1 <html><head><title>WG14/N1256 Septermber 7, 2007 ISO/IEC 9899:TC3</title></head><body>
3 WG14/N1256 Committee Draft -- Septermber 7, 2007 ISO/IEC 9899:TC3
8 <h2><a name="Contents" href="#Contents">Contents</a></h2>
10 <li><a href="#Foreword">Foreword</a>
11 <li><a href="#Introduction">Introduction</a>
12 <li><a href="#1">1. Scope</a>
13 <li><a href="#2">2. Normative references</a>
14 <li><a href="#3">3. Terms, definitions, and symbols</a>
15 <li><a href="#4">4. Conformance</a>
16 <li><a href="#5">5. Environment</a>
18 <li><a href="#5.1"> 5.1 Conceptual models</a>
20 <li><a href="#5.1.1"> 5.1.1 Translation environment</a>
21 <li><a href="#5.1.2"> 5.1.2 Execution environments</a>
23 <li><a href="#5.2"> 5.2 Environmental considerations</a>
25 <li><a href="#5.2.1"> 5.2.1 Character sets</a>
26 <li><a href="#5.2.2"> 5.2.2 Character display semantics</a>
27 <li><a href="#5.2.3"> 5.2.3 Signals and interrupts</a>
28 <li><a href="#5.2.4"> 5.2.4 Environmental limits</a>
31 <li><a href="#6">6. Language</a>
33 <li><a href="#6.1"> 6.1 Notation</a>
34 <li><a href="#6.2"> 6.2 Concepts</a>
36 <li><a href="#6.2.1"> 6.2.1 Scopes of identifiers</a>
37 <li><a href="#6.2.2"> 6.2.2 Linkages of identifiers</a>
38 <li><a href="#6.2.3"> 6.2.3 Name spaces of identifiers</a>
39 <li><a href="#6.2.4"> 6.2.4 Storage durations of objects</a>
40 <li><a href="#6.2.5"> 6.2.5 Types</a>
41 <li><a href="#6.2.6"> 6.2.6 Representations of types</a>
42 <li><a href="#6.2.7"> 6.2.7 Compatible type and composite type</a>
44 <li><a href="#6.3"> 6.3 Conversions</a>
46 <li><a href="#6.3.1"> 6.3.1 Arithmetic operands</a>
47 <li><a href="#6.3.2"> 6.3.2 Other operands</a>
49 <li><a href="#6.4"> 6.4 Lexical elements</a>
51 <li><a href="#6.4.1"> 6.4.1 Keywords</a>
52 <li><a href="#6.4.2"> 6.4.2 Identifiers</a>
53 <li><a href="#6.4.3"> 6.4.3 Universal character names</a>
54 <li><a href="#6.4.4"> 6.4.4 Constants</a>
55 <li><a href="#6.4.5"> 6.4.5 String literals</a>
56 <li><a href="#6.4.6"> 6.4.6 Punctuators</a>
57 <li><a href="#6.4.7"> 6.4.7 Header names</a>
58 <li><a href="#6.4.8"> 6.4.8 Preprocessing numbers</a>
59 <li><a href="#6.4.9"> 6.4.9 Comments</a>
61 <li><a href="#6.5"> 6.5 Expressions</a>
64 <li><a href="#6.5.1"> 6.5.1 Primary expressions</a>
65 <li><a href="#6.5.2"> 6.5.2 Postfix operators</a>
66 <li><a href="#6.5.3"> 6.5.3 Unary operators</a>
67 <li><a href="#6.5.4"> 6.5.4 Cast operators</a>
68 <li><a href="#6.5.5"> 6.5.5 Multiplicative operators</a>
69 <li><a href="#6.5.6"> 6.5.6 Additive operators</a>
70 <li><a href="#6.5.7"> 6.5.7 Bitwise shift operators</a>
71 <li><a href="#6.5.8"> 6.5.8 Relational operators</a>
72 <li><a href="#6.5.9"> 6.5.9 Equality operators</a>
73 <li><a href="#6.5.10"> 6.5.10 Bitwise AND operator</a>
74 <li><a href="#6.5.11"> 6.5.11 Bitwise exclusive OR operator</a>
75 <li><a href="#6.5.12"> 6.5.12 Bitwise inclusive OR operator</a>
76 <li><a href="#6.5.13"> 6.5.13 Logical AND operator</a>
77 <li><a href="#6.5.14"> 6.5.14 Logical OR operator</a>
78 <li><a href="#6.5.15"> 6.5.15 Conditional operator</a>
79 <li><a href="#6.5.16"> 6.5.16 Assignment operators</a>
80 <li><a href="#6.5.17"> 6.5.17 Comma operator</a>
82 <li><a href="#6.6"> 6.6 Constant expressions</a>
83 <li><a href="#6.7"> 6.7 Declarations</a>
85 <li><a href="#6.7.1"> 6.7.1 Storage-class specifiers</a>
86 <li><a href="#6.7.2"> 6.7.2 Type specifiers</a>
87 <li><a href="#6.7.3"> 6.7.3 Type qualifiers</a>
88 <li><a href="#6.7.4"> 6.7.4 Function specifiers</a>
89 <li><a href="#6.7.5"> 6.7.5 Declarators</a>
90 <li><a href="#6.7.6"> 6.7.6 Type names</a>
91 <li><a href="#6.7.7"> 6.7.7 Type definitions</a>
92 <li><a href="#6.7.8"> 6.7.8 Initialization</a>
94 <li><a href="#6.8"> 6.8 Statements and blocks</a>
96 <li><a href="#6.8.1"> 6.8.1 Labeled statements</a>
97 <li><a href="#6.8.2"> 6.8.2 Compound statement</a>
98 <li><a href="#6.8.3"> 6.8.3 Expression and null statements</a>
99 <li><a href="#6.8.4"> 6.8.4 Selection statements</a>
100 <li><a href="#6.8.5"> 6.8.5 Iteration statements</a>
101 <li><a href="#6.8.6"> 6.8.6 Jump statements</a>
103 <li><a href="#6.9"> 6.9 External definitions</a>
105 <li><a href="#6.9.1"> 6.9.1 Function definitions</a>
106 <li><a href="#6.9.2"> 6.9.2 External object definitions</a>
108 <li><a href="#6.10"> 6.10 Preprocessing directives</a>
110 <li><a href="#6.10.1"> 6.10.1 Conditional inclusion</a>
111 <li><a href="#6.10.2"> 6.10.2 Source file inclusion</a>
112 <li><a href="#6.10.3"> 6.10.3 Macro replacement</a>
113 <li><a href="#6.10.4"> 6.10.4 Line control</a>
114 <li><a href="#6.10.5"> 6.10.5 Error directive</a>
115 <li><a href="#6.10.6"> 6.10.6 Pragma directive</a>
117 <li><a href="#6.10.7"> 6.10.7 Null directive</a>
118 <li><a href="#6.10.8"> 6.10.8 Predefined macro names</a>
119 <li><a href="#6.10.9"> 6.10.9 Pragma operator</a>
121 <li><a href="#6.11"> 6.11 Future language directions</a>
123 <li><a href="#6.11.1"> 6.11.1 Floating types</a>
124 <li><a href="#6.11.2"> 6.11.2 Linkages of identifiers</a>
125 <li><a href="#6.11.3"> 6.11.3 External names</a>
126 <li><a href="#6.11.4"> 6.11.4 Character escape sequences</a>
127 <li><a href="#6.11.5"> 6.11.5 Storage-class specifiers</a>
128 <li><a href="#6.11.6"> 6.11.6 Function declarators</a>
129 <li><a href="#6.11.7"> 6.11.7 Function definitions</a>
130 <li><a href="#6.11.8"> 6.11.8 Pragma directives</a>
131 <li><a href="#6.11.9"> 6.11.9 Predefined macro names</a>
134 <li><a href="#7">7. Library</a>
136 <li><a href="#7.1"> 7.1 Introduction</a>
138 <li><a href="#7.1.1"> 7.1.1 Definitions of terms</a>
139 <li><a href="#7.1.2"> 7.1.2 Standard headers</a>
140 <li><a href="#7.1.3"> 7.1.3 Reserved identifiers</a>
141 <li><a href="#7.1.4"> 7.1.4 Use of library functions</a>
143 <li><a href="#7.2"> 7.2 Diagnostics <assert.h></a>
145 <li><a href="#7.2.1"> 7.2.1 Program diagnostics</a>
147 <li><a href="#7.3"> 7.3 Complex arithmetic <complex.h></a>
149 <li><a href="#7.3.1"> 7.3.1 Introduction</a>
150 <li><a href="#7.3.2"> 7.3.2 Conventions</a>
151 <li><a href="#7.3.3"> 7.3.3 Branch cuts</a>
152 <li><a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma</a>
153 <li><a href="#7.3.5"> 7.3.5 Trigonometric functions</a>
154 <li><a href="#7.3.6"> 7.3.6 Hyperbolic functions</a>
155 <li><a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions</a>
156 <li><a href="#7.3.8"> 7.3.8 Power and absolute-value functions</a>
157 <li><a href="#7.3.9"> 7.3.9 Manipulation functions</a>
159 <li><a href="#7.4"> 7.4 Character handling <ctype.h></a>
161 <li><a href="#7.4.1"> 7.4.1 Character classification functions</a>
162 <li><a href="#7.4.2"> 7.4.2 Character case mapping functions</a>
164 <li><a href="#7.5"> 7.5 Errors <errno.h></a>
165 <li><a href="#7.6"> 7.6 Floating-point environment <fenv.h></a>
167 <li><a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma</a>
168 <li><a href="#7.6.2"> 7.6.2 Floating-point exceptions</a>
169 <li><a href="#7.6.3"> 7.6.3 Rounding</a>
170 <li><a href="#7.6.4"> 7.6.4 Environment</a>
172 <li><a href="#7.7"> 7.7 Characteristics of floating types <float.h></a>
173 <li><a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h></a>
175 <li><a href="#7.8.1"> 7.8.1 Macros for format specifiers</a>
176 <li><a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types</a>
179 <li><a href="#7.9"> 7.9 Alternative spellings <iso646.h></a>
180 <li><a href="#7.10"> 7.10 Sizes of integer types <limits.h></a>
181 <li><a href="#7.11"> 7.11 Localization <locale.h></a>
183 <li><a href="#7.11.1"> 7.11.1 Locale control</a>
184 <li><a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry</a>
186 <li><a href="#7.12"> 7.12 Mathematics <math.h></a>
188 <li><a href="#7.12.1"> 7.12.1 Treatment of error conditions</a>
189 <li><a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma</a>
190 <li><a href="#7.12.3"> 7.12.3 Classification macros</a>
191 <li><a href="#7.12.4"> 7.12.4 Trigonometric functions</a>
192 <li><a href="#7.12.5"> 7.12.5 Hyperbolic functions</a>
193 <li><a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions</a>
194 <li><a href="#7.12.7"> 7.12.7 Power and absolute-value functions</a>
195 <li><a href="#7.12.8"> 7.12.8 Error and gamma functions</a>
196 <li><a href="#7.12.9"> 7.12.9 Nearest integer functions</a>
197 <li><a href="#7.12.10"> 7.12.10 Remainder functions</a>
198 <li><a href="#7.12.11"> 7.12.11 Manipulation functions</a>
199 <li><a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions</a>
200 <li><a href="#7.12.13"> 7.12.13 Floating multiply-add</a>
201 <li><a href="#7.12.14"> 7.12.14 Comparison macros</a>
203 <li><a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h></a>
205 <li><a href="#7.13.1"> 7.13.1 Save calling environment</a>
206 <li><a href="#7.13.2"> 7.13.2 Restore calling environment</a>
208 <li><a href="#7.14"> 7.14 Signal handling <signal.h></a>
210 <li><a href="#7.14.1"> 7.14.1 Specify signal handling</a>
211 <li><a href="#7.14.2"> 7.14.2 Send signal</a>
213 <li><a href="#7.15"> 7.15 Variable arguments <stdarg.h></a>
215 <li><a href="#7.15.1"> 7.15.1 Variable argument list access macros</a>
217 <li><a href="#7.16"> 7.16 Boolean type and values <stdbool.h></a>
218 <li><a href="#7.17"> 7.17 Common definitions <stddef.h></a>
219 <li><a href="#7.18"> 7.18 Integer types <stdint.h></a>
221 <li><a href="#7.18.1"> 7.18.1 Integer types</a>
222 <li><a href="#7.18.2"> 7.18.2 Limits of specified-width integer types</a>
223 <li><a href="#7.18.3"> 7.18.3 Limits of other integer types</a>
224 <li><a href="#7.18.4"> 7.18.4 Macros for integer constants</a>
226 <li><a href="#7.19"> 7.19 Input/output <stdio.h></a>
228 <li><a href="#7.19.1"> 7.19.1 Introduction</a>
229 <li><a href="#7.19.2"> 7.19.2 Streams</a>
230 <li><a href="#7.19.3"> 7.19.3 Files</a>
231 <li><a href="#7.19.4"> 7.19.4 Operations on files</a>
232 <li><a href="#7.19.5"> 7.19.5 File access functions</a>
233 <li><a href="#7.19.6"> 7.19.6 Formatted input/output functions</a>
234 <li><a href="#7.19.7"> 7.19.7 Character input/output functions</a>
235 <li><a href="#7.19.8"> 7.19.8 Direct input/output functions</a>
237 <li><a href="#7.19.9"> 7.19.9 File positioning functions</a>
238 <li><a href="#7.19.10"> 7.19.10 Error-handling functions</a>
240 <li><a href="#7.20"> 7.20 General utilities <stdlib.h></a>
242 <li><a href="#7.20.1"> 7.20.1 Numeric conversion functions</a>
243 <li><a href="#7.20.2"> 7.20.2 Pseudo-random sequence generation functions</a>
244 <li><a href="#7.20.3"> 7.20.3 Memory management functions</a>
245 <li><a href="#7.20.4"> 7.20.4 Communication with the environment</a>
246 <li><a href="#7.20.5"> 7.20.5 Searching and sorting utilities</a>
247 <li><a href="#7.20.6"> 7.20.6 Integer arithmetic functions</a>
248 <li><a href="#7.20.7"> 7.20.7 Multibyte/wide character conversion functions</a>
249 <li><a href="#7.20.8"> 7.20.8 Multibyte/wide string conversion functions</a>
251 <li><a href="#7.21"> 7.21 String handling <string.h></a>
253 <li><a href="#7.21.1"> 7.21.1 String function conventions</a>
254 <li><a href="#7.21.2"> 7.21.2 Copying functions</a>
255 <li><a href="#7.21.3"> 7.21.3 Concatenation functions</a>
256 <li><a href="#7.21.4"> 7.21.4 Comparison functions</a>
257 <li><a href="#7.21.5"> 7.21.5 Search functions</a>
258 <li><a href="#7.21.6"> 7.21.6 Miscellaneous functions</a>
260 <li><a href="#7.22"> 7.22 Type-generic math <tgmath.h></a>
261 <li><a href="#7.23"> 7.23 Date and time <time.h></a>
263 <li><a href="#7.23.1"> 7.23.1 Components of time</a>
264 <li><a href="#7.23.2"> 7.23.2 Time manipulation functions</a>
265 <li><a href="#7.23.3"> 7.23.3 Time conversion functions</a>
267 <li><a href="#7.24"> 7.24 Extended multibyte and wide character utilities <wchar.h></a>
269 <li><a href="#7.24.1"> 7.24.1 Introduction</a>
270 <li><a href="#7.24.2"> 7.24.2 Formatted wide character input/output functions</a>
271 <li><a href="#7.24.3"> 7.24.3 Wide character input/output functions</a>
272 <li><a href="#7.24.4"> 7.24.4 General wide string utilities</a>
273 <li><a href="#7.24.5"> 7.24.5 Wide character time conversion functions</a>
274 <li><a href="#7.24.6"> 7.24.6 Extended multibyte/wide character conversion utilities</a>
276 <li><a href="#7.25"> 7.25 Wide character classification and mapping utilities <wctype.h></a>
278 <li><a href="#7.25.1"> 7.25.1 Introduction</a>
279 <li><a href="#7.25.2"> 7.25.2 Wide character classification utilities</a>
280 <li><a href="#7.25.3"> 7.25.3 Wide character case mapping utilities</a>
282 <li><a href="#7.26"> 7.26 Future library directions</a>
284 <li><a href="#7.26.1"> 7.26.1 Complex arithmetic <complex.h></a>
285 <li><a href="#7.26.2"> 7.26.2 Character handling <ctype.h></a>
286 <li><a href="#7.26.3"> 7.26.3 Errors <errno.h></a>
287 <li><a href="#7.26.4"> 7.26.4 Format conversion of integer types <inttypes.h></a>
288 <li><a href="#7.26.5"> 7.26.5 Localization <locale.h></a>
289 <li><a href="#7.26.6"> 7.26.6 Signal handling <signal.h></a>
290 <li><a href="#7.26.7"> 7.26.7 Boolean type and values <stdbool.h></a>
291 <li><a href="#7.26.8"> 7.26.8 Integer types <stdint.h></a>
292 <li><a href="#7.26.9"> 7.26.9 Input/output <stdio.h></a>
294 <li><a href="#7.26.10"> 7.26.10 General utilities <stdlib.h></a>
295 <li><a href="#7.26.11"> 7.26.11 String handling <string.h></a>
296 <li><a href="#7.26.12"> 7.26.12 Extended multibyte and wide character utilities <wchar.h></a>
297 <li><a href="#7.26.13"> 7.26.13 Wide character classification and mapping utilities <wctype.h></a>
300 <li><a href="#A">Annex A (informative) Language syntax summary</a>
302 <li><a href="#A.1"> A.1 Lexical grammar</a>
303 <li><a href="#A.2"> A.2 Phrase structure grammar</a>
304 <li><a href="#A.3"> A.3 Preprocessing directives</a>
306 <li><a href="#B">Annex B (informative) Library summary</a>
308 <li><a href="#B.1"> B.1 Diagnostics <assert.h></a>
309 <li><a href="#B.2"> B.2 Complex <complex.h></a>
310 <li><a href="#B.3"> B.3 Character handling <ctype.h></a>
311 <li><a href="#B.4"> B.4 Errors <errno.h></a>
312 <li><a href="#B.5"> B.5 Floating-point environment <fenv.h></a>
313 <li><a href="#B.6"> B.6 Characteristics of floating types <float.h></a>
314 <li><a href="#B.7"> B.7 Format conversion of integer types <inttypes.h></a>
315 <li><a href="#B.8"> B.8 Alternative spellings <iso646.h></a>
316 <li><a href="#B.9"> B.9 Sizes of integer types <limits.h></a>
317 <li><a href="#B.10"> B.10 Localization <locale.h></a>
318 <li><a href="#B.11"> B.11 Mathematics <math.h></a>
319 <li><a href="#B.12"> B.12 Nonlocal jumps <setjmp.h></a>
320 <li><a href="#B.13"> B.13 Signal handling <signal.h></a>
321 <li><a href="#B.14"> B.14 Variable arguments <stdarg.h></a>
322 <li><a href="#B.15"> B.15 Boolean type and values <stdbool.h></a>
323 <li><a href="#B.16"> B.16 Common definitions <stddef.h></a>
324 <li><a href="#B.17"> B.17 Integer types <stdint.h></a>
325 <li><a href="#B.18"> B.18 Input/output <stdio.h></a>
326 <li><a href="#B.19"> B.19 General utilities <stdlib.h></a>
327 <li><a href="#B.20"> B.20 String handling <string.h></a>
328 <li><a href="#B.21"> B.21 Type-generic math <tgmath.h></a>
329 <li><a href="#B.22"> B.22 Date and time <time.h></a>
330 <li><a href="#B.23"> B.23 Extended multibyte/wide character utilities <wchar.h></a>
331 <li><a href="#B.24"> B.24 Wide character classification and mapping utilities <wctype.h></a>
333 <li><a href="#C">Annex C (informative) Sequence points</a>
334 <li><a href="#D">Annex D (normative) Universal character names for identifiers</a>
335 <li><a href="#E">Annex E (informative) Implementation limits</a>
336 <li><a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic</a>
338 <li><a href="#F.1"> F.1 Introduction</a>
339 <li><a href="#F.2"> F.2 Types</a>
340 <li><a href="#F.3"> F.3 Operators and functions</a>
342 <li><a href="#F.4"> F.4 Floating to integer conversion</a>
343 <li><a href="#F.5"> F.5 Binary-decimal conversion</a>
344 <li><a href="#F.6"> F.6 Contracted expressions</a>
345 <li><a href="#F.7"> F.7 Floating-point environment</a>
346 <li><a href="#F.8"> F.8 Optimization</a>
347 <li><a href="#F.9"> F.9 Mathematics <math.h></a>
349 <li><a href="#G">Annex G (informative) IEC 60559-compatible complex arithmetic</a>
351 <li><a href="#G.1"> G.1 Introduction</a>
352 <li><a href="#G.2"> G.2 Types</a>
353 <li><a href="#G.3"> G.3 Conventions</a>
354 <li><a href="#G.4"> G.4 Conversions</a>
355 <li><a href="#G.5"> G.5 Binary operators</a>
356 <li><a href="#G.6"> G.6 Complex arithmetic <complex.h></a>
357 <li><a href="#G.7"> G.7 Type-generic math <tgmath.h></a>
359 <li><a href="#H">Annex H (informative) Language independent arithmetic</a>
361 <li><a href="#H.1"> H.1 Introduction</a>
362 <li><a href="#H.2"> H.2 Types</a>
363 <li><a href="#H.3"> H.3 Notification</a>
365 <li><a href="#I">Annex I (informative) Common warnings</a>
366 <li><a href="#J">Annex J (informative) Portability issues</a>
368 <li><a href="#J.1"> J.1 Unspecified behavior</a>
369 <li><a href="#J.2"> J.2 Undefined behavior</a>
370 <li><a href="#J.3"> J.3 Implementation-defined behavior</a>
371 <li><a href="#J.4"> J.4 Locale-specific behavior</a>
372 <li><a href="#J.5"> J.5 Common extensions</a>
374 <li><a href="#Bibliography">Bibliography</a>
375 <li><a href="#Index">Index</a>
380 <h2><a name="Foreword" href="#Foreword">Foreword</a></h2>
382 ISO (the International Organization for Standardization) and IEC (the International
383 Electrotechnical Commission) form the specialized system for worldwide
384 standardization. National bodies that are member of ISO or IEC participate in the
385 development of International Standards through technical committees established by the
386 respective organization to deal with particular fields of technical activity. ISO and IEC
387 technical committees collaborate in fields of mutual interest. Other international
388 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
389 take part in the work.
391 International Standards are drafted in accordance with the rules given in the ISO/IEC
394 In the field of information technology, ISO and IEC have established a joint technical
395 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
396 committee are circulated to national bodies for voting. Publication as an International
397 Standard requires approval by at least 75% of the national bodies casting a vote.
399 International Standard ISO/IEC 9899 was prepared by Joint Technical Committee
400 ISO/IEC JTC 1, Information technology, Subcommittee SC 22, Programming languages,
401 their environments and system software interfaces. The Working Group responsible for
402 this standard (WG 14) maintains a site on the World Wide Web at
403 http://www.open-std.org/JTC1/SC22/WG14/ containing additional
404 information relevant to this standard such as a Rationale for many of the decisions made
405 during its preparation and a log of Defect Reports and Responses.
407 This second edition cancels and replaces the first edition, ISO/IEC 9899:1990, as
408 amended and corrected by ISO/IEC 9899/COR1:1994, ISO/IEC 9899/AMD1:1995, and
409 ISO/IEC 9899/COR2:1996. Major changes from the previous edition include:
411 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
413 <li> wide character library support in <a href="#7.24"><wchar.h></a> and <a href="#7.25"><wctype.h></a> (originally
415 <li> more precise aliasing rules via effective type
416 <li> restricted pointers
417 <li> variable length arrays
418 <li> flexible array members
419 <li> static and type qualifiers in parameter array declarators
420 <li> complex (and imaginary) support in <a href="#7.3"><complex.h></a>
421 <li> type-generic math macros in <a href="#7.22"><tgmath.h></a>
422 <li> the long long int type and library functions
424 <li> increased minimum translation limits
425 <li> additional floating-point characteristics in <a href="#7.7"><float.h></a>
426 <li> remove implicit int
427 <li> reliable integer division
428 <li> universal character names (\u and \U)
429 <li> extended identifiers
430 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
432 <li> compound literals
433 <li> designated initializers
435 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.18"><stdint.h></a>
436 <li> remove implicit function declaration
437 <li> preprocessor arithmetic done in intmax_t/uintmax_t
438 <li> mixed declarations and code
439 <li> new block scopes for selection and iteration statements
440 <li> integer constant type rules
441 <li> integer promotion rules
442 <li> macros with a variable number of arguments
443 <li> the vscanf family of functions in <a href="#7.19"><stdio.h></a> and <a href="#7.24"><wchar.h></a>
444 <li> additional math library functions in <a href="#7.12"><math.h></a>
445 <li> treatment of error conditions by math library functions (math_errhandling)
446 <li> floating-point environment access in <a href="#7.6"><fenv.h></a>
447 <li> IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
448 <li> trailing comma allowed in enum declaration
449 <li> %lf conversion specifier allowed in printf
450 <li> inline functions
451 <li> the snprintf family of functions in <a href="#7.19"><stdio.h></a>
452 <li> boolean type in <a href="#7.16"><stdbool.h></a>
453 <li> idempotent type qualifiers
454 <li> empty macro arguments
456 <li> new structure type compatibility rules (tag compatibility)
457 <li> additional predefined macro names
458 <li> _Pragma preprocessing operator
459 <li> standard pragmas
460 <li> __func__ predefined identifier
462 <li> additional strftime conversion specifiers
463 <li> LIA compatibility annex
464 <li> deprecate ungetc at the beginning of a binary file
465 <li> remove deprecation of aliased array parameters
466 <li> conversion of array to pointer not limited to lvalues
467 <li> relaxed constraints on aggregate and union initialization
468 <li> relaxed restrictions on portable header names
469 <li> return without expression not permitted in function that returns a value (and vice
473 Annexes D and F form a normative part of this standard; annexes A, B, C, E, G, H, I, J,
474 the bibliography, and the index are for information only. In accordance with Part 3 of the
475 ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples are
476 also for information only.
479 <h2><a name="Introduction" href="#Introduction">Introduction</a></h2>
481 With the introduction of new devices and extended character sets, new features may be
482 added to this International Standard. Subclauses in the language and library clauses warn
483 implementors and programmers of usages which, though valid in themselves, may
484 conflict with future additions.
486 Certain features are obsolescent, which means that they may be considered for
487 withdrawal in future revisions of this International Standard. They are retained because
488 of their widespread use, but their use in new implementations (for implementation
489 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.26">7.26</a>]) is discouraged.
491 This International Standard is divided into four major subdivisions:
493 <li> preliminary elements (clauses 1-4);
494 <li> the characteristics of environments that translate and execute C programs (clause 5);
495 <li> the language syntax, constraints, and semantics (clause 6);
496 <li> the library facilities (clause 7).
499 Examples are provided to illustrate possible forms of the constructions described.
500 Footnotes are provided to emphasize consequences of the rules described in that
501 subclause or elsewhere in this International Standard. References are used to refer to
502 other related subclauses. Recommendations are provided to give advice or guidance to
503 implementors. Annexes provide additional information and summarize the information
504 contained in this International Standard. A bibliography lists documents that were
505 referred to during the preparation of the standard.
507 The language clause (clause 6) is derived from ''The C Reference Manual''.
509 The library clause (clause 7) is based on the 1984 /usr/group Standard.
512 <h1>Programming languages -- C</h1>
518 <h2><a name="1" href="#1">1. Scope</a></h2>
520 This International Standard specifies the form and establishes the interpretation of
521 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
523 <li> the representation of C programs;
524 <li> the syntax and constraints of the C language;
525 <li> the semantic rules for interpreting C programs;
526 <li> the representation of input data to be processed by C programs;
527 <li> the representation of output data produced by C programs;
528 <li> the restrictions and limits imposed by a conforming implementation of C.
531 This International Standard does not specify
533 <li> the mechanism by which C programs are transformed for use by a data-processing
535 <li> the mechanism by which C programs are invoked for use by a data-processing
537 <li> the mechanism by which input data are transformed for use by a C program;
538 <li> the mechanism by which output data are transformed after being produced by a C
540 <li> the size or complexity of a program and its data that will exceed the capacity of any
541 specific data-processing system or the capacity of a particular processor;
545 <li> all minimal requirements of a data-processing system that is capable of supporting a
546 conforming implementation.
551 <p><small><a name="note1" href="#note1">1)</a> This International Standard is designed to promote the portability of C programs among a variety of
552 data-processing systems. It is intended for use by implementors and programmers.
555 <h2><a name="2" href="#2">2. Normative references</a></h2>
557 The following normative documents contain provisions which, through reference in this
558 text, constitute provisions of this International Standard. For dated references,
559 subsequent amendments to, or revisions of, any of these publications do not apply.
560 However, parties to agreements based on this International Standard are encouraged to
561 investigate the possibility of applying the most recent editions of the normative
562 documents indicated below. For undated references, the latest edition of the normative
563 document referred to applies. Members of ISO and IEC maintain registers of currently
564 valid International Standards.
566 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
567 use in the physical sciences and technology.
569 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
572 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
575 ISO 4217, Codes for the representation of currencies and funds.
577 ISO 8601, Data elements and interchange formats -- Information interchange --
578 Representation of dates and times.
580 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
583 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
584 designated IEC 559:1989).
587 <h2><a name="3" href="#3">3. Terms, definitions, and symbols</a></h2>
589 For the purposes of this International Standard, the following definitions apply. Other
590 terms are defined where they appear in italic type or on the left side of a syntax rule.
591 Terms explicitly defined in this International Standard are not to be presumed to refer
592 implicitly to similar terms defined elsewhere. Terms not defined in this International
593 Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
594 defined in this International Standard are to be interpreted according to ISO 31-11.
596 <h3><a name="3.1" href="#3.1">3.1</a></h3>
599 <execution-time action> to read or modify the value of an object
601 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
604 NOTE 2 "Modify'' includes the case where the new value being stored is the same as the previous value.
607 NOTE 3 Expressions that are not evaluated do not access objects.
610 <h3><a name="3.2" href="#3.2">3.2</a></h3>
612 <b> alignment</b><br>
613 requirement that objects of a particular type be located on storage boundaries with
614 addresses that are particular multiples of a byte address
616 <h3><a name="3.3" href="#3.3">3.3</a></h3>
620 actual parameter (deprecated)<br>
621 expression in the comma-separated list bounded by the parentheses in a function call
622 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
623 by the parentheses in a function-like macro invocation
625 <h3><a name="3.4" href="#3.4">3.4</a></h3>
628 external appearance or action
630 <h4><a name="3.4.1" href="#3.4.1">3.4.1</a></h4>
632 <b> implementation-defined behavior</b><br>
633 unspecified behavior where each implementation documents how the choice is made
635 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
636 when a signed integer is shifted right.
639 <h4><a name="3.4.2" href="#3.4.2">3.4.2</a></h4>
641 <b> locale-specific behavior</b><br>
642 behavior that depends on local conventions of nationality, culture, and language that each
643 implementation documents
646 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
647 characters other than the 26 lowercase Latin letters.
650 <h4><a name="3.4.3" href="#3.4.3">3.4.3</a></h4>
652 <b> undefined behavior</b><br>
653 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
654 for which this International Standard imposes no requirements
656 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
657 results, to behaving during translation or program execution in a documented manner characteristic of the
658 environment (with or without the issuance of a diagnostic message), to terminating a translation or
659 execution (with the issuance of a diagnostic message).
662 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
665 <h4><a name="3.4.4" href="#3.4.4">3.4.4</a></h4>
667 <b> unspecified behavior</b><br>
668 use of an unspecified value, or other behavior where this International Standard provides
669 two or more possibilities and imposes no further requirements on which is chosen in any
672 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
676 <h3><a name="3.5" href="#3.5">3.5</a></h3>
679 unit of data storage in the execution environment large enough to hold an object that may
680 have one of two values
682 NOTE It need not be possible to express the address of each individual bit of an object.
685 <h3><a name="3.6" href="#3.6">3.6</a></h3>
688 addressable unit of data storage large enough to hold any member of the basic character
689 set of the execution environment
691 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
694 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
695 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
699 <h3><a name="3.7" href="#3.7">3.7</a></h3>
701 <b> character</b><br>
702 <abstract> member of a set of elements used for the organization, control, or
703 representation of data
705 <h4><a name="3.7.1" href="#3.7.1">3.7.1</a></h4>
707 <b> character</b><br>
708 single-byte character
709 <C> bit representation that fits in a byte
712 <h4><a name="3.7.2" href="#3.7.2">3.7.2</a></h4>
714 <b> multibyte character</b><br>
715 sequence of one or more bytes representing a member of the extended character set of
716 either the source or the execution environment
718 NOTE The extended character set is a superset of the basic character set.
721 <h4><a name="3.7.3" href="#3.7.3">3.7.3</a></h4>
723 <b> wide character</b><br>
724 bit representation that fits in an object of type wchar_t, capable of representing any
725 character in the current locale
727 <h3><a name="3.8" href="#3.8">3.8</a></h3>
729 <b> constraint</b><br>
730 restriction, either syntactic or semantic, by which the exposition of language elements is
733 <h3><a name="3.9" href="#3.9">3.9</a></h3>
735 <b> correctly rounded result</b><br>
736 representation in the result format that is nearest in value, subject to the current rounding
737 mode, to what the result would be given unlimited range and precision
739 <h3><a name="3.10" href="#3.10">3.10</a></h3>
741 <b> diagnostic message</b><br>
742 message belonging to an implementation-defined subset of the implementation's message
745 <h3><a name="3.11" href="#3.11">3.11</a></h3>
747 <b> forward reference</b><br>
748 reference to a later subclause of this International Standard that contains additional
749 information relevant to this subclause
751 <h3><a name="3.12" href="#3.12">3.12</a></h3>
753 <b> implementation</b><br>
754 particular set of software, running in a particular translation environment under particular
755 control options, that performs translation of programs for, and supports execution of
756 functions in, a particular execution environment
758 <h3><a name="3.13" href="#3.13">3.13</a></h3>
760 <b> implementation limit</b><br>
761 restriction imposed upon programs by the implementation
763 <h3><a name="3.14" href="#3.14">3.14</a></h3>
766 region of data storage in the execution environment, the contents of which can represent
770 NOTE When referenced, an object may be interpreted as having a particular type; see <a href="#6.3.2.1">6.3.2.1</a>.
773 <h3><a name="3.15" href="#3.15">3.15</a></h3>
775 <b> parameter</b><br>
777 formal argument (deprecated)
778 object declared as part of a function declaration or definition that acquires a value on
779 entry to the function, or an identifier from the comma-separated list bounded by the
780 parentheses immediately following the macro name in a function-like macro definition
782 <h3><a name="3.16" href="#3.16">3.16</a></h3>
784 <b> recommended practice</b><br>
785 specification that is strongly recommended as being in keeping with the intent of the
786 standard, but that may be impractical for some implementations
788 <h3><a name="3.17" href="#3.17">3.17</a></h3>
791 precise meaning of the contents of an object when interpreted as having a specific type
793 <h4><a name="3.17.1" href="#3.17.1">3.17.1</a></h4>
795 <b> implementation-defined value</b><br>
796 unspecified value where each implementation documents how the choice is made
798 <h4><a name="3.17.2" href="#3.17.2">3.17.2</a></h4>
800 <b> indeterminate value</b><br>
801 either an unspecified value or a trap representation
803 <h4><a name="3.17.3" href="#3.17.3">3.17.3</a></h4>
805 <b> unspecified value</b><br>
806 valid value of the relevant type where this International Standard imposes no
807 requirements on which value is chosen in any instance
809 NOTE An unspecified value cannot be a trap representation.
812 <h3><a name="3.18" href="#3.18">3.18</a></h3>
815 ceiling of x: the least integer greater than or equal to x
817 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
820 <h3><a name="3.19" href="#3.19">3.19</a></h3>
823 floor of x: the greatest integer less than or equal to x
825 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
828 <h2><a name="4" href="#4">4. Conformance</a></h2>
830 In this International Standard, ''shall'' is to be interpreted as a requirement on an
831 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
834 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated, the
835 behavior is undefined. Undefined behavior is otherwise indicated in this International
836 Standard by the words ''undefined behavior'' or by the omission of any explicit definition
837 of behavior. There is no difference in emphasis among these three; they all describe
838 ''behavior that is undefined''.
840 A program that is correct in all other aspects, operating on correct data, containing
841 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
843 The implementation shall not successfully translate a preprocessing translation unit
844 containing a #error preprocessing directive unless it is part of a group skipped by
845 conditional inclusion.
847 A strictly conforming program shall use only those features of the language and library
848 specified in this International Standard.<sup><a href="#note2"><b>2)</b></a></sup> It shall not produce output dependent on any
849 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
850 minimum implementation limit.
852 The two forms of conforming implementation are hosted and freestanding. A conforming
853 hosted implementation shall accept any strictly conforming program. A conforming
854 freestanding implementation shall accept any strictly conforming program that does not
855 use complex types and in which the use of the features specified in the library clause
856 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
857 <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdarg.h></a>, <a href="#7.16"><stdbool.h></a>, <a href="#7.17"><stddef.h></a>, and
858 <a href="#7.18"><stdint.h></a>. A conforming implementation may have extensions (including additional
859 library functions), provided they do not alter the behavior of any strictly conforming
860 program.<sup><a href="#note3"><b>3)</b></a></sup>
866 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note4"><b>4)</b></a></sup>
868 An implementation shall be accompanied by a document that defines all implementation-
869 defined and locale-specific characteristics and all extensions.
870 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
871 characteristics of floating types <a href="#7.7"><float.h></a> (<a href="#7.7">7.7</a>), alternative spellings <a href="#7.9"><iso646.h></a>
872 (<a href="#7.9">7.9</a>), sizes of integer types <a href="#7.10"><limits.h></a> (<a href="#7.10">7.10</a>), variable arguments <a href="#7.15"><stdarg.h></a>
873 (<a href="#7.15">7.15</a>), boolean type and values <a href="#7.16"><stdbool.h></a> (<a href="#7.16">7.16</a>), common definitions
874 <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
882 <p><small><a name="note2" href="#note2">2)</a> A strictly conforming program can use conditional features (such as those in <a href="#F">annex F</a>) provided the
883 use is guarded by a #ifdef directive with the appropriate macro. For example:
886 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
888 fesetround(FE_UPWARD);
893 <p><small><a name="note3" href="#note3">3)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
894 reserved in this International Standard.
896 <p><small><a name="note4" href="#note4">4)</a> Strictly conforming programs are intended to be maximally portable among conforming
897 implementations. Conforming programs may depend upon nonportable features of a conforming
901 <h2><a name="5" href="#5">5. Environment</a></h2>
903 An implementation translates C source files and executes C programs in two data-
904 processing-system environments, which will be called the translation environment and
905 the execution environment in this International Standard. Their characteristics define and
906 constrain the results of executing conforming C programs constructed according to the
907 syntactic and semantic rules for conforming implementations.
908 <p><b> Forward references</b>: In this clause, only a few of many possible forward references
911 <h3><a name="5.1" href="#5.1">5.1 Conceptual models</a></h3>
913 <h4><a name="5.1.1" href="#5.1.1">5.1.1 Translation environment</a></h4>
915 <h5><a name="5.1.1.1" href="#5.1.1.1">5.1.1.1 Program structure</a></h5>
917 A C program need not all be translated at the same time. The text of the program is kept
918 in units called source files, (or preprocessing files) in this International Standard. A
919 source file together with all the headers and source files included via the preprocessing
920 directive #include is known as a preprocessing translation unit. After preprocessing, a
921 preprocessing translation unit is called a translation unit. Previously translated translation
922 units may be preserved individually or in libraries. The separate translation units of a
923 program communicate by (for example) calls to functions whose identifiers have external
924 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
925 of data files. Translation units may be separately translated and then later linked to
926 produce an executable program.
927 <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>),
928 preprocessing directives (<a href="#6.10">6.10</a>).
930 <h5><a name="5.1.1.2" href="#5.1.1.2">5.1.1.2 Translation phases</a></h5>
932 The precedence among the syntax rules of translation is specified by the following
933 phases.<sup><a href="#note5"><b>5)</b></a></sup>
935 <li> Physical source file multibyte characters are mapped, in an implementation-
936 defined manner, to the source character set (introducing new-line characters for
937 end-of-line indicators) if necessary. Trigraph sequences are replaced by
938 corresponding single-character internal representations.
943 <li> Each instance of a backslash character (\) immediately followed by a new-line
944 character is deleted, splicing physical source lines to form logical source lines.
945 Only the last backslash on any physical source line shall be eligible for being part
946 of such a splice. A source file that is not empty shall end in a new-line character,
947 which shall not be immediately preceded by a backslash character before any such
948 splicing takes place.
949 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note6"><b>6)</b></a></sup> and sequences of
950 white-space characters (including comments). A source file shall not end in a
951 partial preprocessing token or in a partial comment. Each comment is replaced by
952 one space character. New-line characters are retained. Whether each nonempty
953 sequence of white-space characters other than new-line is retained or replaced by
954 one space character is implementation-defined.
955 <li> Preprocessing directives are executed, macro invocations are expanded, and
956 _Pragma unary operator expressions are executed. If a character sequence that
957 matches the syntax of a universal character name is produced by token
958 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
959 directive causes the named header or source file to be processed from phase 1
960 through phase 4, recursively. All preprocessing directives are then deleted.
961 <li> Each source character set member and escape sequence in character constants and
962 string literals is converted to the corresponding member of the execution character
963 set; if there is no corresponding member, it is converted to an implementation-
964 defined member other than the null (wide) character.<sup><a href="#note7"><b>7)</b></a></sup>
965 <li> Adjacent string literal tokens are concatenated.
966 <li> White-space characters separating tokens are no longer significant. Each
967 preprocessing token is converted into a token. The resulting tokens are
968 syntactically and semantically analyzed and translated as a translation unit.
969 <li> All external object and function references are resolved. Library components are
970 linked to satisfy external references to functions and objects not defined in the
971 current translation. All such translator output is collected into a program image
972 which contains information needed for execution in its execution environment.
974 <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>),
975 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>).
982 <p><small><a name="note5" href="#note5">5)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
983 together in practice. Source files, translation units, and translated translation units need not
984 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
985 and any external representation. The description is conceptual only, and does not specify any
986 particular implementation.
988 <p><small><a name="note6" href="#note6">6)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
989 context-dependent. For example, see the handling of < within a #include preprocessing directive.
991 <p><small><a name="note7" href="#note7">7)</a> An implementation need not convert all non-corresponding source characters to the same execution
995 <h5><a name="5.1.1.3" href="#5.1.1.3">5.1.1.3 Diagnostics</a></h5>
997 A conforming implementation shall produce at least one diagnostic message (identified in
998 an implementation-defined manner) if a preprocessing translation unit or translation unit
999 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1000 specified as undefined or implementation-defined. Diagnostic messages need not be
1001 produced in other circumstances.<sup><a href="#note8"><b>8)</b></a></sup>
1003 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1007 because in those cases where wording in this International Standard describes the behavior for a construct
1008 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1012 <p><small><a name="note8" href="#note8">8)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1013 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1014 valid program is still correctly translated. It may also successfully translate an invalid program.
1017 <h4><a name="5.1.2" href="#5.1.2">5.1.2 Execution environments</a></h4>
1019 Two execution environments are defined: freestanding and hosted. In both cases,
1020 program startup occurs when a designated C function is called by the execution
1021 environment. All objects with static storage duration shall be initialized (set to their
1022 initial values) before program startup. The manner and timing of such initialization are
1023 otherwise unspecified. Program termination returns control to the execution
1025 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.8">6.7.8</a>).
1027 <h5><a name="5.1.2.1" href="#5.1.2.1">5.1.2.1 Freestanding environment</a></h5>
1029 In a freestanding environment (in which C program execution may take place without any
1030 benefit of an operating system), the name and type of the function called at program
1031 startup are implementation-defined. Any library facilities available to a freestanding
1032 program, other than the minimal set required by clause 4, are implementation-defined.
1034 The effect of program termination in a freestanding environment is implementation-
1037 <h5><a name="5.1.2.2" href="#5.1.2.2">5.1.2.2 Hosted environment</a></h5>
1039 A hosted environment need not be provided, but shall conform to the following
1040 specifications if present.
1047 <h5><a name="5.1.2.2.1" href="#5.1.2.2.1">5.1.2.2.1 Program startup</a></h5>
1049 The function called at program startup is named main. The implementation declares no
1050 prototype for this function. It shall be defined with a return type of int and with no
1053 int main(void) { /* ... */ }</pre>
1054 or with two parameters (referred to here as argc and argv, though any names may be
1055 used, as they are local to the function in which they are declared):
1057 int main(int argc, char *argv[]) { /* ... */ }</pre>
1058 or equivalent;<sup><a href="#note9"><b>9)</b></a></sup> or in some other implementation-defined manner.
1060 If they are declared, the parameters to the main function shall obey the following
1063 <li> The value of argc shall be nonnegative.
1064 <li> argv[argc] shall be a null pointer.
1065 <li> If the value of argc is greater than zero, the array members argv[0] through
1066 argv[argc-1] inclusive shall contain pointers to strings, which are given
1067 implementation-defined values by the host environment prior to program startup. The
1068 intent is to supply to the program information determined prior to program startup
1069 from elsewhere in the hosted environment. If the host environment is not capable of
1070 supplying strings with letters in both uppercase and lowercase, the implementation
1071 shall ensure that the strings are received in lowercase.
1072 <li> If the value of argc is greater than zero, the string pointed to by argv[0]
1073 represents the program name; argv[0][0] shall be the null character if the
1074 program name is not available from the host environment. If the value of argc is
1075 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1076 represent the program parameters.
1077 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1078 be modifiable by the program, and retain their last-stored values between program
1079 startup and program termination.
1083 <p><small><a name="note9" href="#note9">9)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1084 char ** argv, and so on.
1087 <h5><a name="5.1.2.2.2" href="#5.1.2.2.2">5.1.2.2.2 Program execution</a></h5>
1089 In a hosted environment, a program may use all the functions, macros, type definitions,
1090 and objects described in the library clause (clause 7).
1096 <h5><a name="5.1.2.2.3" href="#5.1.2.2.3">5.1.2.2.3 Program termination</a></h5>
1098 If the return type of the main function is a type compatible with int, a return from the
1099 initial call to the main function is equivalent to calling the exit function with the value
1100 returned by the main function as its argument;<sup><a href="#note10"><b>10)</b></a></sup> reaching the } that terminates the
1101 main function returns a value of 0. If the return type is not compatible with int, the
1102 termination status returned to the host environment is unspecified.
1103 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
1106 <p><small><a name="note10" href="#note10">10)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1107 will have ended in the former case, even where they would not have in the latter.
1110 <h5><a name="5.1.2.3" href="#5.1.2.3">5.1.2.3 Program execution</a></h5>
1112 The semantic descriptions in this International Standard describe the behavior of an
1113 abstract machine in which issues of optimization are irrelevant.
1115 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1116 that does any of those operations are all side effects,<sup><a href="#note11"><b>11)</b></a></sup> which are changes in the state of
1117 the execution environment. Evaluation of an expression may produce side effects. At
1118 certain specified points in the execution sequence called sequence points, all side effects
1119 of previous evaluations shall be complete and no side effects of subsequent evaluations
1120 shall have taken place. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1122 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1123 actual implementation need not evaluate part of an expression if it can deduce that its
1124 value is not used and that no needed side effects are produced (including any caused by
1125 calling a function or accessing a volatile object).
1127 When the processing of the abstract machine is interrupted by receipt of a signal, only the
1128 values of objects as of the previous sequence point may be relied on. Objects that may be
1129 modified between the previous sequence point and the next sequence point need not have
1130 received their correct values yet.
1132 The least requirements on a conforming implementation are:
1134 <li> At sequence points, volatile objects are stable in the sense that previous accesses are
1135 complete and subsequent accesses have not yet occurred.
1141 <li> At program termination, all data written into files shall be identical to the result that
1142 execution of the program according to the abstract semantics would have produced.
1143 <li> The input and output dynamics of interactive devices shall take place as specified in
1144 <a href="#7.19.3">7.19.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1145 appear as soon as possible, to ensure that prompting messages actually appear prior to
1146 a program waiting for input.
1149 What constitutes an interactive device is implementation-defined.
1151 More stringent correspondences between abstract and actual semantics may be defined by
1152 each implementation.
1154 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1155 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1156 abstract semantics. The keyword volatile would then be redundant.
1158 Alternatively, an implementation might perform various optimizations within each translation unit, such
1159 that the actual semantics would agree with the abstract semantics only when making function calls across
1160 translation unit boundaries. In such an implementation, at the time of each function entry and function
1161 return where the calling function and the called function are in different translation units, the values of all
1162 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1163 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1164 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1165 type of implementation, objects referred to by interrupt service routines activated by the signal function
1166 would require explicit specification of volatile storage, as well as other implementation-defined
1170 EXAMPLE 2 In executing the fragment
1175 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1176 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1177 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1178 produce the same result, possibly omitting the promotions.
1181 EXAMPLE 3 Similarly, in the fragment
1187 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1188 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1189 were replaced by the constant 2.0, which has type double).
1192 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1193 semantics. Values are independent of whether they are represented in a register or in memory. For
1194 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1195 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1196 perform their specified conversion. For the fragment
1200 d1 = f = expression;
1201 d2 = (float) expression;</pre>
1202 the values assigned to d1 and d2 are required to have been converted to float.
1205 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1206 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1207 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1208 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1209 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1210 numbers are often not valid (see <a href="#F.8">F.8</a>).
1214 x = (x * y) * z; // not equivalent to x *= y * z;
1215 z = (x - y) + y ; // not equivalent to z = x;
1216 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1217 y = x / 5.0; // not equivalent to y = x * 0.2;</pre>
1220 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1224 a = a + 32760 + b + 5;</pre>
1225 the expression statement behaves exactly the same as
1227 a = (((a + 32760) + b) + 5);</pre>
1228 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1229 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1230 which overflows produce an explicit trap and in which the range of values representable by an int is
1231 [-32768, +32767], the implementation cannot rewrite this expression as
1233 a = ((a + b) + 32765);</pre>
1234 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1235 while the original expression would not; nor can the expression be rewritten either as
1237 a = ((a + 32765) + b);</pre>
1240 a = (a + (b + 32765));</pre>
1241 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1242 in which overflow silently generates some value and where positive and negative overflows cancel, the
1243 above expression statement can be rewritten by the implementation in any of the above ways because the
1244 same result will occur.
1247 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1250 #include <a href="#7.19"><stdio.h></a>
1254 sum = sum * 10 - '0' + (*p++ = getchar());</pre>
1255 the expression statement is grouped as if it were written as
1257 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));</pre>
1258 but the actual increment of p can occur at any time between the previous sequence point and the next
1259 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1262 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>), statements (<a href="#6.8">6.8</a>), the
1263 signal function (<a href="#7.14">7.14</a>), files (<a href="#7.19.3">7.19.3</a>).
1267 <p><small><a name="note11" href="#note11">11)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1268 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1269 values of floating-point operations. Implementations that support such floating-point state are
1270 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1271 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1272 effects matter, freeing the implementations in other cases.
1275 <h3><a name="5.2" href="#5.2">5.2 Environmental considerations</a></h3>
1277 <h4><a name="5.2.1" href="#5.2.1">5.2.1 Character sets</a></h4>
1279 Two sets of characters and their associated collating sequences shall be defined: the set in
1280 which source files are written (the source character set), and the set interpreted in the
1281 execution environment (the execution character set). Each set is further divided into a
1282 basic character set, whose contents are given by this subclause, and a set of zero or more
1283 locale-specific members (which are not members of the basic character set) called
1284 extended characters. The combined set is also called the extended character set. The
1285 values of the members of the execution character set are implementation-defined.
1287 In a character constant or string literal, members of the execution character set shall be
1288 represented by corresponding members of the source character set or by escape
1289 sequences consisting of the backslash \ followed by one or more characters. A byte with
1290 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1291 is used to terminate a character string.
1293 Both the basic source and basic execution character sets shall have the following
1294 members: the 26 uppercase letters of the Latin alphabet
1296 A B C D E F G H I J K L M
1297 N O P Q R S T U V W X Y Z</pre>
1298 the 26 lowercase letters of the Latin alphabet
1300 a b c d e f g h i j k l m
1301 n o p q r s t u v w x y z</pre>
1302 the 10 decimal digits
1304 0 1 2 3 4 5 6 7 8 9</pre>
1305 the following 29 graphic characters
1307 ! " # % & ' ( ) * + , - . / :
1308 ; < = > ? [ \ ] ^ _ { | } ~</pre>
1309 the space character, and control characters representing horizontal tab, vertical tab, and
1310 form feed. The representation of each member of the source and execution basic
1311 character sets shall fit in a byte. In both the source and execution basic character sets, the
1312 value of each character after 0 in the above list of decimal digits shall be one greater than
1313 the value of the previous. In source files, there shall be some way of indicating the end of
1314 each line of text; this International Standard treats such an end-of-line indicator as if it
1315 were a single new-line character. In the basic execution character set, there shall be
1316 control characters representing alert, backspace, carriage return, and new line. If any
1317 other characters are encountered in a source file (except in an identifier, a character
1318 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1320 converted to a token), the behavior is undefined.
1322 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1323 Standard the term does not include other characters that are letters in other alphabets.
1325 The universal character name construct provides a way to name other characters.
1326 <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>),
1327 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>).
1329 <h5><a name="5.2.1.1" href="#5.2.1.1">5.2.1.1 Trigraph sequences</a></h5>
1331 Before any other processing takes place, each occurrence of one of the following
1332 sequences of three characters (called trigraph sequences<sup><a href="#note12"><b>12)</b></a></sup>) is replaced with the
1333 corresponding single character.
1336 ??( [ ??' ^ ??> }
1337 ??/ \ ??< { ??- ~</pre>
1338 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1339 above is not changed.
1343 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)</pre>
1346 #define arraycheck(a, b) a[b] || b[a]</pre>
1349 EXAMPLE 2 The following source line
1351 printf("Eh???/n");</pre>
1352 becomes (after replacement of the trigraph sequence ??/)
1354 printf("Eh?\n");</pre>
1358 <p><small><a name="note12" href="#note12">12)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1359 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1362 <h5><a name="5.2.1.2" href="#5.2.1.2">5.2.1.2 Multibyte characters</a></h5>
1364 The source character set may contain multibyte characters, used to represent members of
1365 the extended character set. The execution character set may also contain multibyte
1366 characters, which need not have the same encoding as for the source character set. For
1367 both character sets, the following shall hold:
1369 <li> The basic character set shall be present and each character shall be encoded as a
1371 <li> The presence, meaning, and representation of any additional members is locale-
1375 <li> A multibyte character set may have a state-dependent encoding, wherein each
1376 sequence of multibyte characters begins in an initial shift state and enters other
1377 locale-specific shift states when specific multibyte characters are encountered in the
1378 sequence. While in the initial shift state, all single-byte characters retain their usual
1379 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1380 in the sequence is a function of the current shift state.
1381 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1382 state. Such a byte shall not occur as part of any other multibyte character.
1385 For source files, the following shall hold:
1387 <li> An identifier, comment, string literal, character constant, or header name shall begin
1388 and end in the initial shift state.
1389 <li> An identifier, comment, string literal, character constant, or header name shall consist
1390 of a sequence of valid multibyte characters.
1393 <h4><a name="5.2.2" href="#5.2.2">5.2.2 Character display semantics</a></h4>
1395 The active position is that location on a display device where the next character output by
1396 the fputc function would appear. The intent of writing a printing character (as defined
1397 by the isprint function) to a display device is to display a graphic representation of
1398 that character at the active position and then advance the active position to the next
1399 position on the current line. The direction of writing is locale-specific. If the active
1400 position is at the final position of a line (if there is one), the behavior of the display device
1403 Alphabetic escape sequences representing nongraphic characters in the execution
1404 character set are intended to produce actions on display devices as follows:
1406 <dt> \a <dd>(alert) Produces an audible or visible alert without changing the active position.
1407 <dt> \b <dd>(backspace) Moves the active position to the previous position on the current line. If
1408 the active position is at the initial position of a line, the behavior of the display
1409 device is unspecified.
1410 <dt> \f <dd>( form feed) Moves the active position to the initial position at the start of the next
1412 <dt> \n <dd>(new line) Moves the active position to the initial position of the next line.
1413 <dt> \r <dd>(carriage return) Moves the active position to the initial position of the current line.
1414 <dt> \t <dd>(horizontal tab) Moves the active position to the next horizontal tabulation position
1415 on the current line. If the active position is at or past the last defined horizontal
1416 tabulation position, the behavior of the display device is unspecified.
1417 <dt> \v <dd>(vertical tab) Moves the active position to the initial position of the next vertical
1419 tabulation position. If the active position is at or past the last defined vertical
1420 tabulation position, the behavior of the display device is unspecified.
1423 Each of these escape sequences shall produce a unique implementation-defined value
1424 which can be stored in a single char object. The external representations in a text file
1425 need not be identical to the internal representations, and are outside the scope of this
1426 International Standard.
1427 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>).
1429 <h4><a name="5.2.3" href="#5.2.3">5.2.3 Signals and interrupts</a></h4>
1431 Functions shall be implemented such that they may be interrupted at any time by a signal,
1432 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1433 invocations' control flow (after the interruption), function return values, or objects with
1434 automatic storage duration. All such objects shall be maintained outside the function
1435 image (the instructions that compose the executable representation of a function) on a
1436 per-invocation basis.
1438 <h4><a name="5.2.4" href="#5.2.4">5.2.4 Environmental limits</a></h4>
1440 Both the translation and execution environments constrain the implementation of
1441 language translators and libraries. The following summarizes the language-related
1442 environmental limits on a conforming implementation; the library-related limits are
1443 discussed in clause 7.
1445 <h5><a name="5.2.4.1" href="#5.2.4.1">5.2.4.1 Translation limits</a></h5>
1447 The implementation shall be able to translate and execute at least one program that
1448 contains at least one instance of every one of the following limits:<sup><a href="#note13"><b>13)</b></a></sup>
1450 <li> 127 nesting levels of blocks
1451 <li> 63 nesting levels of conditional inclusion
1452 <li> 12 pointer, array, and function declarators (in any combinations) modifying an
1453 arithmetic, structure, union, or incomplete type in a declaration
1454 <li> 63 nesting levels of parenthesized declarators within a full declarator
1455 <li> 63 nesting levels of parenthesized expressions within a full expression
1456 <li> 63 significant initial characters in an internal identifier or a macro name (each
1457 universal character name or extended source character is considered a single
1459 <li> 31 significant initial characters in an external identifier (each universal character name
1460 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
1464 universal character name specifying a short identifier of 00010000 or more is
1465 considered 10 characters, and each extended source character is considered the same
1466 number of characters as the corresponding universal character name, if any)<sup><a href="#note14"><b>14)</b></a></sup>
1467 <li> 4095 external identifiers in one translation unit
1468 <li> 511 identifiers with block scope declared in one block
1469 <li> 4095 macro identifiers simultaneously defined in one preprocessing translation unit
1470 <li> 127 parameters in one function definition
1471 <li> 127 arguments in one function call
1472 <li> 127 parameters in one macro definition
1473 <li> 127 arguments in one macro invocation
1474 <li> 4095 characters in a logical source line
1475 <li> 4095 characters in a character string literal or wide string literal (after concatenation)
1476 <li> 65535 bytes in an object (in a hosted environment only)
1477 <li> 15 nesting levels for #included files
1478 <li> 1023 case labels for a switch statement (excluding those for any nested switch
1480 <li> 1023 members in a single structure or union
1481 <li> 1023 enumeration constants in a single enumeration
1482 <li> 63 levels of nested structure or union definitions in a single struct-declaration-list
1486 <p><small><a name="note13" href="#note13">13)</a> Implementations should avoid imposing fixed translation limits whenever possible.
1488 <p><small><a name="note14" href="#note14">14)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1491 <h5><a name="5.2.4.2" href="#5.2.4.2">5.2.4.2 Numerical limits</a></h5>
1493 An implementation is required to document all the limits specified in this subclause,
1494 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1495 specified in <a href="#7.18"><stdint.h></a>.
1496 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
1498 <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>
1500 The values given below shall be replaced by constant expressions suitable for use in #if
1501 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1502 following shall be replaced by expressions that have the same type as would an
1503 expression that is an object of the corresponding type converted according to the integer
1504 promotions. Their implementation-defined values shall be equal or greater in magnitude
1508 (absolute value) to those shown, with the same sign.
1510 <li> number of bits for smallest object that is not a bit-field (byte)
1511 <pre> CHAR_BIT 8</pre>
1512 <li> minimum value for an object of type signed char
1513 <pre> SCHAR_MIN -127 // -(2<sup>7</sup> - 1)</pre>
1514 <li> maximum value for an object of type signed char
1515 <pre> SCHAR_MAX +127 // 2<sup>7</sup> - 1</pre>
1516 <li> maximum value for an object of type unsigned char
1517 <pre> UCHAR_MAX 255 // 2<sup>8</sup> - 1</pre>
1518 <li> minimum value for an object of type char
1519 <pre> CHAR_MIN see below</pre>
1520 <li> maximum value for an object of type char
1521 <pre> CHAR_MAX see below</pre>
1522 <li> maximum number of bytes in a multibyte character, for any supported locale
1523 <pre> MB_LEN_MAX 1</pre>
1524 <li> minimum value for an object of type short int
1525 <pre> SHRT_MIN -32767 // -(2<sup>15</sup> - 1)</pre>
1526 <li> maximum value for an object of type short int
1527 <pre> SHRT_MAX +32767 // 2<sup>15</sup> - 1</pre>
1528 <li> maximum value for an object of type unsigned short int
1529 <pre> USHRT_MAX 65535 // 2<sup>16</sup> - 1</pre>
1530 <li> minimum value for an object of type int
1531 <pre> INT_MIN -32767 // -(2<sup>15</sup> - 1)</pre>
1532 <li> maximum value for an object of type int
1533 <pre> INT_MAX +32767 // 2<sup>15</sup> - 1</pre>
1534 <li> maximum value for an object of type unsigned int
1535 <pre> UINT_MAX 65535 // 2<sup>16</sup> - 1</pre>
1536 <li> minimum value for an object of type long int
1537 <pre> LONG_MIN -2147483647 // -(2<sup>31</sup> - 1)</pre>
1538 <li> maximum value for an object of type long int
1539 <pre> LONG_MAX +2147483647 // 2<sup>31</sup> - 1</pre>
1540 <li> maximum value for an object of type unsigned long int
1541 <pre> ULONG_MAX 4294967295 // 2<sup>32</sup> - 1</pre>
1543 <li> minimum value for an object of type long long int
1544 <pre> LLONG_MIN -9223372036854775807 // -(2<sup>63</sup> - 1)</pre>
1545 <li> maximum value for an object of type long long int
1546 <pre> LLONG_MAX +9223372036854775807 // 2<sup>63</sup> - 1</pre>
1547 <li> maximum value for an object of type unsigned long long int
1548 <pre> ULLONG_MAX 18446744073709551615 // 2<sup>64</sup> - 1</pre>
1551 If the value of an object of type char is treated as a signed integer when used in an
1552 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1553 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1554 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1555 UCHAR_MAX.<sup><a href="#note15"><b>15)</b></a></sup> The value UCHAR_MAX shall equal 2<sup>CHAR_BIT</sup> - 1.
1556 <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>).
1559 <p><small><a name="note15" href="#note15">15)</a> See <a href="#6.2.5">6.2.5</a>.
1562 <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>
1564 The characteristics of floating types are defined in terms of a model that describes a
1565 representation of floating-point numbers and values that provide information about an
1566 implementation's floating-point arithmetic.<sup><a href="#note16"><b>16)</b></a></sup> The following parameters are used to
1567 define the model for each floating-point type:
1571 b base or radix of exponent representation (an integer > 1)
1572 e exponent (an integer between a minimum emin and a maximum emax )
1573 p precision (the number of base-b digits in the significand)
1574 f<sub>k</sub> nonnegative integers less than b (the significand digits)</pre>
1575 A floating-point number (x) is defined by the following model:
1578 x = s b<sup>e</sup> (Sum) f<sub>k</sub> b<sup>-k</sup> , emin <= e <= emax
1582 In addition to normalized floating-point numbers ( f<sub>1</sub> > 0 if x != 0), floating types may be
1583 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1584 numbers (x != 0, e = emin , f<sub>1</sub> = 0) and unnormalized floating-point numbers (x != 0,
1585 e > emin , f<sub>1</sub> = 0), and values that are not floating-point numbers, such as infinities and
1586 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1587 through almost every arithmetic operation without raising a floating-point exception; a
1588 signaling NaN generally raises a floating-point exception when occurring as an
1592 arithmetic operand.<sup><a href="#note17"><b>17)</b></a></sup>
1594 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1595 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1596 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1597 any requirement to set the sign shall be ignored.
1599 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1600 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1601 defined, as is the accuracy of the conversion between floating-point internal
1602 representations and string representations performed by the library functions in
1603 <a href="#7.19"><stdio.h></a>, <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a>. The implementation may state that the
1604 accuracy is unknown.
1606 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1607 expressions suitable for use in #if preprocessing directives; all floating values shall be
1608 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1609 and FLT_ROUNDS have separate names for all three floating-point types. The floating-point
1610 model representation is provided for all values except FLT_EVAL_METHOD and
1613 The rounding mode for floating-point addition is characterized by the implementation-
1614 defined value of FLT_ROUNDS:<sup><a href="#note18"><b>18)</b></a></sup>
1619 2 toward positive infinity
1620 3 toward negative infinity</pre>
1621 All other values for FLT_ROUNDS characterize implementation-defined rounding
1624 Except for assignment and cast (which remove all extra range and precision), the values
1625 of operations with floating operands and values subject to the usual arithmetic
1626 conversions and of floating constants are evaluated to a format whose range and precision
1627 may be greater than required by the type. The use of evaluation formats is characterized
1628 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note19"><b>19)</b></a></sup>
1635 0 evaluate all operations and constants just to the range and precision of the
1637 1 evaluate operations and constants of type float and double to the
1638 range and precision of the double type, evaluate long double
1639 operations and constants to the range and precision of the long double
1641 2 evaluate all operations and constants to the range and precision of the
1642 long double type.</pre>
1643 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1646 The values given in the following list shall be replaced by constant expressions with
1647 implementation-defined values that are greater or equal in magnitude (absolute value) to
1648 those shown, with the same sign:
1650 <li> radix of exponent representation, b
1651 <pre> FLT_RADIX 2</pre>
1652 <li> number of base-FLT_RADIX digits in the floating-point significand, p
1656 <li> number of decimal digits, n, such that any floating-point number in the widest
1657 supported floating type with pmax radix b digits can be rounded to a floating-point
1658 number with n decimal digits and back again without change to the value,
1660 { pmax log10 b if b is a power of 10
1662 { [^1 + pmax log10 b^] otherwise</pre>
1663 <pre> DECIMAL_DIG 10</pre>
1664 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
1665 can be rounded into a floating-point number with p radix b digits and back again
1666 without change to the q decimal digits,
1673 { p log10 b if b is a power of 10
1675 { [_( p - 1) log10 b_] otherwise</pre>
1679 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
1680 a normalized floating-point number, emin
1684 <li> minimum negative integer such that 10 raised to that power is in the range of
1685 normalized floating-point numbers, [^log10 b<sup>emin -1</sup>^]
1686 <pre> FLT_MIN_10_EXP -37
1688 LDBL_MIN_10_EXP -37</pre>
1689 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
1690 representable finite floating-point number, emax
1694 <li> maximum integer such that 10 raised to that power is in the range of representable
1695 finite floating-point numbers, [_log10 ((1 - b<sup>-p</sup>)b<sup>emax</sup>)_]
1696 <pre> FLT_MAX_10_EXP +37
1698 LDBL_MAX_10_EXP +37</pre>
1701 The values given in the following list shall be replaced by constant expressions with
1702 implementation-defined values that are greater than or equal to those shown:
1704 <li> maximum representable finite floating-point number, (1 - b<sup>-p</sup>)b<sup>emax</sup>
1707 LDBL_MAX 1E+37</pre>
1710 The values given in the following list shall be replaced by constant expressions with
1711 implementation-defined (positive) values that are less than or equal to those shown:
1713 <li> the difference between 1 and the least value greater than 1 that is representable in the
1714 given floating point type, b<sup>1-p</sup>
1716 <pre> FLT_EPSILON 1E-5
1718 LDBL_EPSILON 1E-9</pre>
1719 <li> minimum normalized positive floating-point number, b<sup>emin -1</sup>
1722 LDBL_MIN 1E-37</pre>
1724 <h6> Recommended practice</h6>
1726 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1727 should be the identity function.
1729 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1730 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1734 x = s 16<sup>e</sup> (Sum) f<sub>k</sub> 16<sup>-k</sup> , -31 <= e <= +32
1740 FLT_EPSILON 9.53674316E-07F
1743 FLT_MIN 2.93873588E-39F
1746 FLT_MAX 3.40282347E+38F
1747 FLT_MAX_10_EXP +38</pre>
1750 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1751 single-precision and double-precision normalized numbers in IEC 60559,<sup><a href="#note20"><b>20)</b></a></sup> and the appropriate values in a
1752 <a href="#7.7"><float.h></a> header for types float and double:
1755 xf = s 2<sup>e</sup> (Sum) f<sub>k</sub> 2<sup>-k</sup> , -125 <= e <= +128
1760 xd = s 2<sup>e</sup> (Sum) f<sub>k</sub> 2<sup>-k</sup> , -1021 <= e <= +1024
1768 FLT_EPSILON 1.19209290E-07F // decimal constant
1769 FLT_EPSILON 0X1P-23F // hex constant</pre>
1776 FLT_MIN 1.17549435E-38F // decimal constant
1777 FLT_MIN 0X1P-126F // hex constant
1780 FLT_MAX 3.40282347E+38F // decimal constant
1781 FLT_MAX 0X1.fffffeP127F // hex constant
1784 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1785 DBL_EPSILON 0X1P-52 // hex constant
1788 DBL_MIN 2.2250738585072014E-308 // decimal constant
1789 DBL_MIN 0X1P-1022 // hex constant
1792 DBL_MAX 1.7976931348623157E+308 // decimal constant
1793 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1794 DBL_MAX_10_EXP +308</pre>
1795 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1796 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1797 precision), then DECIMAL_DIG would be 21.
1799 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1800 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.24"><wchar.h></a>
1801 (<a href="#7.24">7.24</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.20"><stdlib.h></a>
1802 (<a href="#7.20">7.20</a>), input/output <a href="#7.19"><stdio.h></a> (<a href="#7.19">7.19</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
1806 <p><small><a name="note16" href="#note16">16)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
1807 does not require the floating-point arithmetic of the implementation to be identical.
1809 <p><small><a name="note17" href="#note17">17)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1810 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
1813 <p><small><a name="note18" href="#note18">18)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1814 the function fesetround in <a href="#7.6"><fenv.h></a>.
1816 <p><small><a name="note19" href="#note19">19)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
1817 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1818 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1821 <p><small><a name="note20" href="#note20">20)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1822 limits are one less than shown here.
1825 <h2><a name="6" href="#6">6. Language</a></h2>
1827 <h3><a name="6.1" href="#6.1">6.1 Notation</a></h3>
1829 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1830 indicated by italic type, and literal words and character set members (terminals) by bold
1831 type. A colon (:) following a nonterminal introduces its definition. Alternative
1832 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1833 optional symbol is indicated by the subscript ''opt'', so that
1835 { expression<sub>opt</sub> }</pre>
1836 indicates an optional expression enclosed in braces.
1838 When syntactic categories are referred to in the main text, they are not italicized and
1839 words are separated by spaces instead of hyphens.
1841 A summary of the language syntax is given in <a href="#A">annex A</a>.
1843 <h3><a name="6.2" href="#6.2">6.2 Concepts</a></h3>
1845 <h4><a name="6.2.1" href="#6.2.1">6.2.1 Scopes of identifiers</a></h4>
1847 An identifier can denote an object; a function; a tag or a member of a structure, union, or
1848 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
1849 same identifier can denote different entities at different points in the program. A member
1850 of an enumeration is called an enumeration constant. Macro names and macro
1851 parameters are not considered further here, because prior to the semantic phase of
1852 program translation any occurrences of macro names in the source file are replaced by the
1853 preprocessing token sequences that constitute their macro definitions.
1855 For each different entity that an identifier designates, the identifier is visible (i.e., can be
1856 used) only within a region of program text called its scope. Different entities designated
1857 by the same identifier either have different scopes, or are in different name spaces. There
1858 are four kinds of scopes: function, file, block, and function prototype. (A function
1859 prototype is a declaration of a function that declares the types of its parameters.)
1861 A label name is the only kind of identifier that has function scope. It can be used (in a
1862 goto statement) anywhere in the function in which it appears, and is declared implicitly
1863 by its syntactic appearance (followed by a : and a statement).
1865 Every other identifier has scope determined by the placement of its declaration (in a
1866 declarator or type specifier). If the declarator or type specifier that declares the identifier
1867 appears outside of any block or list of parameters, the identifier has file scope, which
1868 terminates at the end of the translation unit. If the declarator or type specifier that
1869 declares the identifier appears inside a block or within the list of parameter declarations in
1870 a function definition, the identifier has block scope, which terminates at the end of the
1871 associated block. If the declarator or type specifier that declares the identifier appears
1873 within the list of parameter declarations in a function prototype (not part of a function
1874 definition), the identifier has function prototype scope, which terminates at the end of the
1875 function declarator. If an identifier designates two different entities in the same name
1876 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will be a
1877 strict subset of the scope of the other entity (the outer scope). Within the inner scope, the
1878 identifier designates the entity declared in the inner scope; the entity declared in the outer
1879 scope is hidden (and not visible) within the inner scope.
1881 Unless explicitly stated otherwise, where this International Standard uses the term
1882 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
1883 entity in the relevant name space whose declaration is visible at the point the identifier
1886 Two identifiers have the same scope if and only if their scopes terminate at the same
1889 Structure, union, and enumeration tags have scope that begins just after the appearance of
1890 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
1891 begins just after the appearance of its defining enumerator in an enumerator list. Any
1892 other identifier has scope that begins just after the completion of its declarator.
1893 <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
1894 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>),
1895 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
1897 <h4><a name="6.2.2" href="#6.2.2">6.2.2 Linkages of identifiers</a></h4>
1899 An identifier declared in different scopes or in the same scope more than once can be
1900 made to refer to the same object or function by a process called linkage.<sup><a href="#note21"><b>21)</b></a></sup> There are
1901 three kinds of linkage: external, internal, and none.
1903 In the set of translation units and libraries that constitutes an entire program, each
1904 declaration of a particular identifier with external linkage denotes the same object or
1905 function. Within one translation unit, each declaration of an identifier with internal
1906 linkage denotes the same object or function. Each declaration of an identifier with no
1907 linkage denotes a unique entity.
1909 If the declaration of a file scope identifier for an object or a function contains the storage-
1910 class specifier static, the identifier has internal linkage.<sup><a href="#note22"><b>22)</b></a></sup>
1912 For an identifier declared with the storage-class specifier extern in a scope in which a
1917 prior declaration of that identifier is visible,<sup><a href="#note23"><b>23)</b></a></sup> if the prior declaration specifies internal or
1918 external linkage, the linkage of the identifier at the later declaration is the same as the
1919 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
1920 declaration specifies no linkage, then the identifier has external linkage.
1922 If the declaration of an identifier for a function has no storage-class specifier, its linkage
1923 is determined exactly as if it were declared with the storage-class specifier extern. If
1924 the declaration of an identifier for an object has file scope and no storage-class specifier,
1925 its linkage is external.
1927 The following identifiers have no linkage: an identifier declared to be anything other than
1928 an object or a function; an identifier declared to be a function parameter; a block scope
1929 identifier for an object declared without the storage-class specifier extern.
1931 If, within a translation unit, the same identifier appears with both internal and external
1932 linkage, the behavior is undefined.
1933 <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>),
1934 statements (<a href="#6.8">6.8</a>).
1937 <p><small><a name="note21" href="#note21">21)</a> There is no linkage between different identifiers.
1939 <p><small><a name="note22" href="#note22">22)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
1940 <a href="#6.7.1">6.7.1</a>.
1942 <p><small><a name="note23" href="#note23">23)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
1945 <h4><a name="6.2.3" href="#6.2.3">6.2.3 Name spaces of identifiers</a></h4>
1947 If more than one declaration of a particular identifier is visible at any point in a
1948 translation unit, the syntactic context disambiguates uses that refer to different entities.
1949 Thus, there are separate name spaces for various categories of identifiers, as follows:
1951 <li> label names (disambiguated by the syntax of the label declaration and use);
1952 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note24"><b>24)</b></a></sup>
1953 of the keywords struct, union, or enum);
1954 <li> the members of structures or unions; each structure or union has a separate name
1955 space for its members (disambiguated by the type of the expression used to access the
1956 member via the . or -> operator);
1957 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
1958 enumeration constants).
1960 <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>),
1961 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
1962 (<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>).
1970 <p><small><a name="note24" href="#note24">24)</a> There is only one name space for tags even though three are possible.
1973 <h4><a name="6.2.4" href="#6.2.4">6.2.4 Storage durations of objects</a></h4>
1975 An object has a storage duration that determines its lifetime. There are three storage
1976 durations: static, automatic, and allocated. Allocated storage is described in <a href="#7.20.3">7.20.3</a>.
1978 The lifetime of an object is the portion of program execution during which storage is
1979 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note25"><b>25)</b></a></sup> and retains
1980 its last-stored value throughout its lifetime.<sup><a href="#note26"><b>26)</b></a></sup> If an object is referred to outside of its
1981 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
1982 the object it points to reaches the end of its lifetime.
1984 An object whose identifier is declared with external or internal linkage, or with the
1985 storage-class specifier static has static storage duration. Its lifetime is the entire
1986 execution of the program and its stored value is initialized only once, prior to program
1989 An object whose identifier is declared with no linkage and without the storage-class
1990 specifier static has automatic storage duration.
1992 For such an object that does not have a variable length array type, its lifetime extends
1993 from entry into the block with which it is associated until execution of that block ends in
1994 any way. (Entering an enclosed block or calling a function suspends, but does not end,
1995 execution of the current block.) If the block is entered recursively, a new instance of the
1996 object is created each time. The initial value of the object is indeterminate. If an
1997 initialization is specified for the object, it is performed each time the declaration is
1998 reached in the execution of the block; otherwise, the value becomes indeterminate each
1999 time the declaration is reached.
2001 For such an object that does have a variable length array type, its lifetime extends from
2002 the declaration of the object until execution of the program leaves the scope of the
2003 declaration.<sup><a href="#note27"><b>27)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2004 each time. The initial value of the object is indeterminate.
2005 <p><b> Forward references</b>: statements (<a href="#6.8">6.8</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), declarators (<a href="#6.7.5">6.7.5</a>), array
2006 declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
2014 <p><small><a name="note25" href="#note25">25)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2015 times will compare equal. The address may be different during two different executions of the same
2018 <p><small><a name="note26" href="#note26">26)</a> In the case of a volatile object, the last store need not be explicit in the program.
2020 <p><small><a name="note27" href="#note27">27)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2021 embedded block prior to the declaration, leaves the scope of the declaration.
2024 <h4><a name="6.2.5" href="#6.2.5">6.2.5 Types</a></h4>
2026 The meaning of a value stored in an object or returned by a function is determined by the
2027 type of the expression used to access it. (An identifier declared to be an object is the
2028 simplest such expression; the type is specified in the declaration of the identifier.) Types
2029 are partitioned into object types (types that fully describe objects), function types (types
2030 that describe functions), and incomplete types (types that describe objects but lack
2031 information needed to determine their sizes).
2033 An object declared as type _Bool is large enough to store the values 0 and 1.
2035 An object declared as type char is large enough to store any member of the basic
2036 execution character set. If a member of the basic execution character set is stored in a
2037 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2038 a char object, the resulting value is implementation-defined but shall be within the range
2039 of values that can be represented in that type.
2041 There are five standard signed integer types, designated as signed char, short
2042 int, int, long int, and long long int. (These and other types may be
2043 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2044 implementation-defined extended signed integer types.<sup><a href="#note28"><b>28)</b></a></sup> The standard and extended
2045 signed integer types are collectively called signed integer types.<sup><a href="#note29"><b>29)</b></a></sup>
2047 An object declared as type signed char occupies the same amount of storage as a
2048 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2049 architecture of the execution environment (large enough to contain any value in the range
2050 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2052 For each of the signed integer types, there is a corresponding (but different) unsigned
2053 integer type (designated with the keyword unsigned) that uses the same amount of
2054 storage (including sign information) and has the same alignment requirements. The type
2055 _Bool and the unsigned integer types that correspond to the standard signed integer
2056 types are the standard unsigned integer types. The unsigned integer types that
2057 correspond to the extended signed integer types are the extended unsigned integer types.
2058 The standard and extended unsigned integer types are collectively called unsigned integer
2059 types.<sup><a href="#note30"><b>30)</b></a></sup>
2065 The standard signed integer types and standard unsigned integer types are collectively
2066 called the standard integer types, the extended signed integer types and extended
2067 unsigned integer types are collectively called the extended integer types.
2069 For any two integer types with the same signedness and different integer conversion rank
2070 (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
2071 subrange of the values of the other type.
2073 The range of nonnegative values of a signed integer type is a subrange of the
2074 corresponding unsigned integer type, and the representation of the same value in each
2075 type is the same.<sup><a href="#note31"><b>31)</b></a></sup> A computation involving unsigned operands can never overflow,
2076 because a result that cannot be represented by the resulting unsigned integer type is
2077 reduced modulo the number that is one greater than the largest value that can be
2078 represented by the resulting type.
2080 There are three real floating types, designated as float, double, and long
2081 double.<sup><a href="#note32"><b>32)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2082 type double; the set of values of the type double is a subset of the set of values of the
2085 There are three complex types, designated as float _Complex, double
2086 _Complex, and long double _Complex.<sup><a href="#note33"><b>33)</b></a></sup> The real floating and complex types
2087 are collectively called the floating types.
2089 For each floating type there is a corresponding real type, which is always a real floating
2090 type. For real floating types, it is the same type. For complex types, it is the type given
2091 by deleting the keyword _Complex from the type name.
2093 Each complex type has the same representation and alignment requirements as an array
2094 type containing exactly two elements of the corresponding real type; the first element is
2095 equal to the real part, and the second element to the imaginary part, of the complex
2098 The type char, the signed and unsigned integer types, and the floating types are
2099 collectively called the basic types. Even if the implementation defines two or more basic
2100 types to have the same representation, they are nevertheless different types.<sup><a href="#note34"><b>34)</b></a></sup>
2104 The three types char, signed char, and unsigned char are collectively called
2105 the character types. The implementation shall define char to have the same range,
2106 representation, and behavior as either signed char or unsigned char.<sup><a href="#note35"><b>35)</b></a></sup>
2108 An enumeration comprises a set of named integer constant values. Each distinct
2109 enumeration constitutes a different enumerated type.
2111 The type char, the signed and unsigned integer types, and the enumerated types are
2112 collectively called integer types. The integer and real floating types are collectively called
2115 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2116 belongs to one type domain: the real type domain comprises the real types, the complex
2117 type domain comprises the complex types.
2119 The void type comprises an empty set of values; it is an incomplete type that cannot be
2122 Any number of derived types can be constructed from the object, function, and
2123 incomplete types, as follows:
2125 <li> An array type describes a contiguously allocated nonempty set of objects with a
2126 particular member object type, called the element type.<sup><a href="#note36"><b>36)</b></a></sup> Array types are
2127 characterized by their element type and by the number of elements in the array. An
2128 array type is said to be derived from its element type, and if its element type is T , the
2129 array type is sometimes called ''array of T ''. The construction of an array type from
2130 an element type is called ''array type derivation''.
2131 <li> A structure type describes a sequentially allocated nonempty set of member objects
2132 (and, in certain circumstances, an incomplete array), each of which has an optionally
2133 specified name and possibly distinct type.
2134 <li> A union type describes an overlapping nonempty set of member objects, each of
2135 which has an optionally specified name and possibly distinct type.
2136 <li> A function type describes a function with specified return type. A function type is
2137 characterized by its return type and the number and types of its parameters. A
2138 function type is said to be derived from its return type, and if its return type is T , the
2139 function type is sometimes called ''function returning T ''. The construction of a
2140 function type from a return type is called ''function type derivation''.
2145 <li> A pointer type may be derived from a function type, an object type, or an incomplete
2146 type, called the referenced type. A pointer type describes an object whose value
2147 provides a reference to an entity of the referenced type. A pointer type derived from
2148 the referenced type T is sometimes called ''pointer to T ''. The construction of a
2149 pointer type from a referenced type is called ''pointer type derivation''.
2151 These methods of constructing derived types can be applied recursively.
2153 Arithmetic types and pointer types are collectively called scalar types. Array and
2154 structure types are collectively called aggregate types.<sup><a href="#note37"><b>37)</b></a></sup>
2156 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2157 that type, by specifying the size in a later declaration (with internal or external linkage).
2158 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
2159 type. It is completed, for all declarations of that type, by declaring the same structure or
2160 union tag with its defining content later in the same scope.
2162 A type has known constant size if the type is not incomplete and is not a variable length
2165 Array, function, and pointer types are collectively called derived declarator types. A
2166 declarator type derivation from a type T is the construction of a derived declarator type
2167 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2170 A type is characterized by its type category, which is either the outermost derivation of a
2171 derived type (as noted above in the construction of derived types), or the type itself if the
2172 type consists of no derived types.
2174 Any type so far mentioned is an unqualified type. Each unqualified type has several
2175 qualified versions of its type,<sup><a href="#note38"><b>38)</b></a></sup> corresponding to the combinations of one, two, or all
2176 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2177 versions of a type are distinct types that belong to the same type category and have the
2178 same representation and alignment requirements.<sup><a href="#note39"><b>39)</b></a></sup> A derived type is not qualified by the
2179 qualifiers (if any) of the type from which it is derived.
2181 A pointer to void shall have the same representation and alignment requirements as a
2182 pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of
2183 compatible types shall have the same representation and alignment requirements. All
2187 pointers to structure types shall have the same representation and alignment requirements
2188 as each other. All pointers to union types shall have the same representation and
2189 alignment requirements as each other. Pointers to other types need not have the same
2190 representation or alignment requirements.
2192 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2193 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2194 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2195 qualified float'' and is a pointer to a qualified type.
2198 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2199 function returning struct tag''. The array has length five and the function has a single parameter of type
2200 float. Its type category is array.
2202 <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>).
2205 <p><small><a name="note28" href="#note28">28)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2206 described in <a href="#7.1.3">7.1.3</a>.
2208 <p><small><a name="note29" href="#note29">29)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2209 signed integer types.
2211 <p><small><a name="note30" href="#note30">30)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2212 unsigned integer types.
2214 <p><small><a name="note31" href="#note31">31)</a> The same representation and alignment requirements are meant to imply interchangeability as
2215 arguments to functions, return values from functions, and members of unions.
2217 <p><small><a name="note32" href="#note32">32)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2219 <p><small><a name="note33" href="#note33">33)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
2221 <p><small><a name="note34" href="#note34">34)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2222 any other) type; this does not violate the requirement that all basic types be different.
2223 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2224 described in <a href="#7.1.3">7.1.3</a>.
2226 <p><small><a name="note35" href="#note35">35)</a> CHAR_MIN, defined in <a href="#7.10"><limits.h></a>, will have one of the values 0 or SCHAR_MIN, and this can be
2227 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2228 other two and is not compatible with either.
2230 <p><small><a name="note36" href="#note36">36)</a> Since object types do not include incomplete types, an array of incomplete type cannot be constructed.
2232 <p><small><a name="note37" href="#note37">37)</a> Note that aggregate type does not include union type because an object with union type can only
2233 contain one member at a time.
2235 <p><small><a name="note38" href="#note38">38)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2237 <p><small><a name="note39" href="#note39">39)</a> The same representation and alignment requirements are meant to imply interchangeability as
2238 arguments to functions, return values from functions, and members of unions.
2241 <h4><a name="6.2.6" href="#6.2.6">6.2.6 Representations of types</a></h4>
2243 <h5><a name="6.2.6.1" href="#6.2.6.1">6.2.6.1 General</a></h5>
2245 The representations of all types are unspecified except as stated in this subclause.
2247 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2248 the number, order, and encoding of which are either explicitly specified or
2249 implementation-defined.
2251 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2252 represented using a pure binary notation.<sup><a href="#note40"><b>40)</b></a></sup>
2254 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2255 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2256 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2257 called the object representation of the value. Values stored in bit-fields consist of m bits,
2258 where m is the size specified for the bit-field. The object representation is the set of m
2259 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2260 than NaNs) with the same object representation compare equal, but values that compare
2261 equal may have different object representations.
2263 Certain object representations need not represent a value of the object type. If the stored
2264 value of an object has such a representation and is read by an lvalue expression that does
2265 not have character type, the behavior is undefined. If such a representation is produced
2266 by a side effect that modifies all or any part of the object by an lvalue expression that
2267 does not have character type, the behavior is undefined.<sup><a href="#note41"><b>41)</b></a></sup> Such a representation is called
2270 a trap representation.
2272 When a value is stored in an object of structure or union type, including in a member
2273 object, the bytes of the object representation that correspond to any padding bytes take
2274 unspecified values.<sup><a href="#note42"><b>42)</b></a></sup> The value of a structure or union object is never a trap
2275 representation, even though the value of a member of the structure or union object may be
2276 a trap representation.
2278 When a value is stored in a member of an object of union type, the bytes of the object
2279 representation that do not correspond to that member but do correspond to other members
2280 take unspecified values.
2282 Where an operator is applied to a value that has more than one object representation,
2283 which object representation is used shall not affect the value of the result.<sup><a href="#note43"><b>43)</b></a></sup> Where a
2284 value is stored in an object using a type that has more than one object representation for
2285 that value, it is unspecified which representation is used, but a trap representation shall
2287 <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
2288 designators (<a href="#6.3.2.1">6.3.2.1</a>).
2291 <p><small><a name="note40" href="#note40">40)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
2292 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2293 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2294 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2295 type unsigned char range from 0 to 2<sup>CHAR_BIT</sup>- 1.
2297 <p><small><a name="note41" href="#note41">41)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2298 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2300 <p><small><a name="note42" href="#note42">42)</a> Thus, for example, structure assignment need not copy any padding bits.
2302 <p><small><a name="note43" href="#note43">43)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
2303 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2304 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2305 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2306 on values of type T may distinguish between them.
2309 <h5><a name="6.2.6.2" href="#6.2.6.2">6.2.6.2 Integer types</a></h5>
2311 For unsigned integer types other than unsigned char, the bits of the object
2312 representation shall be divided into two groups: value bits and padding bits (there need
2313 not be any of the latter). If there are N value bits, each bit shall represent a different
2314 power of 2 between 1 and 2<sup>N-1</sup> , so that objects of that type shall be capable of
2315 representing values from 0 to 2<sup>N</sup> - 1 using a pure binary representation; this shall be
2316 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note44"><b>44)</b></a></sup>
2318 For signed integer types, the bits of the object representation shall be divided into three
2319 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2322 there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as
2323 the same bit in the object representation of the corresponding unsigned type (if there are
2324 M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit
2325 is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be
2326 modified in one of the following ways:
2328 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
2329 <li> the sign bit has the value -(2<sup>N</sup> ) (two's complement);
2330 <li> the sign bit has the value -(2<sup>N</sup> - 1) (ones' complement ).
2332 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2333 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2334 complement), is a trap representation or a normal value. In the case of sign and
2335 magnitude and ones' complement, if this representation is a normal value it is called a
2338 If the implementation supports negative zeros, they shall be generated only by:
2340 <li> the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
2341 <li> the +, -, *, /, and % operators where one argument is a negative zero and the result is
2343 <li> compound assignment operators based on the above cases.
2345 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2346 and whether a negative zero becomes a normal zero when stored in an object.
2348 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2349 and >> operators with arguments that would produce such a value is undefined.
2351 The values of any padding bits are unspecified.<sup><a href="#note45"><b>45)</b></a></sup> A valid (non-trap) object representation
2352 of a signed integer type where the sign bit is zero is a valid object representation of the
2353 corresponding unsigned type, and shall represent the same value. For any integer type,
2354 the object representation where all the bits are zero shall be a representation of the value
2357 The precision of an integer type is the number of bits it uses to represent values,
2358 excluding any sign and padding bits. The width of an integer type is the same but
2359 including any sign bit; thus for unsigned integer types the two values are the same, while
2363 for signed integer types the width is one greater than the precision.
2366 <p><small><a name="note44" href="#note44">44)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2367 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2368 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2369 with unsigned types. All other combinations of padding bits are alternative object representations of
2370 the value specified by the value bits.
2372 <p><small><a name="note45" href="#note45">45)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2373 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2374 representation other than as part of an exceptional condition such as an overflow. All other
2375 combinations of padding bits are alternative object representations of the value specified by the value
2379 <h4><a name="6.2.7" href="#6.2.7">6.2.7 Compatible type and composite type</a></h4>
2381 Two types have compatible type if their types are the same. Additional rules for
2382 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2383 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.5">6.7.5</a> for declarators.<sup><a href="#note46"><b>46)</b></a></sup> Moreover, two structure,
2384 union, or enumerated types declared in separate translation units are compatible if their
2385 tags and members satisfy the following requirements: If one is declared with a tag, the
2386 other shall be declared with the same tag. If both are complete types, then the following
2387 additional requirements apply: there shall be a one-to-one correspondence between their
2388 members such that each pair of corresponding members are declared with compatible
2389 types, and such that if one member of a corresponding pair is declared with a name, the
2390 other member is declared with the same name. For two structures, corresponding
2391 members shall be declared in the same order. For two structures or unions, corresponding
2392 bit-fields shall have the same widths. For two enumerations, corresponding members
2393 shall have the same values.
2395 All declarations that refer to the same object or function shall have compatible type;
2396 otherwise, the behavior is undefined.
2398 A composite type can be constructed from two types that are compatible; it is a type that
2399 is compatible with both of the two types and satisfies the following conditions:
2401 <li> If one type is an array of known constant size, the composite type is an array of that
2402 size; otherwise, if one type is a variable length array, the composite type is that type.
2403 <li> If only one type is a function type with a parameter type list (a function prototype),
2404 the composite type is a function prototype with the parameter type list.
2405 <li> If both types are function types with parameter type lists, the type of each parameter
2406 in the composite parameter type list is the composite type of the corresponding
2409 These rules apply recursively to the types from which the two types are derived.
2411 For an identifier with internal or external linkage declared in a scope in which a prior
2412 declaration of that identifier is visible,<sup><a href="#note47"><b>47)</b></a></sup> if the prior declaration specifies internal or
2413 external linkage, the type of the identifier at the later declaration becomes the composite
2421 EXAMPLE Given the following two file scope declarations:
2423 int f(int (*)(), double (*)[3]);
2424 int f(int (*)(char *), double (*)[]);</pre>
2425 The resulting composite type for the function is:
2428 int f(int (*)(char *), double (*)[3]);</pre>
2431 <p><small><a name="note46" href="#note46">46)</a> Two types need not be identical to be compatible.
2433 <p><small><a name="note47" href="#note47">47)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2436 <h3><a name="6.3" href="#6.3">6.3 Conversions</a></h3>
2438 Several operators convert operand values from one type to another automatically. This
2439 subclause specifies the result required from such an implicit conversion, as well as those
2440 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2441 the conversions performed by most ordinary operators; it is supplemented as required by
2442 the discussion of each operator in <a href="#6.5">6.5</a>.
