.2.2" href="#K.3.5.2.2">K.3.5.2.2 The freopen_s function</a></h5>
30060 <p><a name="K.3.5.2.2p1" href="#K.3.5.2.2p1"><small>1</small></a>
30062 #define __STDC_WANT_LIB_EXT1__ 1
30063 #include <a href="#7.21"><stdio.h></a>
30064 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
30065 const char * restrict filename,
30066 const char * restrict mode,
30067 FILE * restrict stream);
30069 Runtime-constraints
30070 <p><a name="K.3.5.2.2p2" href="#K.3.5.2.2p2"><small>2</small></a>
30071 None of newstreamptr, mode, and stream shall be a null pointer.
30072 <p><a name="K.3.5.2.2p3" href="#K.3.5.2.2p3"><small>3</small></a>
30073 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
30074 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
30075 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
30076 <p><b>Description</b>
30077 <p><a name="K.3.5.2.2p4" href="#K.3.5.2.2p4"><small>4</small></a>
30078 The freopen_s function opens the file whose name is the string pointed to by
30079 filename and associates the stream pointed to by stream with it. The mode
30080 argument has the same meaning as in the fopen_s function (including the mode's effect
30081 on exclusive access and file permissions).
30082 <p><a name="K.3.5.2.2p5" href="#K.3.5.2.2p5"><small>5</small></a>
30083 If filename is a null pointer, the freopen_s function attempts to change the mode of
30084 the stream to that specified by mode, as if the name of the file currently associated with
30085 the stream had been used. It is implementation-defined which changes of mode are
30086 permitted (if any), and under what circumstances.
30087 <p><a name="K.3.5.2.2p6" href="#K.3.5.2.2p6"><small>6</small></a>
30088 The freopen_s function first attempts to close any file that is associated with stream.
30089 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
30091 <p><a name="K.3.5.2.2p7" href="#K.3.5.2.2p7"><small>7</small></a>
30092 If the file was opened successfully, then the pointer to FILE pointed to by
30093 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
30094 pointed to by newstreamptr will be set to a null pointer.
30096 <p><a name="K.3.5.2.2p8" href="#K.3.5.2.2p8"><small>8</small></a>
30097 The freopen_s function returns zero if it opened the file. If it did not open the file or
30098 there was a runtime-constraint violation, freopen_s returns a nonzero value.
30101 <p><small><a href="#Contents">Contents</a></small>
30102 <h5><a name="K.3.5.3" href="#K.3.5.3">K.3.5.3 Formatted input/output functions</a></h5>
30103 <p><a name="K.3.5.3p1" href="#K.3.5.3p1"><small>1</small></a>
30104 Unless explicitly stated otherwise, if the execution of a function described in this
30105 subclause causes copying to take place between objects that overlap, the objects take on
30106 unspecified values.
30108 <p><small><a href="#Contents">Contents</a></small>
30109 <h5><a name="K.3.5.3.1" href="#K.3.5.3.1">K.3.5.3.1 The fprintf_s function</a></h5>
30111 <p><a name="K.3.5.3.1p1" href="#K.3.5.3.1p1"><small>1</small></a>
30113 #define __STDC_WANT_LIB_EXT1__ 1
30114 #include <a href="#7.21"><stdio.h></a>
30115 int fprintf_s(FILE * restrict stream,
30116 const char * restrict format, ...);
30118 Runtime-constraints
30119 <p><a name="K.3.5.3.1p2" href="#K.3.5.3.1p2"><small>2</small></a>
30120 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note390"><b>390)</b></a></sup> (modified or
30121 not by flags, field width, or precision) shall not appear in the string pointed to by
30122 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
30124 <p><a name="K.3.5.3.1p3" href="#K.3.5.3.1p3"><small>3</small></a>
30125 If there is a runtime-constraint violation,<sup><a href="#note391"><b>391)</b></a></sup> the fprintf_s function does not attempt
30126 to produce further output, and it is unspecified to what extent fprintf_s produced
30127 output before discovering the runtime-constraint violation.
30128 <p><b>Description</b>
30129 <p><a name="K.3.5.3.1p4" href="#K.3.5.3.1p4"><small>4</small></a>
30130 The fprintf_s function is equivalent to the fprintf function except for the explicit
30131 runtime-constraints listed above.
30133 <p><a name="K.3.5.3.1p5" href="#K.3.5.3.1p5"><small>5</small></a>
30134 The fprintf_s function returns the number of characters transmitted, or a negative
30135 value if an output error, encoding error, or runtime-constraint violation occurred.
30142 <p><b>Footnotes</b>
30143 <p><small><a name="note390" href="#note390">390)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30144 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30145 format string was %%n.
30147 <p><small><a name="note391" href="#note391">391)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
30148 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
30149 constraint violation.
30152 <p><small><a href="#Contents">Contents</a></small>
30153 <h5><a name="K.3.5.3.2" href="#K.3.5.3.2">K.3.5.3.2 The fscanf_s function</a></h5>
30155 <p><a name="K.3.5.3.2p1" href="#K.3.5.3.2p1"><small>1</small></a>
30157 #define __STDC_WANT_LIB_EXT1__ 1
30158 #include <a href="#7.21"><stdio.h></a>
30159 int fscanf_s(FILE * restrict stream,
30160 const char * restrict format, ...);
30162 Runtime-constraints
30163 <p><a name="K.3.5.3.2p2" href="#K.3.5.3.2p2"><small>2</small></a>
30164 Neither stream nor format shall be a null pointer. Any argument indirected though in
30165 order to store converted input shall not be a null pointer.
30166 <p><a name="K.3.5.3.2p3" href="#K.3.5.3.2p3"><small>3</small></a>
30167 If there is a runtime-constraint violation,<sup><a href="#note392"><b>392)</b></a></sup> the fscanf_s function does not attempt to
30168 perform further input, and it is unspecified to what extent fscanf_s performed input
30169 before discovering the runtime-constraint violation.
30170 <p><b>Description</b>
30171 <p><a name="K.3.5.3.2p4" href="#K.3.5.3.2p4"><small>4</small></a>
30172 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
30173 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
30174 *). The first of these arguments is the same as for fscanf. That argument is
30175 immediately followed in the argument list by the second argument, which has type
30176 rsize_t and gives the number of elements in the array pointed to by the first argument
30177 of the pair. If the first argument points to a scalar object, it is considered to be an array of
30178 one element.<sup><a href="#note393"><b>393)</b></a></sup>
30179 <p><a name="K.3.5.3.2p5" href="#K.3.5.3.2p5"><small>5</small></a>
30180 A matching failure occurs if the number of elements in a receiving object is insufficient to
30181 hold the converted input (including any trailing null character).
30183 <p><a name="K.3.5.3.2p6" href="#K.3.5.3.2p6"><small>6</small></a>
30184 The fscanf_s function returns the value of the macro EOF if an input failure occurs
30185 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30188 fscanf_s function returns the number of input items assigned, which can be fewer than
30189 provided for, or even zero, in the event of an early matching failure.
30190 <p><a name="K.3.5.3.2p7" href="#K.3.5.3.2p7"><small>7</small></a>
30191 EXAMPLE 1 The call:
30193 #define __STDC_WANT_LIB_EXT1__ 1
30194 #include <a href="#7.21"><stdio.h></a>
30196 int n, i; float x; char name[50];
30197 n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
30199 with the input line:
30201 25 54.32E-1 thompson
30203 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
30206 <p><a name="K.3.5.3.2p8" href="#K.3.5.3.2p8"><small>8</small></a>
30207 EXAMPLE 2 The call:
30209 #define __STDC_WANT_LIB_EXT1__ 1
30210 #include <a href="#7.21"><stdio.h></a>
30213 n = fscanf_s(stdin, "%s", s, sizeof s);
30215 with the input line:
30219 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
30220 array of six characters to store it.
30223 <p><b>Footnotes</b>
30224 <p><small><a name="note392" href="#note392">392)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
30225 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
30226 constraint violation.
30228 <p><small><a name="note393" href="#note393">393)</a> If the format is known at translation time, an implementation may issue a diagnostic for any argument
30229 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
30230 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
30231 the format is not known at translation time. For example, an implementation may issue a diagnostic
30232 for each argument after format that has of type pointer to one of char, signed char,
30233 unsigned char, or void that is not followed by an argument of a type compatible with
30234 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
30235 using the hh length modifier, a length argument must follow the pointer argument. Another useful
30236 diagnostic could flag any non-pointer argument following format that did not have a type
30237 compatible with rsize_t.
30240 <p><small><a href="#Contents">Contents</a></small>
30241 <h5><a name="K.3.5.3.3" href="#K.3.5.3.3">K.3.5.3.3 The printf_s function</a></h5>
30243 <p><a name="K.3.5.3.3p1" href="#K.3.5.3.3p1"><small>1</small></a>
30245 #define __STDC_WANT_LIB_EXT1__ 1
30246 #include <a href="#7.21"><stdio.h></a>
30247 int printf_s(const char * restrict format, ...);
30249 Runtime-constraints
30250 <p><a name="K.3.5.3.3p2" href="#K.3.5.3.3p2"><small>2</small></a>
30251 format shall not be a null pointer. The %n specifier<sup><a href="#note394"><b>394)</b></a></sup> (modified or not by flags, field
30252 width, or precision) shall not appear in the string pointed to by format. Any argument
30253 to printf_s corresponding to a %s specifier shall not be a null pointer.
30254 <p><a name="K.3.5.3.3p3" href="#K.3.5.3.3p3"><small>3</small></a>
30255 If there is a runtime-constraint violation, the printf_s function does not attempt to
30256 produce further output, and it is unspecified to what extent printf_s produced output
30257 before discovering the runtime-constraint violation.
30261 <p><b>Description</b>
30262 <p><a name="K.3.5.3.3p4" href="#K.3.5.3.3p4"><small>4</small></a>
30263 The printf_s function is equivalent to the printf function except for the explicit
30264 runtime-constraints listed above.
30266 <p><a name="K.3.5.3.3p5" href="#K.3.5.3.3p5"><small>5</small></a>
30267 The printf_s function returns the number of characters transmitted, or a negative
30268 value if an output error, encoding error, or runtime-constraint violation occurred.
30270 <p><b>Footnotes</b>
30271 <p><small><a name="note394" href="#note394">394)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30272 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30273 format string was %%n.
30276 <p><small><a href="#Contents">Contents</a></small>
30277 <h5><a name="K.3.5.3.4" href="#K.3.5.3.4">K.3.5.3.4 The scanf_s function</a></h5>
30279 <p><a name="K.3.5.3.4p1" href="#K.3.5.3.4p1"><small>1</small></a>
30281 #define __STDC_WANT_LIB_EXT1__ 1
30282 #include <a href="#7.21"><stdio.h></a>
30283 int scanf_s(const char * restrict format, ...);
30285 Runtime-constraints
30286 <p><a name="K.3.5.3.4p2" href="#K.3.5.3.4p2"><small>2</small></a>
30287 format shall not be a null pointer. Any argument indirected though in order to store
30288 converted input shall not be a null pointer.
30289 <p><a name="K.3.5.3.4p3" href="#K.3.5.3.4p3"><small>3</small></a>
30290 If there is a runtime-constraint violation, the scanf_s function does not attempt to
30291 perform further input, and it is unspecified to what extent scanf_s performed input
30292 before discovering the runtime-constraint violation.
30293 <p><b>Description</b>
30294 <p><a name="K.3.5.3.4p4" href="#K.3.5.3.4p4"><small>4</small></a>
30295 The scanf_s function is equivalent to fscanf_s with the argument stdin
30296 interposed before the arguments to scanf_s.
30298 <p><a name="K.3.5.3.4p5" href="#K.3.5.3.4p5"><small>5</small></a>
30299 The scanf_s function returns the value of the macro EOF if an input failure occurs
30300 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30301 scanf_s function returns the number of input items assigned, which can be fewer than
30302 provided for, or even zero, in the event of an early matching failure.
30304 <p><small><a href="#Contents">Contents</a></small>
30305 <h5><a name="K.3.5.3.5" href="#K.3.5.3.5">K.3.5.3.5 The snprintf_s function</a></h5>
30307 <p><a name="K.3.5.3.5p1" href="#K.3.5.3.5p1"><small>1</small></a>
30309 #define __STDC_WANT_LIB_EXT1__ 1
30310 #include <a href="#7.21"><stdio.h></a>
30311 int snprintf_s(char * restrict s, rsize_t n,
30312 const char * restrict format, ...);
30314 Runtime-constraints
30315 <p><a name="K.3.5.3.5p2" href="#K.3.5.3.5p2"><small>2</small></a>
30316 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30317 than RSIZE_MAX. The %n specifier<sup><a href="#note395"><b>395)</b></a></sup> (modified or not by flags, field width, or
30318 precision) shall not appear in the string pointed to by format. Any argument to
30320 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30322 <p><a name="K.3.5.3.5p3" href="#K.3.5.3.5p3"><small>3</small></a>
30323 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30324 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
30326 <p><b>Description</b>
30327 <p><a name="K.3.5.3.5p4" href="#K.3.5.3.5p4"><small>4</small></a>
30328 The snprintf_s function is equivalent to the snprintf function except for the
30329 explicit runtime-constraints listed above.
30330 <p><a name="K.3.5.3.5p5" href="#K.3.5.3.5p5"><small>5</small></a>
30331 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
30332 array pointed to by s.
30334 <p><a name="K.3.5.3.5p6" href="#K.3.5.3.5p6"><small>6</small></a>
30335 The snprintf_s function returns the number of characters that would have been
30336 written had n been sufficiently large, not counting the terminating null character, or a
30337 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
30338 output has been completely written if and only if the returned value is nonnegative and
30341 <p><b>Footnotes</b>
30342 <p><small><a name="note395" href="#note395">395)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30343 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30344 format string was %%n.
30347 <p><small><a href="#Contents">Contents</a></small>
30348 <h5><a name="K.3.5.3.6" href="#K.3.5.3.6">K.3.5.3.6 The sprintf_s function</a></h5>
30350 <p><a name="K.3.5.3.6p1" href="#K.3.5.3.6p1"><small>1</small></a>
30352 #define __STDC_WANT_LIB_EXT1__ 1
30353 #include <a href="#7.21"><stdio.h></a>
30354 int sprintf_s(char * restrict s, rsize_t n,
30355 const char * restrict format, ...);
30357 Runtime-constraints
30358 <p><a name="K.3.5.3.6p2" href="#K.3.5.3.6p2"><small>2</small></a>
30359 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30360 than RSIZE_MAX. The number of characters (including the trailing null) required for the
30361 result to be written to the array pointed to by s shall not be greater than n. The %n
30362 specifier<sup><a href="#note396"><b>396)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30363 string pointed to by format. Any argument to sprintf_s corresponding to a %s
30364 specifier shall not be a null pointer. No encoding error shall occur.
30369 <p><a name="K.3.5.3.6p3" href="#K.3.5.3.6p3"><small>3</small></a>
30370 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30371 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
30373 <p><b>Description</b>
30374 <p><a name="K.3.5.3.6p4" href="#K.3.5.3.6p4"><small>4</small></a>
30375 The sprintf_s function is equivalent to the sprintf function except for the
30376 parameter n and the explicit runtime-constraints listed above.
30377 <p><a name="K.3.5.3.6p5" href="#K.3.5.3.6p5"><small>5</small></a>
30378 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
30379 pointed to by s as a runtime-constraint violation.
30381 <p><a name="K.3.5.3.6p6" href="#K.3.5.3.6p6"><small>6</small></a>
30382 If no runtime-constraint violation occurred, the sprintf_s function returns the number
30383 of characters written in the array, not counting the terminating null character. If an
30384 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
30385 constraint violation occurred, sprintf_s returns zero.
30387 <p><b>Footnotes</b>
30388 <p><small><a name="note396" href="#note396">396)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30389 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30390 format string was %%n.
30393 <p><small><a href="#Contents">Contents</a></small>
30394 <h5><a name="K.3.5.3.7" href="#K.3.5.3.7">K.3.5.3.7 The sscanf_s function</a></h5>
30396 <p><a name="K.3.5.3.7p1" href="#K.3.5.3.7p1"><small>1</small></a>
30398 #define __STDC_WANT_LIB_EXT1__ 1
30399 #include <a href="#7.21"><stdio.h></a>
30400 int sscanf_s(const char * restrict s,
30401 const char * restrict format, ...);
30403 Runtime-constraints
30404 <p><a name="K.3.5.3.7p2" href="#K.3.5.3.7p2"><small>2</small></a>
30405 Neither s nor format shall be a null pointer. Any argument indirected though in order
30406 to store converted input shall not be a null pointer.
30407 <p><a name="K.3.5.3.7p3" href="#K.3.5.3.7p3"><small>3</small></a>
30408 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
30409 perform further input, and it is unspecified to what extent sscanf_s performed input
30410 before discovering the runtime-constraint violation.
30411 <p><b>Description</b>
30412 <p><a name="K.3.5.3.7p4" href="#K.3.5.3.7p4"><small>4</small></a>
30413 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
30414 a string (specified by the argument s) rather than from a stream. Reaching the end of the
30415 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
30416 takes place between objects that overlap, the objects take on unspecified values.
30418 <p><a name="K.3.5.3.7p5" href="#K.3.5.3.7p5"><small>5</small></a>
30419 The sscanf_s function returns the value of the macro EOF if an input failure occurs
30420 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30421 sscanf_s function returns the number of input items assigned, which can be fewer than
30422 provided for, or even zero, in the event of an early matching failure.
30425 <p><small><a href="#Contents">Contents</a></small>
30426 <h5><a name="K.3.5.3.8" href="#K.3.5.3.8">K.3.5.3.8 The vfprintf_s function</a></h5>
30428 <p><a name="K.3.5.3.8p1" href="#K.3.5.3.8p1"><small>1</small></a>
30430 #define __STDC_WANT_LIB_EXT1__ 1
30431 #include <a href="#7.16"><stdarg.h></a>
30432 #include <a href="#7.21"><stdio.h></a>
30433 int vfprintf_s(FILE * restrict stream,
30434 const char * restrict format,
30437 Runtime-constraints
30438 <p><a name="K.3.5.3.8p2" href="#K.3.5.3.8p2"><small>2</small></a>
30439 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note397"><b>397)</b></a></sup> (modified or
30440 not by flags, field width, or precision) shall not appear in the string pointed to by
30441 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
30443 <p><a name="K.3.5.3.8p3" href="#K.3.5.3.8p3"><small>3</small></a>
30444 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
30445 produce further output, and it is unspecified to what extent vfprintf_s produced
30446 output before discovering the runtime-constraint violation.
30447 <p><b>Description</b>
30448 <p><a name="K.3.5.3.8p4" href="#K.3.5.3.8p4"><small>4</small></a>
30449 The vfprintf_s function is equivalent to the vfprintf function except for the
30450 explicit runtime-constraints listed above.
30452 <p><a name="K.3.5.3.8p5" href="#K.3.5.3.8p5"><small>5</small></a>
30453 The vfprintf_s function returns the number of characters transmitted, or a negative
30454 value if an output error, encoding error, or runtime-constraint violation occurred.
30456 <p><b>Footnotes</b>
30457 <p><small><a name="note397" href="#note397">397)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30458 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30459 format string was %%n.
30462 <p><small><a href="#Contents">Contents</a></small>
30463 <h5><a name="K.3.5.3.9" href="#K.3.5.3.9">K.3.5.3.9 The vfscanf_s function</a></h5>
30465 <p><a name="K.3.5.3.9p1" href="#K.3.5.3.9p1"><small>1</small></a>
30467 #define __STDC_WANT_LIB_EXT1__ 1
30468 #include <a href="#7.16"><stdarg.h></a>
30469 #include <a href="#7.21"><stdio.h></a>
30470 int vfscanf_s(FILE * restrict stream,
30471 const char * restrict format,
30479 Runtime-constraints
30480 <p><a name="K.3.5.3.9p2" href="#K.3.5.3.9p2"><small>2</small></a>
30481 Neither stream nor format shall be a null pointer. Any argument indirected though in
30482 order to store converted input shall not be a null pointer.
30483 <p><a name="K.3.5.3.9p3" href="#K.3.5.3.9p3"><small>3</small></a>
30484 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
30485 perform further input, and it is unspecified to what extent vfscanf_s performed input
30486 before discovering the runtime-constraint violation.
30487 <p><b>Description</b>
30488 <p><a name="K.3.5.3.9p4" href="#K.3.5.3.9p4"><small>4</small></a>
30489 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
30490 replaced by arg, which shall have been initialized by the va_start macro (and
30491 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
30492 va_end macro.<sup><a href="#note398"><b>398)</b></a></sup>
30494 <p><a name="K.3.5.3.9p5" href="#K.3.5.3.9p5"><small>5</small></a>
30495 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
30496 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30497 vfscanf_s function returns the number of input items assigned, which can be fewer
30498 than provided for, or even zero, in the event of an early matching failure.
30500 <p><b>Footnotes</b>
30501 <p><small><a name="note398" href="#note398">398)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30502 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30506 <p><small><a href="#Contents">Contents</a></small>
30507 <h5><a name="K.3.5.3.10" href="#K.3.5.3.10">K.3.5.3.10 The vprintf_s function</a></h5>
30509 <p><a name="K.3.5.3.10p1" href="#K.3.5.3.10p1"><small>1</small></a>
30511 #define __STDC_WANT_LIB_EXT1__ 1
30512 #include <a href="#7.16"><stdarg.h></a>
30513 #include <a href="#7.21"><stdio.h></a>
30514 int vprintf_s(const char * restrict format,
30517 Runtime-constraints
30518 <p><a name="K.3.5.3.10p2" href="#K.3.5.3.10p2"><small>2</small></a>
30519 format shall not be a null pointer. The %n specifier<sup><a href="#note399"><b>399)</b></a></sup> (modified or not by flags, field
30520 width, or precision) shall not appear in the string pointed to by format. Any argument
30521 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
30522 <p><a name="K.3.5.3.10p3" href="#K.3.5.3.10p3"><small>3</small></a>
30523 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
30524 produce further output, and it is unspecified to what extent vprintf_s produced output
30525 before discovering the runtime-constraint violation.
30528 <p><b>Description</b>
30529 <p><a name="K.3.5.3.10p4" href="#K.3.5.3.10p4"><small>4</small></a>
30530 The vprintf_s function is equivalent to the vprintf function except for the explicit
30531 runtime-constraints listed above.
30533 <p><a name="K.3.5.3.10p5" href="#K.3.5.3.10p5"><small>5</small></a>
30534 The vprintf_s function returns the number of characters transmitted, or a negative
30535 value if an output error, encoding error, or runtime-constraint violation occurred.
30537 <p><b>Footnotes</b>
30538 <p><small><a name="note399" href="#note399">399)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30539 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30540 format string was %%n.
30543 <p><small><a href="#Contents">Contents</a></small>
30544 <h5><a name="K.3.5.3.11" href="#K.3.5.3.11">K.3.5.3.11 The vscanf_s function</a></h5>
30546 <p><a name="K.3.5.3.11p1" href="#K.3.5.3.11p1"><small>1</small></a>
30548 #define __STDC_WANT_LIB_EXT1__ 1
30549 #include <a href="#7.16"><stdarg.h></a>
30550 #include <a href="#7.21"><stdio.h></a>
30551 int vscanf_s(const char * restrict format,
30554 Runtime-constraints
30555 <p><a name="K.3.5.3.11p2" href="#K.3.5.3.11p2"><small>2</small></a>
30556 format shall not be a null pointer. Any argument indirected though in order to store
30557 converted input shall not be a null pointer.
30558 <p><a name="K.3.5.3.11p3" href="#K.3.5.3.11p3"><small>3</small></a>
30559 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
30560 perform further input, and it is unspecified to what extent vscanf_s performed input
30561 before discovering the runtime-constraint violation.
30562 <p><b>Description</b>
30563 <p><a name="K.3.5.3.11p4" href="#K.3.5.3.11p4"><small>4</small></a>
30564 The vscanf_s function is equivalent to scanf_s, with the variable argument list
30565 replaced by arg, which shall have been initialized by the va_start macro (and
30566 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
30567 va_end macro.<sup><a href="#note400"><b>400)</b></a></sup>
30569 <p><a name="K.3.5.3.11p5" href="#K.3.5.3.11p5"><small>5</small></a>
30570 The vscanf_s function returns the value of the macro EOF if an input failure occurs
30571 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30572 vscanf_s function returns the number of input items assigned, which can be fewer than
30573 provided for, or even zero, in the event of an early matching failure.
30580 <p><b>Footnotes</b>
30581 <p><small><a name="note400" href="#note400">400)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30582 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30586 <p><small><a href="#Contents">Contents</a></small>
30587 <h5><a name="K.3.5.3.12" href="#K.3.5.3.12">K.3.5.3.12 The vsnprintf_s function</a></h5>
30589 <p><a name="K.3.5.3.12p1" href="#K.3.5.3.12p1"><small>1</small></a>
30591 #define __STDC_WANT_LIB_EXT1__ 1
30592 #include <a href="#7.16"><stdarg.h></a>
30593 #include <a href="#7.21"><stdio.h></a>
30594 int vsnprintf_s(char * restrict s, rsize_t n,
30595 const char * restrict format,
30598 Runtime-constraints
30599 <p><a name="K.3.5.3.12p2" href="#K.3.5.3.12p2"><small>2</small></a>
30600 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30601 than RSIZE_MAX. The %n specifier<sup><a href="#note401"><b>401)</b></a></sup> (modified or not by flags, field width, or
30602 precision) shall not appear in the string pointed to by format. Any argument to
30603 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30605 <p><a name="K.3.5.3.12p3" href="#K.3.5.3.12p3"><small>3</small></a>
30606 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30607 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
30609 <p><b>Description</b>
30610 <p><a name="K.3.5.3.12p4" href="#K.3.5.3.12p4"><small>4</small></a>
30611 The vsnprintf_s function is equivalent to the vsnprintf function except for the
30612 explicit runtime-constraints listed above.
30613 <p><a name="K.3.5.3.12p5" href="#K.3.5.3.12p5"><small>5</small></a>
30614 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
30615 the array pointed to by s.
30617 <p><a name="K.3.5.3.12p6" href="#K.3.5.3.12p6"><small>6</small></a>
30618 The vsnprintf_s function returns the number of characters that would have been
30619 written had n been sufficiently large, not counting the terminating null character, or a
30620 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
30621 output has been completely written if and only if the returned value is nonnegative and
30629 <p><b>Footnotes</b>
30630 <p><small><a name="note401" href="#note401">401)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30631 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30632 format string was %%n.
30635 <p><small><a href="#Contents">Contents</a></small>
30636 <h5><a name="K.3.5.3.13" href="#K.3.5.3.13">K.3.5.3.13 The vsprintf_s function</a></h5>
30638 <p><a name="K.3.5.3.13p1" href="#K.3.5.3.13p1"><small>1</small></a>
30640 #define __STDC_WANT_LIB_EXT1__ 1
30641 #include <a href="#7.16"><stdarg.h></a>
30642 #include <a href="#7.21"><stdio.h></a>
30643 int vsprintf_s(char * restrict s, rsize_t n,
30644 const char * restrict format,
30647 Runtime-constraints
30648 <p><a name="K.3.5.3.13p2" href="#K.3.5.3.13p2"><small>2</small></a>
30649 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30650 than RSIZE_MAX. The number of characters (including the trailing null) required for the
30651 result to be written to the array pointed to by s shall not be greater than n. The %n
30652 specifier<sup><a href="#note402"><b>402)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30653 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
30654 specifier shall not be a null pointer. No encoding error shall occur.
30655 <p><a name="K.3.5.3.13p3" href="#K.3.5.3.13p3"><small>3</small></a>
30656 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30657 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
30659 <p><b>Description</b>
30660 <p><a name="K.3.5.3.13p4" href="#K.3.5.3.13p4"><small>4</small></a>
30661 The vsprintf_s function is equivalent to the vsprintf function except for the
30662 parameter n and the explicit runtime-constraints listed above.
30663 <p><a name="K.3.5.3.13p5" href="#K.3.5.3.13p5"><small>5</small></a>
30664 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
30665 pointed to by s as a runtime-constraint violation.
30667 <p><a name="K.3.5.3.13p6" href="#K.3.5.3.13p6"><small>6</small></a>
30668 If no runtime-constraint violation occurred, the vsprintf_s function returns the
30669 number of characters written in the array, not counting the terminating null character. If
30670 an encoding error occurred, vsprintf_s returns a negative value. If any other
30671 runtime-constraint violation occurred, vsprintf_s returns zero.
30678 <p><b>Footnotes</b>
30679 <p><small><a name="note402" href="#note402">402)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30680 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30681 format string was %%n.
30684 <p><small><a href="#Contents">Contents</a></small>
30685 <h5><a name="K.3.5.3.14" href="#K.3.5.3.14">K.3.5.3.14 The vsscanf_s function</a></h5>
30687 <p><a name="K.3.5.3.14p1" href="#K.3.5.3.14p1"><small>1</small></a>
30689 #define __STDC_WANT_LIB_EXT1__ 1
30690 #include <a href="#7.16"><stdarg.h></a>
30691 #include <a href="#7.21"><stdio.h></a>
30692 int vsscanf_s(const char * restrict s,
30693 const char * restrict format,
30696 Runtime-constraints
30697 <p><a name="K.3.5.3.14p2" href="#K.3.5.3.14p2"><small>2</small></a>
30698 Neither s nor format shall be a null pointer. Any argument indirected though in order
30699 to store converted input shall not be a null pointer.
30700 <p><a name="K.3.5.3.14p3" href="#K.3.5.3.14p3"><small>3</small></a>
30701 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
30702 perform further input, and it is unspecified to what extent vsscanf_s performed input
30703 before discovering the runtime-constraint violation.
30704 <p><b>Description</b>
30705 <p><a name="K.3.5.3.14p4" href="#K.3.5.3.14p4"><small>4</small></a>
30706 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
30707 replaced by arg, which shall have been initialized by the va_start macro (and
30708 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
30709 va_end macro.<sup><a href="#note403"><b>403)</b></a></sup>
30711 <p><a name="K.3.5.3.14p5" href="#K.3.5.3.14p5"><small>5</small></a>
30712 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
30713 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30714 vscanf_s function returns the number of input items assigned, which can be fewer than
30715 provided for, or even zero, in the event of an early matching failure.
30717 <p><b>Footnotes</b>
30718 <p><small><a name="note403" href="#note403">403)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30719 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30723 <p><small><a href="#Contents">Contents</a></small>
30724 <h5><a name="K.3.5.4" href="#K.3.5.4">K.3.5.4 Character input/output functions</a></h5>
30726 <p><small><a href="#Contents">Contents</a></small>
30727 <h5><a name="K.3.5.4.1" href="#K.3.5.4.1">K.3.5.4.1 The gets_s function</a></h5>
30729 <p><a name="K.3.5.4.1p1" href="#K.3.5.4.1p1"><small>1</small></a>
30731 #define __STDC_WANT_LIB_EXT1__ 1
30732 #include <a href="#7.21"><stdio.h></a>
30733 char *gets_s(char *s, rsize_t n);
30740 Runtime-constraints
30741 <p><a name="K.3.5.4.1p2" href="#K.3.5.4.1p2"><small>2</small></a>
30742 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
30743 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
30744 n-1 characters from stdin.<sup><a href="#note404"><b>404)</b></a></sup>
30745 <p><a name="K.3.5.4.1p3" href="#K.3.5.4.1p3"><small>3</small></a>
30746 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
30747 are read and discarded from stdin until a new-line character is read, or end-of-file or a
30749 <p><b>Description</b>
30750 <p><a name="K.3.5.4.1p4" href="#K.3.5.4.1p4"><small>4</small></a>
30751 The gets_s function reads at most one less than the number of characters specified by n
30752 from the stream pointed to by stdin, into the array pointed to by s. No additional
30753 characters are read after a new-line character (which is discarded) or after end-of-file.
30754 The discarded new-line character does not count towards number of characters read. A
30755 null character is written immediately after the last character read into the array.
30756 <p><a name="K.3.5.4.1p5" href="#K.3.5.4.1p5"><small>5</small></a>
30757 If end-of-file is encountered and no characters have been read into the array, or if a read
30758 error occurs during the operation, then s[0] is set to the null character, and the other
30759 elements of s take unspecified values.
30760 <p><b>Recommended practice</b>
30761 <p><a name="K.3.5.4.1p6" href="#K.3.5.4.1p6"><small>6</small></a>
30762 The fgets function allows properly-written programs to safely process input lines too
30763 long to store in the result array. In general this requires that callers of fgets pay
30764 attention to the presence or absence of a new-line character in the result array. Consider
30765 using fgets (along with any needed processing based on new-line characters) instead of
30768 <p><a name="K.3.5.4.1p7" href="#K.3.5.4.1p7"><small>7</small></a>
30769 The gets_s function returns s if successful. If there was a runtime-constraint violation,
30770 or if end-of-file is encountered and no characters have been read into the array, or if a
30771 read error occurs during the operation, then a null pointer is returned.
30778 <p><b>Footnotes</b>
30779 <p><small><a name="note404" href="#note404">404)</a> The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
30780 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
30781 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
30782 expect such a relationship.
30785 <p><small><a href="#Contents">Contents</a></small>
30786 <h4><a name="K.3.6" href="#K.3.6">K.3.6 General utilities <stdlib.h></a></h4>
30787 <p><a name="K.3.6p1" href="#K.3.6p1"><small>1</small></a>
30788 The header <a href="#7.22"><stdlib.h></a> defines three types.
30789 <p><a name="K.3.6p2" href="#K.3.6p2"><small>2</small></a>
30794 which is type int; and
30798 which is the type size_t; and
30800 constraint_handler_t
30802 which has the following definition
30804 typedef void (*constraint_handler_t)(
30805 const char * restrict msg,
30806 void * restrict ptr,
30810 <p><small><a href="#Contents">Contents</a></small>
30811 <h5><a name="K.3.6.1" href="#K.3.6.1">K.3.6.1 Runtime-constraint handling</a></h5>
30813 <p><small><a href="#Contents">Contents</a></small>
30814 <h5><a name="K.3.6.1.1" href="#K.3.6.1.1">K.3.6.1.1 The set_constraint_handler_s function</a></h5>
30816 <p><a name="K.3.6.1.1p1" href="#K.3.6.1.1p1"><small>1</small></a>
30818 #define __STDC_WANT_LIB_EXT1__ 1
30819 #include <a href="#7.22"><stdlib.h></a>
30820 constraint_handler_t set_constraint_handler_s(
30821 constraint_handler_t handler);
30823 <p><b>Description</b>
30824 <p><a name="K.3.6.1.1p2" href="#K.3.6.1.1p2"><small>2</small></a>
30825 The set_constraint_handler_s function sets the runtime-constraint handler to
30826 be handler. The runtime-constraint handler is the function to be called when a library
30827 function detects a runtime-constraint violation. Only the most recent handler registered
30828 with set_constraint_handler_s is called when a runtime-constraint violation
30830 <p><a name="K.3.6.1.1p3" href="#K.3.6.1.1p3"><small>3</small></a>
30831 When the handler is called, it is passed the following arguments in the following order:
30833 <li> A pointer to a character string describing the runtime-constraint violation.
30834 <li> A null pointer or a pointer to an implementation defined object.
30835 <li> If the function calling the handler has a return type declared as errno_t, the
30836 return value of the function is passed. Otherwise, a positive value of type
30840 <p><a name="K.3.6.1.1p4" href="#K.3.6.1.1p4"><small>4</small></a>
30841 The implementation has a default constraint handler that is used if no calls to the
30842 set_constraint_handler_s function have been made. The behavior of the
30843 default handler is implementation-defined, and it may cause the program to exit or abort.