2444 Conversion of an operand value to a compatible type causes no change to the value or the
2446 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>).
2448 <h4><a name="6.3.1" href="#6.3.1">6.3.1 Arithmetic operands</a></h4>
2450 <h5><a name="6.3.1.1" href="#6.3.1.1">6.3.1.1 Boolean, characters, and integers</a></h5>
2452 Every integer type has an integer conversion rank defined as follows:
2454 <li> No two signed integer types shall have the same rank, even if they have the same
2456 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
2457 type with less precision.
2458 <li> The rank of long long int shall be greater than the rank of long int, which
2459 shall be greater than the rank of int, which shall be greater than the rank of short
2460 int, which shall be greater than the rank of signed char.
2461 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
2462 signed integer type, if any.
2463 <li> The rank of any standard integer type shall be greater than the rank of any extended
2464 integer type with the same width.
2465 <li> The rank of char shall equal the rank of signed char and unsigned char.
2466 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
2467 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
2468 (see <a href="#6.7.2.2">6.7.2.2</a>).
2469 <li> The rank of any extended signed integer type relative to another extended signed
2470 integer type with the same precision is implementation-defined, but still subject to the
2471 other rules for determining the integer conversion rank.
2472 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2473 greater rank than T3, then T1 has greater rank than T3.
2476 The following may be used in an expression wherever an int or unsigned int may
2480 <li> An object or expression with an integer type whose integer conversion rank is less
2481 than or equal to the rank of int and unsigned int.
2482 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
2484 If an int can represent all values of the original type, the value is converted to an int;
2485 otherwise, it is converted to an unsigned int. These are called the integer
2486 promotions.<sup><a href="#note48"><b>48)</b></a></sup> All other types are unchanged by the integer promotions.
2488 The integer promotions preserve value including sign. As discussed earlier, whether a
2489 ''plain'' char is treated as signed is implementation-defined.
2490 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2491 (<a href="#6.7.2.1">6.7.2.1</a>).
2494 <p><small><a name="note48" href="#note48">48)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2495 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2496 shift operators, as specified by their respective subclauses.
2499 <h5><a name="6.3.1.2" href="#6.3.1.2">6.3.1.2 Boolean type</a></h5>
2501 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2502 to 0; otherwise, the result is 1.
2504 <h5><a name="6.3.1.3" href="#6.3.1.3">6.3.1.3 Signed and unsigned integers</a></h5>
2506 When a value with integer type is converted to another integer type other than _Bool, if
2507 the value can be represented by the new type, it is unchanged.
2509 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2510 subtracting one more than the maximum value that can be represented in the new type
2511 until the value is in the range of the new type.<sup><a href="#note49"><b>49)</b></a></sup>
2513 Otherwise, the new type is signed and the value cannot be represented in it; either the
2514 result is implementation-defined or an implementation-defined signal is raised.
2517 <p><small><a name="note49" href="#note49">49)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2520 <h5><a name="6.3.1.4" href="#6.3.1.4">6.3.1.4 Real floating and integer</a></h5>
2522 When a finite value of real floating type is converted to an integer type other than _Bool,
2523 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2524 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup>
2526 When a value of integer type is converted to a real floating type, if the value being
2527 converted can be represented exactly in the new type, it is unchanged. If the value being
2528 converted is in the range of values that can be represented but cannot be represented
2531 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2532 in an implementation-defined manner. If the value being converted is outside the range of
2533 values that can be represented, the behavior is undefined.
2536 <p><small><a name="note50" href="#note50">50)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
2537 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2538 range of portable real floating values is (-1, Utype_MAX+1).
2541 <h5><a name="6.3.1.5" href="#6.3.1.5">6.3.1.5 Real floating types</a></h5>
2543 When a float is promoted to double or long double, or a double is promoted
2544 to long double, its value is unchanged (if the source value is represented in the
2545 precision and range of its type).
2547 When a double is demoted to float, a long double is demoted to double or
2548 float, or a value being represented in greater precision and range than required by its
2549 semantic type (see <a href="#6.3.1.8">6.3.1.8</a>) is explicitly converted (including to its own type), if the value
2550 being converted can be represented exactly in the new type, it is unchanged. If the value
2551 being converted is in the range of values that can be represented but cannot be
2552 represented exactly, the result is either the nearest higher or nearest lower representable
2553 value, chosen in an implementation-defined manner. If the value being converted is
2554 outside the range of values that can be represented, the behavior is undefined.
2556 <h5><a name="6.3.1.6" href="#6.3.1.6">6.3.1.6 Complex types</a></h5>
2558 When a value of complex type is converted to another complex type, both the real and
2559 imaginary parts follow the conversion rules for the corresponding real types.
2561 <h5><a name="6.3.1.7" href="#6.3.1.7">6.3.1.7 Real and complex</a></h5>
2563 When a value of real type is converted to a complex type, the real part of the complex
2564 result value is determined by the rules of conversion to the corresponding real type and
2565 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2567 When a value of complex type is converted to a real type, the imaginary part of the
2568 complex value is discarded and the value of the real part is converted according to the
2569 conversion rules for the corresponding real type.
2571 <h5><a name="6.3.1.8" href="#6.3.1.8">6.3.1.8 Usual arithmetic conversions</a></h5>
2573 Many operators that expect operands of arithmetic type cause conversions and yield result
2574 types in a similar way. The purpose is to determine a common real type for the operands
2575 and result. For the specified operands, each operand is converted, without change of type
2576 domain, to a type whose corresponding real type is the common real type. Unless
2577 explicitly stated otherwise, the common real type is also the corresponding real type of
2578 the result, whose type domain is the type domain of the operands if they are the same,
2579 and complex otherwise. This pattern is called the usual arithmetic conversions:
2583 <li> First, if the corresponding real type of either operand is long double, the other
2584 operand is converted, without change of type domain, to a type whose
2585 corresponding real type is long double.
2586 <li> Otherwise, if the corresponding real type of either operand is double, the other
2587 operand is converted, without change of type domain, to a type whose
2588 corresponding real type is double.
2589 <li> Otherwise, if the corresponding real type of either operand is float, the other
2590 operand is converted, without change of type domain, to a type whose
2591 corresponding real type is float.<sup><a href="#note51"><b>51)</b></a></sup>
2592 <li> Otherwise, the integer promotions are performed on both operands. Then the
2593 following rules are applied to the promoted operands:
2595 <li> If both operands have the same type, then no further conversion is needed.
2596 <li> Otherwise, if both operands have signed integer types or both have unsigned
2597 integer types, the operand with the type of lesser integer conversion rank is
2598 converted to the type of the operand with greater rank.
2599 <li> Otherwise, if the operand that has unsigned integer type has rank greater or
2600 equal to the rank of the type of the other operand, then the operand with
2601 signed integer type is converted to the type of the operand with unsigned
2603 <li> Otherwise, if the type of the operand with signed integer type can represent
2604 all of the values of the type of the operand with unsigned integer type, then
2605 the operand with unsigned integer type is converted to the type of the
2606 operand with signed integer type.
2607 <li> Otherwise, both operands are converted to the unsigned integer type
2608 corresponding to the type of the operand with signed integer type.
2611 The values of floating operands and of the results of floating expressions may be
2612 represented in greater precision and range than that required by the type; the types are not
2613 changed thereby.<sup><a href="#note52"><b>52)</b></a></sup>
2621 <p><small><a name="note51" href="#note51">51)</a> For example, addition of a double _Complex and a float entails just the conversion of the
2622 float operand to double (and yields a double _Complex result).
2624 <p><small><a name="note52" href="#note52">52)</a> The cast and assignment operators are still required to perform their specified conversions as
2625 described in <a href="#6.3.1.4">6.3.1.4</a> and <a href="#6.3.1.5">6.3.1.5</a>.
2628 <h4><a name="6.3.2" href="#6.3.2">6.3.2 Other operands</a></h4>
2630 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
2632 An lvalue is an expression with an object type or an incomplete type other than void;<sup><a href="#note53"><b>53)</b></a></sup>
2633 if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
2634 When an object is said to have a particular type, the type is specified by the lvalue used to
2635 designate the object. A modifiable lvalue is an lvalue that does not have array type, does
2636 not have an incomplete type, does not have a const-qualified type, and if it is a structure
2637 or union, does not have any member (including, recursively, any member or element of
2638 all contained aggregates or unions) with a const-qualified type.
2640 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2641 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2642 an lvalue that does not have array type is converted to the value stored in the designated
2643 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2644 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2645 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2648 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2649 string literal used to initialize an array, an expression that has type ''array of type'' is
2650 converted to an expression with type ''pointer to type'' that points to the initial element of
2651 the array object and is not an lvalue. If the array object has register storage class, the
2652 behavior is undefined.
2654 A function designator is an expression that has function type. Except when it is the
2655 operand of the sizeof operator<sup><a href="#note54"><b>54)</b></a></sup> or the unary & operator, a function designator with
2656 type ''function returning type'' is converted to an expression that has type ''pointer to
2657 function returning type''.
2658 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2659 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), initialization (<a href="#6.7.8">6.7.8</a>), postfix
2660 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2661 (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>).
2667 <p><small><a name="note53" href="#note53">53)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2668 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2669 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2670 as the ''value of an expression''.
2671 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2672 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2674 <p><small><a name="note54" href="#note54">54)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
2675 designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
2678 <h5><a name="6.3.2.2" href="#6.3.2.2">6.3.2.2 void</a></h5>
2680 The (nonexistent) value of a void expression (an expression that has type void) shall not
2681 be used in any way, and implicit or explicit conversions (except to void) shall not be
2682 applied to such an expression. If an expression of any other type is evaluated as a void
2683 expression, its value or designator is discarded. (A void expression is evaluated for its
2686 <h5><a name="6.3.2.3" href="#6.3.2.3">6.3.2.3 Pointers</a></h5>
2688 A pointer to void may be converted to or from a pointer to any incomplete or object
2689 type. A pointer to any incomplete or object type may be converted to a pointer to void
2690 and back again; the result shall compare equal to the original pointer.
2692 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2693 the q-qualified version of the type; the values stored in the original and converted pointers
2694 shall compare equal.
2696 An integer constant expression with the value 0, or such an expression cast to type
2697 void *, is called a null pointer constant.<sup><a href="#note55"><b>55)</b></a></sup> If a null pointer constant is converted to a
2698 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2699 to a pointer to any object or function.
2701 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2702 Any two null pointers shall compare equal.
2704 An integer may be converted to any pointer type. Except as previously specified, the
2705 result is implementation-defined, might not be correctly aligned, might not point to an
2706 entity of the referenced type, and might be a trap representation.<sup><a href="#note56"><b>56)</b></a></sup>
2708 Any pointer type may be converted to an integer type. Except as previously specified, the
2709 result is implementation-defined. If the result cannot be represented in the integer type,
2710 the behavior is undefined. The result need not be in the range of values of any integer
2713 A pointer to an object or incomplete type may be converted to a pointer to a different
2714 object or incomplete type. If the resulting pointer is not correctly aligned<sup><a href="#note57"><b>57)</b></a></sup> for the
2715 pointed-to type, the behavior is undefined. Otherwise, when converted back again, the
2716 result shall compare equal to the original pointer. When a pointer to an object is
2720 converted to a pointer to a character type, the result points to the lowest addressed byte of
2721 the object. Successive increments of the result, up to the size of the object, yield pointers
2722 to the remaining bytes of the object.
2724 A pointer to a function of one type may be converted to a pointer to a function of another
2725 type and back again; the result shall compare equal to the original pointer. If a converted
2726 pointer is used to call a function whose type is not compatible with the pointed-to type,
2727 the behavior is undefined.
2728 <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
2729 capable of holding object pointers (<a href="#7.18.1.4">7.18.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
2733 <p><small><a name="note55" href="#note55">55)</a> The macro NULL is defined in <a href="#7.17"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.17">7.17</a>.
2735 <p><small><a name="note56" href="#note56">56)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2736 be consistent with the addressing structure of the execution environment.
2738 <p><small><a name="note57" href="#note57">57)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2739 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2740 correctly aligned for a pointer to type C.
2743 <h3><a name="6.4" href="#6.4">6.4 Lexical elements</a></h3>
2753 preprocessing-token:
2760 each non-white-space character that cannot be one of the above</pre>
2761 <h6>Constraints</h6>
2763 Each preprocessing token that is converted to a token shall have the lexical form of a
2764 keyword, an identifier, a constant, a string literal, or a punctuator.
2767 A token is the minimal lexical element of the language in translation phases 7 and 8. The
2768 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2769 A preprocessing token is the minimal lexical element of the language in translation
2770 phases 3 through 6. The categories of preprocessing tokens are: header names,
2771 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2772 single non-white-space characters that do not lexically match the other preprocessing
2773 token categories.<sup><a href="#note58"><b>58)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2774 undefined. Preprocessing tokens can be separated by white space; this consists of
2775 comments (described later), or white-space characters (space, horizontal tab, new-line,
2776 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2777 during translation phase 4, white space (or the absence thereof) serves as more than
2778 preprocessing token separation. White space may appear within a preprocessing token
2779 only as part of a header name or between the quotation characters in a character constant
2786 If the input stream has been parsed into preprocessing tokens up to a given character, the
2787 next preprocessing token is the longest sequence of characters that could constitute a
2788 preprocessing token. There is one exception to this rule: header name preprocessing
2789 tokens are recognized only within #include preprocessing directives and in
2790 implementation-defined locations within #pragma directives. In such contexts, a
2791 sequence of characters that could be either a header name or a string literal is recognized
2794 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2795 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2796 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2797 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2798 not E is a macro name.
2801 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2802 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2804 <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>),
2805 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
2806 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2807 (<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
2808 (<a href="#6.4.5">6.4.5</a>).
2811 <p><small><a name="note58" href="#note58">58)</a> An additional category, placemarkers, is used internally in translation phase 4 (see <a href="#6.10.3.3">6.10.3.3</a>); it cannot
2812 occur in source files.
2815 <h4><a name="6.4.1" href="#6.4.1">6.4.1 Keywords</a></h4>
2820 auto enum restrict unsigned
2821 break extern return void
2822 case float short volatile
2823 char for signed while
2824 const goto sizeof _Bool
2825 continue if static _Complex
2826 default inline struct _Imaginary
2829 else register union</pre>
2832 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2833 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2834 specifying imaginary types.<sup><a href="#note59"><b>59)</b></a></sup>
2841 <p><small><a name="note59" href="#note59">59)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
2844 <h4><a name="6.4.2" href="#6.4.2">6.4.2 Identifiers</a></h4>
2846 <h5><a name="6.4.2.1" href="#6.4.2.1">6.4.2.1 General</a></h5>
2852 identifier identifier-nondigit
2854 identifier-nondigit:
2856 universal-character-name
2857 other implementation-defined characters
2859 _ a b c d e f g h i j k l m
2860 n o p q r s t u v w x y z
2861 A B C D E F G H I J K L M
2862 N O P Q R S T U V W X Y Z
2864 0 1 2 3 4 5 6 7 8 9</pre>
2867 An identifier is a sequence of nondigit characters (including the underscore _, the
2868 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2869 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2870 There is no specific limit on the maximum length of an identifier.
2872 Each universal character name in an identifier shall designate a character whose encoding
2873 in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.<sup><a href="#note60"><b>60)</b></a></sup> The initial
2874 character shall not be a universal character name designating a digit. An implementation
2875 may allow multibyte characters that are not part of the basic source character set to
2876 appear in identifiers; which characters and their correspondence to universal character
2877 names is implementation-defined.
2879 When preprocessing tokens are converted to tokens during translation phase 7, if a
2880 preprocessing token could be converted to either a keyword or an identifier, it is converted
2885 <h6> Implementation limits</h6>
2887 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2888 characters in an identifier; the limit for an external name (an identifier that has external
2889 linkage) may be more restrictive than that for an internal name (a macro name or an
2890 identifier that does not have external linkage). The number of significant characters in an
2891 identifier is implementation-defined.
2893 Any identifiers that differ in a significant character are different identifiers. If two
2894 identifiers differ only in nonsignificant characters, the behavior is undefined.
2895 <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>).
2898 <p><small><a name="note60" href="#note60">60)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
2899 name may be used in forming valid external identifiers. For example, some otherwise unused
2900 character or sequence of characters may be used to encode the \u in a universal character name.
2901 Extended characters may produce a long external identifier.
2904 <h5><a name="6.4.2.2" href="#6.4.2.2">6.4.2.2 Predefined identifiers</a></h5>
2907 The identifier __func__ shall be implicitly declared by the translator as if,
2908 immediately following the opening brace of each function definition, the declaration
2910 static const char __func__[] = "function-name";</pre>
2911 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note61"><b>61)</b></a></sup>
2913 This name is encoded as if the implicit declaration had been written in the source
2914 character set and then translated into the execution character set as indicated in translation
2917 EXAMPLE Consider the code fragment:
2919 #include <a href="#7.19"><stdio.h></a>
2922 printf("%s\n", __func__);
2925 Each time the function is called, it will print to the standard output stream:
2929 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
2937 <p><small><a name="note61" href="#note61">61)</a> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
2938 identifier is explicitly declared using the name __func__, the behavior is undefined.
2941 <h4><a name="6.4.3" href="#6.4.3">6.4.3 Universal character names</a></h4>
2945 universal-character-name:
2947 \U hex-quad hex-quad
2949 hexadecimal-digit hexadecimal-digit
2950 hexadecimal-digit hexadecimal-digit</pre>
2951 <h6>Constraints</h6>
2953 A universal character name shall not specify a character whose short identifier is less than
2954 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
2955 DFFF inclusive.<sup><a href="#note62"><b>62)</b></a></sup>
2956 <h6>Description</h6>
2958 Universal character names may be used in identifiers, character constants, and string
2959 literals to designate characters that are not in the basic character set.
2962 The universal character name \Unnnnnnnn designates the character whose eight-digit
2963 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note63"><b>63)</b></a></sup> Similarly, the universal
2964 character name \unnnn designates the character whose four-digit short identifier is nnnn
2965 (and whose eight-digit short identifier is 0000nnnn).
2973 <p><small><a name="note62" href="#note62">62)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
2974 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
2977 <p><small><a name="note63" href="#note63">63)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
2980 <h4><a name="6.4.4" href="#6.4.4">6.4.4 Constants</a></h4>
2987 enumeration-constant
2988 character-constant</pre>
2989 <h6>Constraints</h6>
2991 Each constant shall have a type and the value of a constant shall be in the range of
2992 representable values for its type.
2995 Each constant has a type, determined by its form and value, as detailed later.
2997 <h5><a name="6.4.4.1" href="#6.4.4.1">6.4.4.1 Integer constants</a></h5>
3003 decimal-constant integer-suffix<sub>opt</sub>
3004 octal-constant integer-suffix<sub>opt</sub>
3005 hexadecimal-constant integer-suffix<sub>opt</sub>
3008 decimal-constant digit
3011 octal-constant octal-digit
3012 hexadecimal-constant:
3013 hexadecimal-prefix hexadecimal-digit
3014 hexadecimal-constant hexadecimal-digit
3015 hexadecimal-prefix: one of
3017 nonzero-digit: one of
3021 hexadecimal-digit: one of
3026 unsigned-suffix long-suffix<sub>opt</sub>
3027 unsigned-suffix long-long-suffix
3028 long-suffix unsigned-suffix<sub>opt</sub>
3029 long-long-suffix unsigned-suffix<sub>opt</sub>
3030 unsigned-suffix: one of
3034 long-long-suffix: one of
3036 <h6>Description</h6>
3038 An integer constant begins with a digit, but has no period or exponent part. It may have a
3039 prefix that specifies its base and a suffix that specifies its type.
3041 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3042 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3043 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3044 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3045 10 through 15 respectively.
3048 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3049 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3051 The type of an integer constant is the first of the corresponding list in which its value can
3055 <tr><th> Suffix <th>Decimal Constant <th>Octal or Hexadecimal Constant
3065 unsigned long long int</pre>
3067 <td><pre>unsigned int
3069 unsigned long long int</pre>
3070 <td><pre>unsigned int
3072 unsigned long long int</pre>
3079 unsigned long long int</pre>
3080 <tr><td> Both u or U and l or L
3081 <td><pre>unsigned long int
3082 unsigned long long int</pre>
3083 <td><pre>unsigned long int
3084 unsigned long long int</pre>
3086 <td><pre>long long int</pre>
3087 <td><pre>long long int
3088 unsigned long long int</pre>
3089 <tr><td> Both u or U and ll or LL
3090 <td><pre>unsigned long long int</pre>
3091 <td><pre>unsigned long long int</pre>
3094 If an integer constant cannot be represented by any type in its list, it may have an
3095 extended integer type, if the extended integer type can represent its value. If all of the
3096 types in the list for the constant are signed, the extended integer type shall be signed. If
3097 all of the types in the list for the constant are unsigned, the extended integer type shall be
3098 unsigned. If the list contains both signed and unsigned types, the extended integer type
3099 may be signed or unsigned. If an integer constant cannot be represented by any type in
3100 its list and has no extended integer type, then the integer constant has no type.
3103 <h5><a name="6.4.4.2" href="#6.4.4.2">6.4.4.2 Floating constants</a></h5>
3109 decimal-floating-constant
3110 hexadecimal-floating-constant
3111 decimal-floating-constant:
3112 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
3113 digit-sequence exponent-part floating-suffix<sub>opt</sub>
3114 hexadecimal-floating-constant:
3115 hexadecimal-prefix hexadecimal-fractional-constant
3116 binary-exponent-part floating-suffix<sub>opt</sub>
3117 hexadecimal-prefix hexadecimal-digit-sequence
3118 binary-exponent-part floating-suffix<sub>opt</sub>
3119 fractional-constant:
3120 digit-sequence<sub>opt</sub> . digit-sequence
3123 e sign<sub>opt</sub> digit-sequence
3124 E sign<sub>opt</sub> digit-sequence
3129 digit-sequence digit
3130 hexadecimal-fractional-constant:
3131 hexadecimal-digit-sequence<sub>opt</sub> .
3132 hexadecimal-digit-sequence
3133 hexadecimal-digit-sequence .
3134 binary-exponent-part:
3135 p sign<sub>opt</sub> digit-sequence
3136 P sign<sub>opt</sub> digit-sequence
3137 hexadecimal-digit-sequence:
3139 hexadecimal-digit-sequence hexadecimal-digit
3140 floating-suffix: one of
3142 <h6>Description</h6>
3144 A floating constant has a significand part that may be followed by an exponent part and a
3145 suffix that specifies its type. The components of the significand part may include a digit
3146 sequence representing the whole-number part, followed by a period (.), followed by a
3147 digit sequence representing the fraction part. The components of the exponent part are an
3148 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3149 Either the whole-number part or the fraction part has to be present; for decimal floating
3150 constants, either the period or the exponent part has to be present.
3153 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3154 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3155 floating constants, the exponent indicates the power of 10 by which the significand part is
3156 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3157 by which the significand part is to be scaled. For decimal floating constants, and also for
3158 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3159 the nearest representable value, or the larger or smaller representable value immediately
3160 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3161 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3164 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3165 type float. If suffixed by the letter l or L, it has type long double.
3167 Floating constants are converted to internal format as if at translation-time. The
3168 conversion of a floating constant shall not raise an exceptional condition or a floating-
3169 point exception at execution time.
3170 <h6>Recommended practice</h6>
3172 The implementation should produce a diagnostic message if a hexadecimal constant
3173 cannot be represented exactly in its evaluation format; the implementation should then
3174 proceed with the translation of the program.
3176 The translation-time conversion of floating constants should match the execution-time
3177 conversion of character strings by library functions, such as strtod, given matching
3178 inputs suitable for both conversions, the same result format, and default execution-time
3179 rounding.<sup><a href="#note64"><b>64)</b></a></sup>
3187 <p><small><a name="note64" href="#note64">64)</a> The specification for the library functions recommends more accurate conversion than required for
3188 floating constants (see <a href="#7.20.1.3">7.20.1.3</a>).
3191 <h5><a name="6.4.4.3" href="#6.4.4.3">6.4.4.3 Enumeration constants</a></h5>
3195 enumeration-constant:
3199 An identifier declared as an enumeration constant has type int.
3200 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
3202 <h5><a name="6.4.4.4" href="#6.4.4.4">6.4.4.4 Character constants</a></h5>
3209 L' c-char-sequence '
3212 c-char-sequence c-char
3214 any member of the source character set except
3215 the single-quote ', backslash \, or new-line character
3218 simple-escape-sequence
3219 octal-escape-sequence
3220 hexadecimal-escape-sequence
3221 universal-character-name
3222 simple-escape-sequence: one of
3224 \a \b \f \n \r \t \v
3225 octal-escape-sequence:
3227 \ octal-digit octal-digit
3228 \ octal-digit octal-digit octal-digit
3229 hexadecimal-escape-sequence:
3230 \x hexadecimal-digit
3231 hexadecimal-escape-sequence hexadecimal-digit</pre>
3232 <h6>Description</h6>
3234 An integer character constant is a sequence of one or more multibyte characters enclosed
3235 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3236 letter L. With a few exceptions detailed later, the elements of the sequence are any
3237 members of the source character set; they are mapped in an implementation-defined
3238 manner to members of the execution character set.
3240 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3241 arbitrary integer values are representable according to the following table of escape
3249 octal character \octal digits
3250 hexadecimal character \x hexadecimal digits</pre>
3251 The double-quote " and question-mark ? are representable either by themselves or by the
3252 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3253 shall be represented, respectively, by the escape sequences \' and \\.
3255 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3256 of the construction of a single character for an integer character constant or of a single
3257 wide character for a wide character constant. The numerical value of the octal integer so
3258 formed specifies the value of the desired character or wide character.
3260 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3261 sequence are taken to be part of the construction of a single character for an integer
3262 character constant or of a single wide character for a wide character constant. The
3263 numerical value of the hexadecimal integer so formed specifies the value of the desired
3264 character or wide character.
3266 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3267 constitute the escape sequence.
3269 In addition, characters not in the basic character set are representable by universal
3270 character names and certain nongraphic characters are representable by escape sequences
3271 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3272 and \v.<sup><a href="#note65"><b>65)</b></a></sup>
3278 <h6>Constraints</h6>
3280 The value of an octal or hexadecimal escape sequence shall be in the range of
3281 representable values for the type unsigned char for an integer character constant, or
3282 the unsigned type corresponding to wchar_t for a wide character constant.
3285 An integer character constant has type int. The value of an integer character constant
3286 containing a single character that maps to a single-byte execution character is the
3287 numerical value of the representation of the mapped character interpreted as an integer.
3288 The value of an integer character constant containing more than one character (e.g.,
3289 'ab'), or containing a character or escape sequence that does not map to a single-byte
3290 execution character, is implementation-defined. If an integer character constant contains
3291 a single character or escape sequence, its value is the one that results when an object with
3292 type char whose value is that of the single character or escape sequence is converted to
3295 A wide character constant has type wchar_t, an integer type defined in the
3296 <a href="#7.17"><stddef.h></a> header. The value of a wide character constant containing a single
3297 multibyte character that maps to a member of the extended execution character set is the
3298 wide character corresponding to that multibyte character, as defined by the mbtowc
3299 function, with an implementation-defined current locale. The value of a wide character
3300 constant containing more than one multibyte character, or containing a multibyte
3301 character or escape sequence not represented in the extended execution character set, is
3302 implementation-defined.
3304 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3307 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3308 bits for objects that have type char. In an implementation in which type char has the same range of
3309 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3310 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3313 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3314 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3315 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3316 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3317 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3318 constant is implementation-defined.)
3321 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3322 L'\1234' specifies the implementation-defined value that results from the combination of the values
3325 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbtowc function
3326 (<a href="#7.20.7.2">7.20.7.2</a>).
3330 <p><small><a name="note65" href="#note65">65)</a> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
3331 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3334 <h4><a name="6.4.5" href="#6.4.5">6.4.5 String literals</a></h4>
3339 " s-char-sequence<sub>opt</sub> "
3340 L" s-char-sequence<sub>opt</sub> "
3343 s-char-sequence s-char
3345 any member of the source character set except
3346 the double-quote ", backslash \, or new-line character
3347 escape-sequence</pre>
3348 <h6>Description</h6>
3350 A character string literal is a sequence of zero or more multibyte characters enclosed in
3351 double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
3354 The same considerations apply to each element of the sequence in a character string
3355 literal or a wide string literal as if it were in an integer character constant or a wide
3356 character constant, except that the single-quote ' is representable either by itself or by the
3357 escape sequence \', but the double-quote " shall be represented by the escape sequence
3361 In translation phase 6, the multibyte character sequences specified by any sequence of
3362 adjacent character and wide string literal tokens are concatenated into a single multibyte
3363 character sequence. If any of the tokens are wide string literal tokens, the resulting
3364 multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
3365 character string literal.
3367 In translation phase 7, a byte or code of value zero is appended to each multibyte
3368 character sequence that results from a string literal or literals.<sup><a href="#note66"><b>66)</b></a></sup> The multibyte character
3369 sequence is then used to initialize an array of static storage duration and length just
3370 sufficient to contain the sequence. For character string literals, the array elements have
3371 type char, and are initialized with the individual bytes of the multibyte character
3372 sequence; for wide string literals, the array elements have type wchar_t, and are
3373 initialized with the sequence of wide characters corresponding to the multibyte character
3376 sequence, as defined by the mbstowcs function with an implementation-defined current
3377 locale. The value of a string literal containing a multibyte character or escape sequence
3378 not represented in the execution character set is implementation-defined.
3380 It is unspecified whether these arrays are distinct provided their elements have the
3381 appropriate values. If the program attempts to modify such an array, the behavior is
3384 EXAMPLE This pair of adjacent character string literals
3387 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3388 because escape sequences are converted into single members of the execution character set just prior to
3389 adjacent string literal concatenation.
3391 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbstowcs
3392 function (<a href="#7.20.8.1">7.20.8.1</a>).
3395 <p><small><a name="note66" href="#note66">66)</a> A character string literal need not be a string (see <a href="#7.1.1">7.1.1</a>), because a null character may be embedded in
3396 it by a \0 escape sequence.
3399 <h4><a name="6.4.6" href="#6.4.6">6.4.6 Punctuators</a></h4>
3405 ++ -- & * + - ~ !
3406 / % << >> < > <= >= == != ^ | && ||
3408 = *= /= %= += -= <<= >>= &= ^= |=
3410 <: :> <% %> %: %:%:</pre>
3413 A punctuator is a symbol that has independent syntactic and semantic significance.
3414 Depending on context, it may specify an operation to be performed (which in turn may
3415 yield a value or a function designator, produce a side effect, or some combination thereof)
3416 in which case it is known as an operator (other forms of operator also exist in some
3417 contexts). An operand is an entity on which an operator acts.
3420 In all aspects of the language, the six tokens<sup><a href="#note67"><b>67)</b></a></sup>
3422 <: :> <% %> %: %:%:</pre>
3423 behave, respectively, the same as the six tokens
3426 except for their spelling.<sup><a href="#note68"><b>68)</b></a></sup>
3427 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3428 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
3431 <p><small><a name="note67" href="#note67">67)</a> These tokens are sometimes called ''digraphs''.
3433 <p><small><a name="note68" href="#note68">68)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3437 <h4><a name="6.4.7" href="#6.4.7">6.4.7 Header names</a></h4>
3442 < h-char-sequence >
3446 h-char-sequence h-char
3448 any member of the source character set except
3449 the new-line character and >
3452 q-char-sequence q-char
3454 any member of the source character set except
3455 the new-line character and "</pre>
3458 The sequences in both forms of header names are mapped in an implementation-defined
3459 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
3461 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3462 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3468 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note69"><b>69)</b></a></sup> Header name
3469 preprocessing tokens are recognized only within #include preprocessing directives and
3470 in implementation-defined locations within #pragma directives.<sup><a href="#note70"><b>70)</b></a></sup>
3472 EXAMPLE The following sequence of characters:
3475 #include <1/a.h>
3476 #define const.member@$</pre>
3477 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3478 by a { on the left and a } on the right).
3480 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3481 {#}{include} {<1/a.h>}
3482 {#}{define} {const}{.}{member}{@}{$}</pre>
3484 <p><b> Forward references</b>: source file inclusion (<a href="#6.10.2">6.10.2</a>).
3487 <p><small><a name="note69" href="#note69">69)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3489 <p><small><a name="note70" href="#note70">70)</a> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
3492 <h4><a name="6.4.8" href="#6.4.8">6.4.8 Preprocessing numbers</a></h4>
3500 pp-number identifier-nondigit
3506 <h6>Description</h6>
3508 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3509 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3512 Preprocessing number tokens lexically include all floating and integer constant tokens.
3515 A preprocessing number does not have type or a value; it acquires both after a successful
3516 conversion (as part of translation phase 7) to a floating constant token or an integer
3522 <h4><a name="6.4.9" href="#6.4.9">6.4.9 Comments</a></h4>
3524 Except within a character constant, a string literal, or a comment, the characters /*
3525 introduce a comment. The contents of such a comment are examined only to identify
3526 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note71"><b>71)</b></a></sup>
3528 Except within a character constant, a string literal, or a comment, the characters //
3529 introduce a comment that includes all multibyte characters up to, but not including, the
3530 next new-line character. The contents of such a comment are examined only to identify
3531 multibyte characters and to find the terminating new-line character.
3535 "a//b" // four-character string literal
3536 #include "//e" // undefined behavior
3537 // */ // comment, not syntax error
3538 f = g/**//h; // equivalent to f = g / h;
3540 i(); // part of a two-line comment
3542 / j(); // part of a two-line comment
3543 #define glue(x,y) x##y
3544 glue(/,/) k(); // syntax error, not comment
3545 /*//*/ l(); // equivalent to l();
3547 + p; // equivalent to m = n + p;</pre>
3555 <p><small><a name="note71" href="#note71">71)</a> Thus, /* ... */ comments do not nest.
3558 <h3><a name="6.5" href="#6.5">6.5 Expressions</a></h3>
3560 An expression is a sequence of operators and operands that specifies computation of a
3561 value, or that designates an object or a function, or that generates side effects, or that
3562 performs a combination thereof.
3564 Between the previous and next sequence point an object shall have its stored value
3565 modified at most once by the evaluation of an expression.<sup><a href="#note72"><b>72)</b></a></sup> Furthermore, the prior value
3566 shall be read only to determine the value to be stored.<sup><a href="#note73"><b>73)</b></a></sup>
3568 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note74"><b>74)</b></a></sup> Except as specified
3569 later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
3570 of subexpressions and the order in which side effects take place are both unspecified.
3572 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3573 collectively described as bitwise operators) are required to have operands that have
3574 integer type. These operators yield values that depend on the internal representations of
3575 integers, and have implementation-defined and undefined aspects for signed types.
3577 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3578 result is not mathematically defined or not in the range of representable values for its
3579 type), the behavior is undefined.
3581 The effective type of an object for an access to its stored value is the declared type of the
3582 object, if any.<sup><a href="#note75"><b>75)</b></a></sup> If a value is stored into an object having no declared type through an
3583 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3587 effective type of the object for that access and for subsequent accesses that do not modify
3588 the stored value. If a value is copied into an object having no declared type using
3589 memcpy or memmove, or is copied as an array of character type, then the effective type
3590 of the modified object for that access and for subsequent accesses that do not modify the
3591 value is the effective type of the object from which the value is copied, if it has one. For
3592 all other accesses to an object having no declared type, the effective type of the object is
3593 simply the type of the lvalue used for the access.
3595 An object shall have its stored value accessed only by an lvalue expression that has one of
3596 the following types:<sup><a href="#note76"><b>76)</b></a></sup>
3598 <li> a type compatible with the effective type of the object,
3599 <li> a qualified version of a type compatible with the effective type of the object,
3600 <li> a type that is the signed or unsigned type corresponding to the effective type of the
3602 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
3603 effective type of the object,
3604 <li> an aggregate or union type that includes one of the aforementioned types among its
3605 members (including, recursively, a member of a subaggregate or contained union), or
3606 <li> a character type.
3609 A floating expression may be contracted, that is, evaluated as though it were an atomic
3610 operation, thereby omitting rounding errors implied by the source code and the
3611 expression evaluation method.<sup><a href="#note77"><b>77)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3612 way to disallow contracted expressions. Otherwise, whether and how expressions are
3613 contracted is implementation-defined.<sup><a href="#note78"><b>78)</b></a></sup>
3614 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.21.2">7.21.2</a>).
3622 <p><small><a name="note72" href="#note72">72)</a> A floating-point status flag is not an object and can be set more than once within an expression.
3624 <p><small><a name="note73" href="#note73">73)</a> This paragraph renders undefined statement expressions such as
3635 <p><small><a name="note74" href="#note74">74)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3636 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3637 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3638 <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
3639 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3640 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
3641 the conditional operator ?: (<a href="#6.5.15">6.5.15</a>).
3643 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3644 indicated in each subclause by the syntax for the expressions discussed therein.
3646 <p><small><a name="note75" href="#note75">75)</a> Allocated objects have no declared type.
3648 <p><small><a name="note76" href="#note76">76)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3650 <p><small><a name="note77" href="#note77">77)</a> A contracted expression might also omit the raising of floating-point exceptions.
3652 <p><small><a name="note78" href="#note78">78)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
3653 combine multiple C operators. As contractions potentially undermine predictability, and can even
3654 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3658 <h4><a name="6.5.1" href="#6.5.1">6.5.1 Primary expressions</a></h4>
3666 ( expression )</pre>
3669 An identifier is a primary expression, provided it has been declared as designating an
3670 object (in which case it is an lvalue) or a function (in which case it is a function
3671 designator).<sup><a href="#note79"><b>79)</b></a></sup>
3673 A constant is a primary expression. Its type depends on its form and value, as detailed in
3674 <a href="#6.4.4">6.4.4</a>.
3676 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>.
3678 A parenthesized expression is a primary expression. Its type and value are identical to
3679 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3680 expression if the unparenthesized expression is, respectively, an lvalue, a function
3681 designator, or a void expression.
3682 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>).
3685 <p><small><a name="note79" href="#note79">79)</a> Thus, an undeclared identifier is a violation of the syntax.
3688 <h4><a name="6.5.2" href="#6.5.2">6.5.2 Postfix operators</a></h4>
3694 postfix-expression [ expression ]
3695 postfix-expression ( argument-expression-listopt )
3696 postfix-expression . identifier
3697 postfix-expression -> identifier
3698 postfix-expression ++
3699 postfix-expression --
3700 ( type-name ) { initializer-list }
3701 ( type-name ) { initializer-list , }</pre>
3708 argument-expression-list:
3709 assignment-expression
3710 argument-expression-list , assignment-expression</pre>
3712 <h5><a name="6.5.2.1" href="#6.5.2.1">6.5.2.1 Array subscripting</a></h5>
3713 <h6>Constraints</h6>
3715 One of the expressions shall have type ''pointer to object type'', the other expression shall
3716 have integer type, and the result has type ''type''.
3719 A postfix expression followed by an expression in square brackets [] is a subscripted
3720 designation of an element of an array object. The definition of the subscript operator []
3721 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3722 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3723 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3724 element of E1 (counting from zero).
3726 Successive subscript operators designate an element of a multidimensional array object.
3727 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3728 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3729 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3730 implicitly as a result of subscripting, the result is the pointed-to (n - 1)-dimensional array,
3731 which itself is converted into a pointer if used as other than an lvalue. It follows from this
3732 that arrays are stored in row-major order (last subscript varies fastest).
3734 EXAMPLE Consider the array object defined by the declaration
3737 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
3738 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3739 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3740 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3741 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3742 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3745 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3746 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
3749 <h5><a name="6.5.2.2" href="#6.5.2.2">6.5.2.2 Function calls</a></h5>
3750 <h6>Constraints</h6>
3752 The expression that denotes the called function<sup><a href="#note80"><b>80)</b></a></sup> shall have type pointer to function
3753 returning void or returning an object type other than an array type.
3755 If the expression that denotes the called function has a type that includes a prototype, the
3756 number of arguments shall agree with the number of parameters. Each argument shall
3757 have a type such that its value may be assigned to an object with the unqualified version
3758 of the type of its corresponding parameter.
3761 A postfix expression followed by parentheses () containing a possibly empty, comma-
3762 separated list of expressions is a function call. The postfix expression denotes the called
3763 function. The list of expressions specifies the arguments to the function.
3765 An argument may be an expression of any object type. In preparing for the call to a
3766 function, the arguments are evaluated, and each parameter is assigned the value of the
3767 corresponding argument.<sup><a href="#note81"><b>81)</b></a></sup>
3769 If the expression that denotes the called function has type pointer to function returning an
3770 object type, the function call expression has the same type as that object type, and has the
3771 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. If
3772 an attempt is made to modify the result of a function call or to access it after the next
3773 sequence point, the behavior is undefined.
3775 If the expression that denotes the called function has a type that does not include a
3776 prototype, the integer promotions are performed on each argument, and arguments that
3777 have type float are promoted to double. These are called the default argument
3778 promotions. If the number of arguments does not equal the number of parameters, the
3779 behavior is undefined. If the function is defined with a type that includes a prototype, and
3780 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3781 promotion are not compatible with the types of the parameters, the behavior is undefined.
3782 If the function is defined with a type that does not include a prototype, and the types of
3783 the arguments after promotion are not compatible with those of the parameters after
3784 promotion, the behavior is undefined, except for the following cases:
3791 <li> one promoted type is a signed integer type, the other promoted type is the
3792 corresponding unsigned integer type, and the value is representable in both types;
3793 <li> both types are pointers to qualified or unqualified versions of a character type or
3797 If the expression that denotes the called function has a type that does include a prototype,
3798 the arguments are implicitly converted, as if by assignment, to the types of the
3799 corresponding parameters, taking the type of each parameter to be the unqualified version
3800 of its declared type. The ellipsis notation in a function prototype declarator causes
3801 argument type conversion to stop after the last declared parameter. The default argument
3802 promotions are performed on trailing arguments.
3804 No other conversions are performed implicitly; in particular, the number and types of
3805 arguments are not compared with those of the parameters in a function definition that
3806 does not include a function prototype declarator.
3808 If the function is defined with a type that is not compatible with the type (of the
3809 expression) pointed to by the expression that denotes the called function, the behavior is
3812 The order of evaluation of the function designator, the actual arguments, and
3813 subexpressions within the actual arguments is unspecified, but there is a sequence point
3814 before the actual call.
3816 Recursive function calls shall be permitted, both directly and indirectly through any chain
3819 EXAMPLE In the function call
3821 (*pf[f1()]) (f2(), f3() + f4())</pre>
3822 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3823 the function pointed to by pf[f1()] is called.
3825 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), function
3826 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>).
3829 <p><small><a name="note80" href="#note80">80)</a> Most often, this is the result of converting an identifier that is a function designator.
3831 <p><small><a name="note81" href="#note81">81)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
3832 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3833 change the value of the object pointed to. A parameter declared to have array or function type is
3834 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
3837 <h5><a name="6.5.2.3" href="#6.5.2.3">6.5.2.3 Structure and union members</a></h5>
3838 <h6>Constraints</h6>
3840 The first operand of the . operator shall have a qualified or unqualified structure or union
3841 type, and the second operand shall name a member of that type.
3843 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3844 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3845 name a member of the type pointed to.
3849 A postfix expression followed by the . operator and an identifier designates a member of
3850 a structure or union object. The value is that of the named member,<sup><a href="#note82"><b>82)</b></a></sup> and is an lvalue if
3851 the first expression is an lvalue. If the first expression has qualified type, the result has
3852 the so-qualified version of the type of the designated member.
3854 A postfix expression followed by the -> operator and an identifier designates a member
3855 of a structure or union object. The value is that of the named member of the object to
3856 which the first expression points, and is an lvalue.<sup><a href="#note83"><b>83)</b></a></sup> If the first expression is a pointer to
3857 a qualified type, the result has the so-qualified version of the type of the designated
3860 One special guarantee is made in order to simplify the use of unions: if a union contains
3861 several structures that share a common initial sequence (see below), and if the union
3862 object currently contains one of these structures, it is permitted to inspect the common
3863 initial part of any of them anywhere that a declaration of the complete type of the union is
3864 visible. Two structures share a common initial sequence if corresponding members have
3865 compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3868 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3869 union, f().x is a valid postfix expression but is not an lvalue.
3874 struct s { int i; const int ci; };
3877 volatile struct s vs;</pre>
3878 the various members have the types:
3885 vs.ci volatile const int</pre>
3892 EXAMPLE 3 The following is a valid fragment:
3908 u.nf.doublenode = <a href="#3.14">3.14</a>;
3910 if (u.n.alltypes == 1)
3911 if (sin(u.nf.doublenode) == 0.0)
3913 The following is not a valid fragment (because the union type is not visible within function f):
3915 struct t1 { int m; };
3916 struct t2 { int m; };
3917 int f(struct t1 *p1, struct t2 *p2)
3919 if (p1->m < 0)
3920 p2->m = -p2->m;
3930 return f(&u.s1, &u.s2);
3933 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
3934 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
3938 <p><small><a name="note82" href="#note82">82)</a> If the member used to access the contents of a union object is not the same as the member last used to
3939 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3940 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
3941 punning"). This might be a trap representation.
3943 <p><small><a name="note83" href="#note83">83)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
3944 its operand), the expression (&E)->MOS is the same as E.MOS.
3947 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
3948 <h6>Constraints</h6>
3950 The operand of the postfix increment or decrement operator shall have qualified or
3951 unqualified real or pointer type and shall be a modifiable lvalue.
3954 The result of the postfix ++ operator is the value of the operand. After the result is
3955 obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate
3956 type is added to it.) See the discussions of additive operators and compound assignment
3957 for information on constraints, types, and conversions and the effects of operations on
3958 pointers. The side effect of updating the stored value of the operand shall occur between
3959 the previous and the next sequence point.
3961 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
3962 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
3964 <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>).
3966 <h5><a name="6.5.2.5" href="#6.5.2.5">6.5.2.5 Compound literals</a></h5>
3967 <h6>Constraints</h6>
3969 The type name shall specify an object type or an array of unknown size, but not a variable
3972 No initializer shall attempt to provide a value for an object not contained within the entire
3973 unnamed object specified by the compound literal.
3975 If the compound literal occurs outside the body of a function, the initializer list shall
3976 consist of constant expressions.
3979 A postfix expression that consists of a parenthesized type name followed by a brace-
3980 enclosed list of initializers is a compound literal. It provides an unnamed object whose
3981 value is given by the initializer list.<sup><a href="#note84"><b>84)</b></a></sup>
3983 If the type name specifies an array of unknown size, the size is determined by the
3984 initializer list as specified in <a href="#6.7.8">6.7.8</a>, and the type of the compound literal is that of the
3985 completed array type. Otherwise (when the type name specifies an object type), the type
3986 of the compound literal is that specified by the type name. In either case, the result is an
3992 The value of the compound literal is that of an unnamed object initialized by the
3993 initializer list. If the compound literal occurs outside the body of a function, the object
3994 has static storage duration; otherwise, it has automatic storage duration associated with
3995 the enclosing block.
3997 All the semantic rules and constraints for initializer lists in <a href="#6.7.8">6.7.8</a> are applicable to
3998 compound literals.<sup><a href="#note85"><b>85)</b></a></sup>
4000 String literals, and compound literals with const-qualified types, need not designate
4001 distinct objects.<sup><a href="#note86"><b>86)</b></a></sup>
4003 EXAMPLE 1 The file scope definition
4005 int *p = (int []){2, 4};</pre>
4006 initializes p to point to the first element of an array of two ints, the first having the value two and the
4007 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4008 has static storage duration.
4011 EXAMPLE 2 In contrast, in
4020 p is assigned the address of the first element of an array of two ints, the first having the value previously
4021 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4022 unnamed object has automatic storage duration.
4025 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4026 created using compound literals can be passed to functions without depending on member order:
4028 drawline((struct point){.x=1, .y=1},
4029 (struct point){.x=3, .y=4});</pre>
4030 Or, if drawline instead expected pointers to struct point:
4032 drawline(&(struct point){.x=1, .y=1},
4033 &(struct point){.x=3, .y=4});</pre>
4036 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4038 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}</pre>
4045 EXAMPLE 5 The following three expressions have different meanings:
4048 (char []){"/tmp/fileXXXXXX"}
4049 (const char []){"/tmp/fileXXXXXX"}</pre>
4050 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4051 two have automatic storage duration when they occur within the body of a function, and the first of these
4055 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4056 and can even be shared. For example,
4058 (const char []){"abc"} == "abc"</pre>
4059 might yield 1 if the literals' storage is shared.
4062 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4063 linked object. For example, there is no way to write a self-referential compound literal that could be used
4064 as the function argument in place of the named object endless_zeros below:
4066 struct int_list { int car; struct int_list *cdr; };
4067 struct int_list endless_zeros = {0, &endless_zeros};
4068 eval(endless_zeros);</pre>
4071 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4073 struct s { int i; };
4076 struct s *p = 0, *q;
4079 q = p, p = &((struct s){ j++ });
4080 if (j < 2) goto again;
4081 return p == q && q->i == 1;
4083 The function f() always returns the value 1.
4085 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4086 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4087 have an indeterminate value, which would result in undefined behavior.
4089 <p><b> Forward references</b>: type names (<a href="#6.7.6">6.7.6</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4093 <p><small><a name="note84" href="#note84">84)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4094 or void only, and the result of a cast expression is not an lvalue.
4096 <p><small><a name="note85" href="#note85">85)</a> For example, subobjects without explicit initializers are initialized to zero.
4098 <p><small><a name="note86" href="#note86">86)</a> This allows implementations to share storage for string literals and constant compound literals with
4099 the same or overlapping representations.
4102 <h4><a name="6.5.3" href="#6.5.3">6.5.3 Unary operators</a></h4>
4110 unary-operator cast-expression
4111 sizeof unary-expression
4112 sizeof ( type-name )
4113 unary-operator: one of
4114 & * + - ~ !</pre>
4116 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
4117 <h6>Constraints</h6>
4119 The operand of the prefix increment or decrement operator shall have qualified or
4120 unqualified real or pointer type and shall be a modifiable lvalue.
4123 The value of the operand of the prefix ++ operator is incremented. The result is the new
4124 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4125 See the discussions of additive operators and compound assignment for information on
4126 constraints, types, side effects, and conversions and the effects of operations on pointers.
4128 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4129 operand is decremented.
4130 <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>).
4132 <h5><a name="6.5.3.2" href="#6.5.3.2">6.5.3.2 Address and indirection operators</a></h5>
4133 <h6>Constraints</h6>
4135 The operand of the unary & operator shall be either a function designator, the result of a
4136 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4137 not declared with the register storage-class specifier.
4139 The operand of the unary * operator shall have pointer type.
4142 The unary & operator yields the address of its operand. If the operand has type ''type'',
4143 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4144 neither that operator nor the & operator is evaluated and the result is as if both were
4145 omitted, except that the constraints on the operators still apply and the result is not an
4146 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4148 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4149 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4150 a pointer to the object or function designated by its operand.
4152 The unary * operator denotes indirection. If the operand points to a function, the result is
4153 a function designator; if it points to an object, the result is an lvalue designating the
4154 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4155 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4156 undefined.<sup><a href="#note87"><b>87)</b></a></sup>
4157 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4158 (<a href="#6.7.2.1">6.7.2.1</a>).
4161 <p><small><a name="note87" href="#note87">87)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4162 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4163 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4164 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4165 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4166 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4167 end of its lifetime.
4170 <h5><a name="6.5.3.3" href="#6.5.3.3">6.5.3.3 Unary arithmetic operators</a></h5>
4171 <h6>Constraints</h6>
4173 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4174 integer type; of the ! operator, scalar type.
4177 The result of the unary + operator is the value of its (promoted) operand. The integer
4178 promotions are performed on the operand, and the result has the promoted type.
4180 The result of the unary - operator is the negative of its (promoted) operand. The integer
4181 promotions are performed on the operand, and the result has the promoted type.
4183 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4184 each bit in the result is set if and only if the corresponding bit in the converted operand is
4185 not set). The integer promotions are performed on the operand, and the result has the
4186 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4187 to the maximum value representable in that type minus E.
4189 The result of the logical negation operator ! is 0 if the value of its operand compares
4190 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4191 The expression !E is equivalent to (0==E).
4198 <h5><a name="6.5.3.4" href="#6.5.3.4">6.5.3.4 The sizeof operator</a></h5>
4199 <h6>Constraints</h6>
4201 The sizeof operator shall not be applied to an expression that has function type or an
4202 incomplete type, to the parenthesized name of such a type, or to an expression that
4203 designates a bit-field member.
4206 The sizeof operator yields the size (in bytes) of its operand, which may be an
4207 expression or the parenthesized name of a type. The size is determined from the type of
4208 the operand. The result is an integer. If the type of the operand is a variable length array
4209 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4212 When applied to an operand that has type char, unsigned char, or signed char,
4213 (or a qualified version thereof) the result is 1. When applied to an operand that has array
4214 type, the result is the total number of bytes in the array.<sup><a href="#note88"><b>88)</b></a></sup> When applied to an operand
4215 that has structure or union type, the result is the total number of bytes in such an object,
4216 including internal and trailing padding.
4218 The value of the result is implementation-defined, and its type (an unsigned integer type)
4219 is size_t, defined in <a href="#7.17"><stddef.h></a> (and other headers).
4221 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4222 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4223 allocate and return a pointer to void. For example:
4225 extern void *alloc(size_t);
4226 double *dp = alloc(sizeof *dp);</pre>
4227 The implementation of the alloc function should ensure that its return value is aligned suitably for
4228 conversion to a pointer to double.
4231 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4233 sizeof array / sizeof array[0]</pre>
4236 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4239 #include <a href="#7.17"><stddef.h></a>
4240 size_t fsize3(int n)
4242 char b[n+3]; // variable length array
4243 return sizeof b; // execution time sizeof
4253 size = fsize3(10); // fsize3 returns 13
4257 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), declarations (<a href="#6.7">6.7</a>),
4258 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.6">6.7.6</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
4261 <p><small><a name="note88" href="#note88">88)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
4262 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
4265 <h4><a name="6.5.4" href="#6.5.4">6.5.4 Cast operators</a></h4>
4271 ( type-name ) cast-expression</pre>
4272 <h6>Constraints</h6>
4274 Unless the type name specifies a void type, the type name shall specify qualified or
4275 unqualified scalar type and the operand shall have scalar type.
4277 Conversions that involve pointers, other than where permitted by the constraints of
4278 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
4281 Preceding an expression by a parenthesized type name converts the value of the
4282 expression to the named type. This construction is called a cast.<sup><a href="#note89"><b>89)</b></a></sup> A cast that specifies
4283 no conversion has no effect on the type or value of an expression.
4285 If the value of the expression is represented with greater precision or range than required
4286 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
4287 type of the expression is the same as the named type.
4288 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4289 prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
4297 <p><small><a name="note89" href="#note89">89)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4298 unqualified version of the type.
4301 <h4><a name="6.5.5" href="#6.5.5">6.5.5 Multiplicative operators</a></h4>
4305 multiplicative-expression:
4307 multiplicative-expression * cast-expression
4308 multiplicative-expression / cast-expression
4309 multiplicative-expression % cast-expression</pre>
4310 <h6>Constraints</h6>
4312 Each of the operands shall have arithmetic type. The operands of the % operator shall
4316 The usual arithmetic conversions are performed on the operands.
4318 The result of the binary * operator is the product of the operands.
4320 The result of the / operator is the quotient from the division of the first operand by the
4321 second; the result of the % operator is the remainder. In both operations, if the value of
4322 the second operand is zero, the behavior is undefined.
4324 When integers are divided, the result of the / operator is the algebraic quotient with any
4325 fractional part discarded.<sup><a href="#note90"><b>90)</b></a></sup> If the quotient a/b is representable, the expression
4326 (a/b)*b + a%b shall equal a.
4329 <p><small><a name="note90" href="#note90">90)</a> This is often called ''truncation toward zero''.
4332 <h4><a name="6.5.6" href="#6.5.6">6.5.6 Additive operators</a></h4>
4336 additive-expression:
4337 multiplicative-expression
4338 additive-expression + multiplicative-expression
4339 additive-expression - multiplicative-expression</pre>
4340 <h6>Constraints</h6>
4342 For addition, either both operands shall have arithmetic type, or one operand shall be a
4343 pointer to an object type and the other shall have integer type. (Incrementing is
4344 equivalent to adding 1.)
4346 For subtraction, one of the following shall hold:
4348 <li> both operands have arithmetic type;
4353 <li> both operands are pointers to qualified or unqualified versions of compatible object
4355 <li> the left operand is a pointer to an object type and the right operand has integer type.
4357 (Decrementing is equivalent to subtracting 1.)
4360 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4363 The result of the binary + operator is the sum of the operands.
4365 The result of the binary - operator is the difference resulting from the subtraction of the
4366 second operand from the first.
4368 For the purposes of these operators, a pointer to an object that is not an element of an
4369 array behaves the same as a pointer to the first element of an array of length one with the
4370 type of the object as its element type.
4372 When an expression that has integer type is added to or subtracted from a pointer, the
4373 result has the type of the pointer operand. If the pointer operand points to an element of
4374 an array object, and the array is large enough, the result points to an element offset from
4375 the original element such that the difference of the subscripts of the resulting and original
4376 array elements equals the integer expression. In other words, if the expression P points to
4377 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4378 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4379 the array object, provided they exist. Moreover, if the expression P points to the last
4380 element of an array object, the expression (P)+1 points one past the last element of the
4381 array object, and if the expression Q points one past the last element of an array object,
4382 the expression (Q)-1 points to the last element of the array object. If both the pointer
4383 operand and the result point to elements of the same array object, or one past the last
4384 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4385 behavior is undefined. If the result points one past the last element of the array object, it
4386 shall not be used as the operand of a unary * operator that is evaluated.
4388 When two pointers are subtracted, both shall point to elements of the same array object,
4389 or one past the last element of the array object; the result is the difference of the
4390 subscripts of the two array elements. The size of the result is implementation-defined,
4391 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.17"><stddef.h></a> header.
4392 If the result is not representable in an object of that type, the behavior is undefined. In
4393 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4394 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4395 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4396 an array object or one past the last element of an array object, and the expression Q points
4397 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4399 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4400 expression P points one past the last element of the array object, even though the
4401 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note91"><b>91)</b></a></sup>
4403 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4409 int (*p)[m] = a; // p == &a[0]
4410 p += 1; // p == &a[1]
4411 (*p)[2] = 99; // a[1][2] == 99
4412 n = p - a; // n == 1
4414 If array a in the above example were declared to be an array of known constant size, and pointer p were
4415 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4418 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), common definitions <a href="#7.17"><stddef.h></a>
4419 (<a href="#7.17">7.17</a>).
4422 <p><small><a name="note91" href="#note91">91)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4423 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4424 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4425 original type. For pointer subtraction, the result of the difference between the character pointers is
4426 similarly divided by the size of the object originally pointed to.
4427 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4428 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4429 element'' requirements.
4432 <h4><a name="6.5.7" href="#6.5.7">6.5.7 Bitwise shift operators</a></h4>
4438 shift-expression << additive-expression
4439 shift-expression >> additive-expression</pre>
4440 <h6>Constraints</h6>
4442 Each of the operands shall have integer type.
4445 The integer promotions are performed on each of the operands. The type of the result is
4446 that of the promoted left operand. If the value of the right operand is negative or is
4447 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4454 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4455 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4456 one more than the maximum value representable in the result type. If E1 has a signed
4457 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4458 the resulting value; otherwise, the behavior is undefined.
4460 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4461 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4462 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4463 resulting value is implementation-defined.
4465 <h4><a name="6.5.8" href="#6.5.8">6.5.8 Relational operators</a></h4>
4469 relational-expression:
4471 relational-expression < shift-expression
4472 relational-expression > shift-expression
4473 relational-expression <= shift-expression
4474 relational-expression >= shift-expression</pre>
4475 <h6>Constraints</h6>
4477 One of the following shall hold:
4479 <li> both operands have real type;
4480 <li> both operands are pointers to qualified or unqualified versions of compatible object
4482 <li> both operands are pointers to qualified or unqualified versions of compatible
4487 If both of the operands have arithmetic type, the usual arithmetic conversions are
4490 For the purposes of these operators, a pointer to an object that is not an element of an
4491 array behaves the same as a pointer to the first element of an array of length one with the
4492 type of the object as its element type.
4494 When two pointers are compared, the result depends on the relative locations in the
4495 address space of the objects pointed to. If two pointers to object or incomplete types both
4496 point to the same object, or both point one past the last element of the same array object,
4497 they compare equal. If the objects pointed to are members of the same aggregate object,
4498 pointers to structure members declared later compare greater than pointers to members
4499 declared earlier in the structure, and pointers to array elements with larger subscript
4501 values compare greater than pointers to elements of the same array with lower subscript
4502 values. All pointers to members of the same union object compare equal. If the
4503 expression P points to an element of an array object and the expression Q points to the
4504 last element of the same array object, the pointer expression Q+1 compares greater than
4505 P. In all other cases, the behavior is undefined.
4507 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4508 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.<sup><a href="#note92"><b>92)</b></a></sup>
4509 The result has type int.
4512 <p><small><a name="note92" href="#note92">92)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4513 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4516 <h4><a name="6.5.9" href="#6.5.9">6.5.9 Equality operators</a></h4>
4520 equality-expression:
4521 relational-expression
4522 equality-expression == relational-expression
4523 equality-expression != relational-expression</pre>
4524 <h6>Constraints</h6>
4526 One of the following shall hold:
4528 <li> both operands have arithmetic type;
4529 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4530 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4531 qualified or unqualified version of void; or
4532 <li> one operand is a pointer and the other is a null pointer constant.
4536 The == (equal to) and != (not equal to) operators are analogous to the relational
4537 operators except for their lower precedence.<sup><a href="#note93"><b>93)</b></a></sup> Each of the operators yields 1 if the
4538 specified relation is true and 0 if it is false. The result has type int. For any pair of
4539 operands, exactly one of the relations is true.
4541 If both of the operands have arithmetic type, the usual arithmetic conversions are
4542 performed. Values of complex types are equal if and only if both their real parts are equal
4543 and also their imaginary parts are equal. Any two values of arithmetic types from
4544 different type domains are equal if and only if the results of their conversions to the
4545 (complex) result type determined by the usual arithmetic conversions are equal.
4550 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4551 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4552 one operand is a pointer to an object or incomplete type and the other is a pointer to a
4553 qualified or unqualified version of void, the former is converted to the type of the latter.
4555 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4556 same object (including a pointer to an object and a subobject at its beginning) or function,
4557 both are pointers to one past the last element of the same array object, or one is a pointer
4558 to one past the end of one array object and the other is a pointer to the start of a different
4559 array object that happens to immediately follow the first array object in the address
4560 space.<sup><a href="#note94"><b>94)</b></a></sup>
4562 For the purposes of these operators, a pointer to an object that is not an element of an
4563 array behaves the same as a pointer to the first element of an array of length one with the
4564 type of the object as its element type.
4567 <p><small><a name="note93" href="#note93">93)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4569 <p><small><a name="note94" href="#note94">94)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4570 adjacent members of a structure with no padding between them, or because the implementation chose
4571 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4572 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4576 <h4><a name="6.5.10" href="#6.5.10">6.5.10 Bitwise AND operator</a></h4>
4582 AND-expression & equality-expression</pre>
4583 <h6>Constraints</h6>
4585 Each of the operands shall have integer type.
4588 The usual arithmetic conversions are performed on the operands.
4590 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4591 the result is set if and only if each of the corresponding bits in the converted operands is
4599 <h4><a name="6.5.11" href="#6.5.11">6.5.11 Bitwise exclusive OR operator</a></h4>
4603 exclusive-OR-expression:
4605 exclusive-OR-expression ^ AND-expression</pre>
4606 <h6>Constraints</h6>
4608 Each of the operands shall have integer type.
4611 The usual arithmetic conversions are performed on the operands.
4613 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4614 in the result is set if and only if exactly one of the corresponding bits in the converted
4617 <h4><a name="6.5.12" href="#6.5.12">6.5.12 Bitwise inclusive OR operator</a></h4>
4621 inclusive-OR-expression:
4622 exclusive-OR-expression
4623 inclusive-OR-expression | exclusive-OR-expression</pre>
4624 <h6>Constraints</h6>
4626 Each of the operands shall have integer type.
4629 The usual arithmetic conversions are performed on the operands.
4631 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4632 the result is set if and only if at least one of the corresponding bits in the converted
4636 <h4><a name="6.5.13" href="#6.5.13">6.5.13 Logical AND operator</a></h4>
4640 logical-AND-expression:
4641 inclusive-OR-expression
4642 logical-AND-expression && inclusive-OR-expression</pre>
4643 <h6>Constraints</h6>
4645 Each of the operands shall have scalar type.
4648 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4649 yields 0. The result has type int.
4651 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4652 there is a sequence point after the evaluation of the first operand. If the first operand
4653 compares equal to 0, the second operand is not evaluated.
4655 <h4><a name="6.5.14" href="#6.5.14">6.5.14 Logical OR operator</a></h4>
4659 logical-OR-expression:
4660 logical-AND-expression
4661 logical-OR-expression || logical-AND-expression</pre>
4662 <h6>Constraints</h6>
4664 Each of the operands shall have scalar type.
4667 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4668 yields 0. The result has type int.
4670 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
4671 a sequence point after the evaluation of the first operand. If the first operand compares
4672 unequal to 0, the second operand is not evaluated.
4675 <h4><a name="6.5.15" href="#6.5.15">6.5.15 Conditional operator</a></h4>
4679 conditional-expression:
4680 logical-OR-expression
4681 logical-OR-expression ? expression : conditional-expression</pre>
4682 <h6>Constraints</h6>
4684 The first operand shall have scalar type.
4686 One of the following shall hold for the second and third operands:
4688 <li> both operands have arithmetic type;
4689 <li> both operands have the same structure or union type;
4690 <li> both operands have void type;
4691 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4692 <li> one operand is a pointer and the other is a null pointer constant; or
4693 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4694 qualified or unqualified version of void.
4698 The first operand is evaluated; there is a sequence point after its evaluation. The second
4699 operand is evaluated only if the first compares unequal to 0; the third operand is evaluated
4700 only if the first compares equal to 0; the result is the value of the second or third operand
4701 (whichever is evaluated), converted to the type described below.<sup><a href="#note95"><b>95)</b></a></sup> If an attempt is made
4702 to modify the result of a conditional operator or to access it after the next sequence point,
4703 the behavior is undefined.
4705 If both the second and third operands have arithmetic type, the result type that would be
4706 determined by the usual arithmetic conversions, were they applied to those two operands,
4707 is the type of the result. If both the operands have structure or union type, the result has
4708 that type. If both operands have void type, the result has void type.
4710 If both the second and third operands are pointers or one is a null pointer constant and the
4711 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4712 of the types pointed-to by both operands. Furthermore, if both operands are pointers to
4713 compatible types or to differently qualified versions of compatible types, the result type is
4714 a pointer to an appropriately qualified version of the composite type; if one operand is a
4715 null pointer constant, the result has the type of the other operand; otherwise, one operand
4716 is a pointer to void or a qualified version of void, in which case the result type is a
4719 pointer to an appropriately qualified version of void.
4721 EXAMPLE The common type that results when the second and third operands are pointers is determined
4722 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4723 pointers have compatible types.
4725 Given the declarations
4732 const char *c_cp;</pre>
4733 the third column in the following table is the common type that is the result of a conditional expression in
4734 which the first two columns are the second and third operands (in either order):
4736 c_vp c_ip const void *
4737 v_ip 0 volatile int *
4738 c_ip v_ip const volatile int *
4739 vp c_cp const void *
4745 <p><small><a name="note95" href="#note95">95)</a> A conditional expression does not yield an lvalue.
4748 <h4><a name="6.5.16" href="#6.5.16">6.5.16 Assignment operators</a></h4>
4752 assignment-expression:
4753 conditional-expression
4754 unary-expression assignment-operator assignment-expression
4755 assignment-operator: one of
4756 = *= /= %= += -= <<= >>= &= ^= |=</pre>
4757 <h6>Constraints</h6>
4759 An assignment operator shall have a modifiable lvalue as its left operand.
4762 An assignment operator stores a value in the object designated by the left operand. An
4763 assignment expression has the value of the left operand after the assignment, but is not an
4764 lvalue. The type of an assignment expression is the type of the left operand unless the
4765 left operand has qualified type, in which case it is the unqualified version of the type of
4766 the left operand. The side effect of updating the stored value of the left operand shall
4767 occur between the previous and the next sequence point.
4769 The order of evaluation of the operands is unspecified. If an attempt is made to modify
4770 the result of an assignment operator or to access it after the next sequence point, the
4771 behavior is undefined.
4774 <h5><a name="6.5.16.1" href="#6.5.16.1">6.5.16.1 Simple assignment</a></h5>
4775 <h6>Constraints</h6>
4777 One of the following shall hold:<sup><a href="#note96"><b>96)</b></a></sup>
4779 <li> the left operand has qualified or unqualified arithmetic type and the right has
4781 <li> the left operand has a qualified or unqualified version of a structure or union type
4782 compatible with the type of the right;
4783 <li> both operands are pointers to qualified or unqualified versions of compatible types,
4784 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4786 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4787 qualified or unqualified version of void, and the type pointed to by the left has all
4788 the qualifiers of the type pointed to by the right;
4789 <li> the left operand is a pointer and the right is a null pointer constant; or
4790 <li> the left operand has type _Bool and the right is a pointer.
4794 In simple assignment (=), the value of the right operand is converted to the type of the
4795 assignment expression and replaces the value stored in the object designated by the left
4798 If the value being stored in an object is read from another object that overlaps in any way
4799 the storage of the first object, then the overlap shall be exact and the two objects shall
4800 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4803 EXAMPLE 1 In the program fragment
4808 if ((c = f()) == -1)
4810 the int value returned by the function may be truncated when stored in the char, and then converted back
4811 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4812 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4817 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4818 variable c should be declared as int.
4821 EXAMPLE 2 In the fragment:
4827 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4828 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4829 that is, long int type.
4832 EXAMPLE 3 Consider the fragment:
4837 cpp = &p; // constraint violation
4838 *cpp = &c; // valid
4839 *p = 0; // valid</pre>
4840 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4841 value of the const object c.
4845 <p><small><a name="note96" href="#note96">96)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
4846 (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
4847 qualifiers that were applied to the type category of the expression (for example, it removes const but
4848 not volatile from the type int volatile * const).
4851 <h5><a name="6.5.16.2" href="#6.5.16.2">6.5.16.2 Compound assignment</a></h5>
4852 <h6>Constraints</h6>
4854 For the operators += and -= only, either the left operand shall be a pointer to an object
4855 type and the right shall have integer type, or the left operand shall have qualified or
4856 unqualified arithmetic type and the right shall have arithmetic type.
4858 For the other operators, each operand shall have arithmetic type consistent with those
4859 allowed by the corresponding binary operator.
4862 A compound assignment of the form E1 op = E2 differs from the simple assignment
4863 expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
4866 <h4><a name="6.5.17" href="#6.5.17">6.5.17 Comma operator</a></h4>
4871 assignment-expression
4872 expression , assignment-expression</pre>
4875 The left operand of a comma operator is evaluated as a void expression; there is a
4876 sequence point after its evaluation. Then the right operand is evaluated; the result has its
4877 type and value.<sup><a href="#note97"><b>97)</b></a></sup> If an attempt is made to modify the result of a comma operator or to
4878 access it after the next sequence point, the behavior is undefined.
4880 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4881 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4882 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4883 expression of a conditional operator in such contexts. In the function call
4885 f(a, (t=3, t+2), c)</pre>
4886 the function has three arguments, the second of which has the value 5.
4888 <p><b> Forward references</b>: initialization (<a href="#6.7.8">6.7.8</a>).
4896 <p><small><a name="note97" href="#note97">97)</a> A comma operator does not yield an lvalue.
4899 <h3><a name="6.6" href="#6.6">6.6 Constant expressions</a></h3>
4903 constant-expression:
4904 conditional-expression</pre>
4905 <h6>Description</h6>
4907 A constant expression can be evaluated during translation rather than runtime, and
4908 accordingly may be used in any place that a constant may be.
4909 <h6>Constraints</h6>
4911 Constant expressions shall not contain assignment, increment, decrement, function-call,
4912 or comma operators, except when they are contained within a subexpression that is not
4913 evaluated.<sup><a href="#note98"><b>98)</b></a></sup>
4915 Each constant expression shall evaluate to a constant that is in the range of representable
4916 values for its type.
4919 An expression that evaluates to a constant is required in several contexts. If a floating
4920 expression is evaluated in the translation environment, the arithmetic precision and range
4921 shall be at least as great as if the expression were being evaluated in the execution
4924 An integer constant expression<sup><a href="#note99"><b>99)</b></a></sup> shall have integer type and shall only have operands
4925 that are integer constants, enumeration constants, character constants, sizeof
4926 expressions whose results are integer constants, and floating constants that are the
4927 immediate operands of casts. Cast operators in an integer constant expression shall only
4928 convert arithmetic types to integer types, except as part of an operand to the sizeof
4931 More latitude is permitted for constant expressions in initializers. Such a constant
4932 expression shall be, or evaluate to, one of the following:
4934 <li> an arithmetic constant expression,
4935 <li> a null pointer constant,
4941 <li> an address constant, or
4942 <li> an address constant for an object type plus or minus an integer constant expression.
4945 An arithmetic constant expression shall have arithmetic type and shall only have
4946 operands that are integer constants, floating constants, enumeration constants, character
4947 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4948 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4949 sizeof operator whose result is an integer constant.
4951 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4952 storage duration, or a pointer to a function designator; it shall be created explicitly using
4953 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4954 an expression of array or function type. The array-subscript [] and member-access .
4955 and -> operators, the address & and indirection * unary operators, and pointer casts may
4956 be used in the creation of an address constant, but the value of an object shall not be
4957 accessed by use of these operators.
4959 An implementation may accept other forms of constant expressions.
4961 The semantic rules for the evaluation of a constant expression are the same as for
4962 nonconstant expressions.<sup><a href="#note100"><b>100)</b></a></sup>
4963 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4971 <p><small><a name="note98" href="#note98">98)</a> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
4973 <p><small><a name="note99" href="#note99">99)</a> An integer constant expression is used to specify the size of a bit-field member of a structure, the
4974 value of an enumeration constant, the size of an array, or the value of a case constant. Further
4975 constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
4976 directives are discussed in <a href="#6.10.1">6.10.1</a>.
4978 <p><small><a name="note100" href="#note100">100)</a> Thus, in the following initialization,
4981 static int i = 2 || 1 / 0;</pre>
4982 the expression is a valid integer constant expression with value one.
4985 <h3><a name="6.7" href="#6.7">6.7 Declarations</a></h3>
4990 declaration-specifiers init-declarator-list<sub>opt</sub> ;
4991 declaration-specifiers:
4992 storage-class-specifier declaration-specifiers<sub>opt</sub>
4993 type-specifier declaration-specifiers<sub>opt</sub>
4994 type-qualifier declaration-specifiers<sub>opt</sub>
4995 function-specifier declaration-specifiers<sub>opt</sub>
4996 init-declarator-list:
4998 init-declarator-list , init-declarator
5001 declarator = initializer</pre>
5002 <h6>Constraints</h6>
5004 A declaration shall declare at least a declarator (other than the parameters of a function or
5005 the members of a structure or union), a tag, or the members of an enumeration.
5007 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5008 (in a declarator or type specifier) with the same scope and in the same name space, except
5009 for tags as specified in <a href="#6.7.2.3">6.7.2.3</a>.
5011 All declarations in the same scope that refer to the same object or function shall specify
5015 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
5016 of an identifier is a declaration for that identifier that:
5018 <li> for an object, causes storage to be reserved for that object;
5019 <li> for a function, includes the function body;<sup><a href="#note101"><b>101)</b></a></sup>
5020 <li> for an enumeration constant or typedef name, is the (only) declaration of the
5024 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
5025 storage duration, and part of the type of the entities that the declarators denote. The init-
5026 declarator-list is a comma-separated sequence of declarators, each of which may have
5029 additional type information, or an initializer, or both. The declarators contain the
5030 identifiers (if any) being declared.
5032 If an identifier for an object is declared with no linkage, the type for the object shall be
5033 complete by the end of its declarator, or by the end of its init-declarator if it has an
5034 initializer; in the case of function parameters (including in prototypes), it is the adjusted
5035 type (see <a href="#6.7.5.3">6.7.5.3</a>) that is required to be complete.
5036 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
5037 (<a href="#6.7.8">6.7.8</a>).
5040 <p><small><a name="note101" href="#note101">101)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
5043 <h4><a name="6.7.1" href="#6.7.1">6.7.1 Storage-class specifiers</a></h4>
5047 storage-class-specifier:
5053 <h6>Constraints</h6>
5055 At most, one storage-class specifier may be given in the declaration specifiers in a
5056 declaration.<sup><a href="#note102"><b>102)</b></a></sup>
5059 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
5060 only; it is discussed in <a href="#6.7.7">6.7.7</a>. The meanings of the various linkages and storage durations
5061 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
5063 A declaration of an identifier for an object with storage-class specifier register
5064 suggests that access to the object be as fast as possible. The extent to which such
5065 suggestions are effective is implementation-defined.<sup><a href="#note103"><b>103)</b></a></sup>
5067 The declaration of an identifier for a function that has block scope shall have no explicit
5068 storage-class specifier other than extern.
5074 If an aggregate or union object is declared with a storage-class specifier other than
5075 typedef, the properties resulting from the storage-class specifier, except with respect to
5076 linkage, also apply to the members of the object, and so on recursively for any aggregate
5077 or union member objects.
5078 <p><b> Forward references</b>: type definitions (<a href="#6.7.7">6.7.7</a>).
5081 <p><small><a name="note102" href="#note102">102)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
5083 <p><small><a name="note103" href="#note103">103)</a> The implementation may treat any register declaration simply as an auto declaration. However,
5084 whether or not addressable storage is actually used, the address of any part of an object declared with
5085 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5086 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
5087 <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operator that can be applied to an array declared with storage-class specifier
5091 <h4><a name="6.7.2" href="#6.7.2">6.7.2 Type specifiers</a></h4>
5107 struct-or-union-specifier *
5110 <h6>Constraints</h6>
5112 At least one type specifier shall be given in the declaration specifiers in each declaration,
5113 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5114 type specifiers shall be one of the following sets (delimited by commas, when there is
5115 more than one set on a line); the type specifiers may occur in any order, possibly
5116 intermixed with the other declaration specifiers.
5122 <li> short, signed short, short int, or signed short int
5123 <li> unsigned short, or unsigned short int
5124 <li> int, signed, or signed int
5126 <li> unsigned, or unsigned int
5127 <li> long, signed long, long int, or signed long int
5128 <li> unsigned long, or unsigned long int
5129 <li> long long, signed long long, long long int, or
5130 signed long long int
5131 <li> unsigned long long, or unsigned long long int
5137 <li> double _Complex
5138 <li> long double _Complex
5139 <li> struct or union specifier *
5144 The type specifier _Complex shall not be used if the implementation does not provide
5145 complex types.<sup><a href="#note104"><b>104)</b></a></sup>
5148 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5149 <a href="#6.7.2.3">6.7.2.3</a>. Declarations of typedef names are discussed in <a href="#6.7.7">6.7.7</a>. The characteristics of the
5150 other types are discussed in <a href="#6.2.5">6.2.5</a>.
5152 Each of the comma-separated sets designates the same type, except that for bit-fields, it is
5153 implementation-defined whether the specifier int designates the same type as signed
5154 int or the same type as unsigned int.
5155 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5156 (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5164 <p><small><a name="note104" href="#note104">104)</a> Freestanding implementations are not required to provide complex types. *
5167 <h5><a name="6.7.2.1" href="#6.7.2.1">6.7.2.1 Structure and union specifiers</a></h5>
5171 struct-or-union-specifier:
5172 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
5173 struct-or-union identifier
5177 struct-declaration-list:
5179 struct-declaration-list struct-declaration
5181 specifier-qualifier-list struct-declarator-list ;
5182 specifier-qualifier-list:
5183 type-specifier specifier-qualifier-list<sub>opt</sub>
5184 type-qualifier specifier-qualifier-list<sub>opt</sub>
5185 struct-declarator-list:
5187 struct-declarator-list , struct-declarator
5190 declarator<sub>opt</sub> : constant-expression</pre>
5191 <h6>Constraints</h6>
5193 A structure or union shall not contain a member with incomplete or function type (hence,
5194 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5195 of itself), except that the last member of a structure with more than one named member
5196 may have incomplete array type; such a structure (and any union containing, possibly
5197 recursively, a member that is such a structure) shall not be a member of a structure or an
5198 element of an array.
5200 The expression that specifies the width of a bit-field shall be an integer constant
5201 expression with a nonnegative value that does not exceed the width of an object of the
5202 type that would be specified were the colon and expression omitted. If the value is zero,
5203 the declaration shall have no declarator.
5205 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5206 int, unsigned int, or some other implementation-defined type.
5210 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
5211 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5212 of members whose storage overlap.
5214 Structure and union specifiers have the same form. The keywords struct and union
5215 indicate that the type being specified is, respectively, a structure type or a union type.
5217 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5218 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5219 members of the structure or union. If the struct-declaration-list contains no named
5220 members, the behavior is undefined. The type is incomplete until after the } that
5221 terminates the list.
5223 A member of a structure or union may have any object type other than a variably
5224 modified type.<sup><a href="#note105"><b>105)</b></a></sup> In addition, a member may be declared to consist of a specified
5225 number of bits (including a sign bit, if any). Such a member is called a bit-field;<sup><a href="#note106"><b>106)</b></a></sup> its
5226 width is preceded by a colon.
5228 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5229 number of bits.<sup><a href="#note107"><b>107)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of type
5230 _Bool, the value of the bit-field shall compare equal to the value stored.
5232 An implementation may allocate any addressable storage unit large enough to hold a bit-
5233 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5234 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5235 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5236 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5237 low-order or low-order to high-order) is implementation-defined. The alignment of the
5238 addressable storage unit is unspecified.
5240 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5241 unnamed bit-field.<sup><a href="#note108"><b>108)</b></a></sup> As a special case, a bit-field structure member with a width of 0
5242 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5243 field, if any, was placed.
5248 Each non-bit-field member of a structure or union object is aligned in an implementation-
5249 defined manner appropriate to its type.
5251 Within a structure object, the non-bit-field members and the units in which bit-fields
5252 reside have addresses that increase in the order in which they are declared. A pointer to a
5253 structure object, suitably converted, points to its initial member (or if that member is a
5254 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5255 padding within a structure object, but not at its beginning.
5257 The size of a union is sufficient to contain the largest of its members. The value of at
5258 most one of the members can be stored in a union object at any time. A pointer to a
5259 union object, suitably converted, points to each of its members (or if a member is a bit-
5260 field, then to the unit in which it resides), and vice versa.
5262 There may be unnamed padding at the end of a structure or union.
5264 As a special case, the last element of a structure with more than one named member may
5265 have an incomplete array type; this is called a flexible array member. In most situations,
5266 the flexible array member is ignored. In particular, the size of the structure is as if the
5267 flexible array member were omitted except that it may have more trailing padding than
5268 the omission would imply. However, when a . (or ->) operator has a left operand that is
5269 (a pointer to) a structure with a flexible array member and the right operand names that
5270 member, it behaves as if that member were replaced with the longest array (with the same
5271 element type) that would not make the structure larger than the object being accessed; the
5272 offset of the array shall remain that of the flexible array member, even if this would differ
5273 from that of the replacement array. If this array would have no elements, it behaves as if
5274 it had one element but the behavior is undefined if any attempt is made to access that
5275 element or to generate a pointer one past it.
5277 EXAMPLE After the declaration:
5279 struct s { int n; double d[]; };</pre>
5280 the structure struct s has a flexible array member d. A typical way to use this is:
5282 int m = /* some value */;
5283 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));</pre>
5284 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5285 p had been declared as:
5287 struct { int n; double d[m]; } *p;</pre>
5288 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5291 Following the above declaration:
5294 struct s t1 = { 0 }; // valid
5295 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
5297 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior</pre>
5298 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5299 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5301 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)</pre>
5302 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5305 After the further declaration:
5307 struct ss { int n; };</pre>
5310 sizeof (struct s) >= sizeof (struct ss)
5311 sizeof (struct s) >= offsetof(struct s, d)</pre>
5312 are always equal to 1.
5314 If sizeof (double) is 8, then after the following code is executed:
5318 s1 = malloc(sizeof (struct s) + 64);
5319 s2 = malloc(sizeof (struct s) + 46);</pre>
5320 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5321 purposes, as if the identifiers had been declared as:
5324 struct { int n; double d[8]; } *s1;
5325 struct { int n; double d[5]; } *s2;</pre>
5326 Following the further successful assignments:
5328 s1 = malloc(sizeof (struct s) + 10);
5329 s2 = malloc(sizeof (struct s) + 6);</pre>
5330 they then behave as if the declarations were:
5332 struct { int n; double d[1]; } *s1, *s2;</pre>
5337 dp = &(s1->d[0]); // valid
5339 dp = &(s2->d[0]); // valid
5340 *dp = 42; // undefined behavior</pre>
5344 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5345 of the structure, they might be copied or simply overwritten with indeterminate values.
5347 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5351 <p><small><a name="note105" href="#note105">105)</a> A structure or union can not contain a member with a variably modified type because member names
5352 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
5354 <p><small><a name="note106" href="#note106">106)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5355 or arrays of bit-field objects.
5357 <p><small><a name="note107" href="#note107">107)</a> As specified in <a href="#6.7.2">6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int,
5358 then it is implementation-defined whether the bit-field is signed or unsigned.
5360 <p><small><a name="note108" href="#note108">108)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5364 <h5><a name="6.7.2.2" href="#6.7.2.2">6.7.2.2 Enumeration specifiers</a></h5>
5369 enum identifier<sub>opt</sub> { enumerator-list }
5370 enum identifier<sub>opt</sub> { enumerator-list , }
5374 enumerator-list , enumerator
5376 enumeration-constant
5377 enumeration-constant = constant-expression</pre>
5378 <h6>Constraints</h6>
5380 The expression that defines the value of an enumeration constant shall be an integer
5381 constant expression that has a value representable as an int.
5384 The identifiers in an enumerator list are declared as constants that have type int and
5385 may appear wherever such are permitted.<sup><a href="#note109"><b>109)</b></a></sup> An enumerator with = defines its
5386 enumeration constant as the value of the constant expression. If the first enumerator has
5387 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5388 defines its enumeration constant as the value of the constant expression obtained by
5389 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5390 = may produce enumeration constants with values that duplicate other values in the same
5391 enumeration.) The enumerators of an enumeration are also known as its members.
5393 Each enumerated type shall be compatible with char, a signed integer type, or an
5394 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note110"><b>110)</b></a></sup> but shall be
5395 capable of representing the values of all the members of the enumeration. The
5396 enumerated type is incomplete until after the } that terminates the list of enumerator
5404 EXAMPLE The following fragment:
5406 enum hue { chartreuse, burgundy, claret=20, winedark };
5410 if (*cp != burgundy)
5412 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5413 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5415 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5418 <p><small><a name="note109" href="#note109">109)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5419 each other and from other identifiers declared in ordinary declarators.
5421 <p><small><a name="note110" href="#note110">110)</a> An implementation may delay the choice of which integer type until all enumeration constants have
5425 <h5><a name="6.7.2.3" href="#6.7.2.3">6.7.2.3 Tags</a></h5>
5426 <h6>Constraints</h6>
5428 A specific type shall have its content defined at most once.
5430 Where two declarations that use the same tag declare the same type, they shall both use
5431 the same choice of struct, union, or enum.
5433 A type specifier of the form
5435 enum identifier</pre>
5436 without an enumerator list shall only appear after the type it specifies is complete.
5439 All declarations of structure, union, or enumerated types that have the same scope and
5440 use the same tag declare the same type. The type is incomplete<sup><a href="#note111"><b>111)</b></a></sup> until the closing brace
5441 of the list defining the content, and complete thereafter.
5443 Two declarations of structure, union, or enumerated types which are in different scopes or
5444 use different tags declare distinct types. Each declaration of a structure, union, or
5445 enumerated type which does not include a tag declares a distinct type.
5447 A type specifier of the form
5449 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }</pre>
5452 enum identifier { enumerator-list }</pre>
5455 enum identifier { enumerator-list , }</pre>
5456 declares a structure, union, or enumerated type. The list defines the structure content,
5459 union content, or enumeration content. If an identifier is provided,<sup><a href="#note112"><b>112)</b></a></sup> the type specifier
5460 also declares the identifier to be the tag of that type.
5462 A declaration of the form
5464 struct-or-union identifier ;</pre>
5465 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note113"><b>113)</b></a></sup>
5467 If a type specifier of the form
5469 struct-or-union identifier</pre>
5470 occurs other than as part of one of the above forms, and no other declaration of the
5471 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5472 declares the identifier as the tag of that type.113)
5474 If a type specifier of the form
5476 struct-or-union identifier</pre>
5479 enum identifier</pre>
5480 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5481 tag is visible, then it specifies the same type as that other declaration, and does not
5484 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5488 struct tnode *left, *right;
5490 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5491 declaration has been given, the declaration
5493 struct tnode s, *sp;</pre>
5494 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5495 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5496 which sp points; the expression s.right->count designates the count member of the right struct
5497 tnode pointed to from s.
5499 The following alternative formulation uses the typedef mechanism:
5506 typedef struct tnode TNODE;
5509 TNODE *left, *right;
5514 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5515 structures, the declarations
5517 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5518 struct s2 { struct s1 *s1p; /* ... */ }; // D2</pre>
5519 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5520 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5521 D2. To eliminate this context sensitivity, the declaration
5524 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5525 completes the specification of the new type.
5527 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions
5528 (<a href="#6.7.7">6.7.7</a>).
5531 <p><small><a name="note111" href="#note111">111)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
5532 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5533 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5534 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5536 <p><small><a name="note112" href="#note112">112)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5537 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5538 can make use of that typedef name to declare objects having the specified structure, union, or
5541 <p><small><a name="note113" href="#note113">113)</a> A similar construction with enum does not exist.
5544 <h4><a name="6.7.3" href="#6.7.3">6.7.3 Type qualifiers</a></h4>
5552 <h6>Constraints</h6>
5554 Types other than pointer types derived from object or incomplete types shall not be
5558 The properties associated with qualified types are meaningful only for expressions that
5559 are lvalues.<sup><a href="#note114"><b>114)</b></a></sup>
5561 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5562 directly or via one or more typedefs, the behavior is the same as if it appeared only
5570 If an attempt is made to modify an object defined with a const-qualified type through use
5571 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5572 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5573 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note115"><b>115)</b></a></sup>
5575 An object that has volatile-qualified type may be modified in ways unknown to the
5576 implementation or have other unknown side effects. Therefore any expression referring
5577 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5578 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
5579 object shall agree with that prescribed by the abstract machine, except as modified by the
5580 unknown factors mentioned previously.<sup><a href="#note116"><b>116)</b></a></sup> What constitutes an access to an object that
5581 has volatile-qualified type is implementation-defined.
5583 An object that is accessed through a restrict-qualified pointer has a special association
5584 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5585 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note117"><b>117)</b></a></sup> The intended
5586 use of the restrict qualifier (like the register storage class) is to promote
5587 optimization, and deleting all instances of the qualifier from all preprocessing translation
5588 units composing a conforming program does not change its meaning (i.e., observable
5591 If the specification of an array type includes any type qualifiers, the element type is so-
5592 qualified, not the array type. If the specification of a function type includes any type
5593 qualifiers, the behavior is undefined.<sup><a href="#note118"><b>118)</b></a></sup>
5595 For two qualified types to be compatible, both shall have the identically qualified version
5596 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5597 does not affect the specified type.
5599 EXAMPLE 1 An object declared
5601 extern const volatile int real_time_clock;</pre>
5602 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5609 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5610 modify an aggregate type:
5612 const struct s { int mem; } cs = { 1 };
5613 struct s ncs; // the object ncs is modifiable
5614 typedef int A[2][3];
5615 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5619 cs = ncs; // violates modifiable lvalue constraint for =
5620 pi = &ncs.mem; // valid
5621 pi = &cs.mem; // violates type constraints for =
5622 pci = &cs.mem; // valid
5623 pi = a[0]; // invalid: a[0] has type ''const int *''</pre>
5627 <p><small><a name="note114" href="#note114">114)</a> The implementation may place a const object that is not volatile in a read-only region of
5628 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5631 <p><small><a name="note115" href="#note115">115)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
5632 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5635 <p><small><a name="note116" href="#note116">116)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5636 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5637 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5638 permitted by the rules for evaluating expressions.
5640 <p><small><a name="note117" href="#note117">117)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5641 association between the allocated object and the pointer.
5643 <p><small><a name="note118" href="#note118">118)</a> Both of these can occur through the use of typedefs.
5646 <h5><a name="6.7.3.1" href="#6.7.3.1">6.7.3.1 Formal definition of restrict</a></h5>
5648 Let D be a declaration of an ordinary identifier that provides a means of designating an
5649 object P as a restrict-qualified pointer to type T.
5651 If D appears inside a block and does not have storage class extern, let B denote the
5652 block. If D appears in the list of parameter declarations of a function definition, let B
5653 denote the associated block. Otherwise, let B denote the block of main (or the block of
5654 whatever function is called at program startup in a freestanding environment).
5656 In what follows, a pointer expression E is said to be based on object P if (at some
5657 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5658 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note119"><b>119)</b></a></sup>
5659 Note that ''based'' is defined only for expressions with pointer types.
5661 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5662 access the value of the object X that it designates, and X is also modified (by any means),
5663 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5664 used to access the value of X shall also have its address based on P. Every access that
5665 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5666 is assigned the value of a pointer expression E that is based on another restricted pointer
5667 object P2, associated with block B2, then either the execution of B2 shall begin before
5668 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5669 requirements are not met, then the behavior is undefined.
5671 Here an execution of B means that portion of the execution of the program that would
5672 correspond to the lifetime of an object with scalar type and automatic storage duration
5677 A translator is free to ignore any or all aliasing implications of uses of restrict.
5679 EXAMPLE 1 The file scope declarations
5683 extern int c[];</pre>
5684 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5685 program, then it is never accessed using either of the other two.
5688 EXAMPLE 2 The function parameter declarations in the following example
5690 void f(int n, int * restrict p, int * restrict q)
5695 assert that, during each execution of the function, if an object is accessed through one of the pointer
5696 parameters, then it is not also accessed through the other.
5698 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5699 analysis of function f without examining any of the calls of f in the program. The cost is that the
5700 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5701 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5707 f(50, d + 50, d); // valid
5708 f(50, d + 1, d); // undefined behavior
5712 EXAMPLE 3 The function parameter declarations
5714 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5717 for (i = 0; i < n; i++)
5720 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5721 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5722 modified within function h.
5725 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5726 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5727 between restricted pointers declared in nested blocks have defined behavior.
5734 p1 = q1; // undefined behavior
5736 int * restrict p2 = p1; // valid
5737 int * restrict q2 = q1; // valid
5738 p1 = q2; // undefined behavior
5739 p2 = q2; // undefined behavior
5742 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5743 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5744 example, this permits new_vector to return a vector.
5746 typedef struct { int n; float * restrict v; } vector;
5747 vector new_vector(int n)
5751 t.v = malloc(n * sizeof (float));
5757 <p><small><a name="note119" href="#note119">119)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
5758 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5759 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5760 expressions *p and p[1] are not.