30844 <p><a name="K.3.6.1.1p5" href="#K.3.6.1.1p5"><small>5</small></a>
30845 If the handler argument to set_constraint_handler_s is a null pointer, the
30846 implementation default handler becomes the current constraint handler.
30848 <p><a name="K.3.6.1.1p6" href="#K.3.6.1.1p6"><small>6</small></a>
30849 The set_constraint_handler_s function returns a pointer to the previously
30850 registered handler.<sup><a href="#note405"><b>405)</b></a></sup>
30852 <p><b>Footnotes</b>
30853 <p><small><a name="note405" href="#note405">405)</a> If the previous handler was registered by calling set_constraint_handler_s with a null
30854 pointer argument, a pointer to the implementation default handler is returned (not NULL).
30857 <p><small><a href="#Contents">Contents</a></small>
30858 <h5><a name="K.3.6.1.2" href="#K.3.6.1.2">K.3.6.1.2 The abort_handler_s function</a></h5>
30860 <p><a name="K.3.6.1.2p1" href="#K.3.6.1.2p1"><small>1</small></a>
30862 #define __STDC_WANT_LIB_EXT1__ 1
30863 #include <a href="#7.22"><stdlib.h></a>
30864 void abort_handler_s(
30865 const char * restrict msg,
30866 void * restrict ptr,
30869 <p><b>Description</b>
30870 <p><a name="K.3.6.1.2p2" href="#K.3.6.1.2p2"><small>2</small></a>
30871 A pointer to the abort_handler_s function shall be a suitable argument to the
30872 set_constraint_handler_s function.
30873 <p><a name="K.3.6.1.2p3" href="#K.3.6.1.2p3"><small>3</small></a>
30874 The abort_handler_s function writes a message on the standard error stream in an
30875 implementation-defined format. The message shall include the string pointed to by msg.
30876 The abort_handler_s function then calls the abort function.<sup><a href="#note406"><b>406)</b></a></sup>
30878 <p><a name="K.3.6.1.2p4" href="#K.3.6.1.2p4"><small>4</small></a>
30879 The abort_handler_s function does not return to its caller.
30886 <p><b>Footnotes</b>
30887 <p><small><a name="note406" href="#note406">406)</a> Many implementations invoke a debugger when the abort function is called.
30890 <p><small><a href="#Contents">Contents</a></small>
30891 <h5><a name="K.3.6.1.3" href="#K.3.6.1.3">K.3.6.1.3 The ignore_handler_s function</a></h5>
30893 <p><a name="K.3.6.1.3p1" href="#K.3.6.1.3p1"><small>1</small></a>
30895 #define __STDC_WANT_LIB_EXT1__ 1
30896 #include <a href="#7.22"><stdlib.h></a>
30897 void ignore_handler_s(
30898 const char * restrict msg,
30899 void * restrict ptr,
30902 <p><b>Description</b>
30903 <p><a name="K.3.6.1.3p2" href="#K.3.6.1.3p2"><small>2</small></a>
30904 A pointer to the ignore_handler_s function shall be a suitable argument to the
30905 set_constraint_handler_s function.
30906 <p><a name="K.3.6.1.3p3" href="#K.3.6.1.3p3"><small>3</small></a>
30907 The ignore_handler_s function simply returns to its caller.<sup><a href="#note407"><b>407)</b></a></sup>
30909 <p><a name="K.3.6.1.3p4" href="#K.3.6.1.3p4"><small>4</small></a>
30910 The ignore_handler_s function returns no value.
30912 <p><b>Footnotes</b>
30913 <p><small><a name="note407" href="#note407">407)</a> If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
30914 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
30915 a runtime-constraint violation occurred based on the library function's specification (usually, the
30916 library function returns a nonzero errno_t).
30919 <p><small><a href="#Contents">Contents</a></small>
30920 <h5><a name="K.3.6.2" href="#K.3.6.2">K.3.6.2 Communication with the environment</a></h5>
30922 <p><small><a href="#Contents">Contents</a></small>
30923 <h5><a name="K.3.6.2.1" href="#K.3.6.2.1">K.3.6.2.1 The getenv_s function</a></h5>
30925 <p><a name="K.3.6.2.1p1" href="#K.3.6.2.1p1"><small>1</small></a>
30927 #define __STDC_WANT_LIB_EXT1__ 1
30928 #include <a href="#7.22"><stdlib.h></a>
30929 errno_t getenv_s(size_t * restrict len,
30930 char * restrict value, rsize_t maxsize,
30931 const char * restrict name);
30933 Runtime-constraints
30934 <p><a name="K.3.6.2.1p2" href="#K.3.6.2.1p2"><small>2</small></a>
30935 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
30936 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
30937 <p><a name="K.3.6.2.1p3" href="#K.3.6.2.1p3"><small>3</small></a>
30938 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
30939 is not null), and the environment list is not searched.
30940 <p><b>Description</b>
30941 <p><a name="K.3.6.2.1p4" href="#K.3.6.2.1p4"><small>4</small></a>
30942 The getenv_s function searches an environment list, provided by the host environment,
30943 for a string that matches the string pointed to by name.
30947 <p><a name="K.3.6.2.1p5" href="#K.3.6.2.1p5"><small>5</small></a>
30948 If that name is found then getenv_s performs the following actions. If len is not a
30949 null pointer, the length of the string associated with the matched list member is stored in
30950 the integer pointed to by len. If the length of the associated string is less than maxsize,
30951 then the associated string is copied to the array pointed to by value.
30952 <p><a name="K.3.6.2.1p6" href="#K.3.6.2.1p6"><small>6</small></a>
30953 If that name is not found then getenv_s performs the following actions. If len is not
30954 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
30955 zero, then value[0] is set to the null character.
30956 <p><a name="K.3.6.2.1p7" href="#K.3.6.2.1p7"><small>7</small></a>
30957 The set of environment names and the method for altering the environment list are
30958 implementation-defined. The getenv_s function need not avoid data races with other
30959 threads of execution that modify the environment list.<sup><a href="#note408"><b>408)</b></a></sup>
30961 <p><a name="K.3.6.2.1p8" href="#K.3.6.2.1p8"><small>8</small></a>
30962 The getenv_s function returns zero if the specified name is found and the associated
30963 string was successfully stored in value. Otherwise, a nonzero value is returned.
30965 <p><b>Footnotes</b>
30966 <p><small><a name="note408" href="#note408">408)</a> Many implementations provide non-standard functions that modify the environment list.
30969 <p><small><a href="#Contents">Contents</a></small>
30970 <h5><a name="K.3.6.3" href="#K.3.6.3">K.3.6.3 Searching and sorting utilities</a></h5>
30971 <p><a name="K.3.6.3p1" href="#K.3.6.3p1"><small>1</small></a>
30972 These utilities make use of a comparison function to search or sort arrays of unspecified
30973 type. Where an argument declared as size_t nmemb specifies the length of the array
30974 for a function, if nmemb has the value zero on a call to that function, then the comparison
30975 function is not called, a search finds no matching element, sorting performs no
30976 rearrangement, and the pointer to the array may be null.
30977 <p><a name="K.3.6.3p2" href="#K.3.6.3p2"><small>2</small></a>
30978 The implementation shall ensure that the second argument of the comparison function
30979 (when called from bsearch_s), or both arguments (when called from qsort_s), are
30980 pointers to elements of the array.<sup><a href="#note409"><b>409)</b></a></sup> The first argument when called from bsearch_s
30982 <p><a name="K.3.6.3p3" href="#K.3.6.3p3"><small>3</small></a>
30983 The comparison function shall not alter the contents of either the array or search key. The
30984 implementation may reorder elements of the array between calls to the comparison
30985 function, but shall not otherwise alter the contents of any individual element.
30986 <p><a name="K.3.6.3p4" href="#K.3.6.3p4"><small>4</small></a>
30987 When the same objects (consisting of size bytes, irrespective of their current positions
30988 in the array) are passed more than once to the comparison function, the results shall be
30989 consistent with one another. That is, for qsort_s they shall define a total ordering on
30990 the array, and for bsearch_s the same object shall always compare the same way with
30994 <p><a name="K.3.6.3p5" href="#K.3.6.3p5"><small>5</small></a>
30995 A sequence point occurs immediately before and immediately after each call to the
30996 comparison function, and also between any call to the comparison function and any
30997 movement of the objects passed as arguments to that call.
30999 <p><b>Footnotes</b>
31000 <p><small><a name="note409" href="#note409">409)</a> That is, if the value passed is p, then the following expressions are always valid and nonzero:
31003 ((char *)p - (char *)base) % size == 0
31004 (char *)p >= (char *)base
31005 (char *)p < (char *)base + nmemb * size
31009 <p><small><a href="#Contents">Contents</a></small>
31010 <h5><a name="K.3.6.3.1" href="#K.3.6.3.1">K.3.6.3.1 The bsearch_s function</a></h5>
31012 <p><a name="K.3.6.3.1p1" href="#K.3.6.3.1p1"><small>1</small></a>
31014 #define __STDC_WANT_LIB_EXT1__ 1
31015 #include <a href="#7.22"><stdlib.h></a>
31016 void *bsearch_s(const void *key, const void *base,
31017 rsize_t nmemb, rsize_t size,
31018 int (*compar)(const void *k, const void *y,
31022 Runtime-constraints
31023 <p><a name="K.3.6.3.1p2" href="#K.3.6.3.1p2"><small>2</small></a>
31024 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
31025 zero, then none of key, base, or compar shall be a null pointer.
31026 <p><a name="K.3.6.3.1p3" href="#K.3.6.3.1p3"><small>3</small></a>
31027 If there is a runtime-constraint violation, the bsearch_s function does not search the
31029 <p><b>Description</b>
31030 <p><a name="K.3.6.3.1p4" href="#K.3.6.3.1p4"><small>4</small></a>
31031 The bsearch_s function searches an array of nmemb objects, the initial element of
31032 which is pointed to by base, for an element that matches the object pointed to by key.
31033 The size of each element of the array is specified by size.
31034 <p><a name="K.3.6.3.1p5" href="#K.3.6.3.1p5"><small>5</small></a>
31035 The comparison function pointed to by compar is called with three arguments. The first
31036 two point to the key object and to an array element, in that order. The function shall
31037 return an integer less than, equal to, or greater than zero if the key object is considered,
31038 respectively, to be less than, to match, or to be greater than the array element. The array
31039 shall consist of: all the elements that compare less than, all the elements that compare
31040 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note410"><b>410)</b></a></sup>
31041 The third argument to the comparison function is the context argument passed to
31042 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
31043 function.<sup><a href="#note411"><b>411)</b></a></sup>
31050 <p><a name="K.3.6.3.1p6" href="#K.3.6.3.1p6"><small>6</small></a>
31051 The bsearch_s function returns a pointer to a matching element of the array, or a null
31052 pointer if no match is found or there is a runtime-constraint violation. If two elements
31053 compare as equal, which element is matched is unspecified.
31055 <p><b>Footnotes</b>
31056 <p><small><a name="note410" href="#note410">410)</a> In practice, this means that the entire array has been sorted according to the comparison function.
31058 <p><small><a name="note411" href="#note411">411)</a> The context argument is for the use of the comparison function in performing its duties. For
31059 example, it might specify a collating sequence used by the comparison function.
31062 <p><small><a href="#Contents">Contents</a></small>
31063 <h5><a name="K.3.6.3.2" href="#K.3.6.3.2">K.3.6.3.2 The qsort_s function</a></h5>
31065 <p><a name="K.3.6.3.2p1" href="#K.3.6.3.2p1"><small>1</small></a>
31067 #define __STDC_WANT_LIB_EXT1__ 1
31068 #include <a href="#7.22"><stdlib.h></a>
31069 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
31070 int (*compar)(const void *x, const void *y,
31074 Runtime-constraints
31075 <p><a name="K.3.6.3.2p2" href="#K.3.6.3.2p2"><small>2</small></a>
31076 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
31077 zero, then neither base nor compar shall be a null pointer.
31078 <p><a name="K.3.6.3.2p3" href="#K.3.6.3.2p3"><small>3</small></a>
31079 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
31080 <p><b>Description</b>
31081 <p><a name="K.3.6.3.2p4" href="#K.3.6.3.2p4"><small>4</small></a>
31082 The qsort_s function sorts an array of nmemb objects, the initial element of which is
31083 pointed to by base. The size of each object is specified by size.
31084 <p><a name="K.3.6.3.2p5" href="#K.3.6.3.2p5"><small>5</small></a>
31085 The contents of the array are sorted into ascending order according to a comparison
31086 function pointed to by compar, which is called with three arguments. The first two
31087 point to the objects being compared. The function shall return an integer less than, equal
31088 to, or greater than zero if the first argument is considered to be respectively less than,
31089 equal to, or greater than the second. The third argument to the comparison function is the
31090 context argument passed to qsort_s. The sole use of context by qsort_s is to
31091 pass it to the comparison function.<sup><a href="#note412"><b>412)</b></a></sup>
31092 <p><a name="K.3.6.3.2p6" href="#K.3.6.3.2p6"><small>6</small></a>
31093 If two elements compare as equal, their relative order in the resulting sorted array is
31096 <p><a name="K.3.6.3.2p7" href="#K.3.6.3.2p7"><small>7</small></a>
31097 The qsort_s function returns zero if there was no runtime-constraint violation.
31098 Otherwise, a nonzero value is returned.
31105 <p><b>Footnotes</b>
31106 <p><small><a name="note412" href="#note412">412)</a> The context argument is for the use of the comparison function in performing its duties. For
31107 example, it might specify a collating sequence used by the comparison function.
31110 <p><small><a href="#Contents">Contents</a></small>
31111 <h5><a name="K.3.6.4" href="#K.3.6.4">K.3.6.4 Multibyte/wide character conversion functions</a></h5>
31112 <p><a name="K.3.6.4p1" href="#K.3.6.4p1"><small>1</small></a>
31113 The behavior of the multibyte character functions is affected by the LC_CTYPE category
31114 of the current locale. For a state-dependent encoding, each function is placed into its
31115 initial conversion state by a call for which its character pointer argument, s, is a null
31116 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
31117 state of the function to be altered as necessary. A call with s as a null pointer causes
31118 these functions to set the int pointed to by their status argument to a nonzero value if
31119 encodings have state dependency, and zero otherwise.<sup><a href="#note413"><b>413)</b></a></sup> Changing the LC_CTYPE
31120 category causes the conversion state of these functions to be indeterminate.
31122 <p><b>Footnotes</b>
31123 <p><small><a name="note413" href="#note413">413)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
31124 character codes, but are grouped with an adjacent multibyte character.
31127 <p><small><a href="#Contents">Contents</a></small>
31128 <h5><a name="K.3.6.4.1" href="#K.3.6.4.1">K.3.6.4.1 The wctomb_s function</a></h5>
31130 <p><a name="K.3.6.4.1p1" href="#K.3.6.4.1p1"><small>1</small></a>
31132 #define __STDC_WANT_LIB_EXT1__ 1
31133 #include <a href="#7.22"><stdlib.h></a>
31134 errno_t wctomb_s(int * restrict status,
31139 Runtime-constraints
31140 <p><a name="K.3.6.4.1p2" href="#K.3.6.4.1p2"><small>2</small></a>
31141 Let n denote the number of bytes needed to represent the multibyte character
31142 corresponding to the wide character given by wc (including any shift sequences).
31143 <p><a name="K.3.6.4.1p3" href="#K.3.6.4.1p3"><small>3</small></a>
31144 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
31145 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
31146 <p><a name="K.3.6.4.1p4" href="#K.3.6.4.1p4"><small>4</small></a>
31147 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
31148 by status, and if s is not a null pointer, no more than smax elements in the array
31149 pointed to by s will be accessed.
31150 <p><b>Description</b>
31151 <p><a name="K.3.6.4.1p5" href="#K.3.6.4.1p5"><small>5</small></a>
31152 The wctomb_s function determines n and stores the multibyte character representation
31153 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
31154 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
31155 character, a null byte is stored, preceded by any shift sequence needed to restore the
31156 initial shift state, and the function is left in the initial conversion state.
31157 <p><a name="K.3.6.4.1p6" href="#K.3.6.4.1p6"><small>6</small></a>
31158 The implementation shall behave as if no library function calls the wctomb_s function.
31163 <p><a name="K.3.6.4.1p7" href="#K.3.6.4.1p7"><small>7</small></a>
31164 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
31165 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
31166 state-dependent encodings.
31167 <p><a name="K.3.6.4.1p8" href="#K.3.6.4.1p8"><small>8</small></a>
31168 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
31169 status either n or -1 if wc, respectively, does or does not correspond to a valid
31170 multibyte character.
31171 <p><a name="K.3.6.4.1p9" href="#K.3.6.4.1p9"><small>9</small></a>
31172 In no case will the int pointed to by status be set to a value greater than the
31175 <p><a name="K.3.6.4.1p10" href="#K.3.6.4.1p10"><small>10</small></a>
31176 The wctomb_s function returns zero if successful, and a nonzero value if there was a
31177 runtime-constraint violation or wc did not correspond to a valid multibyte character.
31179 <p><small><a href="#Contents">Contents</a></small>
31180 <h5><a name="K.3.6.5" href="#K.3.6.5">K.3.6.5 Multibyte/wide string conversion functions</a></h5>
31181 <p><a name="K.3.6.5p1" href="#K.3.6.5p1"><small>1</small></a>
31182 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
31183 the current locale.
31185 <p><small><a href="#Contents">Contents</a></small>
31186 <h5><a name="K.3.6.5.1" href="#K.3.6.5.1">K.3.6.5.1 The mbstowcs_s function</a></h5>
31188 <p><a name="K.3.6.5.1p1" href="#K.3.6.5.1p1"><small>1</small></a>
31190 #include <a href="#7.22"><stdlib.h></a>
31191 errno_t mbstowcs_s(size_t * restrict retval,
31192 wchar_t * restrict dst, rsize_t dstmax,
31193 const char * restrict src, rsize_t len);
31195 Runtime-constraints
31196 <p><a name="K.3.6.5.1p2" href="#K.3.6.5.1p2"><small>2</small></a>
31197 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
31198 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
31199 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
31200 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
31201 shall occur within the first dstmax multibyte characters of the array pointed to by src.
31202 <p><a name="K.3.6.5.1p3" href="#K.3.6.5.1p3"><small>3</small></a>
31203 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
31204 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
31205 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
31206 then mbstowcs_s sets dst[0] to the null wide character.
31207 <p><b>Description</b>
31208 <p><a name="K.3.6.5.1p4" href="#K.3.6.5.1p4"><small>4</small></a>
31209 The mbstowcs_s function converts a sequence of multibyte characters that begins in
31210 the initial shift state from the array pointed to by src into a sequence of corresponding
31211 wide characters. If dst is not a null pointer, the converted characters are stored into the
31212 array pointed to by dst. Conversion continues up to and including a terminating null
31213 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
31215 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
31216 null pointer) when len wide characters have been stored into the array pointed to by
31217 dst.<sup><a href="#note414"><b>414)</b></a></sup> If dst is not a null pointer and no null wide character was stored into the array
31218 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
31219 takes place as if by a call to the mbrtowc function.
31220 <p><a name="K.3.6.5.1p5" href="#K.3.6.5.1p5"><small>5</small></a>
31221 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
31222 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
31223 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
31224 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
31225 characters successfully converted, not including the terminating null character (if any).
31226 <p><a name="K.3.6.5.1p6" href="#K.3.6.5.1p6"><small>6</small></a>
31227 All elements following the terminating null wide character (if any) written by
31228 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
31229 unspecified values when mbstowcs_s returns.<sup><a href="#note415"><b>415)</b></a></sup>
31230 <p><a name="K.3.6.5.1p7" href="#K.3.6.5.1p7"><small>7</small></a>
31231 If copying takes place between objects that overlap, the objects take on unspecified
31234 <p><a name="K.3.6.5.1p8" href="#K.3.6.5.1p8"><small>8</small></a>
31235 The mbstowcs_s function returns zero if no runtime-constraint violation and no
31236 encoding error occurred. Otherwise, a nonzero value is returned.
31238 <p><b>Footnotes</b>
31239 <p><small><a name="note414" href="#note414">414)</a> Thus, the value of len is ignored if dst is a null pointer.
31241 <p><small><a name="note415" href="#note415">415)</a> This allows an implementation to attempt converting the multibyte string before discovering a
31242 terminating null character did not occur where required.
31245 <p><small><a href="#Contents">Contents</a></small>
31246 <h5><a name="K.3.6.5.2" href="#K.3.6.5.2">K.3.6.5.2 The wcstombs_s function</a></h5>
31248 <p><a name="K.3.6.5.2p1" href="#K.3.6.5.2p1"><small>1</small></a>
31250 #include <a href="#7.22"><stdlib.h></a>
31251 errno_t wcstombs_s(size_t * restrict retval,
31252 char * restrict dst, rsize_t dstmax,
31253 const wchar_t * restrict src, rsize_t len);
31255 Runtime-constraints
31256 <p><a name="K.3.6.5.2p2" href="#K.3.6.5.2p2"><small>2</small></a>
31257 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
31258 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
31259 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
31260 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
31261 shall have been stopped (see below) because a terminating null wide character was
31262 reached or because an encoding error occurred.
31268 <p><a name="K.3.6.5.2p3" href="#K.3.6.5.2p3"><small>3</small></a>
31269 If there is a runtime-constraint violation, then wcstombs_s does the following. If
31270 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
31271 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
31272 then wcstombs_s sets dst[0] to the null character.
31273 <p><b>Description</b>
31274 <p><a name="K.3.6.5.2p4" href="#K.3.6.5.2p4"><small>4</small></a>
31275 The wcstombs_s function converts a sequence of wide characters from the array
31276 pointed to by src into a sequence of corresponding multibyte characters that begins in
31277 the initial shift state. If dst is not a null pointer, the converted characters are then stored
31278 into the array pointed to by dst. Conversion continues up to and including a terminating
31279 null wide character, which is also stored. Conversion stops earlier in two cases:
31281 <li> when a wide character is reached that does not correspond to a valid multibyte
31283 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
31284 limit of n total bytes to be stored into the array pointed to by dst. If the wide
31285 character being converted is the null wide character, then n is the lesser of len or
31286 dstmax. Otherwise, n is the lesser of len or dstmax-1.
31288 If the conversion stops without converting a null wide character and dst is not a null
31289 pointer, then a null character is stored into the array pointed to by dst immediately
31290 following any multibyte characters already stored. Each conversion takes place as if by a
31291 call to the wcrtomb function.<sup><a href="#note416"><b>416)</b></a></sup>
31292 <p><a name="K.3.6.5.2p5" href="#K.3.6.5.2p5"><small>5</small></a>
31293 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
31294 wide character that does not correspond to a valid multibyte character, an encoding error
31295 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
31296 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
31297 resulting multibyte character sequence, not including the terminating null character (if
31299 <p><a name="K.3.6.5.2p6" href="#K.3.6.5.2p6"><small>6</small></a>
31300 All elements following the terminating null character (if any) written by wcstombs_s
31301 in the array of dstmax elements pointed to by dst take unspecified values when
31302 wcstombs_s returns.<sup><a href="#note417"><b>417)</b></a></sup>
31303 <p><a name="K.3.6.5.2p7" href="#K.3.6.5.2p7"><small>7</small></a>
31304 If copying takes place between objects that overlap, the objects take on unspecified
31310 <p><a name="K.3.6.5.2p8" href="#K.3.6.5.2p8"><small>8</small></a>
31311 The wcstombs_s function returns zero if no runtime-constraint violation and no
31312 encoding error occurred. Otherwise, a nonzero value is returned.
31314 <p><b>Footnotes</b>
31315 <p><small><a name="note416" href="#note416">416)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
31316 include those necessary to reach the initial shift state immediately before the null byte. However, if
31317 the conversion stops before a terminating null wide character has been reached, the result will be null
31318 terminated, but might not end in the initial shift state.
31320 <p><small><a name="note417" href="#note417">417)</a> When len is not less than dstmax, the implementation might fill the array before discovering a
31321 runtime-constraint violation.
31324 <p><small><a href="#Contents">Contents</a></small>
31325 <h4><a name="K.3.7" href="#K.3.7">K.3.7 String handling <string.h></a></h4>
31326 <p><a name="K.3.7p1" href="#K.3.7p1"><small>1</small></a>
31327 The header <a href="#7.24"><string.h></a> defines two types.
31328 <p><a name="K.3.7p2" href="#K.3.7p2"><small>2</small></a>
31333 which is type int; and
31337 which is the type size_t.
31339 <p><small><a href="#Contents">Contents</a></small>
31340 <h5><a name="K.3.7.1" href="#K.3.7.1">K.3.7.1 Copying functions</a></h5>
31342 <p><small><a href="#Contents">Contents</a></small>
31343 <h5><a name="K.3.7.1.1" href="#K.3.7.1.1">K.3.7.1.1 The memcpy_s function</a></h5>
31345 <p><a name="K.3.7.1.1p1" href="#K.3.7.1.1p1"><small>1</small></a>
31347 #define __STDC_WANT_LIB_EXT1__ 1
31348 #include <a href="#7.24"><string.h></a>
31349 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
31350 const void * restrict s2, rsize_t n);
31352 Runtime-constraints
31353 <p><a name="K.3.7.1.1p2" href="#K.3.7.1.1p2"><small>2</small></a>
31354 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31355 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
31356 objects that overlap.
31357 <p><a name="K.3.7.1.1p3" href="#K.3.7.1.1p3"><small>3</small></a>
31358 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
31359 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
31360 not greater than RSIZE_MAX.
31361 <p><b>Description</b>
31362 <p><a name="K.3.7.1.1p4" href="#K.3.7.1.1p4"><small>4</small></a>
31363 The memcpy_s function copies n characters from the object pointed to by s2 into the
31364 object pointed to by s1.
31366 <p><a name="K.3.7.1.1p5" href="#K.3.7.1.1p5"><small>5</small></a>
31367 The memcpy_s function returns zero if there was no runtime-constraint violation.
31368 Otherwise, a nonzero value is returned.
31371 <p><small><a href="#Contents">Contents</a></small>
31372 <h5><a name="K.3.7.1.2" href="#K.3.7.1.2">K.3.7.1.2 The memmove_s function</a></h5>
31374 <p><a name="K.3.7.1.2p1" href="#K.3.7.1.2p1"><small>1</small></a>
31376 #define __STDC_WANT_LIB_EXT1__ 1
31377 #include <a href="#7.24"><string.h></a>
31378 errno_t memmove_s(void *s1, rsize_t s1max,
31379 const void *s2, rsize_t n);
31381 Runtime-constraints
31382 <p><a name="K.3.7.1.2p2" href="#K.3.7.1.2p2"><small>2</small></a>
31383 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31384 RSIZE_MAX. n shall not be greater than s1max.
31385 <p><a name="K.3.7.1.2p3" href="#K.3.7.1.2p3"><small>3</small></a>
31386 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
31387 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
31388 s1max is not greater than RSIZE_MAX.
31389 <p><b>Description</b>
31390 <p><a name="K.3.7.1.2p4" href="#K.3.7.1.2p4"><small>4</small></a>
31391 The memmove_s function copies n characters from the object pointed to by s2 into the
31392 object pointed to by s1. This copying takes place as if the n characters from the object
31393 pointed to by s2 are first copied into a temporary array of n characters that does not
31394 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
31395 array are copied into the object pointed to by s1.
31397 <p><a name="K.3.7.1.2p5" href="#K.3.7.1.2p5"><small>5</small></a>
31398 The memmove_s function returns zero if there was no runtime-constraint violation.
31399 Otherwise, a nonzero value is returned.
31401 <p><small><a href="#Contents">Contents</a></small>
31402 <h5><a name="K.3.7.1.3" href="#K.3.7.1.3">K.3.7.1.3 The strcpy_s function</a></h5>
31404 <p><a name="K.3.7.1.3p1" href="#K.3.7.1.3p1"><small>1</small></a>
31406 #define __STDC_WANT_LIB_EXT1__ 1
31407 #include <a href="#7.24"><string.h></a>
31408 errno_t strcpy_s(char * restrict s1,
31410 const char * restrict s2);
31412 Runtime-constraints
31413 <p><a name="K.3.7.1.3p2" href="#K.3.7.1.3p2"><small>2</small></a>
31414 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31415 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
31416 Copying shall not take place between objects that overlap.
31417 <p><a name="K.3.7.1.3p3" href="#K.3.7.1.3p3"><small>3</small></a>
31418 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31419 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
31422 <p><b>Description</b>
31423 <p><a name="K.3.7.1.3p4" href="#K.3.7.1.3p4"><small>4</small></a>
31424 The strcpy_s function copies the string pointed to by s2 (including the terminating
31425 null character) into the array pointed to by s1.
31426 <p><a name="K.3.7.1.3p5" href="#K.3.7.1.3p5"><small>5</small></a>
31427 All elements following the terminating null character (if any) written by strcpy_s in
31428 the array of s1max characters pointed to by s1 take unspecified values when
31429 strcpy_s returns.<sup><a href="#note418"><b>418)</b></a></sup>
31431 <p><a name="K.3.7.1.3p6" href="#K.3.7.1.3p6"><small>6</small></a>
31432 The strcpy_s function returns zero<sup><a href="#note419"><b>419)</b></a></sup> if there was no runtime-constraint violation.
31433 Otherwise, a nonzero value is returned.
31435 <p><b>Footnotes</b>
31436 <p><small><a name="note418" href="#note418">418)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
31437 any of those characters are null. Such an approach might write a character to every element of s1
31438 before discovering that the first element should be set to the null character.
31440 <p><small><a name="note419" href="#note419">419)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
31441 within the array pointed to by s1 and that the result in s1 is null terminated.
31444 <p><small><a href="#Contents">Contents</a></small>
31445 <h5><a name="K.3.7.1.4" href="#K.3.7.1.4">K.3.7.1.4 The strncpy_s function</a></h5>
31447 <p><a name="K.3.7.1.4p1" href="#K.3.7.1.4p1"><small>1</small></a>
31449 #define __STDC_WANT_LIB_EXT1__ 1
31450 #include <a href="#7.24"><string.h></a>
31451 errno_t strncpy_s(char * restrict s1,
31453 const char * restrict s2,
31456 Runtime-constraints
31457 <p><a name="K.3.7.1.4p2" href="#K.3.7.1.4p2"><small>2</small></a>
31458 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31459 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
31460 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
31461 objects that overlap.
31462 <p><a name="K.3.7.1.4p3" href="#K.3.7.1.4p3"><small>3</small></a>
31463 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31464 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
31466 <p><b>Description</b>
31467 <p><a name="K.3.7.1.4p4" href="#K.3.7.1.4p4"><small>4</small></a>
31468 The strncpy_s function copies not more than n successive characters (characters that
31469 follow a null character are not copied) from the array pointed to by s2 to the array
31470 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
31475 <p><a name="K.3.7.1.4p5" href="#K.3.7.1.4p5"><small>5</small></a>
31476 All elements following the terminating null character (if any) written by strncpy_s in
31477 the array of s1max characters pointed to by s1 take unspecified values when
31478 strncpy_s returns.<sup><a href="#note420"><b>420)</b></a></sup>
31480 <p><a name="K.3.7.1.4p6" href="#K.3.7.1.4p6"><small>6</small></a>
31481 The strncpy_s function returns zero<sup><a href="#note421"><b>421)</b></a></sup> if there was no runtime-constraint violation.
31482 Otherwise, a nonzero value is returned.
31483 <p><a name="K.3.7.1.4p7" href="#K.3.7.1.4p7"><small>7</small></a>
31484 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
31485 will not be null terminated or that characters will be written past the end of the destination array.
31487 #define __STDC_WANT_LIB_EXT1__ 1
31488 #include <a href="#7.24"><string.h></a>
31490 char src1[100] = "hello";
31491 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
31492 char dst1[6], dst2[5], dst3[5];
31494 r1 = strncpy_s(dst1, 6, src1, 100);
31495 r2 = strncpy_s(dst2, 5, src2, 7);
31496 r3 = strncpy_s(dst3, 5, src2, 4);
31498 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
31499 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
31500 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
31503 <p><b>Footnotes</b>
31504 <p><small><a name="note420" href="#note420">420)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
31505 any of those characters are null. Such an approach might write a character to every element of s1
31506 before discovering that the first element should be set to the null character.
31508 <p><small><a name="note421" href="#note421">421)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
31509 within the array pointed to by s1 and that the result in s1 is null terminated.
31512 <p><small><a href="#Contents">Contents</a></small>
31513 <h5><a name="K.3.7.2" href="#K.3.7.2">K.3.7.2 Concatenation functions</a></h5>
31515 <p><small><a href="#Contents">Contents</a></small>
31516 <h5><a name="K.3.7.2.1" href="#K.3.7.2.1">K.3.7.2.1 The strcat_s function</a></h5>
31518 <p><a name="K.3.7.2.1p1" href="#K.3.7.2.1p1"><small>1</small></a>
31520 #define __STDC_WANT_LIB_EXT1__ 1
31521 #include <a href="#7.24"><string.h></a>
31522 errno_t strcat_s(char * restrict s1,
31524 const char * restrict s2);
31526 Runtime-constraints
31527 <p><a name="K.3.7.2.1p2" href="#K.3.7.2.1p2"><small>2</small></a>
31528 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
31535 <p><a name="K.3.7.2.1p3" href="#K.3.7.2.1p3"><small>3</small></a>
31536 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31537 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note422"><b>422)</b></a></sup> m shall be greater than
31538 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
31539 <p><a name="K.3.7.2.1p4" href="#K.3.7.2.1p4"><small>4</small></a>
31540 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31541 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
31543 <p><b>Description</b>
31544 <p><a name="K.3.7.2.1p5" href="#K.3.7.2.1p5"><small>5</small></a>
31545 The strcat_s function appends a copy of the string pointed to by s2 (including the
31546 terminating null character) to the end of the string pointed to by s1. The initial character
31547 from s2 overwrites the null character at the end of s1.
31548 <p><a name="K.3.7.2.1p6" href="#K.3.7.2.1p6"><small>6</small></a>
31549 All elements following the terminating null character (if any) written by strcat_s in
31550 the array of s1max characters pointed to by s1 take unspecified values when
31551 strcat_s returns.<sup><a href="#note423"><b>423)</b></a></sup>
31553 <p><a name="K.3.7.2.1p7" href="#K.3.7.2.1p7"><small>7</small></a>
31554 The strcat_s function returns zero<sup><a href="#note424"><b>424)</b></a></sup> if there was no runtime-constraint violation.
31555 Otherwise, a nonzero value is returned.
31557 <p><b>Footnotes</b>
31558 <p><small><a name="note422" href="#note422">422)</a> Zero means that s1 was not null terminated upon entry to strcat_s.
31560 <p><small><a name="note423" href="#note423">423)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
31561 any of those characters are null. Such an approach might write a character to every element of s1
31562 before discovering that the first element should be set to the null character.
31564 <p><small><a name="note424" href="#note424">424)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 were
31565 appended to the string pointed to by s1 and that the result in s1 is null terminated.
31568 <p><small><a href="#Contents">Contents</a></small>
31569 <h5><a name="K.3.7.2.2" href="#K.3.7.2.2">K.3.7.2.2 The strncat_s function</a></h5>
31571 <p><a name="K.3.7.2.2p1" href="#K.3.7.2.2p1"><small>1</small></a>
31573 #define __STDC_WANT_LIB_EXT1__ 1
31574 #include <a href="#7.24"><string.h></a>
31575 errno_t strncat_s(char * restrict s1,
31577 const char * restrict s2,
31580 Runtime-constraints
31581 <p><a name="K.3.7.2.2p2" href="#K.3.7.2.2p2"><small>2</small></a>
31582 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
31584 <p><a name="K.3.7.2.2p3" href="#K.3.7.2.2p3"><small>3</small></a>
31585 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31586 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note425"><b>425)</b></a></sup> If n is not less
31590 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
31591 place between objects that overlap.
31592 <p><a name="K.3.7.2.2p4" href="#K.3.7.2.2p4"><small>4</small></a>
31593 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31594 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
31596 <p><b>Description</b>
31597 <p><a name="K.3.7.2.2p5" href="#K.3.7.2.2p5"><small>5</small></a>
31598 The strncat_s function appends not more than n successive characters (characters
31599 that follow a null character are not copied) from the array pointed to by s2 to the end of
31600 the string pointed to by s1. The initial character from s2 overwrites the null character at
31601 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
31603 <p><a name="K.3.7.2.2p6" href="#K.3.7.2.2p6"><small>6</small></a>
31604 All elements following the terminating null character (if any) written by strncat_s in
31605 the array of s1max characters pointed to by s1 take unspecified values when
31606 strncat_s returns.<sup><a href="#note426"><b>426)</b></a></sup>
31608 <p><a name="K.3.7.2.2p7" href="#K.3.7.2.2p7"><small>7</small></a>
31609 The strncat_s function returns zero<sup><a href="#note427"><b>427)</b></a></sup> if there was no runtime-constraint violation.
31610 Otherwise, a nonzero value is returned.
31611 <p><a name="K.3.7.2.2p8" href="#K.3.7.2.2p8"><small>8</small></a>
31612 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
31613 will not be null terminated or that characters will be written past the end of the destination array.
31615 #define __STDC_WANT_LIB_EXT1__ 1
31616 #include <a href="#7.24"><string.h></a>
31618 char s1[100] = "good";
31619 char s2[6] = "hello";
31620 char s3[6] = "hello";
31621 char s4[7] = "abc";
31622 char s5[1000] = "bye";
31623 int r1, r2, r3, r4;
31624 r1 = strncat_s(s1, 100, s5, 1000);
31625 r2 = strncat_s(s2, 6, "", 1);
31626 r3 = strncat_s(s3, 6, "X", 2);
31627 r4 = strncat_s(s4, 7, "defghijklmn", 3);
31629 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
31634 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
31635 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
31636 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
31639 <p><b>Footnotes</b>
31640 <p><small><a name="note425" href="#note425">425)</a> Zero means that s1 was not null terminated upon entry to strncat_s.
31642 <p><small><a name="note426" href="#note426">426)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
31643 any of those characters are null. Such an approach might write a character to every element of s1
31644 before discovering that the first element should be set to the null character.
31646 <p><small><a name="note427" href="#note427">427)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 were
31647 appended to the string pointed to by s1 and that the result in s1 is null terminated.
31650 <p><small><a href="#Contents">Contents</a></small>
31651 <h5><a name="K.3.7.3" href="#K.3.7.3">K.3.7.3 Search functions</a></h5>
31653 <p><small><a href="#Contents">Contents</a></small>
31654 <h5><a name="K.3.7.3.1" href="#K.3.7.3.1">K.3.7.3.1 The strtok_s function</a></h5>
31656 <p><a name="K.3.7.3.1p1" href="#K.3.7.3.1p1"><small>1</small></a>
31658 #define __STDC_WANT_LIB_EXT1__ 1
31659 #include <a href="#7.24"><string.h></a>
31660 char *strtok_s(char * restrict s1,
31661 rsize_t * restrict s1max,
31662 const char * restrict s2,
31663 char ** restrict ptr);
31665 Runtime-constraints
31666 <p><a name="K.3.7.3.1p2" href="#K.3.7.3.1p2"><small>2</small></a>
31667 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
31668 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
31669 The end of the token found shall occur within the first *s1max characters of s1 for the
31670 first call, and shall occur within the first *s1max characters of where searching resumes
31671 on subsequent calls.
31672 <p><a name="K.3.7.3.1p3" href="#K.3.7.3.1p3"><small>3</small></a>
31673 If there is a runtime-constraint violation, the strtok_s function does not indirect
31674 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
31675 <p><b>Description</b>
31676 <p><a name="K.3.7.3.1p4" href="#K.3.7.3.1p4"><small>4</small></a>
31677 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
31678 sequence of tokens, each of which is delimited by a character from the string pointed to
31679 by s2. The fourth argument points to a caller-provided char pointer into which the
31680 strtok_s function stores information necessary for it to continue scanning the same
31682 <p><a name="K.3.7.3.1p5" href="#K.3.7.3.1p5"><small>5</small></a>
31683 The first call in a sequence has a non-null first argument and s1max points to an object
31684 whose value is the number of elements in the character array pointed to by the first
31685 argument. The first call stores an initial value in the object pointed to by ptr and
31686 updates the value pointed to by s1max to reflect the number of elements that remain in
31687 relation to ptr. Subsequent calls in the sequence have a null first argument and the
31688 objects pointed to by s1max and ptr are required to have the values stored by the
31689 previous call in the sequence, which are then updated. The separator string pointed to by
31690 s2 may be different from call to call.
31691 <p><a name="K.3.7.3.1p6" href="#K.3.7.3.1p6"><small>6</small></a>
31692 The first call in the sequence searches the string pointed to by s1 for the first character
31693 that is not contained in the current separator string pointed to by s2. If no such character
31694 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
31695 function returns a null pointer. If such a character is found, it is the start of the first token.
31697 <p><a name="K.3.7.3.1p7" href="#K.3.7.3.1p7"><small>7</small></a>
31698 The strtok_s function then searches from there for the first character in s1 that is
31699 contained in the current separator string. If no such character is found, the current token
31700 extends to the end of the string pointed to by s1, and subsequent searches in the same
31701 string for a token return a null pointer. If such a character is found, it is overwritten by a
31702 null character, which terminates the current token.
31703 <p><a name="K.3.7.3.1p8" href="#K.3.7.3.1p8"><small>8</small></a>
31704 In all cases, the strtok_s function stores sufficient information in the pointer pointed
31705 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
31706 value for ptr, shall start searching just past the element overwritten by a null character
31709 <p><a name="K.3.7.3.1p9" href="#K.3.7.3.1p9"><small>9</small></a>
31710 The strtok_s function returns a pointer to the first character of a token, or a null
31711 pointer if there is no token or there is a runtime-constraint violation.
31712 <p><a name="K.3.7.3.1p10" href="#K.3.7.3.1p10"><small>10</small></a>
31715 #define __STDC_WANT_LIB_EXT1__ 1
31716 #include <a href="#7.24"><string.h></a>
31717 static char str1[] = "?a???b,,,#c";
31718 static char str2[] = "\t \t";
31719 char *t, *ptr1, *ptr2;
31720 rsize_t max1 = sizeof (str1);
31721 rsize_t max2 = sizeof (str2);
31722 t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
31723 t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
31724 t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
31725 t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
31726 t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
31730 <p><small><a href="#Contents">Contents</a></small>
31731 <h5><a name="K.3.7.4" href="#K.3.7.4">K.3.7.4 Miscellaneous functions</a></h5>
31733 <p><small><a href="#Contents">Contents</a></small>
31734 <h5><a name="K.3.7.4.1" href="#K.3.7.4.1">K.3.7.4.1 The memset_s function</a></h5>
31736 <p><a name="K.3.7.4.1p1" href="#K.3.7.4.1p1"><small>1</small></a>
31738 #define __STDC_WANT_LIB_EXT1__ 1
31739 #include <a href="#7.24"><string.h></a>
31740 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
31742 Runtime-constraints
31743 <p><a name="K.3.7.4.1p2" href="#K.3.7.4.1p2"><small>2</small></a>
31744 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
31745 shall not be greater than smax.
31746 <p><a name="K.3.7.4.1p3" href="#K.3.7.4.1p3"><small>3</small></a>
31747 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
31748 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
31749 unsigned char) into each of the first smax characters of the object pointed to by s.
31751 <p><b>Description</b>
31752 <p><a name="K.3.7.4.1p4" href="#K.3.7.4.1p4"><small>4</small></a>
31753 The memset_s function copies the value of c (converted to an unsigned char) into
31754 each of the first n characters of the object pointed to by s. Unlike memset, any call to
31755 the memset_s function shall be evaluated strictly according to the rules of the abstract
31756 machine as described in (<a href="#5.1.2.3">5.1.2.3</a>). That is, any call to the memset_s function shall
31757 assume that the memory indicated by s and n may be accessible in the future and thus
31758 must contain the values indicated by c.
31760 <p><a name="K.3.7.4.1p5" href="#K.3.7.4.1p5"><small>5</small></a>
31761 The memset_s function returns zero if there was no runtime-constraint violation.
31762 Otherwise, a nonzero value is returned.
31764 <p><small><a href="#Contents">Contents</a></small>
31765 <h5><a name="K.3.7.4.2" href="#K.3.7.4.2">K.3.7.4.2 The strerror_s function</a></h5>
31767 <p><a name="K.3.7.4.2p1" href="#K.3.7.4.2p1"><small>1</small></a>
31769 #define __STDC_WANT_LIB_EXT1__ 1
31770 #include <a href="#7.24"><string.h></a>
31771 errno_t strerror_s(char *s, rsize_t maxsize,
31774 Runtime-constraints
31775 <p><a name="K.3.7.4.2p2" href="#K.3.7.4.2p2"><small>2</small></a>
31776 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
31777 maxsize shall not equal zero.
31778 <p><a name="K.3.7.4.2p3" href="#K.3.7.4.2p3"><small>3</small></a>
31779 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
31781 <p><b>Description</b>
31782 <p><a name="K.3.7.4.2p4" href="#K.3.7.4.2p4"><small>4</small></a>
31783 The strerror_s function maps the number in errnum to a locale-specific message
31784 string. Typically, the values for errnum come from errno, but strerror_s shall
31785 map any value of type int to a message.
31786 <p><a name="K.3.7.4.2p5" href="#K.3.7.4.2p5"><small>5</small></a>
31787 If the length of the desired string is less than maxsize, then the string is copied to the
31788 array pointed to by s.
31789 <p><a name="K.3.7.4.2p6" href="#K.3.7.4.2p6"><small>6</small></a>
31790 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
31791 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
31792 character. Then, if maxsize is greater than 3, then s[maxsize-2],
31793 s[maxsize-3], and s[maxsize-4] are set to the character period (.).
31795 <p><a name="K.3.7.4.2p7" href="#K.3.7.4.2p7"><small>7</small></a>
31796 The strerror_s function returns zero if the length of the desired string was less than
31797 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
31798 function returns a nonzero value.
31801 <p><small><a href="#Contents">Contents</a></small>
31802 <h5><a name="K.3.7.4.3" href="#K.3.7.4.3">K.3.7.4.3 The strerrorlen_s function</a></h5>
31804 <p><a name="K.3.7.4.3p1" href="#K.3.7.4.3p1"><small>1</small></a>
31806 #define __STDC_WANT_LIB_EXT1__ 1
31807 #include <a href="#7.24"><string.h></a>
31808 size_t strerrorlen_s(errno_t errnum);
31810 <p><b>Description</b>
31811 <p><a name="K.3.7.4.3p2" href="#K.3.7.4.3p2"><small>2</small></a>
31812 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
31813 message string that the strerror_s function maps to errnum.
31815 <p><a name="K.3.7.4.3p3" href="#K.3.7.4.3p3"><small>3</small></a>
31816 The strerrorlen_s function returns the number of characters (not including the null
31817 character) in the full message string.
31819 <p><small><a href="#Contents">Contents</a></small>
31820 <h5><a name="K.3.7.4.4" href="#K.3.7.4.4">K.3.7.4.4 The strnlen_s function</a></h5>
31822 <p><a name="K.3.7.4.4p1" href="#K.3.7.4.4p1"><small>1</small></a>
31824 #define __STDC_WANT_LIB_EXT1__ 1
31825 #include <a href="#7.24"><string.h></a>
31826 size_t strnlen_s(const char *s, size_t maxsize);
31828 <p><b>Description</b>
31829 <p><a name="K.3.7.4.4p2" href="#K.3.7.4.4p2"><small>2</small></a>
31830 The strnlen_s function computes the length of the string pointed to by s.
31832 <p><a name="K.3.7.4.4p3" href="#K.3.7.4.4p3"><small>3</small></a>
31833 If s is a null pointer,<sup><a href="#note428"><b>428)</b></a></sup> then the strnlen_s function returns zero.
31834 <p><a name="K.3.7.4.4p4" href="#K.3.7.4.4p4"><small>4</small></a>
31835 Otherwise, the strnlen_s function returns the number of characters that precede the
31836 terminating null character. If there is no null character in the first maxsize characters of
31837 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
31838 be accessed by strnlen_s.
31845 <p><b>Footnotes</b>
31846 <p><small><a name="note428" href="#note428">428)</a> Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
31847 along with the values returned for a null pointer or an unterminated string argument make
31848 strnlen_s useful in algorithms that gracefully handle such exceptional data.
31851 <p><small><a href="#Contents">Contents</a></small>
31852 <h4><a name="K.3.8" href="#K.3.8">K.3.8 Date and time <time.h></a></h4>
31853 <p><a name="K.3.8p1" href="#K.3.8p1"><small>1</small></a>
31854 The header <a href="#7.27"><time.h></a> defines two types.
31855 <p><a name="K.3.8p2" href="#K.3.8p2"><small>2</small></a>
31860 which is type int; and
31864 which is the type size_t.
31866 <p><small><a href="#Contents">Contents</a></small>
31867 <h5><a name="K.3.8.1" href="#K.3.8.1">K.3.8.1 Components of time</a></h5>
31868 <p><a name="K.3.8.1p1" href="#K.3.8.1p1"><small>1</small></a>
31869 A broken-down time is normalized if the values of the members of the tm structure are in
31870 their normal rages.<sup><a href="#note429"><b>429)</b></a></sup>
31872 <p><b>Footnotes</b>
31873 <p><small><a name="note429" href="#note429">429)</a> The normal ranges are defined in <a href="#7.27.1">7.27.1</a>.
31876 <p><small><a href="#Contents">Contents</a></small>
31877 <h5><a name="K.3.8.2" href="#K.3.8.2">K.3.8.2 Time conversion functions</a></h5>
31878 <p><a name="K.3.8.2p1" href="#K.3.8.2p1"><small>1</small></a>
31879 Like the strftime function, the asctime_s and ctime_s functions do not return a
31880 pointer to a static object, and other library functions are permitted to call them.
31882 <p><small><a href="#Contents">Contents</a></small>
31883 <h5><a name="K.3.8.2.1" href="#K.3.8.2.1">K.3.8.2.1 The asctime_s function</a></h5>
31885 <p><a name="K.3.8.2.1p1" href="#K.3.8.2.1p1"><small>1</small></a>
31887 #define __STDC_WANT_LIB_EXT1__ 1
31888 #include <a href="#7.27"><time.h></a>
31889 errno_t asctime_s(char *s, rsize_t maxsize,
31890 const struct tm *timeptr);
31892 Runtime-constraints
31893 <p><a name="K.3.8.2.1p2" href="#K.3.8.2.1p2"><small>2</small></a>
31894 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
31895 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
31896 shall be normalized. The calendar year represented by the broken-down time pointed to
31897 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
31899 <p><a name="K.3.8.2.1p3" href="#K.3.8.2.1p3"><small>3</small></a>
31900 If there is a runtime-constraint violation, there is no attempt to convert the time, and
31901 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
31902 not greater than RSIZE_MAX.
31903 <p><b>Description</b>
31904 <p><a name="K.3.8.2.1p4" href="#K.3.8.2.1p4"><small>4</small></a>
31905 The asctime_s function converts the normalized broken-down time in the structure
31906 pointed to by timeptr into a 26 character (including the null character) string in the
31912 Sun Sep 16 01:03:52 1973\n\0
31914 The fields making up this string are (in order):
31916 <li> The name of the day of the week represented by timeptr->tm_wday using the
31917 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
31918 <li> The character space.
31919 <li> The name of the month represented by timeptr->tm_mon using the following
31920 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
31922 <li> The character space.
31923 <li> The value of timeptr->tm_mday as if printed using the fprintf format
31925 <li> The character space.
31926 <li> The value of timeptr->tm_hour as if printed using the fprintf format
31928 <li> The character colon.
31929 <li> The value of timeptr->tm_min as if printed using the fprintf format
31931 <li> The character colon.
31932 <li> The value of timeptr->tm_sec as if printed using the fprintf format
31934 <li> The character space.
31935 <li> The value of timeptr->tm_year + 1900 as if printed using the fprintf
31937 <li> The character new line.
31938 <li> The null character.
31940 <p><b>Recommended practice</b>
31941 The strftime function allows more flexible formatting and supports locale-specific
31942 behavior. If you do not require the exact form of the result string produced by the
31943 asctime_s function, consider using the strftime function instead.
31945 <p><a name="K.3.8.2.1p5" href="#K.3.8.2.1p5"><small>5</small></a>
31946 The asctime_s function returns zero if the time was successfully converted and stored
31947 into the array pointed to by s. Otherwise, it returns a nonzero value.
31950 <p><small><a href="#Contents">Contents</a></small>
31951 <h5><a name="K.3.8.2.2" href="#K.3.8.2.2">K.3.8.2.2 The ctime_s function</a></h5>
31953 <p><a name="K.3.8.2.2p1" href="#K.3.8.2.2p1"><small>1</small></a>
31955 #define __STDC_WANT_LIB_EXT1__ 1
31956 #include <a href="#7.27"><time.h></a>
31957 errno_t ctime_s(char *s, rsize_t maxsize,
31958 const time_t *timer);
31960 Runtime-constraints
31961 <p><a name="K.3.8.2.2p2" href="#K.3.8.2.2p2"><small>2</small></a>
31962 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
31963 shall not be greater than RSIZE_MAX.
31964 <p><a name="K.3.8.2.2p3" href="#K.3.8.2.2p3"><small>3</small></a>
31965 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
31966 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
31967 <p><b>Description</b>
31968 <p><a name="K.3.8.2.2p4" href="#K.3.8.2.2p4"><small>4</small></a>
31969 The ctime_s function converts the calendar time pointed to by timer to local time in
31970 the form of a string. It is equivalent to
31972 asctime_s(s, maxsize, localtime_s(timer))
31974 <p><b>Recommended practice</b>
31975 The strftime function allows more flexible formatting and supports locale-specific
31976 behavior. If you do not require the exact form of the result string produced by the
31977 ctime_s function, consider using the strftime function instead.
31979 <p><a name="K.3.8.2.2p5" href="#K.3.8.2.2p5"><small>5</small></a>
31980 The ctime_s function returns zero if the time was successfully converted and stored
31981 into the array pointed to by s. Otherwise, it returns a nonzero value.
31983 <p><small><a href="#Contents">Contents</a></small>
31984 <h5><a name="K.3.8.2.3" href="#K.3.8.2.3">K.3.8.2.3 The gmtime_s function</a></h5>
31986 <p><a name="K.3.8.2.3p1" href="#K.3.8.2.3p1"><small>1</small></a>
31988 #define __STDC_WANT_LIB_EXT1__ 1
31989 #include <a href="#7.27"><time.h></a>
31990 struct tm *gmtime_s(const time_t * restrict timer,
31991 struct tm * restrict result);
31993 Runtime-constraints
31994 <p><a name="K.3.8.2.3p2" href="#K.3.8.2.3p2"><small>2</small></a>
31995 Neither timer nor result shall be a null pointer.
31996 <p><a name="K.3.8.2.3p3" href="#K.3.8.2.3p3"><small>3</small></a>
31997 If there is a runtime-constraint violation, there is no attempt to convert the time.
31998 <p><b>Description</b>
31999 <p><a name="K.3.8.2.3p4" href="#K.3.8.2.3p4"><small>4</small></a>
32000 The gmtime_s function converts the calendar time pointed to by timer into a broken-
32001 down time, expressed as UTC. The broken-down time is stored in the structure pointed
32005 <p><a name="K.3.8.2.3p5" href="#K.3.8.2.3p5"><small>5</small></a>
32006 The gmtime_s function returns result, or a null pointer if the specified time cannot
32007 be converted to UTC or there is a runtime-constraint violation.
32009 <p><small><a href="#Contents">Contents</a></small>
32010 <h5><a name="K.3.8.2.4" href="#K.3.8.2.4">K.3.8.2.4 The localtime_s function</a></h5>
32012 <p><a name="K.3.8.2.4p1" href="#K.3.8.2.4p1"><small>1</small></a>
32014 #define __STDC_WANT_LIB_EXT1__ 1
32015 #include <a href="#7.27"><time.h></a>
32016 struct tm *localtime_s(const time_t * restrict timer,
32017 struct tm * restrict result);
32019 Runtime-constraints
32020 <p><a name="K.3.8.2.4p2" href="#K.3.8.2.4p2"><small>2</small></a>
32021 Neither timer nor result shall be a null pointer.
32022 <p><a name="K.3.8.2.4p3" href="#K.3.8.2.4p3"><small>3</small></a>
32023 If there is a runtime-constraint violation, there is no attempt to convert the time.
32024 <p><b>Description</b>
32025 <p><a name="K.3.8.2.4p4" href="#K.3.8.2.4p4"><small>4</small></a>
32026 The localtime_s function converts the calendar time pointed to by timer into a
32027 broken-down time, expressed as local time. The broken-down time is stored in the
32028 structure pointed to by result.
32030 <p><a name="K.3.8.2.4p5" href="#K.3.8.2.4p5"><small>5</small></a>
32031 The localtime_s function returns result, or a null pointer if the specified time
32032 cannot be converted to local time or there is a runtime-constraint violation.
32034 <p><small><a href="#Contents">Contents</a></small>
32035 <h4><a name="K.3.9" href="#K.3.9">K.3.9 Extended multibyte and wide character utilities <wchar.h></a></h4>
32036 <p><a name="K.3.9p1" href="#K.3.9p1"><small>1</small></a>
32037 The header <a href="#7.29"><wchar.h></a> defines two types.
32038 <p><a name="K.3.9p2" href="#K.3.9p2"><small>2</small></a>
32043 which is type int; and
32047 which is the type size_t.
32048 <p><a name="K.3.9p3" href="#K.3.9p3"><small>3</small></a>
32049 Unless explicitly stated otherwise, if the execution of a function described in this
32050 subclause causes copying to take place between objects that overlap, the objects take on
32051 unspecified values.
32054 <p><small><a href="#Contents">Contents</a></small>
32055 <h5><a name="K.3.9.1" href="#K.3.9.1">K.3.9.1 Formatted wide character input/output functions</a></h5>
32057 <p><small><a href="#Contents">Contents</a></small>
32058 <h5><a name="K.3.9.1.1" href="#K.3.9.1.1">K.3.9.1.1 The fwprintf_s function</a></h5>
32060 <p><a name="K.3.9.1.1p1" href="#K.3.9.1.1p1"><small>1</small></a>
32062 #define __STDC_WANT_LIB_EXT1__ 1
32063 #include <a href="#7.29"><wchar.h></a>
32064 int fwprintf_s(FILE * restrict stream,
32065 const wchar_t * restrict format, ...);
32067 Runtime-constraints
32068 <p><a name="K.3.9.1.1p2" href="#K.3.9.1.1p2"><small>2</small></a>
32069 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note430"><b>430)</b></a></sup> (modified or
32070 not by flags, field width, or precision) shall not appear in the wide string pointed to by
32071 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
32073 <p><a name="K.3.9.1.1p3" href="#K.3.9.1.1p3"><small>3</small></a>
32074 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
32075 produce further output, and it is unspecified to what extent fwprintf_s produced
32076 output before discovering the runtime-constraint violation.
32077 <p><b>Description</b>
32078 <p><a name="K.3.9.1.1p4" href="#K.3.9.1.1p4"><small>4</small></a>
32079 The fwprintf_s function is equivalent to the fwprintf function except for the
32080 explicit runtime-constraints listed above.
32082 <p><a name="K.3.9.1.1p5" href="#K.3.9.1.1p5"><small>5</small></a>
32083 The fwprintf_s function returns the number of wide characters transmitted, or a
32084 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32086 <p><b>Footnotes</b>
32087 <p><small><a name="note430" href="#note430">430)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32088 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32089 example, if the entire format string was L"%%n".
32092 <p><small><a href="#Contents">Contents</a></small>
32093 <h5><a name="K.3.9.1.2" href="#K.3.9.1.2">K.3.9.1.2 The fwscanf_s function</a></h5>
32095 <p><a name="K.3.9.1.2p1" href="#K.3.9.1.2p1"><small>1</small></a>
32097 #define __STDC_WANT_LIB_EXT1__ 1
32098 #include <a href="#7.21"><stdio.h></a>
32099 #include <a href="#7.29"><wchar.h></a>
32100 int fwscanf_s(FILE * restrict stream,
32101 const wchar_t * restrict format, ...);
32103 Runtime-constraints
32104 <p><a name="K.3.9.1.2p2" href="#K.3.9.1.2p2"><small>2</small></a>
32105 Neither stream nor format shall be a null pointer. Any argument indirected though in
32106 order to store converted input shall not be a null pointer.
32110 <p><a name="K.3.9.1.2p3" href="#K.3.9.1.2p3"><small>3</small></a>
32111 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
32112 perform further input, and it is unspecified to what extent fwscanf_s performed input
32113 before discovering the runtime-constraint violation.
32114 <p><b>Description</b>
32115 <p><a name="K.3.9.1.2p4" href="#K.3.9.1.2p4"><small>4</small></a>
32116 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
32117 conversion specifiers apply to a pair of arguments (unless assignment suppression is
32118 indicated by a *). The first of these arguments is the same as for fwscanf. That
32119 argument is immediately followed in the argument list by the second argument, which has
32120 type size_t and gives the number of elements in the array pointed to by the first
32121 argument of the pair. If the first argument points to a scalar object, it is considered to be
32122 an array of one element.<sup><a href="#note431"><b>431)</b></a></sup>
32123 <p><a name="K.3.9.1.2p5" href="#K.3.9.1.2p5"><small>5</small></a>
32124 A matching failure occurs if the number of elements in a receiving object is insufficient to
32125 hold the converted input (including any trailing null character).
32127 <p><a name="K.3.9.1.2p6" href="#K.3.9.1.2p6"><small>6</small></a>
32128 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
32129 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32130 fwscanf_s function returns the number of input items assigned, which can be fewer
32131 than provided for, or even zero, in the event of an early matching failure.
32133 <p><b>Footnotes</b>
32134 <p><small><a name="note431" href="#note431">431)</a> If the format is known at translation time, an implementation may issue a diagnostic for any argument
32135 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
32136 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
32137 the format is not known at translation time. For example, an implementation may issue a diagnostic
32138 for each argument after format that has of type pointer to one of char, signed char,
32139 unsigned char, or void that is not followed by an argument of a type compatible with
32140 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
32141 using the hh length modifier, a length argument must follow the pointer argument. Another useful
32142 diagnostic could flag any non-pointer argument following format that did not have a type
32143 compatible with rsize_t.
32146 <p><small><a href="#Contents">Contents</a></small>
32147 <h5><a name="K.3.9.1.3" href="#K.3.9.1.3">K.3.9.1.3 The snwprintf_s function</a></h5>
32149 <p><a name="K.3.9.1.3p1" href="#K.3.9.1.3p1"><small>1</small></a>
32151 #define __STDC_WANT_LIB_EXT1__ 1
32152 #include <a href="#7.29"><wchar.h></a>
32153 int snwprintf_s(wchar_t * restrict s,
32155 const wchar_t * restrict format, ...);
32157 Runtime-constraints
32158 <p><a name="K.3.9.1.3p2" href="#K.3.9.1.3p2"><small>2</small></a>
32159 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32160 than RSIZE_MAX. The %n specifier<sup><a href="#note432"><b>432)</b></a></sup> (modified or not by flags, field width, or
32163 precision) shall not appear in the wide string pointed to by format. Any argument to
32164 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
32166 <p><a name="K.3.9.1.3p3" href="#K.3.9.1.3p3"><small>3</small></a>
32167 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32168 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
32169 null wide character.
32170 <p><b>Description</b>
32171 <p><a name="K.3.9.1.3p4" href="#K.3.9.1.3p4"><small>4</small></a>
32172 The snwprintf_s function is equivalent to the swprintf function except for the
32173 explicit runtime-constraints listed above.
32174 <p><a name="K.3.9.1.3p5" href="#K.3.9.1.3p5"><small>5</small></a>
32175 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
32176 the array pointed to by s.
32178 <p><a name="K.3.9.1.3p6" href="#K.3.9.1.3p6"><small>6</small></a>
32179 The snwprintf_s function returns the number of wide characters that would have
32180 been written had n been sufficiently large, not counting the terminating wide null
32181 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
32182 terminated output has been completely written if and only if the returned value is
32183 nonnegative and less than n.
32185 <p><b>Footnotes</b>
32186 <p><small><a name="note432" href="#note432">432)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32187 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32188 example, if the entire format string was L"%%n".
32191 <p><small><a href="#Contents">Contents</a></small>
32192 <h5><a name="K.3.9.1.4" href="#K.3.9.1.4">K.3.9.1.4 The swprintf_s function</a></h5>
32194 <p><a name="K.3.9.1.4p1" href="#K.3.9.1.4p1"><small>1</small></a>
32196 #define __STDC_WANT_LIB_EXT1__ 1
32197 #include <a href="#7.29"><wchar.h></a>
32198 int swprintf_s(wchar_t * restrict s, rsize_t n,
32199 const wchar_t * restrict format, ...);
32201 Runtime-constraints
32202 <p><a name="K.3.9.1.4p2" href="#K.3.9.1.4p2"><small>2</small></a>
32203 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32204 than RSIZE_MAX. The number of wide characters (including the trailing null) required
32205 for the result to be written to the array pointed to by s shall not be greater than n. The %n
32206 specifier<sup><a href="#note433"><b>433)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
32207 wide string pointed to by format. Any argument to swprintf_s corresponding to a
32208 %s specifier shall not be a null pointer. No encoding error shall occur.
32212 <p><a name="K.3.9.1.4p3" href="#K.3.9.1.4p3"><small>3</small></a>
32213 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32214 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
32215 null wide character.
32216 <p><b>Description</b>
32217 <p><a name="K.3.9.1.4p4" href="#K.3.9.1.4p4"><small>4</small></a>
32218 The swprintf_s function is equivalent to the swprintf function except for the
32219 explicit runtime-constraints listed above.
32220 <p><a name="K.3.9.1.4p5" href="#K.3.9.1.4p5"><small>5</small></a>
32221 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
32222 pointed to by s as a runtime-constraint violation.
32224 <p><a name="K.3.9.1.4p6" href="#K.3.9.1.4p6"><small>6</small></a>
32225 If no runtime-constraint violation occurred, the swprintf_s function returns the
32226 number of wide characters written in the array, not counting the terminating null wide
32227 character. If an encoding error occurred or if n or more wide characters are requested to
32228 be written, swprintf_s returns a negative value. If any other runtime-constraint
32229 violation occurred, swprintf_s returns zero.
32231 <p><b>Footnotes</b>
32232 <p><small><a name="note433" href="#note433">433)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32233 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32234 example, if the entire format string was L"%%n".
32237 <p><small><a href="#Contents">Contents</a></small>
32238 <h5><a name="K.3.9.1.5" href="#K.3.9.1.5">K.3.9.1.5 The swscanf_s function</a></h5>
32240 <p><a name="K.3.9.1.5p1" href="#K.3.9.1.5p1"><small>1</small></a>
32242 #define __STDC_WANT_LIB_EXT1__ 1
32243 #include <a href="#7.29"><wchar.h></a>
32244 int swscanf_s(const wchar_t * restrict s,
32245 const wchar_t * restrict format, ...);
32247 Runtime-constraints
32248 <p><a name="K.3.9.1.5p2" href="#K.3.9.1.5p2"><small>2</small></a>
32249 Neither s nor format shall be a null pointer. Any argument indirected though in order
32250 to store converted input shall not be a null pointer.
32251 <p><a name="K.3.9.1.5p3" href="#K.3.9.1.5p3"><small>3</small></a>
32252 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
32253 perform further input, and it is unspecified to what extent swscanf_s performed input
32254 before discovering the runtime-constraint violation.
32255 <p><b>Description</b>
32256 <p><a name="K.3.9.1.5p4" href="#K.3.9.1.5p4"><small>4</small></a>
32257 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
32258 specifies a wide string from which the input is to be obtained, rather than from a stream.
32259 Reaching the end of the wide string is equivalent to encountering end-of-file for the
32260 fwscanf_s function.
32262 <p><a name="K.3.9.1.5p5" href="#K.3.9.1.5p5"><small>5</small></a>
32263 The swscanf_s function returns the value of the macro EOF if an input failure occurs
32264 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32265 swscanf_s function returns the number of input items assigned, which can be fewer
32266 than provided for, or even zero, in the event of an early matching failure.
32269 <p><small><a href="#Contents">Contents</a></small>
32270 <h5><a name="K.3.9.1.6" href="#K.3.9.1.6">K.3.9.1.6 The vfwprintf_s function</a></h5>
32272 <p><a name="K.3.9.1.6p1" href="#K.3.9.1.6p1"><small>1</small></a>
32274 #define __STDC_WANT_LIB_EXT1__ 1
32275 #include <a href="#7.16"><stdarg.h></a>
32276 #include <a href="#7.21"><stdio.h></a>
32277 #include <a href="#7.29"><wchar.h></a>
32278 int vfwprintf_s(FILE * restrict stream,
32279 const wchar_t * restrict format,
32282 Runtime-constraints
32283 <p><a name="K.3.9.1.6p2" href="#K.3.9.1.6p2"><small>2</small></a>
32284 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note434"><b>434)</b></a></sup> (modified or
32285 not by flags, field width, or precision) shall not appear in the wide string pointed to by
32286 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
32288 <p><a name="K.3.9.1.6p3" href="#K.3.9.1.6p3"><small>3</small></a>
32289 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
32290 to produce further output, and it is unspecified to what extent vfwprintf_s produced
32291 output before discovering the runtime-constraint violation.
32292 <p><b>Description</b>
32293 <p><a name="K.3.9.1.6p4" href="#K.3.9.1.6p4"><small>4</small></a>
32294 The vfwprintf_s function is equivalent to the vfwprintf function except for the
32295 explicit runtime-constraints listed above.
32297 <p><a name="K.3.9.1.6p5" href="#K.3.9.1.6p5"><small>5</small></a>
32298 The vfwprintf_s function returns the number of wide characters transmitted, or a
32299 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32301 <p><b>Footnotes</b>
32302 <p><small><a name="note434" href="#note434">434)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32303 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32304 example, if the entire format string was L"%%n".
32307 <p><small><a href="#Contents">Contents</a></small>
32308 <h5><a name="K.3.9.1.7" href="#K.3.9.1.7">K.3.9.1.7 The vfwscanf_s function</a></h5>
32310 <p><a name="K.3.9.1.7p1" href="#K.3.9.1.7p1"><small>1</small></a>
32312 #define __STDC_WANT_LIB_EXT1__ 1
32313 #include <a href="#7.16"><stdarg.h></a>
32314 #include <a href="#7.21"><stdio.h></a>
32315 #include <a href="#7.29"><wchar.h></a>
32316 int vfwscanf_s(FILE * restrict stream,
32317 const wchar_t * restrict format, va_list arg);
32323 Runtime-constraints
32324 <p><a name="K.3.9.1.7p2" href="#K.3.9.1.7p2"><small>2</small></a>
32325 Neither stream nor format shall be a null pointer. Any argument indirected though in
32326 order to store converted input shall not be a null pointer.