5763 <h4><a name="6.7.4" href="#6.7.4">6.7.4 Function specifiers</a></h4>
5769 <h6>Constraints</h6>
5771 Function specifiers shall be used only in the declaration of an identifier for a function.
5773 An inline definition of a function with external linkage shall not contain a definition of a
5774 modifiable object with static storage duration, and shall not contain a reference to an
5775 identifier with internal linkage.
5777 In a hosted environment, the inline function specifier shall not appear in a declaration
5781 A function declared with an inline function specifier is an inline function. The
5782 function specifier may appear more than once; the behavior is the same as if it appeared
5783 only once. Making a function an inline function suggests that calls to the function be as
5784 fast as possible.<sup><a href="#note120"><b>120)</b></a></sup> The extent to which such suggestions are effective is
5785 implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
5787 Any function with internal linkage can be an inline function. For a function with external
5788 linkage, the following restrictions apply: If a function is declared with an inline
5790 function specifier, then it shall also be defined in the same translation unit. If all of the
5791 file scope declarations for a function in a translation unit include the inline function
5792 specifier without extern, then the definition in that translation unit is an inline
5793 definition. An inline definition does not provide an external definition for the function,
5794 and does not forbid an external definition in another translation unit. An inline definition
5795 provides an alternative to an external definition, which a translator may use to implement
5796 any call to the function in the same translation unit. It is unspecified whether a call to the
5797 function uses the inline definition or the external definition.<sup><a href="#note122"><b>122)</b></a></sup>
5799 EXAMPLE The declaration of an inline function with external linkage can result in either an external
5800 definition, or a definition available for use only within the translation unit. A file scope declaration with
5801 extern creates an external definition. The following example shows an entire translation unit.
5804 inline double fahr(double t)
5806 return (9.0 * t) / 5.0 + 32.0;
5808 inline double cels(double t)
5810 return (5.0 * (t - 32.0)) / 9.0;
5812 extern double fahr(double); // creates an external definition
5813 double convert(int is_fahr, double temp)
5815 /* A translator may perform inline substitutions */
5816 return is_fahr ? cels(temp) : fahr(temp);
5818 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5819 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5820 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5821 definition are distinct and either may be used for the call.
5823 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
5829 <p><small><a name="note120" href="#note120">120)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
5830 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5831 Therefore, for example, the expansion of a macro used within the body of the function uses the
5832 definition it had at the point the function body appears, and not where the function is called; and
5833 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5834 single address, regardless of the number of inline definitions that occur in addition to the external
5837 <p><small><a name="note121" href="#note121">121)</a> For example, an implementation might never perform inline substitution, or might only perform inline
5838 substitutions to calls in the scope of an inline declaration.
5840 <p><small><a name="note122" href="#note122">122)</a> Since an inline definition is distinct from the corresponding external definition and from any other
5841 corresponding inline definitions in other translation units, all corresponding objects with static storage
5842 duration are also distinct in each of the definitions.
5845 <h4><a name="6.7.5" href="#6.7.5">6.7.5 Declarators</a></h4>
5850 pointer<sub>opt</sub> direct-declarator
5854 direct-declarator [ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
5855 direct-declarator [ static type-qualifier-list<sub>opt</sub> assignment-expression ]
5856 direct-declarator [ type-qualifier-list static assignment-expression ]
5857 direct-declarator [ type-qualifier-list<sub>opt</sub> * ]
5858 direct-declarator ( parameter-type-list )
5859 direct-declarator ( identifier-list<sub>opt</sub> )
5861 * type-qualifier-list<sub>opt</sub>
5862 * type-qualifier-list<sub>opt</sub> pointer
5863 type-qualifier-list:
5865 type-qualifier-list type-qualifier
5866 parameter-type-list:
5868 parameter-list , ...
5870 parameter-declaration
5871 parameter-list , parameter-declaration
5872 parameter-declaration:
5873 declaration-specifiers declarator
5874 declaration-specifiers abstract-declarator<sub>opt</sub>
5877 identifier-list , identifier</pre>
5880 Each declarator declares one identifier, and asserts that when an operand of the same
5881 form as the declarator appears in an expression, it designates a function or object with the
5882 scope, storage duration, and type indicated by the declaration specifiers.
5884 A full declarator is a declarator that is not part of another declarator. The end of a full
5885 declarator is a sequence point. If, in the nested sequence of declarators in a full
5887 declarator, there is a declarator specifying a variable length array type, the type specified
5888 by the full declarator is said to be variably modified. Furthermore, any type derived by
5889 declarator type derivation from a variably modified type is itself variably modified.
5891 In the following subclauses, consider a declaration
5894 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5895 a declarator that contains an identifier ident. The type specified for the identifier ident in
5896 the various forms of declarator is described inductively using this notation.
5898 If, in the declaration ''T D1'', D1 has the form
5901 then the type specified for ident is T .
5903 If, in the declaration ''T D1'', D1 has the form
5906 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5907 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5908 declarators may be altered by parentheses.
5909 <h6> Implementation limits</h6>
5911 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
5912 function declarators that modify an arithmetic, structure, union, or incomplete type, either
5913 directly or via one or more typedefs.
5914 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5916 <h5><a name="6.7.5.1" href="#6.7.5.1">6.7.5.1 Pointer declarators</a></h5>
5919 If, in the declaration ''T D1'', D1 has the form
5921 * type-qualifier-list<sub>opt</sub> D</pre>
5922 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5923 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5924 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5926 For two pointer types to be compatible, both shall be identically qualified and both shall
5927 be pointers to compatible types.
5929 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5930 to a constant value'' and a ''constant pointer to a variable value''.
5933 const int *ptr_to_constant;
5934 int *const constant_ptr;</pre>
5935 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5936 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5937 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5940 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5941 type ''pointer to int''.
5943 typedef int *int_ptr;
5944 const int_ptr constant_ptr;</pre>
5945 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5948 <h5><a name="6.7.5.2" href="#6.7.5.2">6.7.5.2 Array declarators</a></h5>
5949 <h6>Constraints</h6>
5951 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5952 an expression or *. If they delimit an expression (which specifies the size of an array), the
5953 expression shall have an integer type. If the expression is a constant expression, it shall
5954 have a value greater than zero. The element type shall not be an incomplete or function
5955 type. The optional type qualifiers and the keyword static shall appear only in a
5956 declaration of a function parameter with an array type, and then only in the outermost
5957 array type derivation.
5959 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
5960 either block scope and no linkage or function prototype scope. If an identifier is declared
5961 to be an object with static storage duration, it shall not have a variable length array type.
5964 If, in the declaration ''T D1'', D1 has one of the forms:
5966 D[ type-qualifier-list<sub>opt</sub> assignment-expressionopt ]
5967 D[ static type-qualifier-list<sub>opt</sub> assignment-expression ]
5968 D[ type-qualifier-list static assignment-expression ]
5969 D[ type-qualifier-list<sub>opt</sub> * ]</pre>
5970 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5971 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note123"><b>123)</b></a></sup>
5972 (See <a href="#6.7.5.3">6.7.5.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5974 If the size is not present, the array type is an incomplete type. If the size is * instead of
5975 being an expression, the array type is a variable length array type of unspecified size,
5976 which can only be used in declarations with function prototype scope;<sup><a href="#note124"><b>124)</b></a></sup> such arrays are
5977 nonetheless complete types. If the size is an integer constant expression and the element
5980 type has a known constant size, the array type is not a variable length array type;
5981 otherwise, the array type is a variable length array type.
5983 If the size is an expression that is not an integer constant expression: if it occurs in a
5984 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5985 each time it is evaluated it shall have a value greater than zero. The size of each instance
5986 of a variable length array type does not change during its lifetime. Where a size
5987 expression is part of the operand of a sizeof operator and changing the value of the
5988 size expression would not affect the result of the operator, it is unspecified whether or not
5989 the size expression is evaluated.
5991 For two array types to be compatible, both shall have compatible element types, and if
5992 both size specifiers are present, and are integer constant expressions, then both size
5993 specifiers shall have the same constant value. If the two array types are used in a context
5994 which requires them to be compatible, it is undefined behavior if the two size specifiers
5995 evaluate to unequal values.
5999 float fa[11], *afp[17];</pre>
6000 declares an array of float numbers and an array of pointers to float numbers.
6003 EXAMPLE 2 Note the distinction between the declarations
6006 extern int y[];</pre>
6007 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
6008 (an incomplete type), the storage for which is defined elsewhere.
6011 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
6020 int (*r)[n][n][n+1];
6021 p = a; // invalid: not compatible because 4 != 6
6022 r = c; // compatible, but defined behavior only if
6023 // n == 6 and m == n+1
6031 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
6032 function prototype scope. Array objects declared with the static or extern storage-class specifier
6033 cannot have a variable length array (VLA) type. However, an object declared with the static storage-
6034 class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all identifiers declared with a
6035 VM type have to be ordinary identifiers and cannot, therefore, be members of structures or unions.
6038 int A[n]; // invalid: file scope VLA
6039 extern int (*p2)[n]; // invalid: file scope VM
6040 int B[100]; // valid: file scope but not VM
6041 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
6042 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
6044 typedef int VLA[m][m]; // valid: block scope typedef VLA
6046 int (*y)[n]; // invalid: y not ordinary identifier
6047 int z[n]; // invalid: z not ordinary identifier
6049 int D[m]; // valid: auto VLA
6050 static int E[m]; // invalid: static block scope VLA
6051 extern int F[m]; // invalid: F has linkage and is VLA
6052 int (*s)[m]; // valid: auto pointer to VLA
6053 extern int (*r)[m]; // invalid: r has linkage and points to VLA
6054 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
6057 <p><b> Forward references</b>: function declarators (<a href="#6.7.5.3">6.7.5.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
6058 initialization (<a href="#6.7.8">6.7.8</a>).
6061 <p><small><a name="note123" href="#note123">123)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
6063 <p><small><a name="note124" href="#note124">124)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.5.3">6.7.5.3</a>).
6066 <h5><a name="6.7.5.3" href="#6.7.5.3">6.7.5.3 Function declarators (including prototypes)</a></h5>
6067 <h6>Constraints</h6>
6069 A function declarator shall not specify a return type that is a function type or an array
6072 The only storage-class specifier that shall occur in a parameter declaration is register.
6074 An identifier list in a function declarator that is not part of a definition of that function
6077 After adjustment, the parameters in a parameter type list in a function declarator that is
6078 part of a definition of that function shall not have incomplete type.
6081 If, in the declaration ''T D1'', D1 has the form
6083 D( parameter-type-list )</pre>
6087 D( identifier-list<sub>opt</sub> )</pre>
6088 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6089 T '', then the type specified for ident is ''derived-declarator-type-list function returning
6092 A parameter type list specifies the types of, and may declare identifiers for, the
6093 parameters of the function.
6095 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
6096 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
6097 array type derivation. If the keyword static also appears within the [ and ] of the
6098 array type derivation, then for each call to the function, the value of the corresponding
6099 actual argument shall provide access to the first element of an array with at least as many
6100 elements as specified by the size expression.
6102 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
6103 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
6105 If the list terminates with an ellipsis (, ...), no information about the number or types
6106 of the parameters after the comma is supplied.<sup><a href="#note125"><b>125)</b></a></sup>
6108 The special case of an unnamed parameter of type void as the only item in the list
6109 specifies that the function has no parameters.
6111 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
6112 parameter name, it shall be taken as a typedef name.
6114 If the function declarator is not part of a definition of that function, parameters may have
6115 incomplete type and may use the [*] notation in their sequences of declarator specifiers
6116 to specify variable length array types.
6118 The storage-class specifier in the declaration specifiers for a parameter declaration, if
6119 present, is ignored unless the declared parameter is one of the members of the parameter
6120 type list for a function definition.
6122 An identifier list declares only the identifiers of the parameters of the function. An empty
6123 list in a function declarator that is part of a definition of that function specifies that the
6124 function has no parameters. The empty list in a function declarator that is not part of a
6125 definition of that function specifies that no information about the number or types of the
6126 parameters is supplied.<sup><a href="#note126"><b>126)</b></a></sup>
6128 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note127"><b>127)</b></a></sup>
6132 Moreover, the parameter type lists, if both are present, shall agree in the number of
6133 parameters and in use of the ellipsis terminator; corresponding parameters shall have
6134 compatible types. If one type has a parameter type list and the other type is specified by a
6135 function declarator that is not part of a function definition and that contains an empty
6136 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
6137 parameter shall be compatible with the type that results from the application of the
6138 default argument promotions. If one type has a parameter type list and the other type is
6139 specified by a function definition that contains a (possibly empty) identifier list, both shall
6140 agree in the number of parameters, and the type of each prototype parameter shall be
6141 compatible with the type that results from the application of the default argument
6142 promotions to the type of the corresponding identifier. (In the determination of type
6143 compatibility and of a composite type, each parameter declared with function or array
6144 type is taken as having the adjusted type and each parameter declared with qualified type
6145 is taken as having the unqualified version of its declared type.)
6147 EXAMPLE 1 The declaration
6149 int f(void), *fip(), (*pfi)();</pre>
6150 declares a function f with no parameters returning an int, a function fip with no parameter specification
6151 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6152 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6153 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6154 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6155 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6156 designator, which is then used to call the function; it returns an int.
6158 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6159 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6160 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6161 the identifier of the pointer pfi has block scope and no linkage.
6164 EXAMPLE 2 The declaration
6166 int (*apfi[3])(int *x, int *y);</pre>
6167 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6168 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6169 go out of scope at the end of the declaration of apfi.
6172 EXAMPLE 3 The declaration
6174 int (*fpfi(int (*)(long), int))(int, ...);</pre>
6175 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6176 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6177 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6178 additional arguments of any type.
6181 EXAMPLE 4 The following prototype has a variably modified parameter.
6183 void addscalar(int n, int m,
6184 double a[n][n*m+300], double x);
6188 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
6191 void addscalar(int n, int m,
6192 double a[n][n*m+300], double x)
6194 for (int i = 0; i < n; i++)
6195 for (int j = 0, k = n*m+300; j < k; j++)
6196 // a is a pointer to a VLA with n*m+300 elements
6201 EXAMPLE 5 The following are all compatible function prototype declarators.
6203 double maximum(int n, int m, double a[n][m]);
6204 double maximum(int n, int m, double a[*][*]);
6205 double maximum(int n, int m, double a[ ][*]);
6206 double maximum(int n, int m, double a[ ][m]);</pre>
6209 void f(double (* restrict a)[5]);
6210 void f(double a[restrict][5]);
6211 void f(double a[restrict 3][5]);
6212 void f(double a[restrict static 3][5]);</pre>
6213 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6214 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6216 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
6220 <p><small><a name="note125" href="#note125">125)</a> The macros defined in the <a href="#7.15"><stdarg.h></a> header (<a href="#7.15">7.15</a>) may be used to access arguments that
6221 correspond to the ellipsis.
6223 <p><small><a name="note126" href="#note126">126)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6225 <p><small><a name="note127" href="#note127">127)</a> If both function types are ''old style'', parameter types are not compared.
6228 <h4><a name="6.7.6" href="#6.7.6">6.7.6 Type names</a></h4>
6233 specifier-qualifier-list abstract-declarator<sub>opt</sub>
6234 abstract-declarator:
6236 pointer<sub>opt</sub> direct-abstract-declarator
6237 direct-abstract-declarator:
6238 ( abstract-declarator )
6239 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list<sub>opt</sub>
6240 assignment-expression<sub>opt</sub> ]
6241 direct-abstract-declarator<sub>opt</sub> [ static type-qualifier-list<sub>opt</sub>
6242 assignment-expression ]
6243 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list static
6244 assignment-expression ]
6245 direct-abstract-declarator<sub>opt</sub> [ * ]
6246 direct-abstract-declarator<sub>opt</sub> ( parameter-type-list<sub>opt</sub> )</pre>
6249 In several contexts, it is necessary to specify a type. This is accomplished using a type
6250 name, which is syntactically a declaration for a function or an object of that type that
6251 omits the identifier.<sup><a href="#note128"><b>128)</b></a></sup>
6253 EXAMPLE The constructions
6262 (h) int (*const [])(unsigned int, ...)</pre>
6263 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6264 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6265 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6266 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6267 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6276 <p><small><a name="note128" href="#note128">128)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6277 parameter specification'', rather than redundant parentheses around the omitted identifier.
6280 <h4><a name="6.7.7" href="#6.7.7">6.7.7 Type definitions</a></h4>
6286 <h6>Constraints</h6>
6288 If a typedef name specifies a variably modified type then it shall have block scope.
6291 In a declaration whose storage-class specifier is typedef, each declarator defines an
6292 identifier to be a typedef name that denotes the type specified for the identifier in the way
6293 described in <a href="#6.7.5">6.7.5</a>. Any array size expressions associated with variable length array
6294 declarators are evaluated each time the declaration of the typedef name is reached in the
6295 order of execution. A typedef declaration does not introduce a new type, only a
6296 synonym for the type so specified. That is, in the following declarations:
6298 typedef T type_ident;
6300 type_ident is defined as a typedef name with the type specified by the declaration
6301 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6302 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6303 typedef name shares the same name space as other identifiers declared in ordinary
6308 typedef int MILES, KLICKSP();
6309 typedef struct { double hi, lo; } range;</pre>
6313 extern KLICKSP *metricp;
6316 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6317 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6318 such a structure. The object distance has a type compatible with any other int object.
6321 EXAMPLE 2 After the declarations
6323 typedef struct s1 { int x; } t1, *tp1;
6324 typedef struct s2 { int x; } t2, *tp2;</pre>
6325 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6326 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6329 EXAMPLE 3 The following obscure constructions
6331 typedef signed int t;
6338 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6339 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6340 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6341 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6342 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6343 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6344 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6345 in an inner scope by
6349 then a function f is declared with type ''function returning signed int with one unnamed parameter
6350 with type pointer to function returning signed int with one unnamed parameter with type signed
6351 int'', and an identifier t with type long int.
6354 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6355 following declarations of the signal function specify exactly the same type, the first without making use
6356 of any typedef names.
6358 typedef void fv(int), (*pfv)(int);
6359 void (*signal(int, void (*)(int)))(int);
6360 fv *signal(int, fv *);
6361 pfv signal(int, pfv);</pre>
6364 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6365 time the typedef name is defined, not each time it is used:
6370 typedef int B[n]; // B is n ints, n evaluated now
6372 B a; // a is n ints, n without += 1
6373 int b[n]; // a and b are different sizes
6374 for (int i = 1; i < n; i++)
6378 <h4><a name="6.7.8" href="#6.7.8">6.7.8 Initialization</a></h4>
6383 assignment-expression
6384 { initializer-list }
6385 { initializer-list , }
6387 designationopt initializer
6388 initializer-list , designation<sub>opt</sub> initializer
6393 designator-list designator
6395 [ constant-expression ]
6397 <h6>Constraints</h6>
6399 No initializer shall attempt to provide a value for an object not contained within the entity
6402 The type of the entity to be initialized shall be an array of unknown size or an object type
6403 that is not a variable length array type.
6405 All the expressions in an initializer for an object that has static storage duration shall be
6406 constant expressions or string literals.
6408 If the declaration of an identifier has block scope, and the identifier has external or
6409 internal linkage, the declaration shall have no initializer for the identifier.
6411 If a designator has the form
6413 [ constant-expression ]</pre>
6414 then the current object (defined below) shall have array type and the expression shall be
6415 an integer constant expression. If the array is of unknown size, any nonnegative value is
6418 If a designator has the form
6421 then the current object (defined below) shall have structure or union type and the
6422 identifier shall be the name of a member of that type.
6426 An initializer specifies the initial value stored in an object.
6428 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6429 members of objects of structure and union type do not participate in initialization.
6430 Unnamed members of structure objects have indeterminate value even after initialization.
6432 If an object that has automatic storage duration is not initialized explicitly, its value is
6433 indeterminate. If an object that has static storage duration is not initialized explicitly,
6436 <li> if it has pointer type, it is initialized to a null pointer;
6437 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6438 <li> if it is an aggregate, every member is initialized (recursively) according to these rules;
6439 <li> if it is a union, the first named member is initialized (recursively) according to these
6443 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6444 initial value of the object is that of the expression (after conversion); the same type
6445 constraints and conversions as for simple assignment apply, taking the type of the scalar
6446 to be the unqualified version of its declared type.
6448 The rest of this subclause deals with initializers for objects that have aggregate or union
6451 The initializer for a structure or union object that has automatic storage duration shall be
6452 either an initializer list as described below, or a single expression that has compatible
6453 structure or union type. In the latter case, the initial value of the object, including
6454 unnamed members, is that of the expression.
6456 An array of character type may be initialized by a character string literal, optionally
6457 enclosed in braces. Successive characters of the character string literal (including the
6458 terminating null character if there is room or if the array is of unknown size) initialize the
6459 elements of the array.
6461 An array with element type compatible with wchar_t may be initialized by a wide
6462 string literal, optionally enclosed in braces. Successive wide characters of the wide string
6463 literal (including the terminating null wide character if there is room or if the array is of
6464 unknown size) initialize the elements of the array.
6466 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6467 enclosed list of initializers for the elements or named members.
6469 Each brace-enclosed initializer list has an associated current object. When no
6470 designations are present, subobjects of the current object are initialized in order according
6471 to the type of the current object: array elements in increasing subscript order, structure
6473 members in declaration order, and the first named member of a union.<sup><a href="#note129"><b>129)</b></a></sup> In contrast, a
6474 designation causes the following initializer to begin initialization of the subobject
6475 described by the designator. Initialization then continues forward in order, beginning
6476 with the next subobject after that described by the designator.<sup><a href="#note130"><b>130)</b></a></sup>
6478 Each designator list begins its description with the current object associated with the
6479 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6480 particular member of its current object and changes the current object for the next
6481 designator (if any) to be that member.<sup><a href="#note131"><b>131)</b></a></sup> The current object that results at the end of the
6482 designator list is the subobject to be initialized by the following initializer.
6484 The initialization shall occur in initializer list order, each initializer provided for a
6485 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note132"><b>132)</b></a></sup>
6486 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6487 objects that have static storage duration.
6489 If the aggregate or union contains elements or members that are aggregates or unions,
6490 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6491 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6492 that brace and its matching right brace initialize the elements or members of the
6493 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6494 taken to account for the elements or members of the subaggregate or the first member of
6495 the contained union; any remaining initializers are left to initialize the next element or
6496 member of the aggregate of which the current subaggregate or contained union is a part.
6498 If there are fewer initializers in a brace-enclosed list than there are elements or members
6499 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6500 size than there are elements in the array, the remainder of the aggregate shall be
6501 initialized implicitly the same as objects that have static storage duration.
6503 If an array of unknown size is initialized, its size is determined by the largest indexed
6504 element with an explicit initializer. At the end of its initializer list, the array no longer
6505 has incomplete type.
6511 The order in which any side effects occur among the initialization list expressions is
6512 unspecified.<sup><a href="#note133"><b>133)</b></a></sup>
6514 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6516 int i = <a href="#3.5">3.5</a>;
6517 double complex c = 5 + 3 * I;</pre>
6518 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6521 EXAMPLE 2 The declaration
6523 int x[] = { 1, 3, 5 };</pre>
6524 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6525 and there are three initializers.
6528 EXAMPLE 3 The declaration
6535 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6536 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6537 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6541 1, 3, 5, 2, 4, 6, 3, 5, 7
6543 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6544 next three are taken successively for y[1] and y[2].
6547 EXAMPLE 4 The declaration
6550 { 1 }, { 2 }, { 3 }, { 4 }
6552 initializes the first column of z as specified and initializes the rest with zeros.
6555 EXAMPLE 5 The declaration
6557 struct { int a[3], b; } w[] = { { 1 }, 2 };</pre>
6558 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6559 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6566 EXAMPLE 6 The declaration
6568 short q[4][3][2] = {
6573 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6574 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
6575 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6576 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6577 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6578 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6579 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6580 diagnostic message would have been issued. The same initialization result could have been achieved by:
6582 short q[4][3][2] = {
6589 short q[4][3][2] = {
6601 in a fully bracketed form.
6603 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6607 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6610 typedef int A[]; // OK - declared with block scope</pre>
6613 A a = { 1, 2 }, b = { 3, 4, 5 };</pre>
6616 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };</pre>
6617 due to the rules for incomplete types.
6620 EXAMPLE 8 The declaration
6622 char s[] = "abc", t[3] = "abc";</pre>
6623 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6624 This declaration is identical to
6626 char s[] = { 'a', 'b', 'c', '\0' },
6627 t[] = { 'a', 'b', 'c' };</pre>
6628 The contents of the arrays are modifiable. On the other hand, the declaration
6630 char *p = "abc";</pre>
6631 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6632 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6633 modify the contents of the array, the behavior is undefined.
6636 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6639 enum { member_one, member_two };
6640 const char *nm[] = {
6641 [member_two] = "member two",
6642 [member_one] = "member one",
6646 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6648 div_t answer = { .quot = 2, .rem = -1 };</pre>
6651 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6652 might be misunderstood:
6654 struct { int a[3], b; } w[] =
6655 { [0].a = {1}, [1].a[0] = 2 };</pre>
6658 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6662 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6664 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6665 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6668 EXAMPLE 13 Any member of a union can be initialized:
6670 union { /* ... */ } u = { .any_member = 42 };</pre>
6672 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>).
6676 <p><small><a name="note129" href="#note129">129)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6677 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6678 current object: current objects are associated only with brace-enclosed initializer lists.
6680 <p><small><a name="note130" href="#note130">130)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
6681 the next subobject of an object containing the union.
6683 <p><small><a name="note131" href="#note131">131)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6684 the surrounding brace pair. Note, too, that each separate designator list is independent.
6686 <p><small><a name="note132" href="#note132">132)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6687 not be evaluated at all.
6689 <p><small><a name="note133" href="#note133">133)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
6692 <h3><a name="6.8" href="#6.8">6.8 Statements and blocks</a></h3>
6699 expression-statement
6702 jump-statement</pre>
6705 A statement specifies an action to be performed. Except as indicated, statements are
6706 executed in sequence.
6708 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6709 The initializers of objects that have automatic storage duration, and the variable length
6710 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6711 stored in the objects (including storing an indeterminate value in objects without an
6712 initializer) each time the declaration is reached in the order of execution, as if it were a
6713 statement, and within each declaration in the order that declarators appear.
6715 A full expression is an expression that is not part of another expression or of a declarator.
6716 Each of the following is a full expression: an initializer; the expression in an expression
6717 statement; the controlling expression of a selection statement (if or switch); the
6718 controlling expression of a while or do statement; each of the (optional) expressions of
6719 a for statement; the (optional) expression in a return statement. The end of a full
6720 expression is a sequence point.
6721 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6722 (<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>).
6724 <h4><a name="6.8.1" href="#6.8.1">6.8.1 Labeled statements</a></h4>
6729 identifier : statement
6730 case constant-expression : statement
6731 default : statement</pre>
6732 <h6>Constraints</h6>
6734 A case or default label shall appear only in a switch statement. Further
6735 constraints on such labels are discussed under the switch statement.
6738 Label names shall be unique within a function.
6741 Any statement may be preceded by a prefix that declares an identifier as a label name.
6742 Labels in themselves do not alter the flow of control, which continues unimpeded across
6744 <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>).
6746 <h4><a name="6.8.2" href="#6.8.2">6.8.2 Compound statement</a></h4>
6751 { block-item-list<sub>opt</sub> }
6754 block-item-list block-item
6760 A compound statement is a block.
6762 <h4><a name="6.8.3" href="#6.8.3">6.8.3 Expression and null statements</a></h4>
6766 expression-statement:
6767 expression<sub>opt</sub> ;</pre>
6770 The expression in an expression statement is evaluated as a void expression for its side
6771 effects.<sup><a href="#note134"><b>134)</b></a></sup>
6773 A null statement (consisting of just a semicolon) performs no operations.
6775 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6776 discarding of its value may be made explicit by converting the expression to a void expression by means of
6787 EXAMPLE 2 In the program fragment
6791 while (*s++ != '\0')
6793 a null statement is used to supply an empty loop body to the iteration statement.
6796 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6811 <p><b> Forward references</b>: iteration statements (<a href="#6.8.5">6.8.5</a>).
6814 <p><small><a name="note134" href="#note134">134)</a> Such as assignments, and function calls which have side effects.
6817 <h4><a name="6.8.4" href="#6.8.4">6.8.4 Selection statements</a></h4>
6821 selection-statement:
6822 if ( expression ) statement
6823 if ( expression ) statement else statement
6824 switch ( expression ) statement</pre>
6827 A selection statement selects among a set of statements depending on the value of a
6828 controlling expression.
6830 A selection statement is a block whose scope is a strict subset of the scope of its
6831 enclosing block. Each associated substatement is also a block whose scope is a strict
6832 subset of the scope of the selection statement.
6834 <h5><a name="6.8.4.1" href="#6.8.4.1">6.8.4.1 The if statement</a></h5>
6835 <h6>Constraints</h6>
6837 The controlling expression of an if statement shall have scalar type.
6840 In both forms, the first substatement is executed if the expression compares unequal to 0.
6841 In the else form, the second substatement is executed if the expression compares equal
6843 to 0. If the first substatement is reached via a label, the second substatement is not
6846 An else is associated with the lexically nearest preceding if that is allowed by the
6849 <h5><a name="6.8.4.2" href="#6.8.4.2">6.8.4.2 The switch statement</a></h5>
6850 <h6>Constraints</h6>
6852 The controlling expression of a switch statement shall have integer type.
6854 If a switch statement has an associated case or default label within the scope of an
6855 identifier with a variably modified type, the entire switch statement shall be within the
6856 scope of that identifier.<sup><a href="#note135"><b>135)</b></a></sup>
6858 The expression of each case label shall be an integer constant expression and no two of
6859 the case constant expressions in the same switch statement shall have the same value
6860 after conversion. There may be at most one default label in a switch statement.
6861 (Any enclosed switch statement may have a default label or case constant
6862 expressions with values that duplicate case constant expressions in the enclosing
6866 A switch statement causes control to jump to, into, or past the statement that is the
6867 switch body, depending on the value of a controlling expression, and on the presence of a
6868 default label and the values of any case labels on or in the switch body. A case or
6869 default label is accessible only within the closest enclosing switch statement.
6871 The integer promotions are performed on the controlling expression. The constant
6872 expression in each case label is converted to the promoted type of the controlling
6873 expression. If a converted value matches that of the promoted controlling expression,
6874 control jumps to the statement following the matched case label. Otherwise, if there is
6875 a default label, control jumps to the labeled statement. If no converted case constant
6876 expression matches and there is no default label, no part of the switch body is
6878 <h6> Implementation limits</h6>
6880 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
6888 EXAMPLE In the artificial program fragment
6896 /* falls through into default code */
6900 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6901 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6902 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6906 <p><small><a name="note135" href="#note135">135)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
6907 default label associated with the switch that is in the block containing the declaration.
6910 <h4><a name="6.8.5" href="#6.8.5">6.8.5 Iteration statements</a></h4>
6914 iteration-statement:
6915 while ( expression ) statement
6916 do statement while ( expression ) ;
6917 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
6918 for ( declaration expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement</pre>
6919 <h6>Constraints</h6>
6921 The controlling expression of an iteration statement shall have scalar type.
6923 The declaration part of a for statement shall only declare identifiers for objects having
6924 storage class auto or register.
6927 An iteration statement causes a statement called the loop body to be executed repeatedly
6928 until the controlling expression compares equal to 0. The repetition occurs regardless of
6929 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note136"><b>136)</b></a></sup>
6931 An iteration statement is a block whose scope is a strict subset of the scope of its
6932 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6933 of the iteration statement.
6941 <p><small><a name="note136" href="#note136">136)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
6942 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6945 <h5><a name="6.8.5.1" href="#6.8.5.1">6.8.5.1 The while statement</a></h5>
6947 The evaluation of the controlling expression takes place before each execution of the loop
6950 <h5><a name="6.8.5.2" href="#6.8.5.2">6.8.5.2 The do statement</a></h5>
6952 The evaluation of the controlling expression takes place after each execution of the loop
6955 <h5><a name="6.8.5.3" href="#6.8.5.3">6.8.5.3 The for statement</a></h5>
6959 for ( clause-1 ; expression-2 ; expression-3 ) statement</pre>
6960 behaves as follows: The expression expression-2 is the controlling expression that is
6961 evaluated before each execution of the loop body. The expression expression-3 is
6962 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6963 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6964 the entire loop, including the other two expressions; it is reached in the order of execution
6965 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6966 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note137"><b>137)</b></a></sup>
6968 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6972 <p><small><a name="note137" href="#note137">137)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
6973 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6974 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6975 specifies an operation (such as incrementing) that is performed after each iteration.
6978 <h4><a name="6.8.6" href="#6.8.6">6.8.6 Jump statements</a></h4>
6986 return expression<sub>opt</sub> ;</pre>
6989 A jump statement causes an unconditional jump to another place.
6996 <h5><a name="6.8.6.1" href="#6.8.6.1">6.8.6.1 The goto statement</a></h5>
6997 <h6>Constraints</h6>
6999 The identifier in a goto statement shall name a label located somewhere in the enclosing
7000 function. A goto statement shall not jump from outside the scope of an identifier having
7001 a variably modified type to inside the scope of that identifier.
7004 A goto statement causes an unconditional jump to the statement prefixed by the named
7005 label in the enclosing function.
7007 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
7008 following outline presents one possible approach to a problem based on these three assumptions:
7010 <li> The general initialization code accesses objects only visible to the current function.
7011 <li> The general initialization code is too large to warrant duplication.
7012 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
7013 continue statements, for example.)
7018 // determine next operation
7020 if (need to reinitialize) {
7021 // reinitialize-only code
7024 // general initialization code
7028 // handle other operations
7034 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
7035 modified types. A jump within the scope, however, is permitted.
7037 goto lab3; // invalid: going INTO scope of VLA.
7040 a[j] = <a href="#4.4">4.4</a>;
7042 a[j] = <a href="#3.3">3.3</a>;
7043 goto lab4; // valid: going WITHIN scope of VLA.
7044 a[j] = <a href="#5.5">5.5</a>;
7046 a[j] = <a href="#6.6">6.6</a>;
7048 goto lab4; // invalid: going INTO scope of VLA.</pre>
7051 <h5><a name="6.8.6.2" href="#6.8.6.2">6.8.6.2 The continue statement</a></h5>
7052 <h6>Constraints</h6>
7054 A continue statement shall appear only in or as a loop body.
7057 A continue statement causes a jump to the loop-continuation portion of the smallest
7058 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
7061 while (/* ... */) { do { for (/* ... */) {
7062 /* ... */ /* ... */ /* ... */
7063 continue; continue; continue;
7064 /* ... */ /* ... */ /* ... */
7065 contin: ; contin: ; contin: ;
7066 } } while (/* ... */); }</pre>
7067 unless the continue statement shown is in an enclosed iteration statement (in which
7068 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note138"><b>138)</b></a></sup>
7071 <p><small><a name="note138" href="#note138">138)</a> Following the contin: label is a null statement.
7074 <h5><a name="6.8.6.3" href="#6.8.6.3">6.8.6.3 The break statement</a></h5>
7075 <h6>Constraints</h6>
7077 A break statement shall appear only in or as a switch body or loop body.
7080 A break statement terminates execution of the smallest enclosing switch or iteration
7087 <h5><a name="6.8.6.4" href="#6.8.6.4">6.8.6.4 The return statement</a></h5>
7088 <h6>Constraints</h6>
7090 A return statement with an expression shall not appear in a function whose return type
7091 is void. A return statement without an expression shall only appear in a function
7092 whose return type is void.
7095 A return statement terminates execution of the current function and returns control to
7096 its caller. A function may have any number of return statements.
7098 If a return statement with an expression is executed, the value of the expression is
7099 returned to the caller as the value of the function call expression. If the expression has a
7100 type different from the return type of the function in which it appears, the value is
7101 converted as if by assignment to an object having the return type of the function.<sup><a href="#note139"><b>139)</b></a></sup>
7105 struct s { double i; } f(void);
7121 g.u2.f3 = f();</pre>
7122 there is no undefined behavior, although there would be if the assignment were done directly (without using
7123 a function call to fetch the value).
7131 <p><small><a name="note139" href="#note139">139)</a> The return statement is not an assignment. The overlap restriction of subclause <a href="#6.5.16.1">6.5.16.1</a> does not
7132 apply to the case of function return. The representation of floating-point values may have wider range
7133 or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
7134 range and precision.
7137 <h3><a name="6.9" href="#6.9">6.9 External definitions</a></h3>
7142 external-declaration
7143 translation-unit external-declaration
7144 external-declaration:
7147 <h6>Constraints</h6>
7149 The storage-class specifiers auto and register shall not appear in the declaration
7150 specifiers in an external declaration.
7152 There shall be no more than one external definition for each identifier declared with
7153 internal linkage in a translation unit. Moreover, if an identifier declared with internal
7154 linkage is used in an expression (other than as a part of the operand of a sizeof
7155 operator whose result is an integer constant), there shall be exactly one external definition
7156 for the identifier in the translation unit.
7159 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,
7160 which consists of a sequence of external declarations. These are described as ''external''
7161 because they appear outside any function (and hence have file scope). As discussed in
7162 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
7163 by the identifier is a definition.
7165 An external definition is an external declaration that is also a definition of a function
7166 (other than an inline definition) or an object. If an identifier declared with external
7167 linkage is used in an expression (other than as part of the operand of a sizeof operator
7168 whose result is an integer constant), somewhere in the entire program there shall be
7169 exactly one external definition for the identifier; otherwise, there shall be no more than
7170 one.<sup><a href="#note140"><b>140)</b></a></sup>
7178 <p><small><a name="note140" href="#note140">140)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
7179 external definition for it.
7182 <h4><a name="6.9.1" href="#6.9.1">6.9.1 Function definitions</a></h4>
7186 function-definition:
7187 declaration-specifiers declarator declaration-list<sub>opt</sub> compound-statement
7190 declaration-list declaration</pre>
7191 <h6>Constraints</h6>
7193 The identifier declared in a function definition (which is the name of the function) shall
7194 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note141"><b>141)</b></a></sup>
7196 The return type of a function shall be void or an object type other than array type.
7198 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
7201 If the declarator includes a parameter type list, the declaration of each parameter shall
7202 include an identifier, except for the special case of a parameter list consisting of a single
7203 parameter of type void, in which case there shall not be an identifier. No declaration list
7206 If the declarator includes an identifier list, each declaration in the declaration list shall
7207 have at least one declarator, those declarators shall declare only identifiers from the
7208 identifier list, and every identifier in the identifier list shall be declared. An identifier
7209 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
7210 declaration list shall contain no storage-class specifier other than register and no
7219 The declarator in a function definition specifies the name of the function being defined
7220 and the identifiers of its parameters. If the declarator includes a parameter type list, the
7221 list also specifies the types of all the parameters; such a declarator also serves as a
7222 function prototype for later calls to the same function in the same translation unit. If the
7223 declarator includes an identifier list,<sup><a href="#note142"><b>142)</b></a></sup> the types of the parameters shall be declared in a
7224 following declaration list. In either case, the type of each parameter is adjusted as
7225 described in <a href="#6.7.5.3">6.7.5.3</a> for a parameter type list; the resulting type shall be an object type.
7227 If a function that accepts a variable number of arguments is defined without a parameter
7228 type list that ends with the ellipsis notation, the behavior is undefined.
7230 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
7231 effect declared at the head of the compound statement that constitutes the function body
7232 (and therefore cannot be redeclared in the function body except in an enclosed block).
7233 The layout of the storage for parameters is unspecified.
7235 On entry to the function, the size expressions of each variably modified parameter are
7236 evaluated and the value of each argument expression is converted to the type of the
7237 corresponding parameter as if by assignment. (Array expressions and function
7238 designators as arguments were converted to pointers before the call.)
7240 After all parameters have been assigned, the compound statement that constitutes the
7241 body of the function definition is executed.
7243 If the } that terminates a function is reached, and the value of the function call is used by
7244 the caller, the behavior is undefined.
7246 EXAMPLE 1 In the following:
7248 extern int max(int a, int b)
7250 return a > b ? a : b;
7252 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
7253 function declarator; and
7255 { return a > b ? a : b; }</pre>
7256 is the function body. The following similar definition uses the identifier-list form for the parameter
7264 extern int max(a, b)
7267 return a > b ? a : b;
7269 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
7270 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
7271 to the function, whereas the second form does not.
7274 EXAMPLE 2 To pass one function to another, one might say
7279 Then the definition of g might read
7281 void g(int (*funcp)(void))
7284 (*funcp)(); /* or funcp(); ... */
7288 void g(int func(void))
7291 func(); /* or (*func)(); ... */
7296 <p><small><a name="note141" href="#note141">141)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
7299 typedef int F(void); // type F is ''function with no parameters
7301 F f, g; // f and g both have type compatible with F
7302 F f { /* ... */ } // WRONG: syntax/constraint error
7303 F g() { /* ... */ } // WRONG: declares that g returns a function
7304 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
7305 int g() { /* ... */ } // RIGHT: g has type compatible with F
7306 F *e(void) { /* ... */ } // e returns a pointer to a function
7307 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
7308 int (*fp)(void); // fp points to a function that has type F
7309 F *Fp; // Fp points to a function that has type F</pre>
7311 <p><small><a name="note142" href="#note142">142)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
7314 <h4><a name="6.9.2" href="#6.9.2">6.9.2 External object definitions</a></h4>
7317 If the declaration of an identifier for an object has file scope and an initializer, the
7318 declaration is an external definition for the identifier.
7320 A declaration of an identifier for an object that has file scope without an initializer, and
7321 without a storage-class specifier or with the storage-class specifier static, constitutes a
7322 tentative definition. If a translation unit contains one or more tentative definitions for an
7323 identifier, and the translation unit contains no external definition for that identifier, then
7324 the behavior is exactly as if the translation unit contains a file scope declaration of that
7325 identifier, with the composite type as of the end of the translation unit, with an initializer
7328 If the declaration of an identifier for an object is a tentative definition and has internal
7329 linkage, the declared type shall not be an incomplete type.
7334 int i1 = 1; // definition, external linkage
7335 static int i2 = 2; // definition, internal linkage
7336 extern int i3 = 3; // definition, external linkage
7337 int i4; // tentative definition, external linkage
7338 static int i5; // tentative definition, internal linkage
7339 int i1; // valid tentative definition, refers to previous
7340 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7341 int i3; // valid tentative definition, refers to previous
7342 int i4; // valid tentative definition, refers to previous
7343 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7344 extern int i1; // refers to previous, whose linkage is external
7345 extern int i2; // refers to previous, whose linkage is internal
7346 extern int i3; // refers to previous, whose linkage is external
7347 extern int i4; // refers to previous, whose linkage is external
7348 extern int i5; // refers to previous, whose linkage is internal</pre>
7351 EXAMPLE 2 If at the end of the translation unit containing
7354 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7355 zero on program startup.
7358 <h3><a name="6.10" href="#6.10">6.10 Preprocessing directives</a></h3>
7374 if-group elif-groups<sub>opt</sub> else-group<sub>opt</sub> endif-line
7376 # if constant-expression new-line group<sub>opt</sub>
7377 # ifdef identifier new-line group<sub>opt</sub>
7378 # ifndef identifier new-line group<sub>opt</sub>
7381 elif-groups elif-group
7383 # elif constant-expression new-line group<sub>opt</sub>
7385 # else new-line group<sub>opt</sub>
7389 # include pp-tokens new-line
7390 # define identifier replacement-list new-line
7391 # define identifier lparen identifier-list<sub>opt</sub> )
7392 replacement-list new-line
7393 # define identifier lparen ... ) replacement-list new-line
7394 # define identifier lparen identifier-list , ... )
7395 replacement-list new-line
7396 # undef identifier new-line
7397 # line pp-tokens new-line
7398 # error pp-tokens<sub>opt</sub> new-line
7399 # pragma pp-tokens<sub>opt</sub> new-line
7402 pp-tokens<sub>opt</sub> new-line
7406 a ( character not immediately preceded by white-space
7408 pp-tokens<sub>opt</sub>
7411 pp-tokens preprocessing-token
7413 the new-line character</pre>
7414 <h6>Description</h6>
7416 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7417 following constraints: The first token in the sequence is a # preprocessing token that (at
7418 the start of translation phase 4) is either the first character in the source file (optionally
7419 after white space containing no new-line characters) or that follows white space
7420 containing at least one new-line character. The last token in the sequence is the first new-
7421 line character that follows the first token in the sequence.<sup><a href="#note143"><b>143)</b></a></sup> A new-line character ends
7422 the preprocessing directive even if it occurs within what would otherwise be an
7425 invocation of a function-like macro.
7427 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7428 with any of the directive names appearing in the syntax.
7430 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
7431 sequence of preprocessing tokens to occur between the directive name and the following
7433 <h6>Constraints</h6>
7435 The only white-space characters that shall appear between preprocessing tokens within a
7436 preprocessing directive (from just after the introducing # preprocessing token through
7437 just before the terminating new-line character) are space and horizontal-tab (including
7438 spaces that have replaced comments or possibly other white-space characters in
7439 translation phase 3).
7442 The implementation can process and skip sections of source files conditionally, include
7443 other source files, and replace macros. These capabilities are called preprocessing,
7444 because conceptually they occur before translation of the resulting translation unit.
7446 The preprocessing tokens within a preprocessing directive are not subject to macro
7447 expansion unless otherwise stated.
7452 EMPTY # include <file.h></pre>
7453 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7454 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7459 <p><small><a name="note143" href="#note143">143)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7460 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7461 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7464 <h4><a name="6.10.1" href="#6.10.1">6.10.1 Conditional inclusion</a></h4>
7465 <h6>Constraints</h6>
7467 The expression that controls conditional inclusion shall be an integer constant expression
7468 except that: it shall not contain a cast; identifiers (including those lexically identical to
7469 keywords) are interpreted as described below;<sup><a href="#note144"><b>144)</b></a></sup> and it may contain unary operator
7470 expressions of the form
7477 defined identifier</pre>
7480 defined ( identifier )</pre>
7481 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7482 predefined or if it has been the subject of a #define preprocessing directive without an
7483 intervening #undef directive with the same subject identifier), 0 if it is not.
7485 Each preprocessing token that remains (in the list of preprocessing tokens that will
7486 become the controlling expression) after all macro replacements have occurred shall be in
7487 the lexical form of a token (<a href="#6.4">6.4</a>).
7490 Preprocessing directives of the forms
7492 # if constant-expression new-line group<sub>opt</sub>
7493 # elif constant-expression new-line group<sub>opt</sub></pre>
7494 check whether the controlling constant expression evaluates to nonzero.
7496 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7497 the controlling constant expression are replaced (except for those macro names modified
7498 by the defined unary operator), just as in normal text. If the token defined is
7499 generated as a result of this replacement process or use of the defined unary operator
7500 does not match one of the two specified forms prior to macro replacement, the behavior is
7501 undefined. After all replacements due to macro expansion and the defined unary
7502 operator have been performed, all remaining identifiers (including those lexically
7503 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7504 token is converted into a token. The resulting tokens compose the controlling constant
7505 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7506 token conversion and evaluation, all signed integer types and all unsigned integer types
7507 act as if they have the same representation as, respectively, the types intmax_t and
7508 uintmax_t defined in the header <a href="#7.18"><stdint.h></a>.<sup><a href="#note145"><b>145)</b></a></sup> This includes interpreting
7509 character constants, which may involve converting escape sequences into execution
7510 character set members. Whether the numeric value for these character constants matches
7511 the value obtained when an identical character constant occurs in an expression (other
7512 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note146"><b>146)</b></a></sup> Also, whether a
7513 single-character character constant may have a negative value is implementation-defined.
7515 Preprocessing directives of the forms
7521 # ifdef identifier new-line group<sub>opt</sub>
7522 # ifndef identifier new-line group<sub>opt</sub></pre>
7523 check whether the identifier is or is not currently defined as a macro name. Their
7524 conditions are equivalent to #if defined identifier and #if !defined identifier
7527 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7528 that it controls is skipped: directives are processed only through the name that determines
7529 the directive in order to keep track of the level of nested conditionals; the rest of the
7530 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7531 group. Only the first group whose control condition evaluates to true (nonzero) is
7532 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7533 group controlled by the #else is processed; lacking a #else directive, all the groups
7534 until the #endif are skipped.<sup><a href="#note147"><b>147)</b></a></sup>
7535 <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
7536 integer types (<a href="#7.18.1.5">7.18.1.5</a>).
7539 <p><small><a name="note144" href="#note144">144)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7540 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7542 <p><small><a name="note145" href="#note145">145)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7543 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7544 translation phase 7.
7546 <p><small><a name="note146" href="#note146">146)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7547 evaluate to the same value in these two contexts.
7550 if ('z' - 'a' == 25)</pre>
7553 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7554 before the terminating new-line character. However, comments may appear anywhere in a source file,
7555 including within a preprocessing directive.
7558 <h4><a name="6.10.2" href="#6.10.2">6.10.2 Source file inclusion</a></h4>
7559 <h6>Constraints</h6>
7561 A #include directive shall identify a header or source file that can be processed by the
7565 A preprocessing directive of the form
7567 # include <h-char-sequence> new-line</pre>
7568 searches a sequence of implementation-defined places for a header identified uniquely by
7569 the specified sequence between the < and > delimiters, and causes the replacement of that
7570 directive by the entire contents of the header. How the places are specified or the header
7571 identified is implementation-defined.
7573 A preprocessing directive of the form
7579 # include "q-char-sequence" new-line</pre>
7580 causes the replacement of that directive by the entire contents of the source file identified
7581 by the specified sequence between the " delimiters. The named source file is searched
7582 for in an implementation-defined manner. If this search is not supported, or if the search
7583 fails, the directive is reprocessed as if it read
7585 # include <h-char-sequence> new-line</pre>
7586 with the identical contained sequence (including > characters, if any) from the original
7589 A preprocessing directive of the form
7591 # include pp-tokens new-line</pre>
7592 (that does not match one of the two previous forms) is permitted. The preprocessing
7593 tokens after include in the directive are processed just as in normal text. (Each
7594 identifier currently defined as a macro name is replaced by its replacement list of
7595 preprocessing tokens.) The directive resulting after all replacements shall match one of
7596 the two previous forms.<sup><a href="#note148"><b>148)</b></a></sup> The method by which a sequence of preprocessing tokens
7597 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7598 single header name preprocessing token is implementation-defined.
7600 The implementation shall provide unique mappings for sequences consisting of one or
7601 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7602 first character shall not be a digit. The implementation may ignore distinctions of
7603 alphabetical case and restrict the mapping to eight significant characters before the
7606 A #include preprocessing directive may appear in a source file that has been read
7607 because of a #include directive in another file, up to an implementation-defined
7608 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
7610 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7612 #include <a href="#7.19"><stdio.h></a>
7613 #include "myprog.h"</pre>
7616 EXAMPLE 2 This illustrates macro-replaced #include directives:
7624 #define INCFILE "vers1.h"
7626 #define INCFILE "vers2.h" // and so on
7628 #define INCFILE "versN.h"
7630 #include INCFILE</pre>
7632 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>).
7635 <p><small><a name="note148" href="#note148">148)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
7636 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.
7639 <h4><a name="6.10.3" href="#6.10.3">6.10.3 Macro replacement</a></h4>
7640 <h6>Constraints</h6>
7642 Two replacement lists are identical if and only if the preprocessing tokens in both have
7643 the same number, ordering, spelling, and white-space separation, where all white-space
7644 separations are considered identical.
7646 An identifier currently defined as an object-like macro shall not be redefined by another
7647 #define preprocessing directive unless the second definition is an object-like macro
7648 definition and the two replacement lists are identical. Likewise, an identifier currently
7649 defined as a function-like macro shall not be redefined by another #define
7650 preprocessing directive unless the second definition is a function-like macro definition
7651 that has the same number and spelling of parameters, and the two replacement lists are
7654 There shall be white-space between the identifier and the replacement list in the definition
7655 of an object-like macro.
7657 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7658 arguments (including those arguments consisting of no preprocessing tokens) in an
7659 invocation of a function-like macro shall equal the number of parameters in the macro
7660 definition. Otherwise, there shall be more arguments in the invocation than there are
7661 parameters in the macro definition (excluding the ...). There shall exist a )
7662 preprocessing token that terminates the invocation.
7664 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7665 macro that uses the ellipsis notation in the parameters.
7667 A parameter identifier in a function-like macro shall be uniquely declared within its
7671 The identifier immediately following the define is called the macro name. There is one
7672 name space for macro names. Any white-space characters preceding or following the
7673 replacement list of preprocessing tokens are not considered part of the replacement list
7674 for either form of macro.
7677 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7678 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7680 A preprocessing directive of the form
7682 # define identifier replacement-list new-line</pre>
7683 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note149"><b>149)</b></a></sup>
7684 to be replaced by the replacement list of preprocessing tokens that constitute the
7685 remainder of the directive. The replacement list is then rescanned for more macro names
7688 A preprocessing directive of the form
7690 # define identifier lparen identifier-list<sub>opt</sub> ) replacement-list new-line
7691 # define identifier lparen ... ) replacement-list new-line
7692 # define identifier lparen identifier-list , ... ) replacement-list new-line</pre>
7693 defines a function-like macro with parameters, whose use is similar syntactically to a
7694 function call. The parameters are specified by the optional list of identifiers, whose scope
7695 extends from their declaration in the identifier list until the new-line character that
7696 terminates the #define preprocessing directive. Each subsequent instance of the
7697 function-like macro name followed by a ( as the next preprocessing token introduces the
7698 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7699 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7700 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7701 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7702 tokens making up an invocation of a function-like macro, new-line is considered a normal
7703 white-space character.
7705 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7706 forms the list of arguments for the function-like macro. The individual arguments within
7707 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7708 between matching inner parentheses do not separate arguments. If there are sequences of
7709 preprocessing tokens within the list of arguments that would otherwise act as
7710 preprocessing directives,<sup><a href="#note150"><b>150)</b></a></sup> the behavior is undefined.
7712 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7713 including any separating comma preprocessing tokens, are merged to form a single item:
7714 the variable arguments. The number of arguments so combined is such that, following
7718 merger, the number of arguments is one more than the number of parameters in the macro
7719 definition (excluding the ...).
7722 <p><small><a name="note149" href="#note149">149)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7723 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7724 are never scanned for macro names or parameters.
7726 <p><small><a name="note150" href="#note150">150)</a> Despite the name, a non-directive is a preprocessing directive.
7729 <h5><a name="6.10.3.1" href="#6.10.3.1">6.10.3.1 Argument substitution</a></h5>
7731 After the arguments for the invocation of a function-like macro have been identified,
7732 argument substitution takes place. A parameter in the replacement list, unless preceded
7733 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7734 replaced by the corresponding argument after all macros contained therein have been
7735 expanded. Before being substituted, each argument's preprocessing tokens are
7736 completely macro replaced as if they formed the rest of the preprocessing file; no other
7737 preprocessing tokens are available.
7739 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7740 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7743 <h5><a name="6.10.3.2" href="#6.10.3.2">6.10.3.2 The # operator</a></h5>
7744 <h6>Constraints</h6>
7746 Each # preprocessing token in the replacement list for a function-like macro shall be
7747 followed by a parameter as the next preprocessing token in the replacement list.
7750 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7751 token, both are replaced by a single character string literal preprocessing token that
7752 contains the spelling of the preprocessing token sequence for the corresponding
7753 argument. Each occurrence of white space between the argument's preprocessing tokens
7754 becomes a single space character in the character string literal. White space before the
7755 first preprocessing token and after the last preprocessing token composing the argument
7756 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7757 is retained in the character string literal, except for special handling for producing the
7758 spelling of string literals and character constants: a \ character is inserted before each "
7759 and \ character of a character constant or string literal (including the delimiting "
7760 characters), except that it is implementation-defined whether a \ character is inserted
7761 before the \ character beginning a universal character name. If the replacement that
7762 results is not a valid character string literal, the behavior is undefined. The character
7763 string literal corresponding to an empty argument is "". The order of evaluation of # and
7764 ## operators is unspecified.
7767 <h5><a name="6.10.3.3" href="#6.10.3.3">6.10.3.3 The ## operator</a></h5>
7768 <h6>Constraints</h6>
7770 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7771 list for either form of macro definition.
7774 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7775 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7776 argument's preprocessing token sequence; however, if an argument consists of no
7777 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7778 instead.<sup><a href="#note151"><b>151)</b></a></sup>
7780 For both object-like and function-like macro invocations, before the replacement list is
7781 reexamined for more macro names to replace, each instance of a ## preprocessing token
7782 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7783 token is concatenated with the following preprocessing token. Placemarker
7784 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7785 a single placemarker preprocessing token, and concatenation of a placemarker with a
7786 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7787 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7788 token is available for further macro replacement. The order of evaluation of ## operators
7791 EXAMPLE In the following fragment:
7793 #define hash_hash # ## #
7794 #define mkstr(a) # a
7795 #define in_between(a) mkstr(a)
7796 #define join(c, d) in_between(c hash_hash d)
7797 char p[] = join(x, y); // equivalent to
7798 // char p[] = "x ## y";</pre>
7799 The expansion produces, at various stages:
7802 in_between(x hash_hash y)
7806 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7807 this new token is not the ## operator.
7813 <p><small><a name="note151" href="#note151">151)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7814 exist only within translation phase 4.
7817 <h5><a name="6.10.3.4" href="#6.10.3.4">6.10.3.4 Rescanning and further replacement</a></h5>
7819 After all parameters in the replacement list have been substituted and # and ##
7820 processing has taken place, all placemarker preprocessing tokens are removed. Then, the
7821 resulting preprocessing token sequence is rescanned, along with all subsequent
7822 preprocessing tokens of the source file, for more macro names to replace.
7824 If the name of the macro being replaced is found during this scan of the replacement list
7825 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7826 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7827 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7828 available for further replacement even if they are later (re)examined in contexts in which
7829 that macro name preprocessing token would otherwise have been replaced.
7831 The resulting completely macro-replaced preprocessing token sequence is not processed
7832 as a preprocessing directive even if it resembles one, but all pragma unary operator
7833 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
7835 <h5><a name="6.10.3.5" href="#6.10.3.5">6.10.3.5 Scope of macro definitions</a></h5>
7837 A macro definition lasts (independent of block structure) until a corresponding #undef
7838 directive is encountered or (if none is encountered) until the end of the preprocessing
7839 translation unit. Macro definitions have no significance after translation phase 4.
7841 A preprocessing directive of the form
7843 # undef identifier new-line</pre>
7844 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7845 the specified identifier is not currently defined as a macro name.
7847 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7850 int table[TABSIZE];</pre>
7853 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7854 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7855 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7856 arguments a second time (including side effects) and generating more code than a function if invoked
7857 several times. It also cannot have its address taken, as it has none.
7859 #define max(a, b) ((a) > (b) ? (a) : (b))</pre>
7860 The parentheses ensure that the arguments and the resulting expression are bound properly.
7863 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7866 #define f(a) f(x * (a))
7877 #define r(x,y) x ## y
7879 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7880 g(x+(3,4)-w) | h 5) & m
7882 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7883 char c[2][6] = { str(hello), str() };</pre>
7886 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7887 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7888 int i[] = { 1, 23, 4, 5, };
7889 char c[2][6] = { "hello", "" };</pre>
7892 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7896 #define xstr(s) str(s)
7897 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
7899 #define INCFILE(n) vers ## n
7900 #define glue(a, b) a ## b
7901 #define xglue(a, b) glue(a, b)
7902 #define HIGHLOW "hello"
7903 #define LOW LOW ", world"
7905 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
7906 == 0) str(: @\n), s);
7907 #include xstr(INCFILE(2).h)
7909 xglue(HIGH, LOW)</pre>
7913 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
7915 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
7917 #include "vers2.h" (after macro replacement, before file access)
7919 "hello" ", world"</pre>
7920 or, after concatenation of the character string literals,
7922 printf("x1= %d, x2= %s", x1, x2);
7924 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
7926 #include "vers2.h" (after macro replacement, before file access)
7928 "hello, world"</pre>
7929 Space around the # and ## tokens in the macro definition is optional.
7932 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7934 #define t(x,y,z) x ## y ## z
7935 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7936 t(10,,), t(,11,), t(,,12), t(,,) };</pre>
7939 int j[] = { 123, 45, 67, 89,
7940 10, 11, 12, };</pre>
7943 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7945 #define OBJ_LIKE (1-1)
7946 #define OBJ_LIKE /* white space */ (1-1) /* other */
7947 #define FUNC_LIKE(a) ( a )
7948 #define FUNC_LIKE( a )( /* note the white space */ \
7949 a /* other stuff on this line
7951 But the following redefinitions are invalid:
7953 #define OBJ_LIKE (0) // different token sequence
7954 #define OBJ_LIKE (1 - 1) // different white space
7955 #define FUNC_LIKE(b) ( a ) // different parameter usage
7956 #define FUNC_LIKE(b) ( b ) // different parameter spelling</pre>
7959 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7962 #define debug(...) fprintf(stderr, __VA_ARGS__)
7963 #define showlist(...) puts(#__VA_ARGS__)
7964 #define report(test, ...) ((test)?puts(#test):\
7965 printf(__VA_ARGS__))
7967 debug("X = %d\n", x);
7968 showlist(The first, second, and third items.);
7969 report(x>y, "x is %d but y is %d", x, y);</pre>
7972 fprintf(stderr, "Flag" );
7973 fprintf(stderr, "X = %d\n", x );
7974 puts( "The first, second, and third items." );
7975 ((x>y)?puts("x>y"):
7976 printf("x is %d but y is %d", x, y));</pre>
7979 <h4><a name="6.10.4" href="#6.10.4">6.10.4 Line control</a></h4>
7980 <h6>Constraints</h6>
7982 The string literal of a #line directive, if present, shall be a character string literal.
7985 The line number of the current source line is one greater than the number of new-line
7986 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7987 file to the current token.
7989 A preprocessing directive of the form
7991 # line digit-sequence new-line</pre>
7992 causes the implementation to behave as if the following sequence of source lines begins
7993 with a source line that has a line number as specified by the digit sequence (interpreted as
7994 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7997 A preprocessing directive of the form
7999 # line digit-sequence "s-char-sequence<sub>opt</sub>" new-line</pre>
8000 sets the presumed line number similarly and changes the presumed name of the source
8001 file to be the contents of the character string literal.
8003 A preprocessing directive of the form
8005 # line pp-tokens new-line</pre>
8006 (that does not match one of the two previous forms) is permitted. The preprocessing
8007 tokens after line on the directive are processed just as in normal text (each identifier
8008 currently defined as a macro name is replaced by its replacement list of preprocessing
8009 tokens). The directive resulting after all replacements shall match one of the two
8010 previous forms and is then processed as appropriate.
8013 <h4><a name="6.10.5" href="#6.10.5">6.10.5 Error directive</a></h4>
8016 A preprocessing directive of the form
8018 # error pp-tokens<sub>opt</sub> new-line</pre>
8019 causes the implementation to produce a diagnostic message that includes the specified
8020 sequence of preprocessing tokens.
8022 <h4><a name="6.10.6" href="#6.10.6">6.10.6 Pragma directive</a></h4>
8025 A preprocessing directive of the form
8027 # pragma pp-tokens<sub>opt</sub> new-line</pre>
8028 where the preprocessing token STDC does not immediately follow pragma in the
8029 directive (prior to any macro replacement)<sup><a href="#note152"><b>152)</b></a></sup> causes the implementation to behave in an
8030 implementation-defined manner. The behavior might cause translation to fail or cause the
8031 translator or the resulting program to behave in a non-conforming manner. Any such
8032 pragma that is not recognized by the implementation is ignored.
8034 If the preprocessing token STDC does immediately follow pragma in the directive (prior
8035 to any macro replacement), then no macro replacement is performed on the directive, and
8036 the directive shall have one of the following forms<sup><a href="#note153"><b>153)</b></a></sup> whose meanings are described
8039 #pragma STDC FP_CONTRACT on-off-switch
8040 #pragma STDC FENV_ACCESS on-off-switch
8041 #pragma STDC CX_LIMITED_RANGE on-off-switch
8042 on-off-switch: one of
8043 ON OFF DEFAULT</pre>
8044 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
8045 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
8053 <p><small><a name="note152" href="#note152">152)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
8054 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
8055 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
8056 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
8057 but is not required to.
8059 <p><small><a name="note153" href="#note153">153)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
8062 <h4><a name="6.10.7" href="#6.10.7">6.10.7 Null directive</a></h4>
8065 A preprocessing directive of the form
8070 <h4><a name="6.10.8" href="#6.10.8">6.10.8 Predefined macro names</a></h4>
8072 The following macro names<sup><a href="#note154"><b>154)</b></a></sup> shall be defined by the implementation:
8074 <dt> __DATE__ <dd>The date of translation of the preprocessing translation unit: a character
8075 string literal of the form "Mmm dd yyyy", where the names of the
8076 months are the same as those generated by the asctime function, and the
8077 first character of dd is a space character if the value is less than 10. If the
8078 date of translation is not available, an implementation-defined valid date
8080 <dt> __FILE__ <dd>The presumed name of the current source file (a character string literal).<sup><a href="#note155"><b>155)</b></a></sup>
8081 <dt> __LINE__ <dd>The presumed line number (within the current source file) of the current
8082 source line (an integer constant).<sup><a href="#note155"><b>155)</b></a></sup>
8083 <dt> __STDC__ <dd>The integer constant 1, intended to indicate a conforming implementation.
8084 <dt> __STDC_HOSTED__ <dd>The integer constant 1 if the implementation is a hosted
8085 implementation or the integer constant 0 if it is not.
8086 <dt> __STDC_MB_MIGHT_NEQ_WC__ <dd>The integer constant 1, intended to indicate that, in
8087 the encoding for wchar_t, a member of the basic character set need not
8088 have a code value equal to its value when used as the lone character in an
8089 integer character constant.
8090 <dt> __STDC_VERSION__ <dd>The integer constant 199901L.<sup><a href="#note156"><b>156)</b></a></sup>
8091 <dt> __TIME__ <dd>The time of translation of the preprocessing translation unit: a character
8092 string literal of the form "hh:mm:ss" as in the time generated by the
8093 asctime function. If the time of translation is not available, an
8094 implementation-defined valid time shall be supplied.
8100 The following macro names are conditionally defined by the implementation:
8102 <dt> __STDC_IEC_559__ <dd>The integer constant 1, intended to indicate conformance to the
8103 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).
8104 <dt> __STDC_IEC_559_COMPLEX__ <dd>The integer constant 1, intended to indicate
8105 adherence to the specifications in informative <a href="#G">annex G</a> (IEC 60559
8106 compatible complex arithmetic).
8107 <dt> __STDC_ISO_10646__ <dd>An integer constant of the form yyyymmL (for example,
8108 199712L). If this symbol is defined, then every character in the Unicode
8109 required set, when stored in an object of type wchar_t, has the same
8110 value as the short identifier of that character. The Unicode required set
8111 consists of all the characters that are defined by ISO/IEC 10646, along with
8112 all amendments and technical corrigenda, as of the specified year and
8116 The values of the predefined macros (except for __FILE__ and __LINE__) remain
8117 constant throughout the translation unit.
8119 None of these macro names, nor the identifier defined, shall be the subject of a
8120 #define or a #undef preprocessing directive. Any other predefined macro names
8121 shall begin with a leading underscore followed by an uppercase letter or a second
8124 The implementation shall not predefine the macro __cplusplus, nor shall it define it
8125 in any standard header.
8126 <p><b> Forward references</b>: the asctime function (<a href="#7.23.3.1">7.23.3.1</a>), standard headers (<a href="#7.1.2">7.1.2</a>).
8129 <p><small><a name="note154" href="#note154">154)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
8131 <p><small><a name="note155" href="#note155">155)</a> The presumed source file name and line number can be changed by the #line directive.
8133 <p><small><a name="note156" href="#note156">156)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
8134 ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
8135 int that is increased with each revision of this International Standard.
8138 <h4><a name="6.10.9" href="#6.10.9">6.10.9 Pragma operator</a></h4>
8141 A unary operator expression of the form:
8143 _Pragma ( string-literal )</pre>
8144 is processed as follows: The string literal is destringized by deleting the L prefix, if
8145 present, deleting the leading and trailing double-quotes, replacing each escape sequence
8146 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
8147 resulting sequence of characters is processed through translation phase 3 to produce
8148 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
8149 directive. The original four preprocessing tokens in the unary operator expression are
8152 EXAMPLE A directive of the form:
8154 #pragma listing on "..\listing.dir"</pre>
8155 can also be expressed as:
8158 _Pragma ( "listing on \"..\\listing.dir\"" )</pre>
8159 The latter form is processed in the same way whether it appears literally as shown, or results from macro
8163 #define LISTING(x) PRAGMA(listing on #x)
8164 #define PRAGMA(x) _Pragma(#x)
8165 LISTING ( ..\listing.dir )</pre>
8167 <h3><a name="6.11" href="#6.11">6.11 Future language directions</a></h3>
8169 <h4><a name="6.11.1" href="#6.11.1">6.11.1 Floating types</a></h4>
8171 Future standardization may include additional floating-point types, including those with
8172 greater range, precision, or both than long double.
8174 <h4><a name="6.11.2" href="#6.11.2">6.11.2 Linkages of identifiers</a></h4>
8176 Declaring an identifier with internal linkage at file scope without the static storage-
8177 class specifier is an obsolescent feature.
8179 <h4><a name="6.11.3" href="#6.11.3">6.11.3 External names</a></h4>
8181 Restriction of the significance of an external name to fewer than 255 characters
8182 (considering each universal character name or extended source character as a single
8183 character) is an obsolescent feature that is a concession to existing implementations.
8185 <h4><a name="6.11.4" href="#6.11.4">6.11.4 Character escape sequences</a></h4>
8187 Lowercase letters as escape sequences are reserved for future standardization. Other
8188 characters may be used in extensions.
8190 <h4><a name="6.11.5" href="#6.11.5">6.11.5 Storage-class specifiers</a></h4>
8192 The placement of a storage-class specifier other than at the beginning of the declaration
8193 specifiers in a declaration is an obsolescent feature.
8195 <h4><a name="6.11.6" href="#6.11.6">6.11.6 Function declarators</a></h4>
8197 The use of function declarators with empty parentheses (not prototype-format parameter
8198 type declarators) is an obsolescent feature.
8200 <h4><a name="6.11.7" href="#6.11.7">6.11.7 Function definitions</a></h4>
8202 The use of function definitions with separate parameter identifier and declaration lists
8203 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
8205 <h4><a name="6.11.8" href="#6.11.8">6.11.8 Pragma directives</a></h4>
8207 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
8209 <h4><a name="6.11.9" href="#6.11.9">6.11.9 Predefined macro names</a></h4>
8211 Macro names beginning with __STDC_ are reserved for future standardization.
8214 <h2><a name="7" href="#7">7. Library</a></h2>
8217 <h3><a name="7.1" href="#7.1">7.1 Introduction</a></h3>
8219 <h4><a name="7.1.1" href="#7.1.1">7.1.1 Definitions of terms</a></h4>
8221 A string is a contiguous sequence of characters terminated by and including the first null
8222 character. The term multibyte string is sometimes used instead to emphasize special
8223 processing given to multibyte characters contained in the string or to avoid confusion
8224 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
8225 character. The length of a string is the number of bytes preceding the null character and
8226 the value of a string is the sequence of the values of the contained characters, in order.
8228 The decimal-point character is the character used by functions that convert floating-point
8229 numbers to or from character sequences to denote the beginning of the fractional part of
8230 such character sequences.<sup><a href="#note157"><b>157)</b></a></sup> It is represented in the text and examples by a period, but
8231 may be changed by the setlocale function.
8233 A null wide character is a wide character with code value zero.
8235 A wide string is a contiguous sequence of wide characters terminated by and including
8236 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
8237 addressed) wide character. The length of a wide string is the number of wide characters
8238 preceding the null wide character and the value of a wide string is the sequence of code
8239 values of the contained wide characters, in order.
8241 A shift sequence is a contiguous sequence of bytes within a multibyte string that
8242 (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
8243 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
8244 character.<sup><a href="#note158"><b>158)</b></a></sup>
8245 <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>).
8253 <p><small><a name="note157" href="#note157">157)</a> The functions that make use of the decimal-point character are the numeric conversion functions
8254 (<a href="#7.20.1">7.20.1</a>, <a href="#7.24.4.1">7.24.4.1</a>) and the formatted input/output functions (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
8256 <p><small><a name="note158" href="#note158">158)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
8257 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
8258 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
8259 implementation's choice.
8262 <h4><a name="7.1.2" href="#7.1.2">7.1.2 Standard headers</a></h4>
8264 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note159"><b>159)</b></a></sup>
8265 whose contents are made available by the #include preprocessing directive. The
8266 header declares a set of related functions, plus any necessary types and additional macros
8267 needed to facilitate their use. Declarations of types described in this clause shall not
8268 include type qualifiers, unless explicitly stated otherwise.
8270 The standard headers are
8273 <a href="#7.2"><assert.h></a> <a href="#7.8"><inttypes.h></a> <a href="#7.14"><signal.h></a> <a href="#7.20"><stdlib.h></a>
8274 <a href="#7.3"><complex.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.15"><stdarg.h></a> <a href="#7.21"><string.h></a>
8275 <a href="#7.4"><ctype.h></a> <a href="#7.10"><limits.h></a> <a href="#7.16"><stdbool.h></a> <a href="#7.22"><tgmath.h></a>
8276 <a href="#7.5"><errno.h></a> <a href="#7.11"><locale.h></a> <a href="#7.17"><stddef.h></a> <a href="#7.23"><time.h></a>
8277 <a href="#7.6"><fenv.h></a> <a href="#7.12"><math.h></a> <a href="#7.18"><stdint.h></a> <a href="#7.24"><wchar.h></a>
8278 <a href="#7.7"><float.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.19"><stdio.h></a> <a href="#7.25"><wctype.h></a></pre>
8279 If a file with the same name as one of the above < and > delimited sequences, not
8280 provided as part of the implementation, is placed in any of the standard places that are
8281 searched for included source files, the behavior is undefined.
8283 Standard headers may be included in any order; each may be included more than once in
8284 a given scope, with no effect different from being included only once, except that the
8285 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
8286 used, a header shall be included outside of any external declaration or definition, and it
8287 shall first be included before the first reference to any of the functions or objects it
8288 declares, or to any of the types or macros it defines. However, if an identifier is declared
8289 or defined in more than one header, the second and subsequent associated headers may be
8290 included after the initial reference to the identifier. The program shall not have any
8291 macros with names lexically identical to keywords currently defined prior to the
8294 Any definition of an object-like macro described in this clause shall expand to code that is
8295 fully protected by parentheses where necessary, so that it groups in an arbitrary
8296 expression as if it were a single identifier.
8298 Any declaration of a library function shall have external linkage.
8300 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
8301 <p><b> Forward references</b>: diagnostics (<a href="#7.2">7.2</a>).
8309 <p><small><a name="note159" href="#note159">159)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
8310 necessarily valid source file names.
8313 <h4><a name="7.1.3" href="#7.1.3">7.1.3 Reserved identifiers</a></h4>
8315 Each header declares or defines all identifiers listed in its associated subclause, and
8316 optionally declares or defines identifiers listed in its associated future library directions
8317 subclause and identifiers which are always reserved either for any use or for use as file
8320 <li> All identifiers that begin with an underscore and either an uppercase letter or another
8321 underscore are always reserved for any use.
8322 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
8323 with file scope in both the ordinary and tag name spaces.
8324 <li> Each macro name in any of the following subclauses (including the future library
8325 directions) is reserved for use as specified if any of its associated headers is included;
8326 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
8327 <li> All identifiers with external linkage in any of the following subclauses (including the
8328 future library directions) are always reserved for use as identifiers with external
8329 linkage.<sup><a href="#note160"><b>160)</b></a></sup>
8330 <li> Each identifier with file scope listed in any of the following subclauses (including the
8331 future library directions) is reserved for use as a macro name and as an identifier with
8332 file scope in the same name space if any of its associated headers is included.
8335 No other identifiers are reserved. If the program declares or defines an identifier in a
8336 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
8337 identifier as a macro name, the behavior is undefined.
8339 If the program removes (with #undef) any macro definition of an identifier in the first
8340 group listed above, the behavior is undefined.
8343 <p><small><a name="note160" href="#note160">160)</a> The list of reserved identifiers with external linkage includes errno, math_errhandling,
8347 <h4><a name="7.1.4" href="#7.1.4">7.1.4 Use of library functions</a></h4>
8349 Each of the following statements applies unless explicitly stated otherwise in the detailed
8350 descriptions that follow: If an argument to a function has an invalid value (such as a value
8351 outside the domain of the function, or a pointer outside the address space of the program,
8352 or a null pointer, or a pointer to non-modifiable storage when the corresponding
8353 parameter is not const-qualified) or a type (after promotion) not expected by a function
8354 with variable number of arguments, the behavior is undefined. If a function argument is
8355 described as being an array, the pointer actually passed to the function shall have a value
8356 such that all address computations and accesses to objects (that would be valid if the
8357 pointer did point to the first element of such an array) are in fact valid. Any function
8358 declared in a header may be additionally implemented as a function-like macro defined in
8361 the header, so if a library function is declared explicitly when its header is included, one
8362 of the techniques shown below can be used to ensure the declaration is not affected by
8363 such a macro. Any macro definition of a function can be suppressed locally by enclosing
8364 the name of the function in parentheses, because the name is then not followed by the left
8365 parenthesis that indicates expansion of a macro function name. For the same syntactic
8366 reason, it is permitted to take the address of a library function even if it is also defined as
8367 a macro.<sup><a href="#note161"><b>161)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
8368 actual function is referred to. Any invocation of a library function that is implemented as
8369 a macro shall expand to code that evaluates each of its arguments exactly once, fully
8370 protected by parentheses where necessary, so it is generally safe to use arbitrary
8371 expressions as arguments.<sup><a href="#note162"><b>162)</b></a></sup> Likewise, those function-like macros described in the
8372 following subclauses may be invoked in an expression anywhere a function with a
8373 compatible return type could be called.<sup><a href="#note163"><b>163)</b></a></sup> All object-like macros listed as expanding to
8374 integer constant expressions shall additionally be suitable for use in #if preprocessing
8377 Provided that a library function can be declared without reference to any type defined in a
8378 header, it is also permissible to declare the function and use it without including its
8381 There is a sequence point immediately before a library function returns.
8383 The functions in the standard library are not guaranteed to be reentrant and may modify
8384 objects with static storage duration.<sup><a href="#note164"><b>164)</b></a></sup>
8390 EXAMPLE The function atoi may be used in any of several ways:
8392 <li> by use of its associated header (possibly generating a macro expansion)
8394 #include <a href="#7.20"><stdlib.h></a>
8397 i = atoi(str);</pre>
8398 <li> by use of its associated header (assuredly generating a true function reference)
8400 #include <a href="#7.20"><stdlib.h></a>
8404 i = atoi(str);</pre>
8407 #include <a href="#7.20"><stdlib.h></a>
8410 i = (atoi)(str);</pre>
8411 <li> by explicit declaration
8414 extern int atoi(const char *);
8417 i = atoi(str);</pre>
8421 <p><small><a name="note161" href="#note161">161)</a> This means that an implementation shall provide an actual function for each library function, even if it
8422 also provides a macro for that function.
8424 <p><small><a name="note162" href="#note162">162)</a> Such macros might not contain the sequence points that the corresponding function calls do.
8426 <p><small><a name="note163" href="#note163">163)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
8427 implementations may provide special semantics for such names. For example, the identifier
8428 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
8429 appropriate header could specify
8432 #define abs(x) _BUILTIN_abs(x)</pre>
8433 for a compiler whose code generator will accept it.
8434 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
8439 whether the implementation's header provides a macro implementation of abs or a built-in
8440 implementation. The prototype for the function, which precedes and is hidden by any macro
8441 definition, is thereby revealed also.
8443 <p><small><a name="note164" href="#note164">164)</a> Thus, a signal handler cannot, in general, call standard library functions.
8446 <h3><a name="7.2" href="#7.2">7.2 Diagnostics <assert.h></a></h3>
8448 The header <a href="#7.2"><assert.h></a> defines the assert macro and refers to another macro,
8451 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8452 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8455 #define assert(ignore) ((void)0)</pre>
8456 The assert macro is redefined according to the current state of NDEBUG each time that
8457 <a href="#7.2"><assert.h></a> is included.
8459 The assert macro shall be implemented as a macro, not as an actual function. If the
8460 macro definition is suppressed in order to access an actual function, the behavior is
8463 <h4><a name="7.2.1" href="#7.2.1">7.2.1 Program diagnostics</a></h4>
8465 <h5><a name="7.2.1.1" href="#7.2.1.1">7.2.1.1 The assert macro</a></h5>
8469 #include <a href="#7.2"><assert.h></a>
8470 void assert(scalar expression);</pre>
8471 <h6>Description</h6>
8473 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8474 When it is executed, if expression (which shall have a scalar type) is false (that is,
8475 compares equal to 0), the assert macro writes information about the particular call that
8476 failed (including the text of the argument, the name of the source file, the source line
8477 number, and the name of the enclosing function -- the latter are respectively the values of
8478 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8479 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note165"><b>165)</b></a></sup> It
8480 then calls the abort function.
8483 The assert macro returns no value.
8484 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>).
8492 <p><small><a name="note165" href="#note165">165)</a> The message written might be of the form:
8493 Assertion failed: expression, function abc, file xyz, line nnn.
8496 <h3><a name="7.3" href="#7.3">7.3 Complex arithmetic <complex.h></a></h3>
8498 <h4><a name="7.3.1" href="#7.3.1">7.3.1 Introduction</a></h4>
8500 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8501 arithmetic.<sup><a href="#note166"><b>166)</b></a></sup> Each synopsis specifies a family of functions consisting of a principal
8502 function with one or more double complex parameters and a double complex or
8503 double return value; and other functions with the same name but with f and l suffixes
8504 which are corresponding functions with float and long double parameters and
8510 expands to _Complex; the macro
8513 expands to a constant expression of type const float _Complex, with the value of
8514 the imaginary unit.<sup><a href="#note167"><b>167)</b></a></sup>
8522 are defined if and only if the implementation supports imaginary types;<sup><a href="#note168"><b>168)</b></a></sup> if defined,
8523 they expand to _Imaginary and a constant expression of type const float
8524 _Imaginary with the value of the imaginary unit.
8529 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8530 defined, I shall expand to _Complex_I.
8532 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8533 redefine the macros complex, imaginary, and I.
8534 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8541 <p><small><a name="note166" href="#note166">166)</a> See ''future library directions'' (<a href="#7.26.1">7.26.1</a>).
8543 <p><small><a name="note167" href="#note167">167)</a> The imaginary unit is a number i such that i 2 = -1.
8545 <p><small><a name="note168" href="#note168">168)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8548 <h4><a name="7.3.2" href="#7.3.2">7.3.2 Conventions</a></h4>
8550 Values are interpreted as radians, not degrees. An implementation may set errno but is
8553 <h4><a name="7.3.3" href="#7.3.3">7.3.3 Branch cuts</a></h4>
8555 Some of the functions below have branch cuts, across which the function is
8556 discontinuous. For implementations with a signed zero (including all IEC 60559
8557 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8558 one side of a cut from another so the function is continuous (except for format
8559 limitations) as the cut is approached from either side. For example, for the square root
8560 function, which has a branch cut along the negative real axis, the top of the cut, with
8561 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8562 imaginary part -0, maps to the negative imaginary axis.
8564 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8565 sides of branch cuts. These implementations shall map a cut so the function is continuous
8566 as the cut is approached coming around the finite endpoint of the cut in a counter
8567 clockwise direction. (Branch cuts for the functions specified here have just one finite
8568 endpoint.) For example, for the square root function, coming counter clockwise around
8569 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8570 so the cut maps to the positive imaginary axis.
8572 <h4><a name="7.3.4" href="#7.3.4">7.3.4 The CX_LIMITED_RANGE pragma</a></h4>
8576 #include <a href="#7.3"><complex.h></a>
8577 #pragma STDC CX_LIMITED_RANGE on-off-switch</pre>
8578 <h6>Description</h6>
8580 The usual mathematical formulas for complex multiply, divide, and absolute value are
8581 problematic because of their treatment of infinities and because of undue overflow and
8582 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8583 implementation that (where the state is ''on'') the usual mathematical formulas are
8584 acceptable.<sup><a href="#note169"><b>169)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8585 explicit declarations and statements inside a compound statement. When outside external
8588 declarations, the pragma takes effect from its occurrence until another
8589 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8590 When inside a compound statement, the pragma takes effect from its occurrence until
8591 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8592 compound statement), or until the end of the compound statement; at the end of a
8593 compound statement the state for the pragma is restored to its condition just before the
8594 compound statement. If this pragma is used in any other context, the behavior is
8595 undefined. The default state for the pragma is ''off''.
8598 <p><small><a name="note169" href="#note169">169)</a> The purpose of the pragma is to allow the implementation to use the formulas:
8601 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8602 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8603 | x + iy | = (sqrt) x 2 + y 2
8604 ???????????????</pre>
8605 where the programmer can determine they are safe.
8608 <h4><a name="7.3.5" href="#7.3.5">7.3.5 Trigonometric functions</a></h4>
8610 <h5><a name="7.3.5.1" href="#7.3.5.1">7.3.5.1 The cacos functions</a></h5>
8614 #include <a href="#7.3"><complex.h></a>
8615 double complex cacos(double complex z);
8616 float complex cacosf(float complex z);
8617 long double complex cacosl(long double complex z);</pre>
8618 <h6>Description</h6>
8620 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8621 interval [-1, +1] along the real axis.
8624 The cacos functions return the complex arc cosine value, in the range of a strip
8625 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8628 <h5><a name="7.3.5.2" href="#7.3.5.2">7.3.5.2 The casin functions</a></h5>
8632 #include <a href="#7.3"><complex.h></a>
8633 double complex casin(double complex z);
8634 float complex casinf(float complex z);
8635 long double complex casinl(long double complex z);</pre>
8636 <h6>Description</h6>
8638 The casin functions compute the complex arc sine of z, with branch cuts outside the
8639 interval [-1, +1] along the real axis.
8642 The casin functions return the complex arc sine value, in the range of a strip
8643 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8644 along the real axis.
8647 <h5><a name="7.3.5.3" href="#7.3.5.3">7.3.5.3 The catan functions</a></h5>
8651 #include <a href="#7.3"><complex.h></a>
8652 double complex catan(double complex z);
8653 float complex catanf(float complex z);
8654 long double complex catanl(long double complex z);</pre>
8655 <h6>Description</h6>
8657 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8658 interval [-i, +i] along the imaginary axis.
8661 The catan functions return the complex arc tangent value, in the range of a strip
8662 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8663 along the real axis.
8665 <h5><a name="7.3.5.4" href="#7.3.5.4">7.3.5.4 The ccos functions</a></h5>
8669 #include <a href="#7.3"><complex.h></a>
8670 double complex ccos(double complex z);
8671 float complex ccosf(float complex z);
8672 long double complex ccosl(long double complex z);</pre>
8673 <h6>Description</h6>
8675 The ccos functions compute the complex cosine of z.
8678 The ccos functions return the complex cosine value.
8680 <h5><a name="7.3.5.5" href="#7.3.5.5">7.3.5.5 The csin functions</a></h5>
8684 #include <a href="#7.3"><complex.h></a>
8685 double complex csin(double complex z);
8686 float complex csinf(float complex z);
8687 long double complex csinl(long double complex z);</pre>
8688 <h6>Description</h6>
8690 The csin functions compute the complex sine of z.
8693 The csin functions return the complex sine value.
8696 <h5><a name="7.3.5.6" href="#7.3.5.6">7.3.5.6 The ctan functions</a></h5>
8700 #include <a href="#7.3"><complex.h></a>
8701 double complex ctan(double complex z);
8702 float complex ctanf(float complex z);
8703 long double complex ctanl(long double complex z);</pre>
8704 <h6>Description</h6>
8706 The ctan functions compute the complex tangent of z.
8709 The ctan functions return the complex tangent value.
8711 <h4><a name="7.3.6" href="#7.3.6">7.3.6 Hyperbolic functions</a></h4>
8713 <h5><a name="7.3.6.1" href="#7.3.6.1">7.3.6.1 The cacosh functions</a></h5>
8717 #include <a href="#7.3"><complex.h></a>
8718 double complex cacosh(double complex z);
8719 float complex cacoshf(float complex z);
8720 long double complex cacoshl(long double complex z);</pre>
8721 <h6>Description</h6>
8723 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8724 cut at values less than 1 along the real axis.
8727 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8728 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
8731 <h5><a name="7.3.6.2" href="#7.3.6.2">7.3.6.2 The casinh functions</a></h5>
8735 #include <a href="#7.3"><complex.h></a>
8736 double complex casinh(double complex z);
8737 float complex casinhf(float complex z);
8738 long double complex casinhl(long double complex z);</pre>
8739 <h6>Description</h6>
8741 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8742 outside the interval [-i, +i] along the imaginary axis.
8746 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8747 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8748 along the imaginary axis.
8750 <h5><a name="7.3.6.3" href="#7.3.6.3">7.3.6.3 The catanh functions</a></h5>
8754 #include <a href="#7.3"><complex.h></a>
8755 double complex catanh(double complex z);
8756 float complex catanhf(float complex z);
8757 long double complex catanhl(long double complex z);</pre>
8758 <h6>Description</h6>
8760 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8761 cuts outside the interval [-1, +1] along the real axis.
8764 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8765 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8766 along the imaginary axis.
8768 <h5><a name="7.3.6.4" href="#7.3.6.4">7.3.6.4 The ccosh functions</a></h5>
8772 #include <a href="#7.3"><complex.h></a>
8773 double complex ccosh(double complex z);
8774 float complex ccoshf(float complex z);
8775 long double complex ccoshl(long double complex z);</pre>
8776 <h6>Description</h6>
8778 The ccosh functions compute the complex hyperbolic cosine of z.
8781 The ccosh functions return the complex hyperbolic cosine value.
8783 <h5><a name="7.3.6.5" href="#7.3.6.5">7.3.6.5 The csinh functions</a></h5>
8788 #include <a href="#7.3"><complex.h></a>
8789 double complex csinh(double complex z);
8790 float complex csinhf(float complex z);
8791 long double complex csinhl(long double complex z);</pre>
8792 <h6>Description</h6>
8794 The csinh functions compute the complex hyperbolic sine of z.
8797 The csinh functions return the complex hyperbolic sine value.
8799 <h5><a name="7.3.6.6" href="#7.3.6.6">7.3.6.6 The ctanh functions</a></h5>
8803 #include <a href="#7.3"><complex.h></a>
8804 double complex ctanh(double complex z);
8805 float complex ctanhf(float complex z);
8806 long double complex ctanhl(long double complex z);</pre>
8807 <h6>Description</h6>
8809 The ctanh functions compute the complex hyperbolic tangent of z.
8812 The ctanh functions return the complex hyperbolic tangent value.
8814 <h4><a name="7.3.7" href="#7.3.7">7.3.7 Exponential and logarithmic functions</a></h4>
8816 <h5><a name="7.3.7.1" href="#7.3.7.1">7.3.7.1 The cexp functions</a></h5>
8820 #include <a href="#7.3"><complex.h></a>
8821 double complex cexp(double complex z);
8822 float complex cexpf(float complex z);
8823 long double complex cexpl(long double complex z);</pre>
8824 <h6>Description</h6>
8826 The cexp functions compute the complex base-e exponential of z.
8829 The cexp functions return the complex base-e exponential value.
8831 <h5><a name="7.3.7.2" href="#7.3.7.2">7.3.7.2 The clog functions</a></h5>
8836 #include <a href="#7.3"><complex.h></a>
8837 double complex clog(double complex z);
8838 float complex clogf(float complex z);
8839 long double complex clogl(long double complex z);</pre>
8840 <h6>Description</h6>
8842 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8843 cut along the negative real axis.
8846 The clog functions return the complex natural logarithm value, in the range of a strip
8847 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8850 <h4><a name="7.3.8" href="#7.3.8">7.3.8 Power and absolute-value functions</a></h4>
8852 <h5><a name="7.3.8.1" href="#7.3.8.1">7.3.8.1 The cabs functions</a></h5>
8856 #include <a href="#7.3"><complex.h></a>
8857 double cabs(double complex z);
8858 float cabsf(float complex z);
8859 long double cabsl(long double complex z);</pre>
8860 <h6>Description</h6>
8862 The cabs functions compute the complex absolute value (also called norm, modulus, or
8866 The cabs functions return the complex absolute value.
8868 <h5><a name="7.3.8.2" href="#7.3.8.2">7.3.8.2 The cpow functions</a></h5>
8872 #include <a href="#7.3"><complex.h></a>
8873 double complex cpow(double complex x, double complex y);
8874 float complex cpowf(float complex x, float complex y);
8875 long double complex cpowl(long double complex x,
8876 long double complex y);</pre>
8877 <h6>Description</h6>
8879 The cpow functions compute the complex power function xy , with a branch cut for the
8880 first parameter along the negative real axis.
8883 The cpow functions return the complex power function value.
8886 <h5><a name="7.3.8.3" href="#7.3.8.3">7.3.8.3 The csqrt functions</a></h5>
8890 #include <a href="#7.3"><complex.h></a>
8891 double complex csqrt(double complex z);
8892 float complex csqrtf(float complex z);
8893 long double complex csqrtl(long double complex z);</pre>
8894 <h6>Description</h6>
8896 The csqrt functions compute the complex square root of z, with a branch cut along the
8900 The csqrt functions return the complex square root value, in the range of the right half-
8901 plane (including the imaginary axis).
8903 <h4><a name="7.3.9" href="#7.3.9">7.3.9 Manipulation functions</a></h4>
8905 <h5><a name="7.3.9.1" href="#7.3.9.1">7.3.9.1 The carg functions</a></h5>
8909 #include <a href="#7.3"><complex.h></a>
8910 double carg(double complex z);
8911 float cargf(float complex z);
8912 long double cargl(long double complex z);</pre>
8913 <h6>Description</h6>
8915 The carg functions compute the argument (also called phase angle) of z, with a branch
8916 cut along the negative real axis.
8919 The carg functions return the value of the argument in the interval [-pi , +pi ].
8921 <h5><a name="7.3.9.2" href="#7.3.9.2">7.3.9.2 The cimag functions</a></h5>
8926 #include <a href="#7.3"><complex.h></a>
8927 double cimag(double complex z);
8928 float cimagf(float complex z);
8929 long double cimagl(long double complex z);</pre>
8930 <h6>Description</h6>
8932 The cimag functions compute the imaginary part of z.<sup><a href="#note170"><b>170)</b></a></sup>
8935 The cimag functions return the imaginary part value (as a real).
8938 <p><small><a name="note170" href="#note170">170)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8941 <h5><a name="7.3.9.3" href="#7.3.9.3">7.3.9.3 The conj functions</a></h5>
8945 #include <a href="#7.3"><complex.h></a>
8946 double complex conj(double complex z);
8947 float complex conjf(float complex z);
8948 long double complex conjl(long double complex z);</pre>
8949 <h6>Description</h6>
8951 The conj functions compute the complex conjugate of z, by reversing the sign of its
8955 The conj functions return the complex conjugate value.
8957 <h5><a name="7.3.9.4" href="#7.3.9.4">7.3.9.4 The cproj functions</a></h5>
8961 #include <a href="#7.3"><complex.h></a>
8962 double complex cproj(double complex z);
8963 float complex cprojf(float complex z);
8964 long double complex cprojl(long double complex z);</pre>
8965 <h6>Description</h6>
8967 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8968 z except that all complex infinities (even those with one infinite part and one NaN part)
8969 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8972 INFINITY + I * copysign(0.0, cimag(z))</pre>
8975 The cproj functions return the value of the projection onto the Riemann sphere.
8982 <h5><a name="7.3.9.5" href="#7.3.9.5">7.3.9.5 The creal functions</a></h5>
8986 #include <a href="#7.3"><complex.h></a>
8987 double creal(double complex z);
8988 float crealf(float complex z);
8989 long double creall(long double complex z);</pre>
8990 <h6>Description</h6>
8992 The creal functions compute the real part of z.<sup><a href="#note171"><b>171)</b></a></sup>
8995 The creal functions return the real part value.
9003 <p><small><a name="note171" href="#note171">171)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9006 <h3><a name="7.4" href="#7.4">7.4 Character handling <ctype.h></a></h3>
9008 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
9009 characters.<sup><a href="#note172"><b>172)</b></a></sup> In all cases the argument is an int, the value of which shall be
9010 representable as an unsigned char or shall equal the value of the macro EOF. If the
9011 argument has any other value, the behavior is undefined.