32327 <p><a name="K.3.9.1.7p3" href="#K.3.9.1.7p3"><small>3</small></a>
32328 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
32329 perform further input, and it is unspecified to what extent vfwscanf_s performed input
32330 before discovering the runtime-constraint violation.
32331 <p><b>Description</b>
32332 <p><a name="K.3.9.1.7p4" href="#K.3.9.1.7p4"><small>4</small></a>
32333 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
32334 list replaced by arg, which shall have been initialized by the va_start macro (and
32335 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
32336 va_end macro.<sup><a href="#note435"><b>435)</b></a></sup>
32338 <p><a name="K.3.9.1.7p5" href="#K.3.9.1.7p5"><small>5</small></a>
32339 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
32340 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32341 vfwscanf_s function returns the number of input items assigned, which can be fewer
32342 than provided for, or even zero, in the event of an early matching failure.
32344 <p><b>Footnotes</b>
32345 <p><small><a name="note435" href="#note435">435)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32346 value of arg after the return is indeterminate.
32349 <p><small><a href="#Contents">Contents</a></small>
32350 <h5><a name="K.3.9.1.8" href="#K.3.9.1.8">K.3.9.1.8 The vsnwprintf_s function</a></h5>
32352 <p><a name="K.3.9.1.8p1" href="#K.3.9.1.8p1"><small>1</small></a>
32354 #define __STDC_WANT_LIB_EXT1__ 1
32355 #include <a href="#7.16"><stdarg.h></a>
32356 #include <a href="#7.29"><wchar.h></a>
32357 int vsnwprintf_s(wchar_t * restrict s,
32359 const wchar_t * restrict format,
32362 Runtime-constraints
32363 <p><a name="K.3.9.1.8p2" href="#K.3.9.1.8p2"><small>2</small></a>
32364 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32365 than RSIZE_MAX. The %n specifier<sup><a href="#note436"><b>436)</b></a></sup> (modified or not by flags, field width, or
32366 precision) shall not appear in the wide string pointed to by format. Any argument to
32367 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
32368 encoding error shall occur.
32371 <p><a name="K.3.9.1.8p3" href="#K.3.9.1.8p3"><small>3</small></a>
32372 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32373 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
32374 the null wide character.
32375 <p><b>Description</b>
32376 <p><a name="K.3.9.1.8p4" href="#K.3.9.1.8p4"><small>4</small></a>
32377 The vsnwprintf_s function is equivalent to the vswprintf function except for the
32378 explicit runtime-constraints listed above.
32379 <p><a name="K.3.9.1.8p5" href="#K.3.9.1.8p5"><small>5</small></a>
32380 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
32381 within the array pointed to by s.
32383 <p><a name="K.3.9.1.8p6" href="#K.3.9.1.8p6"><small>6</small></a>
32384 The vsnwprintf_s function returns the number of wide characters that would have
32385 been written had n been sufficiently large, not counting the terminating null character, or
32386 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
32387 output has been completely written if and only if the returned value is nonnegative and
32390 <p><b>Footnotes</b>
32391 <p><small><a name="note436" href="#note436">436)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32392 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32393 example, if the entire format string was L"%%n".
32396 <p><small><a href="#Contents">Contents</a></small>
32397 <h5><a name="K.3.9.1.9" href="#K.3.9.1.9">K.3.9.1.9 The vswprintf_s function</a></h5>
32399 <p><a name="K.3.9.1.9p1" href="#K.3.9.1.9p1"><small>1</small></a>
32401 #define __STDC_WANT_LIB_EXT1__ 1
32402 #include <a href="#7.16"><stdarg.h></a>
32403 #include <a href="#7.29"><wchar.h></a>
32404 int vswprintf_s(wchar_t * restrict s,
32406 const wchar_t * restrict format,
32409 Runtime-constraints
32410 <p><a name="K.3.9.1.9p2" href="#K.3.9.1.9p2"><small>2</small></a>
32411 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32412 than RSIZE_MAX. The number of wide characters (including the trailing null) required
32413 for the result to be written to the array pointed to by s shall not be greater than n. The %n
32414 specifier<sup><a href="#note437"><b>437)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
32415 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
32416 %s specifier shall not be a null pointer. No encoding error shall occur.
32417 <p><a name="K.3.9.1.9p3" href="#K.3.9.1.9p3"><small>3</small></a>
32418 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32419 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
32420 null wide character.
32423 <p><b>Description</b>
32424 <p><a name="K.3.9.1.9p4" href="#K.3.9.1.9p4"><small>4</small></a>
32425 The vswprintf_s function is equivalent to the vswprintf function except for the
32426 explicit runtime-constraints listed above.
32427 <p><a name="K.3.9.1.9p5" href="#K.3.9.1.9p5"><small>5</small></a>
32428 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
32429 array pointed to by s as a runtime-constraint violation.
32431 <p><a name="K.3.9.1.9p6" href="#K.3.9.1.9p6"><small>6</small></a>
32432 If no runtime-constraint violation occurred, the vswprintf_s function returns the
32433 number of wide characters written in the array, not counting the terminating null wide
32434 character. If an encoding error occurred or if n or more wide characters are requested to
32435 be written, vswprintf_s returns a negative value. If any other runtime-constraint
32436 violation occurred, vswprintf_s returns zero.
32438 <p><b>Footnotes</b>
32439 <p><small><a name="note437" href="#note437">437)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32440 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32441 example, if the entire format string was L"%%n".
32444 <p><small><a href="#Contents">Contents</a></small>
32445 <h5><a name="K.3.9.1.10" href="#K.3.9.1.10">K.3.9.1.10 The vswscanf_s function</a></h5>
32447 <p><a name="K.3.9.1.10p1" href="#K.3.9.1.10p1"><small>1</small></a>
32449 #define __STDC_WANT_LIB_EXT1__ 1
32450 #include <a href="#7.16"><stdarg.h></a>
32451 #include <a href="#7.29"><wchar.h></a>
32452 int vswscanf_s(const wchar_t * restrict s,
32453 const wchar_t * restrict format,
32456 Runtime-constraints
32457 <p><a name="K.3.9.1.10p2" href="#K.3.9.1.10p2"><small>2</small></a>
32458 Neither s nor format shall be a null pointer. Any argument indirected though in order
32459 to store converted input shall not be a null pointer.
32460 <p><a name="K.3.9.1.10p3" href="#K.3.9.1.10p3"><small>3</small></a>
32461 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
32462 perform further input, and it is unspecified to what extent vswscanf_s performed input
32463 before discovering the runtime-constraint violation.
32464 <p><b>Description</b>
32465 <p><a name="K.3.9.1.10p4" href="#K.3.9.1.10p4"><small>4</small></a>
32466 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
32467 list replaced by arg, which shall have been initialized by the va_start macro (and
32468 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
32469 va_end macro.<sup><a href="#note438"><b>438)</b></a></sup>
32476 <p><a name="K.3.9.1.10p5" href="#K.3.9.1.10p5"><small>5</small></a>
32477 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
32478 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32479 vswscanf_s function returns the number of input items assigned, which can be fewer
32480 than provided for, or even zero, in the event of an early matching failure.
32482 <p><b>Footnotes</b>
32483 <p><small><a name="note438" href="#note438">438)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32484 value of arg after the return is indeterminate.
32487 <p><small><a href="#Contents">Contents</a></small>
32488 <h5><a name="K.3.9.1.11" href="#K.3.9.1.11">K.3.9.1.11 The vwprintf_s function</a></h5>
32490 <p><a name="K.3.9.1.11p1" href="#K.3.9.1.11p1"><small>1</small></a>
32492 #define __STDC_WANT_LIB_EXT1__ 1
32493 #include <a href="#7.16"><stdarg.h></a>
32494 #include <a href="#7.29"><wchar.h></a>
32495 int vwprintf_s(const wchar_t * restrict format,
32498 Runtime-constraints
32499 <p><a name="K.3.9.1.11p2" href="#K.3.9.1.11p2"><small>2</small></a>
32500 format shall not be a null pointer. The %n specifier<sup><a href="#note439"><b>439)</b></a></sup> (modified or not by flags, field
32501 width, or precision) shall not appear in the wide string pointed to by format. Any
32502 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
32503 <p><a name="K.3.9.1.11p3" href="#K.3.9.1.11p3"><small>3</small></a>
32504 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
32505 produce further output, and it is unspecified to what extent vwprintf_s produced
32506 output before discovering the runtime-constraint violation.
32507 <p><b>Description</b>
32508 <p><a name="K.3.9.1.11p4" href="#K.3.9.1.11p4"><small>4</small></a>
32509 The vwprintf_s function is equivalent to the vwprintf function except for the
32510 explicit runtime-constraints listed above.
32512 <p><a name="K.3.9.1.11p5" href="#K.3.9.1.11p5"><small>5</small></a>
32513 The vwprintf_s function returns the number of wide characters transmitted, or a
32514 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32521 <p><b>Footnotes</b>
32522 <p><small><a name="note439" href="#note439">439)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32523 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32524 example, if the entire format string was L"%%n".
32527 <p><small><a href="#Contents">Contents</a></small>
32528 <h5><a name="K.3.9.1.12" href="#K.3.9.1.12">K.3.9.1.12 The vwscanf_s function</a></h5>
32530 <p><a name="K.3.9.1.12p1" href="#K.3.9.1.12p1"><small>1</small></a>
32532 #define __STDC_WANT_LIB_EXT1__ 1
32533 #include <a href="#7.16"><stdarg.h></a>
32534 #include <a href="#7.29"><wchar.h></a>
32535 int vwscanf_s(const wchar_t * restrict format,
32538 Runtime-constraints
32539 <p><a name="K.3.9.1.12p2" href="#K.3.9.1.12p2"><small>2</small></a>
32540 format shall not be a null pointer. Any argument indirected though in order to store
32541 converted input shall not be a null pointer.
32542 <p><a name="K.3.9.1.12p3" href="#K.3.9.1.12p3"><small>3</small></a>
32543 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
32544 perform further input, and it is unspecified to what extent vwscanf_s performed input
32545 before discovering the runtime-constraint violation.
32546 <p><b>Description</b>
32547 <p><a name="K.3.9.1.12p4" href="#K.3.9.1.12p4"><small>4</small></a>
32548 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
32549 replaced by arg, which shall have been initialized by the va_start macro (and
32550 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
32551 va_end macro.<sup><a href="#note440"><b>440)</b></a></sup>
32553 <p><a name="K.3.9.1.12p5" href="#K.3.9.1.12p5"><small>5</small></a>
32554 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
32555 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32556 vwscanf_s function returns the number of input items assigned, which can be fewer
32557 than provided for, or even zero, in the event of an early matching failure.
32559 <p><b>Footnotes</b>
32560 <p><small><a name="note440" href="#note440">440)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32561 value of arg after the return is indeterminate.
32564 <p><small><a href="#Contents">Contents</a></small>
32565 <h5><a name="K.3.9.1.13" href="#K.3.9.1.13">K.3.9.1.13 The wprintf_s function</a></h5>
32567 <p><a name="K.3.9.1.13p1" href="#K.3.9.1.13p1"><small>1</small></a>
32569 #define __STDC_WANT_LIB_EXT1__ 1
32570 #include <a href="#7.29"><wchar.h></a>
32571 int wprintf_s(const wchar_t * restrict format, ...);
32573 Runtime-constraints
32574 <p><a name="K.3.9.1.13p2" href="#K.3.9.1.13p2"><small>2</small></a>
32575 format shall not be a null pointer. The %n specifier<sup><a href="#note441"><b>441)</b></a></sup> (modified or not by flags, field
32578 width, or precision) shall not appear in the wide string pointed to by format. Any
32579 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
32580 <p><a name="K.3.9.1.13p3" href="#K.3.9.1.13p3"><small>3</small></a>
32581 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
32582 produce further output, and it is unspecified to what extent wprintf_s produced output
32583 before discovering the runtime-constraint violation.
32584 <p><b>Description</b>
32585 <p><a name="K.3.9.1.13p4" href="#K.3.9.1.13p4"><small>4</small></a>
32586 The wprintf_s function is equivalent to the wprintf function except for the explicit
32587 runtime-constraints listed above.
32589 <p><a name="K.3.9.1.13p5" href="#K.3.9.1.13p5"><small>5</small></a>
32590 The wprintf_s function returns the number of wide characters transmitted, or a
32591 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32593 <p><b>Footnotes</b>
32594 <p><small><a name="note441" href="#note441">441)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32595 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32596 example, if the entire format string was L"%%n".
32599 <p><small><a href="#Contents">Contents</a></small>
32600 <h5><a name="K.3.9.1.14" href="#K.3.9.1.14">K.3.9.1.14 The wscanf_s function</a></h5>
32602 <p><a name="K.3.9.1.14p1" href="#K.3.9.1.14p1"><small>1</small></a>
32604 #define __STDC_WANT_LIB_EXT1__ 1
32605 #include <a href="#7.29"><wchar.h></a>
32606 int wscanf_s(const wchar_t * restrict format, ...);
32608 Runtime-constraints
32609 <p><a name="K.3.9.1.14p2" href="#K.3.9.1.14p2"><small>2</small></a>
32610 format shall not be a null pointer. Any argument indirected though in order to store
32611 converted input shall not be a null pointer.
32612 <p><a name="K.3.9.1.14p3" href="#K.3.9.1.14p3"><small>3</small></a>
32613 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
32614 perform further input, and it is unspecified to what extent wscanf_s performed input
32615 before discovering the runtime-constraint violation.
32616 <p><b>Description</b>
32617 <p><a name="K.3.9.1.14p4" href="#K.3.9.1.14p4"><small>4</small></a>
32618 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
32619 interposed before the arguments to wscanf_s.
32621 <p><a name="K.3.9.1.14p5" href="#K.3.9.1.14p5"><small>5</small></a>
32622 The wscanf_s function returns the value of the macro EOF if an input failure occurs
32623 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32624 wscanf_s function returns the number of input items assigned, which can be fewer than
32625 provided for, or even zero, in the event of an early matching failure.
32628 <p><small><a href="#Contents">Contents</a></small>
32629 <h5><a name="K.3.9.2" href="#K.3.9.2">K.3.9.2 General wide string utilities</a></h5>
32631 <p><small><a href="#Contents">Contents</a></small>
32632 <h5><a name="K.3.9.2.1" href="#K.3.9.2.1">K.3.9.2.1 Wide string copying functions</a></h5>
32634 <p><small><a href="#Contents">Contents</a></small>
32635 <h5><a name="K.3.9.2.1.1" href="#K.3.9.2.1.1">K.3.9.2.1.1 The wcscpy_s function</a></h5>
32637 <p><a name="K.3.9.2.1.1p1" href="#K.3.9.2.1.1p1"><small>1</small></a>
32639 #define __STDC_WANT_LIB_EXT1__ 1
32640 #include <a href="#7.29"><wchar.h></a>
32641 errno_t wcscpy_s(wchar_t * restrict s1,
32643 const wchar_t * restrict s2);
32645 Runtime-constraints
32646 <p><a name="K.3.9.2.1.1p2" href="#K.3.9.2.1.1p2"><small>2</small></a>
32647 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
32648 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
32649 Copying shall not take place between objects that overlap.
32650 <p><a name="K.3.9.2.1.1p3" href="#K.3.9.2.1.1p3"><small>3</small></a>
32651 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32652 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
32653 null wide character.
32654 <p><b>Description</b>
32655 <p><a name="K.3.9.2.1.1p4" href="#K.3.9.2.1.1p4"><small>4</small></a>
32656 The wcscpy_s function copies the wide string pointed to by s2 (including the
32657 terminating null wide character) into the array pointed to by s1.
32658 <p><a name="K.3.9.2.1.1p5" href="#K.3.9.2.1.1p5"><small>5</small></a>
32659 All elements following the terminating null wide character (if any) written by
32660 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
32661 values when wcscpy_s returns.<sup><a href="#note442"><b>442)</b></a></sup>
32663 <p><a name="K.3.9.2.1.1p6" href="#K.3.9.2.1.1p6"><small>6</small></a>
32664 The wcscpy_s function returns zero<sup><a href="#note443"><b>443)</b></a></sup> if there was no runtime-constraint violation.
32665 Otherwise, a nonzero value is returned.
32672 <p><b>Footnotes</b>
32673 <p><small><a name="note442" href="#note442">442)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
32674 if any of those wide characters are null. Such an approach might write a wide character to every
32675 element of s1 before discovering that the first element should be set to the null wide character.
32677 <p><small><a name="note443" href="#note443">443)</a> A zero return value implies that all of the requested wide characters from the string pointed to by s2
32678 fit within the array pointed to by s1 and that the result in s1 is null terminated.
32681 <p><small><a href="#Contents">Contents</a></small>
32682 <h5><a name="K.3.9.2.1.2" href="#K.3.9.2.1.2">K.3.9.2.1.2 The wcsncpy_s function</a></h5>
32684 <p><a name="K.3.9.2.1.2p7" href="#K.3.9.2.1.2p7"><small>7</small></a>
32686 #define __STDC_WANT_LIB_EXT1__ 1
32687 #include <a href="#7.29"><wchar.h></a>
32688 errno_t wcsncpy_s(wchar_t * restrict s1,
32690 const wchar_t * restrict s2,
32693 Runtime-constraints
32694 <p><a name="K.3.9.2.1.2p8" href="#K.3.9.2.1.2p8"><small>8</small></a>
32695 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32696 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
32697 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
32698 objects that overlap.
32699 <p><a name="K.3.9.2.1.2p9" href="#K.3.9.2.1.2p9"><small>9</small></a>
32700 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32701 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
32702 null wide character.
32703 <p><b>Description</b>
32704 <p><a name="K.3.9.2.1.2p10" href="#K.3.9.2.1.2p10"><small>10</small></a>
32705 The wcsncpy_s function copies not more than n successive wide characters (wide
32706 characters that follow a null wide character are not copied) from the array pointed to by
32707 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
32708 s1[n] is set to a null wide character.
32709 <p><a name="K.3.9.2.1.2p11" href="#K.3.9.2.1.2p11"><small>11</small></a>
32710 All elements following the terminating null wide character (if any) written by
32711 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
32712 values when wcsncpy_s returns.<sup><a href="#note444"><b>444)</b></a></sup>
32714 <p><a name="K.3.9.2.1.2p12" href="#K.3.9.2.1.2p12"><small>12</small></a>
32715 The wcsncpy_s function returns zero<sup><a href="#note445"><b>445)</b></a></sup> if there was no runtime-constraint violation.
32716 Otherwise, a nonzero value is returned.
32717 <p><a name="K.3.9.2.1.2p13" href="#K.3.9.2.1.2p13"><small>13</small></a>
32718 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
32719 result will not be null terminated or that wide characters will be written past the end of the destination
32727 #define __STDC_WANT_LIB_EXT1__ 1
32728 #include <a href="#7.29"><wchar.h></a>
32730 wchar_t src1[100] = L"hello";
32731 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
32732 wchar_t dst1[6], dst2[5], dst3[5];
32734 r1 = wcsncpy_s(dst1, 6, src1, 100);
32735 r2 = wcsncpy_s(dst2, 5, src2, 7);
32736 r3 = wcsncpy_s(dst3, 5, src2, 4);
32738 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
32739 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
32740 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
32743 <p><b>Footnotes</b>
32744 <p><small><a name="note444" href="#note444">444)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
32745 if any of those wide characters are null. Such an approach might write a wide character to every
32746 element of s1 before discovering that the first element should be set to the null wide character.
32748 <p><small><a name="note445" href="#note445">445)</a> A zero return value implies that all of the requested wide characters from the string pointed to by s2
32749 fit within the array pointed to by s1 and that the result in s1 is null terminated.
32752 <p><small><a href="#Contents">Contents</a></small>
32753 <h5><a name="K.3.9.2.1.3" href="#K.3.9.2.1.3">K.3.9.2.1.3 The wmemcpy_s function</a></h5>
32755 <p><a name="K.3.9.2.1.3p14" href="#K.3.9.2.1.3p14"><small>14</small></a>
32757 #define __STDC_WANT_LIB_EXT1__ 1
32758 #include <a href="#7.29"><wchar.h></a>
32759 errno_t wmemcpy_s(wchar_t * restrict s1,
32761 const wchar_t * restrict s2,
32764 Runtime-constraints
32765 <p><a name="K.3.9.2.1.3p15" href="#K.3.9.2.1.3p15"><small>15</small></a>
32766 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32767 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
32768 objects that overlap.
32769 <p><a name="K.3.9.2.1.3p16" href="#K.3.9.2.1.3p16"><small>16</small></a>
32770 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
32771 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
32772 s1max is not greater than RSIZE_MAX.
32773 <p><b>Description</b>
32774 <p><a name="K.3.9.2.1.3p17" href="#K.3.9.2.1.3p17"><small>17</small></a>
32775 The wmemcpy_s function copies n successive wide characters from the object pointed
32776 to by s2 into the object pointed to by s1.
32778 <p><a name="K.3.9.2.1.3p18" href="#K.3.9.2.1.3p18"><small>18</small></a>
32779 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
32780 Otherwise, a nonzero value is returned.
32783 <p><small><a href="#Contents">Contents</a></small>
32784 <h5><a name="K.3.9.2.1.4" href="#K.3.9.2.1.4">K.3.9.2.1.4 The wmemmove_s function</a></h5>
32786 <p><a name="K.3.9.2.1.4p19" href="#K.3.9.2.1.4p19"><small>19</small></a>
32788 #define __STDC_WANT_LIB_EXT1__ 1
32789 #include <a href="#7.29"><wchar.h></a>
32790 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
32791 const wchar_t *s2, rsize_t n);
32793 Runtime-constraints
32794 <p><a name="K.3.9.2.1.4p20" href="#K.3.9.2.1.4p20"><small>20</small></a>
32795 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32796 RSIZE_MAX. n shall not be greater than s1max.
32797 <p><a name="K.3.9.2.1.4p21" href="#K.3.9.2.1.4p21"><small>21</small></a>
32798 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
32799 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
32800 s1max is not greater than RSIZE_MAX.
32801 <p><b>Description</b>
32802 <p><a name="K.3.9.2.1.4p22" href="#K.3.9.2.1.4p22"><small>22</small></a>
32803 The wmemmove_s function copies n successive wide characters from the object pointed
32804 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
32805 characters from the object pointed to by s2 are first copied into a temporary array of n
32806 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
32807 wide characters from the temporary array are copied into the object pointed to by s1.
32809 <p><a name="K.3.9.2.1.4p23" href="#K.3.9.2.1.4p23"><small>23</small></a>
32810 The wmemmove_s function returns zero if there was no runtime-constraint violation.
32811 Otherwise, a nonzero value is returned.
32813 <p><small><a href="#Contents">Contents</a></small>
32814 <h5><a name="K.3.9.2.2" href="#K.3.9.2.2">K.3.9.2.2 Wide string concatenation functions</a></h5>
32816 <p><small><a href="#Contents">Contents</a></small>
32817 <h5><a name="K.3.9.2.2.1" href="#K.3.9.2.2.1">K.3.9.2.2.1 The wcscat_s function</a></h5>
32819 <p><a name="K.3.9.2.2.1p1" href="#K.3.9.2.2.1p1"><small>1</small></a>
32821 #define __STDC_WANT_LIB_EXT1__ 1
32822 #include <a href="#7.29"><wchar.h></a>
32823 errno_t wcscat_s(wchar_t * restrict s1,
32825 const wchar_t * restrict s2);
32827 Runtime-constraints
32828 <p><a name="K.3.9.2.2.1p2" href="#K.3.9.2.2.1p2"><small>2</small></a>
32829 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
32831 <p><a name="K.3.9.2.2.1p3" href="#K.3.9.2.2.1p3"><small>3</small></a>
32832 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
32833 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note446"><b>446)</b></a></sup> m shall be greater than
32834 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
32836 <p><a name="K.3.9.2.2.1p4" href="#K.3.9.2.2.1p4"><small>4</small></a>
32837 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32838 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
32839 null wide character.
32840 <p><b>Description</b>
32841 <p><a name="K.3.9.2.2.1p5" href="#K.3.9.2.2.1p5"><small>5</small></a>
32842 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
32843 the terminating null wide character) to the end of the wide string pointed to by s1. The
32844 initial wide character from s2 overwrites the null wide character at the end of s1.
32845 <p><a name="K.3.9.2.2.1p6" href="#K.3.9.2.2.1p6"><small>6</small></a>
32846 All elements following the terminating null wide character (if any) written by
32847 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
32848 values when wcscat_s returns.<sup><a href="#note447"><b>447)</b></a></sup>
32850 <p><a name="K.3.9.2.2.1p7" href="#K.3.9.2.2.1p7"><small>7</small></a>
32851 The wcscat_s function returns zero<sup><a href="#note448"><b>448)</b></a></sup> if there was no runtime-constraint violation.
32852 Otherwise, a nonzero value is returned.
32854 <p><b>Footnotes</b>
32855 <p><small><a name="note446" href="#note446">446)</a> Zero means that s1 was not null terminated upon entry to wcscat_s.
32857 <p><small><a name="note447" href="#note447">447)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
32858 checking if any of those wide characters are null. Such an approach might write a wide character to
32859 every element of s1 before discovering that the first element should be set to the null wide character.
32861 <p><small><a name="note448" href="#note448">448)</a> A zero return value implies that all of the requested wide characters from the wide string pointed to by
32862 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
32865 <p><small><a href="#Contents">Contents</a></small>
32866 <h5><a name="K.3.9.2.2.2" href="#K.3.9.2.2.2">K.3.9.2.2.2 The wcsncat_s function</a></h5>
32868 <p><a name="K.3.9.2.2.2p8" href="#K.3.9.2.2.2p8"><small>8</small></a>
32870 #define __STDC_WANT_LIB_EXT1__ 1
32871 #include <a href="#7.29"><wchar.h></a>
32872 errno_t wcsncat_s(wchar_t * restrict s1,
32874 const wchar_t * restrict s2,
32877 Runtime-constraints
32878 <p><a name="K.3.9.2.2.2p9" href="#K.3.9.2.2.2p9"><small>9</small></a>
32879 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
32881 <p><a name="K.3.9.2.2.2p10" href="#K.3.9.2.2.2p10"><small>10</small></a>
32882 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32883 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note449"><b>449)</b></a></sup> If n is not less
32884 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
32885 place between objects that overlap.
32889 <p><a name="K.3.9.2.2.2p11" href="#K.3.9.2.2.2p11"><small>11</small></a>
32890 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32891 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
32892 null wide character.
32893 <p><b>Description</b>
32894 <p><a name="K.3.9.2.2.2p12" href="#K.3.9.2.2.2p12"><small>12</small></a>
32895 The wcsncat_s function appends not more than n successive wide characters (wide
32896 characters that follow a null wide character are not copied) from the array pointed to by
32897 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
32898 overwrites the null wide character at the end of s1. If no null wide character was copied
32899 from s2, then s1[s1max-m+n] is set to a null wide character.
32900 <p><a name="K.3.9.2.2.2p13" href="#K.3.9.2.2.2p13"><small>13</small></a>
32901 All elements following the terminating null wide character (if any) written by
32902 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
32903 values when wcsncat_s returns.<sup><a href="#note450"><b>450)</b></a></sup>
32905 <p><a name="K.3.9.2.2.2p14" href="#K.3.9.2.2.2p14"><small>14</small></a>
32906 The wcsncat_s function returns zero<sup><a href="#note451"><b>451)</b></a></sup> if there was no runtime-constraint violation.
32907 Otherwise, a nonzero value is returned.
32908 <p><a name="K.3.9.2.2.2p15" href="#K.3.9.2.2.2p15"><small>15</small></a>
32909 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
32910 result will not be null terminated or that wide characters will be written past the end of the destination
32913 #define __STDC_WANT_LIB_EXT1__ 1
32914 #include <a href="#7.29"><wchar.h></a>
32916 wchar_t s1[100] = L"good";
32917 wchar_t s2[6] = L"hello";
32918 wchar_t s3[6] = L"hello";
32919 wchar_t s4[7] = L"abc";
32920 wchar_t s5[1000] = L"bye";
32921 int r1, r2, r3, r4;
32922 r1 = wcsncat_s(s1, 100, s5, 1000);
32923 r2 = wcsncat_s(s2, 6, L"", 1);
32924 r3 = wcsncat_s(s3, 6, L"X", 2);
32925 r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
32927 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
32928 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
32929 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
32930 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
32937 <p><b>Footnotes</b>
32938 <p><small><a name="note449" href="#note449">449)</a> Zero means that s1 was not null terminated upon entry to wcsncat_s.
32940 <p><small><a name="note450" href="#note450">450)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
32941 checking if any of those wide characters are null. Such an approach might write a wide character to
32942 every element of s1 before discovering that the first element should be set to the null wide character.
32944 <p><small><a name="note451" href="#note451">451)</a> A zero return value implies that all of the requested wide characters from the wide string pointed to by
32945 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
32948 <p><small><a href="#Contents">Contents</a></small>
32949 <h5><a name="K.3.9.2.3" href="#K.3.9.2.3">K.3.9.2.3 Wide string search functions</a></h5>
32951 <p><small><a href="#Contents">Contents</a></small>
32952 <h5><a name="K.3.9.2.3.1" href="#K.3.9.2.3.1">K.3.9.2.3.1 The wcstok_s function</a></h5>
32954 <p><a name="K.3.9.2.3.1p1" href="#K.3.9.2.3.1p1"><small>1</small></a>
32956 #define __STDC_WANT_LIB_EXT1__ 1
32957 #include <a href="#7.29"><wchar.h></a>
32958 wchar_t *wcstok_s(wchar_t * restrict s1,
32959 rsize_t * restrict s1max,
32960 const wchar_t * restrict s2,
32961 wchar_t ** restrict ptr);
32963 Runtime-constraints
32964 <p><a name="K.3.9.2.3.1p2" href="#K.3.9.2.3.1p2"><small>2</small></a>
32965 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
32966 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
32967 The end of the token found shall occur within the first *s1max wide characters of s1 for
32968 the first call, and shall occur within the first *s1max wide characters of where searching
32969 resumes on subsequent calls.
32970 <p><a name="K.3.9.2.3.1p3" href="#K.3.9.2.3.1p3"><small>3</small></a>
32971 If there is a runtime-constraint violation, the wcstok_s function does not indirect
32972 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
32973 <p><b>Description</b>
32974 <p><a name="K.3.9.2.3.1p4" href="#K.3.9.2.3.1p4"><small>4</small></a>
32975 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
32976 into a sequence of tokens, each of which is delimited by a wide character from the wide
32977 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
32978 pointer into which the wcstok_s function stores information necessary for it to
32979 continue scanning the same wide string.
32980 <p><a name="K.3.9.2.3.1p5" href="#K.3.9.2.3.1p5"><small>5</small></a>
32981 The first call in a sequence has a non-null first argument and s1max points to an object
32982 whose value is the number of elements in the wide character array pointed to by the first
32983 argument. The first call stores an initial value in the object pointed to by ptr and
32984 updates the value pointed to by s1max to reflect the number of elements that remain in
32985 relation to ptr. Subsequent calls in the sequence have a null first argument and the
32986 objects pointed to by s1max and ptr are required to have the values stored by the
32987 previous call in the sequence, which are then updated. The separator wide string pointed
32988 to by s2 may be different from call to call.
32989 <p><a name="K.3.9.2.3.1p6" href="#K.3.9.2.3.1p6"><small>6</small></a>
32990 The first call in the sequence searches the wide string pointed to by s1 for the first wide
32991 character that is not contained in the current separator wide string pointed to by s2. If no
32992 such wide character is found, then there are no tokens in the wide string pointed to by s1
32993 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
32994 the start of the first token.
32996 <p><a name="K.3.9.2.3.1p7" href="#K.3.9.2.3.1p7"><small>7</small></a>
32997 The wcstok_s function then searches from there for the first wide character in s1 that
32998 is contained in the current separator wide string. If no such wide character is found, the
32999 current token extends to the end of the wide string pointed to by s1, and subsequent
33000 searches in the same wide string for a token return a null pointer. If such a wide character
33001 is found, it is overwritten by a null wide character, which terminates the current token.
33002 <p><a name="K.3.9.2.3.1p8" href="#K.3.9.2.3.1p8"><small>8</small></a>
33003 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
33004 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
33005 value for ptr, shall start searching just past the element overwritten by a null wide
33006 character (if any).
33008 <p><a name="K.3.9.2.3.1p9" href="#K.3.9.2.3.1p9"><small>9</small></a>
33009 The wcstok_s function returns a pointer to the first wide character of a token, or a null
33010 pointer if there is no token or there is a runtime-constraint violation.
33011 <p><a name="K.3.9.2.3.1p10" href="#K.3.9.2.3.1p10"><small>10</small></a>
33014 #define __STDC_WANT_LIB_EXT1__ 1
33015 #include <a href="#7.29"><wchar.h></a>
33016 static wchar_t str1[] = L"?a???b,,,#c";
33017 static wchar_t str2[] = L"\t \t";
33018 wchar_t *t, *ptr1, *ptr2;
33019 rsize_t max1 = wcslen(str1)+1;
33020 rsize_t max2 = wcslen(str2)+1;
33021 t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
33022 t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
33023 t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
33024 t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
33025 t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
33029 <p><small><a href="#Contents">Contents</a></small>
33030 <h5><a name="K.3.9.2.4" href="#K.3.9.2.4">K.3.9.2.4 Miscellaneous functions</a></h5>
33032 <p><small><a href="#Contents">Contents</a></small>
33033 <h5><a name="K.3.9.2.4.1" href="#K.3.9.2.4.1">K.3.9.2.4.1 The wcsnlen_s function</a></h5>
33035 <p><a name="K.3.9.2.4.1p1" href="#K.3.9.2.4.1p1"><small>1</small></a>
33037 #define __STDC_WANT_LIB_EXT1__ 1
33038 #include <a href="#7.29"><wchar.h></a>
33039 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
33041 <p><b>Description</b>
33042 <p><a name="K.3.9.2.4.1p2" href="#K.3.9.2.4.1p2"><small>2</small></a>
33043 The wcsnlen_s function computes the length of the wide string pointed to by s.
33045 <p><a name="K.3.9.2.4.1p3" href="#K.3.9.2.4.1p3"><small>3</small></a>
33046 If s is a null pointer,<sup><a href="#note452"><b>452)</b></a></sup> then the wcsnlen_s function returns zero.
33047 <p><a name="K.3.9.2.4.1p4" href="#K.3.9.2.4.1p4"><small>4</small></a>
33048 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
33049 the terminating null wide character. If there is no null wide character in the first
33050 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
33052 maxsize wide characters of s shall be accessed by wcsnlen_s.
33054 <p><b>Footnotes</b>
33055 <p><small><a name="note452" href="#note452">452)</a> Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
33056 along with the values returned for a null pointer or an unterminated wide string argument make
33057 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
33060 <p><small><a href="#Contents">Contents</a></small>
33061 <h5><a name="K.3.9.3" href="#K.3.9.3">K.3.9.3 Extended multibyte/wide character conversion utilities</a></h5>
33063 <p><small><a href="#Contents">Contents</a></small>
33064 <h5><a name="K.3.9.3.1" href="#K.3.9.3.1">K.3.9.3.1 Restartable multibyte/wide character conversion functions</a></h5>
33065 <p><a name="K.3.9.3.1p1" href="#K.3.9.3.1p1"><small>1</small></a>
33066 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
33067 conversion state) to be a null pointer.