9013 The behavior of these functions is affected by the current locale. Those functions that
9014 have locale-specific aspects only when not in the "C" locale are noted below.
9016 The term printing character refers to a member of a locale-specific set of characters, each
9017 of which occupies one printing position on a display device; the term control character
9018 refers to a member of a locale-specific set of characters that are not printing
9019 characters.<sup><a href="#note173"><b>173)</b></a></sup> All letters and digits are printing characters.
9020 <p><b> Forward references</b>: EOF (<a href="#7.19.1">7.19.1</a>), localization (<a href="#7.11">7.11</a>).
9023 <p><small><a name="note172" href="#note172">172)</a> See ''future library directions'' (<a href="#7.26.2">7.26.2</a>).
9025 <p><small><a name="note173" href="#note173">173)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
9026 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
9027 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
9030 <h4><a name="7.4.1" href="#7.4.1">7.4.1 Character classification functions</a></h4>
9032 The functions in this subclause return nonzero (true) if and only if the value of the
9033 argument c conforms to that in the description of the function.
9035 <h5><a name="7.4.1.1" href="#7.4.1.1">7.4.1.1 The isalnum function</a></h5>
9039 #include <a href="#7.4"><ctype.h></a>
9040 int isalnum(int c);</pre>
9041 <h6>Description</h6>
9043 The isalnum function tests for any character for which isalpha or isdigit is true.
9045 <h5><a name="7.4.1.2" href="#7.4.1.2">7.4.1.2 The isalpha function</a></h5>
9049 #include <a href="#7.4"><ctype.h></a>
9050 int isalpha(int c);</pre>
9051 <h6>Description</h6>
9053 The isalpha function tests for any character for which isupper or islower is true,
9054 or any character that is one of a locale-specific set of alphabetic characters for which
9059 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note174"><b>174)</b></a></sup> In the "C" locale,
9060 isalpha returns true only for the characters for which isupper or islower is true.
9063 <p><small><a name="note174" href="#note174">174)</a> The functions islower and isupper test true or false separately for each of these additional
9064 characters; all four combinations are possible.
9067 <h5><a name="7.4.1.3" href="#7.4.1.3">7.4.1.3 The isblank function</a></h5>
9071 #include <a href="#7.4"><ctype.h></a>
9072 int isblank(int c);</pre>
9073 <h6>Description</h6>
9075 The isblank function tests for any character that is a standard blank character or is one
9076 of a locale-specific set of characters for which isspace is true and that is used to
9077 separate words within a line of text. The standard blank characters are the following:
9078 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
9079 for the standard blank characters.
9081 <h5><a name="7.4.1.4" href="#7.4.1.4">7.4.1.4 The iscntrl function</a></h5>
9085 #include <a href="#7.4"><ctype.h></a>
9086 int iscntrl(int c);</pre>
9087 <h6>Description</h6>
9089 The iscntrl function tests for any control character.
9091 <h5><a name="7.4.1.5" href="#7.4.1.5">7.4.1.5 The isdigit function</a></h5>
9095 #include <a href="#7.4"><ctype.h></a>
9096 int isdigit(int c);</pre>
9097 <h6>Description</h6>
9099 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
9101 <h5><a name="7.4.1.6" href="#7.4.1.6">7.4.1.6 The isgraph function</a></h5>
9105 #include <a href="#7.4"><ctype.h></a>
9106 int isgraph(int c);</pre>
9112 <h6>Description</h6>
9114 The isgraph function tests for any printing character except space (' ').
9116 <h5><a name="7.4.1.7" href="#7.4.1.7">7.4.1.7 The islower function</a></h5>
9120 #include <a href="#7.4"><ctype.h></a>
9121 int islower(int c);</pre>
9122 <h6>Description</h6>
9124 The islower function tests for any character that is a lowercase letter or is one of a
9125 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9126 isspace is true. In the "C" locale, islower returns true only for the lowercase
9127 letters (as defined in <a href="#5.2.1">5.2.1</a>).
9129 <h5><a name="7.4.1.8" href="#7.4.1.8">7.4.1.8 The isprint function</a></h5>
9133 #include <a href="#7.4"><ctype.h></a>
9134 int isprint(int c);</pre>
9135 <h6>Description</h6>
9137 The isprint function tests for any printing character including space (' ').
9139 <h5><a name="7.4.1.9" href="#7.4.1.9">7.4.1.9 The ispunct function</a></h5>
9143 #include <a href="#7.4"><ctype.h></a>
9144 int ispunct(int c);</pre>
9145 <h6>Description</h6>
9147 The ispunct function tests for any printing character that is one of a locale-specific set
9148 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
9149 locale, ispunct returns true for every printing character for which neither isspace
9150 nor isalnum is true.
9152 <h5><a name="7.4.1.10" href="#7.4.1.10">7.4.1.10 The isspace function</a></h5>
9156 #include <a href="#7.4"><ctype.h></a>
9157 int isspace(int c);</pre>
9158 <h6>Description</h6>
9160 The isspace function tests for any character that is a standard white-space character or
9161 is one of a locale-specific set of characters for which isalnum is false. The standard
9163 white-space characters are the following: space (' '), form feed ('\f'), new-line
9164 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
9165 "C" locale, isspace returns true only for the standard white-space characters.
9167 <h5><a name="7.4.1.11" href="#7.4.1.11">7.4.1.11 The isupper function</a></h5>
9171 #include <a href="#7.4"><ctype.h></a>
9172 int isupper(int c);</pre>
9173 <h6>Description</h6>
9175 The isupper function tests for any character that is an uppercase letter or is one of a
9176 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9177 isspace is true. In the "C" locale, isupper returns true only for the uppercase
9178 letters (as defined in <a href="#5.2.1">5.2.1</a>).
9180 <h5><a name="7.4.1.12" href="#7.4.1.12">7.4.1.12 The isxdigit function</a></h5>
9184 #include <a href="#7.4"><ctype.h></a>
9185 int isxdigit(int c);</pre>
9186 <h6>Description</h6>
9188 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
9190 <h4><a name="7.4.2" href="#7.4.2">7.4.2 Character case mapping functions</a></h4>
9192 <h5><a name="7.4.2.1" href="#7.4.2.1">7.4.2.1 The tolower function</a></h5>
9196 #include <a href="#7.4"><ctype.h></a>
9197 int tolower(int c);</pre>
9198 <h6>Description</h6>
9200 The tolower function converts an uppercase letter to a corresponding lowercase letter.
9203 If the argument is a character for which isupper is true and there are one or more
9204 corresponding characters, as specified by the current locale, for which islower is true,
9205 the tolower function returns one of the corresponding characters (always the same one
9206 for any given locale); otherwise, the argument is returned unchanged.
9209 <h5><a name="7.4.2.2" href="#7.4.2.2">7.4.2.2 The toupper function</a></h5>
9213 #include <a href="#7.4"><ctype.h></a>
9214 int toupper(int c);</pre>
9215 <h6>Description</h6>
9217 The toupper function converts a lowercase letter to a corresponding uppercase letter.
9220 If the argument is a character for which islower is true and there are one or more
9221 corresponding characters, as specified by the current locale, for which isupper is true,
9222 the toupper function returns one of the corresponding characters (always the same one
9223 for any given locale); otherwise, the argument is returned unchanged.
9226 <h3><a name="7.5" href="#7.5">7.5 Errors <errno.h></a></h3>
9228 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
9236 which expand to integer constant expressions with type int, distinct positive values, and
9237 which are suitable for use in #if preprocessing directives; and
9240 which expands to a modifiable lvalue<sup><a href="#note175"><b>175)</b></a></sup> that has type int, the value of which is set to a
9241 positive error number by several library functions. It is unspecified whether errno is a
9242 macro or an identifier declared with external linkage. If a macro definition is suppressed
9243 in order to access an actual object, or a program defines an identifier with the name
9244 errno, the behavior is undefined.
9246 The value of errno is zero at program startup, but is never set to zero by any library
9247 function.<sup><a href="#note176"><b>176)</b></a></sup> The value of errno may be set to nonzero by a library function call
9248 whether or not there is an error, provided the use of errno is not documented in the
9249 description of the function in this International Standard.
9251 Additional macro definitions, beginning with E and a digit or E and an uppercase
9252 letter,<sup><a href="#note177"><b>177)</b></a></sup> may also be specified by the implementation.
9260 <p><small><a name="note175" href="#note175">175)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
9261 resulting from a function call (for example, *errno()).
9263 <p><small><a name="note176" href="#note176">176)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
9264 then inspect it before a subsequent library function call. Of course, a library function can save the
9265 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
9266 value is still zero just before the return.
9268 <p><small><a name="note177" href="#note177">177)</a> See ''future library directions'' (<a href="#7.26.3">7.26.3</a>).
9271 <h3><a name="7.6" href="#7.6">7.6 Floating-point environment <fenv.h></a></h3>
9273 The header <a href="#7.6"><fenv.h></a> declares two types and several macros and functions to provide
9274 access to the floating-point environment. The floating-point environment refers
9275 collectively to any floating-point status flags and control modes supported by the
9276 implementation.<sup><a href="#note178"><b>178)</b></a></sup> A floating-point status flag is a system variable whose value is set
9277 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
9278 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note179"><b>179)</b></a></sup> A floating-
9279 point control mode is a system variable whose value may be set by the user to affect the
9280 subsequent behavior of floating-point arithmetic.
9282 Certain programming conventions support the intended model of use for the floating-
9283 point environment:<sup><a href="#note180"><b>180)</b></a></sup>
9285 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
9286 floating-point status flags, nor depend on the state of its caller's floating-point status
9287 flags unless the function is so documented;
9288 <li> a function call is assumed to require default floating-point control modes, unless its
9289 documentation promises otherwise;
9290 <li> a function call is assumed to have the potential for raising floating-point exceptions,
9291 unless its documentation promises otherwise.
9297 represents the entire floating-point environment.
9302 represents the floating-point status flags collectively, including any status the
9303 implementation associates with the flags.
9317 is defined if and only if the implementation supports the floating-point exception by
9318 means of the functions in 7.6.2.<sup><a href="#note181"><b>181)</b></a></sup> Additional implementation-defined floating-point
9319 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
9320 be specified by the implementation. The defined macros expand to integer constant
9321 expressions with values such that bitwise ORs of all combinations of the macros result in
9322 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
9323 zero.<sup><a href="#note182"><b>182)</b></a></sup>
9328 is simply the bitwise OR of all floating-point exception macros defined by the
9329 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
9337 is defined if and only if the implementation supports getting and setting the represented
9338 rounding direction by means of the fegetround and fesetround functions.
9339 Additional implementation-defined rounding directions, with macro definitions beginning
9340 with FE_ and an uppercase letter, may also be specified by the implementation. The
9341 defined macros expand to integer constant expressions whose values are distinct
9342 nonnegative values.<sup><a href="#note183"><b>183)</b></a></sup>
9351 represents the default floating-point environment -- the one installed at program startup
9353 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
9355 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
9357 Additional implementation-defined environments, with macro definitions beginning with
9358 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
9359 also be specified by the implementation.
9362 <p><small><a name="note178" href="#note178">178)</a> This header is designed to support the floating-point exception status flags and directed-rounding
9363 control modes required by IEC 60559, and other similar floating-point state information. Also it is
9364 designed to facilitate code portability among all systems.
9366 <p><small><a name="note179" href="#note179">179)</a> A floating-point status flag is not an object and can be set more than once within an expression.
9368 <p><small><a name="note180" href="#note180">180)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
9369 unaware of them). The responsibilities associated with accessing the floating-point environment fall
9370 on the programmer or program that does so explicitly.
9372 <p><small><a name="note181" href="#note181">181)</a> The implementation supports an exception if there are circumstances where a call to at least one of the
9373 functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not necessary for
9374 all the functions to succeed all the time.
9376 <p><small><a name="note182" href="#note182">182)</a> The macros should be distinct powers of two.
9378 <p><small><a name="note183" href="#note183">183)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
9379 FLT_ROUNDS, they are not required to do so.
9382 <h4><a name="7.6.1" href="#7.6.1">7.6.1 The FENV_ACCESS pragma</a></h4>
9386 #include <a href="#7.6"><fenv.h></a>
9387 #pragma STDC FENV_ACCESS on-off-switch</pre>
9388 <h6>Description</h6>
9390 The FENV_ACCESS pragma provides a means to inform the implementation when a
9391 program might access the floating-point environment to test floating-point status flags or
9392 run under non-default floating-point control modes.<sup><a href="#note184"><b>184)</b></a></sup> The pragma shall occur either
9393 outside external declarations or preceding all explicit declarations and statements inside a
9394 compound statement. When outside external declarations, the pragma takes effect from
9395 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
9396 the translation unit. When inside a compound statement, the pragma takes effect from its
9397 occurrence until another FENV_ACCESS pragma is encountered (including within a
9398 nested compound statement), or until the end of the compound statement; at the end of a
9399 compound statement the state for the pragma is restored to its condition just before the
9400 compound statement. If this pragma is used in any other context, the behavior is
9401 undefined. If part of a program tests floating-point status flags, sets floating-point control
9402 modes, or runs under non-default mode settings, but was translated with the state for the
9403 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
9404 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
9405 the program translated with FENV_ACCESS ''off'' to a part translated with
9406 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
9407 floating-point control modes have their default settings.)
9417 #include <a href="#7.6"><fenv.h></a>
9420 #pragma STDC FENV_ACCESS ON
9428 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
9429 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
9430 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note185"><b>185)</b></a></sup>
9434 <p><small><a name="note184" href="#note184">184)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
9435 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
9436 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
9437 modes are in effect and the flags are not tested.
9439 <p><small><a name="note185" href="#note185">185)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
9440 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
9441 ''off'', just one evaluation of x + 1 would suffice.
9444 <h4><a name="7.6.2" href="#7.6.2">7.6.2 Floating-point exceptions</a></h4>
9446 The following functions provide access to the floating-point status flags.<sup><a href="#note186"><b>186)</b></a></sup> The int
9447 input argument for the functions represents a subset of floating-point exceptions, and can
9448 be zero or the bitwise OR of one or more floating-point exception macros, for example
9449 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
9450 functions is undefined.
9453 <p><small><a name="note186" href="#note186">186)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
9454 abstraction of flags that are either set or clear. An implementation may endow floating-point status
9455 flags with more information -- for example, the address of the code which first raised the floating-
9456 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
9460 <h5><a name="7.6.2.1" href="#7.6.2.1">7.6.2.1 The feclearexcept function</a></h5>
9464 #include <a href="#7.6"><fenv.h></a>
9465 int feclearexcept(int excepts);</pre>
9466 <h6>Description</h6>
9468 The feclearexcept function attempts to clear the supported floating-point exceptions
9469 represented by its argument.
9472 The feclearexcept function returns zero if the excepts argument is zero or if all
9473 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
9478 <h5><a name="7.6.2.2" href="#7.6.2.2">7.6.2.2 The fegetexceptflag function</a></h5>
9482 #include <a href="#7.6"><fenv.h></a>
9483 int fegetexceptflag(fexcept_t *flagp,
9485 <h6>Description</h6>
9487 The fegetexceptflag function attempts to store an implementation-defined
9488 representation of the states of the floating-point status flags indicated by the argument
9489 excepts in the object pointed to by the argument flagp.
9492 The fegetexceptflag function returns zero if the representation was successfully
9493 stored. Otherwise, it returns a nonzero value.
9495 <h5><a name="7.6.2.3" href="#7.6.2.3">7.6.2.3 The feraiseexcept function</a></h5>
9499 #include <a href="#7.6"><fenv.h></a>
9500 int feraiseexcept(int excepts);</pre>
9501 <h6>Description</h6>
9503 The feraiseexcept function attempts to raise the supported floating-point exceptions
9504 represented by its argument.<sup><a href="#note187"><b>187)</b></a></sup> The order in which these floating-point exceptions are
9505 raised is unspecified, except as stated in <a href="#F.7.6">F.7.6</a>. Whether the feraiseexcept function
9506 additionally raises the ''inexact'' floating-point exception whenever it raises the
9507 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
9510 The feraiseexcept function returns zero if the excepts argument is zero or if all
9511 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
9519 <p><small><a name="note187" href="#note187">187)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
9520 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
9521 in <a href="#F.7.6">F.7.6</a> is in the same spirit.
9524 <h5><a name="7.6.2.4" href="#7.6.2.4">7.6.2.4 The fesetexceptflag function</a></h5>
9528 #include <a href="#7.6"><fenv.h></a>
9529 int fesetexceptflag(const fexcept_t *flagp,
9531 <h6>Description</h6>
9533 The fesetexceptflag function attempts to set the floating-point status flags
9534 indicated by the argument excepts to the states stored in the object pointed to by
9535 flagp. The value of *flagp shall have been set by a previous call to
9536 fegetexceptflag whose second argument represented at least those floating-point
9537 exceptions represented by the argument excepts. This function does not raise floating-
9538 point exceptions, but only sets the state of the flags.
9541 The fesetexceptflag function returns zero if the excepts argument is zero or if
9542 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
9545 <h5><a name="7.6.2.5" href="#7.6.2.5">7.6.2.5 The fetestexcept function</a></h5>
9549 #include <a href="#7.6"><fenv.h></a>
9550 int fetestexcept(int excepts);</pre>
9551 <h6>Description</h6>
9553 The fetestexcept function determines which of a specified subset of the floating-
9554 point exception flags are currently set. The excepts argument specifies the floating-
9555 point status flags to be queried.<sup><a href="#note188"><b>188)</b></a></sup>
9558 The fetestexcept function returns the value of the bitwise OR of the floating-point
9559 exception macros corresponding to the currently set floating-point exceptions included in
9562 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
9569 #include <a href="#7.6"><fenv.h></a>
9572 #pragma STDC FENV_ACCESS ON
9574 feclearexcept(FE_INVALID | FE_OVERFLOW);
9575 // maybe raise exceptions
9576 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
9577 if (set_excepts & FE_INVALID) f();
9578 if (set_excepts & FE_OVERFLOW) g();
9584 <p><small><a name="note188" href="#note188">188)</a> This mechanism allows testing several floating-point exceptions with just one function call.
9587 <h4><a name="7.6.3" href="#7.6.3">7.6.3 Rounding</a></h4>
9589 The fegetround and fesetround functions provide control of rounding direction
9592 <h5><a name="7.6.3.1" href="#7.6.3.1">7.6.3.1 The fegetround function</a></h5>
9596 #include <a href="#7.6"><fenv.h></a>
9597 int fegetround(void);</pre>
9598 <h6>Description</h6>
9600 The fegetround function gets the current rounding direction.
9603 The fegetround function returns the value of the rounding direction macro
9604 representing the current rounding direction or a negative value if there is no such
9605 rounding direction macro or the current rounding direction is not determinable.
9607 <h5><a name="7.6.3.2" href="#7.6.3.2">7.6.3.2 The fesetround function</a></h5>
9611 #include <a href="#7.6"><fenv.h></a>
9612 int fesetround(int round);</pre>
9613 <h6>Description</h6>
9615 The fesetround function establishes the rounding direction represented by its
9616 argument round. If the argument is not equal to the value of a rounding direction macro,
9617 the rounding direction is not changed.
9620 The fesetround function returns zero if and only if the requested rounding direction
9624 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
9625 rounding direction fails.
9627 #include <a href="#7.6"><fenv.h></a>
9628 #include <a href="#7.2"><assert.h></a>
9629 void f(int round_dir)
9631 #pragma STDC FENV_ACCESS ON
9634 save_round = fegetround();
9635 setround_ok = fesetround(round_dir);
9636 assert(setround_ok == 0);
9638 fesetround(save_round);
9643 <h4><a name="7.6.4" href="#7.6.4">7.6.4 Environment</a></h4>
9645 The functions in this section manage the floating-point environment -- status flags and
9646 control modes -- as one entity.
9648 <h5><a name="7.6.4.1" href="#7.6.4.1">7.6.4.1 The fegetenv function</a></h5>
9652 #include <a href="#7.6"><fenv.h></a>
9653 int fegetenv(fenv_t *envp);</pre>
9654 <h6>Description</h6>
9656 The fegetenv function attempts to store the current floating-point environment in the
9657 object pointed to by envp.
9660 The fegetenv function returns zero if the environment was successfully stored.
9661 Otherwise, it returns a nonzero value.
9663 <h5><a name="7.6.4.2" href="#7.6.4.2">7.6.4.2 The feholdexcept function</a></h5>
9667 #include <a href="#7.6"><fenv.h></a>
9668 int feholdexcept(fenv_t *envp);</pre>
9669 <h6>Description</h6>
9671 The feholdexcept function saves the current floating-point environment in the object
9672 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
9673 (continue on floating-point exceptions) mode, if available, for all floating-point
9674 exceptions.<sup><a href="#note189"><b>189)</b></a></sup>
9678 The feholdexcept function returns zero if and only if non-stop floating-point
9679 exception handling was successfully installed.
9682 <p><small><a name="note189" href="#note189">189)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
9683 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9684 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9685 function to write routines that hide spurious floating-point exceptions from their callers.
9688 <h5><a name="7.6.4.3" href="#7.6.4.3">7.6.4.3 The fesetenv function</a></h5>
9692 #include <a href="#7.6"><fenv.h></a>
9693 int fesetenv(const fenv_t *envp);</pre>
9694 <h6>Description</h6>
9696 The fesetenv function attempts to establish the floating-point environment represented
9697 by the object pointed to by envp. The argument envp shall point to an object set by a
9698 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
9699 Note that fesetenv merely installs the state of the floating-point status flags
9700 represented through its argument, and does not raise these floating-point exceptions.
9703 The fesetenv function returns zero if the environment was successfully established.
9704 Otherwise, it returns a nonzero value.
9706 <h5><a name="7.6.4.4" href="#7.6.4.4">7.6.4.4 The feupdateenv function</a></h5>
9710 #include <a href="#7.6"><fenv.h></a>
9711 int feupdateenv(const fenv_t *envp);</pre>
9712 <h6>Description</h6>
9714 The feupdateenv function attempts to save the currently raised floating-point
9715 exceptions in its automatic storage, install the floating-point environment represented by
9716 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9717 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9718 or equal a floating-point environment macro.
9721 The feupdateenv function returns zero if all the actions were successfully carried out.
9722 Otherwise, it returns a nonzero value.
9729 EXAMPLE Hide spurious underflow floating-point exceptions:
9732 #include <a href="#7.6"><fenv.h></a>
9735 #pragma STDC FENV_ACCESS ON
9738 if (feholdexcept(&save_env))
9739 return /* indication of an environmental problem */;
9741 if (/* test spurious underflow */)
9742 if (feclearexcept(FE_UNDERFLOW))
9743 return /* indication of an environmental problem */;
9744 if (feupdateenv(&save_env))
9745 return /* indication of an environmental problem */;
9749 <h3><a name="7.7" href="#7.7">7.7 Characteristics of floating types <float.h></a></h3>
9751 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9752 parameters of the standard floating-point types.
9754 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9755 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
9758 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
9760 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.18"><stdint.h></a> and extends it with
9761 additional facilities provided by hosted implementations.
9763 It declares functions for manipulating greatest-width integers and converting numeric
9764 character strings to greatest-width integers, and it declares the type
9767 which is a structure type that is the type of the value returned by the imaxdiv function.
9768 For each type declared in <a href="#7.18"><stdint.h></a>, it defines corresponding macros for conversion
9769 specifiers for use with the formatted input/output functions.<sup><a href="#note190"><b>190)</b></a></sup>
9770 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>), formatted input/output
9771 functions (<a href="#7.19.6">7.19.6</a>), formatted wide character input/output functions (<a href="#7.24.2">7.24.2</a>).
9774 <p><small><a name="note190" href="#note190">190)</a> See ''future library directions'' (<a href="#7.26.4">7.26.4</a>).
9777 <h4><a name="7.8.1" href="#7.8.1">7.8.1 Macros for format specifiers</a></h4>
9779 Each of the following object-like macros<sup><a href="#note191"><b>191)</b></a></sup> expands to a character string literal
9780 containing a conversion specifier, possibly modified by a length modifier, suitable for use
9781 within the format argument of a formatted input/output function when converting the
9782 corresponding integer type. These macro names have the general form of PRI (character
9783 string literals for the fprintf and fwprintf family) or SCN (character string literals
9784 for the fscanf and fwscanf family),<sup><a href="#note192"><b>192)</b></a></sup> followed by the conversion specifier,
9785 followed by a name corresponding to a similar type name in <a href="#7.18.1">7.18.1</a>. In these names, N
9786 represents the width of the type as described in <a href="#7.18.1">7.18.1</a>. For example, PRIdFAST32 can
9787 be used in a format string to print the value of an integer of type int_fast32_t.
9789 The fprintf macros for signed integers are:
9791 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9792 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR</pre>
9799 The fprintf macros for unsigned integers are:
9802 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9803 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9804 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9805 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR</pre>
9806 The fscanf macros for signed integers are:
9809 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9810 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR</pre>
9811 The fscanf macros for unsigned integers are:
9814 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9815 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9816 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR</pre>
9817 For each type that the implementation provides in <a href="#7.18"><stdint.h></a>, the corresponding
9818 fprintf macros shall be defined and the corresponding fscanf macros shall be
9819 defined unless the implementation does not have a suitable fscanf length modifier for
9824 #include <a href="#7.8"><inttypes.h></a>
9825 #include <a href="#7.24"><wchar.h></a>
9828 uintmax_t i = UINTMAX_MAX; // this type always exists
9829 wprintf(L"The largest integer value is %020"
9836 <p><small><a name="note191" href="#note191">191)</a> C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined
9837 before <a href="#7.8"><inttypes.h></a> is included.
9839 <p><small><a name="note192" href="#note192">192)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
9840 different format specifiers may be required for fprintf and fscanf, even when the type is the
9844 <h4><a name="7.8.2" href="#7.8.2">7.8.2 Functions for greatest-width integer types</a></h4>
9846 <h5><a name="7.8.2.1" href="#7.8.2.1">7.8.2.1 The imaxabs function</a></h5>
9850 #include <a href="#7.8"><inttypes.h></a>
9851 intmax_t imaxabs(intmax_t j);</pre>
9852 <h6>Description</h6>
9854 The imaxabs function computes the absolute value of an integer j. If the result cannot
9855 be represented, the behavior is undefined.<sup><a href="#note193"><b>193)</b></a></sup>
9862 The imaxabs function returns the absolute value.
9865 <p><small><a name="note193" href="#note193">193)</a> The absolute value of the most negative number cannot be represented in two's complement.
9868 <h5><a name="7.8.2.2" href="#7.8.2.2">7.8.2.2 The imaxdiv function</a></h5>
9872 #include <a href="#7.8"><inttypes.h></a>
9873 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);</pre>
9874 <h6>Description</h6>
9876 The imaxdiv function computes numer / denom and numer % denom in a single
9880 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9881 quotient and the remainder. The structure shall contain (in either order) the members
9882 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9883 either part of the result cannot be represented, the behavior is undefined.
9885 <h5><a name="7.8.2.3" href="#7.8.2.3">7.8.2.3 The strtoimax and strtoumax functions</a></h5>
9889 #include <a href="#7.8"><inttypes.h></a>
9890 intmax_t strtoimax(const char * restrict nptr,
9891 char ** restrict endptr, int base);
9892 uintmax_t strtoumax(const char * restrict nptr,
9893 char ** restrict endptr, int base);</pre>
9894 <h6>Description</h6>
9896 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9897 strtoul, and strtoull functions, except that the initial portion of the string is
9898 converted to intmax_t and uintmax_t representation, respectively.
9901 The strtoimax and strtoumax functions return the converted value, if any. If no
9902 conversion could be performed, zero is returned. If the correct value is outside the range
9903 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9904 (according to the return type and sign of the value, if any), and the value of the macro
9905 ERANGE is stored in errno.
9906 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
9907 (<a href="#7.20.1.4">7.20.1.4</a>).
9910 <h5><a name="7.8.2.4" href="#7.8.2.4">7.8.2.4 The wcstoimax and wcstoumax functions</a></h5>
9914 #include <a href="#7.17"><stddef.h></a> // for wchar_t
9915 #include <a href="#7.8"><inttypes.h></a>
9916 intmax_t wcstoimax(const wchar_t * restrict nptr,
9917 wchar_t ** restrict endptr, int base);
9918 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9919 wchar_t ** restrict endptr, int base);</pre>
9920 <h6>Description</h6>
9922 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9923 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9924 converted to intmax_t and uintmax_t representation, respectively.
9927 The wcstoimax function returns the converted value, if any. If no conversion could be
9928 performed, zero is returned. If the correct value is outside the range of representable
9929 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9930 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9932 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
9933 (<a href="#7.24.4.1.2">7.24.4.1.2</a>).
9936 <h3><a name="7.9" href="#7.9">7.9 Alternative spellings <iso646.h></a></h3>
9938 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9939 to the corresponding tokens (on the right):
9954 <h3><a name="7.10" href="#7.10">7.10 Sizes of integer types <limits.h></a></h3>
9956 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9957 parameters of the standard integer types.
9959 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9960 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
9963 <h3><a name="7.11" href="#7.11">7.11 Localization <locale.h></a></h3>
9965 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9970 which contains members related to the formatting of numeric values. The structure shall
9971 contain at least the following members, in any order. The semantics of the members and
9972 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
9973 the values specified in the comments.
9977 char *decimal_point; // "."
9978 char *thousands_sep; // ""
9979 char *grouping; // ""
9980 char *mon_decimal_point; // ""
9981 char *mon_thousands_sep; // ""
9982 char *mon_grouping; // ""
9983 char *positive_sign; // ""
9984 char *negative_sign; // ""
9985 char *currency_symbol; // ""
9986 char frac_digits; // CHAR_MAX
9987 char p_cs_precedes; // CHAR_MAX
9988 char n_cs_precedes; // CHAR_MAX
9989 char p_sep_by_space; // CHAR_MAX
9990 char n_sep_by_space; // CHAR_MAX
9991 char p_sign_posn; // CHAR_MAX
9992 char n_sign_posn; // CHAR_MAX
9993 char *int_curr_symbol; // ""
9994 char int_frac_digits; // CHAR_MAX
9995 char int_p_cs_precedes; // CHAR_MAX
9996 char int_n_cs_precedes; // CHAR_MAX
9997 char int_p_sep_by_space; // CHAR_MAX
9998 char int_n_sep_by_space; // CHAR_MAX
9999 char int_p_sign_posn; // CHAR_MAX
10000 char int_n_sign_posn; // CHAR_MAX</pre>
10001 The macros defined are NULL (described in <a href="#7.17">7.17</a>); and
10009 which expand to integer constant expressions with distinct values, suitable for use as the
10010 first argument to the setlocale function.<sup><a href="#note194"><b>194)</b></a></sup> Additional macro definitions, beginning
10011 with the characters LC_ and an uppercase letter,<sup><a href="#note195"><b>195)</b></a></sup> may also be specified by the
10015 <p><small><a name="note194" href="#note194">194)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
10017 <p><small><a name="note195" href="#note195">195)</a> See ''future library directions'' (<a href="#7.26.5">7.26.5</a>).
10020 <h4><a name="7.11.1" href="#7.11.1">7.11.1 Locale control</a></h4>
10022 <h5><a name="7.11.1.1" href="#7.11.1.1">7.11.1.1 The setlocale function</a></h5>
10026 #include <a href="#7.11"><locale.h></a>
10027 char *setlocale(int category, const char *locale);</pre>
10028 <h6>Description</h6>
10030 The setlocale function selects the appropriate portion of the program's locale as
10031 specified by the category and locale arguments. The setlocale function may be
10032 used to change or query the program's entire current locale or portions thereof. The value
10033 LC_ALL for category names the program's entire locale; the other values for
10034 category name only a portion of the program's locale. LC_COLLATE affects the
10035 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
10036 the character handling functions<sup><a href="#note196"><b>196)</b></a></sup> and the multibyte and wide character functions.
10037 LC_MONETARY affects the monetary formatting information returned by the
10038 localeconv function. LC_NUMERIC affects the decimal-point character for the
10039 formatted input/output functions and the string conversion functions, as well as the
10040 nonmonetary formatting information returned by the localeconv function. LC_TIME
10041 affects the behavior of the strftime and wcsftime functions.
10043 A value of "C" for locale specifies the minimal environment for C translation; a value
10044 of "" for locale specifies the locale-specific native environment. Other
10045 implementation-defined strings may be passed as the second argument to setlocale.
10049 At program startup, the equivalent of
10051 setlocale(LC_ALL, "C");</pre>
10054 The implementation shall behave as if no library function calls the setlocale function.
10057 If a pointer to a string is given for locale and the selection can be honored, the
10058 setlocale function returns a pointer to the string associated with the specified
10059 category for the new locale. If the selection cannot be honored, the setlocale
10060 function returns a null pointer and the program's locale is not changed.
10062 A null pointer for locale causes the setlocale function to return a pointer to the
10063 string associated with the category for the program's current locale; the program's
10064 locale is not changed.<sup><a href="#note197"><b>197)</b></a></sup>
10066 The pointer to string returned by the setlocale function is such that a subsequent call
10067 with that string value and its associated category will restore that part of the program's
10068 locale. The string pointed to shall not be modified by the program, but may be
10069 overwritten by a subsequent call to the setlocale function.
10070 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.19.6">7.19.6</a>), multibyte/wide
10071 character conversion functions (<a href="#7.20.7">7.20.7</a>), multibyte/wide string conversion functions
10072 (<a href="#7.20.8">7.20.8</a>), numeric conversion functions (<a href="#7.20.1">7.20.1</a>), the strcoll function (<a href="#7.21.4.3">7.21.4.3</a>), the
10073 strftime function (<a href="#7.23.3.5">7.23.3.5</a>), the strxfrm function (<a href="#7.21.4.5">7.21.4.5</a>).
10076 <p><small><a name="note196" href="#note196">196)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
10079 <p><small><a name="note197" href="#note197">197)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
10080 locale when category has the value LC_ALL.
10083 <h4><a name="7.11.2" href="#7.11.2">7.11.2 Numeric formatting convention inquiry</a></h4>
10085 <h5><a name="7.11.2.1" href="#7.11.2.1">7.11.2.1 The localeconv function</a></h5>
10089 #include <a href="#7.11"><locale.h></a>
10090 struct lconv *localeconv(void);</pre>
10091 <h6>Description</h6>
10093 The localeconv function sets the components of an object with type struct lconv
10094 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
10095 according to the rules of the current locale.
10097 The members of the structure with type char * are pointers to strings, any of which
10098 (except decimal_point) can point to "", to indicate that the value is not available in
10099 the current locale or is of zero length. Apart from grouping and mon_grouping, the
10102 strings shall start and end in the initial shift state. The members with type char are
10103 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
10104 available in the current locale. The members include the following:
10105 char *decimal_point
10107 The decimal-point character used to format nonmonetary quantities.</pre>
10108 char *thousands_sep
10110 The character used to separate groups of digits before the decimal-point
10111 character in formatted nonmonetary quantities.</pre>
10114 A string whose elements indicate the size of each group of digits in
10115 formatted nonmonetary quantities.</pre>
10116 char *mon_decimal_point
10118 The decimal-point used to format monetary quantities.</pre>
10119 char *mon_thousands_sep
10121 The separator for groups of digits before the decimal-point in formatted
10122 monetary quantities.</pre>
10125 A string whose elements indicate the size of each group of digits in
10126 formatted monetary quantities.</pre>
10127 char *positive_sign
10129 The string used to indicate a nonnegative-valued formatted monetary
10131 char *negative_sign
10133 The string used to indicate a negative-valued formatted monetary quantity.</pre>
10134 char *currency_symbol
10136 The local currency symbol applicable to the current locale.</pre>
10139 The number of fractional digits (those after the decimal-point) to be
10140 displayed in a locally formatted monetary quantity.</pre>
10143 Set to 1 or 0 if the currency_symbol respectively precedes or
10144 succeeds the value for a nonnegative locally formatted monetary quantity.</pre>
10148 Set to 1 or 0 if the currency_symbol respectively precedes or
10149 succeeds the value for a negative locally formatted monetary quantity.</pre>
10150 char p_sep_by_space
10152 Set to a value indicating the separation of the currency_symbol, the
10153 sign string, and the value for a nonnegative locally formatted monetary
10155 char n_sep_by_space
10157 Set to a value indicating the separation of the currency_symbol, the
10158 sign string, and the value for a negative locally formatted monetary
10162 Set to a value indicating the positioning of the positive_sign for a
10163 nonnegative locally formatted monetary quantity.</pre>
10166 Set to a value indicating the positioning of the negative_sign for a
10167 negative locally formatted monetary quantity.</pre>
10168 char *int_curr_symbol
10170 The international currency symbol applicable to the current locale. The
10171 first three characters contain the alphabetic international currency symbol
10172 in accordance with those specified in ISO 4217. The fourth character
10173 (immediately preceding the null character) is the character used to separate
10174 the international currency symbol from the monetary quantity.</pre>
10175 char int_frac_digits
10177 The number of fractional digits (those after the decimal-point) to be
10178 displayed in an internationally formatted monetary quantity.</pre>
10179 char int_p_cs_precedes
10181 Set to 1 or 0 if the int_curr_symbol respectively precedes or
10182 succeeds the value for a nonnegative internationally formatted monetary
10184 char int_n_cs_precedes
10186 Set to 1 or 0 if the int_curr_symbol respectively precedes or
10187 succeeds the value for a negative internationally formatted monetary
10189 char int_p_sep_by_space
10192 Set to a value indicating the separation of the int_curr_symbol, the
10193 sign string, and the value for a nonnegative internationally formatted
10194 monetary quantity.</pre>
10195 char int_n_sep_by_space
10197 Set to a value indicating the separation of the int_curr_symbol, the
10198 sign string, and the value for a negative internationally formatted monetary
10200 char int_p_sign_posn
10202 Set to a value indicating the positioning of the positive_sign for a
10203 nonnegative internationally formatted monetary quantity.</pre>
10204 char int_n_sign_posn
10207 Set to a value indicating the positioning of the negative_sign for a
10208 negative internationally formatted monetary quantity.</pre>
10209 The elements of grouping and mon_grouping are interpreted according to the
10211 CHAR_MAX No further grouping is to be performed.
10212 0 The previous element is to be repeatedly used for the remainder of the
10215 other The integer value is the number of digits that compose the current group.
10218 The next element is examined to determine the size of the next group of
10219 digits before the current group.</pre>
10220 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
10221 and int_n_sep_by_space are interpreted according to the following:
10222 0 No space separates the currency symbol and value.
10223 1 If the currency symbol and sign string are adjacent, a space separates them from the
10225 value; otherwise, a space separates the currency symbol from the value.</pre>
10226 2 If the currency symbol and sign string are adjacent, a space separates them;
10228 otherwise, a space separates the sign string from the value.</pre>
10229 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
10230 int_curr_symbol is used instead of a space.
10232 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
10233 int_n_sign_posn are interpreted according to the following:
10234 0 Parentheses surround the quantity and currency symbol.
10235 1 The sign string precedes the quantity and currency symbol.
10236 2 The sign string succeeds the quantity and currency symbol.
10237 3 The sign string immediately precedes the currency symbol.
10238 4 The sign string immediately succeeds the currency symbol.
10241 The implementation shall behave as if no library function calls the localeconv
10245 The localeconv function returns a pointer to the filled-in object. The structure
10246 pointed to by the return value shall not be modified by the program, but may be
10247 overwritten by a subsequent call to the localeconv function. In addition, calls to the
10248 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
10249 overwrite the contents of the structure.
10251 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
10252 monetary quantities.
10254 Local format International format</pre>
10256 Country Positive Negative Positive Negative
10258 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
10259 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
10260 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
10261 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
10263 For these four countries, the respective values for the monetary members of the structure returned by
10264 localeconv could be:
10266 Country1 Country2 Country3 Country4</pre>
10268 mon_decimal_point "," "" "," "."
10269 mon_thousands_sep "." "." "." ","
10270 mon_grouping "\3" "\3" "\3" "\3"
10271 positive_sign "" "" "" ""
10272 negative_sign "-" "-" "-" "C"
10273 currency_symbol "mk" "L." "\u0192" "SFrs."
10274 frac_digits 2 0 2 2
10275 p_cs_precedes 0 1 1 1
10276 n_cs_precedes 0 1 1 1
10277 p_sep_by_space 1 0 1 0
10278 n_sep_by_space 1 0 2 0
10279 p_sign_posn 1 1 1 1
10280 n_sign_posn 1 1 4 2
10281 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
10282 int_frac_digits 2 0 2 2
10283 int_p_cs_precedes 1 1 1 1
10284 int_n_cs_precedes 1 1 1 1
10285 int_p_sep_by_space 1 1 1 1
10286 int_n_sep_by_space 2 1 2 1
10287 int_p_sign_posn 1 1 1 1
10288 int_n_sign_posn 4 1 4 2
10291 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
10292 affect the formatted value.
10294 p_sep_by_space</pre>
10296 p_cs_precedes p_sign_posn 0 1 2
10299 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
10300 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
10301 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
10302 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
10303 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +</pre>
10307 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
10308 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
10309 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
10310 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
10311 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25</pre>
10313 <h3><a name="7.12" href="#7.12">7.12 Mathematics <math.h></a></h3>
10315 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
10316 several macros. Most synopses specify a family of functions consisting of a principal
10317 function with one or more double parameters, a double return value, or both; and
10318 other functions with the same name but with f and l suffixes, which are corresponding
10319 functions with float and long double parameters, return values, or both.<sup><a href="#note198"><b>198)</b></a></sup>
10320 Integer arithmetic functions and conversion functions are discussed later.
10326 are floating types at least as wide as float and double, respectively, and such that
10327 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
10328 float_t and double_t are float and double, respectively; if
10329 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
10330 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
10331 otherwise implementation-defined.<sup><a href="#note199"><b>199)</b></a></sup>
10336 expands to a positive double constant expression, not necessarily representable as a
10341 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note200"><b>200)</b></a></sup>
10346 expands to a constant expression of type float representing positive or unsigned
10347 infinity, if available; else to a positive constant of type float that overflows at
10352 translation time.<sup><a href="#note201"><b>201)</b></a></sup>
10357 is defined if and only if the implementation supports quiet NaNs for the float type. It
10358 expands to a constant expression of type float representing a quiet NaN.
10360 The number classification macros
10367 represent the mutually exclusive kinds of floating-point values. They expand to integer
10368 constant expressions with distinct values. Additional implementation-defined floating-
10369 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
10370 may also be specified by the implementation.
10375 is optionally defined. If defined, it indicates that the fma function generally executes
10376 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note202"><b>202)</b></a></sup> The
10381 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
10382 these macros expand to the integer constant 1.
10388 expand to integer constant expressions whose values are returned by ilogb(x) if x is
10389 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
10390 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
10398 MATH_ERREXCEPT</pre>
10399 expand to the integer constants 1 and 2, respectively; the macro
10401 math_errhandling</pre>
10402 expands to an expression that has type int and the value MATH_ERRNO,
10403 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
10404 constant for the duration of the program. It is unspecified whether
10405 math_errhandling is a macro or an identifier with external linkage. If a macro
10406 definition is suppressed or a program defines an identifier with the name
10407 math_errhandling, the behavior is undefined. If the expression
10408 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
10409 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
10410 <a href="#7.6"><fenv.h></a>.
10413 <p><small><a name="note198" href="#note198">198)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
10414 and return values in wider format than the synopsis prototype indicates.
10416 <p><small><a name="note199" href="#note199">199)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
10417 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
10418 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
10420 <p><small><a name="note200" href="#note200">200)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
10421 supports infinities.
10423 <p><small><a name="note201" href="#note201">201)</a> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
10425 <p><small><a name="note202" href="#note202">202)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
10426 directly with a hardware multiply-add instruction. Software implementations are expected to be
10427 substantially slower.
10430 <h4><a name="7.12.1" href="#7.12.1">7.12.1 Treatment of error conditions</a></h4>
10432 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
10433 values of its input arguments, except where stated otherwise. Each function shall execute
10434 as if it were a single operation without generating any externally visible exceptional
10437 For all functions, a domain error occurs if an input argument is outside the domain over
10438 which the mathematical function is defined. The description of each function lists any
10439 required domain errors; an implementation may define additional domain errors, provided
10440 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note203"><b>203)</b></a></sup> On a
10441 domain error, the function returns an implementation-defined value; if the integer
10442 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
10443 errno acquires the value EDOM; if the integer expression math_errhandling &
10444 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
10446 Similarly, a range error occurs if the mathematical result of the function cannot be
10447 represented in an object of the specified type, due to extreme magnitude.
10449 A floating result overflows if the magnitude of the mathematical result is finite but so
10450 large that the mathematical result cannot be represented without extraordinary roundoff
10451 error in an object of the specified type. If a floating result overflows and default rounding
10452 is in effect, or if the mathematical result is an exact infinity from finite arguments (for
10453 example log(0.0)), then the function returns the value of the macro HUGE_VAL,
10457 HUGE_VALF, or HUGE_VALL according to the return type, with the same sign as the
10458 correct value of the function; if the integer expression math_errhandling &
10459 MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if
10460 the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the
10461 ''divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
10462 infinity and the ''overflow'' floating-point exception is raised otherwise.
10464 The result underflows if the magnitude of the mathematical result is so small that the
10465 mathematical result cannot be represented, without extraordinary roundoff error, in an
10466 object of the specified type.<sup><a href="#note204"><b>204)</b></a></sup> If the result underflows, the function returns an
10467 implementation-defined value whose magnitude is no greater than the smallest
10468 normalized positive number in the specified type; if the integer expression
10469 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
10470 value ERANGE is implementation-defined; if the integer expression
10471 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
10472 floating-point exception is raised is implementation-defined.
10475 <p><small><a name="note203" href="#note203">203)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
10476 error if the mathematical domain of the function does not include the infinity.
10478 <p><small><a name="note204" href="#note204">204)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
10479 also ''flush-to-zero'' underflow.
10482 <h4><a name="7.12.2" href="#7.12.2">7.12.2 The FP_CONTRACT pragma</a></h4>
10486 #include <a href="#7.12"><math.h></a>
10487 #pragma STDC FP_CONTRACT on-off-switch</pre>
10488 <h6>Description</h6>
10490 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
10491 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
10492 either outside external declarations or preceding all explicit declarations and statements
10493 inside a compound statement. When outside external declarations, the pragma takes
10494 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
10495 the end of the translation unit. When inside a compound statement, the pragma takes
10496 effect from its occurrence until another FP_CONTRACT pragma is encountered
10497 (including within a nested compound statement), or until the end of the compound
10498 statement; at the end of a compound statement the state for the pragma is restored to its
10499 condition just before the compound statement. If this pragma is used in any other
10500 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
10501 implementation-defined.
10508 <h4><a name="7.12.3" href="#7.12.3">7.12.3 Classification macros</a></h4>
10510 In the synopses in this subclause, real-floating indicates that the argument shall be an
10511 expression of real floating type.
10513 <h5><a name="7.12.3.1" href="#7.12.3.1">7.12.3.1 The fpclassify macro</a></h5>
10517 #include <a href="#7.12"><math.h></a>
10518 int fpclassify(real-floating x);</pre>
10519 <h6>Description</h6>
10521 The fpclassify macro classifies its argument value as NaN, infinite, normal,
10522 subnormal, zero, or into another implementation-defined category. First, an argument
10523 represented in a format wider than its semantic type is converted to its semantic type.
10524 Then classification is based on the type of the argument.<sup><a href="#note205"><b>205)</b></a></sup>
10527 The fpclassify macro returns the value of the number classification macro
10528 appropriate to the value of its argument.
10530 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
10532 #define fpclassify(x) \
10533 ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \
10534 (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \
10535 __fpclassifyl(x))</pre>
10539 <p><small><a name="note205" href="#note205">205)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
10540 know the type that classification is based on. For example, a normal long double value might
10541 become subnormal when converted to double, and zero when converted to float.
10544 <h5><a name="7.12.3.2" href="#7.12.3.2">7.12.3.2 The isfinite macro</a></h5>
10548 #include <a href="#7.12"><math.h></a>
10549 int isfinite(real-floating x);</pre>
10550 <h6>Description</h6>
10552 The isfinite macro determines whether its argument has a finite value (zero,
10553 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
10554 format wider than its semantic type is converted to its semantic type. Then determination
10555 is based on the type of the argument.
10563 The isfinite macro returns a nonzero value if and only if its argument has a finite
10566 <h5><a name="7.12.3.3" href="#7.12.3.3">7.12.3.3 The isinf macro</a></h5>
10570 #include <a href="#7.12"><math.h></a>
10571 int isinf(real-floating x);</pre>
10572 <h6>Description</h6>
10574 The isinf macro determines whether its argument value is an infinity (positive or
10575 negative). First, an argument represented in a format wider than its semantic type is
10576 converted to its semantic type. Then determination is based on the type of the argument.
10579 The isinf macro returns a nonzero value if and only if its argument has an infinite
10582 <h5><a name="7.12.3.4" href="#7.12.3.4">7.12.3.4 The isnan macro</a></h5>
10586 #include <a href="#7.12"><math.h></a>
10587 int isnan(real-floating x);</pre>
10588 <h6>Description</h6>
10590 The isnan macro determines whether its argument value is a NaN. First, an argument
10591 represented in a format wider than its semantic type is converted to its semantic type.
10592 Then determination is based on the type of the argument.<sup><a href="#note206"><b>206)</b></a></sup>
10595 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
10598 <p><small><a name="note206" href="#note206">206)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
10599 NaNs in the evaluation type but not in the semantic type.
10602 <h5><a name="7.12.3.5" href="#7.12.3.5">7.12.3.5 The isnormal macro</a></h5>
10606 #include <a href="#7.12"><math.h></a>
10607 int isnormal(real-floating x);</pre>
10613 <h6>Description</h6>
10615 The isnormal macro determines whether its argument value is normal (neither zero,
10616 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
10617 semantic type is converted to its semantic type. Then determination is based on the type
10621 The isnormal macro returns a nonzero value if and only if its argument has a normal
10624 <h5><a name="7.12.3.6" href="#7.12.3.6">7.12.3.6 The signbit macro</a></h5>
10628 #include <a href="#7.12"><math.h></a>
10629 int signbit(real-floating x);</pre>
10630 <h6>Description</h6>
10632 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note207"><b>207)</b></a></sup>
10635 The signbit macro returns a nonzero value if and only if the sign of its argument value
10639 <p><small><a name="note207" href="#note207">207)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
10640 unsigned, it is treated as positive.
10643 <h4><a name="7.12.4" href="#7.12.4">7.12.4 Trigonometric functions</a></h4>
10645 <h5><a name="7.12.4.1" href="#7.12.4.1">7.12.4.1 The acos functions</a></h5>
10649 #include <a href="#7.12"><math.h></a>
10650 double acos(double x);
10651 float acosf(float x);
10652 long double acosl(long double x);</pre>
10653 <h6>Description</h6>
10655 The acos functions compute the principal value of the arc cosine of x. A domain error
10656 occurs for arguments not in the interval [-1, +1].
10659 The acos functions return arccos x in the interval [0, pi ] radians.
10666 <h5><a name="7.12.4.2" href="#7.12.4.2">7.12.4.2 The asin functions</a></h5>
10670 #include <a href="#7.12"><math.h></a>
10671 double asin(double x);
10672 float asinf(float x);
10673 long double asinl(long double x);</pre>
10674 <h6>Description</h6>
10676 The asin functions compute the principal value of the arc sine of x. A domain error
10677 occurs for arguments not in the interval [-1, +1].
10680 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
10682 <h5><a name="7.12.4.3" href="#7.12.4.3">7.12.4.3 The atan functions</a></h5>
10686 #include <a href="#7.12"><math.h></a>
10687 double atan(double x);
10688 float atanf(float x);
10689 long double atanl(long double x);</pre>
10690 <h6>Description</h6>
10692 The atan functions compute the principal value of the arc tangent of x.
10695 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
10697 <h5><a name="7.12.4.4" href="#7.12.4.4">7.12.4.4 The atan2 functions</a></h5>
10701 #include <a href="#7.12"><math.h></a>
10702 double atan2(double y, double x);
10703 float atan2f(float y, float x);
10704 long double atan2l(long double y, long double x);</pre>
10705 <h6>Description</h6>
10707 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
10708 arguments to determine the quadrant of the return value. A domain error may occur if
10709 both arguments are zero.
10712 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
10715 <h5><a name="7.12.4.5" href="#7.12.4.5">7.12.4.5 The cos functions</a></h5>
10719 #include <a href="#7.12"><math.h></a>
10720 double cos(double x);
10721 float cosf(float x);
10722 long double cosl(long double x);</pre>
10723 <h6>Description</h6>
10725 The cos functions compute the cosine of x (measured in radians).
10728 The cos functions return cos x.
10730 <h5><a name="7.12.4.6" href="#7.12.4.6">7.12.4.6 The sin functions</a></h5>
10734 #include <a href="#7.12"><math.h></a>
10735 double sin(double x);
10736 float sinf(float x);
10737 long double sinl(long double x);</pre>
10738 <h6>Description</h6>
10740 The sin functions compute the sine of x (measured in radians).
10743 The sin functions return sin x.
10745 <h5><a name="7.12.4.7" href="#7.12.4.7">7.12.4.7 The tan functions</a></h5>
10749 #include <a href="#7.12"><math.h></a>
10750 double tan(double x);
10751 float tanf(float x);
10752 long double tanl(long double x);</pre>
10753 <h6>Description</h6>
10755 The tan functions return the tangent of x (measured in radians).
10758 The tan functions return tan x.
10761 <h4><a name="7.12.5" href="#7.12.5">7.12.5 Hyperbolic functions</a></h4>
10763 <h5><a name="7.12.5.1" href="#7.12.5.1">7.12.5.1 The acosh functions</a></h5>
10767 #include <a href="#7.12"><math.h></a>
10768 double acosh(double x);
10769 float acoshf(float x);
10770 long double acoshl(long double x);</pre>
10771 <h6>Description</h6>
10773 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
10774 error occurs for arguments less than 1.
10777 The acosh functions return arcosh x in the interval [0, +(inf)].
10779 <h5><a name="7.12.5.2" href="#7.12.5.2">7.12.5.2 The asinh functions</a></h5>
10783 #include <a href="#7.12"><math.h></a>
10784 double asinh(double x);
10785 float asinhf(float x);
10786 long double asinhl(long double x);</pre>
10787 <h6>Description</h6>
10789 The asinh functions compute the arc hyperbolic sine of x.
10792 The asinh functions return arsinh x.
10794 <h5><a name="7.12.5.3" href="#7.12.5.3">7.12.5.3 The atanh functions</a></h5>
10798 #include <a href="#7.12"><math.h></a>
10799 double atanh(double x);
10800 float atanhf(float x);
10801 long double atanhl(long double x);</pre>
10802 <h6>Description</h6>
10804 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
10805 for arguments not in the interval [-1, +1]. A range error may occur if the argument
10810 The atanh functions return artanh x.
10812 <h5><a name="7.12.5.4" href="#7.12.5.4">7.12.5.4 The cosh functions</a></h5>
10816 #include <a href="#7.12"><math.h></a>
10817 double cosh(double x);
10818 float coshf(float x);
10819 long double coshl(long double x);</pre>
10820 <h6>Description</h6>
10822 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
10823 magnitude of x is too large.
10826 The cosh functions return cosh x.
10828 <h5><a name="7.12.5.5" href="#7.12.5.5">7.12.5.5 The sinh functions</a></h5>
10832 #include <a href="#7.12"><math.h></a>
10833 double sinh(double x);
10834 float sinhf(float x);
10835 long double sinhl(long double x);</pre>
10836 <h6>Description</h6>
10838 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
10839 magnitude of x is too large.
10842 The sinh functions return sinh x.
10844 <h5><a name="7.12.5.6" href="#7.12.5.6">7.12.5.6 The tanh functions</a></h5>
10848 #include <a href="#7.12"><math.h></a>
10849 double tanh(double x);
10850 float tanhf(float x);
10851 long double tanhl(long double x);</pre>
10852 <h6>Description</h6>
10854 The tanh functions compute the hyperbolic tangent of x.
10858 The tanh functions return tanh x.
10860 <h4><a name="7.12.6" href="#7.12.6">7.12.6 Exponential and logarithmic functions</a></h4>
10862 <h5><a name="7.12.6.1" href="#7.12.6.1">7.12.6.1 The exp functions</a></h5>
10866 #include <a href="#7.12"><math.h></a>
10867 double exp(double x);
10868 float expf(float x);
10869 long double expl(long double x);</pre>
10870 <h6>Description</h6>
10872 The exp functions compute the base-e exponential of x. A range error occurs if the
10873 magnitude of x is too large.
10876 The exp functions return ex .
10878 <h5><a name="7.12.6.2" href="#7.12.6.2">7.12.6.2 The exp2 functions</a></h5>
10882 #include <a href="#7.12"><math.h></a>
10883 double exp2(double x);
10884 float exp2f(float x);
10885 long double exp2l(long double x);</pre>
10886 <h6>Description</h6>
10888 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
10889 magnitude of x is too large.
10892 The exp2 functions return 2x .
10894 <h5><a name="7.12.6.3" href="#7.12.6.3">7.12.6.3 The expm1 functions</a></h5>
10899 #include <a href="#7.12"><math.h></a>
10900 double expm1(double x);
10901 float expm1f(float x);
10902 long double expm1l(long double x);</pre>
10903 <h6>Description</h6>
10905 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10906 error occurs if x is too large.<sup><a href="#note208"><b>208)</b></a></sup>
10909 The expm1 functions return ex - 1.
10912 <p><small><a name="note208" href="#note208">208)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
10915 <h5><a name="7.12.6.4" href="#7.12.6.4">7.12.6.4 The frexp functions</a></h5>
10919 #include <a href="#7.12"><math.h></a>
10920 double frexp(double value, int *exp);
10921 float frexpf(float value, int *exp);
10922 long double frexpl(long double value, int *exp);</pre>
10923 <h6>Description</h6>
10925 The frexp functions break a floating-point number into a normalized fraction and an
10926 integral power of 2. They store the integer in the int object pointed to by exp.
10929 If value is not a floating-point number, the results are unspecified. Otherwise, the
10930 frexp functions return the value x, such that x has a magnitude in the interval [1/2, 1) or
10931 zero, and value equals x x 2*exp . If value is zero, both parts of the result are zero.
10933 <h5><a name="7.12.6.5" href="#7.12.6.5">7.12.6.5 The ilogb functions</a></h5>
10937 #include <a href="#7.12"><math.h></a>
10938 int ilogb(double x);
10939 int ilogbf(float x);
10940 int ilogbl(long double x);</pre>
10941 <h6>Description</h6>
10943 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10944 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10945 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10946 the corresponding logb function and casting the returned value to type int. A domain
10947 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10948 the range of the return type, the numeric result is unspecified.
10956 The ilogb functions return the exponent of x as a signed int value.
10957 <p><b> Forward references</b>: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
10959 <h5><a name="7.12.6.6" href="#7.12.6.6">7.12.6.6 The ldexp functions</a></h5>
10963 #include <a href="#7.12"><math.h></a>
10964 double ldexp(double x, int exp);
10965 float ldexpf(float x, int exp);
10966 long double ldexpl(long double x, int exp);</pre>
10967 <h6>Description</h6>
10969 The ldexp functions multiply a floating-point number by an integral power of 2. A
10970 range error may occur.
10973 The ldexp functions return x x 2exp .
10975 <h5><a name="7.12.6.7" href="#7.12.6.7">7.12.6.7 The log functions</a></h5>
10979 #include <a href="#7.12"><math.h></a>
10980 double log(double x);
10981 float logf(float x);
10982 long double logl(long double x);</pre>
10983 <h6>Description</h6>
10985 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10986 the argument is negative. A range error may occur if the argument is zero.
10989 The log functions return loge x.
10991 <h5><a name="7.12.6.8" href="#7.12.6.8">7.12.6.8 The log10 functions</a></h5>
10996 #include <a href="#7.12"><math.h></a>
10997 double log10(double x);
10998 float log10f(float x);
10999 long double log10l(long double x);</pre>
11000 <h6>Description</h6>
11002 The log10 functions compute the base-10 (common) logarithm of x. A domain error
11003 occurs if the argument is negative. A range error may occur if the argument is zero.
11006 The log10 functions return log10 x.
11008 <h5><a name="7.12.6.9" href="#7.12.6.9">7.12.6.9 The log1p functions</a></h5>
11012 #include <a href="#7.12"><math.h></a>
11013 double log1p(double x);
11014 float log1pf(float x);
11015 long double log1pl(long double x);</pre>
11016 <h6>Description</h6>
11018 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note209"><b>209)</b></a></sup>
11019 A domain error occurs if the argument is less than -1. A range error may occur if the
11020 argument equals -1.
11023 The log1p functions return loge (1 + x).
11026 <p><small><a name="note209" href="#note209">209)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
11029 <h5><a name="7.12.6.10" href="#7.12.6.10">7.12.6.10 The log2 functions</a></h5>
11033 #include <a href="#7.12"><math.h></a>
11034 double log2(double x);
11035 float log2f(float x);
11036 long double log2l(long double x);</pre>
11037 <h6>Description</h6>
11039 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
11040 argument is less than zero. A range error may occur if the argument is zero.
11043 The log2 functions return log2 x.
11050 <h5><a name="7.12.6.11" href="#7.12.6.11">7.12.6.11 The logb functions</a></h5>
11054 #include <a href="#7.12"><math.h></a>
11055 double logb(double x);
11056 float logbf(float x);
11057 long double logbl(long double x);</pre>
11058 <h6>Description</h6>
11060 The logb functions extract the exponent of x, as a signed integer value in floating-point
11061 format. If x is subnormal it is treated as though it were normalized; thus, for positive
11064 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX</pre>
11065 A domain error or range error may occur if the argument is zero.
11068 The logb functions return the signed exponent of x.
11070 <h5><a name="7.12.6.12" href="#7.12.6.12">7.12.6.12 The modf functions</a></h5>
11074 #include <a href="#7.12"><math.h></a>
11075 double modf(double value, double *iptr);
11076 float modff(float value, float *iptr);
11077 long double modfl(long double value, long double *iptr);</pre>
11078 <h6>Description</h6>
11080 The modf functions break the argument value into integral and fractional parts, each of
11081 which has the same type and sign as the argument. They store the integral part (in
11082 floating-point format) in the object pointed to by iptr.
11085 The modf functions return the signed fractional part of value.
11088 <h5><a name="7.12.6.13" href="#7.12.6.13">7.12.6.13 The scalbn and scalbln functions</a></h5>
11092 #include <a href="#7.12"><math.h></a>
11093 double scalbn(double x, int n);
11094 float scalbnf(float x, int n);
11095 long double scalbnl(long double x, int n);
11096 double scalbln(double x, long int n);
11097 float scalblnf(float x, long int n);
11098 long double scalblnl(long double x, long int n);</pre>
11099 <h6>Description</h6>
11101 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
11102 normally by computing FLT_RADIXn explicitly. A range error may occur.
11105 The scalbn and scalbln functions return x x FLT_RADIXn .
11107 <h4><a name="7.12.7" href="#7.12.7">7.12.7 Power and absolute-value functions</a></h4>
11109 <h5><a name="7.12.7.1" href="#7.12.7.1">7.12.7.1 The cbrt functions</a></h5>
11113 #include <a href="#7.12"><math.h></a>
11114 double cbrt(double x);
11115 float cbrtf(float x);
11116 long double cbrtl(long double x);</pre>
11117 <h6>Description</h6>
11119 The cbrt functions compute the real cube root of x.
11122 The cbrt functions return x1/3 .
11124 <h5><a name="7.12.7.2" href="#7.12.7.2">7.12.7.2 The fabs functions</a></h5>
11128 #include <a href="#7.12"><math.h></a>
11129 double fabs(double x);
11130 float fabsf(float x);
11131 long double fabsl(long double x);</pre>
11132 <h6>Description</h6>
11134 The fabs functions compute the absolute value of a floating-point number x.
11138 The fabs functions return | x |.
11140 <h5><a name="7.12.7.3" href="#7.12.7.3">7.12.7.3 The hypot functions</a></h5>
11144 #include <a href="#7.12"><math.h></a>
11145 double hypot(double x, double y);
11146 float hypotf(float x, float y);
11147 long double hypotl(long double x, long double y);</pre>
11148 <h6>Description</h6>
11150 The hypot functions compute the square root of the sum of the squares of x and y,
11151 without undue overflow or underflow. A range error may occur.
11155 The hypot functions return (sqrt)x2 + y2 .
11158 ???????????????</pre>
11160 <h5><a name="7.12.7.4" href="#7.12.7.4">7.12.7.4 The pow functions</a></h5>
11164 #include <a href="#7.12"><math.h></a>
11165 double pow(double x, double y);
11166 float powf(float x, float y);
11167 long double powl(long double x, long double y);</pre>
11168 <h6>Description</h6>
11170 The pow functions compute x raised to the power y. A domain error occurs if x is finite
11171 and negative and y is finite and not an integer value. A range error may occur. A domain
11172 error may occur if x is zero and y is zero. A domain error or range error may occur if x
11173 is zero and y is less than zero.
11176 The pow functions return xy .
11178 <h5><a name="7.12.7.5" href="#7.12.7.5">7.12.7.5 The sqrt functions</a></h5>
11183 #include <a href="#7.12"><math.h></a>
11184 double sqrt(double x);
11185 float sqrtf(float x);
11186 long double sqrtl(long double x);</pre>
11187 <h6>Description</h6>
11189 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
11190 the argument is less than zero.
11193 The sqrt functions return (sqrt)x.
11198 <h4><a name="7.12.8" href="#7.12.8">7.12.8 Error and gamma functions</a></h4>
11200 <h5><a name="7.12.8.1" href="#7.12.8.1">7.12.8.1 The erf functions</a></h5>
11204 #include <a href="#7.12"><math.h></a>
11205 double erf(double x);
11206 float erff(float x);
11207 long double erfl(long double x);</pre>
11208 <h6>Description</h6>
11210 The erf functions compute the error function of x.
11216 The erf functions return erf x = e-t dt.
11227 <h5><a name="7.12.8.2" href="#7.12.8.2">7.12.8.2 The erfc functions</a></h5>
11231 #include <a href="#7.12"><math.h></a>
11232 double erfc(double x);
11233 float erfcf(float x);
11234 long double erfcl(long double x);</pre>
11235 <h6>Description</h6>
11237 The erfc functions compute the complementary error function of x. A range error
11238 occurs if x is too large.
11244 The erfc functions return erfc x = 1 - erf x = e-t dt.
11255 <h5><a name="7.12.8.3" href="#7.12.8.3">7.12.8.3 The lgamma functions</a></h5>
11259 #include <a href="#7.12"><math.h></a>
11260 double lgamma(double x);
11261 float lgammaf(float x);
11262 long double lgammal(long double x);</pre>
11263 <h6>Description</h6>
11265 The lgamma functions compute the natural logarithm of the absolute value of gamma of
11266 x. A range error occurs if x is too large. A range error may occur if x is a negative
11270 The lgamma functions return loge | (Gamma)(x) |.
11272 <h5><a name="7.12.8.4" href="#7.12.8.4">7.12.8.4 The tgamma functions</a></h5>
11276 #include <a href="#7.12"><math.h></a>
11277 double tgamma(double x);
11278 float tgammaf(float x);
11279 long double tgammal(long double x);</pre>
11280 <h6>Description</h6>
11282 The tgamma functions compute the gamma function of x. A domain error or range error
11283 may occur if x is a negative integer or zero. A range error may occur if the magnitude of
11284 x is too large or too small.
11287 The tgamma functions return (Gamma)(x).
11289 <h4><a name="7.12.9" href="#7.12.9">7.12.9 Nearest integer functions</a></h4>
11291 <h5><a name="7.12.9.1" href="#7.12.9.1">7.12.9.1 The ceil functions</a></h5>
11295 #include <a href="#7.12"><math.h></a>
11296 double ceil(double x);
11297 float ceilf(float x);
11298 long double ceill(long double x);</pre>
11299 <h6>Description</h6>
11301 The ceil functions compute the smallest integer value not less than x.
11305 The ceil functions return ???x???, expressed as a floating-point number.
11307 <h5><a name="7.12.9.2" href="#7.12.9.2">7.12.9.2 The floor functions</a></h5>
11311 #include <a href="#7.12"><math.h></a>
11312 double floor(double x);
11313 float floorf(float x);
11314 long double floorl(long double x);</pre>
11315 <h6>Description</h6>
11317 The floor functions compute the largest integer value not greater than x.
11320 The floor functions return ???x???, expressed as a floating-point number.
11322 <h5><a name="7.12.9.3" href="#7.12.9.3">7.12.9.3 The nearbyint functions</a></h5>
11326 #include <a href="#7.12"><math.h></a>
11327 double nearbyint(double x);
11328 float nearbyintf(float x);
11329 long double nearbyintl(long double x);</pre>
11330 <h6>Description</h6>
11332 The nearbyint functions round their argument to an integer value in floating-point
11333 format, using the current rounding direction and without raising the ''inexact'' floating-
11337 The nearbyint functions return the rounded integer value.
11339 <h5><a name="7.12.9.4" href="#7.12.9.4">7.12.9.4 The rint functions</a></h5>
11343 #include <a href="#7.12"><math.h></a>
11344 double rint(double x);
11345 float rintf(float x);
11346 long double rintl(long double x);</pre>
11347 <h6>Description</h6>
11349 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
11350 rint functions may raise the ''inexact'' floating-point exception if the result differs in
11351 value from the argument.
11355 The rint functions return the rounded integer value.
11357 <h5><a name="7.12.9.5" href="#7.12.9.5">7.12.9.5 The lrint and llrint functions</a></h5>
11361 #include <a href="#7.12"><math.h></a>
11362 long int lrint(double x);
11363 long int lrintf(float x);
11364 long int lrintl(long double x);
11365 long long int llrint(double x);
11366 long long int llrintf(float x);
11367 long long int llrintl(long double x);</pre>
11368 <h6>Description</h6>
11370 The lrint and llrint functions round their argument to the nearest integer value,
11371 rounding according to the current rounding direction. If the rounded value is outside the
11372 range of the return type, the numeric result is unspecified and a domain error or range
11376 The lrint and llrint functions return the rounded integer value.
11378 <h5><a name="7.12.9.6" href="#7.12.9.6">7.12.9.6 The round functions</a></h5>
11382 #include <a href="#7.12"><math.h></a>
11383 double round(double x);
11384 float roundf(float x);
11385 long double roundl(long double x);</pre>
11386 <h6>Description</h6>
11388 The round functions round their argument to the nearest integer value in floating-point
11389 format, rounding halfway cases away from zero, regardless of the current rounding
11393 The round functions return the rounded integer value.
11396 <h5><a name="7.12.9.7" href="#7.12.9.7">7.12.9.7 The lround and llround functions</a></h5>
11400 #include <a href="#7.12"><math.h></a>
11401 long int lround(double x);
11402 long int lroundf(float x);
11403 long int lroundl(long double x);
11404 long long int llround(double x);
11405 long long int llroundf(float x);
11406 long long int llroundl(long double x);</pre>
11407 <h6>Description</h6>
11409 The lround and llround functions round their argument to the nearest integer value,
11410 rounding halfway cases away from zero, regardless of the current rounding direction. If
11411 the rounded value is outside the range of the return type, the numeric result is unspecified
11412 and a domain error or range error may occur.
11415 The lround and llround functions return the rounded integer value.
11417 <h5><a name="7.12.9.8" href="#7.12.9.8">7.12.9.8 The trunc functions</a></h5>
11421 #include <a href="#7.12"><math.h></a>
11422 double trunc(double x);
11423 float truncf(float x);
11424 long double truncl(long double x);</pre>
11425 <h6>Description</h6>
11427 The trunc functions round their argument to the integer value, in floating format,
11428 nearest to but no larger in magnitude than the argument.
11431 The trunc functions return the truncated integer value.
11434 <h4><a name="7.12.10" href="#7.12.10">7.12.10 Remainder functions</a></h4>
11436 <h5><a name="7.12.10.1" href="#7.12.10.1">7.12.10.1 The fmod functions</a></h5>
11440 #include <a href="#7.12"><math.h></a>
11441 double fmod(double x, double y);
11442 float fmodf(float x, float y);
11443 long double fmodl(long double x, long double y);</pre>
11444 <h6>Description</h6>
11446 The fmod functions compute the floating-point remainder of x/y.
11449 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
11450 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
11451 whether a domain error occurs or the fmod functions return zero is implementation-
11454 <h5><a name="7.12.10.2" href="#7.12.10.2">7.12.10.2 The remainder functions</a></h5>
11458 #include <a href="#7.12"><math.h></a>
11459 double remainder(double x, double y);
11460 float remainderf(float x, float y);
11461 long double remainderl(long double x, long double y);</pre>
11462 <h6>Description</h6>
11464 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note210"><b>210)</b></a></sup>
11467 The remainder functions return x REM y. If y is zero, whether a domain error occurs
11468 or the functions return zero is implementation defined.
11476 <p><small><a name="note210" href="#note210">210)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
11477 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
11478 | n - x/y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
11479 x.'' This definition is applicable for all implementations.
11482 <h5><a name="7.12.10.3" href="#7.12.10.3">7.12.10.3 The remquo functions</a></h5>
11486 #include <a href="#7.12"><math.h></a>
11487 double remquo(double x, double y, int *quo);
11488 float remquof(float x, float y, int *quo);
11489 long double remquol(long double x, long double y,
11491 <h6>Description</h6>
11493 The remquo functions compute the same remainder as the remainder functions. In
11494 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
11495 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
11496 n is an implementation-defined integer greater than or equal to 3.
11499 The remquo functions return x REM y. If y is zero, the value stored in the object
11500 pointed to by quo is unspecified and whether a domain error occurs or the functions
11501 return zero is implementation defined.
11503 <h4><a name="7.12.11" href="#7.12.11">7.12.11 Manipulation functions</a></h4>
11505 <h5><a name="7.12.11.1" href="#7.12.11.1">7.12.11.1 The copysign functions</a></h5>
11509 #include <a href="#7.12"><math.h></a>
11510 double copysign(double x, double y);
11511 float copysignf(float x, float y);
11512 long double copysignl(long double x, long double y);</pre>
11513 <h6>Description</h6>
11515 The copysign functions produce a value with the magnitude of x and the sign of y.
11516 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
11517 represent a signed zero but do not treat negative zero consistently in arithmetic
11518 operations, the copysign functions regard the sign of zero as positive.
11521 The copysign functions return a value with the magnitude of x and the sign of y.
11524 <h5><a name="7.12.11.2" href="#7.12.11.2">7.12.11.2 The nan functions</a></h5>
11528 #include <a href="#7.12"><math.h></a>
11529 double nan(const char *tagp);
11530 float nanf(const char *tagp);
11531 long double nanl(const char *tagp);</pre>
11532 <h6>Description</h6>
11534 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
11535 sequence)", (char**) NULL); the call nan("") is equivalent to
11536 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
11537 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
11538 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
11542 The nan functions return a quiet NaN, if available, with content indicated through tagp.
11543 If the implementation does not support quiet NaNs, the functions return zero.
11544 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
11546 <h5><a name="7.12.11.3" href="#7.12.11.3">7.12.11.3 The nextafter functions</a></h5>
11550 #include <a href="#7.12"><math.h></a>
11551 double nextafter(double x, double y);
11552 float nextafterf(float x, float y);
11553 long double nextafterl(long double x, long double y);</pre>
11554 <h6>Description</h6>
11556 The nextafter functions determine the next representable value, in the type of the
11557 function, after x in the direction of y, where x and y are first converted to the type of the
11558 function.<sup><a href="#note211"><b>211)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
11559 if the magnitude of x is the largest finite value representable in the type and the result is
11560 infinite or not representable in the type.
11563 The nextafter functions return the next representable value in the specified format
11564 after x in the direction of y.
11570 <p><small><a name="note211" href="#note211">211)</a> The argument values are converted to the type of the function, even by a macro implementation of the
11574 <h5><a name="7.12.11.4" href="#7.12.11.4">7.12.11.4 The nexttoward functions</a></h5>
11578 #include <a href="#7.12"><math.h></a>
11579 double nexttoward(double x, long double y);
11580 float nexttowardf(float x, long double y);
11581 long double nexttowardl(long double x, long double y);</pre>
11582 <h6>Description</h6>
11584 The nexttoward functions are equivalent to the nextafter functions except that the
11585 second parameter has type long double and the functions return y converted to the
11586 type of the function if x equals y.<sup><a href="#note212"><b>212)</b></a></sup>
11589 <p><small><a name="note212" href="#note212">212)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
11590 range or precision in a floating second argument.
11593 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
11595 <h5><a name="7.12.12.1" href="#7.12.12.1">7.12.12.1 The fdim functions</a></h5>
11599 #include <a href="#7.12"><math.h></a>
11600 double fdim(double x, double y);
11601 float fdimf(float x, float y);
11602 long double fdiml(long double x, long double y);</pre>
11603 <h6>Description</h6>
11605 The fdim functions determine the positive difference between their arguments:
11607 ???x - y if x > y
11609 ???+0 if x <= y</pre>
11610 A range error may occur.
11613 The fdim functions return the positive difference value.
11615 <h5><a name="7.12.12.2" href="#7.12.12.2">7.12.12.2 The fmax functions</a></h5>
11619 #include <a href="#7.12"><math.h></a>
11620 double fmax(double x, double y);
11621 float fmaxf(float x, float y);
11622 long double fmaxl(long double x, long double y);</pre>
11627 <h6>Description</h6>
11629 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note213"><b>213)</b></a></sup>
11632 The fmax functions return the maximum numeric value of their arguments.
11635 <p><small><a name="note213" href="#note213">213)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
11636 fmax functions choose the numeric value. See <a href="#F.9.9.2">F.9.9.2</a>.
11639 <h5><a name="7.12.12.3" href="#7.12.12.3">7.12.12.3 The fmin functions</a></h5>
11643 #include <a href="#7.12"><math.h></a>
11644 double fmin(double x, double y);
11645 float fminf(float x, float y);
11646 long double fminl(long double x, long double y);</pre>
11647 <h6>Description</h6>
11649 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note214"><b>214)</b></a></sup>
11652 The fmin functions return the minimum numeric value of their arguments.
11655 <p><small><a name="note214" href="#note214">214)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
11658 <h4><a name="7.12.13" href="#7.12.13">7.12.13 Floating multiply-add</a></h4>
11660 <h5><a name="7.12.13.1" href="#7.12.13.1">7.12.13.1 The fma functions</a></h5>
11664 #include <a href="#7.12"><math.h></a>
11665 double fma(double x, double y, double z);
11666 float fmaf(float x, float y, float z);
11667 long double fmal(long double x, long double y,
11668 long double z);</pre>
11669 <h6>Description</h6>
11671 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
11672 the value (as if) to infinite precision and round once to the result format, according to the
11673 current rounding mode. A range error may occur.
11676 The fma functions return (x x y) + z, rounded as one ternary operation.
11683 <h4><a name="7.12.14" href="#7.12.14">7.12.14 Comparison macros</a></h4>
11685 The relational and equality operators support the usual mathematical relationships
11686 between numeric values. For any ordered pair of numeric values exactly one of the
11687 relationships -- less, greater, and equal -- is true. Relational operators may raise the
11688 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
11689 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note215"><b>215)</b></a></sup> The following
11690 subclauses provide macros that are quiet (non floating-point exception raising) versions
11691 of the relational operators, and other comparison macros that facilitate writing efficient
11692 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
11693 the synopses in this subclause, real-floating indicates that the argument shall be an
11694 expression of real floating type.
11697 <p><small><a name="note215" href="#note215">215)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
11698 the operands compare unordered, as an error indicator for programs written without consideration of
11699 NaNs; the result in these cases is false.
11702 <h5><a name="7.12.14.1" href="#7.12.14.1">7.12.14.1 The isgreater macro</a></h5>
11706 #include <a href="#7.12"><math.h></a>
11707 int isgreater(real-floating x, real-floating y);</pre>
11708 <h6>Description</h6>
11710 The isgreater macro determines whether its first argument is greater than its second
11711 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
11712 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
11713 exception when x and y are unordered.
11716 The isgreater macro returns the value of (x) > (y).
11718 <h5><a name="7.12.14.2" href="#7.12.14.2">7.12.14.2 The isgreaterequal macro</a></h5>
11722 #include <a href="#7.12"><math.h></a>
11723 int isgreaterequal(real-floating x, real-floating y);</pre>
11724 <h6>Description</h6>
11726 The isgreaterequal macro determines whether its first argument is greater than or
11727 equal to its second argument. The value of isgreaterequal(x, y) is always equal
11728 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
11729 not raise the ''invalid'' floating-point exception when x and y are unordered.
11736 The isgreaterequal macro returns the value of (x) >= (y).
11738 <h5><a name="7.12.14.3" href="#7.12.14.3">7.12.14.3 The isless macro</a></h5>
11742 #include <a href="#7.12"><math.h></a>
11743 int isless(real-floating x, real-floating y);</pre>
11744 <h6>Description</h6>
11746 The isless macro determines whether its first argument is less than its second
11747 argument. The value of isless(x, y) is always equal to (x) < (y); however,
11748 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
11749 exception when x and y are unordered.
11752 The isless macro returns the value of (x) < (y).
11754 <h5><a name="7.12.14.4" href="#7.12.14.4">7.12.14.4 The islessequal macro</a></h5>
11758 #include <a href="#7.12"><math.h></a>
11759 int islessequal(real-floating x, real-floating y);</pre>
11760 <h6>Description</h6>
11762 The islessequal macro determines whether its first argument is less than or equal to
11763 its second argument. The value of islessequal(x, y) is always equal to
11764 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
11765 the ''invalid'' floating-point exception when x and y are unordered.
11768 The islessequal macro returns the value of (x) <= (y).
11770 <h5><a name="7.12.14.5" href="#7.12.14.5">7.12.14.5 The islessgreater macro</a></h5>
11774 #include <a href="#7.12"><math.h></a>
11775 int islessgreater(real-floating x, real-floating y);</pre>
11776 <h6>Description</h6>
11778 The islessgreater macro determines whether its first argument is less than or
11779 greater than its second argument. The islessgreater(x, y) macro is similar to
11780 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
11781 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
11786 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
11788 <h5><a name="7.12.14.6" href="#7.12.14.6">7.12.14.6 The isunordered macro</a></h5>
11792 #include <a href="#7.12"><math.h></a>
11793 int isunordered(real-floating x, real-floating y);</pre>
11794 <h6>Description</h6>
11796 The isunordered macro determines whether its arguments are unordered.
11799 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
11802 <h3><a name="7.13" href="#7.13">7.13 Nonlocal jumps <setjmp.h></a></h3>
11804 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
11805 one type, for bypassing the normal function call and return discipline.<sup><a href="#note216"><b>216)</b></a></sup>
11807 The type declared is
11810 which is an array type suitable for holding the information needed to restore a calling
11811 environment. The environment of a call to the setjmp macro consists of information
11812 sufficient for a call to the longjmp function to return execution to the correct block and
11813 invocation of that block, were it called recursively. It does not include the state of the
11814 floating-point status flags, of open files, or of any other component of the abstract
11817 It is unspecified whether setjmp is a macro or an identifier declared with external
11818 linkage. If a macro definition is suppressed in order to access an actual function, or a
11819 program defines an external identifier with the name setjmp, the behavior is undefined.
11822 <p><small><a name="note216" href="#note216">216)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
11826 <h4><a name="7.13.1" href="#7.13.1">7.13.1 Save calling environment</a></h4>
11828 <h5><a name="7.13.1.1" href="#7.13.1.1">7.13.1.1 The setjmp macro</a></h5>
11832 #include <a href="#7.13"><setjmp.h></a>
11833 int setjmp(jmp_buf env);</pre>
11834 <h6>Description</h6>
11836 The setjmp macro saves its calling environment in its jmp_buf argument for later use
11837 by the longjmp function.
11840 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
11841 return is from a call to the longjmp function, the setjmp macro returns a nonzero
11843 Environmental limits
11845 An invocation of the setjmp macro shall appear only in one of the following contexts:
11847 <li> the entire controlling expression of a selection or iteration statement;
11848 <li> one operand of a relational or equality operator with the other operand an integer
11849 constant expression, with the resulting expression being the entire controlling
11853 expression of a selection or iteration statement;
11854 <li> the operand of a unary ! operator with the resulting expression being the entire
11855 controlling expression of a selection or iteration statement; or
11856 <li> the entire expression of an expression statement (possibly cast to void).
11859 If the invocation appears in any other context, the behavior is undefined.
11861 <h4><a name="7.13.2" href="#7.13.2">7.13.2 Restore calling environment</a></h4>
11863 <h5><a name="7.13.2.1" href="#7.13.2.1">7.13.2.1 The longjmp function</a></h5>
11867 #include <a href="#7.13"><setjmp.h></a>
11868 void longjmp(jmp_buf env, int val);</pre>
11869 <h6>Description</h6>
11871 The longjmp function restores the environment saved by the most recent invocation of
11872 the setjmp macro in the same invocation of the program with the corresponding
11873 jmp_buf argument. If there has been no such invocation, or if the function containing
11874 the invocation of the setjmp macro has terminated execution<sup><a href="#note217"><b>217)</b></a></sup> in the interim, or if the
11875 invocation of the setjmp macro was within the scope of an identifier with variably
11876 modified type and execution has left that scope in the interim, the behavior is undefined.
11878 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note218"><b>218)</b></a></sup>
11879 have state, as of the time the longjmp function was called, except that the values of
11880 objects of automatic storage duration that are local to the function containing the
11881 invocation of the corresponding setjmp macro that do not have volatile-qualified type
11882 and have been changed between the setjmp invocation and longjmp call are
11886 After longjmp is completed, program execution continues as if the corresponding
11887 invocation of the setjmp macro had just returned the value specified by val. The
11888 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
11889 the setjmp macro returns the value 1.
11891 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
11892 might cause memory associated with a variable length array object to be squandered.
11900 #include <a href="#7.13"><setjmp.h></a>
11907 int x[n]; // valid: f is not terminated
11913 int a[n]; // a may remain allocated
11918 int b[n]; // b may remain allocated
11919 longjmp(buf, 2); // might cause memory loss
11923 <p><small><a name="note217" href="#note217">217)</a> For example, by executing a return statement or because another longjmp call has caused a
11924 transfer to a setjmp invocation in a function earlier in the set of nested calls.
11926 <p><small><a name="note218" href="#note218">218)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
11929 <h3><a name="7.14" href="#7.14">7.14 Signal handling <signal.h></a></h3>
11931 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
11932 for handling various signals (conditions that may be reported during program execution).
11934 The type defined is
11937 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
11938 an atomic entity, even in the presence of asynchronous interrupts.
11940 The macros defined are
11945 which expand to constant expressions with distinct values that have type compatible with
11946 the second argument to, and the return value of, the signal function, and whose values
11947 compare unequal to the address of any declarable function; and the following, which
11948 expand to positive integer constant expressions with type int and distinct values that are
11949 the signal numbers, each corresponding to the specified condition:
11952 SIGABRT abnormal termination, such as is initiated by the abort function
11953 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
11954 resulting in overflow
11955 SIGILL detection of an invalid function image, such as an invalid instruction
11956 SIGINT receipt of an interactive attention signal
11957 SIGSEGV an invalid access to storage
11958 SIGTERM a termination request sent to the program</pre>
11959 An implementation need not generate any of these signals, except as a result of explicit
11960 calls to the raise function. Additional signals and pointers to undeclarable functions,
11961 with macro definitions beginning, respectively, with the letters SIG and an uppercase
11962 letter or with SIG_ and an uppercase letter,<sup><a href="#note219"><b>219)</b></a></sup> may also be specified by the
11963 implementation. The complete set of signals, their semantics, and their default handling
11964 is implementation-defined; all signal numbers shall be positive.
11972 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>). The names of the signal numbers reflect the following terms
11973 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
11977 <h4><a name="7.14.1" href="#7.14.1">7.14.1 Specify signal handling</a></h4>
11979 <h5><a name="7.14.1.1" href="#7.14.1.1">7.14.1.1 The signal function</a></h5>
11983 #include <a href="#7.14"><signal.h></a>
11984 void (*signal(int sig, void (*func)(int)))(int);</pre>
11985 <h6>Description</h6>
11987 The signal function chooses one of three ways in which receipt of the signal number
11988 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
11989 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
11990 Otherwise, func shall point to a function to be called when that signal occurs. An
11991 invocation of such a function because of a signal, or (recursively) of any further functions
11992 called by that invocation (other than functions in the standard library), is called a signal
11995 When a signal occurs and func points to a function, it is implementation-defined
11996 whether the equivalent of signal(sig, SIG_DFL); is executed or the
11997 implementation prevents some implementation-defined set of signals (at least including
11998 sig) from occurring until the current signal handling has completed; in the case of
11999 SIGILL, the implementation may alternatively define that no action is taken. Then the
12000 equivalent of (*func)(sig); is executed. If and when the function returns, if the
12001 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
12002 value corresponding to a computational exception, the behavior is undefined; otherwise
12003 the program will resume execution at the point it was interrupted.
12005 If the signal occurs as the result of calling the abort or raise function, the signal
12006 handler shall not call the raise function.
12008 If the signal occurs other than as the result of calling the abort or raise function, the
12009 behavior is undefined if the signal handler refers to any object with static storage duration
12010 other than by assigning a value to an object declared as volatile sig_atomic_t, or
12011 the signal handler calls any function in the standard library other than the abort
12012 function, the _Exit function, or the signal function with the first argument equal to
12013 the signal number corresponding to the signal that caused the invocation of the handler.
12014 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
12015 value of errno is indeterminate.<sup><a href="#note220"><b>220)</b></a></sup>
12017 At program startup, the equivalent of
12019 signal(sig, SIG_IGN);</pre>
12023 may be executed for some signals selected in an implementation-defined manner; the
12026 signal(sig, SIG_DFL);</pre>
12027 is executed for all other signals defined by the implementation.
12029 The implementation shall behave as if no library function calls the signal function.
12032 If the request can be honored, the signal function returns the value of func for the
12033 most recent successful call to signal for the specified signal sig. Otherwise, a value of
12034 SIG_ERR is returned and a positive value is stored in errno.
12035 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the
12036 _Exit function (<a href="#7.20.4.4">7.20.4.4</a>).
12039 <p><small><a name="note220" href="#note220">220)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
12042 <h4><a name="7.14.2" href="#7.14.2">7.14.2 Send signal</a></h4>
12044 <h5><a name="7.14.2.1" href="#7.14.2.1">7.14.2.1 The raise function</a></h5>
12048 #include <a href="#7.14"><signal.h></a>
12049 int raise(int sig);</pre>
12050 <h6>Description</h6>
12052 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
12053 signal handler is called, the raise function shall not return until after the signal handler
12057 The raise function returns zero if successful, nonzero if unsuccessful.
12060 <h3><a name="7.15" href="#7.15">7.15 Variable arguments <stdarg.h></a></h3>
12062 The header <a href="#7.15"><stdarg.h></a> declares a type and defines four macros, for advancing
12063 through a list of arguments whose number and types are not known to the called function
12064 when it is translated.
12066 A function may be called with a variable number of arguments of varying types. As
12067 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
12068 parameter plays a special role in the access mechanism, and will be designated parmN in
12071 The type declared is
12074 which is an object type suitable for holding information needed by the macros
12075 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
12076 desired, the called function shall declare an object (generally referred to as ap in this
12077 subclause) having type va_list. The object ap may be passed as an argument to
12078 another function; if that function invokes the va_arg macro with parameter ap, the
12079 value of ap in the calling function is indeterminate and shall be passed to the va_end
12080 macro prior to any further reference to ap.<sup><a href="#note221"><b>221)</b></a></sup>
12083 <p><small><a name="note221" href="#note221">221)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
12084 case the original function may make further use of the original list after the other function returns.
12087 <h4><a name="7.15.1" href="#7.15.1">7.15.1 Variable argument list access macros</a></h4>
12089 The va_start and va_arg macros described in this subclause shall be implemented
12090 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
12091 identifiers declared with external linkage. If a macro definition is suppressed in order to
12092 access an actual function, or a program defines an external identifier with the same name,
12093 the behavior is undefined. Each invocation of the va_start and va_copy macros
12094 shall be matched by a corresponding invocation of the va_end macro in the same
12097 <h5><a name="7.15.1.1" href="#7.15.1.1">7.15.1.1 The va_arg macro</a></h5>
12101 #include <a href="#7.15"><stdarg.h></a>
12102 type va_arg(va_list ap, type);</pre>
12103 <h6>Description</h6>
12105 The va_arg macro expands to an expression that has the specified type and the value of
12106 the next argument in the call. The parameter ap shall have been initialized by the
12107 va_start or va_copy macro (without an intervening invocation of the va_end
12110 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
12111 values of successive arguments are returned in turn. The parameter type shall be a type
12112 name specified such that the type of a pointer to an object that has the specified type can
12113 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
12114 type is not compatible with the type of the actual next argument (as promoted according
12115 to the default argument promotions), the behavior is undefined, except for the following
12118 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
12119 type, and the value is representable in both types;
12120 <li> one type is pointer to void and the other is a pointer to a character type.
12124 The first invocation of the va_arg macro after that of the va_start macro returns the
12125 value of the argument after that specified by parmN . Successive invocations return the
12126 values of the remaining arguments in succession.
12128 <h5><a name="7.15.1.2" href="#7.15.1.2">7.15.1.2 The va_copy macro</a></h5>
12132 #include <a href="#7.15"><stdarg.h></a>
12133 void va_copy(va_list dest, va_list src);</pre>
12134 <h6>Description</h6>
12136 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
12137 been applied to dest followed by the same sequence of uses of the va_arg macro as
12138 had previously been used to reach the present state of src. Neither the va_copy nor
12139 va_start macro shall be invoked to reinitialize dest without an intervening
12140 invocation of the va_end macro for the same dest.
12143 The va_copy macro returns no value.
12145 <h5><a name="7.15.1.3" href="#7.15.1.3">7.15.1.3 The va_end macro</a></h5>
12149 #include <a href="#7.15"><stdarg.h></a>
12150 void va_end(va_list ap);</pre>
12151 <h6>Description</h6>
12153 The va_end macro facilitates a normal return from the function whose variable
12154 argument list was referred to by the expansion of the va_start macro, or the function
12155 containing the expansion of the va_copy macro, that initialized the va_list ap. The
12156 va_end macro may modify ap so that it is no longer usable (without being reinitialized
12158 by the va_start or va_copy macro). If there is no corresponding invocation of the
12159 va_start or va_copy macro, or if the va_end macro is not invoked before the
12160 return, the behavior is undefined.