33069 <p><small><a href="#Contents">Contents</a></small>
33070 <h5><a name="K.3.9.3.1.1" href="#K.3.9.3.1.1">K.3.9.3.1.1 The wcrtomb_s function</a></h5>
33072 <p><a name="K.3.9.3.1.1p2" href="#K.3.9.3.1.1p2"><small>2</small></a>
33074 #include <a href="#7.29"><wchar.h></a>
33075 errno_t wcrtomb_s(size_t * restrict retval,
33076 char * restrict s, rsize_t smax,
33077 wchar_t wc, mbstate_t * restrict ps);
33079 Runtime-constraints
33080 <p><a name="K.3.9.3.1.1p3" href="#K.3.9.3.1.1p3"><small>3</small></a>
33081 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
33082 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
33083 then smax shall be not be less than the number of bytes to be stored in the array pointed
33084 to by s. If s is a null pointer, then smax shall equal zero.
33085 <p><a name="K.3.9.3.1.1p4" href="#K.3.9.3.1.1p4"><small>4</small></a>
33086 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
33087 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
33088 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
33089 wcrtomb_s sets *retval to (size_t)(-1).
33090 <p><b>Description</b>
33091 <p><a name="K.3.9.3.1.1p5" href="#K.3.9.3.1.1p5"><small>5</small></a>
33092 If s is a null pointer, the wcrtomb_s function is equivalent to the call
33094 wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)
33096 where retval and buf are internal variables of the appropriate types, and the size of
33097 buf is greater than MB_CUR_MAX.
33098 <p><a name="K.3.9.3.1.1p6" href="#K.3.9.3.1.1p6"><small>6</small></a>
33099 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
33100 needed to represent the multibyte character that corresponds to the wide character given
33101 by wc (including any shift sequences), and stores the multibyte character representation
33102 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
33103 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
33104 sequence needed to restore the initial shift state; the resulting state described is the initial
33108 <p><a name="K.3.9.3.1.1p7" href="#K.3.9.3.1.1p7"><small>7</small></a>
33109 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
33110 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
33111 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
33112 *retval the number of bytes (including any shift sequences) stored in the array pointed
33115 <p><a name="K.3.9.3.1.1p8" href="#K.3.9.3.1.1p8"><small>8</small></a>
33116 The wcrtomb_s function returns zero if no runtime-constraint violation and no
33117 encoding error occurred. Otherwise, a nonzero value is returned.
33119 <p><small><a href="#Contents">Contents</a></small>
33120 <h5><a name="K.3.9.3.2" href="#K.3.9.3.2">K.3.9.3.2 Restartable multibyte/wide string conversion functions</a></h5>
33121 <p><a name="K.3.9.3.2p1" href="#K.3.9.3.2p1"><small>1</small></a>
33122 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
33123 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
33125 <p><small><a href="#Contents">Contents</a></small>
33126 <h5><a name="K.3.9.3.2.1" href="#K.3.9.3.2.1">K.3.9.3.2.1 The mbsrtowcs_s function</a></h5>
33128 <p><a name="K.3.9.3.2.1p2" href="#K.3.9.3.2.1p2"><small>2</small></a>
33130 #include <a href="#7.29"><wchar.h></a>
33131 errno_t mbsrtowcs_s(size_t * restrict retval,
33132 wchar_t * restrict dst, rsize_t dstmax,
33133 const char ** restrict src, rsize_t len,
33134 mbstate_t * restrict ps);
33136 Runtime-constraints
33137 <p><a name="K.3.9.3.2.1p3" href="#K.3.9.3.2.1p3"><small>3</small></a>
33138 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
33139 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
33140 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
33141 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
33142 character shall occur within the first dstmax multibyte characters of the array pointed to
33144 <p><a name="K.3.9.3.2.1p4" href="#K.3.9.3.2.1p4"><small>4</small></a>
33145 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
33146 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
33147 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
33148 then mbsrtowcs_s sets dst[0] to the null wide character.
33149 <p><b>Description</b>
33150 <p><a name="K.3.9.3.2.1p5" href="#K.3.9.3.2.1p5"><small>5</small></a>
33151 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
33152 the conversion state described by the object pointed to by ps, from the array indirectly
33153 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
33154 pointer, the converted characters are stored into the array pointed to by dst. Conversion
33155 continues up to and including a terminating null character, which is also stored.
33156 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
33157 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
33159 characters have been stored into the array pointed to by dst.<sup><a href="#note453"><b>453)</b></a></sup> If dst is not a null
33160 pointer and no null wide character was stored into the array pointed to by dst, then
33161 dst[len] is set to the null wide character. Each conversion takes place as if by a call
33162 to the mbrtowc function.
33163 <p><a name="K.3.9.3.2.1p6" href="#K.3.9.3.2.1p6"><small>6</small></a>
33164 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
33165 pointer (if conversion stopped due to reaching a terminating null character) or the address
33166 just past the last multibyte character converted (if any). If conversion stopped due to
33167 reaching a terminating null character and if dst is not a null pointer, the resulting state
33168 described is the initial conversion state.
33169 <p><a name="K.3.9.3.2.1p7" href="#K.3.9.3.2.1p7"><small>7</small></a>
33170 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
33171 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
33172 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
33173 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
33174 *retval the number of multibyte characters successfully converted, not including the
33175 terminating null character (if any).
33176 <p><a name="K.3.9.3.2.1p8" href="#K.3.9.3.2.1p8"><small>8</small></a>
33177 All elements following the terminating null wide character (if any) written by
33178 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
33179 unspecified values when mbsrtowcs_s returns.<sup><a href="#note454"><b>454)</b></a></sup>
33180 <p><a name="K.3.9.3.2.1p9" href="#K.3.9.3.2.1p9"><small>9</small></a>
33181 If copying takes place between objects that overlap, the objects take on unspecified
33184 <p><a name="K.3.9.3.2.1p10" href="#K.3.9.3.2.1p10"><small>10</small></a>
33185 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
33186 encoding error occurred. Otherwise, a nonzero value is returned.
33188 <p><b>Footnotes</b>
33189 <p><small><a name="note453" href="#note453">453)</a> Thus, the value of len is ignored if dst is a null pointer.
33191 <p><small><a name="note454" href="#note454">454)</a> This allows an implementation to attempt converting the multibyte string before discovering a
33192 terminating null character did not occur where required.
33195 <p><small><a href="#Contents">Contents</a></small>
33196 <h5><a name="K.3.9.3.2.2" href="#K.3.9.3.2.2">K.3.9.3.2.2 The wcsrtombs_s function</a></h5>
33198 <p><a name="K.3.9.3.2.2p11" href="#K.3.9.3.2.2p11"><small>11</small></a>
33200 #include <a href="#7.29"><wchar.h></a>
33201 errno_t wcsrtombs_s(size_t * restrict retval,
33202 char * restrict dst, rsize_t dstmax,
33203 const wchar_t ** restrict src, rsize_t len,
33204 mbstate_t * restrict ps);
33211 Runtime-constraints
33212 <p><a name="K.3.9.3.2.2p12" href="#K.3.9.3.2.2p12"><small>12</small></a>
33213 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
33214 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
33215 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
33216 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
33217 conversion shall have been stopped (see below) because a terminating null wide character
33218 was reached or because an encoding error occurred.
33219 <p><a name="K.3.9.3.2.2p13" href="#K.3.9.3.2.2p13"><small>13</small></a>
33220 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
33221 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
33222 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
33223 then wcsrtombs_s sets dst[0] to the null character.
33224 <p><b>Description</b>
33225 <p><a name="K.3.9.3.2.2p14" href="#K.3.9.3.2.2p14"><small>14</small></a>
33226 The wcsrtombs_s function converts a sequence of wide characters from the array
33227 indirectly pointed to by src into a sequence of corresponding multibyte characters that
33228 begins in the conversion state described by the object pointed to by ps. If dst is not a
33229 null pointer, the converted characters are then stored into the array pointed to by dst.
33230 Conversion continues up to and including a terminating null wide character, which is also
33231 stored. Conversion stops earlier in two cases:
33233 <li> when a wide character is reached that does not correspond to a valid multibyte
33235 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
33236 limit of n total bytes to be stored into the array pointed to by dst. If the wide
33237 character being converted is the null wide character, then n is the lesser of len or
33238 dstmax. Otherwise, n is the lesser of len or dstmax-1.
33240 If the conversion stops without converting a null wide character and dst is not a null
33241 pointer, then a null character is stored into the array pointed to by dst immediately
33242 following any multibyte characters already stored. Each conversion takes place as if by a
33243 call to the wcrtomb function.<sup><a href="#note455"><b>455)</b></a></sup>
33244 <p><a name="K.3.9.3.2.2p15" href="#K.3.9.3.2.2p15"><small>15</small></a>
33245 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
33246 pointer (if conversion stopped due to reaching a terminating null wide character) or the
33247 address just past the last wide character converted (if any). If conversion stopped due to
33248 reaching a terminating null wide character, the resulting state described is the initial
33253 <p><a name="K.3.9.3.2.2p16" href="#K.3.9.3.2.2p16"><small>16</small></a>
33254 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
33255 wide character that does not correspond to a valid multibyte character, an encoding error
33256 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
33257 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
33258 into *retval the number of bytes in the resulting multibyte character sequence, not
33259 including the terminating null character (if any).
33260 <p><a name="K.3.9.3.2.2p17" href="#K.3.9.3.2.2p17"><small>17</small></a>
33261 All elements following the terminating null character (if any) written by wcsrtombs_s
33262 in the array of dstmax elements pointed to by dst take unspecified values when
33263 wcsrtombs_s returns.<sup><a href="#note456"><b>456)</b></a></sup>
33264 <p><a name="K.3.9.3.2.2p18" href="#K.3.9.3.2.2p18"><small>18</small></a>
33265 If copying takes place between objects that overlap, the objects take on unspecified
33268 <p><a name="K.3.9.3.2.2p19" href="#K.3.9.3.2.2p19"><small>19</small></a>
33269 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
33270 encoding error occurred. Otherwise, a nonzero value is returned.
33277 <p><b>Footnotes</b>
33278 <p><small><a name="note455" href="#note455">455)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
33279 include those necessary to reach the initial shift state immediately before the null byte. However, if
33280 the conversion stops before a terminating null wide character has been reached, the result will be null
33281 terminated, but might not end in the initial shift state.
33283 <p><small><a name="note456" href="#note456">456)</a> When len is not less than dstmax, the implementation might fill the array before discovering a
33284 runtime-constraint violation.
33287 <p><small><a href="#Contents">Contents</a></small>
33288 <h2><a name="L" href="#L">Annex L</a></h2>
33294 <p><small><a href="#Contents">Contents</a></small>
33295 <h3><a name="L.1" href="#L.1">L.1 Scope</a></h3>
33296 <p><a name="L.1p1" href="#L.1p1"><small>1</small></a>
33297 This annex specifies optional behavior that can aid in the analyzability of C programs.
33298 <p><a name="L.1p2" href="#L.1p2"><small>2</small></a>
33299 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
33300 specifications in this annex.<sup><a href="#note457"><b>457)</b></a></sup>
33302 <p><b>Footnotes</b>
33303 <p><small><a name="note457" href="#note457">457)</a> Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
33307 <p><small><a href="#Contents">Contents</a></small>
33308 <h3><a name="L.2" href="#L.2">L.2 Definitions</a></h3>
33310 <p><small><a href="#Contents">Contents</a></small>
33311 <h4><a name="L.2.1" href="#L.2.1">L.2.1</a></h4>
33312 <p><a name="L.2.1p1" href="#L.2.1p1"><small>1</small></a>
33313 out-of-bounds store
33314 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
33315 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
33316 the bounds permitted by this Standard.
33318 <p><small><a href="#Contents">Contents</a></small>
33319 <h4><a name="L.2.2" href="#L.2.2">L.2.2</a></h4>
33320 <p><a name="L.2.2p1" href="#L.2.2p1"><small>1</small></a>
33321 bounded undefined behavior
33322 undefined behavior (<a href="#3.4.3">3.4.3</a>) that does not perform an out-of-bounds store.
33323 <p><a name="L.2.2p2" href="#L.2.2p2"><small>2</small></a>
33324 NOTE 1 The behavior might perform a trap.
33326 <p><a name="L.2.2p3" href="#L.2.2p3"><small>3</small></a>
33327 NOTE 2 Any values produced or stored might be indeterminate values.
33330 <p><small><a href="#Contents">Contents</a></small>
33331 <h4><a name="L.2.3" href="#L.2.3">L.2.3</a></h4>
33332 <p><a name="L.2.3p1" href="#L.2.3p1"><small>1</small></a>
33333 critical undefined behavior
33334 undefined behavior that is not bounded undefined behavior.
33335 <p><a name="L.2.3p2" href="#L.2.3p2"><small>2</small></a>
33336 NOTE The behavior might perform an out-of-bounds store or perform a trap.
33343 <p><small><a href="#Contents">Contents</a></small>
33344 <h3><a name="L.3" href="#L.3">L.3 Requirements</a></h3>
33345 <p><a name="L.3p1" href="#L.3p1"><small>1</small></a>
33346 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
33347 runtime-constraint handler. Any such semantics are implementation-defined.
33348 <p><a name="L.3p2" href="#L.3p2"><small>2</small></a>
33349 All undefined behavior shall be limited to bounded undefined behavior, except for the
33350 following which are permitted to result in critical undefined behavior:
33352 <li> An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
33353 <li> A store is performed to an object that has two incompatible declarations (<a href="#6.2.7">6.2.7</a>),
33354 <li> A pointer is used to call a function whose type is not compatible with the referenced
33355 type (<a href="#6.2.7">6.2.7</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>).
33356 <li> An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
33357 <li> The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
33358 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
33359 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
33360 integer type produces a result that points just beyond the array object and is used as
33361 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
33362 <li> An attempt is made to modify an object defined with a const-qualified type through
33363 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
33364 <li> An argument to a function or macro defined in the standard library has an invalid
33365 value or a type not expected by a function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
33366 <li> The longjmp function is called with a jmp_buf argument where the most recent
33367 invocation of the setjmp macro in the same invocation of the program with the
33368 corresponding jmp_buf argument is nonexistent, or the invocation was from another
33369 thread of execution, or the function containing the invocation has terminated
33370 execution in the interim, or the invocation was within the scope of an identifier with
33371 variably modified type and execution has left that scope in the interim (<a href="#7.13.2.1">7.13.2.1</a>).
33372 <li> The value of a pointer that refers to space deallocated by a call to the free or realloc
33373 function is used (<a href="#7.22.3">7.22.3</a>).
33374 <li> A string or wide string utility function accesses an array beyond the end of an object
33375 (<a href="#7.24.1">7.24.1</a>, <a href="#7.29.4">7.29.4</a>).
33379 <p><small><a href="#Contents">Contents</a></small>
33380 <h2><a name="Bibliography" href="#Bibliography">Bibliography</a></h2>
33382 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
33383 published in The C Programming Language by Brian W. Kernighan and Dennis
33384 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
33385 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
33386 California, USA, November 1984.
33387 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
33388 Processing Systems, Information Processing Systems Technical Report.
33389 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
33391 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
33392 Floating-Point Arithmetic.
33393 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
33394 second edition (previously designated IEC 559:1989).
33395 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
33396 symbols for use in the physical sciences and technology.
33397 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
33398 information interchange.
33399 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
33401 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
33402 <li> ISO 8601:1988, Data elements and interchange formats -- Information
33403 interchange -- Representation of dates and times.
33404 <li> ISO/IEC 9899:1990, Programming languages -- C.
33405 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
33406 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
33407 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
33408 <li> ISO/IEC 9899:1999, Programming languages -- C.
33409 <li> ISO/IEC 9899:1999/Cor.1:2001, Technical Corrigendum 1.
33410 <li> ISO/IEC 9899:1999/Cor.2:2004, Technical Corrigendum 2.
33411 <li> ISO/IEC 9899:1999/Cor.3:2007, Technical Corrigendum 3.
33413 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
33414 Interface (POSIX) -- Part 2: Shell and Utilities.
33415 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
33416 preparation of programming language standards.
33417 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
33418 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
33419 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
33420 ISO/IEC 10646-1:1993.
33421 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
33422 ISO/IEC 10646-1:1993.
33423 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
33424 Transformation Format for 16 planes of group 00 (UTF-16).
33425 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
33426 Transformation Format 8 (UTF-8).
33427 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
33428 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
33429 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
33431 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993
33433 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
33434 additional characters.
33435 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
33436 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
33437 Identifiers for characters.
33438 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
33440 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
33441 Unified Canadian Aboriginal Syllabics.
33442 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
33444 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
33445 arithmetic -- Part 1: Integer and floating point arithmetic.
33447 <li> ISO/IEC TR 19769:2004, Information technology -- Programming languages,
33448 their environments and system software interfaces -- Extensions for the
33449 programming language C to support new character data types.
33450 <li> ISO/IEC TR 24731-1:2007, Information technology -- Programming languages,
33451 their environments and system software interfaces -- Extensions to the C library
33452 -- Part 1: Bounds-checking interfaces.
33456 <p><small><a href="#Contents">Contents</a></small>
33457 <h2><a name="Index" href="#Index">Index</a></h2>
33459 [^ x ^], <a href="#3.20">3.20</a> , (comma operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a>
33460 , (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>,
33461 [_ x _], <a href="#3.21">3.21</a> <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>
33462 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (subtraction operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
33463 != (inequality operator), <a href="#6.5.9">6.5.9</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
33464 # operator, <a href="#6.10.3.2">6.10.3.2</a> -- (postfix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
33465 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -- (prefix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
33466 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33467 ## operator, <a href="#6.10.3.3">6.10.3.3</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
33468 #define preprocessing directive, <a href="#6.10.3">6.10.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
33469 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.5.2.3">6.5.2.3</a>
33470 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
33471 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> ... (ellipsis punctuator), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
33472 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> / (division operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
33473 #if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
33474 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> // (comment delimiter), <a href="#6.4.9">6.4.9</a>
33475 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33476 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
33477 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
33478 <a href="#6.10.2">6.10.2</a> ; (semicolon punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
33479 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
33480 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
33481 #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>
33482 <a href="#7.1.4">7.1.4</a> <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
33483 % (remainder operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a> << (left-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33484 %: (alternative spelling of #), <a href="#6.4.6">6.4.6</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33485 %:%: (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>
33486 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>
33487 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>,
33488 & (address operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.3">7.3</a>, <a href="#7.25">7.25</a>, <a href="#7.31.1">7.31.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
33489 & (bitwise AND operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a> <a href="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.31.2">7.31.2</a>
33490 && (logical AND operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a>, <a href="#K.3.2">K.3.2</a>
33491 &= (bitwise AND assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.6"><fenv.h></a> header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>,
33492 ' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.31.4">7.31.4</a>, <a href="#F">F</a>, <a href="#H">H</a>
33493 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a> <a href="#7.7"><float.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>,
33494 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>
33495 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.31.5">7.31.5</a>
33496 ( ) (parentheses punctuator), <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
33497 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.10"><limits.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
33498 * (asterisk punctuator), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
33499 * (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.12"><math.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.25">7.25</a>, <a href="#F">F</a>,
33500 * (multiplication operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a>
33501 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
33502 *= (multiplication assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.14"><signal.h></a> header, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
33503 + (addition operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#7.15"><stdalign.h></a> header, <a href="#4">4</a>, <a href="#7.15">7.15</a>
33504 <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a>
33505 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><stdatomic.h></a> header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>,
33506 ++ (postfix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> <a href="#7.31.8">7.31.8</a>
33507 ++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.18"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a>, <a href="#H">H</a>
33508 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33510 <a href="#7.19"><stddef.h></a> header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, \u (universal character names), <a href="#6.4.3">6.4.3</a>
33511 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a> \v (vertical-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
33512 <a href="#7.20"><stdint.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.4.1.10">7.4.1.10</a>
33513 <a href="#7.20">7.20</a>, <a href="#7.31.10">7.31.10</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> \x hexadecimal digits (hexadecimal-character
33514 <a href="#7.21"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#F">F</a>, escape sequence), <a href="#6.4.4.4">6.4.4.4</a>
33515 <a href="#K.3.5">K.3.5</a> ^ (bitwise exclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33516 <a href="#7.22"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#F">F</a>, ^= (bitwise exclusive OR assignment operator),
33517 <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a> <a href="#6.5.16.2">6.5.16.2</a>
33518 <a href="#7.23"><stdnoreturn.h></a> header, <a href="#4">4</a>, <a href="#7.23">7.23</a> __alignas_is_defined macro, <a href="#7.15">7.15</a>
33519 <a href="#7.24"><string.h></a> header, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a> __alignof_is_defined macro, <a href="#7.15">7.15</a>
33520 <a href="#7.25"><tgmath.h></a> header, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> __bool_true_false_are_defined
33521 <a href="#7.26"><threads.h></a> header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.26">7.26</a>, macro, <a href="#7.18">7.18</a>
33522 <a href="#7.31.15">7.31.15</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
33523 <a href="#7.27"><time.h></a> header, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a> __DATE__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33524 <a href="#7.28"><uchar.h></a> header, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28">7.28</a> __FILE__ macro, <a href="#6.10.8.1">6.10.8.1</a>, <a href="#7.2.1.1">7.2.1.1</a>
33525 <a href="#7.29"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29">7.29</a>, __func__ identifier, <a href="#6.4.2.2">6.4.2.2</a>, <a href="#7.2.1.1">7.2.1.1</a>
33526 <a href="#7.31.16">7.31.16</a>, <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> __LINE__ macro, <a href="#6.10.8.1">6.10.8.1</a>, <a href="#7.2.1.1">7.2.1.1</a>
33527 <a href="#7.30"><wctype.h></a> header, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a> __STDC_, <a href="#6.11.9">6.11.9</a>
33528 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.9">6.7.9</a> __STDC__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33529 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_ANALYZABLE__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#L.1">L.1</a>
33530 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_HOSTED__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33531 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#F.1">F.1</a>
33532 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
33533 >> (right-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a> <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G.1">G.1</a>
33534 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_ISO_10646__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33535 ? : (conditional operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a> __STDC_LIB_EXT1__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#K.2">K.2</a>
33536 ?? (trigraph sequences), <a href="#5.2.1.1">5.2.1.1</a> __STDC_MB_MIGHT_NEQ_WC__ macro,
33537 [ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>
33538 [ ] (brackets punctuator), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a> __STDC_NO_ATOMICS__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33539 \ (backslash character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.17.1">7.17.1</a>
33540 \ (escape character), <a href="#6.4.4.4">6.4.4.4</a> __STDC_NO_COMPLEX__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33541 \" (double-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.3.1">7.3.1</a>
33542 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> __STDC_NO_THREADS__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33543 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> <a href="#7.26.1">7.26.1</a>
33544 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> __STDC_NO_VLA__ macro, <a href="#6.10.8.3">6.10.8.3</a>
33545 \0 (null character), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> __STDC_UTF_16__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33546 padding of binary stream, <a href="#7.21.2">7.21.2</a> __STDC_UTF_32__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33547 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> __STDC_VERSION__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33548 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> __STDC_WANT_LIB_EXT1__ macro, <a href="#K.3.1.1">K.3.1.1</a>
33549 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> __TIME__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33550 \f (form-feed escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, __VA_ARGS__ identifier, <a href="#6.10.3">6.10.3</a>, <a href="#6.10.3.1">6.10.3.1</a>
33551 <a href="#7.4.1.10">7.4.1.10</a> _Alignas, <a href="#6.7.5">6.7.5</a>
33552 \n (new-line escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Alignof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a>
33553 <a href="#7.4.1.10">7.4.1.10</a> _Atomic type qualifier, <a href="#6.7.3">6.7.3</a>
33554 \octal digits (octal-character escape sequence), _Atomic type specifier, <a href="#6.7.2.4">6.7.2.4</a>
33555 <a href="#6.4.4.4">6.4.4.4</a> _Bool type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.4">F.4</a>
33556 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
33557 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> _Complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
33558 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, _Complex_I macro, <a href="#7.3.1">7.3.1</a>
33559 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a> _Exit function, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
33560 \U (universal character names), <a href="#6.4.3">6.4.3</a> _Imaginary keyword, <a href="#G.2">G.2</a>
33562 _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a> aliasing, <a href="#6.5">6.5</a>
33563 _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> alignas macro, <a href="#7.15">7.15</a>
33564 _IOFBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a> aligned_alloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.1">7.22.3.1</a>
33565 _IOLBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.6">7.21.5.6</a> alignment, <a href="#3.2">3.2</a>, <a href="#6.2.8">6.2.8</a>, <a href="#7.22.3.1">7.22.3.1</a>
33566 _IONBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a> pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a>
33567 _Noreturn, <a href="#6.7.4">6.7.4</a> structure/union member, <a href="#6.7.2.1">6.7.2.1</a>
33568 _Noreturn header, <a href="#7.23">7.23</a> alignment header, <a href="#7.15">7.15</a>
33569 _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> alignment specifier, <a href="#6.7.5">6.7.5</a>
33570 _Static_assert, <a href="#6.7.10">6.7.10</a>, <a href="#7.2">7.2</a> alignof macro, <a href="#7.15">7.15</a>
33571 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, allocated storage, order and contiguity, <a href="#7.22.3">7.22.3</a>
33572 <a href="#6.7.1">6.7.1</a>, <a href="#7.26.1">7.26.1</a> alternative spellings header, <a href="#7.9">7.9</a>
33573 { } (braces punctuator), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>, and macro, <a href="#7.9">7.9</a>
33574 <a href="#6.8.2">6.8.2</a> AND operators
33575 { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> bitwise (&), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
33576 | (bitwise inclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
33577 |= (bitwise inclusive OR assignment operator), logical (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a>
33578 <a href="#6.5.16.2">6.5.16.2</a> and_eq macro, <a href="#7.9">7.9</a>
33579 || (logical OR operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
33580 ~ (bitwise complement operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> anonymous union, <a href="#6.7.2.1">6.7.2.1</a>
33581 ANSI/IEEE 754, <a href="#F.1">F.1</a>
33582 abort function, <a href="#7.2.1.1">7.2.1.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.21.3">7.21.3</a>, ANSI/IEEE 854, <a href="#F.1">F.1</a>
33583 <a href="#7.22.4.1">7.22.4.1</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a> argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
33584 abort_handler_s function, <a href="#K.3.6.1.2">K.3.6.1.2</a> argument, <a href="#3.3">3.3</a>
33585 abs function, <a href="#7.22.6.1">7.22.6.1</a> array, <a href="#6.9.1">6.9.1</a>
33586 absolute-value functions default promotions, <a href="#6.5.2.2">6.5.2.2</a>
33587 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
33588 integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.22.6.1">7.22.6.1</a> macro, substitution, <a href="#6.10.3.1">6.10.3.1</a>
33589 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a> argument, complex, <a href="#7.3.9.1">7.3.9.1</a>
33590 abstract declarator, <a href="#6.7.7">6.7.7</a> argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
33591 abstract machine, <a href="#5.1.2.3">5.1.2.3</a> arithmetic constant expression, <a href="#6.6">6.6</a>
33592 access, <a href="#3.1">3.1</a>, <a href="#6.7.3">6.7.3</a>, <a href="#L.2.1">L.2.1</a> arithmetic conversions, usual, see usual arithmetic
33593 accuracy, see floating-point accuracy conversions
33594 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.10.1.1">F.10.1.1</a> arithmetic operators
33595 acos type-generic macro, <a href="#7.25">7.25</a> additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a>
33596 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.10.2.1">F.10.2.1</a> bitwise, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>
33597 acosh type-generic macro, <a href="#7.25">7.25</a> increment and decrement, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>
33598 acquire fence, <a href="#7.17.4">7.17.4</a> multiplicative, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
33599 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33600 active position, <a href="#5.2.2">5.2.2</a> unary, <a href="#6.5.3.3">6.5.3.3</a>
33601 actual argument, <a href="#3.3">3.3</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
33602 actual parameter (deprecated), <a href="#3.3">3.3</a> arithmetic, pointer, <a href="#6.5.6">6.5.6</a>
33603 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> array
33604 addition operator (+), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, argument, <a href="#6.9.1">6.9.1</a>
33605 <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> declarator, <a href="#6.7.6.2">6.7.6.2</a>
33606 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> initialization, <a href="#6.7.9">6.7.9</a>
33607 address constant, <a href="#6.6">6.6</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
33608 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> parameter, <a href="#6.9.1">6.9.1</a>
33609 address-free, <a href="#7.17.5">7.17.5</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
33610 aggregate initialization, <a href="#6.7.9">6.7.9</a> subscript operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
33611 aggregate types, <a href="#6.2.5">6.2.5</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
33612 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> type, <a href="#6.2.5">6.2.5</a>
33614 type conversion, <a href="#6.3.2.1">6.3.2.1</a> <a href="#7.17.7.5">7.17.7.5</a>
33615 variable length, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a> atomic_flag type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a>
33616 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> atomic_flag_clear functions, <a href="#7.17.8.2">7.17.8.2</a>
33617 as-if rule, <a href="#5.1.2.3">5.1.2.3</a> ATOMIC_FLAG_INIT macro, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a>
33618 ASCII code set, <a href="#5.2.1.1">5.2.1.1</a> atomic_flag_test_and_set functions,
33619 asctime function, <a href="#7.27.3.1">7.27.3.1</a> <a href="#7.17.8.1">7.17.8.1</a>
33620 asctime_s function, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a> atomic_init generic function, <a href="#7.17.2.2">7.17.2.2</a>
33621 asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.10.1.2">F.10.1.2</a> ATOMIC_INT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33622 asin type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
33623 asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.10.2.2">F.10.2.2</a> <a href="#7.17.5.1">7.17.5.1</a>
33624 asinh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33625 asm keyword, <a href="#J.5.10">J.5.10</a> atomic_load generic functions, <a href="#7.17.7.2">7.17.7.2</a>
33626 assert macro, <a href="#7.2.1.1">7.2.1.1</a> ATOMIC_LONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33627 assert.h header, <a href="#7.2">7.2</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33628 assignment ATOMIC_SHORT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33629 compound, <a href="#6.5.16.2">6.5.16.2</a> atomic_signal_fence function, <a href="#7.17.4.2">7.17.4.2</a>
33630 conversion, <a href="#6.5.16.1">6.5.16.1</a> atomic_store generic functions, <a href="#7.17.7.1">7.17.7.1</a>
33631 expression, <a href="#6.5.16">6.5.16</a> atomic_thread_fence function, <a href="#7.17.4.1">7.17.4.1</a>
33632 operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a> ATOMIC_VAR_INIT macro, <a href="#7.17.2.1">7.17.2.1</a>
33633 simple, <a href="#6.5.16.1">6.5.16.1</a> ATOMIC_WCHAR_T_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33634 associativity of operators, <a href="#6.5">6.5</a> atomics header, <a href="#7.17">7.17</a>, <a href="#7.31.8">7.31.8</a>
33635 asterisk punctuator (*), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
33636 at_quick_exit function, <a href="#7.22.4.2">7.22.4.2</a>, <a href="#7.22.4.3">7.22.4.3</a>, automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
33637 <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
33638 atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.10.1.3">F.10.1.3</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
33639 atan type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
33640 atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.10.1.4">F.10.1.4</a> backspace escape sequence (\b), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
33641 atan2 type-generic macro, <a href="#7.25">7.25</a> basic character set, <a href="#3.6">3.6</a>, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>
33642 atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.10.2.3">F.10.2.3</a> basic types, <a href="#6.2.5">6.2.5</a>
33643 atanh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> behavior, <a href="#3.4">3.4</a>
33644 atexit function, <a href="#7.22.4.2">7.22.4.2</a>, <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>, binary streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33645 <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>, <a href="#J.5.13">J.5.13</a> <a href="#7.21.9.4">7.21.9.4</a>
33646 atof function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.1">7.22.1.1</a> bit, <a href="#3.5">3.5</a>
33647 atoi function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> high order, <a href="#3.6">3.6</a>
33648 atol function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> low order, <a href="#3.6">3.6</a>
33649 atoll function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> bit-field, <a href="#6.7.2.1">6.7.2.1</a>
33650 atomic lock-free macros, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.5">7.17.5</a> bitand macro, <a href="#7.9">7.9</a>
33651 atomic operations, <a href="#5.1.2.4">5.1.2.4</a> bitor macro, <a href="#7.9">7.9</a>
33652 atomic types, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, bitwise operators, <a href="#6.5">6.5</a>
33653 <a href="#6.5.2.3">6.5.2.3</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, <a href="#6.7.2.4">6.7.2.4</a>, <a href="#6.10.8.3">6.10.8.3</a>, AND, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
33654 <a href="#7.17.6">7.17.6</a> AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
33655 ATOMIC_CHAR_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> complement (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a>
33656 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33657 <a href="#7.17.1">7.17.1</a> exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
33658 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
33659 <a href="#7.17.1">7.17.1</a> inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
33660 ATOMIC_CHAR_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33661 atomic_compare_exchange generic blank character, <a href="#7.4.1.3">7.4.1.3</a>
33662 functions, <a href="#7.17.7.4">7.17.7.4</a> block, <a href="#6.8">6.8</a>, <a href="#6.8.2">6.8.2</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
33663 atomic_exchange generic functions, <a href="#7.17.7.3">7.17.7.3</a> block scope, <a href="#6.2.1">6.2.1</a>
33664 atomic_fetch and modify generic functions, block structure, <a href="#6.2.1">6.2.1</a>
33666 bold type convention, <a href="#6.1">6.1</a> type-generic macro for, <a href="#7.25">7.25</a>
33667 bool macro, <a href="#7.18">7.18</a> cast expression, <a href="#6.5.4">6.5.4</a>
33668 boolean type, <a href="#6.3.1.2">6.3.1.2</a> cast operator (( )), <a href="#6.5.4">6.5.4</a>
33669 boolean type and values header, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
33670 boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a> type-generic macro for, <a href="#7.25">7.25</a>
33671 bounded undefined behavior, <a href="#L.2.2">L.2.2</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
33672 braces punctuator ({ }), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>, type-generic macro for, <a href="#7.25">7.25</a>
33673 <a href="#6.8.2">6.8.2</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.10.4.1">F.10.4.1</a>
33674 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> cbrt type-generic macro, <a href="#7.25">7.25</a>