12163 The va_end macro returns no value.
12165 <h5><a name="7.15.1.4" href="#7.15.1.4">7.15.1.4 The va_start macro</a></h5>
12169 #include <a href="#7.15"><stdarg.h></a>
12170 void va_start(va_list ap, parmN);</pre>
12171 <h6>Description</h6>
12173 The va_start macro shall be invoked before any access to the unnamed arguments.
12175 The va_start macro initializes ap for subsequent use by the va_arg and va_end
12176 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
12177 without an intervening invocation of the va_end macro for the same ap.
12179 The parameter parmN is the identifier of the rightmost parameter in the variable
12180 parameter list in the function definition (the one just before the , ...). If the parameter
12181 parmN is declared with the register storage class, with a function or array type, or
12182 with a type that is not compatible with the type that results after application of the default
12183 argument promotions, the behavior is undefined.
12186 The va_start macro returns no value.
12188 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
12189 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
12190 pointers is specified by the first argument to f1.
12193 #include <a href="#7.15"><stdarg.h></a>
12195 void f1(int n_ptrs, ...)
12198 char *array[MAXARGS];
12200 if (n_ptrs > MAXARGS)
12202 va_start(ap, n_ptrs);
12203 while (ptr_no < n_ptrs)
12204 array[ptr_no++] = va_arg(ap, char *);
12208 Each call to f1 is required to have visible the definition of the function or a declaration such as
12210 void f1(int, ...);</pre>
12213 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
12214 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
12215 is gathered again and passed to function f4.
12218 #include <a href="#7.15"><stdarg.h></a>
12220 void f3(int n_ptrs, int f4_after, ...)
12222 va_list ap, ap_save;
12223 char *array[MAXARGS];
12225 if (n_ptrs > MAXARGS)
12227 va_start(ap, f4_after);
12228 while (ptr_no < n_ptrs) {
12229 array[ptr_no++] = va_arg(ap, char *);
12230 if (ptr_no == f4_after)
12231 va_copy(ap_save, ap);
12235 // Now process the saved copy.
12236 n_ptrs -= f4_after;
12238 while (ptr_no < n_ptrs)
12239 array[ptr_no++] = va_arg(ap_save, char *);
12244 <h3><a name="7.16" href="#7.16">7.16 Boolean type and values <stdbool.h></a></h3>
12246 The header <a href="#7.16"><stdbool.h></a> defines four macros.
12253 The remaining three macros are suitable for use in #if preprocessing directives. They
12257 which expands to the integer constant 1,
12260 which expands to the integer constant 0, and
12262 __bool_true_false_are_defined</pre>
12263 which expands to the integer constant 1.
12265 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
12266 redefine the macros bool, true, and false.<sup><a href="#note222"><b>222)</b></a></sup>
12274 <p><small><a name="note222" href="#note222">222)</a> See ''future library directions'' (<a href="#7.26.7">7.26.7</a>).
12277 <h3><a name="7.17" href="#7.17">7.17 Common definitions <stddef.h></a></h3>
12279 The following types and macros are defined in the standard header <a href="#7.17"><stddef.h></a>. Some
12280 are also defined in other headers, as noted in their respective subclauses.
12285 which is the signed integer type of the result of subtracting two pointers;
12288 which is the unsigned integer type of the result of the sizeof operator; and
12291 which is an integer type whose range of values can represent distinct codes for all
12292 members of the largest extended character set specified among the supported locales; the
12293 null character shall have the code value zero. Each member of the basic character set
12294 shall have a code value equal to its value when used as the lone character in an integer
12295 character constant if an implementation does not define
12296 __STDC_MB_MIGHT_NEQ_WC__.
12301 which expands to an implementation-defined null pointer constant; and
12303 offsetof(type, member-designator)</pre>
12304 which expands to an integer constant expression that has type size_t, the value of
12305 which is the offset in bytes, to the structure member (designated by member-designator),
12306 from the beginning of its structure (designated by type). The type and member designator
12307 shall be such that given
12309 static type t;</pre>
12310 then the expression &(t.member-designator) evaluates to an address constant. (If the
12311 specified member is a bit-field, the behavior is undefined.)
12312 <h6> Recommended practice</h6>
12314 The types used for size_t and ptrdiff_t should not have an integer conversion rank
12315 greater than that of signed long int unless the implementation supports objects
12316 large enough to make this necessary.
12317 <p><b> Forward references</b>: localization (<a href="#7.11">7.11</a>).
12320 <h3><a name="7.18" href="#7.18">7.18 Integer types <stdint.h></a></h3>
12322 The header <a href="#7.18"><stdint.h></a> declares sets of integer types having specified widths, and
12323 defines corresponding sets of macros.<sup><a href="#note223"><b>223)</b></a></sup> It also defines macros that specify limits of
12324 integer types corresponding to types defined in other standard headers.
12326 Types are defined in the following categories:
12328 <li> integer types having certain exact widths;
12329 <li> integer types having at least certain specified widths;
12330 <li> fastest integer types having at least certain specified widths;
12331 <li> integer types wide enough to hold pointers to objects;
12332 <li> integer types having greatest width.
12334 (Some of these types may denote the same type.)
12336 Corresponding macros specify limits of the declared types and construct suitable
12339 For each type described herein that the implementation provides,<sup><a href="#note224"><b>224)</b></a></sup> <a href="#7.18"><stdint.h></a> shall
12340 declare that typedef name and define the associated macros. Conversely, for each type
12341 described herein that the implementation does not provide, <a href="#7.18"><stdint.h></a> shall not
12342 declare that typedef name nor shall it define the associated macros. An implementation
12343 shall provide those types described as ''required'', but need not provide any of the others
12344 (described as ''optional'').
12347 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.26.8">7.26.8</a>).
12349 <p><small><a name="note224" href="#note224">224)</a> Some of these types may denote implementation-defined extended integer types.
12352 <h4><a name="7.18.1" href="#7.18.1">7.18.1 Integer types</a></h4>
12354 When typedef names differing only in the absence or presence of the initial u are defined,
12355 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
12356 implementation providing one of these corresponding types shall also provide the other.
12358 In the following descriptions, the symbol N represents an unsigned decimal integer with
12359 no leading zeros (e.g., 8 or 24, but not 04 or 048).
12366 <h5><a name="7.18.1.1" href="#7.18.1.1">7.18.1.1 Exact-width integer types</a></h5>
12368 The typedef name intN_t designates a signed integer type with width N , no padding
12369 bits, and a two's complement representation. Thus, int8_t denotes a signed integer
12370 type with a width of exactly 8 bits.
12372 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
12373 uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
12375 These types are optional. However, if an implementation provides integer types with
12376 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
12377 two's complement representation, it shall define the corresponding typedef names.
12379 <h5><a name="7.18.1.2" href="#7.18.1.2">7.18.1.2 Minimum-width integer types</a></h5>
12381 The typedef name int_leastN_t designates a signed integer type with a width of at
12382 least N , such that no signed integer type with lesser size has at least the specified width.
12383 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
12385 The typedef name uint_leastN_t designates an unsigned integer type with a width
12386 of at least N , such that no unsigned integer type with lesser size has at least the specified
12387 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
12390 The following types are required:
12392 int_least8_t uint_least8_t
12393 int_least16_t uint_least16_t
12394 int_least32_t uint_least32_t
12395 int_least64_t uint_least64_t</pre>
12396 All other types of this form are optional.
12398 <h5><a name="7.18.1.3" href="#7.18.1.3">7.18.1.3 Fastest minimum-width integer types</a></h5>
12400 Each of the following types designates an integer type that is usually fastest<sup><a href="#note225"><b>225)</b></a></sup> to operate
12401 with among all integer types that have at least the specified width.
12403 The typedef name int_fastN_t designates the fastest signed integer type with a width
12404 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
12405 type with a width of at least N .
12412 The following types are required:
12414 int_fast8_t uint_fast8_t
12415 int_fast16_t uint_fast16_t
12416 int_fast32_t uint_fast32_t
12417 int_fast64_t uint_fast64_t</pre>
12418 All other types of this form are optional.
12421 <p><small><a name="note225" href="#note225">225)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
12422 grounds for choosing one type over another, it will simply pick some integer type satisfying the
12423 signedness and width requirements.
12426 <h5><a name="7.18.1.4" href="#7.18.1.4">7.18.1.4 Integer types capable of holding object pointers</a></h5>
12428 The following type designates a signed integer type with the property that any valid
12429 pointer to void can be converted to this type, then converted back to pointer to void,
12430 and the result will compare equal to the original pointer:
12433 The following type designates an unsigned integer type with the property that any valid
12434 pointer to void can be converted to this type, then converted back to pointer to void,
12435 and the result will compare equal to the original pointer:
12438 These types are optional.
12440 <h5><a name="7.18.1.5" href="#7.18.1.5">7.18.1.5 Greatest-width integer types</a></h5>
12442 The following type designates a signed integer type capable of representing any value of
12443 any signed integer type:
12446 The following type designates an unsigned integer type capable of representing any value
12447 of any unsigned integer type:
12450 These types are required.
12452 <h4><a name="7.18.2" href="#7.18.2">7.18.2 Limits of specified-width integer types</a></h4>
12454 The following object-like macros<sup><a href="#note226"><b>226)</b></a></sup> specify the minimum and maximum limits of the
12455 types declared in <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in
12456 <a href="#7.18.1">7.18.1</a>.
12458 Each instance of any defined macro shall be replaced by a constant expression suitable
12459 for use in #if preprocessing directives, and this expression shall have the same type as
12460 would an expression that is an object of the corresponding type converted according to
12463 the integer promotions. Its implementation-defined value shall be equal to or greater in
12464 magnitude (absolute value) than the corresponding value given below, with the same sign,
12465 except where stated to be exactly the given value.
12468 <p><small><a name="note226" href="#note226">226)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12469 before <a href="#7.18"><stdint.h></a> is included.
12472 <h5><a name="7.18.2.1" href="#7.18.2.1">7.18.2.1 Limits of exact-width integer types</a></h5>
12475 <li> minimum values of exact-width signed integer types
12476 INTN_MIN exactly -(2 N -1 )
12477 <li> maximum values of exact-width signed integer types
12478 INTN_MAX exactly 2 N -1 - 1
12479 <li> maximum values of exact-width unsigned integer types
12480 UINTN_MAX exactly 2 N - 1
12483 <h5><a name="7.18.2.2" href="#7.18.2.2">7.18.2.2 Limits of minimum-width integer types</a></h5>
12486 <li> minimum values of minimum-width signed integer types
12487 INT_LEASTN_MIN -(2 N -1 - 1)
12488 <li> maximum values of minimum-width signed integer types
12489 INT_LEASTN_MAX 2 N -1 - 1
12490 <li> maximum values of minimum-width unsigned integer types
12491 UINT_LEASTN_MAX 2N - 1
12494 <h5><a name="7.18.2.3" href="#7.18.2.3">7.18.2.3 Limits of fastest minimum-width integer types</a></h5>
12497 <li> minimum values of fastest minimum-width signed integer types
12498 INT_FASTN_MIN -(2 N -1 - 1)
12499 <li> maximum values of fastest minimum-width signed integer types
12500 INT_FASTN_MAX 2 N -1 - 1
12501 <li> maximum values of fastest minimum-width unsigned integer types
12502 UINT_FASTN_MAX 2N - 1
12505 <h5><a name="7.18.2.4" href="#7.18.2.4">7.18.2.4 Limits of integer types capable of holding object pointers</a></h5>
12508 <li> minimum value of pointer-holding signed integer type
12510 INTPTR_MIN -(215 - 1)</pre>
12511 <li> maximum value of pointer-holding signed integer type
12514 INTPTR_MAX 215 - 1</pre>
12515 <li> maximum value of pointer-holding unsigned integer type
12516 UINTPTR_MAX 216 - 1
12519 <h5><a name="7.18.2.5" href="#7.18.2.5">7.18.2.5 Limits of greatest-width integer types</a></h5>
12522 <li> minimum value of greatest-width signed integer type
12523 INTMAX_MIN -(263 - 1)
12524 <li> maximum value of greatest-width signed integer type
12526 <li> maximum value of greatest-width unsigned integer type
12527 UINTMAX_MAX 264 - 1
12530 <h4><a name="7.18.3" href="#7.18.3">7.18.3 Limits of other integer types</a></h4>
12532 The following object-like macros<sup><a href="#note227"><b>227)</b></a></sup> specify the minimum and maximum limits of
12533 integer types corresponding to types defined in other standard headers.
12535 Each instance of these macros shall be replaced by a constant expression suitable for use
12536 in #if preprocessing directives, and this expression shall have the same type as would an
12537 expression that is an object of the corresponding type converted according to the integer
12538 promotions. Its implementation-defined value shall be equal to or greater in magnitude
12539 (absolute value) than the corresponding value given below, with the same sign. An
12540 implementation shall define only the macros corresponding to those typedef names it
12541 actually provides.<sup><a href="#note228"><b>228)</b></a></sup>
12543 <li> limits of ptrdiff_t
12546 <li> limits of sig_atomic_t
12547 SIG_ATOMIC_MIN see below
12548 SIG_ATOMIC_MAX see below
12549 <li> limit of size_t
12551 <li> limits of wchar_t
12556 WCHAR_MIN see below
12557 WCHAR_MAX see below
12558 <li> limits of wint_t
12563 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
12564 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
12565 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
12566 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
12567 SIG_ATOMIC_MAX shall be no less than 255.
12569 If wchar_t (see <a href="#7.17">7.17</a>) is defined as a signed integer type, the value of WCHAR_MIN
12570 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
12571 otherwise, wchar_t is defined as an unsigned integer type, and the value of
12572 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note229"><b>229)</b></a></sup>
12574 If wint_t (see <a href="#7.24">7.24</a>) is defined as a signed integer type, the value of WINT_MIN shall
12575 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
12576 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
12577 shall be 0 and the value of WINT_MAX shall be no less than 65535.
12580 <p><small><a name="note227" href="#note227">227)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12581 before <a href="#7.18"><stdint.h></a> is included.
12583 <p><small><a name="note228" href="#note228">228)</a> A freestanding implementation need not provide all of these types.
12585 <p><small><a name="note229" href="#note229">229)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
12589 <h4><a name="7.18.4" href="#7.18.4">7.18.4 Macros for integer constants</a></h4>
12591 The following function-like macros<sup><a href="#note230"><b>230)</b></a></sup> expand to integer constants suitable for
12592 initializing objects that have integer types corresponding to types defined in
12593 <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in <a href="#7.18.1.2">7.18.1.2</a> or
12594 <a href="#7.18.1.5">7.18.1.5</a>.
12596 The argument in any instance of these macros shall be an unsuffixed integer constant (as
12597 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.
12599 Each invocation of one of these macros shall expand to an integer constant expression
12600 suitable for use in #if preprocessing directives. The type of the expression shall have
12601 the same type as would an expression of the corresponding type converted according to
12602 the integer promotions. The value of the expression shall be that of the argument.
12610 <p><small><a name="note230" href="#note230">230)</a> C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is
12611 defined before <a href="#7.18"><stdint.h></a> is included.
12614 <h5><a name="7.18.4.1" href="#7.18.4.1">7.18.4.1 Macros for minimum-width integer constants</a></h5>
12616 The macro INTN_C(value) shall expand to an integer constant expression
12617 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
12618 to an integer constant expression corresponding to the type uint_leastN_t. For
12619 example, if uint_least64_t is a name for the type unsigned long long int,
12620 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
12622 <h5><a name="7.18.4.2" href="#7.18.4.2">7.18.4.2 Macros for greatest-width integer constants</a></h5>
12624 The following macro expands to an integer constant expression having the value specified
12625 by its argument and the type intmax_t:
12627 INTMAX_C(value)</pre>
12628 The following macro expands to an integer constant expression having the value specified
12629 by its argument and the type uintmax_t:
12632 UINTMAX_C(value)</pre>
12634 <h3><a name="7.19" href="#7.19">7.19 Input/output <stdio.h></a></h3>
12636 <h4><a name="7.19.1" href="#7.19.1">7.19.1 Introduction</a></h4>
12638 The header <a href="#7.19"><stdio.h></a> declares three types, several macros, and many functions for
12639 performing input and output.
12641 The types declared are size_t (described in <a href="#7.17">7.17</a>);
12644 which is an object type capable of recording all the information needed to control a
12645 stream, including its file position indicator, a pointer to its associated buffer (if any), an
12646 error indicator that records whether a read/write error has occurred, and an end-of-file
12647 indicator that records whether the end of the file has been reached; and
12650 which is an object type other than an array type capable of recording all the information
12651 needed to specify uniquely every position within a file.
12653 The macros are NULL (described in <a href="#7.17">7.17</a>);
12658 which expand to integer constant expressions with distinct values, suitable for use as the
12659 third argument to the setvbuf function;
12662 which expands to an integer constant expression that is the size of the buffer used by the
12666 which expands to an integer constant expression, with type int and a negative value, that
12667 is returned by several functions to indicate end-of-file, that is, no more input from a
12671 which expands to an integer constant expression that is the minimum number of files that
12672 the implementation guarantees can be open simultaneously;
12675 which expands to an integer constant expression that is the size needed for an array of
12676 char large enough to hold the longest file name string that the implementation
12678 guarantees can be opened;<sup><a href="#note231"><b>231)</b></a></sup>
12681 which expands to an integer constant expression that is the size needed for an array of
12682 char large enough to hold a temporary file name string generated by the tmpnam
12688 which expand to integer constant expressions with distinct values, suitable for use as the
12689 third argument to the fseek function;
12692 which expands to an integer constant expression that is the maximum number of unique
12693 file names that can be generated by the tmpnam function;
12698 which are expressions of type ''pointer to FILE'' that point to the FILE objects
12699 associated, respectively, with the standard error, input, and output streams.
12701 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide character input
12702 and output. The wide character input/output functions described in that subclause
12703 provide operations analogous to most of those described here, except that the
12704 fundamental units internal to the program are wide characters. The external
12705 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
12706 described further in <a href="#7.19.3">7.19.3</a>.
12708 The input/output functions are given the following collective terms:
12710 <li> The wide character input functions -- those functions described in <a href="#7.24">7.24</a> that perform
12711 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
12712 fwscanf, wscanf, vfwscanf, and vwscanf.
12713 <li> The wide character output functions -- those functions described in <a href="#7.24">7.24</a> that perform
12714 output from wide characters and wide strings: fputwc, fputws, putwc,
12715 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
12719 <li> The wide character input/output functions -- the union of the ungetwc function, the
12720 wide character input functions, and the wide character output functions.
12721 <li> The byte input/output functions -- those functions described in this subclause that
12722 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
12723 fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts,
12724 scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
12726 <p><b> Forward references</b>: files (<a href="#7.19.3">7.19.3</a>), the fseek function (<a href="#7.19.9.2">7.19.9.2</a>), streams (<a href="#7.19.2">7.19.2</a>), the
12727 tmpnam function (<a href="#7.19.4.4">7.19.4.4</a>), <a href="#7.24"><wchar.h></a> (<a href="#7.24">7.24</a>).
12730 <p><small><a name="note231" href="#note231">231)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
12731 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
12732 string. Of course, file name string contents are subject to other system-specific constraints; therefore
12733 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
12736 <h4><a name="7.19.2" href="#7.19.2">7.19.2 Streams</a></h4>
12738 Input and output, whether to or from physical devices such as terminals and tape drives,
12739 or whether to or from files supported on structured storage devices, are mapped into
12740 logical data streams, whose properties are more uniform than their various inputs and
12741 outputs. Two forms of mapping are supported, for text streams and for binary
12742 streams.<sup><a href="#note232"><b>232)</b></a></sup>
12744 A text stream is an ordered sequence of characters composed into lines, each line
12745 consisting of zero or more characters plus a terminating new-line character. Whether the
12746 last line requires a terminating new-line character is implementation-defined. Characters
12747 may have to be added, altered, or deleted on input and output to conform to differing
12748 conventions for representing text in the host environment. Thus, there need not be a one-
12749 to-one correspondence between the characters in a stream and those in the external
12750 representation. Data read in from a text stream will necessarily compare equal to the data
12751 that were earlier written out to that stream only if: the data consist only of printing
12752 characters and the control characters horizontal tab and new-line; no new-line character is
12753 immediately preceded by space characters; and the last character is a new-line character.
12754 Whether space characters that are written out immediately before a new-line character
12755 appear when read in is implementation-defined.
12757 A binary stream is an ordered sequence of characters that can transparently record
12758 internal data. Data read in from a binary stream shall compare equal to the data that were
12759 earlier written out to that stream, under the same implementation. Such a stream may,
12760 however, have an implementation-defined number of null characters appended to the end
12763 Each stream has an orientation. After a stream is associated with an external file, but
12764 before any operations are performed on it, the stream is without orientation. Once a wide
12765 character input/output function has been applied to a stream without orientation, the
12769 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12770 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12771 Only a call to the freopen function or the fwide function can otherwise alter the
12772 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note233"><b>233)</b></a></sup>
12774 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12775 character input/output functions shall not be applied to a byte-oriented stream. The
12776 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12777 except for the following additional restrictions:
12779 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12780 text and binary streams.
12781 <li> For wide-oriented streams, after a successful call to a file-positioning function that
12782 leaves the file position indicator prior to the end-of-file, a wide character output
12783 function can overwrite a partial multibyte character; any file contents beyond the
12784 byte(s) written are henceforth indeterminate.
12787 Each wide-oriented stream has an associated mbstate_t object that stores the current
12788 parse state of the stream. A successful call to fgetpos stores a representation of the
12789 value of this mbstate_t object as part of the value of the fpos_t object. A later
12790 successful call to fsetpos using the same stored fpos_t value restores the value of
12791 the associated mbstate_t object as well as the position within the controlled stream.
12792 Environmental limits
12794 An implementation shall support text files with lines containing at least 254 characters,
12795 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12797 <p><b> Forward references</b>: the freopen function (<a href="#7.19.5.4">7.19.5.4</a>), the fwide function (<a href="#7.24.3.5">7.24.3.5</a>),
12798 mbstate_t (<a href="#7.25.1">7.25.1</a>), the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>), the fsetpos function
12799 (<a href="#7.19.9.3">7.19.9.3</a>).
12807 <p><small><a name="note232" href="#note232">232)</a> An implementation need not distinguish between text streams and binary streams. In such an
12808 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12811 <p><small><a name="note233" href="#note233">233)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12814 <h4><a name="7.19.3" href="#7.19.3">7.19.3 Files</a></h4>
12816 A stream is associated with an external file (which may be a physical device) by opening
12817 a file, which may involve creating a new file. Creating an existing file causes its former
12818 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12819 disk file, as opposed to a terminal), then a file position indicator associated with the
12820 stream is positioned at the start (character number zero) of the file, unless the file is
12821 opened with append mode in which case it is implementation-defined whether the file
12822 position indicator is initially positioned at the beginning or the end of the file. The file
12823 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12824 facilitate an orderly progression through the file.
12826 Binary files are not truncated, except as defined in <a href="#7.19.5.3">7.19.5.3</a>. Whether a write on a text
12827 stream causes the associated file to be truncated beyond that point is implementation-
12830 When a stream is unbuffered, characters are intended to appear from the source or at the
12831 destination as soon as possible. Otherwise characters may be accumulated and
12832 transmitted to or from the host environment as a block. When a stream is fully buffered,
12833 characters are intended to be transmitted to or from the host environment as a block when
12834 a buffer is filled. When a stream is line buffered, characters are intended to be
12835 transmitted to or from the host environment as a block when a new-line character is
12836 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12837 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12838 when input is requested on a line buffered stream that requires the transmission of
12839 characters from the host environment. Support for these characteristics is
12840 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12842 A file may be disassociated from a controlling stream by closing the file. Output streams
12843 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12844 the stream is disassociated from the file. The value of a pointer to a FILE object is
12845 indeterminate after the associated file is closed (including the standard text streams).
12846 Whether a file of zero length (on which no characters have been written by an output
12847 stream) actually exists is implementation-defined.
12849 The file may be subsequently reopened, by the same or another program execution, and
12850 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12851 function returns to its original caller, or if the exit function is called, all open files are
12852 closed (hence all output streams are flushed) before program termination. Other paths to
12853 program termination, such as calling the abort function, need not close all files
12856 The address of the FILE object used to control a stream may be significant; a copy of a
12857 FILE object need not serve in place of the original.
12860 At program startup, three text streams are predefined and need not be opened explicitly
12862 <li> standard input (for reading conventional input), standard output (for writing
12864 conventional output), and standard error (for writing diagnostic output). As initially
12865 opened, the standard error stream is not fully buffered; the standard input and standard
12866 output streams are fully buffered if and only if the stream can be determined not to refer
12867 to an interactive device.
12869 Functions that open additional (nontemporary) files require a file name, which is a string.
12870 The rules for composing valid file names are implementation-defined. Whether the same
12871 file can be simultaneously open multiple times is also implementation-defined.
12873 Although both text and binary wide-oriented streams are conceptually sequences of wide
12874 characters, the external file associated with a wide-oriented stream is a sequence of
12875 multibyte characters, generalized as follows:
12877 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12878 encodings valid for use internal to the program).
12879 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note234"><b>234)</b></a></sup>
12882 Moreover, the encodings used for multibyte characters may differ among files. Both the
12883 nature and choice of such encodings are implementation-defined.
12885 The wide character input functions read multibyte characters from the stream and convert
12886 them to wide characters as if they were read by successive calls to the fgetwc function.
12887 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12888 described by the stream's own mbstate_t object. The byte input functions read
12889 characters from the stream as if by successive calls to the fgetc function.
12891 The wide character output functions convert wide characters to multibyte characters and
12892 write them to the stream as if they were written by successive calls to the fputwc
12893 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12894 conversion state described by the stream's own mbstate_t object. The byte output
12895 functions write characters to the stream as if by successive calls to the fputc function.
12897 In some cases, some of the byte input/output functions also perform conversions between
12898 multibyte characters and wide characters. These conversions also occur as if by calls to
12899 the mbrtowc and wcrtomb functions.
12901 An encoding error occurs if the character sequence presented to the underlying
12902 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12903 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12907 multibyte character. The wide character input/output functions and the byte input/output
12908 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12910 Environmental limits
12912 The value of FOPEN_MAX shall be at least eight, including the three standard text
12914 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the fgetc function (<a href="#7.19.7.1">7.19.7.1</a>), the
12915 fopen function (<a href="#7.19.5.3">7.19.5.3</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>), the setbuf function
12916 (<a href="#7.19.5.5">7.19.5.5</a>), the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>), the fgetwc function (<a href="#7.24.3.1">7.24.3.1</a>), the
12917 fputwc function (<a href="#7.24.3.3">7.24.3.3</a>), conversion state (<a href="#7.24.6">7.24.6</a>), the mbrtowc function
12918 (<a href="#7.24.6.3.2">7.24.6.3.2</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
12921 <p><small><a name="note234" href="#note234">234)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
12922 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12923 with state-dependent encoding that does not assuredly end in the initial shift state.
12926 <h4><a name="7.19.4" href="#7.19.4">7.19.4 Operations on files</a></h4>
12928 <h5><a name="7.19.4.1" href="#7.19.4.1">7.19.4.1 The remove function</a></h5>
12932 #include <a href="#7.19"><stdio.h></a>
12933 int remove(const char *filename);</pre>
12934 <h6>Description</h6>
12936 The remove function causes the file whose name is the string pointed to by filename
12937 to be no longer accessible by that name. A subsequent attempt to open that file using that
12938 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12939 function is implementation-defined.
12942 The remove function returns zero if the operation succeeds, nonzero if it fails.
12944 <h5><a name="7.19.4.2" href="#7.19.4.2">7.19.4.2 The rename function</a></h5>
12948 #include <a href="#7.19"><stdio.h></a>
12949 int rename(const char *old, const char *new);</pre>
12950 <h6>Description</h6>
12952 The rename function causes the file whose name is the string pointed to by old to be
12953 henceforth known by the name given by the string pointed to by new. The file named
12954 old is no longer accessible by that name. If a file named by the string pointed to by new
12955 exists prior to the call to the rename function, the behavior is implementation-defined.
12959 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note235"><b>235)</b></a></sup> in
12960 which case if the file existed previously it is still known by its original name.
12963 <p><small><a name="note235" href="#note235">235)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
12964 or that it is necessary to copy its contents to effectuate its renaming.
12967 <h5><a name="7.19.4.3" href="#7.19.4.3">7.19.4.3 The tmpfile function</a></h5>
12971 #include <a href="#7.19"><stdio.h></a>
12972 FILE *tmpfile(void);</pre>
12973 <h6>Description</h6>
12975 The tmpfile function creates a temporary binary file that is different from any other
12976 existing file and that will automatically be removed when it is closed or at program
12977 termination. If the program terminates abnormally, whether an open temporary file is
12978 removed is implementation-defined. The file is opened for update with "wb+" mode.
12979 <h6> Recommended practice</h6>
12981 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12982 program (this limit may be shared with tmpnam) and there should be no limit on the
12983 number simultaneously open other than this limit and any limit on the number of open
12987 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12988 cannot be created, the tmpfile function returns a null pointer.
12989 <p><b> Forward references</b>: the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
12991 <h5><a name="7.19.4.4" href="#7.19.4.4">7.19.4.4 The tmpnam function</a></h5>
12995 #include <a href="#7.19"><stdio.h></a>
12996 char *tmpnam(char *s);</pre>
12997 <h6>Description</h6>
12999 The tmpnam function generates a string that is a valid file name and that is not the same
13000 as the name of an existing file.<sup><a href="#note236"><b>236)</b></a></sup> The function is potentially capable of generating
13004 TMP_MAX different strings, but any or all of them may already be in use by existing files
13005 and thus not be suitable return values.
13007 The tmpnam function generates a different string each time it is called.
13009 The implementation shall behave as if no library function calls the tmpnam function.
13012 If no suitable string can be generated, the tmpnam function returns a null pointer.
13013 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
13014 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
13015 function may modify the same object). If the argument is not a null pointer, it is assumed
13016 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
13017 in that array and returns the argument as its value.
13018 Environmental limits
13020 The value of the macro TMP_MAX shall be at least 25.
13023 <p><small><a name="note236" href="#note236">236)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
13024 their names should not collide with those generated by conventional naming rules for the
13025 implementation. It is still necessary to use the remove function to remove such files when their use
13026 is ended, and before program termination.
13029 <h4><a name="7.19.5" href="#7.19.5">7.19.5 File access functions</a></h4>
13031 <h5><a name="7.19.5.1" href="#7.19.5.1">7.19.5.1 The fclose function</a></h5>
13035 #include <a href="#7.19"><stdio.h></a>
13036 int fclose(FILE *stream);</pre>
13037 <h6>Description</h6>
13039 A successful call to the fclose function causes the stream pointed to by stream to be
13040 flushed and the associated file to be closed. Any unwritten buffered data for the stream
13041 are delivered to the host environment to be written to the file; any unread buffered data
13042 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
13043 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
13044 (and deallocated if it was automatically allocated).
13047 The fclose function returns zero if the stream was successfully closed, or EOF if any
13048 errors were detected.
13050 <h5><a name="7.19.5.2" href="#7.19.5.2">7.19.5.2 The fflush function</a></h5>
13055 #include <a href="#7.19"><stdio.h></a>
13056 int fflush(FILE *stream);</pre>
13057 <h6>Description</h6>
13059 If stream points to an output stream or an update stream in which the most recent
13060 operation was not input, the fflush function causes any unwritten data for that stream
13061 to be delivered to the host environment to be written to the file; otherwise, the behavior is
13064 If stream is a null pointer, the fflush function performs this flushing action on all
13065 streams for which the behavior is defined above.
13068 The fflush function sets the error indicator for the stream and returns EOF if a write
13069 error occurs, otherwise it returns zero.
13070 <p><b> Forward references</b>: the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
13072 <h5><a name="7.19.5.3" href="#7.19.5.3">7.19.5.3 The fopen function</a></h5>
13076 #include <a href="#7.19"><stdio.h></a>
13077 FILE *fopen(const char * restrict filename,
13078 const char * restrict mode);</pre>
13079 <h6>Description</h6>
13081 The fopen function opens the file whose name is the string pointed to by filename,
13082 and associates a stream with it.
13084 The argument mode points to a string. If the string is one of the following, the file is
13085 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note237"><b>237)</b></a></sup>
13086 r open text file for reading
13087 w truncate to zero length or create text file for writing
13088 a append; open or create text file for writing at end-of-file
13089 rb open binary file for reading
13090 wb truncate to zero length or create binary file for writing
13091 ab append; open or create binary file for writing at end-of-file
13092 r+ open text file for update (reading and writing)
13093 w+ truncate to zero length or create text file for update
13094 a+ append; open or create text file for update, writing at end-of-file
13100 r+b or rb+ open binary file for update (reading and writing)
13101 w+b or wb+ truncate to zero length or create binary file for update
13102 a+b or ab+ append; open or create binary file for update, writing at end-of-file
13104 Opening a file with read mode ('r' as the first character in the mode argument) fails if
13105 the file does not exist or cannot be read.
13107 Opening a file with append mode ('a' as the first character in the mode argument)
13108 causes all subsequent writes to the file to be forced to the then current end-of-file,
13109 regardless of intervening calls to the fseek function. In some implementations, opening
13110 a binary file with append mode ('b' as the second or third character in the above list of
13111 mode argument values) may initially position the file position indicator for the stream
13112 beyond the last data written, because of null character padding.
13114 When a file is opened with update mode ('+' as the second or third character in the
13115 above list of mode argument values), both input and output may be performed on the
13116 associated stream. However, output shall not be directly followed by input without an
13117 intervening call to the fflush function or to a file positioning function (fseek,
13118 fsetpos, or rewind), and input shall not be directly followed by output without an
13119 intervening call to a file positioning function, unless the input operation encounters end-
13120 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
13121 binary stream in some implementations.
13123 When opened, a stream is fully buffered if and only if it can be determined not to refer to
13124 an interactive device. The error and end-of-file indicators for the stream are cleared.
13127 The fopen function returns a pointer to the object controlling the stream. If the open
13128 operation fails, fopen returns a null pointer.
13129 <p><b> Forward references</b>: file positioning functions (<a href="#7.19.9">7.19.9</a>).
13132 <p><small><a name="note237" href="#note237">237)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
13133 remaining characters, or it might use them to select different kinds of a file (some of which might not
13134 conform to the properties in <a href="#7.19.2">7.19.2</a>).
13137 <h5><a name="7.19.5.4" href="#7.19.5.4">7.19.5.4 The freopen function</a></h5>
13141 #include <a href="#7.19"><stdio.h></a>
13142 FILE *freopen(const char * restrict filename,
13143 const char * restrict mode,
13144 FILE * restrict stream);</pre>
13145 <h6>Description</h6>
13147 The freopen function opens the file whose name is the string pointed to by filename
13148 and associates the stream pointed to by stream with it. The mode argument is used just
13150 as in the fopen function.<sup><a href="#note238"><b>238)</b></a></sup>
13152 If filename is a null pointer, the freopen function attempts to change the mode of
13153 the stream to that specified by mode, as if the name of the file currently associated with
13154 the stream had been used. It is implementation-defined which changes of mode are
13155 permitted (if any), and under what circumstances.
13157 The freopen function first attempts to close any file that is associated with the specified
13158 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
13159 stream are cleared.
13162 The freopen function returns a null pointer if the open operation fails. Otherwise,
13163 freopen returns the value of stream.
13166 <p><small><a name="note238" href="#note238">238)</a> The primary use of the freopen function is to change the file associated with a standard text stream
13167 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
13168 returned by the fopen function may be assigned.
13171 <h5><a name="7.19.5.5" href="#7.19.5.5">7.19.5.5 The setbuf function</a></h5>
13175 #include <a href="#7.19"><stdio.h></a>
13176 void setbuf(FILE * restrict stream,
13177 char * restrict buf);</pre>
13178 <h6>Description</h6>
13180 Except that it returns no value, the setbuf function is equivalent to the setvbuf
13181 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
13182 is a null pointer), with the value _IONBF for mode.
13185 The setbuf function returns no value.
13186 <p><b> Forward references</b>: the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>).
13188 <h5><a name="7.19.5.6" href="#7.19.5.6">7.19.5.6 The setvbuf function</a></h5>
13192 #include <a href="#7.19"><stdio.h></a>
13193 int setvbuf(FILE * restrict stream,
13194 char * restrict buf,
13195 int mode, size_t size);</pre>
13201 <h6>Description</h6>
13203 The setvbuf function may be used only after the stream pointed to by stream has
13204 been associated with an open file and before any other operation (other than an
13205 unsuccessful call to setvbuf) is performed on the stream. The argument mode
13206 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
13207 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
13208 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
13209 used instead of a buffer allocated by the setvbuf function<sup><a href="#note239"><b>239)</b></a></sup> and the argument size
13210 specifies the size of the array; otherwise, size may determine the size of a buffer
13211 allocated by the setvbuf function. The contents of the array at any time are
13215 The setvbuf function returns zero on success, or nonzero if an invalid value is given
13216 for mode or if the request cannot be honored.
13219 <p><small><a name="note239" href="#note239">239)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
13220 before a buffer that has automatic storage duration is deallocated upon block exit.
13223 <h4><a name="7.19.6" href="#7.19.6">7.19.6 Formatted input/output functions</a></h4>
13225 The formatted input/output functions shall behave as if there is a sequence point after the
13226 actions associated with each specifier.<sup><a href="#note240"><b>240)</b></a></sup>
13229 <p><small><a name="note240" href="#note240">240)</a> The fprintf functions perform writes to memory for the %n specifier.
13232 <h5><a name="7.19.6.1" href="#7.19.6.1">7.19.6.1 The fprintf function</a></h5>
13236 #include <a href="#7.19"><stdio.h></a>
13237 int fprintf(FILE * restrict stream,
13238 const char * restrict format, ...);</pre>
13239 <h6>Description</h6>
13241 The fprintf function writes output to the stream pointed to by stream, under control
13242 of the string pointed to by format that specifies how subsequent arguments are
13243 converted for output. If there are insufficient arguments for the format, the behavior is
13244 undefined. If the format is exhausted while arguments remain, the excess arguments are
13245 evaluated (as always) but are otherwise ignored. The fprintf function returns when
13246 the end of the format string is encountered.
13248 The format shall be a multibyte character sequence, beginning and ending in its initial
13249 shift state. The format is composed of zero or more directives: ordinary multibyte
13250 characters (not %), which are copied unchanged to the output stream; and conversion
13254 specifications, each of which results in fetching zero or more subsequent arguments,
13255 converting them, if applicable, according to the corresponding conversion specifier, and
13256 then writing the result to the output stream.
13258 Each conversion specification is introduced by the character %. After the %, the following
13259 appear in sequence:
13261 <li> Zero or more flags (in any order) that modify the meaning of the conversion
13263 <li> An optional minimum field width. If the converted value has fewer characters than the
13264 field width, it is padded with spaces (by default) on the left (or right, if the left
13265 adjustment flag, described later, has been given) to the field width. The field width
13266 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note241"><b>241)</b></a></sup>
13267 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
13268 o, u, x, and X conversions, the number of digits to appear after the decimal-point
13269 character for a, A, e, E, f, and F conversions, the maximum number of significant
13270 digits for the g and G conversions, or the maximum number of bytes to be written for
13271 s conversions. The precision takes the form of a period (.) followed either by an
13272 asterisk * (described later) or by an optional decimal integer; if only the period is
13273 specified, the precision is taken as zero. If a precision appears with any other
13274 conversion specifier, the behavior is undefined.
13275 <li> An optional length modifier that specifies the size of the argument.
13276 <li> A conversion specifier character that specifies the type of conversion to be applied.
13279 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
13280 this case, an int argument supplies the field width or precision. The arguments
13281 specifying field width, or precision, or both, shall appear (in that order) before the
13282 argument (if any) to be converted. A negative field width argument is taken as a - flag
13283 followed by a positive field width. A negative precision argument is taken as if the
13284 precision were omitted.
13286 The flag characters and their meanings are:
13287 - The result of the conversion is left-justified within the field. (It is right-justified if
13289 this flag is not specified.)</pre>
13290 + The result of a signed conversion always begins with a plus or minus sign. (It
13292 begins with a sign only when a negative value is converted if this flag is not</pre>
13299 specified.)<sup><a href="#note242"><b>242)</b></a></sup></pre>
13300 space If the first character of a signed conversion is not a sign, or if a signed conversion
13302 results in no characters, a space is prefixed to the result. If the space and + flags
13303 both appear, the space flag is ignored.</pre>
13304 # The result is converted to an ''alternative form''. For o conversion, it increases
13306 the precision, if and only if necessary, to force the first digit of the result to be a
13307 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
13308 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
13309 and G conversions, the result of converting a floating-point number always
13310 contains a decimal-point character, even if no digits follow it. (Normally, a
13311 decimal-point character appears in the result of these conversions only if a digit
13312 follows it.) For g and G conversions, trailing zeros are not removed from the
13313 result. For other conversions, the behavior is undefined.</pre>
13314 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
13317 (following any indication of sign or base) are used to pad to the field width rather
13318 than performing space padding, except when converting an infinity or NaN. If the
13319 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
13320 conversions, if a precision is specified, the 0 flag is ignored. For other
13321 conversions, the behavior is undefined.</pre>
13322 The length modifiers and their meanings are:
13323 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13325 signed char or unsigned char argument (the argument will have
13326 been promoted according to the integer promotions, but its value shall be
13327 converted to signed char or unsigned char before printing); or that
13328 a following n conversion specifier applies to a pointer to a signed char
13330 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13332 short int or unsigned short int argument (the argument will
13333 have been promoted according to the integer promotions, but its value shall
13334 be converted to short int or unsigned short int before printing);
13335 or that a following n conversion specifier applies to a pointer to a short
13336 int argument.</pre>
13337 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13339 long int or unsigned long int argument; that a following n
13340 conversion specifier applies to a pointer to a long int argument; that a</pre>
13344 following c conversion specifier applies to a wint_t argument; that a
13345 following s conversion specifier applies to a pointer to a wchar_t
13346 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
13348 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13350 long long int or unsigned long long int argument; or that a
13351 following n conversion specifier applies to a pointer to a long long int
13353 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
13355 an intmax_t or uintmax_t argument; or that a following n conversion
13356 specifier applies to a pointer to an intmax_t argument.</pre>
13357 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13359 size_t or the corresponding signed integer type argument; or that a
13360 following n conversion specifier applies to a pointer to a signed integer type
13361 corresponding to size_t argument.</pre>
13362 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13364 ptrdiff_t or the corresponding unsigned integer type argument; or that a
13365 following n conversion specifier applies to a pointer to a ptrdiff_t
13367 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13369 applies to a long double argument.</pre>
13370 If a length modifier appears with any conversion specifier other than as specified above,
13371 the behavior is undefined.
13373 The conversion specifiers and their meanings are:
13374 d,i The int argument is converted to signed decimal in the style [-]dddd. The
13376 precision specifies the minimum number of digits to appear; if the value
13377 being converted can be represented in fewer digits, it is expanded with
13378 leading zeros. The default precision is 1. The result of converting a zero
13379 value with a precision of zero is no characters.</pre>
13380 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
13383 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
13384 letters abcdef are used for x conversion and the letters ABCDEF for X
13385 conversion. The precision specifies the minimum number of digits to appear;
13386 if the value being converted can be represented in fewer digits, it is expanded
13387 with leading zeros. The default precision is 1. The result of converting a
13388 zero value with a precision of zero is no characters.</pre>
13389 f,F A double argument representing a floating-point number is converted to
13391 decimal notation in the style [-]ddd.ddd, where the number of digits after
13392 the decimal-point character is equal to the precision specification. If the
13393 precision is missing, it is taken as 6; if the precision is zero and the # flag is
13394 not specified, no decimal-point character appears. If a decimal-point
13395 character appears, at least one digit appears before it. The value is rounded to
13396 the appropriate number of digits.
13397 A double argument representing an infinity is converted in one of the styles
13398 [-]inf or [-]infinity -- which style is implementation-defined. A
13399 double argument representing a NaN is converted in one of the styles
13400 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
13401 any n-char-sequence, is implementation-defined. The F conversion specifier
13402 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
13403 respectively.<sup><a href="#note243"><b>243)</b></a></sup></pre>
13404 e,E A double argument representing a floating-point number is converted in the
13406 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
13407 argument is nonzero) before the decimal-point character and the number of
13408 digits after it is equal to the precision; if the precision is missing, it is taken as
13409 6; if the precision is zero and the # flag is not specified, no decimal-point
13410 character appears. The value is rounded to the appropriate number of digits.
13411 The E conversion specifier produces a number with E instead of e
13412 introducing the exponent. The exponent always contains at least two digits,
13413 and only as many more digits as necessary to represent the exponent. If the
13414 value is zero, the exponent is zero.
13415 A double argument representing an infinity or NaN is converted in the style
13416 of an f or F conversion specifier.</pre>
13417 g,G A double argument representing a floating-point number is converted in
13419 style f or e (or in style F or E in the case of a G conversion specifier),
13420 depending on the value converted and the precision. Let P equal the
13421 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
13422 Then, if a conversion with style E would have an exponent of X :
13423 -- if P > X >= -4, the conversion is with style f (or F) and precision
13425 -- otherwise, the conversion is with style e (or E) and precision P - 1.
13426 Finally, unless the # flag is used, any trailing zeros are removed from the</pre>
13430 fractional portion of the result and the decimal-point character is removed if
13431 there is no fractional portion remaining.
13432 A double argument representing an infinity or NaN is converted in the style
13433 of an f or F conversion specifier.</pre>
13434 a,A A double argument representing a floating-point number is converted in the
13436 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
13437 nonzero if the argument is a normalized floating-point number and is
13438 otherwise unspecified) before the decimal-point character<sup><a href="#note244"><b>244)</b></a></sup> and the number
13439 of hexadecimal digits after it is equal to the precision; if the precision is
13440 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
13441 an exact representation of the value; if the precision is missing and
13442 FLT_RADIX is not a power of 2, then the precision is sufficient to
13443 distinguish<sup><a href="#note245"><b>245)</b></a></sup> values of type double, except that trailing zeros may be
13444 omitted; if the precision is zero and the # flag is not specified, no decimal-
13445 point character appears. The letters abcdef are used for a conversion and
13446 the letters ABCDEF for A conversion. The A conversion specifier produces a
13447 number with X and P instead of x and p. The exponent always contains at
13448 least one digit, and only as many more digits as necessary to represent the
13449 decimal exponent of 2. If the value is zero, the exponent is zero.
13450 A double argument representing an infinity or NaN is converted in the style
13451 of an f or F conversion specifier.</pre>
13452 c If no l length modifier is present, the int argument is converted to an
13454 unsigned char, and the resulting character is written.
13455 If an l length modifier is present, the wint_t argument is converted as if by
13456 an ls conversion specification with no precision and an argument that points
13457 to the initial element of a two-element array of wchar_t, the first element
13458 containing the wint_t argument to the lc conversion specification and the
13459 second a null wide character.</pre>
13460 s If no l length modifier is present, the argument shall be a pointer to the initial
13462 element of an array of character type.<sup><a href="#note246"><b>246)</b></a></sup> Characters from the array are</pre>
13467 written up to (but not including) the terminating null character. If the
13468 precision is specified, no more than that many bytes are written. If the
13469 precision is not specified or is greater than the size of the array, the array shall
13470 contain a null character.
13471 If an l length modifier is present, the argument shall be a pointer to the initial
13472 element of an array of wchar_t type. Wide characters from the array are
13473 converted to multibyte characters (each as if by a call to the wcrtomb
13474 function, with the conversion state described by an mbstate_t object
13475 initialized to zero before the first wide character is converted) up to and
13476 including a terminating null wide character. The resulting multibyte
13477 characters are written up to (but not including) the terminating null character
13478 (byte). If no precision is specified, the array shall contain a null wide
13479 character. If a precision is specified, no more than that many bytes are
13480 written (including shift sequences, if any), and the array shall contain a null
13481 wide character if, to equal the multibyte character sequence length given by
13482 the precision, the function would need to access a wide character one past the
13483 end of the array. In no case is a partial multibyte character written.<sup><a href="#note247"><b>247)</b></a></sup></pre>
13484 p The argument shall be a pointer to void. The value of the pointer is
13486 converted to a sequence of printing characters, in an implementation-defined
13488 n The argument shall be a pointer to signed integer into which is written the
13490 number of characters written to the output stream so far by this call to
13491 fprintf. No argument is converted, but one is consumed. If the conversion
13492 specification includes any flags, a field width, or a precision, the behavior is
13494 % A % character is written. No argument is converted. The complete
13497 conversion specification shall be %%.</pre>
13498 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note248"><b>248)</b></a></sup> If any argument is
13499 not the correct type for the corresponding conversion specification, the behavior is
13502 In no case does a nonexistent or small field width cause truncation of a field; if the result
13503 of a conversion is wider than the field width, the field is expanded to contain the
13511 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
13512 to a hexadecimal floating number with the given precision.
13513 <h6> Recommended practice</h6>
13515 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
13516 representable in the given precision, the result should be one of the two adjacent numbers
13517 in hexadecimal floating style with the given precision, with the extra stipulation that the
13518 error should have a correct sign for the current rounding direction.
13520 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
13521 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note249"><b>249)</b></a></sup> If the number of
13522 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
13523 representable with DECIMAL_DIG digits, then the result should be an exact
13524 representation with trailing zeros. Otherwise, the source value is bounded by two
13525 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
13526 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
13527 the error should have a correct sign for the current rounding direction.
13530 The fprintf function returns the number of characters transmitted, or a negative value
13531 if an output or encoding error occurred.
13532 Environmental limits
13534 The number of characters that can be produced by any single conversion shall be at least
13537 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
13540 #include <a href="#7.12"><math.h></a>
13541 #include <a href="#7.19"><stdio.h></a>
13543 char *weekday, *month; // pointers to strings
13544 int day, hour, min;
13545 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
13546 weekday, month, day, hour, min);
13547 fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));</pre>
13550 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
13551 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13552 the first of which is denoted here by a and the second by an uppercase letter.
13559 Given the following wide string with length seven,
13561 static wchar_t wstr[] = L" X Yabc Z W";</pre>
13564 fprintf(stdout, "|1234567890123|\n");
13565 fprintf(stdout, "|%13ls|\n", wstr);
13566 fprintf(stdout, "|%-13.9ls|\n", wstr);
13567 fprintf(stdout, "|%13.10ls|\n", wstr);
13568 fprintf(stdout, "|%13.11ls|\n", wstr);
13569 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
13570 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);</pre>
13571 will print the following seven lines:
13581 <p><b> Forward references</b>: conversion state (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13584 <p><small><a name="note241" href="#note241">241)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
13586 <p><small><a name="note242" href="#note242">242)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
13587 include a minus sign.
13589 <p><small><a name="note243" href="#note243">243)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
13590 the # and 0 flag characters have no effect.
13592 <p><small><a name="note244" href="#note244">244)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
13593 that subsequent digits align to nibble (4-bit) boundaries.
13595 <p><small><a name="note245" href="#note245">245)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
13596 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
13597 might suffice depending on the implementation's scheme for determining the digit to the left of the
13598 decimal-point character.
13600 <p><small><a name="note246" href="#note246">246)</a> No special provisions are made for multibyte characters.
13602 <p><small><a name="note247" href="#note247">247)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
13604 <p><small><a name="note248" href="#note248">248)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13606 <p><small><a name="note249" href="#note249">249)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
13607 given format specifier. The number of significant digits is determined by the format specifier, and in
13608 the case of fixed-point conversion by the source value as well.
13611 <h5><a name="7.19.6.2" href="#7.19.6.2">7.19.6.2 The fscanf function</a></h5>
13615 #include <a href="#7.19"><stdio.h></a>
13616 int fscanf(FILE * restrict stream,
13617 const char * restrict format, ...);</pre>
13618 <h6>Description</h6>
13620 The fscanf function reads input from the stream pointed to by stream, under control
13621 of the string pointed to by format that specifies the admissible input sequences and how
13622 they are to be converted for assignment, using subsequent arguments as pointers to the
13623 objects to receive the converted input. If there are insufficient arguments for the format,
13624 the behavior is undefined. If the format is exhausted while arguments remain, the excess
13625 arguments are evaluated (as always) but are otherwise ignored.
13627 The format shall be a multibyte character sequence, beginning and ending in its initial
13628 shift state. The format is composed of zero or more directives: one or more white-space
13629 characters, an ordinary multibyte character (neither % nor a white-space character), or a
13630 conversion specification. Each conversion specification is introduced by the character %.
13631 After the %, the following appear in sequence:
13633 <li> An optional assignment-suppressing character *.
13634 <li> An optional decimal integer greater than zero that specifies the maximum field width
13637 <li> An optional length modifier that specifies the size of the receiving object.
13638 <li> A conversion specifier character that specifies the type of conversion to be applied.
13641 The fscanf function executes each directive of the format in turn. If a directive fails, as
13642 detailed below, the function returns. Failures are described as input failures (due to the
13643 occurrence of an encoding error or the unavailability of input characters), or matching
13644 failures (due to inappropriate input).
13646 A directive composed of white-space character(s) is executed by reading input up to the
13647 first non-white-space character (which remains unread), or until no more characters can
13650 A directive that is an ordinary multibyte character is executed by reading the next
13651 characters of the stream. If any of those characters differ from the ones composing the
13652 directive, the directive fails and the differing and subsequent characters remain unread.
13653 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
13654 read, the directive fails.
13656 A directive that is a conversion specification defines a set of matching input sequences, as
13657 described below for each specifier. A conversion specification is executed in the
13660 Input white-space characters (as specified by the isspace function) are skipped, unless
13661 the specification includes a [, c, or n specifier.<sup><a href="#note250"><b>250)</b></a></sup>
13663 An input item is read from the stream, unless the specification includes an n specifier. An
13664 input item is defined as the longest sequence of input characters which does not exceed
13665 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note251"><b>251)</b></a></sup>
13666 The first character, if any, after the input item remains unread. If the length of the input
13667 item is zero, the execution of the directive fails; this condition is a matching failure unless
13668 end-of-file, an encoding error, or a read error prevented input from the stream, in which
13669 case it is an input failure.
13671 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
13672 count of input characters) is converted to a type appropriate to the conversion specifier. If
13673 the input item is not a matching sequence, the execution of the directive fails: this
13674 condition is a matching failure. Unless assignment suppression was indicated by a *, the
13675 result of the conversion is placed in the object pointed to by the first argument following
13676 the format argument that has not already received a conversion result. If this object
13677 does not have an appropriate type, or if the result of the conversion cannot be represented
13681 in the object, the behavior is undefined.
13683 The length modifiers and their meanings are:
13684 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13686 to an argument with type pointer to signed char or unsigned char.</pre>
13687 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13689 to an argument with type pointer to short int or unsigned short
13691 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13693 to an argument with type pointer to long int or unsigned long
13694 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
13695 an argument with type pointer to double; or that a following c, s, or [
13696 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
13697 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13699 to an argument with type pointer to long long int or unsigned
13700 long long int.</pre>
13701 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13703 to an argument with type pointer to intmax_t or uintmax_t.</pre>
13704 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13706 to an argument with type pointer to size_t or the corresponding signed
13707 integer type.</pre>
13708 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13710 to an argument with type pointer to ptrdiff_t or the corresponding
13711 unsigned integer type.</pre>
13712 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13714 applies to an argument with type pointer to long double.</pre>
13715 If a length modifier appears with any conversion specifier other than as specified above,
13716 the behavior is undefined.
13718 The conversion specifiers and their meanings are:
13719 d Matches an optionally signed decimal integer, whose format is the same as
13721 expected for the subject sequence of the strtol function with the value 10
13722 for the base argument. The corresponding argument shall be a pointer to
13723 signed integer.</pre>
13724 i Matches an optionally signed integer, whose format is the same as expected
13727 for the subject sequence of the strtol function with the value 0 for the
13728 base argument. The corresponding argument shall be a pointer to signed
13730 o Matches an optionally signed octal integer, whose format is the same as
13732 expected for the subject sequence of the strtoul function with the value 8
13733 for the base argument. The corresponding argument shall be a pointer to
13734 unsigned integer.</pre>
13735 u Matches an optionally signed decimal integer, whose format is the same as
13737 expected for the subject sequence of the strtoul function with the value 10
13738 for the base argument. The corresponding argument shall be a pointer to
13739 unsigned integer.</pre>
13740 x Matches an optionally signed hexadecimal integer, whose format is the same
13742 as expected for the subject sequence of the strtoul function with the value
13743 16 for the base argument. The corresponding argument shall be a pointer to
13744 unsigned integer.</pre>
13745 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
13747 format is the same as expected for the subject sequence of the strtod
13748 function. The corresponding argument shall be a pointer to floating.</pre>
13749 c Matches a sequence of characters of exactly the number specified by the field
13751 width (1 if no field width is present in the directive).<sup><a href="#note252"><b>252)</b></a></sup>
13752 If no l length modifier is present, the corresponding argument shall be a
13753 pointer to the initial element of a character array large enough to accept the
13754 sequence. No null character is added.
13755 If an l length modifier is present, the input shall be a sequence of multibyte
13756 characters that begins in the initial shift state. Each multibyte character in the
13757 sequence is converted to a wide character as if by a call to the mbrtowc
13758 function, with the conversion state described by an mbstate_t object
13759 initialized to zero before the first multibyte character is converted. The
13760 corresponding argument shall be a pointer to the initial element of an array of
13761 wchar_t large enough to accept the resulting sequence of wide characters.
13762 No null wide character is added.</pre>
13763 s Matches a sequence of non-white-space characters.252)
13765 If no l length modifier is present, the corresponding argument shall be a
13766 pointer to the initial element of a character array large enough to accept the
13767 sequence and a terminating null character, which will be added automatically.
13768 If an l length modifier is present, the input shall be a sequence of multibyte</pre>
13773 characters that begins in the initial shift state. Each multibyte character is
13774 converted to a wide character as if by a call to the mbrtowc function, with
13775 the conversion state described by an mbstate_t object initialized to zero
13776 before the first multibyte character is converted. The corresponding argument
13777 shall be a pointer to the initial element of an array of wchar_t large enough
13778 to accept the sequence and the terminating null wide character, which will be
13779 added automatically.</pre>
13780 [ Matches a nonempty sequence of characters from a set of expected characters
13783 If no l length modifier is present, the corresponding argument shall be a
13784 pointer to the initial element of a character array large enough to accept the
13785 sequence and a terminating null character, which will be added automatically.
13786 If an l length modifier is present, the input shall be a sequence of multibyte
13787 characters that begins in the initial shift state. Each multibyte character is
13788 converted to a wide character as if by a call to the mbrtowc function, with
13789 the conversion state described by an mbstate_t object initialized to zero
13790 before the first multibyte character is converted. The corresponding argument
13791 shall be a pointer to the initial element of an array of wchar_t large enough
13792 to accept the sequence and the terminating null wide character, which will be
13793 added automatically.
13794 The conversion specifier includes all subsequent characters in the format
13795 string, up to and including the matching right bracket (]). The characters
13796 between the brackets (the scanlist) compose the scanset, unless the character
13797 after the left bracket is a circumflex (^), in which case the scanset contains all
13798 characters that do not appear in the scanlist between the circumflex and the
13799 right bracket. If the conversion specifier begins with [] or [^], the right
13800 bracket character is in the scanlist and the next following right bracket
13801 character is the matching right bracket that ends the specification; otherwise
13802 the first following right bracket character is the one that ends the
13803 specification. If a - character is in the scanlist and is not the first, nor the
13804 second where the first character is a ^, nor the last character, the behavior is
13805 implementation-defined.</pre>
13806 p Matches an implementation-defined set of sequences, which should be the
13809 same as the set of sequences that may be produced by the %p conversion of
13810 the fprintf function. The corresponding argument shall be a pointer to a
13811 pointer to void. The input item is converted to a pointer value in an
13812 implementation-defined manner. If the input item is a value converted earlier
13813 during the same program execution, the pointer that results shall compare
13814 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
13815 n No input is consumed. The corresponding argument shall be a pointer to
13817 signed integer into which is to be written the number of characters read from
13818 the input stream so far by this call to the fscanf function. Execution of a
13819 %n directive does not increment the assignment count returned at the
13820 completion of execution of the fscanf function. No argument is converted,
13821 but one is consumed. If the conversion specification includes an assignment-
13822 suppressing character or a field width, the behavior is undefined.</pre>
13823 % Matches a single % character; no conversion or assignment occurs. The
13826 complete conversion specification shall be %%.</pre>
13827 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note253"><b>253)</b></a></sup>
13829 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
13830 respectively, a, e, f, g, and x.
13832 Trailing white space (including new-line characters) is left unread unless matched by a
13833 directive. The success of literal matches and suppressed assignments is not directly
13834 determinable other than via the %n directive.
13837 The fscanf function returns the value of the macro EOF if an input failure occurs
13838 before any conversion. Otherwise, the function returns the number of input items
13839 assigned, which can be fewer than provided for, or even zero, in the event of an early
13842 EXAMPLE 1 The call:
13844 #include <a href="#7.19"><stdio.h></a>
13846 int n, i; float x; char name[50];
13847 n = fscanf(stdin, "%d%f%s", &i, &x, name);</pre>
13848 with the input line:
13850 25 54.32E-1 thompson</pre>
13851 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
13855 EXAMPLE 2 The call:
13857 #include <a href="#7.19"><stdio.h></a>
13859 int i; float x; char name[50];
13860 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);</pre>
13867 56789 0123 56a72</pre>
13868 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
13869 sequence 56\0. The next character read from the input stream will be a.
13872 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
13875 #include <a href="#7.19"><stdio.h></a>
13877 int count; float quant; char units[21], item[21];
13879 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
13880 fscanf(stdin,"%*[^\n]");
13881 } while (!feof(stdin) && !ferror(stdin));</pre>
13882 If the stdin stream contains the following lines:
13885 -12.8degrees Celsius
13889 100ergs of energy</pre>
13890 the execution of the above example will be analogous to the following assignments:
13892 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
13894 quant = -12.8; strcpy(units, "degrees");
13895 count = 2; // "C" fails to match "o"
13896 count = 0; // "l" fails to match "%f"
13897 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
13899 count = 0; // "100e" fails to match "%f"
13905 #include <a href="#7.19"><stdio.h></a>
13907 int d1, d2, n1, n2, i;
13908 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);</pre>
13909 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13910 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
13913 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13914 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13915 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13916 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13917 entry into the alternate shift state.
13922 #include <a href="#7.19"><stdio.h></a>
13925 fscanf(stdin, "a%s", str);</pre>
13926 with the input line:
13928 a(uparrow) X Y(downarrow) bc</pre>
13929 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13930 characters, in the more general case) appears to be a single-byte white-space character.
13932 In contrast, after the call:
13934 #include <a href="#7.19"><stdio.h></a>
13935 #include <a href="#7.17"><stddef.h></a>
13938 fscanf(stdin, "a%ls", wstr);</pre>
13939 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13940 terminating null wide character.
13944 #include <a href="#7.19"><stdio.h></a>
13945 #include <a href="#7.17"><stddef.h></a>
13948 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);</pre>
13949 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13952 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13953 character Y, after the call:
13955 #include <a href="#7.19"><stdio.h></a>
13956 #include <a href="#7.17"><stddef.h></a>
13959 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);</pre>
13960 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13961 multibyte character.
13963 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>), the
13964 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.20.1.4">7.20.1.4</a>), conversion state
13965 (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13969 <p><small><a name="note250" href="#note250">250)</a> These white-space characters are not counted against a specified field width.
13971 <p><small><a name="note251" href="#note251">251)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
13972 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
13974 <p><small><a name="note252" href="#note252">252)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
13975 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
13976 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
13978 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13981 <h5><a name="7.19.6.3" href="#7.19.6.3">7.19.6.3 The printf function</a></h5>
13985 #include <a href="#7.19"><stdio.h></a>
13986 int printf(const char * restrict format, ...);</pre>
13987 <h6>Description</h6>
13989 The printf function is equivalent to fprintf with the argument stdout interposed
13990 before the arguments to printf.
13993 The printf function returns the number of characters transmitted, or a negative value if
13994 an output or encoding error occurred.
13996 <h5><a name="7.19.6.4" href="#7.19.6.4">7.19.6.4 The scanf function</a></h5>
14000 #include <a href="#7.19"><stdio.h></a>
14001 int scanf(const char * restrict format, ...);</pre>
14002 <h6>Description</h6>
14004 The scanf function is equivalent to fscanf with the argument stdin interposed
14005 before the arguments to scanf.
14008 The scanf function returns the value of the macro EOF if an input failure occurs before
14009 any conversion. Otherwise, the scanf function returns the number of input items
14010 assigned, which can be fewer than provided for, or even zero, in the event of an early
14013 <h5><a name="7.19.6.5" href="#7.19.6.5">7.19.6.5 The snprintf function</a></h5>
14017 #include <a href="#7.19"><stdio.h></a>
14018 int snprintf(char * restrict s, size_t n,
14019 const char * restrict format, ...);</pre>
14020 <h6>Description</h6>
14022 The snprintf function is equivalent to fprintf, except that the output is written into
14023 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
14024 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
14025 discarded rather than being written to the array, and a null character is written at the end
14026 of the characters actually written into the array. If copying takes place between objects
14027 that overlap, the behavior is undefined.
14031 The snprintf function returns the number of characters that would have been written
14032 had n been sufficiently large, not counting the terminating null character, or a negative
14033 value if an encoding error occurred. Thus, the null-terminated output has been
14034 completely written if and only if the returned value is nonnegative and less than n.
14036 <h5><a name="7.19.6.6" href="#7.19.6.6">7.19.6.6 The sprintf function</a></h5>
14040 #include <a href="#7.19"><stdio.h></a>
14041 int sprintf(char * restrict s,
14042 const char * restrict format, ...);</pre>
14043 <h6>Description</h6>
14045 The sprintf function is equivalent to fprintf, except that the output is written into
14046 an array (specified by the argument s) rather than to a stream. A null character is written
14047 at the end of the characters written; it is not counted as part of the returned value. If
14048 copying takes place between objects that overlap, the behavior is undefined.
14051 The sprintf function returns the number of characters written in the array, not
14052 counting the terminating null character, or a negative value if an encoding error occurred.
14054 <h5><a name="7.19.6.7" href="#7.19.6.7">7.19.6.7 The sscanf function</a></h5>
14058 #include <a href="#7.19"><stdio.h></a>
14059 int sscanf(const char * restrict s,
14060 const char * restrict format, ...);</pre>
14061 <h6>Description</h6>
14063 The sscanf function is equivalent to fscanf, except that input is obtained from a
14064 string (specified by the argument s) rather than from a stream. Reaching the end of the
14065 string is equivalent to encountering end-of-file for the fscanf function. If copying
14066 takes place between objects that overlap, the behavior is undefined.
14069 The sscanf function returns the value of the macro EOF if an input failure occurs
14070 before any conversion. Otherwise, the sscanf function returns the number of input
14071 items assigned, which can be fewer than provided for, or even zero, in the event of an
14072 early matching failure.
14075 <h5><a name="7.19.6.8" href="#7.19.6.8">7.19.6.8 The vfprintf function</a></h5>
14079 #include <a href="#7.15"><stdarg.h></a>
14080 #include <a href="#7.19"><stdio.h></a>
14081 int vfprintf(FILE * restrict stream,
14082 const char * restrict format,
14083 va_list arg);</pre>
14084 <h6>Description</h6>
14086 The vfprintf function is equivalent to fprintf, with the variable argument list
14087 replaced by arg, which shall have been initialized by the va_start macro (and
14088 possibly subsequent va_arg calls). The vfprintf function does not invoke the
14089 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup>
14092 The vfprintf function returns the number of characters transmitted, or a negative
14093 value if an output or encoding error occurred.
14095 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
14097 #include <a href="#7.15"><stdarg.h></a>
14098 #include <a href="#7.19"><stdio.h></a>
14099 void error(char *function_name, char *format, ...)
14102 va_start(args, format);
14103 // print out name of function causing error
14104 fprintf(stderr, "ERROR in %s: ", function_name);
14105 // print out remainder of message
14106 vfprintf(stderr, format, args);
14116 <p><small><a name="note254" href="#note254">254)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
14117 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
14120 <h5><a name="7.19.6.9" href="#7.19.6.9">7.19.6.9 The vfscanf function</a></h5>
14124 #include <a href="#7.15"><stdarg.h></a>
14125 #include <a href="#7.19"><stdio.h></a>
14126 int vfscanf(FILE * restrict stream,
14127 const char * restrict format,
14128 va_list arg);</pre>
14129 <h6>Description</h6>
14131 The vfscanf function is equivalent to fscanf, with the variable argument list
14132 replaced by arg, which shall have been initialized by the va_start macro (and
14133 possibly subsequent va_arg calls). The vfscanf function does not invoke the
14137 The vfscanf function returns the value of the macro EOF if an input failure occurs
14138 before any conversion. Otherwise, the vfscanf function returns the number of input
14139 items assigned, which can be fewer than provided for, or even zero, in the event of an
14140 early matching failure.
14142 <h5><a name="7.19.6.10" href="#7.19.6.10">7.19.6.10 The vprintf function</a></h5>
14146 #include <a href="#7.15"><stdarg.h></a>
14147 #include <a href="#7.19"><stdio.h></a>
14148 int vprintf(const char * restrict format,
14149 va_list arg);</pre>
14150 <h6>Description</h6>
14152 The vprintf function is equivalent to printf, with the variable argument list
14153 replaced by arg, which shall have been initialized by the va_start macro (and
14154 possibly subsequent va_arg calls). The vprintf function does not invoke the
14158 The vprintf function returns the number of characters transmitted, or a negative value
14159 if an output or encoding error occurred.
14162 <h5><a name="7.19.6.11" href="#7.19.6.11">7.19.6.11 The vscanf function</a></h5>
14166 #include <a href="#7.15"><stdarg.h></a>
14167 #include <a href="#7.19"><stdio.h></a>
14168 int vscanf(const char * restrict format,
14169 va_list arg);</pre>
14170 <h6>Description</h6>
14172 The vscanf function is equivalent to scanf, with the variable argument list replaced
14173 by arg, which shall have been initialized by the va_start macro (and possibly
14174 subsequent va_arg calls). The vscanf function does not invoke the va_end
14178 The vscanf function returns the value of the macro EOF if an input failure occurs
14179 before any conversion. Otherwise, the vscanf function returns the number of input
14180 items assigned, which can be fewer than provided for, or even zero, in the event of an
14181 early matching failure.
14183 <h5><a name="7.19.6.12" href="#7.19.6.12">7.19.6.12 The vsnprintf function</a></h5>
14187 #include <a href="#7.15"><stdarg.h></a>
14188 #include <a href="#7.19"><stdio.h></a>
14189 int vsnprintf(char * restrict s, size_t n,
14190 const char * restrict format,
14191 va_list arg);</pre>
14192 <h6>Description</h6>
14194 The vsnprintf function is equivalent to snprintf, with the variable argument list
14195 replaced by arg, which shall have been initialized by the va_start macro (and
14196 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
14197 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14201 The vsnprintf function returns the number of characters that would have been written
14202 had n been sufficiently large, not counting the terminating null character, or a negative
14203 value if an encoding error occurred. Thus, the null-terminated output has been
14204 completely written if and only if the returned value is nonnegative and less than n.
14207 <h5><a name="7.19.6.13" href="#7.19.6.13">7.19.6.13 The vsprintf function</a></h5>
14211 #include <a href="#7.15"><stdarg.h></a>
14212 #include <a href="#7.19"><stdio.h></a>
14213 int vsprintf(char * restrict s,
14214 const char * restrict format,
14215 va_list arg);</pre>
14216 <h6>Description</h6>
14218 The vsprintf function is equivalent to sprintf, with the variable argument list
14219 replaced by arg, which shall have been initialized by the va_start macro (and
14220 possibly subsequent va_arg calls). The vsprintf function does not invoke the
14221 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14225 The vsprintf function returns the number of characters written in the array, not
14226 counting the terminating null character, or a negative value if an encoding error occurred.
14228 <h5><a name="7.19.6.14" href="#7.19.6.14">7.19.6.14 The vsscanf function</a></h5>
14232 #include <a href="#7.15"><stdarg.h></a>
14233 #include <a href="#7.19"><stdio.h></a>
14234 int vsscanf(const char * restrict s,
14235 const char * restrict format,
14236 va_list arg);</pre>
14237 <h6>Description</h6>
14239 The vsscanf function is equivalent to sscanf, with the variable argument list
14240 replaced by arg, which shall have been initialized by the va_start macro (and
14241 possibly subsequent va_arg calls). The vsscanf function does not invoke the
14245 The vsscanf function returns the value of the macro EOF if an input failure occurs
14246 before any conversion. Otherwise, the vsscanf function returns the number of input
14247 items assigned, which can be fewer than provided for, or even zero, in the event of an
14248 early matching failure.
14251 <h4><a name="7.19.7" href="#7.19.7">7.19.7 Character input/output functions</a></h4>
14253 <h5><a name="7.19.7.1" href="#7.19.7.1">7.19.7.1 The fgetc function</a></h5>
14257 #include <a href="#7.19"><stdio.h></a>
14258 int fgetc(FILE *stream);</pre>
14259 <h6>Description</h6>
14261 If the end-of-file indicator for the input stream pointed to by stream is not set and a
14262 next character is present, the fgetc function obtains that character as an unsigned
14263 char converted to an int and advances the associated file position indicator for the
14264 stream (if defined).
14267 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
14268 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
14269 fgetc function returns the next character from the input stream pointed to by stream.
14270 If a read error occurs, the error indicator for the stream is set and the fgetc function
14271 returns EOF.<sup><a href="#note255"><b>255)</b></a></sup>
14274 <p><small><a name="note255" href="#note255">255)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
14277 <h5><a name="7.19.7.2" href="#7.19.7.2">7.19.7.2 The fgets function</a></h5>
14281 #include <a href="#7.19"><stdio.h></a>
14282 char *fgets(char * restrict s, int n,
14283 FILE * restrict stream);</pre>
14284 <h6>Description</h6>
14286 The fgets function reads at most one less than the number of characters specified by n
14287 from the stream pointed to by stream into the array pointed to by s. No additional
14288 characters are read after a new-line character (which is retained) or after end-of-file. A
14289 null character is written immediately after the last character read into the array.
14292 The fgets function returns s if successful. If end-of-file is encountered and no
14293 characters have been read into the array, the contents of the array remain unchanged and a
14294 null pointer is returned. If a read error occurs during the operation, the array contents are
14295 indeterminate and a null pointer is returned.
14302 <h5><a name="7.19.7.3" href="#7.19.7.3">7.19.7.3 The fputc function</a></h5>
14306 #include <a href="#7.19"><stdio.h></a>
14307 int fputc(int c, FILE *stream);</pre>
14308 <h6>Description</h6>
14310 The fputc function writes the character specified by c (converted to an unsigned
14311 char) to the output stream pointed to by stream, at the position indicated by the
14312 associated file position indicator for the stream (if defined), and advances the indicator
14313 appropriately. If the file cannot support positioning requests, or if the stream was opened
14314 with append mode, the character is appended to the output stream.
14317 The fputc function returns the character written. If a write error occurs, the error
14318 indicator for the stream is set and fputc returns EOF.
14320 <h5><a name="7.19.7.4" href="#7.19.7.4">7.19.7.4 The fputs function</a></h5>
14324 #include <a href="#7.19"><stdio.h></a>
14325 int fputs(const char * restrict s,
14326 FILE * restrict stream);</pre>
14327 <h6>Description</h6>
14329 The fputs function writes the string pointed to by s to the stream pointed to by
14330 stream. The terminating null character is not written.
14333 The fputs function returns EOF if a write error occurs; otherwise it returns a
14336 <h5><a name="7.19.7.5" href="#7.19.7.5">7.19.7.5 The getc function</a></h5>
14340 #include <a href="#7.19"><stdio.h></a>
14341 int getc(FILE *stream);</pre>
14342 <h6>Description</h6>
14344 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
14345 may evaluate stream more than once, so the argument should never be an expression
14350 The getc function returns the next character from the input stream pointed to by
14351 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14352 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
14355 <h5><a name="7.19.7.6" href="#7.19.7.6">7.19.7.6 The getchar function</a></h5>
14359 #include <a href="#7.19"><stdio.h></a>
14360 int getchar(void);</pre>
14361 <h6>Description</h6>
14363 The getchar function is equivalent to getc with the argument stdin.
14366 The getchar function returns the next character from the input stream pointed to by
14367 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14368 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
14369 getchar returns EOF.
14371 <h5><a name="7.19.7.7" href="#7.19.7.7">7.19.7.7 The gets function</a></h5>
14375 #include <a href="#7.19"><stdio.h></a>
14376 char *gets(char *s);</pre>
14377 <h6>Description</h6>
14379 The gets function reads characters from the input stream pointed to by stdin, into the
14380 array pointed to by s, until end-of-file is encountered or a new-line character is read.
14381 Any new-line character is discarded, and a null character is written immediately after the
14382 last character read into the array.
14385 The gets function returns s if successful. If end-of-file is encountered and no
14386 characters have been read into the array, the contents of the array remain unchanged and a
14387 null pointer is returned. If a read error occurs during the operation, the array contents are
14388 indeterminate and a null pointer is returned.
14389 <p><b> Forward references</b>: future library directions (<a href="#7.26.9">7.26.9</a>).
14392 <h5><a name="7.19.7.8" href="#7.19.7.8">7.19.7.8 The putc function</a></h5>
14396 #include <a href="#7.19"><stdio.h></a>
14397 int putc(int c, FILE *stream);</pre>
14398 <h6>Description</h6>
14400 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
14401 may evaluate stream more than once, so that argument should never be an expression
14405 The putc function returns the character written. If a write error occurs, the error
14406 indicator for the stream is set and putc returns EOF.
14408 <h5><a name="7.19.7.9" href="#7.19.7.9">7.19.7.9 The putchar function</a></h5>
14412 #include <a href="#7.19"><stdio.h></a>
14413 int putchar(int c);</pre>
14414 <h6>Description</h6>
14416 The putchar function is equivalent to putc with the second argument stdout.
14419 The putchar function returns the character written. If a write error occurs, the error
14420 indicator for the stream is set and putchar returns EOF.
14422 <h5><a name="7.19.7.10" href="#7.19.7.10">7.19.7.10 The puts function</a></h5>
14426 #include <a href="#7.19"><stdio.h></a>
14427 int puts(const char *s);</pre>
14428 <h6>Description</h6>
14430 The puts function writes the string pointed to by s to the stream pointed to by stdout,
14431 and appends a new-line character to the output. The terminating null character is not
14435 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
14439 <h5><a name="7.19.7.11" href="#7.19.7.11">7.19.7.11 The ungetc function</a></h5>
14443 #include <a href="#7.19"><stdio.h></a>
14444 int ungetc(int c, FILE *stream);</pre>
14445 <h6>Description</h6>
14447 The ungetc function pushes the character specified by c (converted to an unsigned
14448 char) back onto the input stream pointed to by stream. Pushed-back characters will be
14449 returned by subsequent reads on that stream in the reverse order of their pushing. A
14450 successful intervening call (with the stream pointed to by stream) to a file positioning
14451 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
14452 stream. The external storage corresponding to the stream is unchanged.
14454 One character of pushback is guaranteed. If the ungetc function is called too many
14455 times on the same stream without an intervening read or file positioning operation on that
14456 stream, the operation may fail.
14458 If the value of c equals that of the macro EOF, the operation fails and the input stream is
14461 A successful call to the ungetc function clears the end-of-file indicator for the stream.
14462 The value of the file position indicator for the stream after reading or discarding all
14463 pushed-back characters shall be the same as it was before the characters were pushed
14464 back. For a text stream, the value of its file position indicator after a successful call to the
14465 ungetc function is unspecified until all pushed-back characters are read or discarded.
14466 For a binary stream, its file position indicator is decremented by each successful call to
14467 the ungetc function; if its value was zero before a call, it is indeterminate after the
14468 call.<sup><a href="#note256"><b>256)</b></a></sup>
14471 The ungetc function returns the character pushed back after conversion, or EOF if the
14473 <p><b> Forward references</b>: file positioning functions (<a href="#7.19.9">7.19.9</a>).
14481 <p><small><a name="note256" href="#note256">256)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14484 <h4><a name="7.19.8" href="#7.19.8">7.19.8 Direct input/output functions</a></h4>
14486 <h5><a name="7.19.8.1" href="#7.19.8.1">7.19.8.1 The fread function</a></h5>
14490 #include <a href="#7.19"><stdio.h></a>
14491 size_t fread(void * restrict ptr,
14492 size_t size, size_t nmemb,
14493 FILE * restrict stream);</pre>
14494 <h6>Description</h6>
14496 The fread function reads, into the array pointed to by ptr, up to nmemb elements
14497 whose size is specified by size, from the stream pointed to by stream. For each
14498 object, size calls are made to the fgetc function and the results stored, in the order
14499 read, in an array of unsigned char exactly overlaying the object. The file position
14500 indicator for the stream (if defined) is advanced by the number of characters successfully
14501 read. If an error occurs, the resulting value of the file position indicator for the stream is
14502 indeterminate. If a partial element is read, its value is indeterminate.
14505 The fread function returns the number of elements successfully read, which may be
14506 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
14507 fread returns zero and the contents of the array and the state of the stream remain
14510 <h5><a name="7.19.8.2" href="#7.19.8.2">7.19.8.2 The fwrite function</a></h5>
14514 #include <a href="#7.19"><stdio.h></a>
14515 size_t fwrite(const void * restrict ptr,
14516 size_t size, size_t nmemb,
14517 FILE * restrict stream);</pre>
14518 <h6>Description</h6>
14520 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
14521 whose size is specified by size, to the stream pointed to by stream. For each object,
14522 size calls are made to the fputc function, taking the values (in order) from an array of
14523 unsigned char exactly overlaying the object. The file position indicator for the
14524 stream (if defined) is advanced by the number of characters successfully written. If an
14525 error occurs, the resulting value of the file position indicator for the stream is
14530 The fwrite function returns the number of elements successfully written, which will be
14531 less than nmemb only if a write error is encountered. If size or nmemb is zero,
14532 fwrite returns zero and the state of the stream remains unchanged.
14534 <h4><a name="7.19.9" href="#7.19.9">7.19.9 File positioning functions</a></h4>
14536 <h5><a name="7.19.9.1" href="#7.19.9.1">7.19.9.1 The fgetpos function</a></h5>
14540 #include <a href="#7.19"><stdio.h></a>
14541 int fgetpos(FILE * restrict stream,
14542 fpos_t * restrict pos);</pre>
14543 <h6>Description</h6>
14545 The fgetpos function stores the current values of the parse state (if any) and file
14546 position indicator for the stream pointed to by stream in the object pointed to by pos.
14547 The values stored contain unspecified information usable by the fsetpos function for
14548 repositioning the stream to its position at the time of the call to the fgetpos function.
14551 If successful, the fgetpos function returns zero; on failure, the fgetpos function
14552 returns nonzero and stores an implementation-defined positive value in errno.
14553 <p><b> Forward references</b>: the fsetpos function (<a href="#7.19.9.3">7.19.9.3</a>).
14555 <h5><a name="7.19.9.2" href="#7.19.9.2">7.19.9.2 The fseek function</a></h5>
14559 #include <a href="#7.19"><stdio.h></a>
14560 int fseek(FILE *stream, long int offset, int whence);</pre>
14561 <h6>Description</h6>
14563 The fseek function sets the file position indicator for the stream pointed to by stream.
14564 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
14566 For a binary stream, the new position, measured in characters from the beginning of the
14567 file, is obtained by adding offset to the position specified by whence. The specified
14568 position is the beginning of the file if whence is SEEK_SET, the current value of the file
14569 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
14570 meaningfully support fseek calls with a whence value of SEEK_END.
14572 For a text stream, either offset shall be zero, or offset shall be a value returned by
14573 an earlier successful call to the ftell function on a stream associated with the same file
14574 and whence shall be SEEK_SET.
14577 After determining the new position, a successful call to the fseek function undoes any
14578 effects of the ungetc function on the stream, clears the end-of-file indicator for the
14579 stream, and then establishes the new position. After a successful fseek call, the next
14580 operation on an update stream may be either input or output.
14583 The fseek function returns nonzero only for a request that cannot be satisfied.
14584 <p><b> Forward references</b>: the ftell function (<a href="#7.19.9.4">7.19.9.4</a>).
14586 <h5><a name="7.19.9.3" href="#7.19.9.3">7.19.9.3 The fsetpos function</a></h5>
14590 #include <a href="#7.19"><stdio.h></a>
14591 int fsetpos(FILE *stream, const fpos_t *pos);</pre>
14592 <h6>Description</h6>
14594 The fsetpos function sets the mbstate_t object (if any) and file position indicator
14595 for the stream pointed to by stream according to the value of the object pointed to by
14596 pos, which shall be a value obtained from an earlier successful call to the fgetpos
14597 function on a stream associated with the same file. If a read or write error occurs, the
14598 error indicator for the stream is set and fsetpos fails.
14600 A successful call to the fsetpos function undoes any effects of the ungetc function
14601 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
14602 parse state and position. After a successful fsetpos call, the next operation on an
14603 update stream may be either input or output.
14606 If successful, the fsetpos function returns zero; on failure, the fsetpos function
14607 returns nonzero and stores an implementation-defined positive value in errno.
14609 <h5><a name="7.19.9.4" href="#7.19.9.4">7.19.9.4 The ftell function</a></h5>
14613 #include <a href="#7.19"><stdio.h></a>
14614 long int ftell(FILE *stream);</pre>
14615 <h6>Description</h6>
14617 The ftell function obtains the current value of the file position indicator for the stream
14618 pointed to by stream. For a binary stream, the value is the number of characters from
14619 the beginning of the file. For a text stream, its file position indicator contains unspecified
14620 information, usable by the fseek function for returning the file position indicator for the
14621 stream to its position at the time of the ftell call; the difference between two such
14622 return values is not necessarily a meaningful measure of the number of characters written
14627 If successful, the ftell function returns the current value of the file position indicator
14628 for the stream. On failure, the ftell function returns -1L and stores an
14629 implementation-defined positive value in errno.
14631 <h5><a name="7.19.9.5" href="#7.19.9.5">7.19.9.5 The rewind function</a></h5>
14635 #include <a href="#7.19"><stdio.h></a>
14636 void rewind(FILE *stream);</pre>
14637 <h6>Description</h6>
14639 The rewind function sets the file position indicator for the stream pointed to by
14640 stream to the beginning of the file. It is equivalent to
14642 (void)fseek(stream, 0L, SEEK_SET)</pre>
14643 except that the error indicator for the stream is also cleared.
14646 The rewind function returns no value.
14648 <h4><a name="7.19.10" href="#7.19.10">7.19.10 Error-handling functions</a></h4>
14650 <h5><a name="7.19.10.1" href="#7.19.10.1">7.19.10.1 The clearerr function</a></h5>
14654 #include <a href="#7.19"><stdio.h></a>
14655 void clearerr(FILE *stream);</pre>
14656 <h6>Description</h6>
14658 The clearerr function clears the end-of-file and error indicators for the stream pointed
14662 The clearerr function returns no value.
14665 <h5><a name="7.19.10.2" href="#7.19.10.2">7.19.10.2 The feof function</a></h5>
14669 #include <a href="#7.19"><stdio.h></a>
14670 int feof(FILE *stream);</pre>
14671 <h6>Description</h6>
14673 The feof function tests the end-of-file indicator for the stream pointed to by stream.
14676 The feof function returns nonzero if and only if the end-of-file indicator is set for
14679 <h5><a name="7.19.10.3" href="#7.19.10.3">7.19.10.3 The ferror function</a></h5>
14683 #include <a href="#7.19"><stdio.h></a>
14684 int ferror(FILE *stream);</pre>
14685 <h6>Description</h6>
14687 The ferror function tests the error indicator for the stream pointed to by stream.
14690 The ferror function returns nonzero if and only if the error indicator is set for
14693 <h5><a name="7.19.10.4" href="#7.19.10.4">7.19.10.4 The perror function</a></h5>
14697 #include <a href="#7.19"><stdio.h></a>
14698 void perror(const char *s);</pre>
14699 <h6>Description</h6>
14701 The perror function maps the error number in the integer expression errno to an
14702 error message. It writes a sequence of characters to the standard error stream thus: first
14703 (if s is not a null pointer and the character pointed to by s is not the null character), the
14704 string pointed to by s followed by a colon (:) and a space; then an appropriate error
14705 message string followed by a new-line character. The contents of the error message
14706 strings are the same as those returned by the strerror function with argument errno.
14709 The perror function returns no value.
14710 <p><b> Forward references</b>: the strerror function (<a href="#7.21.6.2">7.21.6.2</a>).
14713 <h3><a name="7.20" href="#7.20">7.20 General utilities <stdlib.h></a></h3>
14715 The header <a href="#7.20"><stdlib.h></a> declares five types and several functions of general utility, and
14716 defines several macros.<sup><a href="#note257"><b>257)</b></a></sup>
14718 The types declared are size_t and wchar_t (both described in <a href="#7.17">7.17</a>),
14721 which is a structure type that is the type of the value returned by the div function,
14724 which is a structure type that is the type of the value returned by the ldiv function, and
14727 which is a structure type that is the type of the value returned by the lldiv function.
14729 The macros defined are NULL (described in <a href="#7.17">7.17</a>);
14735 which expand to integer constant expressions that can be used as the argument to the
14736 exit function to return unsuccessful or successful termination status, respectively, to the
14740 which expands to an integer constant expression that is the maximum value returned by
14741 the rand function; and
14744 which expands to a positive integer expression with type size_t that is the maximum
14745 number of bytes in a multibyte character for the extended character set specified by the
14746 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
14754 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.26.10">7.26.10</a>).
14757 <h4><a name="7.20.1" href="#7.20.1">7.20.1 Numeric conversion functions</a></h4>
14759 The functions atof, atoi, atol, and atoll need not affect the value of the integer
14760 expression errno on an error. If the value of the result cannot be represented, the
14761 behavior is undefined.
14763 <h5><a name="7.20.1.1" href="#7.20.1.1">7.20.1.1 The atof function</a></h5>
14767 #include <a href="#7.20"><stdlib.h></a>
14768 double atof(const char *nptr);</pre>
14769 <h6>Description</h6>
14771 The atof function converts the initial portion of the string pointed to by nptr to
14772 double representation. Except for the behavior on error, it is equivalent to
14774 strtod(nptr, (char **)NULL)</pre>
14777 The atof function returns the converted value.
14778 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
14780 <h5><a name="7.20.1.2" href="#7.20.1.2">7.20.1.2 The atoi, atol, and atoll functions</a></h5>
14784 #include <a href="#7.20"><stdlib.h></a>
14785 int atoi(const char *nptr);
14786 long int atol(const char *nptr);
14787 long long int atoll(const char *nptr);</pre>
14788 <h6>Description</h6>
14790 The atoi, atol, and atoll functions convert the initial portion of the string pointed
14791 to by nptr to int, long int, and long long int representation, respectively.
14792 Except for the behavior on error, they are equivalent to
14794 atoi: (int)strtol(nptr, (char **)NULL, 10)
14795 atol: strtol(nptr, (char **)NULL, 10)
14796 atoll: strtoll(nptr, (char **)NULL, 10)</pre>
14799 The atoi, atol, and atoll functions return the converted value.
14800 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
14801 (<a href="#7.20.1.4">7.20.1.4</a>).
14804 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 The strtod, strtof, and strtold functions</a></h5>
14808 #include <a href="#7.20"><stdlib.h></a>
14809 double strtod(const char * restrict nptr,
14810 char ** restrict endptr);
14811 float strtof(const char * restrict nptr,
14812 char ** restrict endptr);
14813 long double strtold(const char * restrict nptr,
14814 char ** restrict endptr);</pre>
14815 <h6>Description</h6>
14817 The strtod, strtof, and strtold functions convert the initial portion of the string
14818 pointed to by nptr to double, float, and long double representation,
14819 respectively. First, they decompose the input string into three parts: an initial, possibly
14820 empty, sequence of white-space characters (as specified by the isspace function), a
14821 subject sequence resembling a floating-point constant or representing an infinity or NaN;
14822 and a final string of one or more unrecognized characters, including the terminating null
14823 character of the input string. Then, they attempt to convert the subject sequence to a
14824 floating-point number, and return the result.
14826 The expected form of the subject sequence is an optional plus or minus sign, then one of
14829 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
14830 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14831 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
14832 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14833 <li> INF or INFINITY, ignoring case
14834 <li> NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
14839 n-char-sequence digit
14840 n-char-sequence nondigit</pre>
14842 The subject sequence is defined as the longest initial subsequence of the input string,
14843 starting with the first non-white-space character, that is of the expected form. The subject
14844 sequence contains no characters if the input string is not of the expected form.
14846 If the subject sequence has the expected form for a floating-point number, the sequence of
14847 characters starting with the first digit or the decimal-point character (whichever occurs
14848 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
14850 decimal-point character is used in place of a period, and that if neither an exponent part
14851 nor a decimal-point character appears in a decimal floating point number, or if a binary
14852 exponent part does not appear in a hexadecimal floating point number, an exponent part
14853 of the appropriate type with value zero is assumed to follow the last digit in the string. If
14854 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note258"><b>258)</b></a></sup>
14855 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
14856 the return type, else like a floating constant that is too large for the range of the return
14857 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
14858 NaN, if supported in the return type, else like a subject sequence part that does not have
14859 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note259"><b>259)</b></a></sup> A
14860 pointer to the final string is stored in the object pointed to by endptr, provided that
14861 endptr is not a null pointer.
14863 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
14864 value resulting from the conversion is correctly rounded.
14866 In other than the "C" locale, additional locale-specific subject sequence forms may be
14869 If the subject sequence is empty or does not have the expected form, no conversion is
14870 performed; the value of nptr is stored in the object pointed to by endptr, provided
14871 that endptr is not a null pointer.
14872 <h6> Recommended practice</h6>
14874 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
14875 the result is not exactly representable, the result should be one of the two numbers in the
14876 appropriate internal format that are adjacent to the hexadecimal floating source value,
14877 with the extra stipulation that the error should have a correct sign for the current rounding
14880 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
14881 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
14882 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
14883 consider the two bounding, adjacent decimal strings L and U, both having
14884 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
14885 The result should be one of the (equal or adjacent) values that would be obtained by
14886 correctly rounding L and U according to the current rounding direction, with the extra
14889 stipulation that the error with respect to D should have a correct sign for the current
14890 rounding direction.<sup><a href="#note260"><b>260)</b></a></sup>
14893 The functions return the converted value, if any. If no conversion could be performed,
14894 zero is returned. If the correct value is outside the range of representable values, plus or
14895 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
14896 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
14897 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
14898 than the smallest normalized positive number in the return type; whether errno acquires
14899 the value ERANGE is implementation-defined.
14902 <p><small><a name="note258" href="#note258">258)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
14903 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
14904 methods may yield different results if rounding is toward positive or negative infinity. In either case,
14905 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
14907 <p><small><a name="note259" href="#note259">259)</a> An implementation may use the n-char sequence to determine extra information to be represented in
14908 the NaN's significand.
14910 <p><small><a name="note260" href="#note260">260)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
14911 to the same internal floating value, but if not will round to adjacent values.
14914 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
14918 #include <a href="#7.20"><stdlib.h></a>
14920 const char * restrict nptr,
14921 char ** restrict endptr,
14923 long long int strtoll(
14924 const char * restrict nptr,
14925 char ** restrict endptr,
14927 unsigned long int strtoul(
14928 const char * restrict nptr,
14929 char ** restrict endptr,
14931 unsigned long long int strtoull(
14932 const char * restrict nptr,
14933 char ** restrict endptr,
14935 <h6>Description</h6>
14937 The strtol, strtoll, strtoul, and strtoull functions convert the initial
14938 portion of the string pointed to by nptr to long int, long long int, unsigned
14939 long int, and unsigned long long int representation, respectively. First,
14940 they decompose the input string into three parts: an initial, possibly empty, sequence of
14941 white-space characters (as specified by the isspace function), a subject sequence
14945 resembling an integer represented in some radix determined by the value of base, and a
14946 final string of one or more unrecognized characters, including the terminating null
14947 character of the input string. Then, they attempt to convert the subject sequence to an
14948 integer, and return the result.