33675 brackets punctuator ([ ]), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
33676 branch cuts, <a href="#7.3.3">7.3.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33677 break statement, <a href="#6.8.6.3">6.8.6.3</a> ccosh functions, <a href="#7.3.6.4">7.3.6.4</a>, <a href="#G.6.2.4">G.6.2.4</a>
33678 broken-down time, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.3">7.27.3</a>, type-generic macro for, <a href="#7.25">7.25</a>
33679 <a href="#7.27.3.1">7.27.3.1</a>, <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#7.27.3.5">7.27.3.5</a>, ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.10.6.1">F.10.6.1</a>
33680 <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> ceil type-generic macro, <a href="#7.25">7.25</a>
33681 bsearch function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.1">7.22.5.1</a> cerf function, <a href="#7.31.1">7.31.1</a>
33682 bsearch_s function, <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a> cerfc function, <a href="#7.31.1">7.31.1</a>
33683 btowc function, <a href="#7.29.6.1.1">7.29.6.1.1</a> cexp functions, <a href="#7.3.7.1">7.3.7.1</a>, <a href="#G.6.3.1">G.6.3.1</a>
33684 BUFSIZ macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.5">7.21.5.5</a> type-generic macro for, <a href="#7.25">7.25</a>
33685 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> cexp2 function, <a href="#7.31.1">7.31.1</a>
33686 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.31.1">7.31.1</a>
33687 byte-oriented stream, <a href="#7.21.2">7.21.2</a> char type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>,
33688 <a href="#K.3.9.1.2">K.3.9.1.2</a>
33689 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> char type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
33690 c16rtomb function, <a href="#7.28.1.2">7.28.1.2</a> <a href="#6.3.1.8">6.3.1.8</a>
33691 c32rtomb function, <a href="#7.28.1.4">7.28.1.4</a> char16_t type, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>,
33692 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> <a href="#7.28">7.28</a>
33693 type-generic macro for, <a href="#7.25">7.25</a> char32_t type, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>,
33694 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> <a href="#7.28">7.28</a>
33695 type-generic macro for, <a href="#7.25">7.25</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
33696 cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> CHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
33697 type-generic macro for, <a href="#7.25">7.25</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
33698 calendar time, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.2">7.27.2.2</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.2.4">7.27.2.4</a>, character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
33699 <a href="#7.27.3.2">7.27.3.2</a>, <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, character array initialization, <a href="#6.7.9">6.7.9</a>
33700 <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
33701 call by value, <a href="#6.5.2.2">6.5.2.2</a> wide character, <a href="#7.30.3.1">7.30.3.1</a>
33702 call_once function, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.1">7.26.2.1</a> extensible, <a href="#7.30.3.2">7.30.3.2</a>
33703 calloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.2">7.22.3.2</a> character classification functions, <a href="#7.4.1">7.4.1</a>
33704 carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a> wide character, <a href="#7.30.2.1">7.30.2.1</a>
33705 carg type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> extensible, <a href="#7.30.2.2">7.30.2.2</a>
33706 carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>, character constant, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
33707 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> character display semantics, <a href="#5.2.2">5.2.2</a>
33708 carries a dependency, <a href="#5.1.2.4">5.1.2.4</a> character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.31.2">7.31.2</a>
33709 case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> character input/output functions, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a>
33710 case mapping functions wide character, <a href="#7.29.3">7.29.3</a>
33711 character, <a href="#7.4.2">7.4.2</a> character sets, <a href="#5.2.1">5.2.1</a>
33712 wide character, <a href="#7.30.3.1">7.30.3.1</a> character string literal, see string literal
33713 extensible, <a href="#7.30.3.2">7.30.3.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
33714 casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a> character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.9">6.7.9</a>
33715 type-generic macro for, <a href="#7.25">7.25</a> characteristics of floating types header, <a href="#7.7">7.7</a>
33716 casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a> cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
33718 cimag type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> complex macro, <a href="#7.3.1">7.3.1</a>
33719 cis function, <a href="#G.6">G.6</a> complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
33720 classification functions complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>
33721 character, <a href="#7.4.1">7.4.1</a> complex type domain, <a href="#6.2.5">6.2.5</a>
33722 floating-point, <a href="#7.12.3">7.12.3</a> complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G">G</a>
33723 wide character, <a href="#7.30.2.1">7.30.2.1</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>,
33724 extensible, <a href="#7.30.2.2">7.30.2.2</a> <a href="#7.3">7.3</a>, <a href="#7.25">7.25</a>, <a href="#7.31.1">7.31.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
33725 clearerr function, <a href="#7.21.10.1">7.21.10.1</a> compliance, see conformance
33726 clgamma function, <a href="#7.31.1">7.31.1</a> components of time, <a href="#7.27.1">7.27.1</a>, <a href="#K.3.8.1">K.3.8.1</a>
33727 clock function, <a href="#7.27.2.1">7.27.2.1</a> composite type, <a href="#6.2.7">6.2.7</a>
33728 clock_t type, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.1">7.27.2.1</a> compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
33729 CLOCKS_PER_SEC macro, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.1">7.27.2.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
33730 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a> compound statement, <a href="#6.8.2">6.8.2</a>
33731 type-generic macro for, <a href="#7.25">7.25</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
33732 clog10 function, <a href="#7.31.1">7.31.1</a> concatenation functions
33733 clog1p function, <a href="#7.31.1">7.31.1</a> string, <a href="#7.24.3">7.24.3</a>, <a href="#K.3.7.2">K.3.7.2</a>
33734 clog2 function, <a href="#7.31.1">7.31.1</a> wide string, <a href="#7.29.4.3">7.29.4.3</a>, <a href="#K.3.9.2.2">K.3.9.2.2</a>
33735 CMPLX macros, <a href="#7.3.9.3">7.3.9.3</a> concatenation, preprocessing, see preprocessing
33736 cnd_broadcast function, <a href="#7.26.3.1">7.26.3.1</a>, <a href="#7.26.3.5">7.26.3.5</a>, concatenation
33737 <a href="#7.26.3.6">7.26.3.6</a> conceptual models, <a href="#5.1">5.1</a>
33738 cnd_destroy function, <a href="#7.26.3.2">7.26.3.2</a> conditional features, <a href="#4">4</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>,
33739 cnd_init function, <a href="#7.26.3.3">7.26.3.3</a> <a href="#7.1.2">7.1.2</a>, <a href="#F.1">F.1</a>, <a href="#G.1">G.1</a>, <a href="#K.2">K.2</a>, <a href="#L.1">L.1</a>
33740 cnd_signal function, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#7.26.3.5">7.26.3.5</a>, conditional inclusion, <a href="#6.10.1">6.10.1</a>
33741 <a href="#7.26.3.6">7.26.3.6</a> conditional operator (? :), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a>
33742 cnd_t type, <a href="#7.26.1">7.26.1</a> conflict, <a href="#5.1.2.4">5.1.2.4</a>
33743 cnd_timedwait function, <a href="#7.26.3.5">7.26.3.5</a> conformance, <a href="#4">4</a>
33744 cnd_wait function, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.6">7.26.3.6</a> conj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a>
33745 collating sequences, <a href="#5.2.1">5.2.1</a> conj type-generic macro, <a href="#7.25">7.25</a>
33746 colon punctuator (:), <a href="#6.7.2.1">6.7.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
33747 comma operator (,), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a> const-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.7.3">6.7.3</a>
33748 comma punctuator (,), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>, constant expression, <a href="#6.6">6.6</a>, <a href="#F.8.4">F.8.4</a>
33749 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a> constants, <a href="#6.4.4">6.4.4</a>
33750 command processor, <a href="#7.22.4.8">7.22.4.8</a> as primary expression, <a href="#6.5.1">6.5.1</a>
33751 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> character, <a href="#6.4.4.4">6.4.4.4</a>
33752 comments, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.4.9">6.4.9</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
33753 common definitions header, <a href="#7.19">7.19</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
33754 common extensions, <a href="#J.5">J.5</a> hexadecimal, <a href="#6.4.4.1">6.4.4.1</a>
33755 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> integer, <a href="#6.4.4.1">6.4.4.1</a>
33756 common real type, <a href="#6.3.1.8">6.3.1.8</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
33757 common warnings, <a href="#I">I</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
33758 comparison functions, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.1">7.22.5.1</a>, <a href="#7.22.5.2">7.22.5.2</a>, constraint_handler_t type, <a href="#K.3.6">K.3.6</a>
33759 <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a> consume operation, <a href="#5.1.2.4">5.1.2.4</a>
33760 string, <a href="#7.24.4">7.24.4</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
33761 wide string, <a href="#7.29.4.4">7.29.4.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
33762 comparison macros, <a href="#7.12.14">7.12.14</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
33763 comparison, pointer, <a href="#6.5.8">6.5.8</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.7">F.7</a>
33764 compatible type, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.6">6.7.6</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
33765 compl macro, <a href="#7.9">7.9</a> control wide character, <a href="#7.30.2">7.30.2</a>
33766 complement operator (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> conversion, <a href="#6.3">6.3</a>
33767 complete type, <a href="#6.2.5">6.2.5</a> arithmetic operands, <a href="#6.3.1">6.3.1</a>
33768 complex arithmetic header, <a href="#7.3">7.3</a>, <a href="#7.31.1">7.31.1</a> array argument, <a href="#6.9.1">6.9.1</a>
33770 array parameter, <a href="#6.9.1">6.9.1</a> correctly rounded result, <a href="#3.9">3.9</a>
33771 arrays, <a href="#6.3.2.1">6.3.2.1</a> corresponding real type, <a href="#6.2.5">6.2.5</a>
33772 boolean, <a href="#6.3.1.2">6.3.1.2</a> cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.10.1.5">F.10.1.5</a>
33773 boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a> cos type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
33774 by assignment, <a href="#6.5.16.1">6.5.16.1</a> cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.10.2.4">F.10.2.4</a>
33775 by return statement, <a href="#6.8.6.4">6.8.6.4</a> cosh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
33776 complex types, <a href="#6.3.1.6">6.3.1.6</a> cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a>
33777 explicit, <a href="#6.3">6.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33778 function, <a href="#6.3.2.1">6.3.2.1</a> cproj functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
33779 function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> cproj type-generic macro, <a href="#7.25">7.25</a>
33780 function designators, <a href="#6.3.2.1">6.3.2.1</a> creal functions, <a href="#7.3.9.6">7.3.9.6</a>, <a href="#G.6">G.6</a>
33781 function parameter, <a href="#6.9.1">6.9.1</a> creal type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
33782 imaginary, <a href="#G.4.1">G.4.1</a> critical undefined behavior, <a href="#L.2.3">L.2.3</a>
33783 imaginary and complex, <a href="#G.4.3">G.4.3</a> csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a>
33784 implicit, <a href="#6.3">6.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33785 lvalues, <a href="#6.3.2.1">6.3.2.1</a> csinh functions, <a href="#7.3.6.5">7.3.6.5</a>, <a href="#G.6.2.5">G.6.2.5</a>
33786 pointer, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33787 real and complex, <a href="#6.3.1.7">6.3.1.7</a> csqrt functions, <a href="#7.3.8.3">7.3.8.3</a>, <a href="#G.6.4.2">G.6.4.2</a>
33788 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.25">7.25</a>
33789 real floating and integer, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
33790 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33791 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctanh functions, <a href="#7.3.6.6">7.3.6.6</a>, <a href="#G.6.2.6">G.6.2.6</a>
33792 usual arithmetic, see usual arithmetic type-generic macro for, <a href="#7.25">7.25</a>
33793 conversions ctgamma function, <a href="#7.31.1">7.31.1</a>
33794 void type, <a href="#6.3.2.2">6.3.2.2</a> ctime function, <a href="#7.27.3.2">7.27.3.2</a>
33795 conversion functions ctime_s function, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>
33796 multibyte/wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.31.2">7.31.2</a>
33797 extended, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a> current object, <a href="#6.7.9">6.7.9</a>
33798 restartable, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> CX_LIMITED_RANGE pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.3.4">7.3.4</a>
33799 multibyte/wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
33800 restartable, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> data race, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.2.2">7.22.2.2</a>, <a href="#7.22.3">7.22.3</a>,
33801 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> <a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.24.5.8">7.24.5.8</a>, <a href="#7.24.6.2">7.24.6.2</a>, <a href="#7.27.3">7.27.3</a>, <a href="#7.28.1">7.28.1</a>,
33802 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1">7.29.4.1</a> <a href="#7.29.6.3">7.29.6.3</a>, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>
33803 single byte/wide character, <a href="#7.29.6.1">7.29.6.1</a> data stream, see streams
33804 time, <a href="#7.27.3">7.27.3</a>, <a href="#K.3.8.2">K.3.8.2</a> date and time header, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a>
33805 wide character, <a href="#7.29.5">7.29.5</a> Daylight Saving Time, <a href="#7.27.1">7.27.1</a>
33806 conversion specifier, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, DBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33807 <a href="#7.29.2.2">7.29.2.2</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33808 conversion state, <a href="#7.22.7">7.22.7</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.1.1">7.28.1.1</a>, DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33809 <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.6">7.29.6</a>, DBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33810 <a href="#7.29.6.2.1">7.29.6.2.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33811 <a href="#7.29.6.4">7.29.6.4</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33812 <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33813 <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33814 conversion state functions, <a href="#7.29.6.2">7.29.6.2</a> DBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33815 copying functions DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33816 string, <a href="#7.24.2">7.24.2</a>, <a href="#K.3.7.1">K.3.7.1</a> DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33817 wide string, <a href="#7.29.4.2">7.29.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a> DBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33818 copysign functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, decimal constant, <a href="#6.4.4.1">6.4.4.1</a>
33819 <a href="#F.10.8.1">F.10.8.1</a> decimal digit, <a href="#5.2.1">5.2.1</a>
33820 copysign type-generic macro, <a href="#7.25">7.25</a> decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
33822 DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.2">F.2</a>
33823 <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.5">F.5</a> double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
33824 declaration specifiers, <a href="#6.7">6.7</a> <a href="#6.3.1.8">6.3.1.8</a>
33825 declarations, <a href="#6.7">6.7</a> double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a>
33826 function, <a href="#6.7.6.3">6.7.6.3</a> double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>,
33827 pointer, <a href="#6.7.6.1">6.7.6.1</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a>
33828 structure/union, <a href="#6.7.2.1">6.7.2.1</a> double_t type, <a href="#7.12">7.12</a>
33829 typedef, <a href="#6.7.8">6.7.8</a>
33830 declarator, <a href="#6.7.6">6.7.6</a> EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error
33831 abstract, <a href="#6.7.7">6.7.7</a> effective type, <a href="#6.5">6.5</a>
33832 declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6">6.7.6</a> EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.28.1.1">7.28.1.1</a>, <a href="#7.28.1.2">7.28.1.2</a>,
33833 decrement operators, see arithmetic operators, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.3">7.29.3.3</a>,
33834 increment and decrement <a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>,
33835 default argument promotions, <a href="#6.5.2.2">6.5.2.2</a> see also encoding error
33836 default initialization, <a href="#6.7.9">6.7.9</a> element type, <a href="#6.2.5">6.2.5</a>
33837 default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> elif preprocessing directive, <a href="#6.10.1">6.10.1</a>
33838 define preprocessing directive, <a href="#6.10.3">6.10.3</a> ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
33839 defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a> else preprocessing directive, <a href="#6.10.1">6.10.1</a>
33840 definition, <a href="#6.7">6.7</a> else statement, <a href="#6.8.4.1">6.8.4.1</a>
33841 function, <a href="#6.9.1">6.9.1</a> empty statement, <a href="#6.8.3">6.8.3</a>
33842 dependency-ordered before, <a href="#5.1.2.4">5.1.2.4</a> encoding error, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
33843 derived declarator types, <a href="#6.2.5">6.2.5</a> <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.6">7.21.6.6</a>, <a href="#7.21.6.8">7.21.6.8</a>,
33844 derived types, <a href="#6.2.5">6.2.5</a> <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.28.1.1">7.28.1.1</a>,
33845 designated initializer, <a href="#6.7.9">6.7.9</a> <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>,
33846 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.2.3">7.29.2.3</a>, <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.7">7.29.2.7</a>,
33847 device input/output, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.11">7.29.2.11</a>, <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.2">7.29.3.2</a>,
33848 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.3.4">7.29.3.4</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>,
33849 diagnostics, <a href="#5.1.1.3">5.1.1.3</a> <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>,
33850 diagnostics header, <a href="#7.2">7.2</a> <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a>
33851 difftime function, <a href="#7.27.2.2">7.27.2.2</a> end-of-file, <a href="#7.29.1">7.29.1</a>
33852 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> end-of-file indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>,
33853 digraphs, <a href="#6.4.6">6.4.6</a> <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33854 direct input/output functions, <a href="#7.21.8">7.21.8</a> <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.10.1">7.21.10.1</a>, <a href="#7.21.10.2">7.21.10.2</a>, <a href="#7.29.3.1">7.29.3.1</a>,
33855 display device, <a href="#5.2.2">5.2.2</a> <a href="#7.29.3.10">7.29.3.10</a>
33856 div function, <a href="#7.22.6.2">7.22.6.2</a> end-of-file macro, see EOF macro
33857 div_t type, <a href="#7.22">7.22</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
33858 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
33859 division operator (/), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> enum type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.2">6.7.2.2</a>
33860 do statement, <a href="#6.8.5.2">6.8.5.2</a> enumerated type, <a href="#6.2.5">6.2.5</a>
33861 documentation of implementation, <a href="#4">4</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
33862 domain error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#7.12.4.4">7.12.4.4</a>, enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
33863 <a href="#7.12.5.1">7.12.5.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.7">7.12.6.7</a>, enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
33864 <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
33865 <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
33866 <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
33867 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> enumerator, <a href="#6.7.2.2">6.7.2.2</a>
33868 double _Complex type, <a href="#6.2.5">6.2.5</a> environment, <a href="#5">5</a>
33869 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, environment functions, <a href="#7.22.4">7.22.4</a>, <a href="#K.3.6.2">K.3.6.2</a>
33870 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> environment list, <a href="#7.22.4.6">7.22.4.6</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>
33871 double _Imaginary type, <a href="#G.2">G.2</a> environmental considerations, <a href="#5.2">5.2</a>
33872 double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.21.2">7.21.2</a>,
33874 <a href="#7.21.3">7.21.3</a>, <a href="#7.21.4.4">7.21.4.4</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.4.2">7.22.4.2</a>, evaluation format, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#7.12">7.12</a>
33875 <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> evaluation method, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#F.8.5">F.8.5</a>
33876 EOF macro, <a href="#7.4">7.4</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.1">7.21.5.1</a>, <a href="#7.21.5.2">7.21.5.2</a>, evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a>
33877 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.11">7.21.6.11</a>, evaluation order, see order of evaluation
33878 <a href="#7.21.6.14">7.21.6.14</a>, <a href="#7.21.7.1">7.21.7.1</a>, <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.4">7.21.7.4</a>, exceptional condition, <a href="#6.5">6.5</a>
33879 <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>, excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
33880 <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.2.4">7.29.2.4</a>, excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
33881 <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#7.29.2.12">7.29.2.12</a>, exclusive OR operators
33882 <a href="#7.29.3.4">7.29.3.4</a>, <a href="#7.29.6.1.1">7.29.6.1.1</a>, <a href="#7.29.6.1.2">7.29.6.1.2</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>, bitwise (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33883 <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>, bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
33884 <a href="#K.3.9.1.5">K.3.9.1.5</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>, executable program, <a href="#5.1.1.1">5.1.1.1</a>
33885 <a href="#K.3.9.1.14">K.3.9.1.14</a> execution character set, <a href="#5.2.1">5.2.1</a>
33886 epoch, <a href="#7.27.2.5">7.27.2.5</a> execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also
33887 equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.9">6.7.9</a> environmental limits
33888 equal-to operator, see equality operator execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a>
33889 equality expressions, <a href="#6.5.9">6.5.9</a> exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>,
33890 equality operator (==), <a href="#6.5.9">6.5.9</a> <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>, <a href="#7.26.5.5">7.26.5.5</a>
33891 ERANGE macro, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.12.1">7.12.1</a>, EXIT_FAILURE macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>
33892 <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>, see EXIT_SUCCESS macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.26.5.5">7.26.5.5</a>
33893 also range error, pole error exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.10.3.1">F.10.3.1</a>
33894 erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.10.5.1">F.10.5.1</a> exp type-generic macro, <a href="#7.25">7.25</a>
33895 erf type-generic macro, <a href="#7.25">7.25</a> exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.10.3.2">F.10.3.2</a>
33896 erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.10.5.2">F.10.5.2</a> exp2 type-generic macro, <a href="#7.25">7.25</a>
33897 erfc type-generic macro, <a href="#7.25">7.25</a> explicit conversion, <a href="#6.3">6.3</a>
33898 errno macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.3.2">7.3.2</a>, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.10.3.3">F.10.3.3</a>
33899 <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.10.4">7.21.10.4</a>, expm1 type-generic macro, <a href="#7.25">7.25</a>
33900 <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.24.6.2">7.24.6.2</a>, <a href="#7.28.1.1">7.28.1.1</a>, exponent part, <a href="#6.4.4.2">6.4.4.2</a>
33901 <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.3.1">7.29.3.1</a>, exponential functions
33902 <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>, complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
33903 <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#J.5.17">J.5.17</a>, real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
33904 <a href="#K.3.1.3">K.3.1.3</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a> expression, <a href="#6.5">6.5</a>
33905 errno.h header, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a>, <a href="#K.3.2">K.3.2</a> assignment, <a href="#6.5.16">6.5.16</a>
33906 errno_t type, <a href="#K.3.2">K.3.2</a>, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.6">K.3.6</a>, <a href="#K.3.6.1.1">K.3.6.1.1</a>, cast, <a href="#6.5.4">6.5.4</a>
33907 <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a> constant, <a href="#6.6">6.6</a>
33908 error evaluation, <a href="#5.1.2.3">5.1.2.3</a>
33909 domain, see domain error full, <a href="#6.8">6.8</a>
33910 encoding, see encoding error order of evaluation, see order of evaluation
33911 pole, see pole error parenthesized, <a href="#6.5.1">6.5.1</a>
33912 range, see range error primary, <a href="#6.5.1">6.5.1</a>
33913 error conditions, <a href="#7.12.1">7.12.1</a> unary, <a href="#6.5.3">6.5.3</a>
33914 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> expression statement, <a href="#6.8.3">6.8.3</a>
33915 error indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, extended alignment, <a href="#6.2.8">6.2.8</a>
33916 <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.7">7.21.7.7</a>, extended character set, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.1.2">5.2.1.2</a>
33917 <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.10.1">7.21.10.1</a>, <a href="#7.21.10.3">7.21.10.3</a>, extended characters, <a href="#5.2.1">5.2.1</a>
33918 <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.3">7.29.3.3</a> extended integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>,
33919 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.20">7.20</a>
33920 error-handling functions, <a href="#7.21.10">7.21.10</a>, <a href="#7.24.6.2">7.24.6.2</a>, extended multibyte and wide character utilities
33921 <a href="#K.3.7.4.2">K.3.7.4.2</a>, <a href="#K.3.7.4.3">K.3.7.4.3</a> header, <a href="#7.29">7.29</a>, <a href="#7.31.16">7.31.16</a>
33922 errors header, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a> extended multibyte/wide character conversion
33923 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> utilities, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
33924 escape sequences, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.11.4">6.11.4</a> extensible wide character case mapping functions,
33926 <a href="#7.30.3.2">7.30.3.2</a> <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.8.1">7.21.8.1</a>
33927 extensible wide character classification functions, fgetpos function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>
33928 <a href="#7.30.2.2">7.30.2.2</a> fgets function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.2">7.21.7.2</a>, <a href="#K.3.5.4.1">K.3.5.4.1</a>
33929 extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a> fgetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.29.3.1">7.29.3.1</a>,
33930 external definition, <a href="#6.9">6.9</a> <a href="#7.29.3.6">7.29.3.6</a>
33931 external identifiers, underscore, <a href="#7.1.3">7.1.3</a> fgetws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.2">7.29.3.2</a>
33932 external linkage, <a href="#6.2.2">6.2.2</a> field width, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>
33933 external name, <a href="#6.4.2.1">6.4.2.1</a> file, <a href="#7.21.3">7.21.3</a>
33934 external object definitions, <a href="#6.9.2">6.9.2</a> access functions, <a href="#7.21.5">7.21.5</a>, <a href="#K.3.5.2">K.3.5.2</a>
33935 name, <a href="#7.21.3">7.21.3</a>
33936 fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.3">F.3</a>, <a href="#F.10.4.2">F.10.4.2</a> operations, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a>
33937 fabs type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> position indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>,
33938 false macro, <a href="#7.18">7.18</a> <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
33939 fclose function, <a href="#7.21.5.1">7.21.5.1</a> <a href="#7.21.8.1">7.21.8.1</a>, <a href="#7.21.8.2">7.21.8.2</a>, <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33940 fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.10.9.1">F.10.9.1</a> <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.9.4">7.21.9.4</a>, <a href="#7.21.9.5">7.21.9.5</a>, <a href="#7.29.3.1">7.29.3.1</a>,
33941 fdim type-generic macro, <a href="#7.25">7.25</a> <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.3.10">7.29.3.10</a>
33942 FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a> positioning functions, <a href="#7.21.9">7.21.9</a>
33943 FE_DFL_ENV macro, <a href="#7.6">7.6</a> file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a>
33944 FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> FILE type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>
33945 FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a>
33946 FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> flags, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>, see also floating-point
33947 FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> status flag
33948 FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> flexible array member, <a href="#6.7.2.1">6.7.2.1</a>
33949 FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Complex type, <a href="#6.2.5">6.2.5</a>
33950 FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>,
33951 FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
33952 FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Imaginary type, <a href="#G.2">G.2</a>
33953 feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a> float type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.2">F.2</a>
33954 fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> float type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
33955 fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a> <a href="#6.3.1.8">6.3.1.8</a>
33956 fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a> float.h header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>,
33957 feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>
33958 <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> float_t type, <a href="#7.12">7.12</a>
33959 fence, <a href="#5.1.2.4">5.1.2.4</a> floating constant, <a href="#6.4.4.2">6.4.4.2</a>
33960 fences, <a href="#7.17.4">7.17.4</a> floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a>
33961 fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
33962 <a href="#7.31.4">7.31.4</a>, <a href="#F">F</a>, <a href="#H">H</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
33963 FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.8">F.8</a>, <a href="#F.9">F.9</a>, floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a>
33964 <a href="#F.10">F.10</a> floating-point accuracy, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.5">6.5</a>,
33965 fenv_t type, <a href="#7.6">7.6</a> <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression
33966 feof function, <a href="#7.21.10.2">7.21.10.2</a> floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a>
33967 feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a> floating-point classification functions, <a href="#7.12.3">7.12.3</a>
33968 ferror function, <a href="#7.21.10.3">7.21.10.3</a> floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
33969 fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a> floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.8">F.8</a>, <a href="#F.8.6">F.8.6</a>
33970 fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a> floating-point environment header, <a href="#7.6">7.6</a>, <a href="#7.31.4">7.31.4</a>
33971 fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a> floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.10">F.10</a>
33972 fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a> floating-point number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a>
33973 feupdateenv function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33974 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
33975 fflush function, <a href="#7.21.5.2">7.21.5.2</a>, <a href="#7.21.5.3">7.21.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.10.6.2">F.10.6.2</a>
33976 fgetc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, floor type-generic macro, <a href="#7.25">7.25</a>
33978 FLT_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33979 FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33980 FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33981 FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.6">6.6</a>, <a href="#7.12">7.12</a>, FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33982 <a href="#F.10.11">F.10.11</a> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
33983 FLT_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>
33984 FLT_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.1">7.21.6.1</a>,
33985 FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.6">7.21.6.6</a>,
33986 FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.1">K.3.5.3.1</a>
33987 FLT_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fprintf_s function, <a href="#K.3.5.3.1">K.3.5.3.1</a>
33988 FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.7.3">7.21.7.3</a>,
33989 FLT_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.8.2">7.21.8.2</a>
33990 FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a>
33991 FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, fputwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.29.3.3">7.29.3.3</a>,
33992 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a> <a href="#7.29.3.8">7.29.3.8</a>
33993 FLT_ROUNDS macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> fputws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.4">7.29.3.4</a>
33994 FLT_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fread function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.1">7.21.8.1</a>
33995 fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.10.10.1">F.10.10.1</a> free function, <a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a>
33996 fma type-generic macro, <a href="#7.25">7.25</a> freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>,
33997 fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.10.9.2">F.10.9.2</a> <a href="#5.1.2.1">5.1.2.1</a>
33998 fmax type-generic macro, <a href="#7.25">7.25</a> freopen function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.4">7.21.5.4</a>
33999 fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.10.9.3">F.10.9.3</a> freopen_s function, <a href="#K.3.5.2.2">K.3.5.2.2</a>
34000 fmin type-generic macro, <a href="#7.25">7.25</a> frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.10.3.4">F.10.3.4</a>
34001 fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.10.7.1">F.10.7.1</a> frexp type-generic macro, <a href="#7.25">7.25</a>
34002 fmod type-generic macro, <a href="#7.25">7.25</a> fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34003 fopen function, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.5.4">7.21.5.4</a>, <a href="#K.3.5.2.1">K.3.5.2.1</a> <a href="#7.21.6.4">7.21.6.4</a>, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>
34004 FOPEN_MAX macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.4.3">7.21.4.3</a>, fscanf_s function, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>,
34005 <a href="#K.3.5.1.1">K.3.5.1.1</a> <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>
34006 fopen_s function, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.2.1">K.3.5.2.1</a>, fseek function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
34007 <a href="#K.3.5.2.2">K.3.5.2.2</a> <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a>, <a href="#7.21.9.5">7.21.9.5</a>, <a href="#7.29.3.10">7.29.3.10</a>
34008 for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a> fsetpos function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
34009 form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.29.3.10">7.29.3.10</a>
34010 form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, ftell function, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a>
34011 <a href="#7.4.1.10">7.4.1.10</a> full declarator, <a href="#6.7.6">6.7.6</a>
34012 formal argument (deprecated), <a href="#3.16">3.16</a> full expression, <a href="#6.8">6.8</a>
34013 formal parameter, <a href="#3.16">3.16</a> fully buffered stream, <a href="#7.21.3">7.21.3</a>
34014 format conversion of integer types header, <a href="#7.8">7.8</a>, function
34015 <a href="#7.31.5">7.31.5</a> argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
34016 formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.6">7.21.6</a>, body, <a href="#6.9.1">6.9.1</a>
34017 <a href="#K.3.5.3">K.3.5.3</a> call, <a href="#6.5.2.2">6.5.2.2</a>
34018 wide character, <a href="#7.29.2">7.29.2</a>, <a href="#K.3.9.1">K.3.9.1</a> library, <a href="#7.1.4">7.1.4</a>
34019 fortran keyword, <a href="#J.5.9">J.5.9</a> declarator, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.11.6">6.11.6</a>
34020 forward reference, <a href="#3.11">3.11</a> definition, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a>
34021 FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see designator, <a href="#6.3.2.1">6.3.2.1</a>
34022 also contracted expression image, <a href="#5.2.3">5.2.3</a>
34023 FP_FAST_FMA macro, <a href="#7.12">7.12</a> inline, <a href="#6.7.4">6.7.4</a>
34024 FP_FAST_FMAF macro, <a href="#7.12">7.12</a> library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a>
34025 FP_FAST_FMAL macro, <a href="#7.12">7.12</a> name length, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
34026 FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> no-return, <a href="#6.7.4">6.7.4</a>
34027 FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> parameter, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
34028 FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> prototype, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.7">6.2.7</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>,
34030 <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.6">6.11.6</a>, <a href="#6.11.7">6.11.7</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.12">7.12</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
34031 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.6.2">6.7.6.2</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
34032 recursive call, <a href="#6.5.2.2">6.5.2.2</a> hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a>
34033 return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
34034 scope, <a href="#6.2.1">6.2.1</a> hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a>
34035 type, <a href="#6.2.5">6.2.5</a> hexadecimal-character escape sequence
34036 type conversion, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
34037 function specifiers, <a href="#6.7.4">6.7.4</a> high-order bit, <a href="#3.6">3.6</a>
34038 function type, <a href="#6.2.5">6.2.5</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
34039 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> horizontal-tab escape sequence (\r), <a href="#7.30.2.1.3">7.30.2.1.3</a>
34040 function-like macro, <a href="#6.10.3">6.10.3</a> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
34041 fundamental alignment, <a href="#6.2.8">6.2.8</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>
34042 future directions hosted execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.2">5.1.2.2</a>
34043 language, <a href="#6.11">6.11</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34044 library, <a href="#7.31">7.31</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.10">F.10</a>
34045 fwide function, <a href="#7.21.2">7.21.2</a>, <a href="#7.29.3.5">7.29.3.5</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34046 fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.10">F.10</a>
34047 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.2.3">7.29.2.3</a>, <a href="#7.29.2.5">7.29.2.5</a>, HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34048 <a href="#7.29.2.11">7.29.2.11</a>, <a href="#K.3.9.1.1">K.3.9.1.1</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.10">F.10</a>
34049 fwprintf_s function, <a href="#K.3.9.1.1">K.3.9.1.1</a> hyperbolic functions
34050 fwrite function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.2">7.21.8.2</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
34051 fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a>
34052 <a href="#7.29.2.4">7.29.2.4</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.12">7.29.2.12</a>, <a href="#7.29.3.10">7.29.3.10</a>, hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.10.4.3">F.10.4.3</a>
34053 <a href="#K.3.9.1.2">K.3.9.1.2</a> hypot type-generic macro, <a href="#7.25">7.25</a>
34054 fwscanf_s function, <a href="#K.3.9.1.2">K.3.9.1.2</a>, <a href="#K.3.9.1.5">K.3.9.1.5</a>,
34055 <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
34056 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a>
34057 gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> linkage, see linkage
34058 general utilities, <a href="#K.3.6">K.3.6</a> maximum length, <a href="#6.4.2.1">6.4.2.1</a>
34059 wide string, <a href="#7.29.4">7.29.4</a>, <a href="#K.3.9.2">K.3.9.2</a> name spaces, <a href="#6.2.3">6.2.3</a>
34060 general utilities header, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a> reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a>, <a href="#K.3.1.2">K.3.1.2</a>
34061 general wide string utilities, <a href="#7.29.4">7.29.4</a>, <a href="#K.3.9.2">K.3.9.2</a> scope, <a href="#6.2.1">6.2.1</a>
34062 generic association, <a href="#6.5.1.1">6.5.1.1</a> type, <a href="#6.2.5">6.2.5</a>
34063 generic parameters, <a href="#7.25">7.25</a> identifier list, <a href="#6.7.6">6.7.6</a>
34064 generic selection, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.1.1">6.5.1.1</a> identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a>
34065 getc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a> IEC 559, <a href="#F.1">F.1</a>
34066 getchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.6">7.21.7.6</a> IEC 60559, <a href="#2">2</a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.3.3">7.3.3</a>,
34067 getenv function, <a href="#7.22.4.6">7.22.4.6</a> <a href="#7.6">7.6</a>, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.14">7.12.14</a>, <a href="#F">F</a>, <a href="#G">G</a>,
34068 getenv_s function, <a href="#K.3.6.2.1">K.3.6.2.1</a> <a href="#H.1">H.1</a>
34069 gets function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 754, <a href="#F.1">F.1</a>
34070 gets_s function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 854, <a href="#F.1">F.1</a>
34071 getwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.6">7.29.3.6</a>, <a href="#7.29.3.7">7.29.3.7</a> IEEE floating-point arithmetic standard, see
34072 getwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.7">7.29.3.7</a> IEC 60559, ANSI/IEEE 754,
34073 gmtime function, <a href="#7.27.3.3">7.27.3.3</a> ANSI/IEEE 854
34074 gmtime_s function, <a href="#K.3.8.2.3">K.3.8.2.3</a> if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>,
34075 goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a> <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a>
34076 graphic characters, <a href="#5.2.1">5.2.1</a> if statement, <a href="#6.8.4.1">6.8.4.1</a>
34077 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
34078 greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a> ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a>
34079 ignore_handler_s function, <a href="#K.3.6.1.3">K.3.6.1.3</a>
34080 happens before, <a href="#5.1.2.4">5.1.2.4</a> ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.10.3.5">F.10.3.5</a>
34082 ilogb type-generic macro, <a href="#7.25">7.25</a> formatted, <a href="#7.29.2">7.29.2</a>, <a href="#K.3.9.1">K.3.9.1</a>
34083 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> input/output header, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#K.3.5">K.3.5</a>
34084 imaginary numbers, <a href="#G">G</a> input/output, device, <a href="#5.1.2.3">5.1.2.3</a>
34085 imaginary type domain, <a href="#G.2">G.2</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
34086 imaginary types, <a href="#G">G</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
34087 imaxabs function, <a href="#7.8.2.1">7.8.2.1</a> <a href="#6.3.1.8">6.3.1.8</a>
34088 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a>
34089 imaxdiv_t type, <a href="#7.8">7.8</a> INT_FASTN_MIN macros, <a href="#7.20.2.3">7.20.2.3</a>
34090 implementation, <a href="#3.12">3.12</a> int_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a>
34091 implementation limit, <a href="#3.13">3.13</a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.4.2.1">6.4.2.1</a>, INT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a>
34092 <a href="#6.7.6">6.7.6</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental INT_LEASTN_MIN macros, <a href="#7.20.2.2">7.20.2.2</a>
34093 limits int_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a>
34094 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
34095 implementation-defined value, <a href="#3.19.1">3.19.1</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
34096 implicit conversion, <a href="#6.3">6.3</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
34097 implicit initialization, <a href="#6.7.9">6.7.9</a> <a href="#7.22.6">7.22.6</a>
34098 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
34099 inclusive OR operators integer constant, <a href="#6.4.4.1">6.4.4.1</a>
34100 bitwise (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> integer constant expression, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.6">6.6</a>, <a href="#6.7.2.1">6.7.2.1</a>,
34101 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.7.10">6.7.10</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#6.10.1">6.10.1</a>,
34102 incomplete type, <a href="#6.2.5">6.2.5</a> <a href="#7.1.4">7.1.4</a>
34103 increment operators, see arithmetic operators, integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
34104 increment and decrement integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>,
34105 indeterminate value, <a href="#3.19.2">3.19.2</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.20.2">7.20.2</a>, <a href="#7.20.3">7.20.3</a>,
34106 indeterminately sequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>
34107 <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, see also sequenced before, integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
34108 unsequenced integer type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
34109 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
34110 inequality operator (!=), <a href="#6.5.9">6.5.9</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.20">7.20</a>
34111 infinitary, <a href="#7.12.1">7.12.1</a> extended, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#7.20">7.20</a>
34112 INFINITY macro, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> integer types header, <a href="#7.20">7.20</a>, <a href="#7.31.10">7.31.10</a>
34113 initial position, <a href="#5.2.2">5.2.2</a> inter-thread happens before, <a href="#5.1.2.4">5.1.2.4</a>
34114 initial shift state, <a href="#5.2.1.2">5.2.1.2</a> interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.3">7.21.5.3</a>
34115 initialization, <a href="#5.1.2">5.1.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.5">6.5.2.5</a>, <a href="#6.7.9">6.7.9</a>, internal linkage, <a href="#6.2.2">6.2.2</a>
34116 <a href="#F.8.5">F.8.5</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
34117 in blocks, <a href="#6.8">6.8</a> interrupt, <a href="#5.2.3">5.2.3</a>
34118 initializer, <a href="#6.7.9">6.7.9</a> INTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a>
34119 permitted form, <a href="#6.6">6.6</a> INTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
34120 string literal, <a href="#6.3.2.1">6.3.2.1</a> INTMAX_MIN macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
34121 inline, <a href="#6.7.4">6.7.4</a> intmax_t type, <a href="#7.20.1.5">7.20.1.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34122 inner scope, <a href="#6.2.1">6.2.1</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34123 input failure, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.10">7.29.2.10</a>, INTN_C macros, <a href="#7.20.4.1">7.20.4.1</a>
34124 <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, INTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a>
34125 <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>, <a href="#K.3.9.1.5">K.3.9.1.5</a>, INTN_MIN macros, <a href="#7.20.2.1">7.20.2.1</a>
34126 <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> intN_t types, <a href="#7.20.1.1">7.20.1.1</a>
34127 input/output functions INTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a>
34128 character, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a> INTPTR_MIN macro, <a href="#7.20.2.4">7.20.2.4</a>
34129 direct, <a href="#7.21.8">7.21.8</a> intptr_t type, <a href="#7.20.1.4">7.20.1.4</a>
34130 formatted, <a href="#7.21.6">7.21.6</a>, <a href="#K.3.5.3">K.3.5.3</a> inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.31.5">7.31.5</a>
34131 wide character, <a href="#7.29.2">7.29.2</a>, <a href="#K.3.9.1">K.3.9.1</a> isalnum function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>
34132 wide character, <a href="#7.29.3">7.29.3</a> isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>
34134 isblank function, <a href="#7.4.1.3">7.4.1.3</a> iswpunct function, <a href="#7.30.2.1">7.30.2.1</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>,
34135 iscntrl function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.4">7.4.1.4</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.2.1.10">7.30.2.1.10</a>,
34136 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>
34137 isdigit function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.5">7.4.1.5</a>, iswspace function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>,
34138 <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.6">7.30.2.1.6</a>,
34139 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.2.1.10">7.30.2.1.10</a>,
34140 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>
34141 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>,
34142 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.3.1.1">7.30.3.1.1</a>, <a href="#7.30.3.1.2">7.30.3.1.2</a>
34143 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> iswxdigit function, <a href="#7.30.2.1.12">7.30.2.1.12</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>
34144 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
34145 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
34146 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> iteration statements, <a href="#6.8.5">6.8.5</a>
34147 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>,
34148 <a href="#7.4.2.2">7.4.2.2</a> jmp_buf type, <a href="#7.13">7.13</a>
34149 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jump statements, <a href="#6.8.6">6.8.6</a>
34150 isnormal macro, <a href="#7.12.3.5">7.12.3.5</a>
34151 ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
34152 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> kill_dependency macro, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.17.3.1">7.17.3.1</a>
34153 ISO 8601, <a href="#2">2</a>, <a href="#7.27.3.5">7.27.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
34154 ISO/IEC 10646, <a href="#2">2</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.4.3">6.4.3</a>, <a href="#6.10.8.2">6.10.8.2</a>
34155 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.4">7.21.4.4</a>
34156 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> L_tmpnam_s macro, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34157 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
34158 ISO/IEC 9945-2, <a href="#7.11">7.11</a> labeled statement, <a href="#6.8.1">6.8.1</a>
34159 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> labs function, <a href="#7.22.6.1">7.22.6.1</a>
34160 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> language, <a href="#6">6</a>
34161 ispunct function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, future directions, <a href="#6.11">6.11</a>
34162 <a href="#7.4.1.11">7.4.1.11</a> syntax summary, <a href="#A">A</a>
34163 isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
34164 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, LC_ALL macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34165 <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.2.2">7.29.2.2</a> LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.4.3">7.24.4.3</a>,
34166 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.29.4.4.2">7.29.4.4.2</a>
34167 isupper function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.4.2.1">7.4.2.1</a>, LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.22">7.22</a>, <a href="#7.22.7">7.22.7</a>,
34168 <a href="#7.4.2.2">7.4.2.2</a> <a href="#7.22.8">7.22.8</a>, <a href="#7.29.6">7.29.6</a>, <a href="#7.30.1">7.30.1</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a>,
34169 iswalnum function, <a href="#7.30.2.1.1">7.30.2.1.1</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.3.2.1">7.30.3.2.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, <a href="#K.3.6.5">K.3.6.5</a>
34170 <a href="#7.30.2.1.10">7.30.2.1.10</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LC_MONETARY macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34171 iswalpha function, <a href="#7.30.2.1.1">7.30.2.1.1</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, LC_NUMERIC macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34172 <a href="#7.30.2.2.1">7.30.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.27.3.5">7.27.3.5</a>
34173 iswblank function, <a href="#7.30.2.1.3">7.30.2.1.3</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> lconv structure type, <a href="#7.11">7.11</a>
34174 iswcntrl function, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.4">7.30.2.1.4</a>, LDBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34175 <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34176 iswctype function, <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a> LDBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34177 iswdigit function, <a href="#7.30.2.1.1">7.30.2.1.1</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, LDBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34178 <a href="#7.30.2.1.5">7.30.2.1.5</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34179 iswgraph function, <a href="#7.30.2.1">7.30.2.1</a>, <a href="#7.30.2.1.6">7.30.2.1.6</a>, LDBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34180 <a href="#7.30.2.1.10">7.30.2.1.10</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34181 iswlower function, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, LDBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34182 <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.3.1.1">7.30.3.1.1</a>, <a href="#7.30.3.1.2">7.30.3.1.2</a> LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34183 iswprint function, <a href="#7.30.2.1.6">7.30.2.1.6</a>, <a href="#7.30.2.1.8">7.30.2.1.8</a>, LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34184 <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34186 LDBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a>
34187 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.10.3.6">F.10.3.6</a> llround type-generic macro, <a href="#7.25">7.25</a>
34188 ldexp type-generic macro, <a href="#7.25">7.25</a> local time, <a href="#7.27.1">7.27.1</a>
34189 ldiv function, <a href="#7.22.6.2">7.22.6.2</a> locale, <a href="#3.4.2">3.4.2</a>
34190 ldiv_t type, <a href="#7.22">7.22</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
34191 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
34192 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>
34193 left-shift operator (<<), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a> localization header, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
34194 length localtime function, <a href="#7.27.3.4">7.27.3.4</a>
34195 external name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> localtime_s function, <a href="#K.3.8.2.4">K.3.8.2.4</a>
34196 function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.10.3.7">F.10.3.7</a>
34197 identifier, <a href="#6.4.2.1">6.4.2.1</a> log type-generic macro, <a href="#7.25">7.25</a>
34198 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.10.3.8">F.10.3.8</a>
34199 length function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.29.4.6.1">7.29.4.6.1</a>, log10 type-generic macro, <a href="#7.25">7.25</a>
34200 <a href="#7.29.6.3.1">7.29.6.3.1</a>, <a href="#K.3.7.4.4">K.3.7.4.4</a>, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a> log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.10.3.9">F.10.3.9</a>
34201 length modifier, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, log1p type-generic macro, <a href="#7.25">7.25</a>
34202 <a href="#7.29.2.2">7.29.2.2</a> log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.10.3.10">F.10.3.10</a>
34203 less-than operator (<), <a href="#6.5.8">6.5.8</a> log2 type-generic macro, <a href="#7.25">7.25</a>
34204 less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a> logarithmic functions
34205 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
34206 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
34207 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.10.5.3">F.10.5.3</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.11">F.10.3.11</a>
34208 lgamma type-generic macro, <a href="#7.25">7.25</a> logb type-generic macro, <a href="#7.25">7.25</a>
34209 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a>, <a href="#K.3">K.3</a> logical operators
34210 future directions, <a href="#7.31">7.31</a> AND (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a>
34211 summary, <a href="#B">B</a> negation (!), <a href="#6.5.3.3">6.5.3.3</a>
34212 terms, <a href="#7.1.1">7.1.1</a> OR (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a>
34213 use of functions, <a href="#7.1.4">7.1.4</a> logical source lines, <a href="#5.1.1.2">5.1.1.2</a>
34214 lifetime, <a href="#6.2.4">6.2.4</a> long double _Complex type, <a href="#6.2.5">6.2.5</a>
34215 limits long double _Complex type conversion,
34216 environmental, see environmental limits <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
34217 implementation, see implementation limits long double _Imaginary type, <a href="#G.2">G.2</a>
34218 numerical, see numerical limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
34219 translation, see translation limits long double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>,
34220 limits.h header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.2">F.2</a>
34221 line buffered stream, <a href="#7.21.3">7.21.3</a> long double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>,
34222 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
34223 line preprocessing directive, <a href="#6.10.4">6.10.4</a> long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>,
34224 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.21.2">7.21.2</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34225 preprocessing directive, <a href="#6.10">6.10</a> long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
34226 linkage, <a href="#6.2.2">6.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.4">6.7.4</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34227 <a href="#6.11.2">6.11.2</a> long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
34228 llabs function, <a href="#7.22.6.1">7.22.6.1</a> long long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>,
34229 lldiv function, <a href="#7.22.6.2">7.22.6.2</a> <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34230 lldiv_t type, <a href="#7.22">7.22</a> long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>,
34231 LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34232 <a href="#7.29.4.1.2">7.29.4.1.2</a> long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a>
34233 LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34234 <a href="#7.29.4.1.2">7.29.4.1.2</a> LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34235 llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.5">F.10.6.5</a> longjmp function, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>, <a href="#7.22.4.4">7.22.4.4</a>,
34236 llrint type-generic macro, <a href="#7.25">7.25</a> <a href="#7.22.4.7">7.22.4.7</a>
34238 loop body, <a href="#6.8.5">6.8.5</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.6.3.1">7.29.6.3.1</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>,
34239 low-order bit, <a href="#3.6">3.6</a> <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>
34240 lowercase letter, <a href="#5.2.1">5.2.1</a> mbsinit function, <a href="#7.29.6.2.1">7.29.6.2.1</a>
34241 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.5">F.10.6.5</a> mbsrtowcs function, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
34242 lrint type-generic macro, <a href="#7.25">7.25</a> mbsrtowcs_s function, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>
34243 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a> mbstate_t type, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>,
34244 lround type-generic macro, <a href="#7.25">7.25</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28">7.28</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>,
34245 lvalue, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>, <a href="#6.5.16">6.5.16</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.6">7.29.6</a>, <a href="#7.29.6.2.1">7.29.6.2.1</a>, <a href="#7.29.6.3">7.29.6.3</a>,
34246 <a href="#6.7.2.4">6.7.2.4</a> <a href="#7.29.6.3.1">7.29.6.3.1</a>, <a href="#7.29.6.4">7.29.6.4</a>
34247 lvalue conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.16.1">6.5.16.1</a>, mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.29.6.4">7.29.6.4</a>
34248 <a href="#6.5.16.2">6.5.16.2</a> mbstowcs_s function, <a href="#K.3.6.5.1">K.3.6.5.1</a>
34249 mbtowc function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.22.7.2">7.22.7.2</a>,
34250 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.29.6.3">7.29.6.3</a>
34251 macro definition member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a>
34252 library function, <a href="#7.1.4">7.1.4</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
34253 macro invocation, <a href="#6.10.3">6.10.3</a> memchr function, <a href="#7.24.5.1">7.24.5.1</a>
34254 macro name, <a href="#6.10.3">6.10.3</a> memcmp function, <a href="#7.24.4">7.24.4</a>, <a href="#7.24.4.1">7.24.4.1</a>
34255 length, <a href="#5.2.4.1">5.2.4.1</a> memcpy function, <a href="#7.24.2.1">7.24.2.1</a>
34256 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> memcpy_s function, <a href="#K.3.7.1.1">K.3.7.1.1</a>
34257 redefinition, <a href="#6.10.3">6.10.3</a> memmove function, <a href="#7.24.2.2">7.24.2.2</a>
34258 scope, <a href="#6.10.3.5">6.10.3.5</a> memmove_s function, <a href="#K.3.7.1.2">K.3.7.1.2</a>
34259 macro parameter, <a href="#6.10.3">6.10.3</a> memory location, <a href="#3.14">3.14</a>
34260 macro preprocessor, <a href="#6.10">6.10</a> memory management functions, <a href="#7.22.3">7.22.3</a>
34261 macro replacement, <a href="#6.10.3">6.10.3</a> memory_order type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.3">7.17.3</a>
34262 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> memset function, <a href="#7.24.6.1">7.24.6.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a>
34263 main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.4">6.7.4</a>, memset_s function, <a href="#K.3.7.4.1">K.3.7.4.1</a>
34264 <a href="#7.21.3">7.21.3</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a>
34265 malloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.4">7.22.3.4</a>, <a href="#7.22.3.5">7.22.3.5</a> minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a>
34266 manipulation functions miscellaneous functions
34267 complex, <a href="#7.3.9">7.3.9</a> string, <a href="#7.24.6">7.24.6</a>, <a href="#K.3.7.4">K.3.7.4</a>
34268 real, <a href="#7.12.11">7.12.11</a>, <a href="#F.10.8">F.10.8</a> wide string, <a href="#7.29.4.6">7.29.4.6</a>, <a href="#K.3.9.2.4">K.3.9.2.4</a>
34269 matching failure, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.10">7.29.2.10</a>, mktime function, <a href="#7.27.2.3">7.27.2.3</a>
34270 <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.10.3.12">F.10.3.12</a>
34271 math.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.25">7.25</a>, <a href="#F">F</a>, modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
34272 <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a> modification order, <a href="#5.1.2.4">5.1.2.4</a>
34273 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> modulus functions, <a href="#7.12.6.12">7.12.6.12</a>
34274 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
34275 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_destroy function, <a href="#7.26.4.1">7.26.4.1</a>
34276 mathematics header, <a href="#7.12">7.12</a> mtx_init function, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.4.2">7.26.4.2</a>
34277 max_align_t type, <a href="#7.19">7.19</a> mtx_lock function, <a href="#7.26.4.3">7.26.4.3</a>
34278 maximal munch, <a href="#6.4">6.4</a> mtx_t type, <a href="#7.26.1">7.26.1</a>
34279 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> mtx_timedlock function, <a href="#7.26.4.4">7.26.4.4</a>
34280 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.22">7.22</a>, <a href="#7.22.7.2">7.22.7.2</a>, mtx_trylock function, <a href="#7.26.4.5">7.26.4.5</a>
34281 <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, mtx_unlock function, <a href="#7.26.4.3">7.26.4.3</a>, <a href="#7.26.4.4">7.26.4.4</a>,
34282 <a href="#K.3.6.4.1">K.3.6.4.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a> <a href="#7.26.4.5">7.26.4.5</a>, <a href="#7.26.4.6">7.26.4.6</a>
34283 MB_LEN_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.1.1">7.1.1</a>, <a href="#7.22">7.22</a> multibyte character, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
34284 mblen function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.29.6.3">7.29.6.3</a> multibyte conversion functions
34285 mbrlen function, <a href="#7.29.6.3.1">7.29.6.3.1</a> wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
34286 mbrtoc16 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28.1.1">7.28.1.1</a> extended, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
34287 mbrtoc32 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28.1.3">7.28.1.3</a> restartable, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
34288 mbrtowc function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
34290 restartable, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> not macro, <a href="#7.9">7.9</a>
34291 multibyte string, <a href="#7.1.1">7.1.1</a> not-equal-to operator, see inequality operator
34292 multibyte/wide character conversion functions, not_eq macro, <a href="#7.9">7.9</a>
34293 <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a> null character (\0), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>
34294 extended, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a> padding of binary stream, <a href="#7.21.2">7.21.2</a>
34295 restartable, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> NULL macro, <a href="#7.11">7.11</a>, <a href="#7.19">7.19</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.22">7.22</a>, <a href="#7.24.1">7.24.1</a>,
34296 multibyte/wide string conversion functions, <a href="#7.27.1">7.27.1</a>, <a href="#7.29.1">7.29.1</a>
34297 <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a> null pointer, <a href="#6.3.2.3">6.3.2.3</a>
34298 restartable, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> null pointer constant, <a href="#6.3.2.3">6.3.2.3</a>
34299 multidimensional array, <a href="#6.5.2.1">6.5.2.1</a> null preprocessing directive, <a href="#6.10.7">6.10.7</a>
34300 multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a> null statement, <a href="#6.8.3">6.8.3</a>
34301 multiplication operator (*), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, null wide character, <a href="#7.1.1">7.1.1</a>
34302 <a href="#G.5.1">G.5.1</a> number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a>
34303 multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a>
34304 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1">7.29.4.1</a>
34305 n-char sequence, <a href="#7.22.1.3">7.22.1.3</a> numerical limits, <a href="#5.2.4.2">5.2.4.2</a>
34306 n-wchar sequence, <a href="#7.29.4.1.1">7.29.4.1.1</a>
34307 name object, <a href="#3.15">3.15</a>
34308 external, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> object representation, <a href="#6.2.6.1">6.2.6.1</a>
34309 file, <a href="#7.21.3">7.21.3</a> object type, <a href="#6.2.5">6.2.5</a>
34310 internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> object-like macro, <a href="#6.10.3">6.10.3</a>
34311 label, <a href="#6.2.3">6.2.3</a> observable behavior, <a href="#5.1.2.3">5.1.2.3</a>
34312 structure/union member, <a href="#6.2.3">6.2.3</a> obsolescence, <a href="#6.11">6.11</a>, <a href="#7.31">7.31</a>
34313 name spaces, <a href="#6.2.3">6.2.3</a> octal constant, <a href="#6.4.4.1">6.4.4.1</a>
34314 named label, <a href="#6.8.1">6.8.1</a> octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
34315 NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a> octal-character escape sequence (\octal digits),
34316 nan functions, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#F.2.1">F.2.1</a>, <a href="#F.10.8.2">F.10.8.2</a> <a href="#6.4.4.4">6.4.4.4</a>
34317 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> offsetof macro, <a href="#7.19">7.19</a>
34318 NDEBUG macro, <a href="#7.2">7.2</a> on-off switch, <a href="#6.10.6">6.10.6</a>
34319 nearbyint functions, <a href="#7.12.9.3">7.12.9.3</a>, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, once_flag type, <a href="#7.26.1">7.26.1</a>
34320 <a href="#F.10.6.3">F.10.6.3</a> ONCE_FLAG_INIT macro, <a href="#7.26.1">7.26.1</a>
34321 nearbyint type-generic macro, <a href="#7.25">7.25</a> ones' complement, <a href="#6.2.6.2">6.2.6.2</a>
34322 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.10.6">F.10.6</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
34323 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.22.4.8">7.22.4.8</a>
34324 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> operations on files, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a>
34325 new-line character, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#6.10.4">6.10.4</a> operator, <a href="#6.4.6">6.4.6</a>
34326 new-line escape sequence (\n), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, operators, <a href="#6.5">6.5</a>
34327 <a href="#7.4.1.10">7.4.1.10</a> _Alignof, <a href="#6.5.3.4">6.5.3.4</a>
34328 nextafter functions, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>
34329 <a href="#F.10.8.3">F.10.8.3</a> assignment, <a href="#6.5.16">6.5.16</a>
34330 nextafter type-generic macro, <a href="#7.25">7.25</a> associativity, <a href="#6.5">6.5</a>
34331 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.10.8.4">F.10.8.4</a> equality, <a href="#6.5.9">6.5.9</a>
34332 nexttoward type-generic macro, <a href="#7.25">7.25</a> multiplicative, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
34333 no linkage, <a href="#6.2.2">6.2.2</a> postfix, <a href="#6.5.2">6.5.2</a>
34334 no-return function, <a href="#6.7.4">6.7.4</a> precedence, <a href="#6.5">6.5</a>
34335 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> preprocessing, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, <a href="#6.10.9">6.10.9</a>
34336 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> relational, <a href="#6.5.8">6.5.8</a>
34337 nonlocal jumps header, <a href="#7.13">7.13</a> shift, <a href="#6.5.7">6.5.7</a>
34338 noreturn macro, <a href="#7.23">7.23</a> sizeof, <a href="#6.5.3.4">6.5.3.4</a>
34339 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> unary, <a href="#6.5.3">6.5.3</a>
34340 normalized broken-down time, <a href="#K.3.8.1">K.3.8.1</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
34342 optional features, see conditional features portability, <a href="#4">4</a>, <a href="#J">J</a>
34343 or macro, <a href="#7.9">7.9</a> position indicator, file, see file position indicator
34344 OR operators positive difference, <a href="#7.12.12.1">7.12.12.1</a>
34345 bitwise exclusive (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a> positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a>
34346 bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> postfix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
34347 bitwise inclusive (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> postfix expressions, <a href="#6.5.2">6.5.2</a>
34348 bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> postfix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
34349 logical (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.10.4.4">F.10.4.4</a>
34350 or_eq macro, <a href="#7.9">7.9</a> pow type-generic macro, <a href="#7.25">7.25</a>
34351 order of allocated storage, <a href="#7.22.3">7.22.3</a> power functions
34352 order of evaluation, <a href="#6.5">6.5</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
34353 see also sequence points real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a>
34354 ordinary identifier name space, <a href="#6.2.3">6.2.3</a> pp-number, <a href="#6.4.8">6.4.8</a>
34355 orientation of stream, <a href="#7.21.2">7.21.2</a>, <a href="#7.29.3.5">7.29.3.5</a> pragma operator, <a href="#6.10.9">6.10.9</a>
34356 out-of-bounds store, <a href="#L.2.1">L.2.1</a> pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a>
34357 outer scope, <a href="#6.2.1">6.2.1</a> precedence of operators, <a href="#6.5">6.5</a>
34358 over-aligned, <a href="#6.2.8">6.2.8</a> precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a>
34359 precision, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>
34360 padding excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
34361 binary stream, <a href="#7.21.2">7.21.2</a> predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
34362 bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a> prefix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
34363 structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a> prefix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
34364 parameter, <a href="#3.16">3.16</a> preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a>
34365 array, <a href="#6.9.1">6.9.1</a> preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a>
34366 ellipsis, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a> preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a>
34367 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a> preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a>
34368 macro, <a href="#6.10.3">6.10.3</a> preprocessing operators
34369 main function, <a href="#5.1.2.2.1">5.1.2.2.1</a> #, <a href="#6.10.3.2">6.10.3.2</a>
34370 program, <a href="#5.1.2.2.1">5.1.2.2.1</a> ##, <a href="#6.10.3.3">6.10.3.3</a>
34371 parameter type list, <a href="#6.7.6.3">6.7.6.3</a> _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
34372 parentheses punctuator (( )), <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> defined, <a href="#6.10.1">6.10.1</a>
34373 parenthesized expression, <a href="#6.5.1">6.5.1</a> preprocessing tokens, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>
34374 parse state, <a href="#7.21.2">7.21.2</a> preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a>
34375 perform a trap, <a href="#3.19.5">3.19.5</a> preprocessor, <a href="#6.10">6.10</a>
34376 permitted form of initializer, <a href="#6.6">6.6</a> PRIcFASTN macros, <a href="#7.8.1">7.8.1</a>
34377 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
34378 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> PRIcMAX macros, <a href="#7.8.1">7.8.1</a>
34379 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> PRIcN macros, <a href="#7.8.1">7.8.1</a>
34380 placemarker, <a href="#6.10.3.3">6.10.3.3</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
34381 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> primary expression, <a href="#6.5.1">6.5.1</a>
34382 pointer arithmetic, <a href="#6.5.6">6.5.6</a> printf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.10">7.21.6.10</a>,
34383 pointer comparison, <a href="#6.5.8">6.5.8</a> <a href="#K.3.5.3.3">K.3.5.3.3</a>
34384 pointer declarator, <a href="#6.7.6.1">6.7.6.1</a> printf_s function, <a href="#K.3.5.3.3">K.3.5.3.3</a>
34385 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> printing character, <a href="#5.2.2">5.2.2</a>, <a href="#7.4">7.4</a>, <a href="#7.4.1.8">7.4.1.8</a>
34386 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> printing wide character, <a href="#7.30.2">7.30.2</a>
34387 pointer type, <a href="#6.2.5">6.2.5</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
34388 pointer type conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> program execution, <a href="#5.1.2.2.2">5.1.2.2.2</a>, <a href="#5.1.2.3">5.1.2.3</a>
34389 pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
34390 pole error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, program image, <a href="#5.1.1.2">5.1.1.2</a>
34391 <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#7.12.7.4">7.12.7.4</a>, program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
34392 <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
34394 program startup, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.1">5.1.2.2.1</a> recursion, <a href="#6.5.2.2">6.5.2.2</a>
34395 program structure, <a href="#5.1.1.1">5.1.1.1</a> recursive function call, <a href="#6.5.2.2">6.5.2.2</a>
34396 program termination, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, redefinition of macro, <a href="#6.10.3">6.10.3</a>
34397 <a href="#5.1.2.3">5.1.2.3</a> reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>
34398 program, conforming, <a href="#4">4</a> library functions, <a href="#7.1.4">7.1.4</a>
34399 program, strictly conforming, <a href="#4">4</a> referenced type, <a href="#6.2.5">6.2.5</a>
34400 promotions register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
34401 default argument, <a href="#6.5.2.2">6.5.2.2</a> relational expressions, <a href="#6.5.8">6.5.8</a>
34402 integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a> relaxed atomic operations, <a href="#5.1.2.4">5.1.2.4</a>
34403 prototype, see function prototype release fence, <a href="#7.17.4">7.17.4</a>
34404 pseudo-random sequence functions, <a href="#7.22.2">7.22.2</a> release operation, <a href="#5.1.2.4">5.1.2.4</a>
34405 PTRDIFF_MAX macro, <a href="#7.20.3">7.20.3</a> release sequence, <a href="#5.1.2.4">5.1.2.4</a>
34406 PTRDIFF_MIN macro, <a href="#7.20.3">7.20.3</a> reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a>
34407 ptrdiff_t type, <a href="#7.17.1">7.17.1</a>, <a href="#7.19">7.19</a>, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a>
34408 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a> remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.10.7">F.10.7</a>
34409 punctuators, <a href="#6.4.6">6.4.6</a> remainder functions, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>,
34410 putc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.7.8">7.21.7.8</a> <a href="#F.10.7.2">F.10.7.2</a>
34411 putchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.8">7.21.7.8</a> remainder operator (%), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>
34412 puts function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.9">7.21.7.9</a> remainder type-generic macro, <a href="#7.25">7.25</a>
34413 putwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.8">7.29.3.8</a>, <a href="#7.29.3.9">7.29.3.9</a> remove function, <a href="#7.21.4.1">7.21.4.1</a>, <a href="#7.21.4.4">7.21.4.4</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34414 putwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.9">7.29.3.9</a> remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.10.7.3">F.10.7.3</a>
34415 remquo type-generic macro, <a href="#7.25">7.25</a>
34416 qsort function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.2">7.22.5.2</a> rename function, <a href="#7.21.4.2">7.21.4.2</a>
34417 qsort_s function, <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a> representations of types, <a href="#6.2.6">6.2.6</a>
34418 qualified types, <a href="#6.2.5">6.2.5</a> pointer, <a href="#6.2.5">6.2.5</a>
34419 qualified version of type, <a href="#6.2.5">6.2.5</a> rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a>
34420 question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a> reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a>, <a href="#K.3.1.2">K.3.1.2</a>
34421 quick_exit function, <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>, restartable multibyte/wide character conversion
34422 <a href="#7.22.4.7">7.22.4.7</a> functions, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
34423 quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a> restartable multibyte/wide string conversion
34424 functions, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
34425 raise function, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>, <a href="#7.22.4.1">7.22.4.1</a> restore calling environment function, <a href="#7.13.2">7.13.2</a>
34426 rand function, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.2.2">7.22.2.2</a> restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a>
34427 RAND_MAX macro, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a> restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
34428 range return statement, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
34429 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> rewind function, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.5">7.21.9.5</a>,
34430 range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.29.3.10">7.29.3.10</a>
34431 <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.6">7.12.6.6</a>, right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a>
34432 <a href="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, right-shift operator (>>), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
34433 <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.4">F.10.6.4</a>
34434 <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#7.12.13.1">7.12.13.1</a> rint type-generic macro, <a href="#7.25">7.25</a>
34435 rank, see integer conversion rank round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.10.6.6">F.10.6.6</a>
34436 read-modify-write operations, <a href="#5.1.2.4">5.1.2.4</a> round type-generic macro, <a href="#7.25">7.25</a>
34437 real floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34438 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> RSIZE_MAX macro, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>,
34439 real floating types, <a href="#6.2.5">6.2.5</a> <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>,
34440 real type domain, <a href="#6.2.5">6.2.5</a> <a href="#K.3.5.4.1">K.3.5.4.1</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a>,
34441 real types, <a href="#6.2.5">6.2.5</a> <a href="#K.3.6.4.1">K.3.6.4.1</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.7.1.1">K.3.7.1.1</a>,
34442 real-floating, <a href="#7.12.3">7.12.3</a> <a href="#K.3.7.1.2">K.3.7.1.2</a>, <a href="#K.3.7.1.3">K.3.7.1.3</a>, <a href="#K.3.7.1.4">K.3.7.1.4</a>, <a href="#K.3.7.2.1">K.3.7.2.1</a>,
34443 realloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.5">7.22.3.5</a> <a href="#K.3.7.2.2">K.3.7.2.2</a>, <a href="#K.3.7.3.1">K.3.7.3.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a>,
34444 recommended practice, <a href="#3.17">3.17</a> <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a>,
34446 <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a>, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a>, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a>, <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6.1.1">K.3.6.1.1</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a>, <a href="#K.3.6.1.3">K.3.6.1.3</a>
34447 <a href="#K.3.9.2.1.3">K.3.9.2.1.3</a>, <a href="#K.3.9.2.1.4">K.3.9.2.1.4</a>, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>, setbuf function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.1">7.21.5.1</a>, <a href="#7.21.5.5">7.21.5.5</a>
34448 <a href="#K.3.9.2.2.2">K.3.9.2.2.2</a>, <a href="#K.3.9.2.3.1">K.3.9.2.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
34449 <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> setjmp.h header, <a href="#7.13">7.13</a>
34450 rsize_t type, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>, setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34451 <a href="#K.3.6">K.3.6</a>, <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a> setvbuf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.1">7.21.5.1</a>,
34452 runtime-constraint, <a href="#3.18">3.18</a> <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a>
34453 Runtime-constraint handling functions, <a href="#K.3.6.1">K.3.6.1</a> shall, <a href="#4">4</a>
34454 rvalue, <a href="#6.3.2.1">6.3.2.1</a> shift expressions, <a href="#6.5.7">6.5.7</a>
34455 shift sequence, <a href="#7.1.1">7.1.1</a>
34456 same scope, <a href="#6.2.1">6.2.1</a> shift states, <a href="#5.2.1.2">5.2.1.2</a>