14950 If the value of base is zero, the expected form of the subject sequence is that of an
14951 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
14952 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
14953 expected form of the subject sequence is a sequence of letters and digits representing an
14954 integer with the radix specified by base, optionally preceded by a plus or minus sign,
14955 but not including an integer suffix. The letters from a (or A) through z (or Z) are
14956 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
14957 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
14958 optionally precede the sequence of letters and digits, following the sign if present.
14960 The subject sequence is defined as the longest initial subsequence of the input string,
14961 starting with the first non-white-space character, that is of the expected form. The subject
14962 sequence contains no characters if the input string is empty or consists entirely of white
14963 space, or if the first non-white-space character is other than a sign or a permissible letter
14966 If the subject sequence has the expected form and the value of base is zero, the sequence
14967 of characters starting with the first digit is interpreted as an integer constant according to
14968 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
14969 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
14970 as given above. If the subject sequence begins with a minus sign, the value resulting from
14971 the conversion is negated (in the return type). A pointer to the final string is stored in the
14972 object pointed to by endptr, provided that endptr is not a null pointer.
14974 In other than the "C" locale, additional locale-specific subject sequence forms may be
14977 If the subject sequence is empty or does not have the expected form, no conversion is
14978 performed; the value of nptr is stored in the object pointed to by endptr, provided
14979 that endptr is not a null pointer.
14982 The strtol, strtoll, strtoul, and strtoull functions return the converted
14983 value, if any. If no conversion could be performed, zero is returned. If the correct value
14984 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
14985 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
14986 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
14989 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Pseudo-random sequence generation functions</a></h4>
14991 <h5><a name="7.20.2.1" href="#7.20.2.1">7.20.2.1 The rand function</a></h5>
14995 #include <a href="#7.20"><stdlib.h></a>
14996 int rand(void);</pre>
14997 <h6>Description</h6>
14999 The rand function computes a sequence of pseudo-random integers in the range 0 to
15002 The implementation shall behave as if no library function calls the rand function.
15005 The rand function returns a pseudo-random integer.
15006 Environmental limits
15008 The value of the RAND_MAX macro shall be at least 32767.
15010 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 The srand function</a></h5>
15014 #include <a href="#7.20"><stdlib.h></a>
15015 void srand(unsigned int seed);</pre>
15016 <h6>Description</h6>
15018 The srand function uses the argument as a seed for a new sequence of pseudo-random
15019 numbers to be returned by subsequent calls to rand. If srand is then called with the
15020 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
15021 called before any calls to srand have been made, the same sequence shall be generated
15022 as when srand is first called with a seed value of 1.
15024 The implementation shall behave as if no library function calls the srand function.
15027 The srand function returns no value.
15029 EXAMPLE The following functions define a portable implementation of rand and srand.
15032 static unsigned long int next = 1;
15033 int rand(void) // RAND_MAX assumed to be 32767
15035 next = next * 1103515245 + 12345;
15036 return (unsigned int)(next/65536) % 32768;
15038 void srand(unsigned int seed)
15044 <h4><a name="7.20.3" href="#7.20.3">7.20.3 Memory management functions</a></h4>
15046 The order and contiguity of storage allocated by successive calls to the calloc,
15047 malloc, and realloc functions is unspecified. The pointer returned if the allocation
15048 succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
15049 and then used to access such an object or an array of such objects in the space allocated
15050 (until the space is explicitly deallocated). The lifetime of an allocated object extends
15051 from the allocation until the deallocation. Each such allocation shall yield a pointer to an
15052 object disjoint from any other object. The pointer returned points to the start (lowest byte
15053 address) of the allocated space. If the space cannot be allocated, a null pointer is
15054 returned. If the size of the space requested is zero, the behavior is implementation-
15055 defined: either a null pointer is returned, or the behavior is as if the size were some
15056 nonzero value, except that the returned pointer shall not be used to access an object.
15058 <h5><a name="7.20.3.1" href="#7.20.3.1">7.20.3.1 The calloc function</a></h5>
15062 #include <a href="#7.20"><stdlib.h></a>
15063 void *calloc(size_t nmemb, size_t size);</pre>
15064 <h6>Description</h6>
15066 The calloc function allocates space for an array of nmemb objects, each of whose size
15067 is size. The space is initialized to all bits zero.<sup><a href="#note261"><b>261)</b></a></sup>
15070 The calloc function returns either a null pointer or a pointer to the allocated space.
15073 <p><small><a name="note261" href="#note261">261)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
15077 <h5><a name="7.20.3.2" href="#7.20.3.2">7.20.3.2 The free function</a></h5>
15081 #include <a href="#7.20"><stdlib.h></a>
15082 void free(void *ptr);</pre>
15083 <h6>Description</h6>
15085 The free function causes the space pointed to by ptr to be deallocated, that is, made
15086 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
15087 the argument does not match a pointer earlier returned by the calloc, malloc, or
15091 realloc function, or if the space has been deallocated by a call to free or realloc,
15092 the behavior is undefined.
15095 The free function returns no value.
15097 <h5><a name="7.20.3.3" href="#7.20.3.3">7.20.3.3 The malloc function</a></h5>
15101 #include <a href="#7.20"><stdlib.h></a>
15102 void *malloc(size_t size);</pre>
15103 <h6>Description</h6>
15105 The malloc function allocates space for an object whose size is specified by size and
15106 whose value is indeterminate.
15109 The malloc function returns either a null pointer or a pointer to the allocated space.
15111 <h5><a name="7.20.3.4" href="#7.20.3.4">7.20.3.4 The realloc function</a></h5>
15115 #include <a href="#7.20"><stdlib.h></a>
15116 void *realloc(void *ptr, size_t size);</pre>
15117 <h6>Description</h6>
15119 The realloc function deallocates the old object pointed to by ptr and returns a
15120 pointer to a new object that has the size specified by size. The contents of the new
15121 object shall be the same as that of the old object prior to deallocation, up to the lesser of
15122 the new and old sizes. Any bytes in the new object beyond the size of the old object have
15123 indeterminate values.
15125 If ptr is a null pointer, the realloc function behaves like the malloc function for the
15126 specified size. Otherwise, if ptr does not match a pointer earlier returned by the
15127 calloc, malloc, or realloc function, or if the space has been deallocated by a call
15128 to the free or realloc function, the behavior is undefined. If memory for the new
15129 object cannot be allocated, the old object is not deallocated and its value is unchanged.
15132 The realloc function returns a pointer to the new object (which may have the same
15133 value as a pointer to the old object), or a null pointer if the new object could not be
15137 <h4><a name="7.20.4" href="#7.20.4">7.20.4 Communication with the environment</a></h4>
15139 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 The abort function</a></h5>
15143 #include <a href="#7.20"><stdlib.h></a>
15144 void abort(void);</pre>
15145 <h6>Description</h6>
15147 The abort function causes abnormal program termination to occur, unless the signal
15148 SIGABRT is being caught and the signal handler does not return. Whether open streams
15149 with unwritten buffered data are flushed, open streams are closed, or temporary files are
15150 removed is implementation-defined. An implementation-defined form of the status
15151 unsuccessful termination is returned to the host environment by means of the function
15152 call raise(SIGABRT).
15155 The abort function does not return to its caller.
15157 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 The atexit function</a></h5>
15161 #include <a href="#7.20"><stdlib.h></a>
15162 int atexit(void (*func)(void));</pre>
15163 <h6>Description</h6>
15165 The atexit function registers the function pointed to by func, to be called without
15166 arguments at normal program termination.
15167 Environmental limits
15169 The implementation shall support the registration of at least 32 functions.
15172 The atexit function returns zero if the registration succeeds, nonzero if it fails.
15173 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15175 <h5><a name="7.20.4.3" href="#7.20.4.3">7.20.4.3 The exit function</a></h5>
15179 #include <a href="#7.20"><stdlib.h></a>
15180 void exit(int status);</pre>
15181 <h6>Description</h6>
15183 The exit function causes normal program termination to occur. If more than one call to
15184 the exit function is executed by a program, the behavior is undefined.
15187 First, all functions registered by the atexit function are called, in the reverse order of
15188 their registration,<sup><a href="#note262"><b>262)</b></a></sup> except that a function is called after any previously registered
15189 functions that had already been called at the time it was registered. If, during the call to
15190 any such function, a call to the longjmp function is made that would terminate the call
15191 to the registered function, the behavior is undefined.
15193 Next, all open streams with unwritten buffered data are flushed, all open streams are
15194 closed, and all files created by the tmpfile function are removed.
15196 Finally, control is returned to the host environment. If the value of status is zero or
15197 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
15198 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
15199 of the status unsuccessful termination is returned. Otherwise the status returned is
15200 implementation-defined.
15203 The exit function cannot return to its caller.
15206 <p><small><a name="note262" href="#note262">262)</a> Each function is called as many times as it was registered, and in the correct order with respect to
15207 other registered functions.
15210 <h5><a name="7.20.4.4" href="#7.20.4.4">7.20.4.4 The _Exit function</a></h5>
15214 #include <a href="#7.20"><stdlib.h></a>
15215 void _Exit(int status);</pre>
15216 <h6>Description</h6>
15218 The _Exit function causes normal program termination to occur and control to be
15219 returned to the host environment. No functions registered by the atexit function or
15220 signal handlers registered by the signal function are called. The status returned to the
15221 host environment is determined in the same way as for the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15222 Whether open streams with unwritten buffered data are flushed, open streams are closed,
15223 or temporary files are removed is implementation-defined.
15226 The _Exit function cannot return to its caller.
15233 <h5><a name="7.20.4.5" href="#7.20.4.5">7.20.4.5 The getenv function</a></h5>
15237 #include <a href="#7.20"><stdlib.h></a>
15238 char *getenv(const char *name);</pre>
15239 <h6>Description</h6>
15241 The getenv function searches an environment list, provided by the host environment,
15242 for a string that matches the string pointed to by name. The set of environment names
15243 and the method for altering the environment list are implementation-defined.
15245 The implementation shall behave as if no library function calls the getenv function.
15248 The getenv function returns a pointer to a string associated with the matched list
15249 member. The string pointed to shall not be modified by the program, but may be
15250 overwritten by a subsequent call to the getenv function. If the specified name cannot
15251 be found, a null pointer is returned.
15253 <h5><a name="7.20.4.6" href="#7.20.4.6">7.20.4.6 The system function</a></h5>
15257 #include <a href="#7.20"><stdlib.h></a>
15258 int system(const char *string);</pre>
15259 <h6>Description</h6>
15261 If string is a null pointer, the system function determines whether the host
15262 environment has a command processor. If string is not a null pointer, the system
15263 function passes the string pointed to by string to that command processor to be
15264 executed in a manner which the implementation shall document; this might then cause the
15265 program calling system to behave in a non-conforming manner or to terminate.
15268 If the argument is a null pointer, the system function returns nonzero only if a
15269 command processor is available. If the argument is not a null pointer, and the system
15270 function does return, it returns an implementation-defined value.
15273 <h4><a name="7.20.5" href="#7.20.5">7.20.5 Searching and sorting utilities</a></h4>
15275 These utilities make use of a comparison function to search or sort arrays of unspecified
15276 type. Where an argument declared as size_t nmemb specifies the length of the array
15277 for a function, nmemb can have the value zero on a call to that function; the comparison
15278 function is not called, a search finds no matching element, and sorting performs no
15279 rearrangement. Pointer arguments on such a call shall still have valid values, as described
15280 in <a href="#7.1.4">7.1.4</a>.
15282 The implementation shall ensure that the second argument of the comparison function
15283 (when called from bsearch), or both arguments (when called from qsort), are
15284 pointers to elements of the array.<sup><a href="#note263"><b>263)</b></a></sup> The first argument when called from bsearch
15287 The comparison function shall not alter the contents of the array. The implementation
15288 may reorder elements of the array between calls to the comparison function, but shall not
15289 alter the contents of any individual element.
15291 When the same objects (consisting of size bytes, irrespective of their current positions
15292 in the array) are passed more than once to the comparison function, the results shall be
15293 consistent with one another. That is, for qsort they shall define a total ordering on the
15294 array, and for bsearch the same object shall always compare the same way with the
15297 A sequence point occurs immediately before and immediately after each call to the
15298 comparison function, and also between any call to the comparison function and any
15299 movement of the objects passed as arguments to that call.
15302 <p><small><a name="note263" href="#note263">263)</a> That is, if the value passed is p, then the following expressions are always nonzero:
15305 ((char *)p - (char *)base) % size == 0
15306 (char *)p >= (char *)base
15307 (char *)p < (char *)base + nmemb * size</pre>
15310 <h5><a name="7.20.5.1" href="#7.20.5.1">7.20.5.1 The bsearch function</a></h5>
15314 #include <a href="#7.20"><stdlib.h></a>
15315 void *bsearch(const void *key, const void *base,
15316 size_t nmemb, size_t size,
15317 int (*compar)(const void *, const void *));</pre>
15318 <h6>Description</h6>
15320 The bsearch function searches an array of nmemb objects, the initial element of which
15321 is pointed to by base, for an element that matches the object pointed to by key. The
15325 size of each element of the array is specified by size.
15327 The comparison function pointed to by compar is called with two arguments that point
15328 to the key object and to an array element, in that order. The function shall return an
15329 integer less than, equal to, or greater than zero if the key object is considered,
15330 respectively, to be less than, to match, or to be greater than the array element. The array
15331 shall consist of: all the elements that compare less than, all the elements that compare
15332 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note264"><b>264)</b></a></sup>
15335 The bsearch function returns a pointer to a matching element of the array, or a null
15336 pointer if no match is found. If two elements compare as equal, which element is
15337 matched is unspecified.
15340 <p><small><a name="note264" href="#note264">264)</a> In practice, the entire array is sorted according to the comparison function.
15343 <h5><a name="7.20.5.2" href="#7.20.5.2">7.20.5.2 The qsort function</a></h5>
15347 #include <a href="#7.20"><stdlib.h></a>
15348 void qsort(void *base, size_t nmemb, size_t size,
15349 int (*compar)(const void *, const void *));</pre>
15350 <h6>Description</h6>
15352 The qsort function sorts an array of nmemb objects, the initial element of which is
15353 pointed to by base. The size of each object is specified by size.
15355 The contents of the array are sorted into ascending order according to a comparison
15356 function pointed to by compar, which is called with two arguments that point to the
15357 objects being compared. The function shall return an integer less than, equal to, or
15358 greater than zero if the first argument is considered to be respectively less than, equal to,
15359 or greater than the second.
15361 If two elements compare as equal, their order in the resulting sorted array is unspecified.
15364 The qsort function returns no value.
15371 <h4><a name="7.20.6" href="#7.20.6">7.20.6 Integer arithmetic functions</a></h4>
15373 <h5><a name="7.20.6.1" href="#7.20.6.1">7.20.6.1 The abs, labs and llabs functions</a></h5>
15377 #include <a href="#7.20"><stdlib.h></a>
15379 long int labs(long int j);
15380 long long int llabs(long long int j);</pre>
15381 <h6>Description</h6>
15383 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
15384 result cannot be represented, the behavior is undefined.<sup><a href="#note265"><b>265)</b></a></sup>
15387 The abs, labs, and llabs, functions return the absolute value.
15390 <p><small><a name="note265" href="#note265">265)</a> The absolute value of the most negative number cannot be represented in two's complement.
15393 <h5><a name="7.20.6.2" href="#7.20.6.2">7.20.6.2 The div, ldiv, and lldiv functions</a></h5>
15397 #include <a href="#7.20"><stdlib.h></a>
15398 div_t div(int numer, int denom);
15399 ldiv_t ldiv(long int numer, long int denom);
15400 lldiv_t lldiv(long long int numer, long long int denom);</pre>
15401 <h6>Description</h6>
15403 The div, ldiv, and lldiv, functions compute numer / denom and numer %
15404 denom in a single operation.
15407 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
15408 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
15409 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
15410 each of which has the same type as the arguments numer and denom. If either part of
15411 the result cannot be represented, the behavior is undefined.
15418 <h4><a name="7.20.7" href="#7.20.7">7.20.7 Multibyte/wide character conversion functions</a></h4>
15420 The behavior of the multibyte character functions is affected by the LC_CTYPE category
15421 of the current locale. For a state-dependent encoding, each function is placed into its
15422 initial conversion state by a call for which its character pointer argument, s, is a null
15423 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
15424 state of the function to be altered as necessary. A call with s as a null pointer causes
15425 these functions to return a nonzero value if encodings have state dependency, and zero
15426 otherwise.<sup><a href="#note266"><b>266)</b></a></sup> Changing the LC_CTYPE category causes the conversion state of these
15427 functions to be indeterminate.
15430 <p><small><a name="note266" href="#note266">266)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
15431 character codes, but are grouped with an adjacent multibyte character.
15434 <h5><a name="7.20.7.1" href="#7.20.7.1">7.20.7.1 The mblen function</a></h5>
15438 #include <a href="#7.20"><stdlib.h></a>
15439 int mblen(const char *s, size_t n);</pre>
15440 <h6>Description</h6>
15442 If s is not a null pointer, the mblen function determines the number of bytes contained
15443 in the multibyte character pointed to by s. Except that the conversion state of the
15444 mbtowc function is not affected, it is equivalent to
15447 mbtowc((wchar_t *)0, s, n);</pre>
15448 The implementation shall behave as if no library function calls the mblen function.
15451 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
15452 character encodings, respectively, do or do not have state-dependent encodings. If s is
15453 not a null pointer, the mblen function either returns 0 (if s points to the null character),
15454 or returns the number of bytes that are contained in the multibyte character (if the next n
15455 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
15456 multibyte character).
15457 <p><b> Forward references</b>: the mbtowc function (<a href="#7.20.7.2">7.20.7.2</a>).
15464 <h5><a name="7.20.7.2" href="#7.20.7.2">7.20.7.2 The mbtowc function</a></h5>
15468 #include <a href="#7.20"><stdlib.h></a>
15469 int mbtowc(wchar_t * restrict pwc,
15470 const char * restrict s,
15472 <h6>Description</h6>
15474 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
15475 the byte pointed to by s to determine the number of bytes needed to complete the next
15476 multibyte character (including any shift sequences). If the function determines that the
15477 next multibyte character is complete and valid, it determines the value of the
15478 corresponding wide character and then, if pwc is not a null pointer, stores that value in
15479 the object pointed to by pwc. If the corresponding wide character is the null wide
15480 character, the function is left in the initial conversion state.
15482 The implementation shall behave as if no library function calls the mbtowc function.
15485 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
15486 character encodings, respectively, do or do not have state-dependent encodings. If s is
15487 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
15488 or returns the number of bytes that are contained in the converted multibyte character (if
15489 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
15490 form a valid multibyte character).
15492 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
15495 <h5><a name="7.20.7.3" href="#7.20.7.3">7.20.7.3 The wctomb function</a></h5>
15499 #include <a href="#7.20"><stdlib.h></a>
15500 int wctomb(char *s, wchar_t wc);</pre>
15501 <h6>Description</h6>
15503 The wctomb function determines the number of bytes needed to represent the multibyte
15504 character corresponding to the wide character given by wc (including any shift
15505 sequences), and stores the multibyte character representation in the array whose first
15506 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
15507 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
15508 sequence needed to restore the initial shift state, and the function is left in the initial
15512 The implementation shall behave as if no library function calls the wctomb function.
15515 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
15516 character encodings, respectively, do or do not have state-dependent encodings. If s is
15517 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
15518 to a valid multibyte character, or returns the number of bytes that are contained in the
15519 multibyte character corresponding to the value of wc.
15521 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
15523 <h4><a name="7.20.8" href="#7.20.8">7.20.8 Multibyte/wide string conversion functions</a></h4>
15525 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
15526 the current locale.
15528 <h5><a name="7.20.8.1" href="#7.20.8.1">7.20.8.1 The mbstowcs function</a></h5>
15532 #include <a href="#7.20"><stdlib.h></a>
15533 size_t mbstowcs(wchar_t * restrict pwcs,
15534 const char * restrict s,
15536 <h6>Description</h6>
15538 The mbstowcs function converts a sequence of multibyte characters that begins in the
15539 initial shift state from the array pointed to by s into a sequence of corresponding wide
15540 characters and stores not more than n wide characters into the array pointed to by pwcs.
15541 No multibyte characters that follow a null character (which is converted into a null wide
15542 character) will be examined or converted. Each multibyte character is converted as if by
15543 a call to the mbtowc function, except that the conversion state of the mbtowc function is
15546 No more than n elements will be modified in the array pointed to by pwcs. If copying
15547 takes place between objects that overlap, the behavior is undefined.
15550 If an invalid multibyte character is encountered, the mbstowcs function returns
15551 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
15552 elements modified, not including a terminating null wide character, if any.<sup><a href="#note267"><b>267)</b></a></sup>
15560 <p><small><a name="note267" href="#note267">267)</a> The array will not be null-terminated if the value returned is n.
15563 <h5><a name="7.20.8.2" href="#7.20.8.2">7.20.8.2 The wcstombs function</a></h5>
15567 #include <a href="#7.20"><stdlib.h></a>
15568 size_t wcstombs(char * restrict s,
15569 const wchar_t * restrict pwcs,
15571 <h6>Description</h6>
15573 The wcstombs function converts a sequence of wide characters from the array pointed
15574 to by pwcs into a sequence of corresponding multibyte characters that begins in the
15575 initial shift state, and stores these multibyte characters into the array pointed to by s,
15576 stopping if a multibyte character would exceed the limit of n total bytes or if a null
15577 character is stored. Each wide character is converted as if by a call to the wctomb
15578 function, except that the conversion state of the wctomb function is not affected.
15580 No more than n bytes will be modified in the array pointed to by s. If copying takes place
15581 between objects that overlap, the behavior is undefined.
15584 If a wide character is encountered that does not correspond to a valid multibyte character,
15585 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
15586 returns the number of bytes modified, not including a terminating null character, if
15590 <h3><a name="7.21" href="#7.21">7.21 String handling <string.h></a></h3>
15592 <h4><a name="7.21.1" href="#7.21.1">7.21.1 String function conventions</a></h4>
15594 The header <a href="#7.21"><string.h></a> declares one type and several functions, and defines one
15595 macro useful for manipulating arrays of character type and other objects treated as arrays
15596 of character type.<sup><a href="#note268"><b>268)</b></a></sup> The type is size_t and the macro is NULL (both described in
15597 <a href="#7.17">7.17</a>). Various methods are used for determining the lengths of the arrays, but in all cases
15598 a char * or void * argument points to the initial (lowest addressed) character of the
15599 array. If an array is accessed beyond the end of an object, the behavior is undefined.
15601 Where an argument declared as size_t n specifies the length of the array for a
15602 function, n can have the value zero on a call to that function. Unless explicitly stated
15603 otherwise in the description of a particular function in this subclause, pointer arguments
15604 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
15605 function that locates a character finds no occurrence, a function that compares two
15606 character sequences returns zero, and a function that copies characters copies zero
15609 For all functions in this subclause, each character shall be interpreted as if it had the type
15610 unsigned char (and therefore every possible object representation is valid and has a
15614 <p><small><a name="note268" href="#note268">268)</a> See ''future library directions'' (<a href="#7.26.11">7.26.11</a>).
15617 <h4><a name="7.21.2" href="#7.21.2">7.21.2 Copying functions</a></h4>
15619 <h5><a name="7.21.2.1" href="#7.21.2.1">7.21.2.1 The memcpy function</a></h5>
15623 #include <a href="#7.21"><string.h></a>
15624 void *memcpy(void * restrict s1,
15625 const void * restrict s2,
15627 <h6>Description</h6>
15629 The memcpy function copies n characters from the object pointed to by s2 into the
15630 object pointed to by s1. If copying takes place between objects that overlap, the behavior
15634 The memcpy function returns the value of s1.
15641 <h5><a name="7.21.2.2" href="#7.21.2.2">7.21.2.2 The memmove function</a></h5>
15645 #include <a href="#7.21"><string.h></a>
15646 void *memmove(void *s1, const void *s2, size_t n);</pre>
15647 <h6>Description</h6>
15649 The memmove function copies n characters from the object pointed to by s2 into the
15650 object pointed to by s1. Copying takes place as if the n characters from the object
15651 pointed to by s2 are first copied into a temporary array of n characters that does not
15652 overlap the objects pointed to by s1 and s2, and then the n characters from the
15653 temporary array are copied into the object pointed to by s1.
15656 The memmove function returns the value of s1.
15658 <h5><a name="7.21.2.3" href="#7.21.2.3">7.21.2.3 The strcpy function</a></h5>
15662 #include <a href="#7.21"><string.h></a>
15663 char *strcpy(char * restrict s1,
15664 const char * restrict s2);</pre>
15665 <h6>Description</h6>
15667 The strcpy function copies the string pointed to by s2 (including the terminating null
15668 character) into the array pointed to by s1. If copying takes place between objects that
15669 overlap, the behavior is undefined.
15672 The strcpy function returns the value of s1.
15674 <h5><a name="7.21.2.4" href="#7.21.2.4">7.21.2.4 The strncpy function</a></h5>
15678 #include <a href="#7.21"><string.h></a>
15679 char *strncpy(char * restrict s1,
15680 const char * restrict s2,
15682 <h6>Description</h6>
15684 The strncpy function copies not more than n characters (characters that follow a null
15685 character are not copied) from the array pointed to by s2 to the array pointed to by
15687 s1.<sup><a href="#note269"><b>269)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
15689 If the array pointed to by s2 is a string that is shorter than n characters, null characters
15690 are appended to the copy in the array pointed to by s1, until n characters in all have been
15694 The strncpy function returns the value of s1.
15697 <p><small><a name="note269" href="#note269">269)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
15698 not be null-terminated.
15701 <h4><a name="7.21.3" href="#7.21.3">7.21.3 Concatenation functions</a></h4>
15703 <h5><a name="7.21.3.1" href="#7.21.3.1">7.21.3.1 The strcat function</a></h5>
15707 #include <a href="#7.21"><string.h></a>
15708 char *strcat(char * restrict s1,
15709 const char * restrict s2);</pre>
15710 <h6>Description</h6>
15712 The strcat function appends a copy of the string pointed to by s2 (including the
15713 terminating null character) to the end of the string pointed to by s1. The initial character
15714 of s2 overwrites the null character at the end of s1. If copying takes place between
15715 objects that overlap, the behavior is undefined.
15718 The strcat function returns the value of s1.
15720 <h5><a name="7.21.3.2" href="#7.21.3.2">7.21.3.2 The strncat function</a></h5>
15724 #include <a href="#7.21"><string.h></a>
15725 char *strncat(char * restrict s1,
15726 const char * restrict s2,
15728 <h6>Description</h6>
15730 The strncat function appends not more than n characters (a null character and
15731 characters that follow it are not appended) from the array pointed to by s2 to the end of
15732 the string pointed to by s1. The initial character of s2 overwrites the null character at the
15733 end of s1. A terminating null character is always appended to the result.<sup><a href="#note270"><b>270)</b></a></sup> If copying
15736 takes place between objects that overlap, the behavior is undefined.
15739 The strncat function returns the value of s1.
15740 <p><b> Forward references</b>: the strlen function (<a href="#7.21.6.3">7.21.6.3</a>).
15743 <p><small><a name="note270" href="#note270">270)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
15747 <h4><a name="7.21.4" href="#7.21.4">7.21.4 Comparison functions</a></h4>
15749 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
15750 and strncmp is determined by the sign of the difference between the values of the first
15751 pair of characters (both interpreted as unsigned char) that differ in the objects being
15754 <h5><a name="7.21.4.1" href="#7.21.4.1">7.21.4.1 The memcmp function</a></h5>
15758 #include <a href="#7.21"><string.h></a>
15759 int memcmp(const void *s1, const void *s2, size_t n);</pre>
15760 <h6>Description</h6>
15762 The memcmp function compares the first n characters of the object pointed to by s1 to
15763 the first n characters of the object pointed to by s2.<sup><a href="#note271"><b>271)</b></a></sup>
15766 The memcmp function returns an integer greater than, equal to, or less than zero,
15767 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
15771 <p><small><a name="note271" href="#note271">271)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
15772 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
15776 <h5><a name="7.21.4.2" href="#7.21.4.2">7.21.4.2 The strcmp function</a></h5>
15780 #include <a href="#7.21"><string.h></a>
15781 int strcmp(const char *s1, const char *s2);</pre>
15782 <h6>Description</h6>
15784 The strcmp function compares the string pointed to by s1 to the string pointed to by
15788 The strcmp function returns an integer greater than, equal to, or less than zero,
15789 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15794 <h5><a name="7.21.4.3" href="#7.21.4.3">7.21.4.3 The strcoll function</a></h5>
15798 #include <a href="#7.21"><string.h></a>
15799 int strcoll(const char *s1, const char *s2);</pre>
15800 <h6>Description</h6>
15802 The strcoll function compares the string pointed to by s1 to the string pointed to by
15803 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
15806 The strcoll function returns an integer greater than, equal to, or less than zero,
15807 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15808 pointed to by s2 when both are interpreted as appropriate to the current locale.
15810 <h5><a name="7.21.4.4" href="#7.21.4.4">7.21.4.4 The strncmp function</a></h5>
15814 #include <a href="#7.21"><string.h></a>
15815 int strncmp(const char *s1, const char *s2, size_t n);</pre>
15816 <h6>Description</h6>
15818 The strncmp function compares not more than n characters (characters that follow a
15819 null character are not compared) from the array pointed to by s1 to the array pointed to
15823 The strncmp function returns an integer greater than, equal to, or less than zero,
15824 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
15825 to, or less than the possibly null-terminated array pointed to by s2.
15827 <h5><a name="7.21.4.5" href="#7.21.4.5">7.21.4.5 The strxfrm function</a></h5>
15831 #include <a href="#7.21"><string.h></a>
15832 size_t strxfrm(char * restrict s1,
15833 const char * restrict s2,
15835 <h6>Description</h6>
15837 The strxfrm function transforms the string pointed to by s2 and places the resulting
15838 string into the array pointed to by s1. The transformation is such that if the strcmp
15839 function is applied to two transformed strings, it returns a value greater than, equal to, or
15841 less than zero, corresponding to the result of the strcoll function applied to the same
15842 two original strings. No more than n characters are placed into the resulting array
15843 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
15844 be a null pointer. If copying takes place between objects that overlap, the behavior is
15848 The strxfrm function returns the length of the transformed string (not including the
15849 terminating null character). If the value returned is n or more, the contents of the array
15850 pointed to by s1 are indeterminate.
15852 EXAMPLE The value of the following expression is the size of the array needed to hold the
15853 transformation of the string pointed to by s.
15855 1 + strxfrm(NULL, s, 0)</pre>
15858 <h4><a name="7.21.5" href="#7.21.5">7.21.5 Search functions</a></h4>
15860 <h5><a name="7.21.5.1" href="#7.21.5.1">7.21.5.1 The memchr function</a></h5>
15864 #include <a href="#7.21"><string.h></a>
15865 void *memchr(const void *s, int c, size_t n);</pre>
15866 <h6>Description</h6>
15868 The memchr function locates the first occurrence of c (converted to an unsigned
15869 char) in the initial n characters (each interpreted as unsigned char) of the object
15873 The memchr function returns a pointer to the located character, or a null pointer if the
15874 character does not occur in the object.
15876 <h5><a name="7.21.5.2" href="#7.21.5.2">7.21.5.2 The strchr function</a></h5>
15880 #include <a href="#7.21"><string.h></a>
15881 char *strchr(const char *s, int c);</pre>
15882 <h6>Description</h6>
15884 The strchr function locates the first occurrence of c (converted to a char) in the
15885 string pointed to by s. The terminating null character is considered to be part of the
15889 The strchr function returns a pointer to the located character, or a null pointer if the
15890 character does not occur in the string.
15893 <h5><a name="7.21.5.3" href="#7.21.5.3">7.21.5.3 The strcspn function</a></h5>
15897 #include <a href="#7.21"><string.h></a>
15898 size_t strcspn(const char *s1, const char *s2);</pre>
15899 <h6>Description</h6>
15901 The strcspn function computes the length of the maximum initial segment of the string
15902 pointed to by s1 which consists entirely of characters not from the string pointed to by
15906 The strcspn function returns the length of the segment.
15908 <h5><a name="7.21.5.4" href="#7.21.5.4">7.21.5.4 The strpbrk function</a></h5>
15912 #include <a href="#7.21"><string.h></a>
15913 char *strpbrk(const char *s1, const char *s2);</pre>
15914 <h6>Description</h6>
15916 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
15917 character from the string pointed to by s2.
15920 The strpbrk function returns a pointer to the character, or a null pointer if no character
15921 from s2 occurs in s1.
15923 <h5><a name="7.21.5.5" href="#7.21.5.5">7.21.5.5 The strrchr function</a></h5>
15927 #include <a href="#7.21"><string.h></a>
15928 char *strrchr(const char *s, int c);</pre>
15929 <h6>Description</h6>
15931 The strrchr function locates the last occurrence of c (converted to a char) in the
15932 string pointed to by s. The terminating null character is considered to be part of the
15936 The strrchr function returns a pointer to the character, or a null pointer if c does not
15937 occur in the string.
15940 <h5><a name="7.21.5.6" href="#7.21.5.6">7.21.5.6 The strspn function</a></h5>
15944 #include <a href="#7.21"><string.h></a>
15945 size_t strspn(const char *s1, const char *s2);</pre>
15946 <h6>Description</h6>
15948 The strspn function computes the length of the maximum initial segment of the string
15949 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
15952 The strspn function returns the length of the segment.
15954 <h5><a name="7.21.5.7" href="#7.21.5.7">7.21.5.7 The strstr function</a></h5>
15958 #include <a href="#7.21"><string.h></a>
15959 char *strstr(const char *s1, const char *s2);</pre>
15960 <h6>Description</h6>
15962 The strstr function locates the first occurrence in the string pointed to by s1 of the
15963 sequence of characters (excluding the terminating null character) in the string pointed to
15967 The strstr function returns a pointer to the located string, or a null pointer if the string
15968 is not found. If s2 points to a string with zero length, the function returns s1.
15970 <h5><a name="7.21.5.8" href="#7.21.5.8">7.21.5.8 The strtok function</a></h5>
15974 #include <a href="#7.21"><string.h></a>
15975 char *strtok(char * restrict s1,
15976 const char * restrict s2);</pre>
15977 <h6>Description</h6>
15979 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
15980 sequence of tokens, each of which is delimited by a character from the string pointed to
15981 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
15982 sequence have a null first argument. The separator string pointed to by s2 may be
15983 different from call to call.
15985 The first call in the sequence searches the string pointed to by s1 for the first character
15986 that is not contained in the current separator string pointed to by s2. If no such character
15987 is found, then there are no tokens in the string pointed to by s1 and the strtok function
15989 returns a null pointer. If such a character is found, it is the start of the first token.
15991 The strtok function then searches from there for a character that is contained in the
15992 current separator string. If no such character is found, the current token extends to the
15993 end of the string pointed to by s1, and subsequent searches for a token will return a null
15994 pointer. If such a character is found, it is overwritten by a null character, which
15995 terminates the current token. The strtok function saves a pointer to the following
15996 character, from which the next search for a token will start.
15998 Each subsequent call, with a null pointer as the value of the first argument, starts
15999 searching from the saved pointer and behaves as described above.
16001 The implementation shall behave as if no library function calls the strtok function.
16004 The strtok function returns a pointer to the first character of a token, or a null pointer
16005 if there is no token.
16009 #include <a href="#7.21"><string.h></a>
16010 static char str[] = "?a???b,,,#c";
16012 t = strtok(str, "?"); // t points to the token "a"
16013 t = strtok(NULL, ","); // t points to the token "??b"
16014 t = strtok(NULL, "#,"); // t points to the token "c"
16015 t = strtok(NULL, "?"); // t is a null pointer</pre>
16018 <h4><a name="7.21.6" href="#7.21.6">7.21.6 Miscellaneous functions</a></h4>
16020 <h5><a name="7.21.6.1" href="#7.21.6.1">7.21.6.1 The memset function</a></h5>
16024 #include <a href="#7.21"><string.h></a>
16025 void *memset(void *s, int c, size_t n);</pre>
16026 <h6>Description</h6>
16028 The memset function copies the value of c (converted to an unsigned char) into
16029 each of the first n characters of the object pointed to by s.
16032 The memset function returns the value of s.
16035 <h5><a name="7.21.6.2" href="#7.21.6.2">7.21.6.2 The strerror function</a></h5>
16039 #include <a href="#7.21"><string.h></a>
16040 char *strerror(int errnum);</pre>
16041 <h6>Description</h6>
16043 The strerror function maps the number in errnum to a message string. Typically,
16044 the values for errnum come from errno, but strerror shall map any value of type
16047 The implementation shall behave as if no library function calls the strerror function.
16050 The strerror function returns a pointer to the string, the contents of which are locale-
16051 specific. The array pointed to shall not be modified by the program, but may be
16052 overwritten by a subsequent call to the strerror function.
16054 <h5><a name="7.21.6.3" href="#7.21.6.3">7.21.6.3 The strlen function</a></h5>
16058 #include <a href="#7.21"><string.h></a>
16059 size_t strlen(const char *s);</pre>
16060 <h6>Description</h6>
16062 The strlen function computes the length of the string pointed to by s.
16065 The strlen function returns the number of characters that precede the terminating null
16069 <h3><a name="7.22" href="#7.22">7.22 Type-generic math <tgmath.h></a></h3>
16071 The header <a href="#7.22"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
16072 defines several type-generic macros.
16074 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
16075 double) suffix, several have one or more parameters whose corresponding real type is
16076 double. For each such function, except modf, there is a corresponding type-generic
16077 macro.<sup><a href="#note272"><b>272)</b></a></sup> The parameters whose corresponding real type is double in the function
16078 synopsis are generic parameters. Use of the macro invokes a function whose
16079 corresponding real type and type domain are determined by the arguments for the generic
16080 parameters.<sup><a href="#note273"><b>273)</b></a></sup>
16082 Use of the macro invokes a function whose generic parameters have the corresponding
16083 real type determined as follows:
16085 <li> First, if any argument for generic parameters has type long double, the type
16086 determined is long double.
16087 <li> Otherwise, if any argument for generic parameters has type double or is of integer
16088 type, the type determined is double.
16089 <li> Otherwise, the type determined is float.
16092 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
16093 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
16094 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
16095 corresponding type-generic macro for fabs and cabs is fabs.
16102 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
16103 function function macro
16120 fabs cabs fabs</pre>
16121 If at least one argument for a generic parameter is complex, then use of the macro invokes
16122 a complex function; otherwise, use of the macro invokes a real function.
16124 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
16125 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
16126 name as the function. These type-generic macros are:
16128 atan2 fma llround remainder
16129 cbrt fmax log10 remquo
16130 ceil fmin log1p rint
16131 copysign fmod log2 round
16132 erf frexp logb scalbn
16133 erfc hypot lrint scalbln
16134 exp2 ilogb lround tgamma
16135 expm1 ldexp nearbyint trunc
16136 fdim lgamma nextafter
16137 floor llrint nexttoward</pre>
16138 If all arguments for generic parameters are real, then use of the macro invokes a real
16139 function; otherwise, use of the macro results in undefined behavior.
16141 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
16142 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
16143 function. These type-generic macros are:
16148 Use of the macro with any real or complex argument invokes a complex function.
16150 EXAMPLE With the declarations
16152 #include <a href="#7.22"><tgmath.h></a>
16159 long double complex ldc;</pre>
16160 functions invoked by use of type-generic macros are shown in the following table:
16164 exp(n) exp(n), the function
16166 sin(d) sin(d), the function
16170 pow(ldc, f) cpowl(ldc, f)
16171 remainder(n, n) remainder(n, n), the function
16172 nextafter(d, f) nextafter(d, f), the function
16173 nexttoward(f, ld) nexttowardf(f, ld)
16174 copysign(n, ld) copysignl(n, ld)
16175 ceil(fc) undefined behavior
16176 rint(dc) undefined behavior
16177 fmax(ldc, ld) undefined behavior
16178 carg(n) carg(n), the function
16180 creal(d) creal(d), the function
16181 cimag(ld) cimagl(ld)
16183 carg(dc) carg(dc), the function
16184 cproj(ldc) cprojl(ldc)</pre>
16187 <p><small><a name="note272" href="#note272">272)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
16188 make available the corresponding ordinary function.
16190 <p><small><a name="note273" href="#note273">273)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
16191 the behavior is undefined.
16194 <h3><a name="7.23" href="#7.23">7.23 Date and time <time.h></a></h3>
16196 <h4><a name="7.23.1" href="#7.23.1">7.23.1 Components of time</a></h4>
16198 The header <a href="#7.23"><time.h></a> defines two macros, and declares several types and functions for
16199 manipulating time. Many functions deal with a calendar time that represents the current
16200 date (according to the Gregorian calendar) and time. Some functions deal with local
16201 time, which is the calendar time expressed for some specific time zone, and with Daylight
16202 Saving Time, which is a temporary change in the algorithm for determining local time.
16203 The local time zone and Daylight Saving Time are implementation-defined.
16205 The macros defined are NULL (described in <a href="#7.17">7.17</a>); and
16207 CLOCKS_PER_SEC</pre>
16208 which expands to an expression with type clock_t (described below) that is the
16209 number per second of the value returned by the clock function.
16211 The types declared are size_t (described in <a href="#7.17">7.17</a>);
16217 which are arithmetic types capable of representing times; and
16220 which holds the components of a calendar time, called the broken-down time.
16222 The range and precision of times representable in clock_t and time_t are
16223 implementation-defined. The tm structure shall contain at least the following members,
16224 in any order. The semantics of the members and their normal ranges are expressed in the
16225 comments.<sup><a href="#note274"><b>274)</b></a></sup>
16227 int tm_sec; // seconds after the minute -- [0, 60]
16228 int tm_min; // minutes after the hour -- [0, 59]
16229 int tm_hour; // hours since midnight -- [0, 23]
16230 int tm_mday; // day of the month -- [1, 31]
16231 int tm_mon; // months since January -- [0, 11]
16232 int tm_year; // years since 1900
16233 int tm_wday; // days since Sunday -- [0, 6]
16234 int tm_yday; // days since January 1 -- [0, 365]
16235 int tm_isdst; // Daylight Saving Time flag</pre>
16240 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
16241 Saving Time is not in effect, and negative if the information is not available.
16244 <p><small><a name="note274" href="#note274">274)</a> The range [0, 60] for tm_sec allows for a positive leap second.
16247 <h4><a name="7.23.2" href="#7.23.2">7.23.2 Time manipulation functions</a></h4>
16249 <h5><a name="7.23.2.1" href="#7.23.2.1">7.23.2.1 The clock function</a></h5>
16253 #include <a href="#7.23"><time.h></a>
16254 clock_t clock(void);</pre>
16255 <h6>Description</h6>
16257 The clock function determines the processor time used.
16260 The clock function returns the implementation's best approximation to the processor
16261 time used by the program since the beginning of an implementation-defined era related
16262 only to the program invocation. To determine the time in seconds, the value returned by
16263 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
16264 the processor time used is not available or its value cannot be represented, the function
16265 returns the value (clock_t)(-1).<sup><a href="#note275"><b>275)</b></a></sup>
16268 <p><small><a name="note275" href="#note275">275)</a> In order to measure the time spent in a program, the clock function should be called at the start of
16269 the program and its return value subtracted from the value returned by subsequent calls.
16272 <h5><a name="7.23.2.2" href="#7.23.2.2">7.23.2.2 The difftime function</a></h5>
16276 #include <a href="#7.23"><time.h></a>
16277 double difftime(time_t time1, time_t time0);</pre>
16278 <h6>Description</h6>
16280 The difftime function computes the difference between two calendar times: time1 -
16284 The difftime function returns the difference expressed in seconds as a double.
16291 <h5><a name="7.23.2.3" href="#7.23.2.3">7.23.2.3 The mktime function</a></h5>
16295 #include <a href="#7.23"><time.h></a>
16296 time_t mktime(struct tm *timeptr);</pre>
16297 <h6>Description</h6>
16299 The mktime function converts the broken-down time, expressed as local time, in the
16300 structure pointed to by timeptr into a calendar time value with the same encoding as
16301 that of the values returned by the time function. The original values of the tm_wday
16302 and tm_yday components of the structure are ignored, and the original values of the
16303 other components are not restricted to the ranges indicated above.<sup><a href="#note276"><b>276)</b></a></sup> On successful
16304 completion, the values of the tm_wday and tm_yday components of the structure are
16305 set appropriately, and the other components are set to represent the specified calendar
16306 time, but with their values forced to the ranges indicated above; the final value of
16307 tm_mday is not set until tm_mon and tm_year are determined.
16310 The mktime function returns the specified calendar time encoded as a value of type
16311 time_t. If the calendar time cannot be represented, the function returns the value
16314 EXAMPLE What day of the week is July 4, 2001?
16316 #include <a href="#7.19"><stdio.h></a>
16317 #include <a href="#7.23"><time.h></a>
16318 static const char *const wday[] = {
16319 "Sunday", "Monday", "Tuesday", "Wednesday",
16320 "Thursday", "Friday", "Saturday", "-unknown-"
16322 struct tm time_str;
16330 time_str.tm_year = 2001 - 1900;
16331 time_str.tm_mon = 7 - 1;
16332 time_str.tm_mday = 4;
16333 time_str.tm_hour = 0;
16334 time_str.tm_min = 0;
16335 time_str.tm_sec = 1;
16336 time_str.tm_isdst = -1;
16337 if (mktime(&time_str) == (time_t)(-1))
16338 time_str.tm_wday = 7;
16339 printf("%s\n", wday[time_str.tm_wday]);</pre>
16343 <p><small><a name="note276" href="#note276">276)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
16344 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
16345 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
16348 <h5><a name="7.23.2.4" href="#7.23.2.4">7.23.2.4 The time function</a></h5>
16352 #include <a href="#7.23"><time.h></a>
16353 time_t time(time_t *timer);</pre>
16354 <h6>Description</h6>
16356 The time function determines the current calendar time. The encoding of the value is
16360 The time function returns the implementation's best approximation to the current
16361 calendar time. The value (time_t)(-1) is returned if the calendar time is not
16362 available. If timer is not a null pointer, the return value is also assigned to the object it
16365 <h4><a name="7.23.3" href="#7.23.3">7.23.3 Time conversion functions</a></h4>
16367 Except for the strftime function, these functions each return a pointer to one of two
16368 types of static objects: a broken-down time structure or an array of char. Execution of
16369 any of the functions that return a pointer to one of these object types may overwrite the
16370 information in any object of the same type pointed to by the value returned from any
16371 previous call to any of them. The implementation shall behave as if no other library
16372 functions call these functions.
16374 <h5><a name="7.23.3.1" href="#7.23.3.1">7.23.3.1 The asctime function</a></h5>
16378 #include <a href="#7.23"><time.h></a>
16379 char *asctime(const struct tm *timeptr);</pre>
16380 <h6>Description</h6>
16382 The asctime function converts the broken-down time in the structure pointed to by
16383 timeptr into a string in the form
16386 Sun Sep 16 01:03:52 1973\n\0</pre>
16387 using the equivalent of the following algorithm.
16388 char *asctime(const struct tm *timeptr)
16391 static const char wday_name[7][3] = {
16392 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
16394 static const char mon_name[12][3] = {
16395 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
16396 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
16398 static char result[26];
16399 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
16400 wday_name[timeptr->tm_wday],
16401 mon_name[timeptr->tm_mon],
16402 timeptr->tm_mday, timeptr->tm_hour,
16403 timeptr->tm_min, timeptr->tm_sec,
16404 1900 + timeptr->tm_year);
16405 return result;</pre>
16409 The asctime function returns a pointer to the string.
16411 <h5><a name="7.23.3.2" href="#7.23.3.2">7.23.3.2 The ctime function</a></h5>
16415 #include <a href="#7.23"><time.h></a>
16416 char *ctime(const time_t *timer);</pre>
16417 <h6>Description</h6>
16419 The ctime function converts the calendar time pointed to by timer to local time in the
16420 form of a string. It is equivalent to
16422 asctime(localtime(timer))</pre>
16425 The ctime function returns the pointer returned by the asctime function with that
16426 broken-down time as argument.
16427 <p><b> Forward references</b>: the localtime function (<a href="#7.23.3.4">7.23.3.4</a>).
16430 <h5><a name="7.23.3.3" href="#7.23.3.3">7.23.3.3 The gmtime function</a></h5>
16434 #include <a href="#7.23"><time.h></a>
16435 struct tm *gmtime(const time_t *timer);</pre>
16436 <h6>Description</h6>
16438 The gmtime function converts the calendar time pointed to by timer into a broken-
16439 down time, expressed as UTC.
16442 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
16443 specified time cannot be converted to UTC.
16445 <h5><a name="7.23.3.4" href="#7.23.3.4">7.23.3.4 The localtime function</a></h5>
16449 #include <a href="#7.23"><time.h></a>
16450 struct tm *localtime(const time_t *timer);</pre>
16451 <h6>Description</h6>
16453 The localtime function converts the calendar time pointed to by timer into a
16454 broken-down time, expressed as local time.
16457 The localtime function returns a pointer to the broken-down time, or a null pointer if
16458 the specified time cannot be converted to local time.
16460 <h5><a name="7.23.3.5" href="#7.23.3.5">7.23.3.5 The strftime function</a></h5>
16464 #include <a href="#7.23"><time.h></a>
16465 size_t strftime(char * restrict s,
16467 const char * restrict format,
16468 const struct tm * restrict timeptr);</pre>
16469 <h6>Description</h6>
16471 The strftime function places characters into the array pointed to by s as controlled by
16472 the string pointed to by format. The format shall be a multibyte character sequence,
16473 beginning and ending in its initial shift state. The format string consists of zero or
16474 more conversion specifiers and ordinary multibyte characters. A conversion specifier
16475 consists of a % character, possibly followed by an E or O modifier character (described
16476 below), followed by a character that determines the behavior of the conversion specifier.
16477 All ordinary multibyte characters (including the terminating null character) are copied
16479 unchanged into the array. If copying takes place between objects that overlap, the
16480 behavior is undefined. No more than maxsize characters are placed into the array.
16482 Each conversion specifier is replaced by appropriate characters as described in the
16483 following list. The appropriate characters are determined using the LC_TIME category
16484 of the current locale and by the values of zero or more members of the broken-down time
16485 structure pointed to by timeptr, as specified in brackets in the description. If any of
16486 the specified values is outside the normal range, the characters stored are unspecified.
16487 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
16488 %A is replaced by the locale's full weekday name. [tm_wday]
16489 %b is replaced by the locale's abbreviated month name. [tm_mon]
16490 %B is replaced by the locale's full month name. [tm_mon]
16491 %c is replaced by the locale's appropriate date and time representation. [all specified
16493 in <a href="#7.23.1">7.23.1</a>]</pre>
16494 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
16496 number (00-99). [tm_year]</pre>
16497 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
16498 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
16499 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
16501 preceded by a space. [tm_mday]</pre>
16502 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
16505 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
16507 number (00-99). [tm_year, tm_wday, tm_yday]</pre>
16508 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
16510 [tm_year, tm_wday, tm_yday]</pre>
16511 %h is equivalent to ''%b''. [tm_mon]
16512 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
16513 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
16514 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
16515 %m is replaced by the month as a decimal number (01-12). [tm_mon]
16516 %M is replaced by the minute as a decimal number (00-59). [tm_min]
16517 %n is replaced by a new-line character.
16518 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
16520 12-hour clock. [tm_hour]</pre>
16521 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
16522 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
16523 %S is replaced by the second as a decimal number (00-60). [tm_sec]
16524 %t is replaced by a horizontal-tab character.
16525 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
16529 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
16531 is 1. [tm_wday]</pre>
16532 %U is replaced by the week number of the year (the first Sunday as the first day of week
16534 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]</pre>
16535 %V is replaced by the ISO 8601 week number (see below) as a decimal number
16537 (01-53). [tm_year, tm_wday, tm_yday]</pre>
16538 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
16541 %W is replaced by the week number of the year (the first Monday as the first day of
16543 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]</pre>
16544 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16545 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16546 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
16549 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
16550 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
16552 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
16553 zone is determinable. [tm_isdst]</pre>
16554 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
16556 time zone is determinable. [tm_isdst]</pre>
16557 %% is replaced by %.
16559 Some conversion specifiers can be modified by the inclusion of an E or O modifier
16560 character to indicate an alternative format or specification. If the alternative format or
16561 specification does not exist for the current locale, the modifier is ignored.
16562 %Ec is replaced by the locale's alternative date and time representation.
16563 %EC is replaced by the name of the base year (period) in the locale's alternative
16565 representation.</pre>
16566 %Ex is replaced by the locale's alternative date representation.
16567 %EX is replaced by the locale's alternative time representation.
16568 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
16570 representation.</pre>
16571 %EY is replaced by the locale's full alternative year representation.
16572 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
16574 (filled as needed with leading zeros, or with leading spaces if there is no alternative
16575 symbol for zero).</pre>
16576 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
16578 (filled as needed with leading spaces).</pre>
16579 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
16583 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
16586 %Om is replaced by the month, using the locale's alternative numeric symbols.
16587 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
16588 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
16589 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
16591 representation, where Monday is 1.</pre>
16592 %OU is replaced by the week number, using the locale's alternative numeric symbols.
16593 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
16596 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
16599 %OW is replaced by the week number of the year, using the locale's alternative numeric
16602 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
16606 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
16607 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
16608 which is also the week that includes the first Thursday of the year, and is also the first
16609 week that contains at least four days in the year. If the first Monday of January is the
16610 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
16611 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
16612 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
16613 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
16614 %V is replaced by 01.
16616 If a conversion specifier is not one of the above, the behavior is undefined.
16618 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
16619 following specifiers are:
16620 %a the first three characters of %A.
16621 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
16622 %b the first three characters of %B.
16623 %B one of ''January'', ''February'', ... , ''December''.
16624 %c equivalent to ''%a %b %e %T %Y''.
16625 %p one of ''AM'' or ''PM''.
16626 %r equivalent to ''%I:%M:%S %p''.
16627 %x equivalent to ''%m/%d/%y''.
16628 %X equivalent to %T.
16629 %Z implementation-defined.
16633 If the total number of resulting characters including the terminating null character is not
16634 more than maxsize, the strftime function returns the number of characters placed
16635 into the array pointed to by s not including the terminating null character. Otherwise,
16636 zero is returned and the contents of the array are indeterminate.
16639 <h3><a name="7.24" href="#7.24">7.24 Extended multibyte and wide character utilities <wchar.h></a></h3>
16641 <h4><a name="7.24.1" href="#7.24.1">7.24.1 Introduction</a></h4>
16643 The header <a href="#7.24"><wchar.h></a> declares four data types, one tag, four macros, and many
16644 functions.<sup><a href="#note277"><b>277)</b></a></sup>
16646 The types declared are wchar_t and size_t (both described in <a href="#7.17">7.17</a>);
16649 which is an object type other than an array type that can hold the conversion state
16650 information necessary to convert between sequences of multibyte characters and wide
16654 which is an integer type unchanged by default argument promotions that can hold any
16655 value corresponding to members of the extended character set, as well as at least one
16656 value that does not correspond to any member of the extended character set (see WEOF
16657 below);<sup><a href="#note278"><b>278)</b></a></sup> and
16660 which is declared as an incomplete structure type (the contents are described in <a href="#7.23.1">7.23.1</a>).
16662 The macros defined are NULL (described in <a href="#7.17">7.17</a>); WCHAR_MIN and WCHAR_MAX
16663 (described in <a href="#7.18.3">7.18.3</a>); and
16666 which expands to a constant expression of type wint_t whose value does not
16667 correspond to any member of the extended character set.<sup><a href="#note279"><b>279)</b></a></sup> It is accepted (and returned)
16668 by several functions in this subclause to indicate end-of-file, that is, no more input from a
16669 stream. It is also used as a wide character value that does not correspond to any member
16670 of the extended character set.
16672 The functions declared are grouped as follows:
16674 <li> Functions that perform input and output of wide characters, or multibyte characters,
16676 <li> Functions that provide wide string numeric conversion;
16677 <li> Functions that perform general wide string manipulation;
16681 <li> Functions for wide string date and time conversion; and
16682 <li> Functions that provide extended capabilities for conversion between multibyte and
16683 wide character sequences.
16686 Unless explicitly stated otherwise, if the execution of a function described in this
16687 subclause causes copying to take place between objects that overlap, the behavior is
16691 <p><small><a name="note277" href="#note277">277)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
16693 <p><small><a name="note278" href="#note278">278)</a> wchar_t and wint_t can be the same integer type.
16695 <p><small><a name="note279" href="#note279">279)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
16698 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Formatted wide character input/output functions</a></h4>
16700 The formatted wide character input/output functions shall behave as if there is a sequence
16701 point after the actions associated with each specifier.<sup><a href="#note280"><b>280)</b></a></sup>
16704 <p><small><a name="note280" href="#note280">280)</a> The fwprintf functions perform writes to memory for the %n specifier.
16707 <h5><a name="7.24.2.1" href="#7.24.2.1">7.24.2.1 The fwprintf function</a></h5>
16711 #include <a href="#7.19"><stdio.h></a>
16712 #include <a href="#7.24"><wchar.h></a>
16713 int fwprintf(FILE * restrict stream,
16714 const wchar_t * restrict format, ...);</pre>
16715 <h6>Description</h6>
16717 The fwprintf function writes output to the stream pointed to by stream, under
16718 control of the wide string pointed to by format that specifies how subsequent arguments
16719 are converted for output. If there are insufficient arguments for the format, the behavior
16720 is undefined. If the format is exhausted while arguments remain, the excess arguments
16721 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
16722 when the end of the format string is encountered.
16724 The format is composed of zero or more directives: ordinary wide characters (not %),
16725 which are copied unchanged to the output stream; and conversion specifications, each of
16726 which results in fetching zero or more subsequent arguments, converting them, if
16727 applicable, according to the corresponding conversion specifier, and then writing the
16728 result to the output stream.
16730 Each conversion specification is introduced by the wide character %. After the %, the
16731 following appear in sequence:
16733 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16735 <li> An optional minimum field width. If the converted value has fewer wide characters
16736 than the field width, it is padded with spaces (by default) on the left (or right, if the
16740 left adjustment flag, described later, has been given) to the field width. The field
16741 width takes the form of an asterisk * (described later) or a nonnegative decimal
16742 integer.<sup><a href="#note281"><b>281)</b></a></sup>
16743 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16744 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16745 wide character for a, A, e, E, f, and F conversions, the maximum number of
16746 significant digits for the g and G conversions, or the maximum number of wide
16747 characters to be written for s conversions. The precision takes the form of a period
16748 (.) followed either by an asterisk * (described later) or by an optional decimal
16749 integer; if only the period is specified, the precision is taken as zero. If a precision
16750 appears with any other conversion specifier, the behavior is undefined.
16751 <li> An optional length modifier that specifies the size of the argument.
16752 <li> A conversion specifier wide character that specifies the type of conversion to be
16756 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16757 this case, an int argument supplies the field width or precision. The arguments
16758 specifying field width, or precision, or both, shall appear (in that order) before the
16759 argument (if any) to be converted. A negative field width argument is taken as a - flag
16760 followed by a positive field width. A negative precision argument is taken as if the
16761 precision were omitted.
16763 The flag wide characters and their meanings are:
16764 - The result of the conversion is left-justified within the field. (It is right-justified if
16766 this flag is not specified.)</pre>
16767 + The result of a signed conversion always begins with a plus or minus sign. (It
16769 begins with a sign only when a negative value is converted if this flag is not
16770 specified.)<sup><a href="#note282"><b>282)</b></a></sup></pre>
16771 space If the first wide character of a signed conversion is not a sign, or if a signed
16773 conversion results in no wide characters, a space is prefixed to the result. If the
16774 space and + flags both appear, the space flag is ignored.</pre>
16775 # The result is converted to an ''alternative form''. For o conversion, it increases
16777 the precision, if and only if necessary, to force the first digit of the result to be a
16778 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16779 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,</pre>
16783 and G conversions, the result of converting a floating-point number always
16784 contains a decimal-point wide character, even if no digits follow it. (Normally, a
16785 decimal-point wide character appears in the result of these conversions only if a
16786 digit follows it.) For g and G conversions, trailing zeros are not removed from the
16787 result. For other conversions, the behavior is undefined.</pre>
16788 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16791 (following any indication of sign or base) are used to pad to the field width rather
16792 than performing space padding, except when converting an infinity or NaN. If the
16793 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16794 conversions, if a precision is specified, the 0 flag is ignored. For other
16795 conversions, the behavior is undefined.</pre>
16796 The length modifiers and their meanings are:
16797 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16799 signed char or unsigned char argument (the argument will have
16800 been promoted according to the integer promotions, but its value shall be
16801 converted to signed char or unsigned char before printing); or that
16802 a following n conversion specifier applies to a pointer to a signed char
16804 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16806 short int or unsigned short int argument (the argument will
16807 have been promoted according to the integer promotions, but its value shall
16808 be converted to short int or unsigned short int before printing);
16809 or that a following n conversion specifier applies to a pointer to a short
16810 int argument.</pre>
16811 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16813 long int or unsigned long int argument; that a following n
16814 conversion specifier applies to a pointer to a long int argument; that a
16815 following c conversion specifier applies to a wint_t argument; that a
16816 following s conversion specifier applies to a pointer to a wchar_t
16817 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16819 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16821 long long int or unsigned long long int argument; or that a
16822 following n conversion specifier applies to a pointer to a long long int
16824 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16827 an intmax_t or uintmax_t argument; or that a following n conversion
16828 specifier applies to a pointer to an intmax_t argument.</pre>
16829 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16831 size_t or the corresponding signed integer type argument; or that a
16832 following n conversion specifier applies to a pointer to a signed integer type
16833 corresponding to size_t argument.</pre>
16834 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16836 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16837 following n conversion specifier applies to a pointer to a ptrdiff_t
16839 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16841 applies to a long double argument.</pre>
16842 If a length modifier appears with any conversion specifier other than as specified above,
16843 the behavior is undefined.
16845 The conversion specifiers and their meanings are:
16846 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16848 precision specifies the minimum number of digits to appear; if the value
16849 being converted can be represented in fewer digits, it is expanded with
16850 leading zeros. The default precision is 1. The result of converting a zero
16851 value with a precision of zero is no wide characters.</pre>
16852 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16854 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16855 letters abcdef are used for x conversion and the letters ABCDEF for X
16856 conversion. The precision specifies the minimum number of digits to appear;
16857 if the value being converted can be represented in fewer digits, it is expanded
16858 with leading zeros. The default precision is 1. The result of converting a
16859 zero value with a precision of zero is no wide characters.</pre>
16860 f,F A double argument representing a floating-point number is converted to
16863 decimal notation in the style [-]ddd.ddd, where the number of digits after
16864 the decimal-point wide character is equal to the precision specification. If the
16865 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16866 not specified, no decimal-point wide character appears. If a decimal-point
16867 wide character appears, at least one digit appears before it. The value is
16868 rounded to the appropriate number of digits.
16869 A double argument representing an infinity is converted in one of the styles
16870 [-]inf or [-]infinity -- which style is implementation-defined. A
16871 double argument representing a NaN is converted in one of the styles
16872 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16873 any n-wchar-sequence, is implementation-defined. The F conversion
16874 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16875 nan, respectively.<sup><a href="#note283"><b>283)</b></a></sup></pre>
16876 e,E A double argument representing a floating-point number is converted in the
16878 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16879 argument is nonzero) before the decimal-point wide character and the number
16880 of digits after it is equal to the precision; if the precision is missing, it is taken
16881 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16882 wide character appears. The value is rounded to the appropriate number of
16883 digits. The E conversion specifier produces a number with E instead of e
16884 introducing the exponent. The exponent always contains at least two digits,
16885 and only as many more digits as necessary to represent the exponent. If the
16886 value is zero, the exponent is zero.
16887 A double argument representing an infinity or NaN is converted in the style
16888 of an f or F conversion specifier.</pre>
16889 g,G A double argument representing a floating-point number is converted in
16891 style f or e (or in style F or E in the case of a G conversion specifier),
16892 depending on the value converted and the precision. Let P equal the
16893 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16894 Then, if a conversion with style E would have an exponent of X :
16895 -- if P > X >= -4, the conversion is with style f (or F) and precision
16897 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16898 Finally, unless the # flag is used, any trailing zeros are removed from the
16899 fractional portion of the result and the decimal-point wide character is
16900 removed if there is no fractional portion remaining.
16901 A double argument representing an infinity or NaN is converted in the style
16902 of an f or F conversion specifier.</pre>
16903 a,A A double argument representing a floating-point number is converted in the
16905 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16906 nonzero if the argument is a normalized floating-point number and is
16907 otherwise unspecified) before the decimal-point wide character<sup><a href="#note284"><b>284)</b></a></sup> and the
16908 number of hexadecimal digits after it is equal to the precision; if the precision
16909 is missing and FLT_RADIX is a power of 2, then the precision is sufficient</pre>
16914 for an exact representation of the value; if the precision is missing and
16915 FLT_RADIX is not a power of 2, then the precision is sufficient to
16916 distinguish<sup><a href="#note285"><b>285)</b></a></sup> values of type double, except that trailing zeros may be
16917 omitted; if the precision is zero and the # flag is not specified, no decimal-
16918 point wide character appears. The letters abcdef are used for a conversion
16919 and the letters ABCDEF for A conversion. The A conversion specifier
16920 produces a number with X and P instead of x and p. The exponent always
16921 contains at least one digit, and only as many more digits as necessary to
16922 represent the decimal exponent of 2. If the value is zero, the exponent is
16924 A double argument representing an infinity or NaN is converted in the style
16925 of an f or F conversion specifier.</pre>
16926 c If no l length modifier is present, the int argument is converted to a wide
16928 character as if by calling btowc and the resulting wide character is written.
16929 If an l length modifier is present, the wint_t argument is converted to
16930 wchar_t and written.</pre>
16931 s If no l length modifier is present, the argument shall be a pointer to the initial
16933 element of a character array containing a multibyte character sequence
16934 beginning in the initial shift state. Characters from the array are converted as
16935 if by repeated calls to the mbrtowc function, with the conversion state
16936 described by an mbstate_t object initialized to zero before the first
16937 multibyte character is converted, and written up to (but not including) the
16938 terminating null wide character. If the precision is specified, no more than
16939 that many wide characters are written. If the precision is not specified or is
16940 greater than the size of the converted array, the converted array shall contain a
16941 null wide character.
16942 If an l length modifier is present, the argument shall be a pointer to the initial
16943 element of an array of wchar_t type. Wide characters from the array are
16944 written up to (but not including) a terminating null wide character. If the
16945 precision is specified, no more than that many wide characters are written. If
16946 the precision is not specified or is greater than the size of the array, the array
16947 shall contain a null wide character.</pre>
16948 p The argument shall be a pointer to void. The value of the pointer is
16950 converted to a sequence of printing wide characters, in an implementation-</pre>
16954 defined manner.</pre>
16955 n The argument shall be a pointer to signed integer into which is written the
16957 number of wide characters written to the output stream so far by this call to
16958 fwprintf. No argument is converted, but one is consumed. If the
16959 conversion specification includes any flags, a field width, or a precision, the
16960 behavior is undefined.</pre>
16961 % A % wide character is written. No argument is converted. The complete
16964 conversion specification shall be %%.</pre>
16965 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note286"><b>286)</b></a></sup> If any argument is
16966 not the correct type for the corresponding conversion specification, the behavior is
16969 In no case does a nonexistent or small field width cause truncation of a field; if the result
16970 of a conversion is wider than the field width, the field is expanded to contain the
16973 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16974 to a hexadecimal floating number with the given precision.
16975 <h6> Recommended practice</h6>
16977 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16978 representable in the given precision, the result should be one of the two adjacent numbers
16979 in hexadecimal floating style with the given precision, with the extra stipulation that the
16980 error should have a correct sign for the current rounding direction.
16982 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16983 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note287"><b>287)</b></a></sup> If the number of
16984 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16985 representable with DECIMAL_DIG digits, then the result should be an exact
16986 representation with trailing zeros. Otherwise, the source value is bounded by two
16987 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16988 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16989 the error should have a correct sign for the current rounding direction.
16992 The fwprintf function returns the number of wide characters transmitted, or a negative
16993 value if an output or encoding error occurred.
16996 Environmental limits
16998 The number of wide characters that can be produced by any single conversion shall be at
17001 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
17004 #include <a href="#7.12"><math.h></a>
17005 #include <a href="#7.19"><stdio.h></a>
17006 #include <a href="#7.24"><wchar.h></a>
17008 wchar_t *weekday, *month; // pointers to wide strings
17009 int day, hour, min;
17010 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
17011 weekday, month, day, hour, min);
17012 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));</pre>
17014 <p><b> Forward references</b>: the btowc function (<a href="#7.24.6.1.1">7.24.6.1.1</a>), the mbrtowc function
17015 (<a href="#7.24.6.3.2">7.24.6.3.2</a>).
17018 <p><small><a name="note281" href="#note281">281)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
17020 <p><small><a name="note282" href="#note282">282)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
17021 include a minus sign.
17023 <p><small><a name="note283" href="#note283">283)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
17024 meaning; the # and 0 flag wide characters have no effect.
17026 <p><small><a name="note284" href="#note284">284)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
17027 character so that subsequent digits align to nibble (4-bit) boundaries.
17029 <p><small><a name="note285" href="#note285">285)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
17030 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
17031 might suffice depending on the implementation's scheme for determining the digit to the left of the
17032 decimal-point wide character.
17034 <p><small><a name="note286" href="#note286">286)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17036 <p><small><a name="note287" href="#note287">287)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
17037 given format specifier. The number of significant digits is determined by the format specifier, and in
17038 the case of fixed-point conversion by the source value as well.
17041 <h5><a name="7.24.2.2" href="#7.24.2.2">7.24.2.2 The fwscanf function</a></h5>
17045 #include <a href="#7.19"><stdio.h></a>
17046 #include <a href="#7.24"><wchar.h></a>
17047 int fwscanf(FILE * restrict stream,
17048 const wchar_t * restrict format, ...);</pre>
17049 <h6>Description</h6>
17051 The fwscanf function reads input from the stream pointed to by stream, under
17052 control of the wide string pointed to by format that specifies the admissible input
17053 sequences and how they are to be converted for assignment, using subsequent arguments
17054 as pointers to the objects to receive the converted input. If there are insufficient
17055 arguments for the format, the behavior is undefined. If the format is exhausted while
17056 arguments remain, the excess arguments are evaluated (as always) but are otherwise
17059 The format is composed of zero or more directives: one or more white-space wide
17060 characters, an ordinary wide character (neither % nor a white-space wide character), or a
17061 conversion specification. Each conversion specification is introduced by the wide
17062 character %. After the %, the following appear in sequence:
17064 <li> An optional assignment-suppressing wide character *.
17065 <li> An optional decimal integer greater than zero that specifies the maximum field width
17066 (in wide characters).
17068 <li> An optional length modifier that specifies the size of the receiving object.
17069 <li> A conversion specifier wide character that specifies the type of conversion to be
17073 The fwscanf function executes each directive of the format in turn. If a directive fails,
17074 as detailed below, the function returns. Failures are described as input failures (due to the
17075 occurrence of an encoding error or the unavailability of input characters), or matching
17076 failures (due to inappropriate input).
17078 A directive composed of white-space wide character(s) is executed by reading input up to
17079 the first non-white-space wide character (which remains unread), or until no more wide
17080 characters can be read.
17082 A directive that is an ordinary wide character is executed by reading the next wide
17083 character of the stream. If that wide character differs from the directive, the directive
17084 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
17085 of-file, an encoding error, or a read error prevents a wide character from being read, the
17088 A directive that is a conversion specification defines a set of matching input sequences, as
17089 described below for each specifier. A conversion specification is executed in the
17092 Input white-space wide characters (as specified by the iswspace function) are skipped,
17093 unless the specification includes a [, c, or n specifier.<sup><a href="#note288"><b>288)</b></a></sup>
17095 An input item is read from the stream, unless the specification includes an n specifier. An
17096 input item is defined as the longest sequence of input wide characters which does not
17097 exceed any specified field width and which is, or is a prefix of, a matching input
17098 sequence.<sup><a href="#note289"><b>289)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
17099 length of the input item is zero, the execution of the directive fails; this condition is a
17100 matching failure unless end-of-file, an encoding error, or a read error prevented input
17101 from the stream, in which case it is an input failure.
17103 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
17104 count of input wide characters) is converted to a type appropriate to the conversion
17105 specifier. If the input item is not a matching sequence, the execution of the directive fails:
17106 this condition is a matching failure. Unless assignment suppression was indicated by a *,
17107 the result of the conversion is placed in the object pointed to by the first argument
17108 following the format argument that has not already received a conversion result. If this
17112 object does not have an appropriate type, or if the result of the conversion cannot be
17113 represented in the object, the behavior is undefined.
17115 The length modifiers and their meanings are:
17116 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17118 to an argument with type pointer to signed char or unsigned char.</pre>
17119 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17121 to an argument with type pointer to short int or unsigned short
17123 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17125 to an argument with type pointer to long int or unsigned long
17126 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
17127 an argument with type pointer to double; or that a following c, s, or [
17128 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
17129 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17131 to an argument with type pointer to long long int or unsigned
17132 long long int.</pre>
17133 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17135 to an argument with type pointer to intmax_t or uintmax_t.</pre>
17136 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17138 to an argument with type pointer to size_t or the corresponding signed
17139 integer type.</pre>
17140 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17142 to an argument with type pointer to ptrdiff_t or the corresponding
17143 unsigned integer type.</pre>
17144 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
17146 applies to an argument with type pointer to long double.</pre>
17147 If a length modifier appears with any conversion specifier other than as specified above,
17148 the behavior is undefined.
17150 The conversion specifiers and their meanings are:
17151 d Matches an optionally signed decimal integer, whose format is the same as
17153 expected for the subject sequence of the wcstol function with the value 10
17154 for the base argument. The corresponding argument shall be a pointer to
17155 signed integer.</pre>
17156 i Matches an optionally signed integer, whose format is the same as expected
17159 for the subject sequence of the wcstol function with the value 0 for the
17160 base argument. The corresponding argument shall be a pointer to signed
17162 o Matches an optionally signed octal integer, whose format is the same as
17164 expected for the subject sequence of the wcstoul function with the value 8
17165 for the base argument. The corresponding argument shall be a pointer to
17166 unsigned integer.</pre>
17167 u Matches an optionally signed decimal integer, whose format is the same as
17169 expected for the subject sequence of the wcstoul function with the value 10
17170 for the base argument. The corresponding argument shall be a pointer to
17171 unsigned integer.</pre>
17172 x Matches an optionally signed hexadecimal integer, whose format is the same
17174 as expected for the subject sequence of the wcstoul function with the value
17175 16 for the base argument. The corresponding argument shall be a pointer to
17176 unsigned integer.</pre>
17177 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
17179 format is the same as expected for the subject sequence of the wcstod
17180 function. The corresponding argument shall be a pointer to floating.</pre>
17181 c Matches a sequence of wide characters of exactly the number specified by the
17183 field width (1 if no field width is present in the directive).
17184 If no l length modifier is present, characters from the input field are
17185 converted as if by repeated calls to the wcrtomb function, with the
17186 conversion state described by an mbstate_t object initialized to zero
17187 before the first wide character is converted. The corresponding argument
17188 shall be a pointer to the initial element of a character array large enough to
17189 accept the sequence. No null character is added.
17190 If an l length modifier is present, the corresponding argument shall be a
17191 pointer to the initial element of an array of wchar_t large enough to accept
17192 the sequence. No null wide character is added.</pre>
17193 s Matches a sequence of non-white-space wide characters.
17196 If no l length modifier is present, characters from the input field are
17197 converted as if by repeated calls to the wcrtomb function, with the
17198 conversion state described by an mbstate_t object initialized to zero
17199 before the first wide character is converted. The corresponding argument
17200 shall be a pointer to the initial element of a character array large enough to
17201 accept the sequence and a terminating null character, which will be added
17203 If an l length modifier is present, the corresponding argument shall be a
17204 pointer to the initial element of an array of wchar_t large enough to accept
17205 the sequence and the terminating null wide character, which will be added
17206 automatically.</pre>
17207 [ Matches a nonempty sequence of wide characters from a set of expected
17209 characters (the scanset).
17210 If no l length modifier is present, characters from the input field are
17211 converted as if by repeated calls to the wcrtomb function, with the
17212 conversion state described by an mbstate_t object initialized to zero
17213 before the first wide character is converted. The corresponding argument
17214 shall be a pointer to the initial element of a character array large enough to
17215 accept the sequence and a terminating null character, which will be added
17217 If an l length modifier is present, the corresponding argument shall be a
17218 pointer to the initial element of an array of wchar_t large enough to accept
17219 the sequence and the terminating null wide character, which will be added
17221 The conversion specifier includes all subsequent wide characters in the
17222 format string, up to and including the matching right bracket (]). The wide
17223 characters between the brackets (the scanlist) compose the scanset, unless the
17224 wide character after the left bracket is a circumflex (^), in which case the
17225 scanset contains all wide characters that do not appear in the scanlist between
17226 the circumflex and the right bracket. If the conversion specifier begins with
17227 [] or [^], the right bracket wide character is in the scanlist and the next
17228 following right bracket wide character is the matching right bracket that ends
17229 the specification; otherwise the first following right bracket wide character is
17230 the one that ends the specification. If a - wide character is in the scanlist and
17231 is not the first, nor the second where the first wide character is a ^, nor the
17232 last character, the behavior is implementation-defined.</pre>
17233 p Matches an implementation-defined set of sequences, which should be the
17235 same as the set of sequences that may be produced by the %p conversion of
17236 the fwprintf function. The corresponding argument shall be a pointer to a
17237 pointer to void. The input item is converted to a pointer value in an
17238 implementation-defined manner. If the input item is a value converted earlier
17239 during the same program execution, the pointer that results shall compare
17240 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
17241 n No input is consumed. The corresponding argument shall be a pointer to
17244 signed integer into which is to be written the number of wide characters read
17245 from the input stream so far by this call to the fwscanf function. Execution
17246 of a %n directive does not increment the assignment count returned at the
17247 completion of execution of the fwscanf function. No argument is
17248 converted, but one is consumed. If the conversion specification includes an
17249 assignment-suppressing wide character or a field width, the behavior is
17251 % Matches a single % wide character; no conversion or assignment occurs. The
17254 complete conversion specification shall be %%.</pre>
17255 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note290"><b>290)</b></a></sup>
17257 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
17258 respectively, a, e, f, g, and x.
17260 Trailing white space (including new-line wide characters) is left unread unless matched
17261 by a directive. The success of literal matches and suppressed assignments is not directly
17262 determinable other than via the %n directive.
17265 The fwscanf function returns the value of the macro EOF if an input failure occurs
17266 before any conversion. Otherwise, the function returns the number of input items
17267 assigned, which can be fewer than provided for, or even zero, in the event of an early
17270 EXAMPLE 1 The call:
17272 #include <a href="#7.19"><stdio.h></a>
17273 #include <a href="#7.24"><wchar.h></a>
17275 int n, i; float x; wchar_t name[50];
17276 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);</pre>
17277 with the input line:
17279 25 54.32E-1 thompson</pre>
17280 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
17284 EXAMPLE 2 The call:
17286 #include <a href="#7.19"><stdio.h></a>
17287 #include <a href="#7.24"><wchar.h></a>
17289 int i; float x; double y;
17290 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);</pre>
17293 56789 0123 56a72</pre>
17294 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
17295 56.0. The next wide character read from the input stream will be a.
17299 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.24.4.1.1">7.24.4.1.1</a>), the
17300 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.24.4.1.2">7.24.4.1.2</a>), the wcrtomb
17301 function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
17304 <p><small><a name="note288" href="#note288">288)</a> These white-space wide characters are not counted against a specified field width.
17306 <p><small><a name="note289" href="#note289">289)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
17307 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
17309 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17312 <h5><a name="7.24.2.3" href="#7.24.2.3">7.24.2.3 The swprintf function</a></h5>
17316 #include <a href="#7.24"><wchar.h></a>
17317 int swprintf(wchar_t * restrict s,
17319 const wchar_t * restrict format, ...);</pre>
17320 <h6>Description</h6>
17322 The swprintf function is equivalent to fwprintf, except that the argument s
17323 specifies an array of wide characters into which the generated output is to be written,
17324 rather than written to a stream. No more than n wide characters are written, including a
17325 terminating null wide character, which is always added (unless n is zero).
17328 The swprintf function returns the number of wide characters written in the array, not
17329 counting the terminating null wide character, or a negative value if an encoding error
17330 occurred or if n or more wide characters were requested to be written.
17332 <h5><a name="7.24.2.4" href="#7.24.2.4">7.24.2.4 The swscanf function</a></h5>
17336 #include <a href="#7.24"><wchar.h></a>
17337 int swscanf(const wchar_t * restrict s,
17338 const wchar_t * restrict format, ...);</pre>
17339 <h6>Description</h6>
17341 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
17342 wide string from which the input is to be obtained, rather than from a stream. Reaching
17343 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
17347 The swscanf function returns the value of the macro EOF if an input failure occurs
17348 before any conversion. Otherwise, the swscanf function returns the number of input
17349 items assigned, which can be fewer than provided for, or even zero, in the event of an
17350 early matching failure.
17353 <h5><a name="7.24.2.5" href="#7.24.2.5">7.24.2.5 The vfwprintf function</a></h5>
17357 #include <a href="#7.15"><stdarg.h></a>
17358 #include <a href="#7.19"><stdio.h></a>
17359 #include <a href="#7.24"><wchar.h></a>
17360 int vfwprintf(FILE * restrict stream,
17361 const wchar_t * restrict format,
17362 va_list arg);</pre>
17363 <h6>Description</h6>
17365 The vfwprintf function is equivalent to fwprintf, with the variable argument list
17366 replaced by arg, which shall have been initialized by the va_start macro (and
17367 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
17368 va_end macro.<sup><a href="#note291"><b>291)</b></a></sup>
17371 The vfwprintf function returns the number of wide characters transmitted, or a
17372 negative value if an output or encoding error occurred.
17374 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
17377 #include <a href="#7.15"><stdarg.h></a>
17378 #include <a href="#7.19"><stdio.h></a>
17379 #include <a href="#7.24"><wchar.h></a>
17380 void error(char *function_name, wchar_t *format, ...)
17383 va_start(args, format);
17384 // print out name of function causing error
17385 fwprintf(stderr, L"ERROR in %s: ", function_name);
17386 // print out remainder of message
17387 vfwprintf(stderr, format, args);
17397 <p><small><a name="note291" href="#note291">291)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
17398 invoke the va_arg macro, the value of arg after the return is indeterminate.
17401 <h5><a name="7.24.2.6" href="#7.24.2.6">7.24.2.6 The vfwscanf function</a></h5>
17405 #include <a href="#7.15"><stdarg.h></a>
17406 #include <a href="#7.19"><stdio.h></a>
17407 #include <a href="#7.24"><wchar.h></a>
17408 int vfwscanf(FILE * restrict stream,
17409 const wchar_t * restrict format,
17410 va_list arg);</pre>
17411 <h6>Description</h6>
17413 The vfwscanf function is equivalent to fwscanf, with the variable argument list
17414 replaced by arg, which shall have been initialized by the va_start macro (and
17415 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
17419 The vfwscanf function returns the value of the macro EOF if an input failure occurs
17420 before any conversion. Otherwise, the vfwscanf function returns the number of input
17421 items assigned, which can be fewer than provided for, or even zero, in the event of an
17422 early matching failure.
17424 <h5><a name="7.24.2.7" href="#7.24.2.7">7.24.2.7 The vswprintf function</a></h5>
17428 #include <a href="#7.15"><stdarg.h></a>
17429 #include <a href="#7.24"><wchar.h></a>
17430 int vswprintf(wchar_t * restrict s,
17432 const wchar_t * restrict format,
17433 va_list arg);</pre>
17434 <h6>Description</h6>
17436 The vswprintf function is equivalent to swprintf, with the variable argument list
17437 replaced by arg, which shall have been initialized by the va_start macro (and
17438 possibly subsequent va_arg calls). The vswprintf function does not invoke the
17442 The vswprintf function returns the number of wide characters written in the array, not
17443 counting the terminating null wide character, or a negative value if an encoding error
17444 occurred or if n or more wide characters were requested to be generated.
17447 <h5><a name="7.24.2.8" href="#7.24.2.8">7.24.2.8 The vswscanf function</a></h5>
17451 #include <a href="#7.15"><stdarg.h></a>
17452 #include <a href="#7.24"><wchar.h></a>
17453 int vswscanf(const wchar_t * restrict s,
17454 const wchar_t * restrict format,
17455 va_list arg);</pre>
17456 <h6>Description</h6>
17458 The vswscanf function is equivalent to swscanf, with the variable argument list
17459 replaced by arg, which shall have been initialized by the va_start macro (and
17460 possibly subsequent va_arg calls). The vswscanf function does not invoke the
17464 The vswscanf function returns the value of the macro EOF if an input failure occurs
17465 before any conversion. Otherwise, the vswscanf function returns the number of input
17466 items assigned, which can be fewer than provided for, or even zero, in the event of an
17467 early matching failure.
17469 <h5><a name="7.24.2.9" href="#7.24.2.9">7.24.2.9 The vwprintf function</a></h5>
17473 #include <a href="#7.15"><stdarg.h></a>
17474 #include <a href="#7.24"><wchar.h></a>
17475 int vwprintf(const wchar_t * restrict format,
17476 va_list arg);</pre>
17477 <h6>Description</h6>
17479 The vwprintf function is equivalent to wprintf, with the variable argument list
17480 replaced by arg, which shall have been initialized by the va_start macro (and
17481 possibly subsequent va_arg calls). The vwprintf function does not invoke the
17485 The vwprintf function returns the number of wide characters transmitted, or a negative
17486 value if an output or encoding error occurred.
17489 <h5><a name="7.24.2.10" href="#7.24.2.10">7.24.2.10 The vwscanf function</a></h5>
17493 #include <a href="#7.15"><stdarg.h></a>
17494 #include <a href="#7.24"><wchar.h></a>
17495 int vwscanf(const wchar_t * restrict format,
17496 va_list arg);</pre>
17497 <h6>Description</h6>
17499 The vwscanf function is equivalent to wscanf, with the variable argument list
17500 replaced by arg, which shall have been initialized by the va_start macro (and
17501 possibly subsequent va_arg calls). The vwscanf function does not invoke the
17505 The vwscanf function returns the value of the macro EOF if an input failure occurs
17506 before any conversion. Otherwise, the vwscanf function returns the number of input
17507 items assigned, which can be fewer than provided for, or even zero, in the event of an
17508 early matching failure.
17510 <h5><a name="7.24.2.11" href="#7.24.2.11">7.24.2.11 The wprintf function</a></h5>
17514 #include <a href="#7.24"><wchar.h></a>
17515 int wprintf(const wchar_t * restrict format, ...);</pre>
17516 <h6>Description</h6>
17518 The wprintf function is equivalent to fwprintf with the argument stdout
17519 interposed before the arguments to wprintf.
17522 The wprintf function returns the number of wide characters transmitted, or a negative
17523 value if an output or encoding error occurred.
17525 <h5><a name="7.24.2.12" href="#7.24.2.12">7.24.2.12 The wscanf function</a></h5>
17529 #include <a href="#7.24"><wchar.h></a>
17530 int wscanf(const wchar_t * restrict format, ...);</pre>
17531 <h6>Description</h6>
17533 The wscanf function is equivalent to fwscanf with the argument stdin interposed
17534 before the arguments to wscanf.
17538 The wscanf function returns the value of the macro EOF if an input failure occurs
17539 before any conversion. Otherwise, the wscanf function returns the number of input
17540 items assigned, which can be fewer than provided for, or even zero, in the event of an
17541 early matching failure.
17543 <h4><a name="7.24.3" href="#7.24.3">7.24.3 Wide character input/output functions</a></h4>
17545 <h5><a name="7.24.3.1" href="#7.24.3.1">7.24.3.1 The fgetwc function</a></h5>
17549 #include <a href="#7.19"><stdio.h></a>
17550 #include <a href="#7.24"><wchar.h></a>
17551 wint_t fgetwc(FILE *stream);</pre>
17552 <h6>Description</h6>
17554 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17555 next wide character is present, the fgetwc function obtains that wide character as a
17556 wchar_t converted to a wint_t and advances the associated file position indicator for
17557 the stream (if defined).
17560 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17561 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
17562 the fgetwc function returns the next wide character from the input stream pointed to by
17563 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
17564 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
17565 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note292"><b>292)</b></a></sup>
17568 <p><small><a name="note292" href="#note292">292)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17569 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
17572 <h5><a name="7.24.3.2" href="#7.24.3.2">7.24.3.2 The fgetws function</a></h5>
17576 #include <a href="#7.19"><stdio.h></a>
17577 #include <a href="#7.24"><wchar.h></a>
17578 wchar_t *fgetws(wchar_t * restrict s,
17579 int n, FILE * restrict stream);</pre>
17580 <h6>Description</h6>
17582 The fgetws function reads at most one less than the number of wide characters
17583 specified by n from the stream pointed to by stream into the array pointed to by s. No
17587 additional wide characters are read after a new-line wide character (which is retained) or
17588 after end-of-file. A null wide character is written immediately after the last wide
17589 character read into the array.
17592 The fgetws function returns s if successful. If end-of-file is encountered and no
17593 characters have been read into the array, the contents of the array remain unchanged and a
17594 null pointer is returned. If a read or encoding error occurs during the operation, the array
17595 contents are indeterminate and a null pointer is returned.
17597 <h5><a name="7.24.3.3" href="#7.24.3.3">7.24.3.3 The fputwc function</a></h5>
17601 #include <a href="#7.19"><stdio.h></a>
17602 #include <a href="#7.24"><wchar.h></a>
17603 wint_t fputwc(wchar_t c, FILE *stream);</pre>
17604 <h6>Description</h6>
17606 The fputwc function writes the wide character specified by c to the output stream
17607 pointed to by stream, at the position indicated by the associated file position indicator
17608 for the stream (if defined), and advances the indicator appropriately. If the file cannot
17609 support positioning requests, or if the stream was opened with append mode, the
17610 character is appended to the output stream.
17613 The fputwc function returns the wide character written. If a write error occurs, the
17614 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
17615 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
17617 <h5><a name="7.24.3.4" href="#7.24.3.4">7.24.3.4 The fputws function</a></h5>
17621 #include <a href="#7.19"><stdio.h></a>
17622 #include <a href="#7.24"><wchar.h></a>
17623 int fputws(const wchar_t * restrict s,
17624 FILE * restrict stream);</pre>
17625 <h6>Description</h6>
17627 The fputws function writes the wide string pointed to by s to the stream pointed to by
17628 stream. The terminating null wide character is not written.
17631 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
17632 returns a nonnegative value.
17635 <h5><a name="7.24.3.5" href="#7.24.3.5">7.24.3.5 The fwide function</a></h5>
17639 #include <a href="#7.19"><stdio.h></a>
17640 #include <a href="#7.24"><wchar.h></a>
17641 int fwide(FILE *stream, int mode);</pre>
17642 <h6>Description</h6>
17644 The fwide function determines the orientation of the stream pointed to by stream. If
17645 mode is greater than zero, the function first attempts to make the stream wide oriented. If
17646 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note293"><b>293)</b></a></sup>
17647 Otherwise, mode is zero and the function does not alter the orientation of the stream.
17650 The fwide function returns a value greater than zero if, after the call, the stream has
17651 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
17652 stream has no orientation.
17655 <p><small><a name="note293" href="#note293">293)</a> If the orientation of the stream has already been determined, fwide does not change it.
17658 <h5><a name="7.24.3.6" href="#7.24.3.6">7.24.3.6 The getwc function</a></h5>
17662 #include <a href="#7.19"><stdio.h></a>
17663 #include <a href="#7.24"><wchar.h></a>
17664 wint_t getwc(FILE *stream);</pre>
17665 <h6>Description</h6>
17667 The getwc function is equivalent to fgetwc, except that if it is implemented as a
17668 macro, it may evaluate stream more than once, so the argument should never be an
17669 expression with side effects.
17672 The getwc function returns the next wide character from the input stream pointed to by
17675 <h5><a name="7.24.3.7" href="#7.24.3.7">7.24.3.7 The getwchar function</a></h5>
17679 #include <a href="#7.24"><wchar.h></a>
17680 wint_t getwchar(void);</pre>
17686 <h6>Description</h6>
17688 The getwchar function is equivalent to getwc with the argument stdin.
17691 The getwchar function returns the next wide character from the input stream pointed to
17694 <h5><a name="7.24.3.8" href="#7.24.3.8">7.24.3.8 The putwc function</a></h5>
17698 #include <a href="#7.19"><stdio.h></a>
17699 #include <a href="#7.24"><wchar.h></a>
17700 wint_t putwc(wchar_t c, FILE *stream);</pre>
17701 <h6>Description</h6>
17703 The putwc function is equivalent to fputwc, except that if it is implemented as a
17704 macro, it may evaluate stream more than once, so that argument should never be an
17705 expression with side effects.
17708 The putwc function returns the wide character written, or WEOF.
17710 <h5><a name="7.24.3.9" href="#7.24.3.9">7.24.3.9 The putwchar function</a></h5>
17714 #include <a href="#7.24"><wchar.h></a>
17715 wint_t putwchar(wchar_t c);</pre>
17716 <h6>Description</h6>
17718 The putwchar function is equivalent to putwc with the second argument stdout.
17721 The putwchar function returns the character written, or WEOF.
17723 <h5><a name="7.24.3.10" href="#7.24.3.10">7.24.3.10 The ungetwc function</a></h5>
17727 #include <a href="#7.19"><stdio.h></a>
17728 #include <a href="#7.24"><wchar.h></a>
17729 wint_t ungetwc(wint_t c, FILE *stream);</pre>
17730 <h6>Description</h6>
17732 The ungetwc function pushes the wide character specified by c back onto the input
17733 stream pointed to by stream. Pushed-back wide characters will be returned by
17734 subsequent reads on that stream in the reverse order of their pushing. A successful
17736 intervening call (with the stream pointed to by stream) to a file positioning function
17737 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
17738 stream. The external storage corresponding to the stream is unchanged.
17740 One wide character of pushback is guaranteed, even if the call to the ungetwc function
17741 follows just after a call to a formatted wide character input function fwscanf,
17742 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
17743 on the same stream without an intervening read or file positioning operation on that
17744 stream, the operation may fail.
17746 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
17749 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
17750 The value of the file position indicator for the stream after reading or discarding all
17751 pushed-back wide characters is the same as it was before the wide characters were pushed
17752 back. For a text or binary stream, the value of its file position indicator after a successful
17753 call to the ungetwc function is unspecified until all pushed-back wide characters are
17757 The ungetwc function returns the wide character pushed back, or WEOF if the operation
17760 <h4><a name="7.24.4" href="#7.24.4">7.24.4 General wide string utilities</a></h4>
17762 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide string
17763 manipulation. Various methods are used for determining the lengths of the arrays, but in
17764 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
17765 array. If an array is accessed beyond the end of an object, the behavior is undefined.
17767 Where an argument declared as size_t n determines the length of the array for a
17768 function, n can have the value zero on a call to that function. Unless explicitly stated
17769 otherwise in the description of a particular function in this subclause, pointer arguments
17770 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
17771 function that locates a wide character finds no occurrence, a function that compares two
17772 wide character sequences returns zero, and a function that copies wide characters copies
17773 zero wide characters.
17776 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 Wide string numeric conversion functions</a></h5>
17778 <h5><a name="7.24.4.1.1" href="#7.24.4.1.1">7.24.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
17782 #include <a href="#7.24"><wchar.h></a>
17783 double wcstod(const wchar_t * restrict nptr,
17784 wchar_t ** restrict endptr);
17785 float wcstof(const wchar_t * restrict nptr,
17786 wchar_t ** restrict endptr);
17787 long double wcstold(const wchar_t * restrict nptr,
17788 wchar_t ** restrict endptr);</pre>
17789 <h6>Description</h6>
17791 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
17792 string pointed to by nptr to double, float, and long double representation,
17793 respectively. First, they decompose the input string into three parts: an initial, possibly
17794 empty, sequence of white-space wide characters (as specified by the iswspace
17795 function), a subject sequence resembling a floating-point constant or representing an
17796 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
17797 including the terminating null wide character of the input wide string. Then, they attempt
17798 to convert the subject sequence to a floating-point number, and return the result.
17800 The expected form of the subject sequence is an optional plus or minus sign, then one of
17803 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
17804 character, then an optional exponent part as defined for the corresponding single-byte
17805 characters in <a href="#6.4.4.2">6.4.4.2</a>;
17806 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
17807 decimal-point wide character, then an optional binary exponent part as defined in
17808 <a href="#6.4.4.2">6.4.4.2</a>;
17809 <li> INF or INFINITY, or any other wide string equivalent except for case
17810 <li> NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
17811 case in the NAN part, where:
17816 n-wchar-sequence digit
17817 n-wchar-sequence nondigit</pre>
17819 The subject sequence is defined as the longest initial subsequence of the input wide
17820 string, starting with the first non-white-space wide character, that is of the expected form.
17822 The subject sequence contains no wide characters if the input wide string is not of the
17825 If the subject sequence has the expected form for a floating-point number, the sequence of
17826 wide characters starting with the first digit or the decimal-point wide character
17827 (whichever occurs first) is interpreted as a floating constant according to the rules of
17828 <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
17829 if neither an exponent part nor a decimal-point wide character appears in a decimal
17830 floating point number, or if a binary exponent part does not appear in a hexadecimal
17831 floating point number, an exponent part of the appropriate type with value zero is
17832 assumed to follow the last digit in the string. If the subject sequence begins with a minus
17833 sign, the sequence is interpreted as negated.<sup><a href="#note294"><b>294)</b></a></sup> A wide character sequence INF or
17834 INFINITY is interpreted as an infinity, if representable in the return type, else like a
17835 floating constant that is too large for the range of the return type. A wide character
17836 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
17837 in the return type, else like a subject sequence part that does not have the expected form;
17838 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note295"><b>295)</b></a></sup> A pointer to the
17839 final wide string is stored in the object pointed to by endptr, provided that endptr is
17840 not a null pointer.
17842 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17843 value resulting from the conversion is correctly rounded.
17845 In other than the "C" locale, additional locale-specific subject sequence forms may be
17848 If the subject sequence is empty or does not have the expected form, no conversion is
17849 performed; the value of nptr is stored in the object pointed to by endptr, provided
17850 that endptr is not a null pointer.
17851 <h6> Recommended practice</h6>
17853 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17854 the result is not exactly representable, the result should be one of the two numbers in the
17855 appropriate internal format that are adjacent to the hexadecimal floating source value,
17856 with the extra stipulation that the error should have a correct sign for the current rounding
17863 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17864 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17865 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17866 consider the two bounding, adjacent decimal strings L and U, both having
17867 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17868 The result should be one of the (equal or adjacent) values that would be obtained by
17869 correctly rounding L and U according to the current rounding direction, with the extra
17870 stipulation that the error with respect to D should have a correct sign for the current
17871 rounding direction.<sup><a href="#note296"><b>296)</b></a></sup>
17874 The functions return the converted value, if any. If no conversion could be performed,
17875 zero is returned. If the correct value is outside the range of representable values, plus or
17876 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
17877 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
17878 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
17879 than the smallest normalized positive number in the return type; whether errno acquires
17880 the value ERANGE is implementation-defined.
17888 <p><small><a name="note294" href="#note294">294)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
17889 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17890 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17891 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17893 <p><small><a name="note295" href="#note295">295)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
17894 the NaN's significand.
17896 <p><small><a name="note296" href="#note296">296)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
17897 to the same internal floating value, but if not will round to adjacent values.
17900 <h5><a name="7.24.4.1.2" href="#7.24.4.1.2">7.24.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
17904 #include <a href="#7.24"><wchar.h></a>
17906 const wchar_t * restrict nptr,
17907 wchar_t ** restrict endptr,
17909 long long int wcstoll(
17910 const wchar_t * restrict nptr,
17911 wchar_t ** restrict endptr,
17913 unsigned long int wcstoul(
17914 const wchar_t * restrict nptr,
17915 wchar_t ** restrict endptr,
17917 unsigned long long int wcstoull(
17918 const wchar_t * restrict nptr,
17919 wchar_t ** restrict endptr,
17921 <h6>Description</h6>
17923 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
17924 portion of the wide string pointed to by nptr to long int, long long int,
17925 unsigned long int, and unsigned long long int representation,
17926 respectively. First, they decompose the input string into three parts: an initial, possibly
17927 empty, sequence of white-space wide characters (as specified by the iswspace
17928 function), a subject sequence resembling an integer represented in some radix determined
17929 by the value of base, and a final wide string of one or more unrecognized wide
17930 characters, including the terminating null wide character of the input wide string. Then,
17931 they attempt to convert the subject sequence to an integer, and return the result.
17933 If the value of base is zero, the expected form of the subject sequence is that of an
17934 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
17935 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
17936 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
17937 is a sequence of letters and digits representing an integer with the radix specified by
17938 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
17939 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
17940 letters and digits whose ascribed values are less than that of base are permitted. If the
17941 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
17942 of letters and digits, following the sign if present.
17945 The subject sequence is defined as the longest initial subsequence of the input wide
17946 string, starting with the first non-white-space wide character, that is of the expected form.
17947 The subject sequence contains no wide characters if the input wide string is empty or
17948 consists entirely of white space, or if the first non-white-space wide character is other
17949 than a sign or a permissible letter or digit.
17951 If the subject sequence has the expected form and the value of base is zero, the sequence
17952 of wide characters starting with the first digit is interpreted as an integer constant
17953 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
17954 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
17955 letter its value as given above. If the subject sequence begins with a minus sign, the value
17956 resulting from the conversion is negated (in the return type). A pointer to the final wide
17957 string is stored in the object pointed to by endptr, provided that endptr is not a null
17960 In other than the "C" locale, additional locale-specific subject sequence forms may be
17963 If the subject sequence is empty or does not have the expected form, no conversion is
17964 performed; the value of nptr is stored in the object pointed to by endptr, provided
17965 that endptr is not a null pointer.
17968 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
17969 value, if any. If no conversion could be performed, zero is returned. If the correct value
17970 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17971 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17972 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17974 <h5><a name="7.24.4.2" href="#7.24.4.2">7.24.4.2 Wide string copying functions</a></h5>
17976 <h5><a name="7.24.4.2.1" href="#7.24.4.2.1">7.24.4.2.1 The wcscpy function</a></h5>
17980 #include <a href="#7.24"><wchar.h></a>
17981 wchar_t *wcscpy(wchar_t * restrict s1,
17982 const wchar_t * restrict s2);</pre>
17983 <h6>Description</h6>
17985 The wcscpy function copies the wide string pointed to by s2 (including the terminating
17986 null wide character) into the array pointed to by s1.
17989 The wcscpy function returns the value of s1.
17992 <h5><a name="7.24.4.2.2" href="#7.24.4.2.2">7.24.4.2.2 The wcsncpy function</a></h5>
17996 #include <a href="#7.24"><wchar.h></a>
17997 wchar_t *wcsncpy(wchar_t * restrict s1,
17998 const wchar_t * restrict s2,
18000 <h6>Description</h6>
18002 The wcsncpy function copies not more than n wide characters (those that follow a null
18003 wide character are not copied) from the array pointed to by s2 to the array pointed to by
18004 s1.<sup><a href="#note297"><b>297)</b></a></sup>
18006 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
18007 wide characters are appended to the copy in the array pointed to by s1, until n wide
18008 characters in all have been written.
18011 The wcsncpy function returns the value of s1.
18014 <p><small><a name="note297" href="#note297">297)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
18015 result will not be null-terminated.
18018 <h5><a name="7.24.4.2.3" href="#7.24.4.2.3">7.24.4.2.3 The wmemcpy function</a></h5>
18022 #include <a href="#7.24"><wchar.h></a>
18023 wchar_t *wmemcpy(wchar_t * restrict s1,
18024 const wchar_t * restrict s2,
18026 <h6>Description</h6>
18028 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
18029 object pointed to by s1.
18032 The wmemcpy function returns the value of s1.
18039 <h5><a name="7.24.4.2.4" href="#7.24.4.2.4">7.24.4.2.4 The wmemmove function</a></h5>
18043 #include <a href="#7.24"><wchar.h></a>
18044 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
18046 <h6>Description</h6>
18048 The wmemmove function copies n wide characters from the object pointed to by s2 to
18049 the object pointed to by s1. Copying takes place as if the n wide characters from the
18050 object pointed to by s2 are first copied into a temporary array of n wide characters that
18051 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
18052 the temporary array are copied into the object pointed to by s1.
18055 The wmemmove function returns the value of s1.
18057 <h5><a name="7.24.4.3" href="#7.24.4.3">7.24.4.3 Wide string concatenation functions</a></h5>
18059 <h5><a name="7.24.4.3.1" href="#7.24.4.3.1">7.24.4.3.1 The wcscat function</a></h5>
18063 #include <a href="#7.24"><wchar.h></a>
18064 wchar_t *wcscat(wchar_t * restrict s1,
18065 const wchar_t * restrict s2);</pre>
18066 <h6>Description</h6>
18068 The wcscat function appends a copy of the wide string pointed to by s2 (including the
18069 terminating null wide character) to the end of the wide string pointed to by s1. The initial
18070 wide character of s2 overwrites the null wide character at the end of s1.
18073 The wcscat function returns the value of s1.
18075 <h5><a name="7.24.4.3.2" href="#7.24.4.3.2">7.24.4.3.2 The wcsncat function</a></h5>
18079 #include <a href="#7.24"><wchar.h></a>
18080 wchar_t *wcsncat(wchar_t * restrict s1,
18081 const wchar_t * restrict s2,
18083 <h6>Description</h6>
18085 The wcsncat function appends not more than n wide characters (a null wide character
18086 and those that follow it are not appended) from the array pointed to by s2 to the end of
18088 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
18089 wide character at the end of s1. A terminating null wide character is always appended to
18090 the result.<sup><a href="#note298"><b>298)</b></a></sup>
18093 The wcsncat function returns the value of s1.
18096 <p><small><a name="note298" href="#note298">298)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
18100 <h5><a name="7.24.4.4" href="#7.24.4.4">7.24.4.4 Wide string comparison functions</a></h5>
18102 Unless explicitly stated otherwise, the functions described in this subclause order two
18103 wide characters the same way as two integers of the underlying integer type designated
18106 <h5><a name="7.24.4.4.1" href="#7.24.4.4.1">7.24.4.4.1 The wcscmp function</a></h5>
18110 #include <a href="#7.24"><wchar.h></a>
18111 int wcscmp(const wchar_t *s1, const wchar_t *s2);</pre>
18112 <h6>Description</h6>
18114 The wcscmp function compares the wide string pointed to by s1 to the wide string
18118 The wcscmp function returns an integer greater than, equal to, or less than zero,
18119 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18120 wide string pointed to by s2.
18122 <h5><a name="7.24.4.4.2" href="#7.24.4.4.2">7.24.4.4.2 The wcscoll function</a></h5>
18126 #include <a href="#7.24"><wchar.h></a>
18127 int wcscoll(const wchar_t *s1, const wchar_t *s2);</pre>
18128 <h6>Description</h6>
18130 The wcscoll function compares the wide string pointed to by s1 to the wide string
18131 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
18135 The wcscoll function returns an integer greater than, equal to, or less than zero,
18136 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18140 wide string pointed to by s2 when both are interpreted as appropriate to the current
18143 <h5><a name="7.24.4.4.3" href="#7.24.4.4.3">7.24.4.4.3 The wcsncmp function</a></h5>
18147 #include <a href="#7.24"><wchar.h></a>
18148 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
18150 <h6>Description</h6>
18152 The wcsncmp function compares not more than n wide characters (those that follow a
18153 null wide character are not compared) from the array pointed to by s1 to the array
18157 The wcsncmp function returns an integer greater than, equal to, or less than zero,
18158 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18159 to, or less than the possibly null-terminated array pointed to by s2.
18161 <h5><a name="7.24.4.4.4" href="#7.24.4.4.4">7.24.4.4.4 The wcsxfrm function</a></h5>
18165 #include <a href="#7.24"><wchar.h></a>
18166 size_t wcsxfrm(wchar_t * restrict s1,
18167 const wchar_t * restrict s2,
18169 <h6>Description</h6>
18171 The wcsxfrm function transforms the wide string pointed to by s2 and places the
18172 resulting wide string into the array pointed to by s1. The transformation is such that if
18173 the wcscmp function is applied to two transformed wide strings, it returns a value greater
18174 than, equal to, or less than zero, corresponding to the result of the wcscoll function
18175 applied to the same two original wide strings. No more than n wide characters are placed
18176 into the resulting array pointed to by s1, including the terminating null wide character. If
18177 n is zero, s1 is permitted to be a null pointer.
18180 The wcsxfrm function returns the length of the transformed wide string (not including
18181 the terminating null wide character). If the value returned is n or greater, the contents of
18182 the array pointed to by s1 are indeterminate.
18184 EXAMPLE The value of the following expression is the length of the array needed to hold the
18185 transformation of the wide string pointed to by s:
18188 1 + wcsxfrm(NULL, s, 0)</pre>
18191 <h5><a name="7.24.4.4.5" href="#7.24.4.4.5">7.24.4.4.5 The wmemcmp function</a></h5>
18195 #include <a href="#7.24"><wchar.h></a>
18196 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
18198 <h6>Description</h6>
18200 The wmemcmp function compares the first n wide characters of the object pointed to by
18201 s1 to the first n wide characters of the object pointed to by s2.
18204 The wmemcmp function returns an integer greater than, equal to, or less than zero,
18205 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18208 <h5><a name="7.24.4.5" href="#7.24.4.5">7.24.4.5 Wide string search functions</a></h5>
18210 <h5><a name="7.24.4.5.1" href="#7.24.4.5.1">7.24.4.5.1 The wcschr function</a></h5>
18214 #include <a href="#7.24"><wchar.h></a>
18215 wchar_t *wcschr(const wchar_t *s, wchar_t c);</pre>
18216 <h6>Description</h6>
18218 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
18219 The terminating null wide character is considered to be part of the wide string.
18222 The wcschr function returns a pointer to the located wide character, or a null pointer if
18223 the wide character does not occur in the wide string.
18225 <h5><a name="7.24.4.5.2" href="#7.24.4.5.2">7.24.4.5.2 The wcscspn function</a></h5>
18229 #include <a href="#7.24"><wchar.h></a>
18230 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);</pre>
18231 <h6>Description</h6>
18233 The wcscspn function computes the length of the maximum initial segment of the wide
18234 string pointed to by s1 which consists entirely of wide characters not from the wide
18235 string pointed to by s2.
18239 The wcscspn function returns the length of the segment.
18241 <h5><a name="7.24.4.5.3" href="#7.24.4.5.3">7.24.4.5.3 The wcspbrk function</a></h5>
18245 #include <a href="#7.24"><wchar.h></a>
18246 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);</pre>
18247 <h6>Description</h6>
18249 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
18250 any wide character from the wide string pointed to by s2.
18253 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
18254 no wide character from s2 occurs in s1.
18256 <h5><a name="7.24.4.5.4" href="#7.24.4.5.4">7.24.4.5.4 The wcsrchr function</a></h5>
18260 #include <a href="#7.24"><wchar.h></a>
18261 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);</pre>
18262 <h6>Description</h6>
18264 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
18265 s. The terminating null wide character is considered to be part of the wide string.
18268 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
18269 not occur in the wide string.
18271 <h5><a name="7.24.4.5.5" href="#7.24.4.5.5">7.24.4.5.5 The wcsspn function</a></h5>
18275 #include <a href="#7.24"><wchar.h></a>
18276 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);</pre>
18277 <h6>Description</h6>
18279 The wcsspn function computes the length of the maximum initial segment of the wide
18280 string pointed to by s1 which consists entirely of wide characters from the wide string
18284 The wcsspn function returns the length of the segment.
18287 <h5><a name="7.24.4.5.6" href="#7.24.4.5.6">7.24.4.5.6 The wcsstr function</a></h5>
18291 #include <a href="#7.24"><wchar.h></a>
18292 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);</pre>
18293 <h6>Description</h6>
18295 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
18296 the sequence of wide characters (excluding the terminating null wide character) in the
18297 wide string pointed to by s2.
18300 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
18301 wide string is not found. If s2 points to a wide string with zero length, the function
18304 <h5><a name="7.24.4.5.7" href="#7.24.4.5.7">7.24.4.5.7 The wcstok function</a></h5>
18308 #include <a href="#7.24"><wchar.h></a>
18309 wchar_t *wcstok(wchar_t * restrict s1,
18310 const wchar_t * restrict s2,
18311 wchar_t ** restrict ptr);</pre>
18312 <h6>Description</h6>
18314 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
18315 a sequence of tokens, each of which is delimited by a wide character from the wide string
18316 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
18317 which the wcstok function stores information necessary for it to continue scanning the
18320 The first call in a sequence has a non-null first argument and stores an initial value in the
18321 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
18322 the object pointed to by ptr is required to have the value stored by the previous call in
18323 the sequence, which is then updated. The separator wide string pointed to by s2 may be
18324 different from call to call.
18326 The first call in the sequence searches the wide string pointed to by s1 for the first wide
18327 character that is not contained in the current separator wide string pointed to by s2. If no
18328 such wide character is found, then there are no tokens in the wide string pointed to by s1
18329 and the wcstok function returns a null pointer. If such a wide character is found, it is
18330 the start of the first token.
18332 The wcstok function then searches from there for a wide character that is contained in
18333 the current separator wide string. If no such wide character is found, the current token
18335 extends to the end of the wide string pointed to by s1, and subsequent searches in the
18336 same wide string for a token return a null pointer. If such a wide character is found, it is
18337 overwritten by a null wide character, which terminates the current token.
18339 In all cases, the wcstok function stores sufficient information in the pointer pointed to
18340 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
18341 value for ptr, shall start searching just past the element overwritten by a null wide
18342 character (if any).
18345 The wcstok function returns a pointer to the first wide character of a token, or a null
18346 pointer if there is no token.
18350 #include <a href="#7.24"><wchar.h></a>
18351 static wchar_t str1[] = L"?a???b,,,#c";
18352 static wchar_t str2[] = L"\t \t";
18353 wchar_t *t, *ptr1, *ptr2;
18354 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
18355 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
18356 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
18357 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
18358 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer</pre>
18361 <h5><a name="7.24.4.5.8" href="#7.24.4.5.8">7.24.4.5.8 The wmemchr function</a></h5>
18365 #include <a href="#7.24"><wchar.h></a>
18366 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
18368 <h6>Description</h6>
18370 The wmemchr function locates the first occurrence of c in the initial n wide characters of
18371 the object pointed to by s.
18374 The wmemchr function returns a pointer to the located wide character, or a null pointer if
18375 the wide character does not occur in the object.
18378 <h5><a name="7.24.4.6" href="#7.24.4.6">7.24.4.6 Miscellaneous functions</a></h5>
18380 <h5><a name="7.24.4.6.1" href="#7.24.4.6.1">7.24.4.6.1 The wcslen function</a></h5>
18384 #include <a href="#7.24"><wchar.h></a>
18385 size_t wcslen(const wchar_t *s);</pre>
18386 <h6>Description</h6>
18388 The wcslen function computes the length of the wide string pointed to by s.
18391 The wcslen function returns the number of wide characters that precede the terminating
18392 null wide character.
18394 <h5><a name="7.24.4.6.2" href="#7.24.4.6.2">7.24.4.6.2 The wmemset function</a></h5>
18398 #include <a href="#7.24"><wchar.h></a>
18399 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);</pre>
18400 <h6>Description</h6>
18402 The wmemset function copies the value of c into each of the first n wide characters of
18403 the object pointed to by s.
18406 The wmemset function returns the value of s.
18408 <h4><a name="7.24.5" href="#7.24.5">7.24.5 Wide character time conversion functions</a></h4>
18410 <h5><a name="7.24.5.1" href="#7.24.5.1">7.24.5.1 The wcsftime function</a></h5>
18414 #include <a href="#7.23"><time.h></a>
18415 #include <a href="#7.24"><wchar.h></a>
18416 size_t wcsftime(wchar_t * restrict s,
18418 const wchar_t * restrict format,
18419 const struct tm * restrict timeptr);</pre>
18420 <h6>Description</h6>
18422 The wcsftime function is equivalent to the strftime function, except that:
18424 <li> The argument s points to the initial element of an array of wide characters into which
18425 the generated output is to be placed.
18427 <li> The argument maxsize indicates the limiting number of wide characters.
18428 <li> The argument format is a wide string and the conversion specifiers are replaced by
18429 corresponding sequences of wide characters.
18430 <li> The return value indicates the number of wide characters.
18434 If the total number of resulting wide characters including the terminating null wide
18435 character is not more than maxsize, the wcsftime function returns the number of
18436 wide characters placed into the array pointed to by s not including the terminating null
18437 wide character. Otherwise, zero is returned and the contents of the array are
18440 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Extended multibyte/wide character conversion utilities</a></h4>
18442 The header <a href="#7.24"><wchar.h></a> declares an extended set of functions useful for conversion
18443 between multibyte characters and wide characters.
18445 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.24.6.3">7.24.6.3</a> and
18446 <a href="#7.24.6.4">7.24.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
18447 to describe the current conversion state from a particular multibyte character sequence to
18448 a wide character sequence (or the reverse) under the rules of a particular setting for the
18449 LC_CTYPE category of the current locale.
18451 The initial conversion state corresponds, for a conversion in either direction, to the
18452 beginning of a new multibyte character in the initial shift state. A zero-valued
18453 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
18454 valued mbstate_t object can be used to initiate conversion involving any multibyte
18455 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
18456 been altered by any of the functions described in this subclause, and is then used with a
18457 different multibyte character sequence, or in the other conversion direction, or with a
18458 different LC_CTYPE category setting than on earlier function calls, the behavior is
18459 undefined.<sup><a href="#note299"><b>299)</b></a></sup>
18461 On entry, each function takes the described conversion state (either internal or pointed to
18462 by an argument) as current. The conversion state described by the pointed-to object is
18463 altered as needed to track the shift state, and the position within a multibyte character, for
18464 the associated multibyte character sequence.
18472 <p><small><a name="note299" href="#note299">299)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
18473 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
18477 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 Single-byte/wide character conversion functions</a></h5>
18479 <h5><a name="7.24.6.1.1" href="#7.24.6.1.1">7.24.6.1.1 The btowc function</a></h5>
18483 #include <a href="#7.19"><stdio.h></a>
18484 #include <a href="#7.24"><wchar.h></a>
18485 wint_t btowc(int c);</pre>
18486 <h6>Description</h6>
18488 The btowc function determines whether c constitutes a valid single-byte character in the
18489 initial shift state.
18492 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
18493 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
18494 returns the wide character representation of that character.
18496 <h5><a name="7.24.6.1.2" href="#7.24.6.1.2">7.24.6.1.2 The wctob function</a></h5>
18500 #include <a href="#7.19"><stdio.h></a>
18501 #include <a href="#7.24"><wchar.h></a>
18502 int wctob(wint_t c);</pre>
18503 <h6>Description</h6>
18505 The wctob function determines whether c corresponds to a member of the extended
18506 character set whose multibyte character representation is a single byte when in the initial
18510 The wctob function returns EOF if c does not correspond to a multibyte character with
18511 length one in the initial shift state. Otherwise, it returns the single-byte representation of
18512 that character as an unsigned char converted to an int.
18514 <h5><a name="7.24.6.2" href="#7.24.6.2">7.24.6.2 Conversion state functions</a></h5>
18516 <h5><a name="7.24.6.2.1" href="#7.24.6.2.1">7.24.6.2.1 The mbsinit function</a></h5>
18520 #include <a href="#7.24"><wchar.h></a>
18521 int mbsinit(const mbstate_t *ps);</pre>
18522 <h6>Description</h6>
18524 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
18525 mbstate_t object describes an initial conversion state.
18529 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
18530 describes an initial conversion state; otherwise, it returns zero.
18532 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 Restartable multibyte/wide character conversion functions</a></h5>
18534 These functions differ from the corresponding multibyte character functions of <a href="#7.20.7">7.20.7</a>
18535 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
18536 pointer to mbstate_t that points to an object that can completely describe the current
18537 conversion state of the associated multibyte character sequence. If ps is a null pointer,
18538 each function uses its own internal mbstate_t object instead, which is initialized at
18539 program startup to the initial conversion state. The implementation behaves as if no
18540 library function calls these functions with a null pointer for ps.
18542 Also unlike their corresponding functions, the return value does not represent whether the
18543 encoding is state-dependent.
18545 <h5><a name="7.24.6.3.1" href="#7.24.6.3.1">7.24.6.3.1 The mbrlen function</a></h5>
18549 #include <a href="#7.24"><wchar.h></a>
18550 size_t mbrlen(const char * restrict s,
18552 mbstate_t * restrict ps);</pre>
18553 <h6>Description</h6>
18555 The mbrlen function is equivalent to the call:
18557 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)</pre>
18558 where internal is the mbstate_t object for the mbrlen function, except that the
18559 expression designated by ps is evaluated only once.
18562 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
18564 <p><b> Forward references</b>: the mbrtowc function (<a href="#7.24.6.3.2">7.24.6.3.2</a>).
18567 <h5><a name="7.24.6.3.2" href="#7.24.6.3.2">7.24.6.3.2 The mbrtowc function</a></h5>
18571 #include <a href="#7.24"><wchar.h></a>
18572 size_t mbrtowc(wchar_t * restrict pwc,
18573 const char * restrict s,
18575 mbstate_t * restrict ps);</pre>
18576 <h6>Description</h6>
18578 If s is a null pointer, the mbrtowc function is equivalent to the call:
18580 mbrtowc(NULL, "", 1, ps)</pre>
18581 In this case, the values of the parameters pwc and n are ignored.
18583 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
18584 the byte pointed to by s to determine the number of bytes needed to complete the next
18585 multibyte character (including any shift sequences). If the function determines that the
18586 next multibyte character is complete and valid, it determines the value of the
18587 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18588 the object pointed to by pwc. If the corresponding wide character is the null wide
18589 character, the resulting state described is the initial conversion state.
18592 The mbrtowc function returns the first of the following that applies (given the current
18594 0 if the next n or fewer bytes complete the multibyte character that
18596 corresponds to the null wide character (which is the value stored).</pre>
18597 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
18599 character (which is the value stored); the value returned is the number
18600 of bytes that complete the multibyte character.</pre>
18601 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
18603 multibyte character, and all n bytes have been processed (no value is
18604 stored).<sup><a href="#note300"><b>300)</b></a></sup></pre>
18605 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
18607 do not contribute to a complete and valid multibyte character (no
18608 value is stored); the value of the macro EILSEQ is stored in errno,
18609 and the conversion state is unspecified.</pre>
18614 <p><small><a name="note300" href="#note300">300)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
18615 sequence of redundant shift sequences (for implementations with state-dependent encodings).
18618 <h5><a name="7.24.6.3.3" href="#7.24.6.3.3">7.24.6.3.3 The wcrtomb function</a></h5>
18622 #include <a href="#7.24"><wchar.h></a>
18623 size_t wcrtomb(char * restrict s,
18625 mbstate_t * restrict ps);</pre>
18626 <h6>Description</h6>
18628 If s is a null pointer, the wcrtomb function is equivalent to the call
18630 wcrtomb(buf, L'\0', ps)</pre>
18631 where buf is an internal buffer.
18633 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
18634 to represent the multibyte character that corresponds to the wide character given by wc
18635 (including any shift sequences), and stores the multibyte character representation in the
18636 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
18637 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
18638 to restore the initial shift state; the resulting state described is the initial conversion state.
18641 The wcrtomb function returns the number of bytes stored in the array object (including
18642 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
18643 the function stores the value of the macro EILSEQ in errno and returns
18644 (size_t)(-1); the conversion state is unspecified.
18646 <h5><a name="7.24.6.4" href="#7.24.6.4">7.24.6.4 Restartable multibyte/wide string conversion functions</a></h5>
18648 These functions differ from the corresponding multibyte string functions of <a href="#7.20.8">7.20.8</a>
18649 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
18650 mbstate_t that points to an object that can completely describe the current conversion
18651 state of the associated multibyte character sequence. If ps is a null pointer, each function
18652 uses its own internal mbstate_t object instead, which is initialized at program startup
18653 to the initial conversion state. The implementation behaves as if no library function calls
18654 these functions with a null pointer for ps.
18656 Also unlike their corresponding functions, the conversion source parameter, src, has a
18657 pointer-to-pointer type. When the function is storing the results of conversions (that is,
18658 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
18659 to reflect the amount of the source processed by that invocation.
18662 <h5><a name="7.24.6.4.1" href="#7.24.6.4.1">7.24.6.4.1 The mbsrtowcs function</a></h5>
18666 #include <a href="#7.24"><wchar.h></a>
18667 size_t mbsrtowcs(wchar_t * restrict dst,
18668 const char ** restrict src,
18670 mbstate_t * restrict ps);</pre>
18671 <h6>Description</h6>
18673 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
18674 conversion state described by the object pointed to by ps, from the array indirectly
18675 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
18676 pointer, the converted characters are stored into the array pointed to by dst. Conversion
18677 continues up to and including a terminating null character, which is also stored.
18678 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
18679 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
18680 characters have been stored into the array pointed to by dst.<sup><a href="#note301"><b>301)</b></a></sup> Each conversion takes
18681 place as if by a call to the mbrtowc function.
18683 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18684 pointer (if conversion stopped due to reaching a terminating null character) or the address
18685 just past the last multibyte character converted (if any). If conversion stopped due to
18686 reaching a terminating null character and if dst is not a null pointer, the resulting state
18687 described is the initial conversion state.
18690 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
18691 character, an encoding error occurs: the mbsrtowcs function stores the value of the
18692 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
18693 unspecified. Otherwise, it returns the number of multibyte characters successfully
18694 converted, not including the terminating null character (if any).
18702 <p><small><a name="note301" href="#note301">301)</a> Thus, the value of len is ignored if dst is a null pointer.
18705 <h5><a name="7.24.6.4.2" href="#7.24.6.4.2">7.24.6.4.2 The wcsrtombs function</a></h5>
18709 #include <a href="#7.24"><wchar.h></a>
18710 size_t wcsrtombs(char * restrict dst,
18711 const wchar_t ** restrict src,
18713 mbstate_t * restrict ps);</pre>
18714 <h6>Description</h6>
18716 The wcsrtombs function converts a sequence of wide characters from the array
18717 indirectly pointed to by src into a sequence of corresponding multibyte characters that
18718 begins in the conversion state described by the object pointed to by ps. If dst is not a
18719 null pointer, the converted characters are then stored into the array pointed to by dst.
18720 Conversion continues up to and including a terminating null wide character, which is also
18721 stored. Conversion stops earlier in two cases: when a wide character is reached that does
18722 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
18723 next multibyte character would exceed the limit of len total bytes to be stored into the
18724 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
18725 function.<sup><a href="#note302"><b>302)</b></a></sup>
18727 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18728 pointer (if conversion stopped due to reaching a terminating null wide character) or the
18729 address just past the last wide character converted (if any). If conversion stopped due to
18730 reaching a terminating null wide character, the resulting state described is the initial
18734 If conversion stops because a wide character is reached that does not correspond to a
18735 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
18736 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
18737 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
18738 character sequence, not including the terminating null character (if any).
18746 <p><small><a name="note302" href="#note302">302)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
18747 include those necessary to reach the initial shift state immediately before the null byte.
18750 <h3><a name="7.25" href="#7.25">7.25 Wide character classification and mapping utilities <wctype.h></a></h3>
18752 <h4><a name="7.25.1" href="#7.25.1">7.25.1 Introduction</a></h4>
18754 The header <a href="#7.25"><wctype.h></a> declares three data types, one macro, and many functions.<sup><a href="#note303"><b>303)</b></a></sup>
18756 The types declared are
18759 described in <a href="#7.24.1">7.24.1</a>;
18762 which is a scalar type that can hold values which represent locale-specific character
18766 which is a scalar type that can hold values which represent locale-specific character
18769 The macro defined is WEOF (described in <a href="#7.24.1">7.24.1</a>).
18771 The functions declared are grouped as follows:
18773 <li> Functions that provide wide character classification;
18774 <li> Extensible functions that provide wide character classification;
18775 <li> Functions that provide wide character case mapping;
18776 <li> Extensible functions that provide wide character mapping.
18779 For all functions described in this subclause that accept an argument of type wint_t, the
18780 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
18781 this argument has any other value, the behavior is undefined.
18783 The behavior of these functions is affected by the LC_CTYPE category of the current
18792 <p><small><a name="note303" href="#note303">303)</a> See ''future library directions'' (<a href="#7.26.13">7.26.13</a>).
18795 <h4><a name="7.25.2" href="#7.25.2">7.25.2 Wide character classification utilities</a></h4>
18797 The header <a href="#7.25"><wctype.h></a> declares several functions useful for classifying wide
18800 The term printing wide character refers to a member of a locale-specific set of wide
18801 characters, each of which occupies at least one printing position on a display device. The
18802 term control wide character refers to a member of a locale-specific set of wide characters
18803 that are not printing wide characters.
18805 <h5><a name="7.25.2.1" href="#7.25.2.1">7.25.2.1 Wide character classification functions</a></h5>
18807 The functions in this subclause return nonzero (true) if and only if the value of the
18808 argument wc conforms to that in the description of the function.
18810 Each of the following functions returns true for each wide character that corresponds (as
18811 if by a call to the wctob function) to a single-byte character for which the corresponding
18812 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
18813 iswpunct functions may differ with respect to wide characters other than L' ' that are
18814 both printing and white-space wide characters.<sup><a href="#note304"><b>304)</b></a></sup>
18815 <p><b> Forward references</b>: the wctob function (<a href="#7.24.6.1.2">7.24.6.1.2</a>).
18818 <p><small><a name="note304" href="#note304">304)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
18819 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
18820 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
18821 && iswspace(wc) is true, but not both.
18824 <h5><a name="7.25.2.1.1" href="#7.25.2.1.1">7.25.2.1.1 The iswalnum function</a></h5>
18828 #include <a href="#7.25"><wctype.h></a>
18829 int iswalnum(wint_t wc);</pre>
18830 <h6>Description</h6>
18832 The iswalnum function tests for any wide character for which iswalpha or
18835 <h5><a name="7.25.2.1.2" href="#7.25.2.1.2">7.25.2.1.2 The iswalpha function</a></h5>
18839 #include <a href="#7.25"><wctype.h></a>
18840 int iswalpha(wint_t wc);</pre>
18841 <h6>Description</h6>
18843 The iswalpha function tests for any wide character for which iswupper or
18844 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
18847 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
18848 is true.<sup><a href="#note305"><b>305)</b></a></sup>
18851 <p><small><a name="note305" href="#note305">305)</a> The functions iswlower and iswupper test true or false separately for each of these additional
18852 wide characters; all four combinations are possible.
18855 <h5><a name="7.25.2.1.3" href="#7.25.2.1.3">7.25.2.1.3 The iswblank function</a></h5>
18859 #include <a href="#7.25"><wctype.h></a>
18860 int iswblank(wint_t wc);</pre>
18861 <h6>Description</h6>
18863 The iswblank function tests for any wide character that is a standard blank wide
18864 character or is one of a locale-specific set of wide characters for which iswspace is true
18865 and that is used to separate words within a line of text. The standard blank wide
18866 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
18867 locale, iswblank returns true only for the standard blank characters.
18869 <h5><a name="7.25.2.1.4" href="#7.25.2.1.4">7.25.2.1.4 The iswcntrl function</a></h5>
18873 #include <a href="#7.25"><wctype.h></a>
18874 int iswcntrl(wint_t wc);</pre>
18875 <h6>Description</h6>
18877 The iswcntrl function tests for any control wide character.
18879 <h5><a name="7.25.2.1.5" href="#7.25.2.1.5">7.25.2.1.5 The iswdigit function</a></h5>
18883 #include <a href="#7.25"><wctype.h></a>
18884 int iswdigit(wint_t wc);</pre>
18885 <h6>Description</h6>
18887 The iswdigit function tests for any wide character that corresponds to a decimal-digit
18888 character (as defined in <a href="#5.2.1">5.2.1</a>).
18890 <h5><a name="7.25.2.1.6" href="#7.25.2.1.6">7.25.2.1.6 The iswgraph function</a></h5>
18894 #include <a href="#7.25"><wctype.h></a>
18895 int iswgraph(wint_t wc);</pre>
18901 <h6>Description</h6>
18903 The iswgraph function tests for any wide character for which iswprint is true and
18904 iswspace is false.<sup><a href="#note306"><b>306)</b></a></sup>
18907 <p><small><a name="note306" href="#note306">306)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
18908 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
18909 characters other than ' '.
18912 <h5><a name="7.25.2.1.7" href="#7.25.2.1.7">7.25.2.1.7 The iswlower function</a></h5>
18916 #include <a href="#7.25"><wctype.h></a>
18917 int iswlower(wint_t wc);</pre>
18918 <h6>Description</h6>
18920 The iswlower function tests for any wide character that corresponds to a lowercase
18921 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18922 iswdigit, iswpunct, or iswspace is true.
18924 <h5><a name="7.25.2.1.8" href="#7.25.2.1.8">7.25.2.1.8 The iswprint function</a></h5>
18928 #include <a href="#7.25"><wctype.h></a>
18929 int iswprint(wint_t wc);</pre>
18930 <h6>Description</h6>
18932 The iswprint function tests for any printing wide character.
18934 <h5><a name="7.25.2.1.9" href="#7.25.2.1.9">7.25.2.1.9 The iswpunct function</a></h5>
18938 #include <a href="#7.25"><wctype.h></a>
18939 int iswpunct(wint_t wc);</pre>
18940 <h6>Description</h6>
18942 The iswpunct function tests for any printing wide character that is one of a locale-
18943 specific set of punctuation wide characters for which neither iswspace nor iswalnum
18946 <h5><a name="7.25.2.1.10" href="#7.25.2.1.10">7.25.2.1.10 The iswspace function</a></h5>
18950 #include <a href="#7.25"><wctype.h></a>
18951 int iswspace(wint_t wc);</pre>
18956 <h6>Description</h6>
18958 The iswspace function tests for any wide character that corresponds to a locale-specific
18959 set of white-space wide characters for which none of iswalnum, iswgraph, or
18962 <h5><a name="7.25.2.1.11" href="#7.25.2.1.11">7.25.2.1.11 The iswupper function</a></h5>
18966 #include <a href="#7.25"><wctype.h></a>
18967 int iswupper(wint_t wc);</pre>
18968 <h6>Description</h6>
18970 The iswupper function tests for any wide character that corresponds to an uppercase
18971 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18972 iswdigit, iswpunct, or iswspace is true.
18974 <h5><a name="7.25.2.1.12" href="#7.25.2.1.12">7.25.2.1.12 The iswxdigit function</a></h5>
18978 #include <a href="#7.25"><wctype.h></a>
18979 int iswxdigit(wint_t wc);</pre>
18980 <h6>Description</h6>
18982 The iswxdigit function tests for any wide character that corresponds to a
18983 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
18985 <h5><a name="7.25.2.2" href="#7.25.2.2">7.25.2.2 Extensible wide character classification functions</a></h5>
18987 The functions wctype and iswctype provide extensible wide character classification
18988 as well as testing equivalent to that performed by the functions described in the previous
18989 subclause (<a href="#7.25.2.1">7.25.2.1</a>).
18991 <h5><a name="7.25.2.2.1" href="#7.25.2.2.1">7.25.2.2.1 The iswctype function</a></h5>
18995 #include <a href="#7.25"><wctype.h></a>
18996 int iswctype(wint_t wc, wctype_t desc);</pre>
18997 <h6>Description</h6>
18999 The iswctype function determines whether the wide character wc has the property
19000 described by desc. The current setting of the LC_CTYPE category shall be the same as
19001 during the call to wctype that returned the value desc.
19003 Each of the following expressions has a truth-value equivalent to the call to the wide
19004 character classification function (<a href="#7.25.2.1">7.25.2.1</a>) in the comment that follows the expression:
19007 iswctype(wc, wctype("alnum")) // iswalnum(wc)
19008 iswctype(wc, wctype("alpha")) // iswalpha(wc)
19009 iswctype(wc, wctype("blank")) // iswblank(wc)
19010 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
19011 iswctype(wc, wctype("digit")) // iswdigit(wc)
19012 iswctype(wc, wctype("graph")) // iswgraph(wc)
19013 iswctype(wc, wctype("lower")) // iswlower(wc)
19014 iswctype(wc, wctype("print")) // iswprint(wc)
19015 iswctype(wc, wctype("punct")) // iswpunct(wc)
19016 iswctype(wc, wctype("space")) // iswspace(wc)
19017 iswctype(wc, wctype("upper")) // iswupper(wc)
19018 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)</pre>
19021 The iswctype function returns nonzero (true) if and only if the value of the wide
19022 character wc has the property described by desc.
19023 <p><b> Forward references</b>: the wctype function (<a href="#7.25.2.2.2">7.25.2.2.2</a>).
19025 <h5><a name="7.25.2.2.2" href="#7.25.2.2.2">7.25.2.2.2 The wctype function</a></h5>
19029 #include <a href="#7.25"><wctype.h></a>
19030 wctype_t wctype(const char *property);</pre>
19031 <h6>Description</h6>
19033 The wctype function constructs a value with type wctype_t that describes a class of
19034 wide characters identified by the string argument property.
19036 The strings listed in the description of the iswctype function shall be valid in all
19037 locales as property arguments to the wctype function.
19040 If property identifies a valid class of wide characters according to the LC_CTYPE
19041 category of the current locale, the wctype function returns a nonzero value that is valid
19042 as the second argument to the iswctype function; otherwise, it returns zero. *
19045 <h4><a name="7.25.3" href="#7.25.3">7.25.3 Wide character case mapping utilities</a></h4>
19047 The header <a href="#7.25"><wctype.h></a> declares several functions useful for mapping wide characters.
19049 <h5><a name="7.25.3.1" href="#7.25.3.1">7.25.3.1 Wide character case mapping functions</a></h5>
19051 <h5><a name="7.25.3.1.1" href="#7.25.3.1.1">7.25.3.1.1 The towlower function</a></h5>
19055 #include <a href="#7.25"><wctype.h></a>
19056 wint_t towlower(wint_t wc);</pre>
19057 <h6>Description</h6>
19059 The towlower function converts an uppercase letter to a corresponding lowercase letter.
19062 If the argument is a wide character for which iswupper is true and there are one or
19063 more corresponding wide characters, as specified by the current locale, for which
19064 iswlower is true, the towlower function returns one of the corresponding wide
19065 characters (always the same one for any given locale); otherwise, the argument is
19066 returned unchanged.
19068 <h5><a name="7.25.3.1.2" href="#7.25.3.1.2">7.25.3.1.2 The towupper function</a></h5>
19072 #include <a href="#7.25"><wctype.h></a>
19073 wint_t towupper(wint_t wc);</pre>
19074 <h6>Description</h6>
19076 The towupper function converts a lowercase letter to a corresponding uppercase letter.
19079 If the argument is a wide character for which iswlower is true and there are one or
19080 more corresponding wide characters, as specified by the current locale, for which
19081 iswupper is true, the towupper function returns one of the corresponding wide
19082 characters (always the same one for any given locale); otherwise, the argument is
19083 returned unchanged.
19085 <h5><a name="7.25.3.2" href="#7.25.3.2">7.25.3.2 Extensible wide character case mapping functions</a></h5>
19087 The functions wctrans and towctrans provide extensible wide character mapping as
19088 well as case mapping equivalent to that performed by the functions described in the
19089 previous subclause (<a href="#7.25.3.1">7.25.3.1</a>).
19092 <h5><a name="7.25.3.2.1" href="#7.25.3.2.1">7.25.3.2.1 The towctrans function</a></h5>
19096 #include <a href="#7.25"><wctype.h></a>
19097 wint_t towctrans(wint_t wc, wctrans_t desc);</pre>
19098 <h6>Description</h6>
19100 The towctrans function maps the wide character wc using the mapping described by
19101 desc. The current setting of the LC_CTYPE category shall be the same as during the call
19102 to wctrans that returned the value desc.
19104 Each of the following expressions behaves the same as the call to the wide character case
19105 mapping function (<a href="#7.25.3.1">7.25.3.1</a>) in the comment that follows the expression:
19107 towctrans(wc, wctrans("tolower")) // towlower(wc)
19108 towctrans(wc, wctrans("toupper")) // towupper(wc)</pre>
19111 The towctrans function returns the mapped value of wc using the mapping described
19114 <h5><a name="7.25.3.2.2" href="#7.25.3.2.2">7.25.3.2.2 The wctrans function</a></h5>
19118 #include <a href="#7.25"><wctype.h></a>
19119 wctrans_t wctrans(const char *property);</pre>
19120 <h6>Description</h6>
19122 The wctrans function constructs a value with type wctrans_t that describes a
19123 mapping between wide characters identified by the string argument property.
19125 The strings listed in the description of the towctrans function shall be valid in all
19126 locales as property arguments to the wctrans function.
19129 If property identifies a valid mapping of wide characters according to the LC_CTYPE
19130 category of the current locale, the wctrans function returns a nonzero value that is valid
19131 as the second argument to the towctrans function; otherwise, it returns zero.
19134 <h3><a name="7.26" href="#7.26">7.26 Future library directions</a></h3>
19136 The following names are grouped under individual headers for convenience. All external
19137 names described below are reserved no matter what headers are included by the program.
19139 <h4><a name="7.26.1" href="#7.26.1">7.26.1 Complex arithmetic <complex.h></a></h4>
19144 cerfc clog10 clgamma
19145 cexp2 clog1p ctgamma</pre>
19146 and the same names suffixed with f or l may be added to the declarations in the
19147 <a href="#7.3"><complex.h></a> header.
19149 <h4><a name="7.26.2" href="#7.26.2">7.26.2 Character handling <ctype.h></a></h4>
19151 Function names that begin with either is or to, and a lowercase letter may be added to
19152 the declarations in the <a href="#7.4"><ctype.h></a> header.
19154 <h4><a name="7.26.3" href="#7.26.3">7.26.3 Errors <errno.h></a></h4>
19156 Macros that begin with E and a digit or E and an uppercase letter may be added to the
19157 declarations in the <a href="#7.5"><errno.h></a> header.
19159 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Format conversion of integer types <inttypes.h></a></h4>
19161 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
19162 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
19164 <h4><a name="7.26.5" href="#7.26.5">7.26.5 Localization <locale.h></a></h4>
19166 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
19167 the <a href="#7.11"><locale.h></a> header.
19169 <h4><a name="7.26.6" href="#7.26.6">7.26.6 Signal handling <signal.h></a></h4>
19171 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
19172 letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
19174 <h4><a name="7.26.7" href="#7.26.7">7.26.7 Boolean type and values <stdbool.h></a></h4>
19176 The ability to undefine and perhaps then redefine the macros bool, true, and false is
19177 an obsolescent feature.
19179 <h4><a name="7.26.8" href="#7.26.8">7.26.8 Integer types <stdint.h></a></h4>
19181 Typedef names beginning with int or uint and ending with _t may be added to the
19182 types defined in the <a href="#7.18"><stdint.h></a> header. Macro names beginning with INT or UINT
19183 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
19184 <a href="#7.18"><stdint.h></a> header.
19187 <h4><a name="7.26.9" href="#7.26.9">7.26.9 Input/output <stdio.h></a></h4>
19189 Lowercase letters may be added to the conversion specifiers and length modifiers in
19190 fprintf and fscanf. Other characters may be used in extensions.
19192 The gets function is obsolescent, and is deprecated.
19194 The use of ungetc on a binary stream where the file position indicator is zero prior to
19195 the call is an obsolescent feature.
19197 <h4><a name="7.26.10" href="#7.26.10">7.26.10 General utilities <stdlib.h></a></h4>
19199 Function names that begin with str and a lowercase letter may be added to the
19200 declarations in the <a href="#7.20"><stdlib.h></a> header.
19202 <h4><a name="7.26.11" href="#7.26.11">7.26.11 String handling <string.h></a></h4>
19204 Function names that begin with str, mem, or wcs and a lowercase letter may be added
19205 to the declarations in the <a href="#7.21"><string.h></a> header.
19207 <h4><a name="7.26.12" href="#7.26.12">7.26.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
19209 Function names that begin with wcs and a lowercase letter may be added to the
19210 declarations in the <a href="#7.24"><wchar.h></a> header.
19212 Lowercase letters may be added to the conversion specifiers and length modifiers in
19213 fwprintf and fwscanf. Other characters may be used in extensions.
19215 <h4><a name="7.26.13" href="#7.26.13">7.26.13 Wide character classification and mapping utilities</a></h4>
19216 <a href="#7.25"><wctype.h></a>
19218 Function names that begin with is or to and a lowercase letter may be added to the
19219 declarations in the <a href="#7.25"><wctype.h></a> header.
19222 <h2><a name="A" href="#A">Annex A</a></h2>
19226 Language syntax summary</pre>
19227 NOTE The notation is described in <a href="#6.1">6.1</a>.
19230 <h3><a name="A.1" href="#A.1">A.1 Lexical grammar</a></h3>
19232 <h4><a name="A.1.1" href="#A.1.1">A.1.1 Lexical elements</a></h4>
19233 (<a href="#6.4">6.4</a>) token:
19240 (<a href="#6.4">6.4</a>) preprocessing-token:
19248 each non-white-space character that cannot be one of the above</pre>
19250 <h4><a name="A.1.2" href="#A.1.2">A.1.2 Keywords</a></h4>
19251 (<a href="#6.4.1">6.4.1</a>) keyword: one of
19254 auto enum restrict unsigned
19255 break extern return void
19256 case float short volatile
19257 char for signed while
19258 const goto sizeof _Bool
19259 continue if static _Complex
19260 default inline struct _Imaginary
19262 double long typedef
19263 else register union</pre>
19265 <h4><a name="A.1.3" href="#A.1.3">A.1.3 Identifiers</a></h4>
19266 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
19268 identifier-nondigit
19269 identifier identifier-nondigit
19270 identifier digit</pre>
19271 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
19274 universal-character-name
19275 other implementation-defined characters</pre>
19276 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
19278 _ a b c d e f g h i j k l m
19279 n o p q r s t u v w x y z
19280 A B C D E F G H I J K L M
19281 N O P Q R S T U V W X Y Z</pre>
19282 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
19284 0 1 2 3 4 5 6 7 8 9</pre>
19286 <h4><a name="A.1.4" href="#A.1.4">A.1.4 Universal character names</a></h4>
19287 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
19290 \U hex-quad hex-quad</pre>
19291 (<a href="#6.4.3">6.4.3</a>) hex-quad:
19293 hexadecimal-digit hexadecimal-digit
19294 hexadecimal-digit hexadecimal-digit</pre>
19296 <h4><a name="A.1.5" href="#A.1.5">A.1.5 Constants</a></h4>
19297 (<a href="#6.4.4">6.4.4</a>) constant:
19301 enumeration-constant
19302 character-constant</pre>
19303 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
19305 decimal-constant integer-suffixopt
19306 octal-constant integer-suffixopt
19307 hexadecimal-constant integer-suffixopt</pre>
19308 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
19312 decimal-constant digit</pre>
19313 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
19316 octal-constant octal-digit</pre>
19317 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
19319 hexadecimal-prefix hexadecimal-digit
19320 hexadecimal-constant hexadecimal-digit</pre>
19321 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
19324 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
19326 1 2 3 4 5 6 7 8 9</pre>
19327 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
19329 0 1 2 3 4 5 6 7</pre>
19330 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
19332 0 1 2 3 4 5 6 7 8 9
19335 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
19337 unsigned-suffix long-suffixopt
19338 unsigned-suffix long-long-suffix
19339 long-suffix unsigned-suffixopt
19340 long-long-suffix unsigned-suffixopt</pre>
19341 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
19344 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
19347 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
19350 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
19352 decimal-floating-constant
19353 hexadecimal-floating-constant</pre>
19354 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
19357 fractional-constant exponent-partopt floating-suffixopt
19358 digit-sequence exponent-part floating-suffixopt</pre>
19359 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
19361 hexadecimal-prefix hexadecimal-fractional-constant
19362 binary-exponent-part floating-suffixopt
19363 hexadecimal-prefix hexadecimal-digit-sequence
19364 binary-exponent-part floating-suffixopt</pre>
19365 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
19367 digit-sequenceopt . digit-sequence
19368 digit-sequence .</pre>
19369 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
19371 e signopt digit-sequence
19372 E signopt digit-sequence</pre>
19373 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
19376 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
19379 digit-sequence digit</pre>
19380 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
19382 hexadecimal-digit-sequenceopt .
19383 hexadecimal-digit-sequence
19384 hexadecimal-digit-sequence .</pre>
19385 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
19387 p signopt digit-sequence
19388 P signopt digit-sequence</pre>
19389 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
19392 hexadecimal-digit-sequence hexadecimal-digit</pre>
19393 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
19396 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
19399 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
19402 ' c-char-sequence '
19403 L' c-char-sequence '</pre>
19404 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
19407 c-char-sequence c-char</pre>
19408 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
19410 any member of the source character set except
19411 the single-quote ', backslash \, or new-line character
19412 escape-sequence</pre>
19413 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
19415 simple-escape-sequence
19416 octal-escape-sequence
19417 hexadecimal-escape-sequence
19418 universal-character-name</pre>
19419 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
19422 \a \b \f \n \r \t \v</pre>
19423 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
19426 \ octal-digit octal-digit
19427 \ octal-digit octal-digit octal-digit</pre>
19428 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
19430 \x hexadecimal-digit
19431 hexadecimal-escape-sequence hexadecimal-digit</pre>
19433 <h4><a name="A.1.6" href="#A.1.6">A.1.6 String literals</a></h4>
19434 (<a href="#6.4.5">6.4.5</a>) string-literal:
19436 " s-char-sequenceopt "
19437 L" s-char-sequenceopt "</pre>
19438 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
19441 s-char-sequence s-char</pre>
19442 (<a href="#6.4.5">6.4.5</a>) s-char:
19445 any member of the source character set except
19446 the double-quote ", backslash \, or new-line character
19447 escape-sequence</pre>
19449 <h4><a name="A.1.7" href="#A.1.7">A.1.7 Punctuators</a></h4>
19450 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
19452 [ ] ( ) { } . ->
19453 ++ -- & * + - ~ !
19454 / % << >> < > <= >= == != ^ | && ||
19456 = *= /= %= += -= <<= >>= &= ^= |=
19458 <: :> <% %> %: %:%:</pre>
19460 <h4><a name="A.1.8" href="#A.1.8">A.1.8 Header names</a></h4>
19461 (<a href="#6.4.7">6.4.7</a>) header-name:
19463 < h-char-sequence >
19464 " q-char-sequence "</pre>
19465 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
19468 h-char-sequence h-char</pre>
19469 (<a href="#6.4.7">6.4.7</a>) h-char:
19471 any member of the source character set except
19472 the new-line character and ></pre>
19473 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
19476 q-char-sequence q-char</pre>
19477 (<a href="#6.4.7">6.4.7</a>) q-char:
19479 any member of the source character set except
19480 the new-line character and "</pre>
19482 <h4><a name="A.1.9" href="#A.1.9">A.1.9 Preprocessing numbers</a></h4>
19483 (<a href="#6.4.8">6.4.8</a>) pp-number:
19489 pp-number identifier-nondigit
19496 <h3><a name="A.2" href="#A.2">A.2 Phrase structure grammar</a></h3>
19498 <h4><a name="A.2.1" href="#A.2.1">A.2.1 Expressions</a></h4>
19499 (<a href="#6.5.1">6.5.1</a>) primary-expression:
19504 ( expression )</pre>
19505 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
19508 postfix-expression [ expression ]
19509 postfix-expression ( argument-expression-listopt )
19510 postfix-expression . identifier
19511 postfix-expression -> identifier
19512 postfix-expression ++
19513 postfix-expression --
19514 ( type-name ) { initializer-list }
19515 ( type-name ) { initializer-list , }</pre>
19516 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
19518 assignment-expression
19519 argument-expression-list , assignment-expression</pre>
19520 (<a href="#6.5.3">6.5.3</a>) unary-expression:
19523 ++ unary-expression
19524 -- unary-expression
19525 unary-operator cast-expression
19526 sizeof unary-expression
19527 sizeof ( type-name )</pre>
19528 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
19530 & * + - ~ !</pre>
19531 (<a href="#6.5.4">6.5.4</a>) cast-expression:
19534 ( type-name ) cast-expression</pre>
19535 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
19539 multiplicative-expression * cast-expression
19540 multiplicative-expression / cast-expression
19541 multiplicative-expression % cast-expression</pre>
19542 (<a href="#6.5.6">6.5.6</a>) additive-expression:
19544 multiplicative-expression
19545 additive-expression + multiplicative-expression
19546 additive-expression - multiplicative-expression</pre>
19547 (<a href="#6.5.7">6.5.7</a>) shift-expression:
19549 additive-expression
19550 shift-expression << additive-expression
19551 shift-expression >> additive-expression</pre>
19552 (<a href="#6.5.8">6.5.8</a>) relational-expression:
19555 relational-expression < shift-expression
19556 relational-expression > shift-expression
19557 relational-expression <= shift-expression
19558 relational-expression >= shift-expression</pre>
19559 (<a href="#6.5.9">6.5.9</a>) equality-expression:
19561 relational-expression
19562 equality-expression == relational-expression
19563 equality-expression != relational-expression</pre>
19564 (<a href="#6.5.10">6.5.10</a>) AND-expression:
19566 equality-expression
19567 AND-expression & equality-expression</pre>
19568 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
19571 exclusive-OR-expression ^ AND-expression</pre>
19572 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
19574 exclusive-OR-expression
19575 inclusive-OR-expression | exclusive-OR-expression</pre>
19576 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
19578 inclusive-OR-expression
19579 logical-AND-expression && inclusive-OR-expression</pre>
19580 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
19582 logical-AND-expression
19583 logical-OR-expression || logical-AND-expression</pre>
19584 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
19587 logical-OR-expression
19588 logical-OR-expression ? expression : conditional-expression</pre>
19589 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
19591 conditional-expression
19592 unary-expression assignment-operator assignment-expression</pre>
19593 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
19595 = *= /= %= += -= <<= >>= &= ^= |=</pre>
19596 (<a href="#6.5.17">6.5.17</a>) expression:
19598 assignment-expression
19599 expression , assignment-expression</pre>
19600 (<a href="#6.6">6.6</a>) constant-expression:
19602 conditional-expression</pre>
19604 <h4><a name="A.2.2" href="#A.2.2">A.2.2 Declarations</a></h4>
19605 (<a href="#6.7">6.7</a>) declaration:
19607 declaration-specifiers init-declarator-listopt ;</pre>
19608 (<a href="#6.7">6.7</a>) declaration-specifiers:
19610 storage-class-specifier declaration-specifiersopt
19611 type-specifier declaration-specifiersopt
19612 type-qualifier declaration-specifiersopt
19613 function-specifier declaration-specifiersopt</pre>
19614 (<a href="#6.7">6.7</a>) init-declarator-list:
19617 init-declarator-list , init-declarator</pre>
19618 (<a href="#6.7">6.7</a>) init-declarator:
19621 declarator = initializer</pre>
19622 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
19630 (<a href="#6.7.2">6.7.2</a>) type-specifier:
19643 struct-or-union-specifier *
19646 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
19648 struct-or-union identifieropt { struct-declaration-list }
19649 struct-or-union identifier</pre>
19650 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
19654 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
19657 struct-declaration-list struct-declaration</pre>
19658 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
19660 specifier-qualifier-list struct-declarator-list ;</pre>
19661 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
19663 type-specifier specifier-qualifier-listopt
19664 type-qualifier specifier-qualifier-listopt</pre>
19665 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
19668 struct-declarator-list , struct-declarator</pre>
19669 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
19673 declaratoropt : constant-expression</pre>
19674 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
19676 enum identifieropt { enumerator-list }
19677 enum identifieropt { enumerator-list , }
19678 enum identifier</pre>
19679 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
19682 enumerator-list , enumerator</pre>
19683 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
19685 enumeration-constant
19686 enumeration-constant = constant-expression</pre>
19687 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
19692 (<a href="#6.7.4">6.7.4</a>) function-specifier:
19695 (<a href="#6.7.5">6.7.5</a>) declarator:
19697 pointeropt direct-declarator</pre>
19698 (<a href="#6.7.5">6.7.5</a>) direct-declarator:
19702 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
19703 direct-declarator [ static type-qualifier-listopt assignment-expression ]
19704 direct-declarator [ type-qualifier-list static assignment-expression ]
19705 direct-declarator [ type-qualifier-listopt * ]
19706 direct-declarator ( parameter-type-list )
19707 direct-declarator ( identifier-listopt )</pre>
19708 (<a href="#6.7.5">6.7.5</a>) pointer:
19710 * type-qualifier-listopt
19711 * type-qualifier-listopt pointer</pre>
19712 (<a href="#6.7.5">6.7.5</a>) type-qualifier-list:
19715 type-qualifier-list type-qualifier</pre>
19716 (<a href="#6.7.5">6.7.5</a>) parameter-type-list:
19720 parameter-list , ...</pre>
19721 (<a href="#6.7.5">6.7.5</a>) parameter-list:
19723 parameter-declaration
19724 parameter-list , parameter-declaration</pre>
19725 (<a href="#6.7.5">6.7.5</a>) parameter-declaration:
19727 declaration-specifiers declarator
19728 declaration-specifiers abstract-declaratoropt</pre>
19729 (<a href="#6.7.5">6.7.5</a>) identifier-list:
19732 identifier-list , identifier</pre>
19733 (<a href="#6.7.6">6.7.6</a>) type-name:
19735 specifier-qualifier-list abstract-declaratoropt</pre>
19736 (<a href="#6.7.6">6.7.6</a>) abstract-declarator:
19739 pointeropt direct-abstract-declarator</pre>
19740 (<a href="#6.7.6">6.7.6</a>) direct-abstract-declarator:
19742 ( abstract-declarator )
19743 direct-abstract-declaratoropt [ type-qualifier-listopt
19744 assignment-expressionopt ]
19745 direct-abstract-declaratoropt [ static type-qualifier-listopt
19746 assignment-expression ]
19747 direct-abstract-declaratoropt [ type-qualifier-list static
19748 assignment-expression ]
19749 direct-abstract-declaratoropt [ * ]
19750 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
19751 (<a href="#6.7.7">6.7.7</a>) typedef-name:
19754 (<a href="#6.7.8">6.7.8</a>) initializer:
19756 assignment-expression
19757 { initializer-list }
19758 { initializer-list , }</pre>
19759 (<a href="#6.7.8">6.7.8</a>) initializer-list:
19761 designationopt initializer
19762 initializer-list , designationopt initializer</pre>
19763 (<a href="#6.7.8">6.7.8</a>) designation:
19766 designator-list =</pre>
19767 (<a href="#6.7.8">6.7.8</a>) designator-list:
19770 designator-list designator</pre>
19771 (<a href="#6.7.8">6.7.8</a>) designator:
19773 [ constant-expression ]
19776 <h4><a name="A.2.3" href="#A.2.3">A.2.3 Statements</a></h4>
19777 (<a href="#6.8">6.8</a>) statement:
19781 expression-statement
19782 selection-statement
19783 iteration-statement
19784 jump-statement</pre>
19785 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
19787 identifier : statement
19788 case constant-expression : statement
19789 default : statement</pre>
19790 (<a href="#6.8.2">6.8.2</a>) compound-statement:
19792 { block-item-listopt }</pre>
19793 (<a href="#6.8.2">6.8.2</a>) block-item-list:
19796 block-item-list block-item</pre>
19797 (<a href="#6.8.2">6.8.2</a>) block-item:
19801 (<a href="#6.8.3">6.8.3</a>) expression-statement:
19803 expressionopt ;</pre>
19804 (<a href="#6.8.4">6.8.4</a>) selection-statement:
19807 if ( expression ) statement
19808 if ( expression ) statement else statement
19809 switch ( expression ) statement</pre>
19810 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
19812 while ( expression ) statement
19813 do statement while ( expression ) ;
19814 for ( expressionopt ; expressionopt ; expressionopt ) statement
19815 for ( declaration expressionopt ; expressionopt ) statement</pre>
19816 (<a href="#6.8.6">6.8.6</a>) jump-statement:
19821 return expressionopt ;</pre>
19823 <h4><a name="A.2.4" href="#A.2.4">A.2.4 External definitions</a></h4>
19824 (<a href="#6.9">6.9</a>) translation-unit:
19826 external-declaration
19827 translation-unit external-declaration</pre>
19828 (<a href="#6.9">6.9</a>) external-declaration:
19830 function-definition
19832 (<a href="#6.9.1">6.9.1</a>) function-definition:
19834 declaration-specifiers declarator declaration-listopt compound-statement</pre>
19835 (<a href="#6.9.1">6.9.1</a>) declaration-list:
19838 declaration-list declaration</pre>
19840 <h3><a name="A.3" href="#A.3">A.3 Preprocessing directives</a></h3>
19841 (<a href="#6.10">6.10</a>) preprocessing-file:
19844 (<a href="#6.10">6.10</a>) group:
19847 group group-part</pre>
19848 (<a href="#6.10">6.10</a>) group-part:
19853 # non-directive</pre>
19854 (<a href="#6.10">6.10</a>) if-section:
19857 if-group elif-groupsopt else-groupopt endif-line</pre>
19858 (<a href="#6.10">6.10</a>) if-group:
19860 # if constant-expression new-line groupopt
19861 # ifdef identifier new-line groupopt
19862 # ifndef identifier new-line groupopt</pre>
19863 (<a href="#6.10">6.10</a>) elif-groups:
19866 elif-groups elif-group</pre>
19867 (<a href="#6.10">6.10</a>) elif-group:
19869 # elif constant-expression new-line groupopt</pre>
19870 (<a href="#6.10">6.10</a>) else-group:
19872 # else new-line groupopt</pre>
19873 (<a href="#6.10">6.10</a>) endif-line:
19875 # endif new-line</pre>
19876 (<a href="#6.10">6.10</a>) control-line:
19878 # include pp-tokens new-line
19879 # define identifier replacement-list new-line
19880 # define identifier lparen identifier-listopt )
19881 replacement-list new-line
19882 # define identifier lparen ... ) replacement-list new-line
19883 # define identifier lparen identifier-list , ... )
19884 replacement-list new-line
19885 # undef identifier new-line
19886 # line pp-tokens new-line
19887 # error pp-tokensopt new-line
19888 # pragma pp-tokensopt new-line
19890 (<a href="#6.10">6.10</a>) text-line:
19892 pp-tokensopt new-line</pre>
19893 (<a href="#6.10">6.10</a>) non-directive:
19895 pp-tokens new-line</pre>
19896 (<a href="#6.10">6.10</a>) lparen:
19898 a ( character not immediately preceded by white-space</pre>
19899 (<a href="#6.10">6.10</a>) replacement-list:
19903 (<a href="#6.10">6.10</a>) pp-tokens:
19905 preprocessing-token
19906 pp-tokens preprocessing-token</pre>
19907 (<a href="#6.10">6.10</a>) new-line:
19910 the new-line character</pre>
19912 <h2><a name="B" href="#B">Annex B</a></h2>
19915 Library summary</pre>
19917 <h3><a name="B.1" href="#B.1">B.1 Diagnostics <assert.h></a></h3>
19920 void assert(scalar expression);</pre>
19922 <h3><a name="B.2" href="#B.2">B.2 Complex <complex.h></a></h3>
19926 complex imaginary I
19927 _Complex_I _Imaginary_I
19928 #pragma STDC CX_LIMITED_RANGE on-off-switch
19929 double complex cacos(double complex z);
19930 float complex cacosf(float complex z);
19931 long double complex cacosl(long double complex z);
19932 double complex casin(double complex z);
19933 float complex casinf(float complex z);
19934 long double complex casinl(long double complex z);
19935 double complex catan(double complex z);
19936 float complex catanf(float complex z);
19937 long double complex catanl(long double complex z);
19938 double complex ccos(double complex z);
19939 float complex ccosf(float complex z);
19940 long double complex ccosl(long double complex z);
19941 double complex csin(double complex z);
19942 float complex csinf(float complex z);
19943 long double complex csinl(long double complex z);
19944 double complex ctan(double complex z);
19945 float complex ctanf(float complex z);
19946 long double complex ctanl(long double complex z);
19947 double complex cacosh(double complex z);
19948 float complex cacoshf(float complex z);
19949 long double complex cacoshl(long double complex z);
19950 double complex casinh(double complex z);
19951 float complex casinhf(float complex z);
19952 long double complex casinhl(long double complex z);
19953 double complex catanh(double complex z);
19954 float complex catanhf(float complex z);
19955 long double complex catanhl(long double complex z);
19956 double complex ccosh(double complex z);
19957 float complex ccoshf(float complex z);
19958 long double complex ccoshl(long double complex z);
19959 double complex csinh(double complex z);
19960 float complex csinhf(float complex z);
19961 long double complex csinhl(long double complex z);
19962 double complex ctanh(double complex z);
19963 float complex ctanhf(float complex z);
19964 long double complex ctanhl(long double complex z);
19965 double complex cexp(double complex z);
19966 float complex cexpf(float complex z);
19967 long double complex cexpl(long double complex z);
19968 double complex clog(double complex z);
19969 float complex clogf(float complex z);
19970 long double complex clogl(long double complex z);
19971 double cabs(double complex z);
19972 float cabsf(float complex z);
19973 long double cabsl(long double complex z);
19974 double complex cpow(double complex x, double complex y);
19975 float complex cpowf(float complex x, float complex y);
19976 long double complex cpowl(long double complex x,
19977 long double complex y);
19978 double complex csqrt(double complex z);
19979 float complex csqrtf(float complex z);
19980 long double complex csqrtl(long double complex z);
19981 double carg(double complex z);
19982 float cargf(float complex z);
19983 long double cargl(long double complex z);
19984 double cimag(double complex z);
19985 float cimagf(float complex z);
19986 long double cimagl(long double complex z);
19987 double complex conj(double complex z);
19988 float complex conjf(float complex z);
19989 long double complex conjl(long double complex z);
19990 double complex cproj(double complex z);
19991 float complex cprojf(float complex z);
19992 long double complex cprojl(long double complex z);
19993 double creal(double complex z);
19994 float crealf(float complex z);
19995 long double creall(long double complex z);</pre>
19997 <h3><a name="B.3" href="#B.3">B.3 Character handling <ctype.h></a></h3>
19999 int isalnum(int c);
20000 int isalpha(int c);
20001 int isblank(int c);
20002 int iscntrl(int c);
20003 int isdigit(int c);
20004 int isgraph(int c);
20005 int islower(int c);
20006 int isprint(int c);
20007 int ispunct(int c);
20008 int isspace(int c);
20009 int isupper(int c);
20010 int isxdigit(int c);
20011 int tolower(int c);
20012 int toupper(int c);</pre>
20014 <h3><a name="B.4" href="#B.4">B.4 Errors <errno.h></a></h3>
20016 EDOM EILSEQ ERANGE errno</pre>
20018 <h3><a name="B.5" href="#B.5">B.5 Floating-point environment <fenv.h></a></h3>
20021 fenv_t FE_OVERFLOW FE_TOWARDZERO
20022 fexcept_t FE_UNDERFLOW FE_UPWARD
20023 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
20024 FE_INEXACT FE_DOWNWARD
20025 FE_INVALID FE_TONEAREST
20026 #pragma STDC FENV_ACCESS on-off-switch
20027 int feclearexcept(int excepts);
20028 int fegetexceptflag(fexcept_t *flagp, int excepts);
20029 int feraiseexcept(int excepts);
20030 int fesetexceptflag(const fexcept_t *flagp,
20032 int fetestexcept(int excepts);
20033 int fegetround(void);
20034 int fesetround(int round);
20035 int fegetenv(fenv_t *envp);
20036 int feholdexcept(fenv_t *envp);
20037 int fesetenv(const fenv_t *envp);
20038 int feupdateenv(const fenv_t *envp);</pre>
20040 <h3><a name="B.6" href="#B.6">B.6 Characteristics of floating types <float.h></a></h3>
20042 FLT_ROUNDS DBL_MIN_EXP FLT_MAX
20043 FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
20044 FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
20045 FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
20046 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
20047 LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
20048 DECIMAL_DIG DBL_MAX_EXP FLT_MIN
20049 FLT_DIG LDBL_MAX_EXP DBL_MIN
20050 DBL_DIG FLT_MAX_10_EXP LDBL_MIN
20051 LDBL_DIG DBL_MAX_10_EXP
20052 FLT_MIN_EXP LDBL_MAX_10_EXP</pre>
20054 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
20058 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
20059 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
20060 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
20061 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
20062 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
20063 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
20064 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
20065 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
20066 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
20067 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
20068 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
20069 intmax_t imaxabs(intmax_t j);
20070 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
20071 intmax_t strtoimax(const char * restrict nptr,
20072 char ** restrict endptr, int base);
20073 uintmax_t strtoumax(const char * restrict nptr,
20074 char ** restrict endptr, int base);
20075 intmax_t wcstoimax(const wchar_t * restrict nptr,
20076 wchar_t ** restrict endptr, int base);
20077 uintmax_t wcstoumax(const wchar_t * restrict nptr,
20078 wchar_t ** restrict endptr, int base);</pre>
20080 <h3><a name="B.8" href="#B.8">B.8 Alternative spellings <iso646.h></a></h3>
20082 and bitor not_eq xor
20083 and_eq compl or xor_eq
20084 bitand not or_eq</pre>
20086 <h3><a name="B.9" href="#B.9">B.9 Sizes of integer types <limits.h></a></h3>
20088 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
20089 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
20090 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
20091 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
20092 CHAR_MIN USHRT_MAX LONG_MAX</pre>
20094 <h3><a name="B.10" href="#B.10">B.10 Localization <locale.h></a></h3>
20096 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
20097 NULL LC_COLLATE LC_MONETARY LC_TIME
20098 char *setlocale(int category, const char *locale);
20099 struct lconv *localeconv(void);</pre>
20101 <h3><a name="B.11" href="#B.11">B.11 Mathematics <math.h></a></h3>
20108 float_t FP_INFINITE FP_FAST_FMAL
20109 double_t FP_NAN FP_ILOGB0
20110 HUGE_VAL FP_NORMAL FP_ILOGBNAN
20111 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
20112 HUGE_VALL FP_ZERO MATH_ERREXCEPT
20113 INFINITY FP_FAST_FMA math_errhandling
20115 #pragma STDC FP_CONTRACT on-off-switch
20116 int fpclassify(real-floating x);
20117 int isfinite(real-floating x);
20118 int isinf(real-floating x);
20119 int isnan(real-floating x);
20120 int isnormal(real-floating x);
20121 int signbit(real-floating x);
20122 double acos(double x);
20123 float acosf(float x);
20124 long double acosl(long double x);
20125 double asin(double x);
20126 float asinf(float x);
20127 long double asinl(long double x);
20128 double atan(double x);
20129 float atanf(float x);
20130 long double atanl(long double x);
20131 double atan2(double y, double x);
20132 float atan2f(float y, float x);
20133 long double atan2l(long double y, long double x);
20134 double cos(double x);
20135 float cosf(float x);
20136 long double cosl(long double x);
20137 double sin(double x);
20138 float sinf(float x);
20139 long double sinl(long double x);
20140 double tan(double x);
20141 float tanf(float x);
20142 long double tanl(long double x);
20143 double acosh(double x);
20144 float acoshf(float x);
20145 long double acoshl(long double x);
20146 double asinh(double x);
20147 float asinhf(float x);
20148 long double asinhl(long double x);
20149 double atanh(double x);
20150 float atanhf(float x);
20151 long double atanhl(long double x);
20152 double cosh(double x);
20153 float coshf(float x);
20154 long double coshl(long double x);
20155 double sinh(double x);
20156 float sinhf(float x);
20157 long double sinhl(long double x);
20158 double tanh(double x);
20159 float tanhf(float x);
20160 long double tanhl(long double x);
20161 double exp(double x);
20162 float expf(float x);
20163 long double expl(long double x);
20164 double exp2(double x);
20165 float exp2f(float x);
20166 long double exp2l(long double x);
20167 double expm1(double x);
20168 float expm1f(float x);
20169 long double expm1l(long double x);
20170 double frexp(double value, int *exp);
20171 float frexpf(float value, int *exp);
20172 long double frexpl(long double value, int *exp);
20173 int ilogb(double x);
20174 int ilogbf(float x);
20175 int ilogbl(long double x);
20176 double ldexp(double x, int exp);
20177 float ldexpf(float x, int exp);
20178 long double ldexpl(long double x, int exp);
20179 double log(double x);
20180 float logf(float x);
20181 long double logl(long double x);
20182 double log10(double x);
20183 float log10f(float x);
20184 long double log10l(long double x);
20185 double log1p(double x);
20186 float log1pf(float x);
20187 long double log1pl(long double x);
20188 double log2(double x);
20189 float log2f(float x);
20190 long double log2l(long double x);
20191 double logb(double x);
20192 float logbf(float x);
20193 long double logbl(long double x);
20194 double modf(double value, double *iptr);
20195 float modff(float value, float *iptr);
20196 long double modfl(long double value, long double *iptr);
20197 double scalbn(double x, int n);
20198 float scalbnf(float x, int n);
20199 long double scalbnl(long double x, int n);
20200 double scalbln(double x, long int n);
20201 float scalblnf(float x, long int n);
20202 long double scalblnl(long double x, long int n);
20203 double cbrt(double x);
20204 float cbrtf(float x);
20205 long double cbrtl(long double x);
20206 double fabs(double x);
20207 float fabsf(float x);
20208 long double fabsl(long double x);
20209 double hypot(double x, double y);
20210 float hypotf(float x, float y);
20211 long double hypotl(long double x, long double y);
20212 double pow(double x, double y);
20213 float powf(float x, float y);
20214 long double powl(long double x, long double y);
20215 double sqrt(double x);
20216 float sqrtf(float x);
20217 long double sqrtl(long double x);
20218 double erf(double x);
20219 float erff(float x);
20220 long double erfl(long double x);
20221 double erfc(double x);
20222 float erfcf(float x);
20223 long double erfcl(long double x);
20224 double lgamma(double x);
20225 float lgammaf(float x);
20226 long double lgammal(long double x);
20227 double tgamma(double x);
20228 float tgammaf(float x);
20229 long double tgammal(long double x);
20230 double ceil(double x);
20231 float ceilf(float x);
20232 long double ceill(long double x);
20233 double floor(double x);
20234 float floorf(float x);
20235 long double floorl(long double x);
20236 double nearbyint(double x);
20237 float nearbyintf(float x);
20238 long double nearbyintl(long double x);
20239 double rint(double x);
20240 float rintf(float x);
20241 long double rintl(long double x);
20242 long int lrint(double x);
20243 long int lrintf(float x);
20244 long int lrintl(long double x);
20245 long long int llrint(double x);
20246 long long int llrintf(float x);
20247 long long int llrintl(long double x);
20248 double round(double x);
20249 float roundf(float x);
20250 long double roundl(long double x);
20251 long int lround(double x);
20252 long int lroundf(float x);
20253 long int lroundl(long double x);
20254 long long int llround(double x);
20255 long long int llroundf(float x);
20256 long long int llroundl(long double x);
20257 double trunc(double x);
20258 float truncf(float x);
20259 long double truncl(long double x);
20260 double fmod(double x, double y);
20261 float fmodf(float x, float y);
20262 long double fmodl(long double x, long double y);
20263 double remainder(double x, double y);
20264 float remainderf(float x, float y);
20265 long double remainderl(long double x, long double y);
20266 double remquo(double x, double y, int *quo);
20267 float remquof(float x, float y, int *quo);
20268 long double remquol(long double x, long double y,
20270 double copysign(double x, double y);
20271 float copysignf(float x, float y);
20272 long double copysignl(long double x, long double y);
20273 double nan(const char *tagp);
20274 float nanf(const char *tagp);
20275 long double nanl(const char *tagp);
20276 double nextafter(double x, double y);
20277 float nextafterf(float x, float y);
20278 long double nextafterl(long double x, long double y);
20279 double nexttoward(double x, long double y);
20280 float nexttowardf(float x, long double y);
20281 long double nexttowardl(long double x, long double y);
20282 double fdim(double x, double y);
20283 float fdimf(float x, float y);
20284 long double fdiml(long double x, long double y);
20285 double fmax(double x, double y);
20286 float fmaxf(float x, float y);
20287 long double fmaxl(long double x, long double y);
20288 double fmin(double x, double y);
20289 float fminf(float x, float y);
20290 long double fminl(long double x, long double y);
20291 double fma(double x, double y, double z);
20292 float fmaf(float x, float y, float z);
20293 long double fmal(long double x, long double y,
20295 int isgreater(real-floating x, real-floating y);
20296 int isgreaterequal(real-floating x, real-floating y);
20297 int isless(real-floating x, real-floating y);
20298 int islessequal(real-floating x, real-floating y);
20299 int islessgreater(real-floating x, real-floating y);
20300 int isunordered(real-floating x, real-floating y);</pre>
20302 <h3><a name="B.12" href="#B.12">B.12 Nonlocal jumps <setjmp.h></a></h3>
20305 int setjmp(jmp_buf env);
20306 void longjmp(jmp_buf env, int val);</pre>
20308 <h3><a name="B.13" href="#B.13">B.13 Signal handling <signal.h></a></h3>
20310 sig_atomic_t SIG_IGN SIGILL SIGTERM
20311 SIG_DFL SIGABRT SIGINT
20312 SIG_ERR SIGFPE SIGSEGV
20313 void (*signal(int sig, void (*func)(int)))(int);
20314 int raise(int sig);</pre>
20316 <h3><a name="B.14" href="#B.14">B.14 Variable arguments <stdarg.h></a></h3>
20319 type va_arg(va_list ap, type);
20320 void va_copy(va_list dest, va_list src);
20321 void va_end(va_list ap);
20322 void va_start(va_list ap, parmN);</pre>
20324 <h3><a name="B.15" href="#B.15">B.15 Boolean type and values <stdbool.h></a></h3>
20330 __bool_true_false_are_defined</pre>
20332 <h3><a name="B.16" href="#B.16">B.16 Common definitions <stddef.h></a></h3>
20334 ptrdiff_t size_t wchar_t NULL
20335 offsetof(type, member-designator)</pre>
20337 <h3><a name="B.17" href="#B.17">B.17 Integer types <stdint.h></a></h3>
20339 intN_t INT_LEASTN_MIN PTRDIFF_MAX
20340 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
20341 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
20342 uint_leastN_t INT_FASTN_MIN SIZE_MAX
20343 int_fastN_t INT_FASTN_MAX WCHAR_MIN
20344 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
20345 intptr_t INTPTR_MIN WINT_MIN
20346 uintptr_t INTPTR_MAX WINT_MAX
20347 intmax_t UINTPTR_MAX INTN_C(value)
20348 uintmax_t INTMAX_MIN UINTN_C(value)
20349 INTN_MIN INTMAX_MAX INTMAX_C(value)
20350 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
20351 UINTN_MAX PTRDIFF_MIN</pre>
20353 <h3><a name="B.18" href="#B.18">B.18 Input/output <stdio.h></a></h3>
20357 size_t _IOLBF FILENAME_MAX TMP_MAX
20358 FILE _IONBF L_tmpnam stderr
20359 fpos_t BUFSIZ SEEK_CUR stdin
20360 NULL EOF SEEK_END stdout
20361 _IOFBF FOPEN_MAX SEEK_SET
20362 int remove(const char *filename);
20363 int rename(const char *old, const char *new);
20364 FILE *tmpfile(void);
20365 char *tmpnam(char *s);
20366 int fclose(FILE *stream);
20367 int fflush(FILE *stream);
20368 FILE *fopen(const char * restrict filename,
20369 const char * restrict mode);
20370 FILE *freopen(const char * restrict filename,
20371 const char * restrict mode,
20372 FILE * restrict stream);
20373 void setbuf(FILE * restrict stream,
20374 char * restrict buf);
20375 int setvbuf(FILE * restrict stream,
20376 char * restrict buf,
20377 int mode, size_t size);
20378 int fprintf(FILE * restrict stream,
20379 const char * restrict format, ...);
20380 int fscanf(FILE * restrict stream,
20381 const char * restrict format, ...);
20382 int printf(const char * restrict format, ...);
20383 int scanf(const char * restrict format, ...);
20384 int snprintf(char * restrict s, size_t n,
20385 const char * restrict format, ...);
20386 int sprintf(char * restrict s,
20387 const char * restrict format, ...);
20388 int sscanf(const char * restrict s,
20389 const char * restrict format, ...);
20390 int vfprintf(FILE * restrict stream,
20391 const char * restrict format, va_list arg);
20392 int vfscanf(FILE * restrict stream,
20393 const char * restrict format, va_list arg);
20394 int vprintf(const char * restrict format, va_list arg);
20395 int vscanf(const char * restrict format, va_list arg);
20396 int vsnprintf(char * restrict s, size_t n,
20397 const char * restrict format, va_list arg);
20398 int vsprintf(char * restrict s,
20399 const char * restrict format, va_list arg);
20400 int vsscanf(const char * restrict s,
20401 const char * restrict format, va_list arg);
20402 int fgetc(FILE *stream);
20403 char *fgets(char * restrict s, int n,
20404 FILE * restrict stream);
20405 int fputc(int c, FILE *stream);
20406 int fputs(const char * restrict s,
20407 FILE * restrict stream);
20408 int getc(FILE *stream);
20410 char *gets(char *s);
20411 int putc(int c, FILE *stream);
20412 int putchar(int c);
20413 int puts(const char *s);
20414 int ungetc(int c, FILE *stream);
20415 size_t fread(void * restrict ptr,
20416 size_t size, size_t nmemb,
20417 FILE * restrict stream);
20418 size_t fwrite(const void * restrict ptr,
20419 size_t size, size_t nmemb,
20420 FILE * restrict stream);
20421 int fgetpos(FILE * restrict stream,
20422 fpos_t * restrict pos);
20423 int fseek(FILE *stream, long int offset, int whence);
20424 int fsetpos(FILE *stream, const fpos_t *pos);
20425 long int ftell(FILE *stream);
20426 void rewind(FILE *stream);
20427 void clearerr(FILE *stream);
20428 int feof(FILE *stream);
20429 int ferror(FILE *stream);
20430 void perror(const char *s);</pre>
20432 <h3><a name="B.19" href="#B.19">B.19 General utilities <stdlib.h></a></h3>
20436 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
20437 wchar_t lldiv_t EXIT_SUCCESS
20438 div_t NULL RAND_MAX
20439 double atof(const char *nptr);
20440 int atoi(const char *nptr);
20441 long int atol(const char *nptr);
20442 long long int atoll(const char *nptr);
20443 double strtod(const char * restrict nptr,
20444 char ** restrict endptr);
20445 float strtof(const char * restrict nptr,
20446 char ** restrict endptr);
20447 long double strtold(const char * restrict nptr,
20448 char ** restrict endptr);
20449 long int strtol(const char * restrict nptr,
20450 char ** restrict endptr, int base);
20451 long long int strtoll(const char * restrict nptr,
20452 char ** restrict endptr, int base);
20453 unsigned long int strtoul(
20454 const char * restrict nptr,
20455 char ** restrict endptr, int base);
20456 unsigned long long int strtoull(
20457 const char * restrict nptr,
20458 char ** restrict endptr, int base);
20460 void srand(unsigned int seed);
20461 void *calloc(size_t nmemb, size_t size);
20462 void free(void *ptr);
20463 void *malloc(size_t size);
20464 void *realloc(void *ptr, size_t size);
20466 int atexit(void (*func)(void));
20467 void exit(int status);
20468 void _Exit(int status);
20469 char *getenv(const char *name);
20470 int system(const char *string);
20471 void *bsearch(const void *key, const void *base,
20472 size_t nmemb, size_t size,
20473 int (*compar)(const void *, const void *));
20474 void qsort(void *base, size_t nmemb, size_t size,
20475 int (*compar)(const void *, const void *));
20477 long int labs(long int j);
20478 long long int llabs(long long int j);
20479 div_t div(int numer, int denom);
20480 ldiv_t ldiv(long int numer, long int denom);
20481 lldiv_t lldiv(long long int numer,
20482 long long int denom);
20483 int mblen(const char *s, size_t n);
20484 int mbtowc(wchar_t * restrict pwc,
20485 const char * restrict s, size_t n);
20486 int wctomb(char *s, wchar_t wchar);
20487 size_t mbstowcs(wchar_t * restrict pwcs,
20488 const char * restrict s, size_t n);
20489 size_t wcstombs(char * restrict s,
20490 const wchar_t * restrict pwcs, size_t n);</pre>
20492 <h3><a name="B.20" href="#B.20">B.20 String handling <string.h></a></h3>
20497 void *memcpy(void * restrict s1,
20498 const void * restrict s2, size_t n);
20499 void *memmove(void *s1, const void *s2, size_t n);
20500 char *strcpy(char * restrict s1,
20501 const char * restrict s2);
20502 char *strncpy(char * restrict s1,
20503 const char * restrict s2, size_t n);
20504 char *strcat(char * restrict s1,
20505 const char * restrict s2);
20506 char *strncat(char * restrict s1,
20507 const char * restrict s2, size_t n);
20508 int memcmp(const void *s1, const void *s2, size_t n);
20509 int strcmp(const char *s1, const char *s2);
20510 int strcoll(const char *s1, const char *s2);
20511 int strncmp(const char *s1, const char *s2, size_t n);
20512 size_t strxfrm(char * restrict s1,
20513 const char * restrict s2, size_t n);
20514 void *memchr(const void *s, int c, size_t n);
20515 char *strchr(const char *s, int c);
20516 size_t strcspn(const char *s1, const char *s2);
20517 char *strpbrk(const char *s1, const char *s2);
20518 char *strrchr(const char *s, int c);
20519 size_t strspn(const char *s1, const char *s2);
20520 char *strstr(const char *s1, const char *s2);
20521 char *strtok(char * restrict s1,
20522 const char * restrict s2);
20523 void *memset(void *s, int c, size_t n);
20524 char *strerror(int errnum);
20525 size_t strlen(const char *s);</pre>
20527 <h3><a name="B.21" href="#B.21">B.21 Type-generic math <tgmath.h></a></h3>
20529 acos sqrt fmod nextafter
20530 asin fabs frexp nexttoward
20531 atan atan2 hypot remainder
20532 acosh cbrt ilogb remquo
20533 asinh ceil ldexp rint
20534 atanh copysign lgamma round
20535 cos erf llrint scalbn
20536 sin erfc llround scalbln
20537 tan exp2 log10 tgamma
20538 cosh expm1 log1p trunc
20539 sinh fdim log2 carg
20540 tanh floor logb cimag
20542 log fmax lround cproj
20543 pow fmin nearbyint creal</pre>
20545 <h3><a name="B.22" href="#B.22">B.22 Date and time <time.h></a></h3>
20549 CLOCKS_PER_SEC clock_t struct tm
20550 clock_t clock(void);
20551 double difftime(time_t time1, time_t time0);
20552 time_t mktime(struct tm *timeptr);
20553 time_t time(time_t *timer);
20554 char *asctime(const struct tm *timeptr);
20555 char *ctime(const time_t *timer);
20556 struct tm *gmtime(const time_t *timer);
20557 struct tm *localtime(const time_t *timer);
20558 size_t strftime(char * restrict s,
20560 const char * restrict format,
20561 const struct tm * restrict timeptr);</pre>
20563 <h3><a name="B.23" href="#B.23">B.23 Extended multibyte/wide character utilities <wchar.h></a></h3>
20567 wchar_t wint_t WCHAR_MAX
20568 size_t struct tm WCHAR_MIN
20569 mbstate_t NULL WEOF
20570 int fwprintf(FILE * restrict stream,
20571 const wchar_t * restrict format, ...);
20572 int fwscanf(FILE * restrict stream,
20573 const wchar_t * restrict format, ...);
20574 int swprintf(wchar_t * restrict s, size_t n,
20575 const wchar_t * restrict format, ...);
20576 int swscanf(const wchar_t * restrict s,
20577 const wchar_t * restrict format, ...);
20578 int vfwprintf(FILE * restrict stream,
20579 const wchar_t * restrict format, va_list arg);
20580 int vfwscanf(FILE * restrict stream,
20581 const wchar_t * restrict format, va_list arg);
20582 int vswprintf(wchar_t * restrict s, size_t n,
20583 const wchar_t * restrict format, va_list arg);
20584 int vswscanf(const wchar_t * restrict s,
20585 const wchar_t * restrict format, va_list arg);
20586 int vwprintf(const wchar_t * restrict format,
20588 int vwscanf(const wchar_t * restrict format,
20590 int wprintf(const wchar_t * restrict format, ...);
20591 int wscanf(const wchar_t * restrict format, ...);
20592 wint_t fgetwc(FILE *stream);
20593 wchar_t *fgetws(wchar_t * restrict s, int n,
20594 FILE * restrict stream);
20595 wint_t fputwc(wchar_t c, FILE *stream);
20596 int fputws(const wchar_t * restrict s,
20597 FILE * restrict stream);
20598 int fwide(FILE *stream, int mode);
20599 wint_t getwc(FILE *stream);
20600 wint_t getwchar(void);
20601 wint_t putwc(wchar_t c, FILE *stream);
20602 wint_t putwchar(wchar_t c);
20603 wint_t ungetwc(wint_t c, FILE *stream);
20604 double wcstod(const wchar_t * restrict nptr,
20605 wchar_t ** restrict endptr);
20606 float wcstof(const wchar_t * restrict nptr,
20607 wchar_t ** restrict endptr);
20608 long double wcstold(const wchar_t * restrict nptr,
20609 wchar_t ** restrict endptr);
20610 long int wcstol(const wchar_t * restrict nptr,
20611 wchar_t ** restrict endptr, int base);
20612 long long int wcstoll(const wchar_t * restrict nptr,
20613 wchar_t ** restrict endptr, int base);
20614 unsigned long int wcstoul(const wchar_t * restrict nptr,
20615 wchar_t ** restrict endptr, int base);
20616 unsigned long long int wcstoull(
20617 const wchar_t * restrict nptr,
20618 wchar_t ** restrict endptr, int base);
20619 wchar_t *wcscpy(wchar_t * restrict s1,
20620 const wchar_t * restrict s2);
20621 wchar_t *wcsncpy(wchar_t * restrict s1,
20622 const wchar_t * restrict s2, size_t n);
20623 wchar_t *wmemcpy(wchar_t * restrict s1,
20624 const wchar_t * restrict s2, size_t n);
20625 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
20627 wchar_t *wcscat(wchar_t * restrict s1,
20628 const wchar_t * restrict s2);
20629 wchar_t *wcsncat(wchar_t * restrict s1,
20630 const wchar_t * restrict s2, size_t n);
20631 int wcscmp(const wchar_t *s1, const wchar_t *s2);
20632 int wcscoll(const wchar_t *s1, const wchar_t *s2);
20633 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
20635 size_t wcsxfrm(wchar_t * restrict s1,
20636 const wchar_t * restrict s2, size_t n);
20637 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
20639 wchar_t *wcschr(const wchar_t *s, wchar_t c);
20640 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
20641 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2); *
20642 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
20643 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
20644 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
20645 wchar_t *wcstok(wchar_t * restrict s1,
20646 const wchar_t * restrict s2,
20647 wchar_t ** restrict ptr);
20648 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
20649 size_t wcslen(const wchar_t *s);
20650 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
20651 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
20652 const wchar_t * restrict format,
20653 const struct tm * restrict timeptr);
20654 wint_t btowc(int c);
20655 int wctob(wint_t c);
20656 int mbsinit(const mbstate_t *ps);
20657 size_t mbrlen(const char * restrict s, size_t n,
20658 mbstate_t * restrict ps);
20659 size_t mbrtowc(wchar_t * restrict pwc,
20660 const char * restrict s, size_t n,
20661 mbstate_t * restrict ps);
20662 size_t wcrtomb(char * restrict s, wchar_t wc,
20663 mbstate_t * restrict ps);
20664 size_t mbsrtowcs(wchar_t * restrict dst,
20665 const char ** restrict src, size_t len,
20666 mbstate_t * restrict ps);
20667 size_t wcsrtombs(char * restrict dst,
20668 const wchar_t ** restrict src, size_t len,
20669 mbstate_t * restrict ps);</pre>
20671 <h3><a name="B.24" href="#B.24">B.24 Wide character classification and mapping utilities <wctype.h></a></h3>
20675 wint_t wctrans_t wctype_t WEOF
20676 int iswalnum(wint_t wc);
20677 int iswalpha(wint_t wc);
20678 int iswblank(wint_t wc);
20679 int iswcntrl(wint_t wc);
20680 int iswdigit(wint_t wc);
20681 int iswgraph(wint_t wc);
20682 int iswlower(wint_t wc);
20683 int iswprint(wint_t wc);
20684 int iswpunct(wint_t wc);
20685 int iswspace(wint_t wc);
20686 int iswupper(wint_t wc);
20687 int iswxdigit(wint_t wc);
20688 int iswctype(wint_t wc, wctype_t desc);
20689 wctype_t wctype(const char *property);
20690 wint_t towlower(wint_t wc);
20691 wint_t towupper(wint_t wc);
20692 wint_t towctrans(wint_t wc, wctrans_t desc);
20693 wctrans_t wctrans(const char *property);</pre>
20695 <h2><a name="C" href="#C">Annex C</a></h2>
20699 Sequence points</pre>
20700 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
20702 <li> The call to a function, after the arguments have been evaluated (<a href="#6.5.2.2">6.5.2.2</a>).