34457 save calling environment function, <a href="#7.13.1">7.13.1</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
34458 scalar types, <a href="#6.2.5">6.2.5</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>,
34459 scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.13">F.10.3.13</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34460 scalbln type-generic macro, <a href="#7.25">7.25</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
34461 scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.13">F.10.3.13</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34462 scalbn type-generic macro, <a href="#7.25">7.25</a> SHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34463 scanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.4">7.21.6.4</a>, <a href="#7.21.6.11">7.21.6.11</a> SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34464 scanf_s function, <a href="#K.3.5.3.4">K.3.5.3.4</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a> side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.5">6.5</a>, <a href="#6.5.2.4">6.5.2.4</a>,
34465 scanlist, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a> <a href="#6.5.16">6.5.16</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.8.3">6.8.3</a>, <a href="#7.6">7.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.21.7.5">7.21.7.5</a>,
34466 scanset, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a> <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.29.3.6">7.29.3.6</a>, <a href="#7.29.3.8">7.29.3.8</a>, <a href="#F.8.1">F.8.1</a>, <a href="#F.9.1">F.9.1</a>,
34467 SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> <a href="#F.9.3">F.9.3</a>
34468 SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> SIG_ATOMIC_MAX macro, <a href="#7.20.3">7.20.3</a>
34469 SCNcFASTN macros, <a href="#7.8.1">7.8.1</a> SIG_ATOMIC_MIN macro, <a href="#7.20.3">7.20.3</a>
34470 SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a> sig_atomic_t type, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>,
34471 SCNcMAX macros, <a href="#7.8.1">7.8.1</a> <a href="#7.20.3">7.20.3</a>
34472 SCNcN macros, <a href="#7.8.1">7.8.1</a> SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34473 SCNcPTR macros, <a href="#7.8.1">7.8.1</a> SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34474 scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a> SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34475 search functions SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.22.4.1">7.22.4.1</a>
34476 string, <a href="#7.24.5">7.24.5</a>, <a href="#K.3.7.3">K.3.7.3</a> SIGFPE macro, <a href="#7.12.1">7.12.1</a>, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.2">J.2</a>, <a href="#J.5.17">J.5.17</a>
34477 utility, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a> SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.2">J.2</a>
34478 wide string, <a href="#7.29.4.5">7.29.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a> SIGINT macro, <a href="#7.14">7.14</a>
34479 SEEK_CUR macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a>
34480 SEEK_END macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> sign bit, <a href="#6.2.6.2">6.2.6.2</a>
34481 SEEK_SET macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
34482 selection statements, <a href="#6.8.4">6.8.4</a> signal handler, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>
34483 self-referential structure, <a href="#6.7.2.3">6.7.2.3</a> signal handling functions, <a href="#7.14.1">7.14.1</a>
34484 semicolon punctuator (;), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>, signal handling header, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
34485 <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a> signal.h header, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
34486 separate compilation, <a href="#5.1.1.1">5.1.1.1</a> signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a>
34487 separate translation, <a href="#5.1.1.1">5.1.1.1</a> signals, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1">7.14.1</a>
34488 sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.13">6.5.13</a>, <a href="#6.5.14">6.5.14</a>, signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a>
34489 <a href="#6.5.15">6.5.15</a>, <a href="#6.5.17">6.5.17</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.6">6.7.6</a>, <a href="#6.8">6.8</a>, signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34490 <a href="#7.1.4">7.1.4</a>, <a href="#7.21.6">7.21.6</a>, <a href="#7.22.5">7.22.5</a>, <a href="#7.29.2">7.29.2</a>, <a href="#C">C</a>, <a href="#K.3.6.3">K.3.6.3</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>
34491 sequenced after, see sequenced before signed character, <a href="#6.3.1.1">6.3.1.1</a>
34492 sequenced before, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.2.4">6.5.2.4</a>, signed integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>
34493 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
34494 unsequenced <a href="#6.3.1.8">6.3.1.8</a>
34495 sequencing of statements, <a href="#6.8">6.8</a> signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>
34496 set_constraint_handler_s function, significand part, <a href="#6.4.4.2">6.4.4.2</a>
34498 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.2">J.2</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.31.5">7.31.5</a>
34499 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
34500 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
34501 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.10.1.6">F.10.1.6</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
34502 sin type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#7.12"><math.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.25">7.25</a>, <a href="#F">F</a>, <a href="#F.10">F.10</a>,
34503 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#J.5.17">J.5.17</a>
34504 single-byte/wide character conversion functions, <a href="#7.13"><setjmp.h></a>, <a href="#7.13">7.13</a>
34505 <a href="#7.29.6.1">7.29.6.1</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
34506 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.15"><stdalign.h></a>, <a href="#4">4</a>, <a href="#7.15">7.15</a>
34507 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.16"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a>
34508 singularity, <a href="#7.12.1">7.12.1</a> <a href="#7.17"><stdatomic.h></a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>,
34509 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.10.2.5">F.10.2.5</a> <a href="#7.31.8">7.31.8</a>
34510 sinh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#7.18"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a>, <a href="#H">H</a>
34511 SIZE_MAX macro, <a href="#7.20.3">7.20.3</a> <a href="#7.19"><stddef.h></a>, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
34512 size_t type, <a href="#6.2.8">6.2.8</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.19">7.19</a>, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.1">7.21.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a>
34513 <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22">7.22</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.28">7.28</a>, <a href="#7.20"><stdint.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.20">7.20</a>,
34514 <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#7.31.10">7.31.10</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>
34515 <a href="#K.3.5">K.3.5</a>, <a href="#K.3.6">K.3.6</a>, <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a> <a href="#7.21"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#F">F</a>, <a href="#K.3.5">K.3.5</a>
34516 sizeof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> <a href="#7.22"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#F">F</a>,
34517 sizes of integer types header, <a href="#7.10">7.10</a> <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a>
34518 snprintf function, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.23"><stdnoreturn.h></a>, <a href="#4">4</a>, <a href="#7.23">7.23</a>
34519 <a href="#K.3.5.3.5">K.3.5.3.5</a> <a href="#7.24"><string.h></a>, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a>
34520 snprintf_s function, <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a> <a href="#7.25"><tgmath.h></a>, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
34521 snwprintf_s function, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a> <a href="#7.26"><threads.h></a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.26">7.26</a>, <a href="#7.31.15">7.31.15</a>
34522 sorting utility functions, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a> <a href="#7.27"><time.h></a>, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a>
34523 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> <a href="#7.28"><uchar.h></a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28">7.28</a>
34524 source file, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.29"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29">7.29</a>, <a href="#7.31.16">7.31.16</a>,
34525 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a> <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a>
34526 source file inclusion, <a href="#6.10.2">6.10.2</a> <a href="#7.30"><wctype.h></a>, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a>
34527 source lines, <a href="#5.1.1.2">5.1.1.2</a> standard input stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>
34528 source text, <a href="#5.1.1.2">5.1.1.2</a> standard integer types, <a href="#6.2.5">6.2.5</a>
34529 space character (' '), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, standard output stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>
34530 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a> standard signed integer types, <a href="#6.2.5">6.2.5</a>
34531 sprintf function, <a href="#7.21.6.6">7.21.6.6</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
34532 sprintf_s function, <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a> statements, <a href="#6.8">6.8</a>
34533 sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.4.5">F.10.4.5</a> break, <a href="#6.8.6.3">6.8.6.3</a>
34534 sqrt type-generic macro, <a href="#7.25">7.25</a> compound, <a href="#6.8.2">6.8.2</a>
34535 srand function, <a href="#7.22.2.2">7.22.2.2</a> continue, <a href="#6.8.6.2">6.8.6.2</a>
34536 sscanf function, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.14">7.21.6.14</a> do, <a href="#6.8.5.2">6.8.5.2</a>
34537 sscanf_s function, <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> else, <a href="#6.8.4.1">6.8.4.1</a>
34538 standard error stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.10.4">7.21.10.4</a> expression, <a href="#6.8.3">6.8.3</a>
34539 standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a> for, <a href="#6.8.5.3">6.8.5.3</a>
34540 <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a> goto, <a href="#6.8.6.1">6.8.6.1</a>
34541 <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.3">7.3</a>, if, <a href="#6.8.4.1">6.8.4.1</a>
34542 <a href="#7.25">7.25</a>, <a href="#7.31.1">7.31.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a> iteration, <a href="#6.8.5">6.8.5</a>
34543 <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.31.2">7.31.2</a> jump, <a href="#6.8.6">6.8.6</a>
34544 <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a>, <a href="#K.3.2">K.3.2</a> labeled, <a href="#6.8.1">6.8.1</a>
34545 <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, null, <a href="#6.8.3">6.8.3</a>
34546 <a href="#7.31.4">7.31.4</a>, <a href="#F">F</a>, <a href="#H">H</a> return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
34547 <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>, selection, <a href="#6.8.4">6.8.4</a>
34548 <a href="#7.29.4.1.1">7.29.4.1.1</a> sequencing, <a href="#6.8">6.8</a>
34550 switch, <a href="#6.8.4.2">6.8.4.2</a> strerrorlen_s function, <a href="#K.3.7.4.3">K.3.7.4.3</a>
34551 while, <a href="#6.8.5.1">6.8.5.1</a> strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.27.3">7.27.3</a>, <a href="#7.27.3.5">7.27.3.5</a>,
34552 static assertions, <a href="#6.7.10">6.7.10</a> <a href="#7.29.5.1">7.29.5.1</a>, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>
34553 static storage duration, <a href="#6.2.4">6.2.4</a> stricter, <a href="#6.2.8">6.2.8</a>
34554 static storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.7.1">6.7.1</a> strictly conforming program, <a href="#4">4</a>
34555 static, in array declarators, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.6.3">6.7.6.3</a> string, <a href="#7.1.1">7.1.1</a>
34556 static_assert declaration, <a href="#6.7.10">6.7.10</a> comparison functions, <a href="#7.24.4">7.24.4</a>
34557 static_assert macro, <a href="#7.2">7.2</a> concatenation functions, <a href="#7.24.3">7.24.3</a>, <a href="#K.3.7.2">K.3.7.2</a>
34558 stdalign.h header, <a href="#4">4</a>, <a href="#7.15">7.15</a> conversion functions, <a href="#7.11.1.1">7.11.1.1</a>
34559 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a> copying functions, <a href="#7.24.2">7.24.2</a>, <a href="#K.3.7.1">K.3.7.1</a>
34560 stdatomic.h header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>, library function conventions, <a href="#7.24.1">7.24.1</a>
34561 <a href="#7.31.8">7.31.8</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.9">6.7.9</a>
34562 stdbool.h header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a>, <a href="#H">H</a> miscellaneous functions, <a href="#7.24.6">7.24.6</a>, <a href="#K.3.7.4">K.3.7.4</a>
34563 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a>
34564 stddef.h header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, search functions, <a href="#7.24.5">7.24.5</a>, <a href="#K.3.7.3">K.3.7.3</a>
34565 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a> string handling header, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a>
34566 stderr macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a> string.h header, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a>
34567 stdin macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.4">7.21.6.4</a>, stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
34568 <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.29.2.12">7.29.2.12</a>, <a href="#7.29.3.7">7.29.3.7</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>, strlen function, <a href="#7.24.6.3">7.24.6.3</a>
34569 <a href="#K.3.5.4.1">K.3.5.4.1</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> strncat function, <a href="#7.24.3.2">7.24.3.2</a>
34570 stdint.h header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.20">7.20</a>, strncat_s function, <a href="#K.3.7.2.2">K.3.7.2.2</a>
34571 <a href="#7.31.10">7.31.10</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> strncmp function, <a href="#7.24.4">7.24.4</a>, <a href="#7.24.4.4">7.24.4.4</a>
34572 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#F">F</a>, strncpy function, <a href="#7.24.2.4">7.24.2.4</a>
34573 <a href="#K.3.5">K.3.5</a> strncpy_s function, <a href="#K.3.7.1.4">K.3.7.1.4</a>
34574 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#F">F</a>, strnlen_s function, <a href="#K.3.7.4.4">K.3.7.4.4</a>
34575 <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a> stronger, <a href="#6.2.8">6.2.8</a>
34576 stdnoreturn.h header, <a href="#4">4</a>, <a href="#7.23">7.23</a> strpbrk function, <a href="#7.24.5.4">7.24.5.4</a>
34577 stdout macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.3">7.21.6.3</a>, strrchr function, <a href="#7.24.5.5">7.24.5.5</a>
34578 <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>, <a href="#7.29.2.11">7.29.2.11</a>, <a href="#7.29.3.9">7.29.3.9</a> strspn function, <a href="#7.24.5.6">7.24.5.6</a>
34579 storage duration, <a href="#6.2.4">6.2.4</a> strstr function, <a href="#7.24.5.7">7.24.5.7</a>
34580 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34581 storage unit (bit-field), <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a> <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.3">F.3</a>
34582 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.3">F.3</a>
34583 strcat function, <a href="#7.24.3.1">7.24.3.1</a> strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
34584 strcat_s function, <a href="#K.3.7.2.1">K.3.7.2.1</a> strtok function, <a href="#7.24.5.8">7.24.5.8</a>
34585 strchr function, <a href="#7.24.5.2">7.24.5.2</a> strtok_s function, <a href="#K.3.7.3.1">K.3.7.3.1</a>
34586 strcmp function, <a href="#7.24.4">7.24.4</a>, <a href="#7.24.4.2">7.24.4.2</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.2">7.22.1.2</a>,
34587 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.4.3">7.24.4.3</a>, <a href="#7.24.4.5">7.24.4.5</a> <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.2.2">7.29.2.2</a>
34588 strcpy function, <a href="#7.24.2.3">7.24.2.3</a> strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.3">F.3</a>
34589 strcpy_s function, <a href="#K.3.7.1.3">K.3.7.1.3</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a>
34590 strcspn function, <a href="#7.24.5.3">7.24.5.3</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.2">7.22.1.2</a>,
34591 streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.22.4.4">7.22.4.4</a> <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.2.2">7.29.2.2</a>
34592 fully buffered, <a href="#7.21.3">7.21.3</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a>
34593 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
34594 orientation, <a href="#7.21.2">7.21.2</a> struct hack, see flexible array member
34595 standard error, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct lconv, <a href="#7.11">7.11</a>
34596 standard input, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct timespec, <a href="#7.27.1">7.27.1</a>
34597 standard output, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct tm, <a href="#7.27.1">7.27.1</a>
34598 unbuffered, <a href="#7.21.3">7.21.3</a> structure
34599 strerror function, <a href="#7.21.10.4">7.21.10.4</a>, <a href="#7.24.6.2">7.24.6.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34600 strerror_s function, <a href="#K.3.7.4.2">K.3.7.4.2</a>, <a href="#K.3.7.4.3">K.3.7.4.3</a> content, <a href="#6.7.2.3">6.7.2.3</a>
34602 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> thrd_current function, <a href="#7.26.5.2">7.26.5.2</a>
34603 initialization, <a href="#6.7.9">6.7.9</a> thrd_detach function, <a href="#7.26.5.3">7.26.5.3</a>
34604 member alignment, <a href="#6.7.2.1">6.7.2.1</a> thrd_equal function, <a href="#7.26.5.4">7.26.5.4</a>
34605 member name space, <a href="#6.2.3">6.2.3</a> thrd_exit function, <a href="#7.26.5.5">7.26.5.5</a>
34606 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> thrd_join function, <a href="#7.26.5.6">7.26.5.6</a>
34607 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> thrd_sleep function, <a href="#7.26.5.7">7.26.5.7</a>
34608 specifier, <a href="#6.7.2.1">6.7.2.1</a> thrd_start_t type, <a href="#7.26.1">7.26.1</a>
34609 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> thrd_t type, <a href="#7.26.1">7.26.1</a>
34610 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> thrd_yield function, <a href="#7.26.5.8">7.26.5.8</a>
34611 strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.4.5">7.24.4.5</a> thread of execution, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.6">7.6</a>, <a href="#7.22.4.6">7.22.4.6</a>,
34612 subnormal floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#K.3.6.2.1">K.3.6.2.1</a>
34613 subscripting, <a href="#6.5.2.1">6.5.2.1</a> thread storage duration, <a href="#6.2.4">6.2.4</a>, <a href="#7.6">7.6</a>
34614 subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a> threads header, <a href="#7.26">7.26</a>, <a href="#7.31.15">7.31.15</a>
34615 subtraction operator (-), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> threads.h header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.26">7.26</a>,
34616 suffix <a href="#7.31.15">7.31.15</a>
34617 floating constant, <a href="#6.4.4.2">6.4.4.2</a> time
34618 integer constant, <a href="#6.4.4.1">6.4.4.1</a> broken down, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.3">7.27.3</a>, <a href="#7.27.3.1">7.27.3.1</a>,
34619 switch body, <a href="#6.8.4.2">6.8.4.2</a> <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#7.27.3.5">7.27.3.5</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>,
34620 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a>
34621 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> calendar, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.2">7.27.2.2</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.2.4">7.27.2.4</a>,
34622 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> <a href="#7.27.3.2">7.27.3.2</a>, <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>,
34623 swprintf function, <a href="#7.29.2.3">7.29.2.3</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a>
34624 <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a> components, <a href="#7.27.1">7.27.1</a>, <a href="#K.3.8.1">K.3.8.1</a>
34625 swprintf_s function, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a> conversion functions, <a href="#7.27.3">7.27.3</a>, <a href="#K.3.8.2">K.3.8.2</a>
34626 swscanf function, <a href="#7.29.2.4">7.29.2.4</a>, <a href="#7.29.2.8">7.29.2.8</a> wide character, <a href="#7.29.5">7.29.5</a>
34627 swscanf_s function, <a href="#K.3.9.1.5">K.3.9.1.5</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a> local, <a href="#7.27.1">7.27.1</a>
34628 symbols, <a href="#3">3</a> manipulation functions, <a href="#7.27.2">7.27.2</a>
34629 synchronization operation, <a href="#5.1.2.4">5.1.2.4</a> normalized broken down, <a href="#K.3.8.1">K.3.8.1</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>
34630 synchronize with, <a href="#5.1.2.4">5.1.2.4</a> time base, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.5">7.27.2.5</a>
34631 syntactic categories, <a href="#6.1">6.1</a> time function, <a href="#7.27.2.4">7.27.2.4</a>
34632 syntax notation, <a href="#6.1">6.1</a> time.h header, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a>
34633 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> time_t type, <a href="#7.27.1">7.27.1</a>
34634 syntax summary, language, <a href="#A">A</a> TIME_UTC macro, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.26.4.4">7.26.4.4</a>, <a href="#7.26.5.7">7.26.5.7</a>,
34635 system function, <a href="#7.22.4.8">7.22.4.8</a> <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.5">7.27.2.5</a>
34636 timespec structure type, <a href="#7.27.1">7.27.1</a>
34637 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> timespec_get function, <a href="#7.27.2.5">7.27.2.5</a>
34638 tag compatibility, <a href="#6.2.7">6.2.7</a> tm structure type, <a href="#7.27.1">7.27.1</a>, <a href="#7.29.1">7.29.1</a>, <a href="#K.3.8.1">K.3.8.1</a>
34639 tag name space, <a href="#6.2.3">6.2.3</a> TMP_MAX macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.4">7.21.4.4</a>
34640 tags, <a href="#6.7.2.3">6.7.2.3</a> TMP_MAX_S macro, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34641 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.10.1.7">F.10.1.7</a> tmpfile function, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>
34642 tan type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> tmpfile_s function, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34643 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.10.2.6">F.10.2.6</a> tmpnam function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.4">7.21.4.4</a>,
34644 tanh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#K.3.5.1.2">K.3.5.1.2</a>
34645 temporary lifetime, <a href="#6.2.4">6.2.4</a> tmpnam_s function, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34646 tentative definition, <a href="#6.9.2">6.9.2</a> token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens
34647 terms, <a href="#3">3</a> token concatenation, <a href="#6.10.3.3">6.10.3.3</a>
34648 text streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a> token pasting, <a href="#6.10.3.3">6.10.3.3</a>
34649 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.10.5.4">F.10.5.4</a> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
34650 tgamma type-generic macro, <a href="#7.25">7.25</a> toupper function, <a href="#7.4.2.2">7.4.2.2</a>
34651 tgmath.h header, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> towctrans function, <a href="#7.30.3.2.1">7.30.3.2.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>
34652 thrd_create function, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.5.1">7.26.5.1</a> towlower function, <a href="#7.30.3.1.1">7.30.3.1.1</a>, <a href="#7.30.3.2.1">7.30.3.2.1</a>
34654 towupper function, <a href="#7.30.3.1.2">7.30.3.1.2</a>, <a href="#7.30.3.2.1">7.30.3.2.1</a> UCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34655 translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a> UINT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a>
34656 translation limits, <a href="#5.2.4.1">5.2.4.1</a> uint_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a>
34657 translation phases, <a href="#5.1.1.2">5.1.1.2</a> uint_least16_t type, <a href="#7.28">7.28</a>
34658 translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a> uint_least32_t type, <a href="#7.28">7.28</a>
34659 trap, see perform a trap UINT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a>
34660 trap representation, <a href="#3.19.4">3.19.4</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, uint_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a>
34661 <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.3">6.5.2.3</a> UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34662 trigonometric functions UINTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a>
34663 complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
34664 real, <a href="#7.12.4">7.12.4</a>, <a href="#F.10.1">F.10.1</a> uintmax_t type, <a href="#7.20.1.5">7.20.1.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34665 trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34666 true macro, <a href="#7.18">7.18</a> UINTN_C macros, <a href="#7.20.4.1">7.20.4.1</a>
34667 trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.10.6.8">F.10.6.8</a> UINTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a>
34668 trunc type-generic macro, <a href="#7.25">7.25</a> uintN_t types, <a href="#7.20.1.1">7.20.1.1</a>
34669 truncation, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.3">7.21.5.3</a> UINTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a>
34670 truncation toward zero, <a href="#6.5.5">6.5.5</a> uintptr_t type, <a href="#7.20.1.4">7.20.1.4</a>
34671 tss_create function, <a href="#7.26.6.1">7.26.6.1</a> ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>,
34672 tss_delete function, <a href="#7.26.6.2">7.26.6.2</a> <a href="#7.29.4.1.2">7.29.4.1.2</a>
34673 TSS_DTOR_ITERATIONS macro, <a href="#7.26.1">7.26.1</a> ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>,
34674 tss_dtor_t type, <a href="#7.26.1">7.26.1</a> <a href="#7.29.4.1.2">7.29.4.1.2</a>
34675 tss_get function, <a href="#7.26.6.3">7.26.6.3</a> unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a>
34676 tss_set function, <a href="#7.26.6.4">7.26.6.4</a> unary expression, <a href="#6.5.3">6.5.3</a>
34677 tss_t type, <a href="#7.26.1">7.26.1</a> unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
34678 two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a> unary operators, <a href="#6.5.3">6.5.3</a>
34679 type category, <a href="#6.2.5">6.2.5</a> unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a>
34680 type conversion, <a href="#6.3">6.3</a> unbuffered stream, <a href="#7.21.3">7.21.3</a>
34681 type definitions, <a href="#6.7.8">6.7.8</a> undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>,
34682 type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a> <a href="#7.1.4">7.1.4</a>
34683 type names, <a href="#6.7.7">6.7.7</a> undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a>
34684 type punning, <a href="#6.5.2.3">6.5.2.3</a> underscore character, <a href="#6.4.2.1">6.4.2.1</a>
34685 type qualifiers, <a href="#6.7.3">6.7.3</a> underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a>
34686 type specifiers, <a href="#6.7.2">6.7.2</a> ungetc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
34687 type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#7.21.9.3">7.21.9.3</a>
34688 type-generic math header, <a href="#7.25">7.25</a> ungetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.10">7.29.3.10</a>
34689 typedef declaration, <a href="#6.7.8">6.7.8</a> Unicode, <a href="#7.28">7.28</a>, see also char16_t type,
34690 typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.8">6.7.8</a> char32_t type, wchar_t type
34691 types, <a href="#6.2.5">6.2.5</a> Unicode required set, <a href="#6.10.8.2">6.10.8.2</a>
34692 atomic, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>, unicode utilities header, <a href="#7.28">7.28</a>
34693 <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, <a href="#6.7.2.4">6.7.2.4</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.17.6">7.17.6</a> union
34694 character, <a href="#6.7.9">6.7.9</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34695 compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.6">6.7.6</a> content, <a href="#6.7.2.3">6.7.2.3</a>
34696 complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
34697 composite, <a href="#6.2.7">6.2.7</a> initialization, <a href="#6.7.9">6.7.9</a>
34698 const qualified, <a href="#6.7.3">6.7.3</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
34699 conversions, <a href="#6.3">6.3</a> member name space, <a href="#6.2.3">6.2.3</a>
34700 imaginary, <a href="#G">G</a> member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>
34701 restrict qualified, <a href="#6.7.3">6.7.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34702 volatile qualified, <a href="#6.7.3">6.7.3</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
34703 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
34704 uchar.h header, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28">7.28</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
34706 universal character name, <a href="#6.4.3">6.4.3</a> value bits, <a href="#6.2.6.2">6.2.6.2</a>
34707 unnormalized floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a> variable arguments, <a href="#6.10.3">6.10.3</a>
34708 unqualified type, <a href="#6.2.5">6.2.5</a> variable arguments header, <a href="#7.16">7.16</a>
34709 unqualified version of type, <a href="#6.2.5">6.2.5</a> variable length array, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>
34710 unsequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.5.16">6.5.16</a>, see also variably modified type, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>
34711 indeterminately sequenced, sequenced vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
34712 before vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
34713 unsigned char type, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a> <a href="#7.4.1.10">7.4.1.10</a>
34714 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> vfprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#K.3.5.3.8">K.3.5.3.8</a>
34715 unsigned integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> vfprintf_s function, <a href="#K.3.5.3.8">K.3.5.3.8</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>,
34716 unsigned type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34717 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> vfscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>
34718 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, vfscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34719 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a> <a href="#K.3.5.3.14">K.3.5.3.14</a>
34720 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vfwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.5">7.29.2.5</a>, <a href="#K.3.9.1.6">K.3.9.1.6</a>
34721 unspecified value, <a href="#3.19.3">3.19.3</a> vfwprintf_s function, <a href="#K.3.9.1.6">K.3.9.1.6</a>
34722 uppercase letter, <a href="#5.2.1">5.2.1</a> vfwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.3.10">7.29.3.10</a>
34723 use of library functions, <a href="#7.1.4">7.1.4</a> vfwscanf_s function, <a href="#K.3.9.1.7">K.3.9.1.7</a>
34724 USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
34725 usual arithmetic conversions, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.5.5">6.5.5</a>, <a href="#6.5.6">6.5.6</a>, visible sequence of side effects, <a href="#5.1.2.4">5.1.2.4</a>
34726 <a href="#6.5.8">6.5.8</a>, <a href="#6.5.9">6.5.9</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>, <a href="#6.5.15">6.5.15</a> visible side effect, <a href="#5.1.2.4">5.1.2.4</a>
34727 UTF-16, <a href="#6.10.8.2">6.10.8.2</a> VLA, see variable length array
34728 UTF-32, <a href="#6.10.8.2">6.10.8.2</a> void expression, <a href="#6.3.2.2">6.3.2.2</a>
34729 UTF-8 string literal, see string literal void function parameter, <a href="#6.7.6.3">6.7.6.3</a>
34730 utilities, general, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#K.3.6">K.3.6</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>,
34731 wide string, <a href="#7.29.4">7.29.4</a>, <a href="#K.3.9.2">K.3.9.2</a> <a href="#K.3.9.1.2">K.3.9.1.2</a>
34732 utilities, unicode, <a href="#7.28">7.28</a> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
34733 volatile storage, <a href="#5.1.2.3">5.1.2.3</a>
34734 va_arg macro, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#7.16.1.2">7.16.1.2</a>, volatile type qualifier, <a href="#6.7.3">6.7.3</a>
34735 <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
34736 <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, vprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.10">7.21.6.10</a>,
34737 <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#K.3.5.3.10">K.3.5.3.10</a>
34738 <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, vprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.10">K.3.5.3.10</a>,
34739 <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34740 va_copy macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, vscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.11">7.21.6.11</a>
34741 <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a> vscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34742 va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.3">7.16.1.3</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34743 <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, vsnprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.12">7.21.6.12</a>,
34744 <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>
34745 <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, vsnprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34746 <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34747 <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> vsnwprintf_s function, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a>
34748 va_list type, <a href="#7.16">7.16</a>, <a href="#7.16.1.3">7.16.1.3</a> vsprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.13">7.21.6.13</a>,
34749 va_start macro, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>
34750 <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>, <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, vsprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34751 <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34752 <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, vsscanf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.14">7.21.6.14</a>
34753 <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>, vsscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34754 <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34755 <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> vswprintf function, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#K.3.9.1.8">K.3.9.1.8</a>,
34756 value, <a href="#3.19">3.19</a> <a href="#K.3.9.1.9">K.3.9.1.9</a>
34758 vswprintf_s function, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a> wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34759 vswscanf function, <a href="#7.29.2.8">7.29.2.8</a> wcstombs function, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.29.6.4">7.29.6.4</a>
34760 vswscanf_s function, <a href="#K.3.9.1.10">K.3.9.1.10</a> wcstombs_s function, <a href="#K.3.6.5.2">K.3.6.5.2</a>
34761 vwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#K.3.9.1.11">K.3.9.1.11</a> wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>,
34762 vwprintf_s function, <a href="#K.3.9.1.11">K.3.9.1.11</a> <a href="#7.29.4.1.2">7.29.4.1.2</a>
34763 vwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#7.29.3.10">7.29.3.10</a> wcstoull function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34764 vwscanf_s function, <a href="#K.3.9.1.12">K.3.9.1.12</a> wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a>
34765 wcsxfrm function, <a href="#7.29.4.4.4">7.29.4.4.4</a>
34766 warnings, <a href="#I">I</a> wctob function, <a href="#7.29.6.1.2">7.29.6.1.2</a>, <a href="#7.30.2.1">7.30.2.1</a>
34767 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29">7.29</a>, <a href="#7.31.16">7.31.16</a>, wctomb function, <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.29.6.3">7.29.6.3</a>
34768 <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> wctomb_s function, <a href="#K.3.6.4.1">K.3.6.4.1</a>
34769 WCHAR_MAX macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.29.1">7.29.1</a> wctrans function, <a href="#7.30.3.2.1">7.30.3.2.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>
34770 WCHAR_MIN macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.29.1">7.29.1</a> wctrans_t type, <a href="#7.30.1">7.30.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>
34771 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>, wctype function, <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a>
34772 <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22">7.22</a>, <a href="#7.29.1">7.29.1</a>, wctype.h header, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a>
34773 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a> wctype_t type, <a href="#7.30.1">7.30.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a>
34774 wcrtomb function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.1">7.29.1</a>, weaker, <a href="#6.2.8">6.2.8</a>
34775 <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#J.1">J.1</a>, WEOF macro, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.3.6">7.29.3.6</a>,
34776 <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> <a href="#7.29.3.7">7.29.3.7</a>, <a href="#7.29.3.8">7.29.3.8</a>, <a href="#7.29.3.9">7.29.3.9</a>, <a href="#7.29.3.10">7.29.3.10</a>,
34777 wcrtomb_s function, <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a> <a href="#7.29.6.1.1">7.29.6.1.1</a>, <a href="#7.30.1">7.30.1</a>
34778 wcscat function, <a href="#7.29.4.3.1">7.29.4.3.1</a> while statement, <a href="#6.8.5.1">6.8.5.1</a>
34779 wcscat_s function, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a> white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
34780 wcschr function, <a href="#7.29.4.5.1">7.29.4.5.1</a> <a href="#7.30.2.1.10">7.30.2.1.10</a>
34781 wcscmp function, <a href="#7.29.4.4.1">7.29.4.4.1</a>, <a href="#7.29.4.4.4">7.29.4.4.4</a> white-space characters, <a href="#6.4">6.4</a>
34782 wcscoll function, <a href="#7.29.4.4.2">7.29.4.4.2</a>, <a href="#7.29.4.4.4">7.29.4.4.4</a> wide character, <a href="#3.7.3">3.7.3</a>
34783 wcscpy function, <a href="#7.29.4.2.1">7.29.4.2.1</a> case mapping functions, <a href="#7.30.3.1">7.30.3.1</a>
34784 wcscpy_s function, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a> extensible, <a href="#7.30.3.2">7.30.3.2</a>
34785 wcscspn function, <a href="#7.29.4.5.2">7.29.4.5.2</a> classification functions, <a href="#7.30.2.1">7.30.2.1</a>
34786 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.29.5.1">7.29.5.1</a> extensible, <a href="#7.30.2.2">7.30.2.2</a>
34787 wcslen function, <a href="#7.29.4.6.1">7.29.4.6.1</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
34788 wcsncat function, <a href="#7.29.4.3.2">7.29.4.3.2</a> formatted input/output functions, <a href="#7.29.2">7.29.2</a>,
34789 wcsncat_s function, <a href="#K.3.9.2.2.2">K.3.9.2.2.2</a> <a href="#K.3.9.1">K.3.9.1</a>
34790 wcsncmp function, <a href="#7.29.4.4.3">7.29.4.4.3</a> input functions, <a href="#7.21.1">7.21.1</a>
34791 wcsncpy function, <a href="#7.29.4.2.2">7.29.4.2.2</a> input/output functions, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3">7.29.3</a>
34792 wcsncpy_s function, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a> output functions, <a href="#7.21.1">7.21.1</a>
34793 wcsnlen_s function, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a> single-byte conversion functions, <a href="#7.29.6.1">7.29.6.1</a>
34794 wcspbrk function, <a href="#7.29.4.5.3">7.29.4.5.3</a> wide character classification and mapping utilities
34795 wcsrchr function, <a href="#7.29.4.5.4">7.29.4.5.4</a> header, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a>
34796 wcsrtombs function, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> wide string, <a href="#7.1.1">7.1.1</a>
34797 wcsrtombs_s function, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> wide string comparison functions, <a href="#7.29.4.4">7.29.4.4</a>
34798 wcsspn function, <a href="#7.29.4.5.5">7.29.4.5.5</a> wide string concatenation functions, <a href="#7.29.4.3">7.29.4.3</a>,
34799 wcsstr function, <a href="#7.29.4.5.6">7.29.4.5.6</a> <a href="#K.3.9.2.2">K.3.9.2.2</a>
34800 wcstod function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a> wide string copying functions, <a href="#7.29.4.2">7.29.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a>
34801 wcstod function, <a href="#7.29.4.1.1">7.29.4.1.1</a> wide string literal, see string literal
34802 wcstof function, <a href="#7.29.4.1.1">7.29.4.1.1</a> wide string miscellaneous functions, <a href="#7.29.4.6">7.29.4.6</a>,
34803 wcstoimax function, <a href="#7.8.2.4">7.8.2.4</a> <a href="#K.3.9.2.4">K.3.9.2.4</a>
34804 wcstok function, <a href="#7.29.4.5.7">7.29.4.5.7</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
34805 wcstok_s function, <a href="#K.3.9.2.3.1">K.3.9.2.3.1</a> <a href="#7.29.4.1">7.29.4.1</a>
34806 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>, wide string search functions, <a href="#7.29.4.5">7.29.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a>
34807 <a href="#7.29.4.1.2">7.29.4.1.2</a> wide-oriented stream, <a href="#7.21.2">7.21.2</a>
34808 wcstold function, <a href="#7.29.4.1.1">7.29.4.1.1</a> width, <a href="#6.2.6.2">6.2.6.2</a>
34810 WINT_MAX macro, <a href="#7.20.3">7.20.3</a>
34811 WINT_MIN macro, <a href="#7.20.3">7.20.3</a>
34812 wint_t type, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>,
34813 <a href="#7.30.1">7.30.1</a>
34814 wmemchr function, <a href="#7.29.4.5.8">7.29.4.5.8</a>
34815 wmemcmp function, <a href="#7.29.4.4.5">7.29.4.4.5</a>
34816 wmemcpy function, <a href="#7.29.4.2.3">7.29.4.2.3</a>
34817 wmemcpy_s function, <a href="#K.3.9.2.1.3">K.3.9.2.1.3</a>
34818 wmemmove function, <a href="#7.29.4.2.4">7.29.4.2.4</a>
34819 wmemmove_s function, <a href="#K.3.9.2.1.4">K.3.9.2.1.4</a>
34820 wmemset function, <a href="#7.29.4.6.2">7.29.4.6.2</a>
34821 wprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.11">7.29.2.11</a>,
34822 <a href="#K.3.9.1.13">K.3.9.1.13</a>
34823 wprintf_s function, <a href="#K.3.9.1.13">K.3.9.1.13</a>
34824 wscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#7.29.2.12">7.29.2.12</a>,
34825 <a href="#7.29.3.10">7.29.3.10</a>
34826 wscanf_s function, <a href="#K.3.9.1.12">K.3.9.1.12</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a>
34828 xor macro, <a href="#7.9">7.9</a>
34829 xor_eq macro, <a href="#7.9">7.9</a> *
34831 <p><small><a href="#Contents">Contents</a></small>