20703 <li> The end of the first operand of the following operators: logical AND && (<a href="#6.5.13">6.5.13</a>);
20704 logical OR || (<a href="#6.5.14">6.5.14</a>); conditional ? (<a href="#6.5.15">6.5.15</a>); comma , (<a href="#6.5.17">6.5.17</a>).
20705 <li> The end of a full declarator: declarators (<a href="#6.7.5">6.7.5</a>);
20706 <li> The end of a full expression: an initializer (<a href="#6.7.8">6.7.8</a>); the expression in an expression
20707 statement (<a href="#6.8.3">6.8.3</a>); the controlling expression of a selection statement (if or switch)
20708 (<a href="#6.8.4">6.8.4</a>); the controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the
20709 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the expression in a return statement
20710 (<a href="#6.8.6.4">6.8.6.4</a>).
20711 <li> Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
20712 <li> After the actions associated with each formatted input/output function conversion
20713 specifier (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
20714 <li> Immediately before and immediately after each call to a comparison function, and
20715 also between any call to a comparison function and any movement of the objects
20716 passed as arguments to that call (<a href="#7.20.5">7.20.5</a>).
20720 <h2><a name="D" href="#D">Annex D</a></h2>
20724 Universal character names for identifiers</pre>
20725 This clause lists the hexadecimal code values that are valid in universal character names
20728 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
20729 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
20731 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
20733 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F</pre>
20734 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
20736 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
20737 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
20738 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
20739 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC</pre>
20740 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
20742 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9</pre>
20743 Armenian: 0531-0556, 0561-0587
20744 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
20747 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
20749 06D0-06DC, 06E5-06E8, 06EA-06ED</pre>
20750 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
20751 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
20753 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
20754 09DC-09DD, 09DF-09E3, 09F0-09F1</pre>
20755 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
20757 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
20758 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74</pre>
20759 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
20761 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
20762 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0</pre>
20763 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
20766 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
20767 0B5C-0B5D, 0B5F-0B61</pre>
20768 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
20770 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
20771 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD</pre>
20772 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
20774 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61</pre>
20775 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
20777 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
20779 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
20781 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61</pre>
20782 Thai: 0E01-0E3A, 0E40-0E5B
20783 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
20785 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
20786 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
20787 0EC8-0ECD, 0EDC-0EDD</pre>
20788 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
20790 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
20791 0FB1-0FB7, 0FB9</pre>
20792 Georgian: 10A0-10C5, 10D0-10F6
20793 Hiragana: 3041-3093, 309B-309C
20794 Katakana: 30A1-30F6, 30FB-30FC
20795 Bopomofo: 3105-312C
20796 CJK Unified Ideographs: 4E00-9FA5
20798 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
20800 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
20801 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33</pre>
20802 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
20805 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
20806 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
20807 2133-2138, 2160-2182, 3005-3007, 3021-3029</pre>
20809 <h2><a name="E" href="#E">Annex E</a></h2>
20813 <h6> Implementation limits</h6></pre>
20814 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
20815 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
20816 with the same sign. The values shall all be constant expressions suitable for use in #if
20817 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
20821 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
20822 #define CHAR_MIN 0 or SCHAR_MIN
20823 #define INT_MAX +32767
20824 #define INT_MIN -32767
20825 #define LONG_MAX +2147483647
20826 #define LONG_MIN -2147483647
20827 #define LLONG_MAX +9223372036854775807
20828 #define LLONG_MIN -9223372036854775807
20829 #define MB_LEN_MAX 1
20830 #define SCHAR_MAX +127
20831 #define SCHAR_MIN -127
20832 #define SHRT_MAX +32767
20833 #define SHRT_MIN -32767
20834 #define UCHAR_MAX 255
20835 #define USHRT_MAX 65535
20836 #define UINT_MAX 65535
20837 #define ULONG_MAX 4294967295
20838 #define ULLONG_MAX 18446744073709551615</pre>
20839 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
20840 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
20841 directives; all floating values shall be constant expressions. The components are
20842 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
20844 The values given in the following list shall be replaced by implementation-defined
20848 #define FLT_EVAL_METHOD
20849 #define FLT_ROUNDS</pre>
20850 The values given in the following list shall be replaced by implementation-defined
20851 constant expressions that are greater or equal in magnitude (absolute value) to those
20852 shown, with the same sign:
20857 #define DBL_MANT_DIG
20858 #define DBL_MAX_10_EXP +37
20859 #define DBL_MAX_EXP
20860 #define DBL_MIN_10_EXP -37
20861 #define DBL_MIN_EXP
20862 #define DECIMAL_DIG 10
20864 #define FLT_MANT_DIG
20865 #define FLT_MAX_10_EXP +37
20866 #define FLT_MAX_EXP
20867 #define FLT_MIN_10_EXP -37
20868 #define FLT_MIN_EXP
20869 #define FLT_RADIX 2
20870 #define LDBL_DIG 10
20871 #define LDBL_MANT_DIG
20872 #define LDBL_MAX_10_EXP +37
20873 #define LDBL_MAX_EXP
20874 #define LDBL_MIN_10_EXP -37
20875 #define LDBL_MIN_EXP</pre>
20876 The values given in the following list shall be replaced by implementation-defined
20877 constant expressions with values that are greater than or equal to those shown:
20880 #define DBL_MAX 1E+37
20881 #define FLT_MAX 1E+37
20882 #define LDBL_MAX 1E+37</pre>
20883 The values given in the following list shall be replaced by implementation-defined
20884 constant expressions with (positive) values that are less than or equal to those shown:
20887 #define DBL_EPSILON 1E-9
20888 #define DBL_MIN 1E-37
20889 #define FLT_EPSILON 1E-5
20890 #define FLT_MIN 1E-37
20891 #define LDBL_EPSILON 1E-9
20892 #define LDBL_MIN 1E-37</pre>
20894 <h2><a name="F" href="#F">Annex F</a></h2>
20897 IEC 60559 floating-point arithmetic</pre>
20899 <h3><a name="F.1" href="#F.1">F.1 Introduction</a></h3>
20901 This annex specifies C language support for the IEC 60559 floating-point standard. The
20902 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
20903 microprocessor systems, second edition (IEC 60559:1989), previously designated
20904 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
20905 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
20906 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
20907 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
20908 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
20909 defines __STDC_IEC_559__ shall conform to the specifications in this annex. Where
20910 a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
20911 behavior is adopted by reference, unless stated otherwise.
20913 <h3><a name="F.2" href="#F.2">F.2 Types</a></h3>
20915 The C floating types match the IEC 60559 formats as follows:
20917 <li> The float type matches the IEC 60559 single format.
20918 <li> The double type matches the IEC 60559 double format.
20919 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note307"><b>307)</b></a></sup> else a
20920 non-IEC 60559 extended format, else the IEC 60559 double format.
20922 Any non-IEC 60559 extended format used for the long double type shall have more
20923 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note308"><b>308)</b></a></sup>
20924 <h6> Recommended practice</h6>
20926 The long double type should match an IEC 60559 extended format.
20934 <p><small><a name="note307" href="#note307">307)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
20935 and quadruple 128-bit IEC 60559 formats.
20937 <p><small><a name="note308" href="#note308">308)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
20941 <h4><a name="F.2.1" href="#F.2.1">F.2.1 Infinities, signed zeros, and NaNs</a></h4>
20943 This specification does not define the behavior of signaling NaNs.<sup><a href="#note309"><b>309)</b></a></sup> It generally uses
20944 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
20945 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
20948 <p><small><a name="note309" href="#note309">309)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
20949 sufficient for closure of the arithmetic.
20952 <h3><a name="F.3" href="#F.3">F.3 Operators and functions</a></h3>
20954 C operators and functions provide IEC 60559 required and recommended facilities as
20957 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
20959 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
20960 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
20961 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
20962 with additional information.
20963 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
20964 floating-point number to an integer value (in the same precision). The nearbyint
20965 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
20966 Appendix to ANSI/IEEE 854.
20967 <li> The conversions for floating types provide the IEC 60559 conversions between
20968 floating-point precisions.
20969 <li> The conversions from integer to floating types provide the IEC 60559 conversions
20970 from integer to floating point.
20971 <li> The conversions from floating to integer types provide IEC 60559-like conversions
20972 but always round toward zero.
20973 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
20974 conversions, which honor the directed rounding mode, from floating point to the
20975 long int and long long int integer formats. The lrint and llrint
20976 functions can be used to implement IEC 60559 conversions from floating to other
20978 <li> The translation time conversion of floating constants and the strtod, strtof,
20979 strtold, fprintf, fscanf, and related library functions in <a href="#7.20"><stdlib.h></a>,
20980 <a href="#7.19"><stdio.h></a>, and <a href="#7.24"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
20981 strtold function in <a href="#7.20"><stdlib.h></a> provides the conv function recommended in the
20982 Appendix to ANSI/IEEE 854.
20985 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
20986 identifies a need for additional comparison predicates to facilitate writing code that
20987 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
20988 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
20989 supplement the language operators to address this need. The islessgreater and
20990 isunordered macros provide respectively a quiet version of the <> predicate and
20991 the unordered predicate recommended in the Appendix to IEC 60559.
20992 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
20993 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
20994 exception status flags. The fegetexceptflag and fesetexceptflag
20995 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
20996 one time. These functions are used in conjunction with the type fexcept_t and the
20997 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
20998 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
20999 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
21000 to select among the IEC 60559 directed rounding modes represented by the rounding
21001 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
21002 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
21003 IEC 60559 directed rounding modes.
21004 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
21005 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
21006 the IEC 60559 status flags and control modes.
21007 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
21008 recommended in the Appendix to IEC 60559.
21009 <li> The unary minus (-) operator provides the minus (-) operation recommended in the
21010 Appendix to IEC 60559.
21011 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
21012 recommended in the Appendix to IEC 60559.
21013 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
21014 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
21015 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
21016 function recommended in the Appendix to IEC 60559 (but with a minor change to
21017 better handle signed zeros).
21018 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
21019 the Appendix to IEC 60559.
21020 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
21021 Appendix to IEC 60559.
21023 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
21024 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
21025 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
21026 function recommended in the Appendix to IEC 60559 (except that the classification
21027 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
21030 <h3><a name="F.4" href="#F.4">F.4 Floating to integer conversion</a></h3>
21032 If the floating value is infinite or NaN or if the integral part of the floating value exceeds
21033 the range of the integer type, then the ''invalid'' floating-point exception is raised and the
21034 resulting value is unspecified. Whether conversion of non-integer floating values whose
21035 integral part is within the range of the integer type raises the ''inexact'' floating-point
21036 exception is unspecified.<sup><a href="#note310"><b>310)</b></a></sup>
21039 <p><small><a name="note310" href="#note310">310)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
21040 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
21041 cases where it matters, library functions can be used to effect such conversions with or without raising
21042 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
21043 <a href="#7.12"><math.h></a>.
21046 <h3><a name="F.5" href="#F.5">F.5 Binary-decimal conversion</a></h3>
21048 Conversion from the widest supported IEC 60559 format to decimal with
21049 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note311"><b>311)</b></a></sup>
21051 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
21052 particular, conversion between any supported IEC 60559 format and decimal with
21053 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
21054 rounding mode), which assures that conversion from the widest supported IEC 60559
21055 format to decimal with DECIMAL_DIG digits and back is the identity function.
21057 Functions such as strtod that convert character sequences to floating types honor the
21058 rounding direction. Hence, if the rounding direction might be upward or downward, the
21059 implementation cannot convert a minus-signed sequence by negating the converted
21068 <p><small><a name="note311" href="#note311">311)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
21069 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
21070 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
21071 DBL_DIG are 18 and 15, respectively, for these formats.)
21074 <h3><a name="F.6" href="#F.6">F.6 Contracted expressions</a></h3>
21076 A contracted expression treats infinities, NaNs, signed zeros, subnormals, and the
21077 rounding directions in a manner consistent with the basic arithmetic operations covered
21079 <h6> Recommended practice</h6>
21081 A contracted expression should raise floating-point exceptions in a manner generally
21082 consistent with the basic arithmetic operations. A contracted expression should deliver
21083 the same value as its uncontracted counterpart, else should be correctly rounded (once).
21085 <h3><a name="F.7" href="#F.7">F.7 Floating-point environment</a></h3>
21087 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
21088 point exception status flags and directed-rounding control modes. It includes also
21089 IEC 60559 dynamic rounding precision and trap enablement modes, if the
21090 implementation supports them.<sup><a href="#note312"><b>312)</b></a></sup>
21093 <p><small><a name="note312" href="#note312">312)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
21096 <h4><a name="F.7.1" href="#F.7.1">F.7.1 Environment management</a></h4>
21098 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
21099 status flags, and that rounding control modes can be set explicitly to affect result values of
21100 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
21101 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
21102 which respect sequence points.<sup><a href="#note313"><b>313)</b></a></sup>
21105 <p><small><a name="note313" href="#note313">313)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
21106 point control modes will be the default ones and the floating-point status flags will not be tested,
21107 which allows certain optimizations (see <a href="#F.8">F.8</a>).
21110 <h4><a name="F.7.2" href="#F.7.2">F.7.2 Translation</a></h4>
21112 During translation the IEC 60559 default modes are in effect:
21114 <li> The rounding direction mode is rounding to nearest.
21115 <li> The rounding precision mode (if supported) is set so that results are not shortened.
21116 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21118 <h6> Recommended practice</h6>
21120 The implementation should produce a diagnostic message for each translation-time
21126 floating-point exception, other than ''inexact'';<sup><a href="#note314"><b>314)</b></a></sup> the implementation should then
21127 proceed with the translation of the program.
21130 <p><small><a name="note314" href="#note314">314)</a> As floating constants are converted to appropriate internal representations at translation time, their
21131 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
21132 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
21133 strtod, provide execution-time conversion of numeric strings.
21136 <h4><a name="F.7.3" href="#F.7.3">F.7.3 Execution</a></h4>
21138 At program startup the floating-point environment is initialized as prescribed by
21141 <li> All floating-point exception status flags are cleared.
21142 <li> The rounding direction mode is rounding to nearest.
21143 <li> The dynamic rounding precision mode (if supported) is set so that results are not
21145 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21148 <h4><a name="F.7.4" href="#F.7.4">F.7.4 Constant expressions</a></h4>
21150 An arithmetic constant expression of floating type, other than one in an initializer for an
21151 object that has static storage duration, is evaluated (as if) during execution; thus, it is
21152 affected by any operative floating-point control modes and raises floating-point
21153 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
21154 is ''on'').<sup><a href="#note315"><b>315)</b></a></sup>
21159 #include <a href="#7.6"><fenv.h></a>
21160 #pragma STDC FENV_ACCESS ON
21163 float w[] = { 0.0/0.0 }; // raises an exception
21164 static float x = 0.0/0.0; // does not raise an exception
21165 float y = 0.0/0.0; // raises an exception
21166 double z = 0.0/0.0; // raises an exception
21169 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
21170 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
21178 <p><small><a name="note315" href="#note315">315)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
21179 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
21180 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
21181 efficiency of translation-time evaluation through static initialization, such as
21184 const static double one_third = 1.0/3.0;</pre>
21187 <h4><a name="F.7.5" href="#F.7.5">F.7.5 Initialization</a></h4>
21189 All computation for automatic initialization is done (as if) at execution time; thus, it is
21190 affected by any operative modes and raises floating-point exceptions as required by
21191 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
21192 for initialization of objects that have static storage duration is done (as if) at translation
21198 #include <a href="#7.6"><fenv.h></a>
21199 #pragma STDC FENV_ACCESS ON
21202 float u[] = { 1.1e75 }; // raises exceptions
21203 static float v = 1.1e75; // does not raise exceptions
21204 float w = 1.1e75; // raises exceptions
21205 double x = 1.1e75; // may raise exceptions
21206 float y = 1.1e75f; // may raise exceptions
21207 long double z = 1.1e75; // does not raise exceptions
21210 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
21211 done at translation time. The automatic initialization of u and w require an execution-time conversion to
21212 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
21213 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
21214 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note316"><b>316)</b></a></sup> The
21215 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
21216 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
21217 their internal representations occur at translation time in all cases.
21225 <p><small><a name="note316" href="#note316">316)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
21226 For example, the automatic initialization
21229 double_t x = 1.1e75;</pre>
21230 could be done at translation time, regardless of the expression evaluation method.
21233 <h4><a name="F.7.6" href="#F.7.6">F.7.6 Changing the environment</a></h4>
21235 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
21236 change floating-point status flags and control modes just as indicated by their
21237 specifications (including conformance to IEC 60559). They do not change flags or modes
21238 (so as to be detectable by the user) in any other cases.
21240 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
21241 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
21242 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
21243 before ''inexact''.
21245 <h3><a name="F.8" href="#F.8">F.8 Optimization</a></h3>
21247 This section identifies code transformations that might subvert IEC 60559-specified
21248 behavior, and others that do not.
21250 <h4><a name="F.8.1" href="#F.8.1">F.8.1 Global transformations</a></h4>
21252 Floating-point arithmetic operations and external function calls may entail side effects
21253 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
21254 ''on''. The flags and modes in the floating-point environment may be regarded as global
21255 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
21258 Concern about side effects may inhibit code motion and removal of seemingly useless
21259 code. For example, in
21261 #include <a href="#7.6"><fenv.h></a>
21262 #pragma STDC FENV_ACCESS ON
21266 for (i = 0; i < n; i++) x + 1;
21269 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
21270 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
21271 course these optimizations are valid if the implementation can rule out the nettlesome
21274 This specification does not require support for trap handlers that maintain information
21275 about the order or count of floating-point exceptions. Therefore, between function calls,
21276 floating-point exceptions need not be precise: the actual order and number of occurrences
21277 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
21278 the preceding loop could be treated as
21281 if (0 < n) x + 1;</pre>
21283 <h4><a name="F.8.2" href="#F.8.2">F.8.2 Expression transformations</a></h4>
21285 x / 2 <-> x * 0.5 Although similar transformations involving inexact
21287 constants generally do not yield numerically equivalent
21288 expressions, if the constants are exact then such
21289 transformations can be made on IEC 60559 machines
21290 and others that round perfectly.</pre>
21291 1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
21293 (on IEC 60559 machines, among others).<sup><a href="#note317"><b>317)</b></a></sup></pre>
21294 x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
21296 can be zero, infinite, or NaN.</pre>
21297 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
21299 are equivalent (on IEC 60559 machines, among others).</pre>
21300 x - y <-> -(y - x) The expressions x - y and -(y - x) are not
21302 equivalent because 1 - 1 is +0 but -(1 - 1) is -0 (in the
21303 default rounding direction).<sup><a href="#note318"><b>318)</b></a></sup></pre>
21304 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
21306 x is a NaN or infinite.</pre>
21307 0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
21309 x is a NaN, infinite, or -0.</pre>
21310 x + 0->x The expressions x + 0 and x are not equivalent if x is
21312 -0, because (-0) + (+0) yields +0 (in the default
21313 rounding direction), not -0.</pre>
21314 x - 0->x (+0) - (+0) yields -0 when rounding is downward
21316 (toward -(inf)), but +0 otherwise, and (-0) - (+0) always
21317 yields -0; so, if the state of the FENV_ACCESS pragma
21318 is ''off'', promising default rounding, then the
21319 implementation can replace x - 0 by x, even if x</pre>
21324 might be zero.</pre>
21325 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x
21327 is +0, because -(+0) yields -0, but 0 - (+0) yields +0
21328 (unless rounding is downward).</pre>
21331 <p><small><a name="note317" href="#note317">317)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
21332 other transformations that remove arithmetic operators.
21334 <p><small><a name="note318" href="#note318">318)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
21338 1/(1/ (+-) (inf)) is (+-) (inf)</pre>
21342 conj(csqrt(z)) is csqrt(conj(z)),</pre>
21346 <h4><a name="F.8.3" href="#F.8.3">F.8.3 Relational operators</a></h4>
21348 x != x -> false The statement x != x is true if x is a NaN.
21349 x == x -> true The statement x == x is false if x is a NaN.
21350 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically
21352 equal, these expressions are not equivalent because of
21353 side effects when x or y is a NaN and the state of the
21354 FENV_ACCESS pragma is ''on''. This transformation,
21355 which would be desirable if extra code were required to
21356 cause the ''invalid'' floating-point exception for
21357 unordered cases, could be performed provided the state
21358 of the FENV_ACCESS pragma is ''off''.</pre>
21359 The sense of relational operators shall be maintained. This includes handling unordered
21360 cases as expressed by the source code.
21364 // calls g and raises ''invalid'' if a and b are unordered
21369 is not equivalent to
21371 // calls f and raises ''invalid'' if a and b are unordered
21378 // calls f without raising ''invalid'' if a and b are unordered
21379 if (isgreaterequal(a,b))
21383 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
21386 // calls g without raising ''invalid'' if a and b are unordered
21391 but is equivalent to
21399 <h4><a name="F.8.4" href="#F.8.4">F.8.4 Constant arithmetic</a></h4>
21401 The implementation shall honor floating-point exceptions raised by execution-time
21402 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.7.4">F.7.4</a>
21403 and <a href="#F.7.5">F.7.5</a>.) An operation on constants that raises no floating-point exception can be
21404 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
21405 further check is required to assure that changing the rounding direction to downward does
21406 not alter the sign of the result,<sup><a href="#note319"><b>319)</b></a></sup> and implementations that support dynamic rounding
21407 precision modes shall assure further that the result of the operation raises no floating-
21408 point exception when converted to the semantic type of the operation.
21411 <p><small><a name="note319" href="#note319">319)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
21414 <h3><a name="F.9" href="#F.9">F.9 Mathematics <math.h></a></h3>
21416 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
21417 for IEC 60559 implementations.
21419 The Standard C macro HUGE_VAL and its float and long double analogs,
21420 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
21423 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
21424 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
21425 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
21426 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
21427 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
21429 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
21432 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
21433 subsequent subclauses of this annex.
21435 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
21436 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
21440 whose magnitude is too large.
21442 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
21443 subnormal or zero) and suffers loss of accuracy.<sup><a href="#note320"><b>320)</b></a></sup>
21445 Whether or when library functions raise the ''inexact'' floating-point exception is
21446 unspecified, unless explicitly specified otherwise.
21448 Whether or when library functions raise an undeserved ''underflow'' floating-point
21449 exception is unspecified.<sup><a href="#note321"><b>321)</b></a></sup> Otherwise, as implied by <a href="#F.7.6">F.7.6</a>, the <a href="#7.12"><math.h></a> functions do
21450 not raise spurious floating-point exceptions (detectable by the user), other than the
21451 ''inexact'' floating-point exception.
21453 Whether the functions honor the rounding direction mode is implementation-defined,
21454 unless explicitly specified otherwise.
21456 Functions with a NaN argument return a NaN result and raise no floating-point exception,
21457 except where stated otherwise.
21459 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
21460 For families of functions, the specifications apply to all of the functions even though only
21461 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
21462 occurs in both an argument and the result, the result has the same sign as the argument.
21463 <h6> Recommended practice</h6>
21465 If a function with one or more NaN arguments returns a NaN result, the result should be
21466 the same as one of the NaN arguments (after possible type conversion), except perhaps
21470 <p><small><a name="note320" href="#note320">320)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
21471 when the floating-point exception is raised.
21473 <p><small><a name="note321" href="#note321">321)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
21474 avoiding them would be too costly.
21477 <h4><a name="F.9.1" href="#F.9.1">F.9.1 Trigonometric functions</a></h4>
21479 <h5><a name="F.9.1.1" href="#F.9.1.1">F.9.1.1 The acos functions</a></h5>
21482 <li> acos(1) returns +0.
21483 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
21492 <h5><a name="F.9.1.2" href="#F.9.1.2">F.9.1.2 The asin functions</a></h5>
21495 <li> asin((+-)0) returns (+-)0.
21496 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
21500 <h5><a name="F.9.1.3" href="#F.9.1.3">F.9.1.3 The atan functions</a></h5>
21503 <li> atan((+-)0) returns (+-)0.
21504 <li> atan((+-)(inf)) returns (+-)pi /2.
21507 <h5><a name="F.9.1.4" href="#F.9.1.4">F.9.1.4 The atan2 functions</a></h5>
21510 <li> atan2((+-)0, -0) returns (+-)pi .<sup><a href="#note322"><b>322)</b></a></sup>
21511 <li> atan2((+-)0, +0) returns (+-)0.
21512 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
21513 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
21514 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
21515 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
21516 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
21517 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
21518 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
21519 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
21520 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
21524 <p><small><a name="note322" href="#note322">322)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
21525 the ''divide-by-zero'' floating-point exception.
21528 <h5><a name="F.9.1.5" href="#F.9.1.5">F.9.1.5 The cos functions</a></h5>
21531 <li> cos((+-)0) returns 1.
21532 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21535 <h5><a name="F.9.1.6" href="#F.9.1.6">F.9.1.6 The sin functions</a></h5>
21538 <li> sin((+-)0) returns (+-)0.
21539 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21547 <h5><a name="F.9.1.7" href="#F.9.1.7">F.9.1.7 The tan functions</a></h5>
21550 <li> tan((+-)0) returns (+-)0.
21551 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21554 <h4><a name="F.9.2" href="#F.9.2">F.9.2 Hyperbolic functions</a></h4>
21556 <h5><a name="F.9.2.1" href="#F.9.2.1">F.9.2.1 The acosh functions</a></h5>
21559 <li> acosh(1) returns +0.
21560 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
21561 <li> acosh(+(inf)) returns +(inf).
21564 <h5><a name="F.9.2.2" href="#F.9.2.2">F.9.2.2 The asinh functions</a></h5>
21567 <li> asinh((+-)0) returns (+-)0.
21568 <li> asinh((+-)(inf)) returns (+-)(inf).
21571 <h5><a name="F.9.2.3" href="#F.9.2.3">F.9.2.3 The atanh functions</a></h5>
21574 <li> atanh((+-)0) returns (+-)0.
21575 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21576 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
21580 <h5><a name="F.9.2.4" href="#F.9.2.4">F.9.2.4 The cosh functions</a></h5>
21583 <li> cosh((+-)0) returns 1.
21584 <li> cosh((+-)(inf)) returns +(inf).
21587 <h5><a name="F.9.2.5" href="#F.9.2.5">F.9.2.5 The sinh functions</a></h5>
21590 <li> sinh((+-)0) returns (+-)0.
21591 <li> sinh((+-)(inf)) returns (+-)(inf).
21594 <h5><a name="F.9.2.6" href="#F.9.2.6">F.9.2.6 The tanh functions</a></h5>
21597 <li> tanh((+-)0) returns (+-)0.
21598 <li> tanh((+-)(inf)) returns (+-)1.
21602 <h4><a name="F.9.3" href="#F.9.3">F.9.3 Exponential and logarithmic functions</a></h4>
21604 <h5><a name="F.9.3.1" href="#F.9.3.1">F.9.3.1 The exp functions</a></h5>
21607 <li> exp((+-)0) returns 1.
21608 <li> exp(-(inf)) returns +0.
21609 <li> exp(+(inf)) returns +(inf).
21612 <h5><a name="F.9.3.2" href="#F.9.3.2">F.9.3.2 The exp2 functions</a></h5>
21615 <li> exp2((+-)0) returns 1.
21616 <li> exp2(-(inf)) returns +0.
21617 <li> exp2(+(inf)) returns +(inf).
21620 <h5><a name="F.9.3.3" href="#F.9.3.3">F.9.3.3 The expm1 functions</a></h5>
21623 <li> expm1((+-)0) returns (+-)0.
21624 <li> expm1(-(inf)) returns -1.
21625 <li> expm1(+(inf)) returns +(inf).
21628 <h5><a name="F.9.3.4" href="#F.9.3.4">F.9.3.4 The frexp functions</a></h5>
21631 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
21632 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
21634 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
21635 (and returns a NaN).
21638 frexp raises no floating-point exceptions.
21640 On a binary system, the body of the frexp function might be
21643 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
21644 return scalbn(value, -(*exp));
21647 <h5><a name="F.9.3.5" href="#F.9.3.5">F.9.3.5 The ilogb functions</a></h5>
21649 If the correct result is outside the range of the return type, the numeric result is
21650 unspecified and the ''invalid'' floating-point exception is raised.
21653 <h5><a name="F.9.3.6" href="#F.9.3.6">F.9.3.6 The ldexp functions</a></h5>
21655 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
21657 <h5><a name="F.9.3.7" href="#F.9.3.7">F.9.3.7 The log functions</a></h5>
21660 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21661 <li> log(1) returns +0.
21662 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21663 <li> log(+(inf)) returns +(inf).
21666 <h5><a name="F.9.3.8" href="#F.9.3.8">F.9.3.8 The log10 functions</a></h5>
21669 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21670 <li> log10(1) returns +0.
21671 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21672 <li> log10(+(inf)) returns +(inf).
21675 <h5><a name="F.9.3.9" href="#F.9.3.9">F.9.3.9 The log1p functions</a></h5>
21678 <li> log1p((+-)0) returns (+-)0.
21679 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21680 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
21682 <li> log1p(+(inf)) returns +(inf).
21685 <h5><a name="F.9.3.10" href="#F.9.3.10">F.9.3.10 The log2 functions</a></h5>
21688 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21689 <li> log2(1) returns +0.
21690 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21691 <li> log2(+(inf)) returns +(inf).
21694 <h5><a name="F.9.3.11" href="#F.9.3.11">F.9.3.11 The logb functions</a></h5>
21697 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21698 <li> logb((+-)(inf)) returns +(inf).
21702 <h5><a name="F.9.3.12" href="#F.9.3.12">F.9.3.12 The modf functions</a></h5>
21705 <li> modf((+-)x, iptr) returns a result with the same sign as x.
21706 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
21707 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
21711 modf behaves as though implemented by
21713 #include <a href="#7.12"><math.h></a>
21714 #include <a href="#7.6"><fenv.h></a>
21715 #pragma STDC FENV_ACCESS ON
21716 double modf(double value, double *iptr)
21718 int save_round = fegetround();
21719 fesetround(FE_TOWARDZERO);
21720 *iptr = nearbyint(value);
21721 fesetround(save_round);
21723 isinf(value) ? 0.0 :
21724 value - (*iptr), value);
21727 <h5><a name="F.9.3.13" href="#F.9.3.13">F.9.3.13 The scalbn and scalbln functions</a></h5>
21730 <li> scalbn((+-)0, n) returns (+-)0.
21731 <li> scalbn(x, 0) returns x.
21732 <li> scalbn((+-)(inf), n) returns (+-)(inf).
21735 <h4><a name="F.9.4" href="#F.9.4">F.9.4 Power and absolute value functions</a></h4>
21737 <h5><a name="F.9.4.1" href="#F.9.4.1">F.9.4.1 The cbrt functions</a></h5>
21740 <li> cbrt((+-)0) returns (+-)0.
21741 <li> cbrt((+-)(inf)) returns (+-)(inf).
21744 <h5><a name="F.9.4.2" href="#F.9.4.2">F.9.4.2 The fabs functions</a></h5>
21747 <li> fabs((+-)0) returns +0.
21748 <li> fabs((+-)(inf)) returns +(inf).
21752 <h5><a name="F.9.4.3" href="#F.9.4.3">F.9.4.3 The hypot functions</a></h5>
21755 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
21756 <li> hypot(x, (+-)0) is equivalent to fabs(x).
21757 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
21760 <h5><a name="F.9.4.4" href="#F.9.4.4">F.9.4.4 The pow functions</a></h5>
21763 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
21764 for y an odd integer < 0.
21765 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
21766 for y < 0 and not an odd integer.
21767 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
21768 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
21769 <li> pow(-1, (+-)(inf)) returns 1.
21770 <li> pow(+1, y) returns 1 for any y, even a NaN.
21771 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
21772 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
21773 finite x < 0 and finite non-integer y.
21774 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
21775 <li> pow(x, -(inf)) returns +0 for | x | > 1.
21776 <li> pow(x, +(inf)) returns +0 for | x | < 1.
21777 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
21778 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
21779 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
21780 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
21781 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
21782 <li> pow(+(inf), y) returns +0 for y < 0.
21783 <li> pow(+(inf), y) returns +(inf) for y > 0.
21787 <h5><a name="F.9.4.5" href="#F.9.4.5">F.9.4.5 The sqrt functions</a></h5>
21789 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
21791 <h4><a name="F.9.5" href="#F.9.5">F.9.5 Error and gamma functions</a></h4>
21793 <h5><a name="F.9.5.1" href="#F.9.5.1">F.9.5.1 The erf functions</a></h5>
21796 <li> erf((+-)0) returns (+-)0.
21797 <li> erf((+-)(inf)) returns (+-)1.
21800 <h5><a name="F.9.5.2" href="#F.9.5.2">F.9.5.2 The erfc functions</a></h5>
21803 <li> erfc(-(inf)) returns 2.
21804 <li> erfc(+(inf)) returns +0.
21807 <h5><a name="F.9.5.3" href="#F.9.5.3">F.9.5.3 The lgamma functions</a></h5>
21810 <li> lgamma(1) returns +0.
21811 <li> lgamma(2) returns +0.
21812 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
21813 x a negative integer or zero.
21814 <li> lgamma(-(inf)) returns +(inf).
21815 <li> lgamma(+(inf)) returns +(inf).
21818 <h5><a name="F.9.5.4" href="#F.9.5.4">F.9.5.4 The tgamma functions</a></h5>
21821 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21822 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
21824 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21825 <li> tgamma(+(inf)) returns +(inf).
21828 <h4><a name="F.9.6" href="#F.9.6">F.9.6 Nearest integer functions</a></h4>
21830 <h5><a name="F.9.6.1" href="#F.9.6.1">F.9.6.1 The ceil functions</a></h5>
21833 <li> ceil((+-)0) returns (+-)0.
21834 <li> ceil((+-)(inf)) returns (+-)(inf).
21837 The double version of ceil behaves as though implemented by
21840 #include <a href="#7.12"><math.h></a>
21841 #include <a href="#7.6"><fenv.h></a>
21842 #pragma STDC FENV_ACCESS ON
21843 double ceil(double x)
21846 int save_round = fegetround();
21847 fesetround(FE_UPWARD);
21848 result = rint(x); // or nearbyint instead of rint
21849 fesetround(save_round);
21853 <h5><a name="F.9.6.2" href="#F.9.6.2">F.9.6.2 The floor functions</a></h5>
21856 <li> floor((+-)0) returns (+-)0.
21857 <li> floor((+-)(inf)) returns (+-)(inf).
21860 See the sample implementation for ceil in <a href="#F.9.6.1">F.9.6.1</a>.
21862 <h5><a name="F.9.6.3" href="#F.9.6.3">F.9.6.3 The nearbyint functions</a></h5>
21864 The nearbyint functions use IEC 60559 rounding according to the current rounding
21865 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
21866 value from the argument.
21868 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
21869 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
21872 <h5><a name="F.9.6.4" href="#F.9.6.4">F.9.6.4 The rint functions</a></h5>
21874 The rint functions differ from the nearbyint functions only in that they do raise the
21875 ''inexact'' floating-point exception if the result differs in value from the argument.
21877 <h5><a name="F.9.6.5" href="#F.9.6.5">F.9.6.5 The lrint and llrint functions</a></h5>
21879 The lrint and llrint functions provide floating-to-integer conversion as prescribed
21880 by IEC 60559. They round according to the current rounding direction. If the rounded
21881 value is outside the range of the return type, the numeric result is unspecified and the
21882 ''invalid'' floating-point exception is raised. When they raise no other floating-point
21883 exception and the result differs from the argument, they raise the ''inexact'' floating-point
21887 <h5><a name="F.9.6.6" href="#F.9.6.6">F.9.6.6 The round functions</a></h5>
21890 <li> round((+-)0) returns (+-)0.
21891 <li> round((+-)(inf)) returns (+-)(inf).
21894 The double version of round behaves as though implemented by
21896 #include <a href="#7.12"><math.h></a>
21897 #include <a href="#7.6"><fenv.h></a>
21898 #pragma STDC FENV_ACCESS ON
21899 double round(double x)
21903 feholdexcept(&save_env);
21905 if (fetestexcept(FE_INEXACT)) {
21906 fesetround(FE_TOWARDZERO);
21907 result = rint(copysign(0.5 + fabs(x), x));
21909 feupdateenv(&save_env);
21912 The round functions may, but are not required to, raise the ''inexact'' floating-point
21913 exception for non-integer numeric arguments, as this implementation does.
21915 <h5><a name="F.9.6.7" href="#F.9.6.7">F.9.6.7 The lround and llround functions</a></h5>
21917 The lround and llround functions differ from the lrint and llrint functions
21918 with the default rounding direction just in that the lround and llround functions
21919 round halfway cases away from zero and need not raise the ''inexact'' floating-point
21920 exception for non-integer arguments that round to within the range of the return type.
21922 <h5><a name="F.9.6.8" href="#F.9.6.8">F.9.6.8 The trunc functions</a></h5>
21924 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
21925 rounding direction).
21927 <li> trunc((+-)0) returns (+-)0.
21928 <li> trunc((+-)(inf)) returns (+-)(inf).
21932 <h4><a name="F.9.7" href="#F.9.7">F.9.7 Remainder functions</a></h4>
21934 <h5><a name="F.9.7.1" href="#F.9.7.1">F.9.7.1 The fmod functions</a></h5>
21937 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
21938 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
21939 infinite or y zero.
21940 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
21943 The double version of fmod behaves as though implemented by
21945 #include <a href="#7.12"><math.h></a>
21946 #include <a href="#7.6"><fenv.h></a>
21947 #pragma STDC FENV_ACCESS ON
21948 double fmod(double x, double y)
21951 result = remainder(fabs(x), (y = fabs(y)));
21952 if (signbit(result)) result += y;
21953 return copysign(result, x);
21956 <h5><a name="F.9.7.2" href="#F.9.7.2">F.9.7.2 The remainder functions</a></h5>
21958 The remainder functions are fully specified as a basic arithmetic operation in
21961 <h5><a name="F.9.7.3" href="#F.9.7.3">F.9.7.3 The remquo functions</a></h5>
21963 The remquo functions follow the specifications for the remainder functions. They
21964 have no further specifications special to IEC 60559 implementations.
21966 <h4><a name="F.9.8" href="#F.9.8">F.9.8 Manipulation functions</a></h4>
21968 <h5><a name="F.9.8.1" href="#F.9.8.1">F.9.8.1 The copysign functions</a></h5>
21970 copysign is specified in the Appendix to IEC 60559.
21972 <h5><a name="F.9.8.2" href="#F.9.8.2">F.9.8.2 The nan functions</a></h5>
21974 All IEC 60559 implementations support quiet NaNs, in all floating formats.
21977 <h5><a name="F.9.8.3" href="#F.9.8.3">F.9.8.3 The nextafter functions</a></h5>
21980 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
21981 for x finite and the function value infinite.
21982 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
21983 exceptions for the function value subnormal or zero and x != y.
21986 <h5><a name="F.9.8.4" href="#F.9.8.4">F.9.8.4 The nexttoward functions</a></h5>
21988 No additional requirements beyond those on nextafter.
21990 <h4><a name="F.9.9" href="#F.9.9">F.9.9 Maximum, minimum, and positive difference functions</a></h4>
21992 <h5><a name="F.9.9.1" href="#F.9.9.1">F.9.9.1 The fdim functions</a></h5>
21994 No additional requirements.
21996 <h5><a name="F.9.9.2" href="#F.9.9.2">F.9.9.2 The fmax functions</a></h5>
21998 If just one argument is a NaN, the fmax functions return the other argument (if both
21999 arguments are NaNs, the functions return a NaN).
22001 The body of the fmax function might be<sup><a href="#note323"><b>323)</b></a></sup>
22003 { return (isgreaterequal(x, y) ||
22004 isnan(y)) ? x : y; }</pre>
22007 <p><small><a name="note323" href="#note323">323)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
22008 return +0; however, implementation in software might be impractical.
22011 <h5><a name="F.9.9.3" href="#F.9.9.3">F.9.9.3 The fmin functions</a></h5>
22013 The fmin functions are analogous to the fmax functions (see <a href="#F.9.9.2">F.9.9.2</a>).
22015 <h4><a name="F.9.10" href="#F.9.10">F.9.10 Floating multiply-add</a></h4>
22017 <h5><a name="F.9.10.1" href="#F.9.10.1">F.9.10.1 The fma functions</a></h5>
22020 <li> fma(x, y, z) computes xy + z, correctly rounded once.
22021 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
22022 exception if one of x and y is infinite, the other is zero, and z is a NaN.
22023 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
22024 one of x and y is infinite, the other is zero, and z is not a NaN.
22025 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
22026 times y is an exact infinity and z is also an infinity but with the opposite sign.
22034 <h2><a name="G" href="#G">Annex G</a></h2>
22037 IEC 60559-compatible complex arithmetic</pre>
22039 <h3><a name="G.1" href="#G.1">G.1 Introduction</a></h3>
22041 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
22042 IEC 60559 real floating-point arithmetic. Although these specifications have been
22043 carefully designed, there is little existing practice to validate the design decisions.
22044 Therefore, these specifications are not normative, but should be viewed more as
22045 recommended practice. An implementation that defines
22046 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
22048 <h3><a name="G.2" href="#G.2">G.2 Types</a></h3>
22050 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
22051 used as a type specifier within declaration specifiers in the same way as _Complex is
22052 (thus, _Imaginary float is a valid type name).
22054 There are three imaginary types, designated as float _Imaginary, double
22055 _Imaginary, and long double _Imaginary. The imaginary types (along with
22056 the real floating and complex types) are floating types.
22058 For imaginary types, the corresponding real type is given by deleting the keyword
22059 _Imaginary from the type name.
22061 Each imaginary type has the same representation and alignment requirements as the
22062 corresponding real type. The value of an object of imaginary type is the value of the real
22063 representation times the imaginary unit.
22065 The imaginary type domain comprises the imaginary types.
22067 <h3><a name="G.3" href="#G.3">G.3 Conventions</a></h3>
22069 A complex or imaginary value with at least one infinite part is regarded as an infinity
22070 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
22071 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
22072 a zero if each of its parts is a zero.
22075 <h3><a name="G.4" href="#G.4">G.4 Conversions</a></h3>
22077 <h4><a name="G.4.1" href="#G.4.1">G.4.1 Imaginary types</a></h4>
22079 Conversions among imaginary types follow rules analogous to those for real floating
22082 <h4><a name="G.4.2" href="#G.4.2">G.4.2 Real and imaginary</a></h4>
22084 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note324"><b>324)</b></a></sup> the
22085 result is a positive zero.
22087 When a value of real type is converted to an imaginary type, the result is a positive
22091 <p><small><a name="note324" href="#note324">324)</a> See <a href="#6.3.1.2">6.3.1.2</a>.
22094 <h4><a name="G.4.3" href="#G.4.3">G.4.3 Imaginary and complex</a></h4>
22096 When a value of imaginary type is converted to a complex type, the real part of the
22097 complex result value is a positive zero and the imaginary part of the complex result value
22098 is determined by the conversion rules for the corresponding real types.
22100 When a value of complex type is converted to an imaginary type, the real part of the
22101 complex value is discarded and the value of the imaginary part is converted according to
22102 the conversion rules for the corresponding real types.
22104 <h3><a name="G.5" href="#G.5">G.5 Binary operators</a></h3>
22106 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
22107 operation with an imaginary operand.
22109 For most operand types, the value of the result of a binary operator with an imaginary or
22110 complex operand is completely determined, with reference to real arithmetic, by the usual
22111 mathematical formula. For some operand types, the usual mathematical formula is
22112 problematic because of its treatment of infinities and because of undue overflow or
22113 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
22114 not completely determined.
22121 <h4><a name="G.5.1" href="#G.5.1">G.5.1 Multiplicative operators</a></h4>
22124 If one operand has real type and the other operand has imaginary type, then the result has
22125 imaginary type. If both operands have imaginary type, then the result has real type. (If
22126 either operand has complex type, then the result has complex type.)
22128 If the operands are not both complex, then the result and floating-point exception
22129 behavior of the * operator is defined by the usual mathematical formula:
22131 * u iv u + iv</pre>
22134 x xu i(xv) (xu) + i(xv)</pre>
22137 iy i(yu) -yv (-yv) + i(yu)</pre>
22141 x + iy (xu) + i(yu) (-yv) + i(xv)</pre>
22142 If the second operand is not complex, then the result and floating-point exception
22143 behavior of the / operator is defined by the usual mathematical formula:
22148 x x/u i(-x/v)</pre>
22151 iy i(y/u) y/v</pre>
22155 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)</pre>
22156 The * and / operators satisfy the following infinity properties for all real, imaginary, and
22157 complex operands:<sup><a href="#note325"><b>325)</b></a></sup>
22159 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
22160 infinity, then the result of the * operator is an infinity;
22161 <li> if the first operand is an infinity and the second operand is a finite number, then the
22162 result of the / operator is an infinity;
22163 <li> if the first operand is a finite number and the second operand is an infinity, then the
22164 result of the / operator is a zero;
22170 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
22171 a zero, then the result of the / operator is an infinity.
22174 If both operands of the * operator are complex or if the second operand of the / operator
22175 is complex, the operator raises floating-point exceptions if appropriate for the calculation
22176 of the parts of the result, and may raise spurious floating-point exceptions.
22178 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
22179 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
22183 #include <a href="#7.12"><math.h></a>
22184 #include <a href="#7.3"><complex.h></a>
22185 /* Multiply z * w ... */
22186 double complex _Cmultd(double complex z, double complex w)
22188 #pragma STDC FP_CONTRACT OFF
22189 double a, b, c, d, ac, bd, ad, bc, x, y;
22190 a = creal(z); b = cimag(z);
22191 c = creal(w); d = cimag(w);
22192 ac = a * c; bd = b * d;
22193 ad = a * d; bc = b * c;
22194 x = ac - bd; y = ad + bc;
22195 if (isnan(x) && isnan(y)) {
22196 /* Recover infinities that computed as NaN+iNaN ... */
22198 if ( isinf(a) || isinf(b) ) { // z is infinite
22199 /* "Box" the infinity and change NaNs in the other factor to 0 */
22200 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22201 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22202 if (isnan(c)) c = copysign(0.0, c);
22203 if (isnan(d)) d = copysign(0.0, d);
22206 if ( isinf(c) || isinf(d) ) { // w is infinite
22207 /* "Box" the infinity and change NaNs in the other factor to 0 */
22208 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22209 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22210 if (isnan(a)) a = copysign(0.0, a);
22211 if (isnan(b)) b = copysign(0.0, b);
22214 if (!recalc && (isinf(ac) || isinf(bd) ||
22215 isinf(ad) || isinf(bc))) {
22216 /* Recover infinities from overflow by changing NaNs to 0 ... */
22217 if (isnan(a)) a = copysign(0.0, a);
22218 if (isnan(b)) b = copysign(0.0, b);
22219 if (isnan(c)) c = copysign(0.0, c);
22220 if (isnan(d)) d = copysign(0.0, d);
22224 x = INFINITY * ( a * c - b * d );
22225 y = INFINITY * ( a * d + b * c );
22230 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
22231 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
22234 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
22238 #include <a href="#7.12"><math.h></a>
22239 #include <a href="#7.3"><complex.h></a>
22240 /* Divide z / w ... */
22241 double complex _Cdivd(double complex z, double complex w)
22243 #pragma STDC FP_CONTRACT OFF
22244 double a, b, c, d, logbw, denom, x, y;
22246 a = creal(z); b = cimag(z);
22247 c = creal(w); d = cimag(w);
22248 logbw = logb(fmax(fabs(c), fabs(d)));
22249 if (isfinite(logbw)) {
22250 ilogbw = (int)logbw;
22251 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
22253 denom = c * c + d * d;
22254 x = scalbn((a * c + b * d) / denom, -ilogbw);
22255 y = scalbn((b * c - a * d) / denom, -ilogbw);
22256 /* Recover infinities and zeros that computed as NaN+iNaN; */
22257 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
22258 if (isnan(x) && isnan(y)) {
22259 if ((denom == 0.0) &&
22260 (!isnan(a) || !isnan(b))) {
22261 x = copysign(INFINITY, c) * a;
22262 y = copysign(INFINITY, c) * b;
22264 else if ((isinf(a) || isinf(b)) &&
22265 isfinite(c) && isfinite(d)) {
22266 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22267 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22268 x = INFINITY * ( a * c + b * d );
22269 y = INFINITY * ( b * c - a * d );
22271 else if (isinf(logbw) &&
22272 isfinite(a) && isfinite(b)) {
22273 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22274 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22275 x = 0.0 * ( a * c + b * d );
22276 y = 0.0 * ( b * c - a * d );
22281 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
22282 for multiplication. In the spirit of the multiplication example above, this code does not defend against
22283 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
22284 with division, provides better roundoff characteristics.
22288 <p><small><a name="note325" href="#note325">325)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
22289 (at least where the state for CX_LIMITED_RANGE is ''off'').
22292 <h4><a name="G.5.2" href="#G.5.2">G.5.2 Additive operators</a></h4>
22295 If both operands have imaginary type, then the result has imaginary type. (If one operand
22296 has real type and the other operand has imaginary type, or if either operand has complex
22297 type, then the result has complex type.)
22299 In all cases the result and floating-point exception behavior of a + or - operator is defined
22300 by the usual mathematical formula:
22302 + or - u iv u + iv</pre>
22305 x x(+-)u x (+-) iv (x (+-) u) (+-) iv</pre>
22308 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)</pre>
22311 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)</pre>
22313 <h3><a name="G.6" href="#G.6">G.6 Complex arithmetic <complex.h></a></h3>
22321 are defined, respectively, as _Imaginary and a constant expression of type const
22322 float _Imaginary with the value of the imaginary unit. The macro
22325 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
22326 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
22329 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
22330 particularly suited to IEC 60559 implementations. For families of functions, the
22331 specifications apply to all of the functions even though only the principal function is
22333 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
22334 and the result, the result has the same sign as the argument.
22336 The functions are continuous onto both sides of their branch cuts, taking into account the
22337 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. ???
22339 Since complex and imaginary values are composed of real values, each function may be
22340 regarded as computing real values from real values. Except as noted, the functions treat
22341 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
22342 manner consistent with the specifications for real functions in F.9.<sup><a href="#note326"><b>326)</b></a></sup>
22344 The functions cimag, conj, cproj, and creal are fully specified for all
22345 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
22348 Each of the functions cabs and carg is specified by a formula in terms of a real
22349 function (whose special cases are covered in <a href="#F">annex F</a>):
22352 cabs(x + iy) = hypot(x, y)
22353 carg(x + iy) = atan2(y, x)</pre>
22354 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
22355 a formula in terms of other complex functions (whose special cases are specified below):
22358 casin(z) = -i casinh(iz)
22359 catan(z) = -i catanh(iz)
22360 ccos(z) = ccosh(iz)
22361 csin(z) = -i csinh(iz)
22362 ctan(z) = -i ctanh(iz)</pre>
22363 For the other functions, the following subclauses specify behavior for special cases,
22364 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
22365 families of functions, the specifications apply to all of the functions even though only the
22366 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
22367 specifications for the upper half-plane imply the specifications for the lower half-plane; if
22368 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
22369 specifications for the first quadrant imply the specifications for the other three quadrants.
22371 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
22379 <p><small><a name="note326" href="#note326">326)</a> As noted in <a href="#G.3">G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its
22380 other part is a NaN.
22383 <h4><a name="G.6.1" href="#G.6.1">G.6.1 Trigonometric functions</a></h4>
22385 <h5><a name="G.6.1.1" href="#G.6.1.1">G.6.1.1 The cacos functions</a></h5>
22388 <li> cacos(conj(z)) = conj(cacos(z)).
22389 <li> cacos((+-)0 + i0) returns pi /2 - i0.
22390 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
22391 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
22392 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22393 point exception, for nonzero finite x.
22394 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
22395 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
22396 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
22397 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
22398 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22399 result is unspecified).
22400 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22401 point exception, for finite y.
22402 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
22403 <li> cacos(NaN + iNaN) returns NaN + iNaN.
22406 <h4><a name="G.6.2" href="#G.6.2">G.6.2 Hyperbolic functions</a></h4>
22408 <h5><a name="G.6.2.1" href="#G.6.2.1">G.6.2.1 The cacosh functions</a></h5>
22411 <li> cacosh(conj(z)) = conj(cacosh(z)).
22412 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
22413 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22414 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22415 floating-point exception, for finite x.
22416 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
22417 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
22418 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22419 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22420 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
22422 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22423 floating-point exception, for finite y.
22424 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
22425 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
22428 <h5><a name="G.6.2.2" href="#G.6.2.2">G.6.2.2 The casinh functions</a></h5>
22431 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
22432 <li> casinh(+0 + i0) returns 0 + i0.
22433 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
22434 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22435 floating-point exception, for finite x.
22436 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
22437 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22438 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
22439 <li> casinh(NaN + i0) returns NaN + i0.
22440 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22441 floating-point exception, for finite nonzero y.
22442 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22444 <li> casinh(NaN + iNaN) returns NaN + iNaN.
22447 <h5><a name="G.6.2.3" href="#G.6.2.3">G.6.2.3 The catanh functions</a></h5>
22450 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
22451 <li> catanh(+0 + i0) returns +0 + i0.
22452 <li> catanh(+0 + iNaN) returns +0 + iNaN.
22453 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
22455 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
22456 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22457 floating-point exception, for nonzero finite x.
22458 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
22459 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
22460 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
22462 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22463 floating-point exception, for finite y.
22464 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
22466 <li> catanh(NaN + iNaN) returns NaN + iNaN.
22469 <h5><a name="G.6.2.4" href="#G.6.2.4">G.6.2.4 The ccosh functions</a></h5>
22472 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
22473 <li> ccosh(+0 + i0) returns 1 + i0.
22474 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
22475 result is unspecified) and raises the ''invalid'' floating-point exception.
22476 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
22477 result is unspecified).
22478 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22479 exception, for finite nonzero x.
22480 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22481 point exception, for finite nonzero x.
22482 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
22483 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22484 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22485 unspecified) and raises the ''invalid'' floating-point exception.
22486 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
22487 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
22488 result is unspecified).
22489 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22490 point exception, for all nonzero numbers y.
22491 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
22494 <h5><a name="G.6.2.5" href="#G.6.2.5">G.6.2.5 The csinh functions</a></h5>
22497 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
22498 <li> csinh(+0 + i0) returns +0 + i0.
22499 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
22500 unspecified) and raises the ''invalid'' floating-point exception.
22501 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
22504 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22505 exception, for positive finite x.
22506 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22507 point exception, for finite nonzero x.
22508 <li> csinh(+(inf) + i0) returns +(inf) + i0.
22509 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
22510 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22511 unspecified) and raises the ''invalid'' floating-point exception.
22512 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22514 <li> csinh(NaN + i0) returns NaN + i0.
22515 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22516 point exception, for all nonzero numbers y.
22517 <li> csinh(NaN + iNaN) returns NaN + iNaN.
22520 <h5><a name="G.6.2.6" href="#G.6.2.6">G.6.2.6 The ctanh functions</a></h5>
22523 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
22524 <li> ctanh(+0 + i0) returns +0 + i0.
22525 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22526 exception, for finite x.
22527 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22528 point exception, for finite x.
22529 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
22530 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
22532 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
22533 result is unspecified).
22534 <li> ctanh(NaN + i0) returns NaN + i0.
22535 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22536 point exception, for all nonzero numbers y.
22537 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
22541 <h4><a name="G.6.3" href="#G.6.3">G.6.3 Exponential and logarithmic functions</a></h4>
22543 <h5><a name="G.6.3.1" href="#G.6.3.1">G.6.3.1 The cexp functions</a></h5>
22546 <li> cexp(conj(z)) = conj(cexp(z)).
22547 <li> cexp((+-)0 + i0) returns 1 + i0.
22548 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22549 exception, for finite x.
22550 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22551 point exception, for finite x.
22552 <li> cexp(+(inf) + i0) returns +(inf) + i0.
22553 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
22554 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22555 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
22556 the result are unspecified).
22557 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
22558 exception (where the sign of the real part of the result is unspecified).
22559 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
22560 of the result are unspecified).
22561 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22563 <li> cexp(NaN + i0) returns NaN + i0.
22564 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22565 point exception, for all nonzero numbers y.
22566 <li> cexp(NaN + iNaN) returns NaN + iNaN.
22569 <h5><a name="G.6.3.2" href="#G.6.3.2">G.6.3.2 The clog functions</a></h5>
22572 <li> clog(conj(z)) = conj(clog(z)).
22573 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
22575 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
22577 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22578 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22579 point exception, for finite x.
22581 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
22582 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22583 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22584 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
22585 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
22586 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22587 point exception, for finite y.
22588 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
22589 <li> clog(NaN + iNaN) returns NaN + iNaN.
22592 <h4><a name="G.6.4" href="#G.6.4">G.6.4 Power and absolute-value functions</a></h4>
22594 <h5><a name="G.6.4.1" href="#G.6.4.1">G.6.4.1 The cpow functions</a></h5>
22596 The cpow functions raise floating-point exceptions if appropriate for the calculation of
22597 the parts of the result, and may raise spurious exceptions.<sup><a href="#note327"><b>327)</b></a></sup>
22600 <p><small><a name="note327" href="#note327">327)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
22601 implementations that treat special cases more carefully.
22604 <h5><a name="G.6.4.2" href="#G.6.4.2">G.6.4.2 The csqrt functions</a></h5>
22607 <li> csqrt(conj(z)) = conj(csqrt(z)).
22608 <li> csqrt((+-)0 + i0) returns +0 + i0.
22609 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
22610 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22611 point exception, for finite x.
22612 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
22613 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22614 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22615 result is unspecified).
22616 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
22617 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22618 point exception, for finite y.
22619 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
22627 <h3><a name="G.7" href="#G.7">G.7 Type-generic math <tgmath.h></a></h3>
22629 Type-generic macros that accept complex arguments also accept imaginary arguments. If
22630 an argument is imaginary, the macro expands to an expression whose type is real,
22631 imaginary, or complex, as appropriate for the particular function: if the argument is
22632 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
22633 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
22634 the types of the others are complex.
22636 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
22637 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
22642 sin(iy) = i sinh(y)
22643 tan(iy) = i tanh(y)
22645 sinh(iy) = i sin(y)
22646 tanh(iy) = i tan(y)
22647 asin(iy) = i asinh(y)
22648 atan(iy) = i atanh(y)
22649 asinh(iy) = i asin(y)
22650 atanh(iy) = i atan(y)</pre>
22652 <h2><a name="H" href="#H">Annex H</a></h2>
22655 Language independent arithmetic</pre>
22657 <h3><a name="H.1" href="#H.1">H.1 Introduction</a></h3>
22659 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
22660 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
22661 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
22663 <h3><a name="H.2" href="#H.2">H.2 Types</a></h3>
22665 The relevant C arithmetic types meet the requirements of LIA-1 types if an
22666 implementation adds notification of exceptional arithmetic operations and meets the 1
22667 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
22669 <h4><a name="H.2.1" href="#H.2.1">H.2.1 Boolean type</a></h4>
22671 The LIA-1 data type Boolean is implemented by the C data type bool with values of
22672 true and false, all from <a href="#7.16"><stdbool.h></a>.
22674 <h4><a name="H.2.2" href="#H.2.2">H.2.2 Integer types</a></h4>
22676 The signed C integer types int, long int, long long int, and the corresponding
22677 unsigned types are compatible with LIA-1. If an implementation adds support for the
22678 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
22679 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
22680 in that overflows or out-of-bounds results silently wrap. An implementation that defines
22681 signed integer types as also being modulo need not detect integer overflow, in which case,
22682 only integer divide-by-zero need be detected.
22684 The parameters for the integer data types can be accessed by the following:
22685 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
22688 minint INT_MIN, LONG_MIN, LLONG_MIN
22690 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
22691 is always 0 for the unsigned types, and is not provided for those types.
22694 <h5><a name="H.2.2.1" href="#H.2.2.1">H.2.2.1 Integer operations</a></h5>
22696 The integer operations on integer types are the following:
22703 absI abs(x), labs(x), llabs(x)
22710 where x and y are expressions of the same integer type.
22712 <h4><a name="H.2.3" href="#H.2.3">H.2.3 Floating-point types</a></h4>
22714 The C floating-point types float, double, and long double are compatible with
22715 LIA-1. If an implementation adds support for the LIA-1 exceptional values
22716 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
22717 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
22718 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
22721 <h5><a name="H.2.3.1" href="#H.2.3.1">H.2.3.1 Floating-point parameters</a></h5>
22723 The parameters for a floating point data type can be accessed by the following:
22725 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
22726 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
22727 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
22729 The derived constants for the floating point types are accessed by the following:
22731 fmax FLT_MAX, DBL_MAX, LDBL_MAX
22732 fminN FLT_MIN, DBL_MIN, LDBL_MIN
22733 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
22734 rnd_style FLT_ROUNDS
22736 <h5><a name="H.2.3.2" href="#H.2.3.2">H.2.3.2 Floating-point operations</a></h5>
22738 The floating-point operations on floating-point types are the following:
22744 absF fabsf(x), fabs(x), fabsl(x)
22745 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
22746 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
22748 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)</pre>
22749 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
22750 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
22757 where x and y are expressions of the same floating point type, n is of type int, and li
22758 is of type long int.
22760 <h5><a name="H.2.3.3" href="#H.2.3.3">H.2.3.3 Rounding styles</a></h5>
22762 The C Standard requires all floating types to use the same radix and rounding style, so
22763 that only one identifier for each is provided to map to LIA-1.
22765 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
22766 truncate FLT_ROUNDS == 0
22768 nearest FLT_ROUNDS == 1
22769 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
22770 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
22771 in all relevant LIA-1 operations, not just addition as in C.
22773 <h4><a name="H.2.4" href="#H.2.4">H.2.4 Type conversions</a></h4>
22775 The LIA-1 type conversions are the following type casts:
22776 cvtI' -> I (int)i, (long int)i, (long long int)i,
22778 (unsigned int)i, (unsigned long int)i,
22779 (unsigned long long int)i</pre>
22780 cvtF -> I (int)x, (long int)x, (long long int)x,
22782 (unsigned int)x, (unsigned long int)x,
22783 (unsigned long long int)x</pre>
22784 cvtI -> F (float)i, (double)i, (long double)i
22785 cvtF' -> F (float)x, (double)x, (long double)x
22787 In the above conversions from floating to integer, the use of (cast)x can be replaced with
22788 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
22789 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
22790 conversion functions, lrint(), llrint(), lround(), and llround(), can be
22791 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
22792 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
22794 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
22795 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
22796 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
22797 to 65535.0 which can then be cast to unsigned short int. But, the
22798 remainder() function is not useful for doing silent wrapping to signed integer types,
22799 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
22800 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
22803 C's conversions (casts) from floating-point to floating-point can meet LIA-1
22804 requirements if an implementation uses round-to-nearest (IEC 60559 default).
22806 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
22807 implementation uses round-to-nearest.
22810 <h3><a name="H.3" href="#H.3">H.3 Notification</a></h3>
22812 Notification is the process by which a user or program is informed that an exceptional
22813 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
22814 allows an implementation to cause a notification to occur when any arithmetic operation
22815 returns an exceptional value as defined in LIA-1 clause 5.
22817 <h4><a name="H.3.1" href="#H.3.1">H.3.1 Notification alternatives</a></h4>
22819 LIA-1 requires at least the following two alternatives for handling of notifications:
22820 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
22823 An implementation need only support a given notification alternative for the entire
22824 program. An implementation may support the ability to switch between notification
22825 alternatives during execution, but is not required to do so. An implementation can
22826 provide separate selection for each kind of notification, but this is not required.
22828 C allows an implementation to provide notification. C's SIGFPE (for traps) and
22829 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
22830 can provide LIA-1 notification.
22832 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
22833 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
22834 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
22835 and-resume behavior with the same constraint.
22837 <h5><a name="H.3.1.1" href="#H.3.1.1">H.3.1.1 Indicators</a></h5>
22839 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
22841 The following mapping is for floating-point types:
22842 undefined FE_INVALID, FE_DIVBYZERO
22843 floating_overflow FE_OVERFLOW
22844 underflow FE_UNDERFLOW
22846 The floating-point indicator interrogation and manipulation operations are:
22847 set_indicators feraiseexcept(i)
22848 clear_indicators feclearexcept(i)
22849 test_indicators fetestexcept(i)
22850 current_indicators fetestexcept(FE_ALL_EXCEPT)
22851 where i is an expression of type int representing a subset of the LIA-1 indicators.
22853 C allows an implementation to provide the following LIA-1 required behavior: at
22854 program termination if any indicator is set the implementation shall send an unambiguous
22856 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
22858 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
22859 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
22862 <h5><a name="H.3.1.2" href="#H.3.1.2">H.3.1.2 Traps</a></h5>
22864 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
22865 math library functions (which are not permitted to generate any externally visible
22866 exceptional conditions). An implementation can provide an alternative of notification
22867 through termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
22869 LIA-1 does not require that traps be precise.
22871 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
22872 is any signal raised for them.
22874 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
22875 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
22876 terminate (either default implementation behavior or user replacement for it) or trap-and-
22877 resume, at the programmer's option.
22880 <h2><a name="I" href="#I">Annex I</a></h2>
22884 Common warnings</pre>
22885 An implementation may generate warnings in many situations, none of which are
22886 specified as part of this International Standard. The following are a few of the more
22890 <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>).
22891 <li> A block with initialization of an object that has automatic storage duration is jumped
22892 into (<a href="#6.2.4">6.2.4</a>).
22893 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
22894 int or a double to an int, or a pointer to void to a pointer to any type other than
22895 a character type (<a href="#6.3">6.3</a>).
22896 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
22897 (<a href="#6.4.4.2">6.4.4.2</a>).
22898 <li> An integer character constant includes more than one character or a wide character
22899 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
22900 <li> The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
22901 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
22902 lvalue in one operand, and a side effect to, or an access to the value of, the identical
22903 lvalue in the other operand (<a href="#6.5">6.5</a>).
22904 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
22905 <li> The arguments in a function call do not agree in number and type with those of the
22906 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
22907 <li> An object is defined but not used (<a href="#6.7">6.7</a>).
22908 <li> A value is given to an object of an enumerated type other than by assignment of an
22909 enumeration constant that is a member of that type, or an enumeration object that has
22910 the same type, or the value of a function that returns the same enumerated type
22911 (<a href="#6.7.2.2">6.7.2.2</a>).
22912 <li> An aggregate has a partly bracketed initialization (<a href="#6.7.7">6.7.7</a>).
22913 <li> A statement cannot be reached (<a href="#6.8">6.8</a>).
22914 <li> A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
22915 <li> A constant expression is used as the controlling expression of a selection statement
22916 (<a href="#6.8.4">6.8.4</a>).
22918 <li> An incorrectly formed preprocessing group is encountered while skipping a
22919 preprocessing group (<a href="#6.10.1">6.10.1</a>).
22920 <li> An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
22924 <h2><a name="J" href="#J">Annex J</a></h2>
22928 Portability issues</pre>
22929 This annex collects some information about portability that appears in this International
22932 <h3><a name="J.1" href="#J.1">J.1 Unspecified behavior</a></h3>
22934 The following are unspecified:
22936 <li> The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
22937 <li> The termination status returned to the hosted environment if the return type of main
22938 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
22939 <li> The behavior of the display device if a printing character is written when the active
22940 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
22941 <li> The behavior of the display device if a backspace character is written when the active
22942 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
22943 <li> The behavior of the display device if a horizontal tab character is written when the
22944 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
22945 <li> The behavior of the display device if a vertical tab character is written when the active
22946 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
22947 <li> How an extended source character that does not correspond to a universal character
22948 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
22949 <li> Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
22950 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
22951 <li> The value of a union member other than the last one stored into (<a href="#6.2.6.1">6.2.6.1</a>).
22952 <li> The representation used when storing a value in an object that has more than one
22953 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
22954 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
22955 <li> Whether certain operators can generate negative zeros and whether a negative zero
22956 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
22957 <li> Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
22958 <li> The order in which subexpressions are evaluated and the order in which side effects
22959 take place, except as specified for the function-call (), &&, ||, ?:, and comma
22960 operators (<a href="#6.5">6.5</a>).
22962 <li> The order in which the function designator, arguments, and subexpressions within the
22963 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
22964 <li> The order of side effects among compound literal initialization list expressions
22965 (<a href="#6.5.2.5">6.5.2.5</a>).
22966 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
22967 <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>).
22968 <li> Whether a call to an inline function uses the inline definition or the external definition
22969 of the function (<a href="#6.7.4">6.7.4</a>).
22970 <li> Whether or not a size expression is evaluated when it is part of the operand of a
22971 sizeof operator and changing the value of the size expression would not affect the
22972 result of the operator (<a href="#6.7.5.2">6.7.5.2</a>).
22973 <li> The order in which any side effects occur among the initialization list expressions in
22974 an initializer (<a href="#6.7.8">6.7.8</a>).
22975 <li> The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
22976 <li> When a fully expanded macro replacement list contains a function-like macro name
22977 as its last preprocessing token and the next preprocessing token from the source file is
22978 a (, and the fully expanded replacement of that macro ends with the name of the first
22979 macro and the next preprocessing token from the source file is again a (, whether that
22980 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
22981 <li> The order in which # and ## operations are evaluated during macro substitution
22982 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
22983 <li> Whether errno is a macro or an identifier with external linkage (<a href="#7.5">7.5</a>).
22984 <li> The state of the floating-point status flags when execution passes from a part of the
22985 program translated with FENV_ACCESS ''off'' to a part translated with
22986 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
22987 <li> The order in which feraiseexcept raises floating-point exceptions, except as
22988 stated in <a href="#F.7.6">F.7.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
22989 <li> Whether math_errhandling is a macro or an identifier with external linkage
22990 (<a href="#7.12">7.12</a>).
22991 <li> The results of the frexp functions when the specified value is not a floating-point
22992 number (<a href="#7.12.6.4">7.12.6.4</a>).
22993 <li> The numeric result of the ilogb functions when the correct value is outside the
22994 range of the return type (<a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a>).
22995 <li> The result of rounding when the value is out of range (<a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.5">F.9.6.5</a>).
22997 <li> The value stored by the remquo functions in the object pointed to by quo when y is
22998 zero (<a href="#7.12.10.3">7.12.10.3</a>).
22999 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
23000 <li> Whether va_copy and va_end are macros or identifiers with external linkage
23001 (<a href="#7.15.1">7.15.1</a>).
23002 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
23003 number is printed with an a or A conversion specifier (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23004 <li> The value of the file position indicator after a successful call to the ungetc function
23005 for a text stream, or the ungetwc function for any stream, until all pushed-back
23006 characters are read or discarded (<a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.3.10">7.24.3.10</a>).
23007 <li> The details of the value stored by the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>).
23008 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.19.9.4">7.19.9.4</a>).
23009 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
23010 functions convert a minus-signed sequence to a negative number directly or by
23011 negating the value resulting from converting the corresponding unsigned sequence
23012 (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23013 <li> The order and contiguity of storage allocated by successive calls to the calloc,
23014 malloc, and realloc functions (<a href="#7.20.3">7.20.3</a>).
23015 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
23016 realloc function when 0 bytes was requested (<a href="#7.20.3">7.20.3</a>).
23017 <li> Which of two elements that compare as equal is matched by the bsearch function
23018 (<a href="#7.20.5.1">7.20.5.1</a>).
23019 <li> The order of two elements that compare as equal in an array sorted by the qsort
23020 function (<a href="#7.20.5.2">7.20.5.2</a>).
23021 <li> The encoding of the calendar time returned by the time function (<a href="#7.23.2.4">7.23.2.4</a>).
23022 <li> The characters stored by the strftime or wcsftime function if any of the time
23023 values being converted is outside the normal range (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23024 <li> The conversion state after an encoding error occurs (<a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>,
23025 <a href="#7.24.6.4.2">7.24.6.4.2</a>,
23026 <li> The resulting value when the ''invalid'' floating-point exception is raised during
23027 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
23028 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
23029 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
23031 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
23032 exception in an IEC 60559 conformant implementation (<a href="#F.9">F.9</a>).
23033 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
23034 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.9">F.9</a>).
23035 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.9.3.4">F.9.3.4</a>).
23036 <li> The numeric result returned by the lrint, llrint, lround, and llround
23037 functions if the rounded value is outside the range of the return type (<a href="#F.9.6.5">F.9.6.5</a>, <a href="#F.9.6.7">F.9.6.7</a>).
23038 <li> The sign of one part of the complex result of several math functions for certain
23039 exceptional values in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>,
23040 <a href="#G.6.2.3">G.6.2.3</a>, <a href="#G.6.2.4">G.6.2.4</a>, <a href="#G.6.2.5">G.6.2.5</a>, <a href="#G.6.2.6">G.6.2.6</a>, <a href="#G.6.3.1">G.6.3.1</a>, <a href="#G.6.4.2">G.6.4.2</a>).
23043 <h3><a name="J.2" href="#J.2">J.2 Undefined behavior</a></h3>
23045 The behavior is undefined in the following circumstances:
23047 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
23049 <li> A nonempty source file does not end in a new-line character which is not immediately
23050 preceded by a backslash character or ends in a partial preprocessing token or
23051 comment (<a href="#5.1.1.2">5.1.1.2</a>).
23052 <li> Token concatenation produces a character sequence matching the syntax of a
23053 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
23054 <li> A program in a hosted environment does not define a function named main using one
23055 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23056 <li> A character not in the basic source character set is encountered in a source file, except
23057 in an identifier, a character constant, a string literal, a header name, a comment, or a
23058 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
23059 <li> An identifier, comment, string literal, character constant, or header name contains an
23060 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>).
23061 <li> The same identifier has both internal and external linkage in the same translation unit
23062 (<a href="#6.2.2">6.2.2</a>).
23063 <li> An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
23064 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
23065 <li> The value of an object with automatic storage duration is used while it is
23066 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.8">6.7.8</a>, <a href="#6.8">6.8</a>).
23067 <li> A trap representation is read by an lvalue expression that does not have character type
23068 (<a href="#6.2.6.1">6.2.6.1</a>).
23070 <li> A trap representation is produced by a side effect that modifies any part of the object
23071 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
23072 <li> The arguments to certain operators are such that could produce a negative zero result,
23073 but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
23074 <li> Two declarations of the same object or function specify types that are not compatible
23075 (<a href="#6.2.7">6.2.7</a>).
23076 <li> Conversion to or from an integer type produces a value outside the range that can be
23077 represented (<a href="#6.3.1.4">6.3.1.4</a>).
23078 <li> Demotion of one real floating type to another produces a value outside the range that
23079 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
23080 <li> An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
23081 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
23082 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
23083 <li> An lvalue having array type is converted to a pointer to the initial element of the
23084 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
23085 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
23086 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
23087 <li> Conversion of a pointer to an integer type produces a value outside the range that can
23088 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
23089 <li> Conversion between two pointer types produces a result that is incorrectly aligned
23090 (<a href="#6.3.2.3">6.3.2.3</a>).
23091 <li> A pointer is used to call a function whose type is not compatible with the pointed-to
23092 type (<a href="#6.3.2.3">6.3.2.3</a>).
23093 <li> An unmatched ' or " character is encountered on a logical source line during
23094 tokenization (<a href="#6.4">6.4</a>).
23095 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
23096 than as a keyword (<a href="#6.4.1">6.4.1</a>).
23097 <li> A universal character name in an identifier does not designate a character whose
23098 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
23099 <li> The initial character of an identifier is a universal character name designating a digit
23100 (<a href="#6.4.2.1">6.4.2.1</a>).
23101 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
23102 <li> The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
23104 <li> The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
23105 <li> The characters ', \, ", //, or /* occur in the sequence between the < and >
23106 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
23107 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
23108 <li> Between two sequence points, an object is modified more than once, or is modified
23109 and the prior value is read other than to determine the value to be stored (<a href="#6.5">6.5</a>).
23110 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
23111 <li> An object has its stored value accessed other than by an lvalue of an allowable type
23112 (<a href="#6.5">6.5</a>).
23113 <li> An attempt is made to modify the result of a function call, a conditional operator, an
23114 assignment operator, or a comma operator, or to access it after the next sequence
23115 point (<a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.15">6.5.15</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.17">6.5.17</a>).
23116 <li> For a call to a function without a function prototype in scope, the number of
23117 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
23118 <li> For call to a function without a function prototype in scope where the function is
23119 defined with a function prototype, either the prototype ends with an ellipsis or the
23120 types of the arguments after promotion are not compatible with the types of the
23121 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
23122 <li> For a call to a function without a function prototype in scope where the function is not
23123 defined with a function prototype, the types of the arguments after promotion are not
23124 compatible with those of the parameters after promotion (with certain exceptions)
23125 (<a href="#6.5.2.2">6.5.2.2</a>).
23126 <li> A function is defined with a type that is not compatible with the type (of the
23127 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
23128 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
23129 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
23130 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
23131 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23132 integer type produces a result that does not point into, or just beyond, the same array
23133 object (<a href="#6.5.6">6.5.6</a>).
23134 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23135 integer type produces a result that points just beyond the array object and is used as
23136 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
23137 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
23138 (<a href="#6.5.6">6.5.6</a>).
23140 <li> An array subscript is out of range, even if an object is apparently accessible with the
23141 given subscript (as in the lvalue expression a[1][7] given the declaration int
23142 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
23143 <li> The result of subtracting two pointers is not representable in an object of type
23144 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
23145 <li> An expression is shifted by a negative number or by an amount greater than or equal
23146 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
23147 <li> An expression having signed promoted type is left-shifted and either the value of the
23148 expression is negative or the result of shifting would be not be representable in the
23149 promoted type (<a href="#6.5.7">6.5.7</a>).
23150 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
23151 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
23152 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
23153 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
23154 <li> An expression that is required to be an integer constant expression does not have an
23155 integer type; has operands that are not integer constants, enumeration constants,
23156 character constants, sizeof expressions whose results are integer constants, or
23157 immediately-cast floating constants; or contains casts (outside operands to sizeof
23158 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
23159 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
23160 following: an arithmetic constant expression, a null pointer constant, an address
23161 constant, or an address constant for an object type plus or minus an integer constant
23162 expression (<a href="#6.6">6.6</a>).
23163 <li> An arithmetic constant expression does not have arithmetic type; has operands that
23164 are not integer constants, floating constants, enumeration constants, character
23165 constants, or sizeof expressions; or contains casts (outside operands to sizeof
23166 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
23167 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
23168 address &, or indirection * operator or a pointer cast in creating an address constant
23169 (<a href="#6.6">6.6</a>).
23170 <li> An identifier for an object is declared with no linkage and the type of the object is
23171 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
23172 <li> A function is declared at block scope with an explicit storage-class specifier other
23173 than extern (<a href="#6.7.1">6.7.1</a>).
23174 <li> A structure or union is defined as containing no named members (<a href="#6.7.2.1">6.7.2.1</a>).
23176 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
23177 member of a structure when the referenced object provides no elements for that array
23178 (<a href="#6.7.2.1">6.7.2.1</a>).
23179 <li> When the complete type is needed, an incomplete structure or union type is not
23180 completed in the same scope by another declaration of the tag that defines the content
23181 (<a href="#6.7.2.3">6.7.2.3</a>).
23182 <li> An attempt is made to modify an object defined with a const-qualified type through
23183 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
23184 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
23185 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23186 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
23187 <li> Two qualified types that are required to be compatible do not have the identically
23188 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
23189 <li> An object which has been modified is accessed through a restrict-qualified pointer to
23190 a const-qualified type, or through a restrict-qualified pointer and another pointer that
23191 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
23192 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
23193 whose associated block neither began execution before the block associated with this
23194 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
23195 <li> A function with external linkage is declared with an inline function specifier, but is
23196 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
23197 <li> Two pointer types that are required to be compatible are not identically qualified, or
23198 are not pointers to compatible types (<a href="#6.7.5.1">6.7.5.1</a>).
23199 <li> The size expression in an array declaration is not a constant expression and evaluates
23200 at program execution time to a nonpositive value (<a href="#6.7.5.2">6.7.5.2</a>).
23201 <li> In a context requiring two array types to be compatible, they do not have compatible
23202 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.5.2">6.7.5.2</a>).
23203 <li> A declaration of an array parameter includes the keyword static within the [ and
23204 ] and the corresponding argument does not provide access to the first element of an
23205 array with at least the specified number of elements (<a href="#6.7.5.3">6.7.5.3</a>).
23206 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
23207 parameter type list (<a href="#6.7.5.3">6.7.5.3</a>).
23208 <li> In a context requiring two function types to be compatible, they do not have
23209 compatible return types, or their parameters disagree in use of the ellipsis terminator
23210 or the number and type of parameters (after default argument promotion, when there
23211 is no parameter type list or when one type is specified by a function definition with an
23213 identifier list) (<a href="#6.7.5.3">6.7.5.3</a>).
23214 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.8">6.7.8</a>).
23215 <li> The initializer for a scalar is neither a single expression nor a single expression
23216 enclosed in braces (<a href="#6.7.8">6.7.8</a>).
23217 <li> The initializer for a structure or union object that has automatic storage duration is
23218 neither an initializer list nor a single expression that has compatible structure or union
23219 type (<a href="#6.7.8">6.7.8</a>).
23220 <li> The initializer for an aggregate or union, other than an array initialized by a string
23221 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.8">6.7.8</a>).
23222 <li> An identifier with external linkage is used, but in the program there does not exist
23223 exactly one external definition for the identifier, or the identifier is not used and there
23224 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
23225 <li> A function definition includes an identifier list, but the types of the parameters are not
23226 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
23227 <li> An adjusted parameter type in a function definition is not an object type (<a href="#6.9.1">6.9.1</a>).
23228 <li> A function that accepts a variable number of arguments is defined without a
23229 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
23230 <li> The } that terminates a function is reached, and the value of the function call is used
23231 by the caller (<a href="#6.9.1">6.9.1</a>).
23232 <li> An identifier for an object with internal linkage and an incomplete type is declared
23233 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
23234 <li> The token defined is generated during the expansion of a #if or #elif
23235 preprocessing directive, or the use of the defined unary operator does not match
23236 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
23237 <li> The #include preprocessing directive that results after expansion does not match
23238 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
23239 <li> The character sequence in an #include preprocessing directive does not start with a
23240 letter (<a href="#6.10.2">6.10.2</a>).
23241 <li> There are sequences of preprocessing tokens within the list of macro arguments that
23242 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
23243 <li> The result of the preprocessing operator # is not a valid character string literal
23244 (<a href="#6.10.3.2">6.10.3.2</a>).
23245 <li> The result of the preprocessing operator ## is not a valid preprocessing token
23246 (<a href="#6.10.3.3">6.10.3.3</a>).
23248 <li> The #line preprocessing directive that results after expansion does not match one of
23249 the two well-defined forms, or its digit sequence specifies zero or a number greater
23250 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
23251 <li> A non-STDC #pragma preprocessing directive that is documented as causing
23252 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
23253 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
23254 forms (<a href="#6.10.6">6.10.6</a>).
23255 <li> The name of a predefined macro, or the identifier defined, is the subject of a
23256 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
23257 <li> An attempt is made to copy an object to an overlapping object by use of a library
23258 function, other than as explicitly allowed (e.g., memmove) (clause 7).
23259 <li> A file with the same name as one of the standard headers, not provided as part of the
23260 implementation, is placed in any of the standard places that are searched for included
23261 source files (<a href="#7.1.2">7.1.2</a>).
23262 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
23263 <li> A function, object, type, or macro that is specified as being declared or defined by
23264 some standard header is used before any header that declares or defines it is included
23265 (<a href="#7.1.2">7.1.2</a>).
23266 <li> A standard header is included while a macro is defined with the same name as a
23267 keyword (<a href="#7.1.2">7.1.2</a>).
23268 <li> The program attempts to declare a library function itself, rather than via a standard
23269 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
23270 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
23271 (<a href="#7.1.3">7.1.3</a>).
23272 <li> The program removes the definition of a macro whose name begins with an
23273 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
23274 <li> An argument to a library function has an invalid value or a type not expected by a
23275 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
23276 <li> The pointer passed to a library function array parameter does not have a value such
23277 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
23278 <li> The macro definition of assert is suppressed in order to access an actual function
23279 (<a href="#7.2">7.2</a>).
23280 <li> The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
23281 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
23282 any context other than outside all external declarations or preceding all explicit
23284 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>).
23285 <li> The value of an argument to a character handling function is neither equal to the value
23286 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
23287 <li> A macro definition of errno is suppressed in order to access an actual object, or the
23288 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
23289 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
23290 or runs under non-default mode settings, but was translated with the state for the
23291 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
23292 <li> The exception-mask argument for one of the functions that provide access to the
23293 floating-point status flags has a nonzero value not obtained by bitwise OR of the
23294 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
23295 <li> The fesetexceptflag function is used to set floating-point status flags that were
23296 not specified in the call to the fegetexceptflag function that provided the value
23297 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
23298 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
23299 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>).
23300 <li> The value of the result of an integer arithmetic or conversion function cannot be
23301 represented (<a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.6.1">7.20.6.1</a>, <a href="#7.20.6.2">7.20.6.2</a>, <a href="#7.20.1">7.20.1</a>).
23302 <li> The program modifies the string pointed to by the value returned by the setlocale
23303 function (<a href="#7.11.1.1">7.11.1.1</a>).
23304 <li> The program modifies the structure pointed to by the value returned by the
23305 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
23306 <li> A macro definition of math_errhandling is suppressed or the program defines
23307 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
23308 <li> An argument to a floating-point classification or comparison macro is not of real
23309 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
23310 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
23311 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
23312 <li> An invocation of the setjmp macro occurs other than in an allowed context
23313 (<a href="#7.13.2.1">7.13.2.1</a>).
23314 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
23315 <li> After a longjmp, there is an attempt to access the value of an object of automatic
23316 storage class with non-volatile-qualified type, local to the function containing the
23317 invocation of the corresponding setjmp macro, that was changed between the
23318 setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
23320 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
23321 <li> A signal handler returns when the signal corresponded to a computational exception
23322 (<a href="#7.14.1.1">7.14.1.1</a>).
23323 <li> A signal occurs as the result of calling the abort or raise function, and the signal
23324 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
23325 <li> A signal occurs other than as the result of calling the abort or raise function, and
23326 the signal handler refers to an object with static storage duration other than by
23327 assigning a value to an object declared as volatile sig_atomic_t, or calls any
23328 function in the standard library other than the abort function, the _Exit function,
23329 or the signal function (for the same signal number) (<a href="#7.14.1.1">7.14.1.1</a>).
23330 <li> The value of errno is referred to after a signal occurred other than as the result of
23331 calling the abort or raise function and the corresponding signal handler obtained
23332 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
23333 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
23334 <li> A function with a variable number of arguments attempts to access its varying
23335 arguments other than through a properly declared and initialized va_list object, or
23336 before the va_start macro is invoked (<a href="#7.15">7.15</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23337 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
23338 that invoked the macro va_arg with the same parameter (<a href="#7.15">7.15</a>).
23339 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
23340 order to access an actual function, or the program defines an external identifier with
23341 the name va_copy or va_end (<a href="#7.15.1">7.15.1</a>).
23342 <li> The va_start or va_copy macro is invoked without a corresponding invocation
23343 of the va_end macro in the same function, or vice versa (<a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>,
23344 <a href="#7.15.1.4">7.15.1.4</a>).
23345 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
23346 that type can be obtained simply by postfixing a * (<a href="#7.15.1.1">7.15.1.1</a>).
23347 <li> The va_arg macro is invoked when there is no actual next argument, or with a
23348 specified type that is not compatible with the promoted type of the actual next
23349 argument, with certain exceptions (<a href="#7.15.1.1">7.15.1.1</a>).
23350 <li> The va_copy or va_start macro is called to initialize a va_list that was
23351 previously initialized by either macro without an intervening invocation of the
23352 va_end macro for the same va_list (<a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23353 <li> The parameter parmN of a va_start macro is declared with the register
23354 storage class, with a function or array type, or with a type that is not compatible with
23355 the type that results after application of the default argument promotions (<a href="#7.15.1.4">7.15.1.4</a>).
23357 <li> The member designator parameter of an offsetof macro is an invalid right
23358 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.17">7.17</a>).
23359 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
23360 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
23361 corresponding type (<a href="#7.18.4">7.18.4</a>).
23362 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
23363 input/output function is applied to a byte-oriented stream (<a href="#7.19.2">7.19.2</a>).
23364 <li> Use is made of any portion of a file beyond the most recent wide character written to
23365 a wide-oriented stream (<a href="#7.19.2">7.19.2</a>).
23366 <li> The value of a pointer to a FILE object is used after the associated file is closed
23367 (<a href="#7.19.3">7.19.3</a>).
23368 <li> The stream for the fflush function points to an input stream or to an update stream
23369 in which the most recent operation was input (<a href="#7.19.5.2">7.19.5.2</a>).
23370 <li> The string pointed to by the mode argument in a call to the fopen function does not
23371 exactly match one of the specified character sequences (<a href="#7.19.5.3">7.19.5.3</a>).
23372 <li> An output operation on an update stream is followed by an input operation without an
23373 intervening call to the fflush function or a file positioning function, or an input
23374 operation on an update stream is followed by an output operation with an intervening
23375 call to a file positioning function (<a href="#7.19.5.3">7.19.5.3</a>).
23376 <li> An attempt is made to use the contents of the array that was supplied in a call to the
23377 setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>).
23378 <li> There are insufficient arguments for the format in a call to one of the formatted
23379 input/output functions, or an argument does not have an appropriate type (<a href="#7.19.6.1">7.19.6.1</a>,
23380 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23381 <li> The format in a call to one of the formatted input/output functions or to the
23382 strftime or wcsftime function is not a valid multibyte character sequence that
23383 begins and ends in its initial shift state (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
23384 <a href="#7.24.5.1">7.24.5.1</a>).
23385 <li> In a call to one of the formatted output functions, a precision appears with a
23386 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23387 <li> A conversion specification for a formatted output function uses an asterisk to denote
23388 an argument-supplied field width or precision, but the corresponding argument is not
23389 provided (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23390 <li> A conversion specification for a formatted output function uses a # or 0 flag with a
23391 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23393 <li> A conversion specification for one of the formatted input/output functions uses a
23394 length modifier with a conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>,
23395 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23396 <li> An s conversion specifier is encountered by one of the formatted output functions,
23397 and the argument is missing the null terminator (unless a precision is specified that
23398 does not require null termination) (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23399 <li> An n conversion specification for one of the formatted input/output functions includes
23400 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.19.6.1">7.19.6.1</a>,
23401 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23402 <li> A % conversion specifier is encountered by one of the formatted input/output
23403 functions, but the complete conversion specification is not exactly %% (<a href="#7.19.6.1">7.19.6.1</a>,
23404 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23405 <li> An invalid conversion specification is found in the format for one of the formatted
23406 input/output functions, or the strftime or wcsftime function (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
23407 <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23408 <li> The number of characters transmitted by a formatted output function is greater than
23409 INT_MAX (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>).
23410 <li> The result of a conversion by one of the formatted input functions cannot be
23411 represented in the corresponding object, or the receiving object does not have an
23412 appropriate type (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23413 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
23414 functions, and the array pointed to by the corresponding argument is not large enough
23415 to accept the input sequence (and a null terminator if the conversion specifier is s or
23416 [) (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23417 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
23418 formatted input functions, but the input is not a valid multibyte character sequence
23419 that begins in the initial shift state (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23420 <li> The input item for a %p conversion by one of the formatted input functions is not a
23421 value converted earlier during the same program execution (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23422 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
23423 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
23424 vwscanf function is called with an improperly initialized va_list argument, or
23425 the argument is used (other than in an invocation of va_end) after the function
23426 returns (<a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
23427 <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>).
23428 <li> The contents of the array supplied in a call to the fgets, gets, or fgetws function
23429 are used after a read error occurred (<a href="#7.19.7.2">7.19.7.2</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.3.2">7.24.3.2</a>).
23431 <li> The file position indicator for a binary stream is used after a call to the ungetc
23432 function where its value was zero before the call (<a href="#7.19.7.11">7.19.7.11</a>).
23433 <li> The file position indicator for a stream is used after an error occurred during a call to
23434 the fread or fwrite function (<a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>).
23435 <li> A partial element read by a call to the fread function is used (<a href="#7.19.8.1">7.19.8.1</a>).
23436 <li> The fseek function is called for a text stream with a nonzero offset and either the
23437 offset was not returned by a previous successful call to the ftell function on a
23438 stream associated with the same file or whence is not SEEK_SET (<a href="#7.19.9.2">7.19.9.2</a>).
23439 <li> The fsetpos function is called to set a position that was not returned by a previous
23440 successful call to the fgetpos function on a stream associated with the same file
23441 (<a href="#7.19.9.3">7.19.9.3</a>).
23442 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
23443 with a zero requested size is used to access an object (<a href="#7.20.3">7.20.3</a>).
23444 <li> The value of a pointer that refers to space deallocated by a call to the free or
23445 realloc function is used (<a href="#7.20.3">7.20.3</a>).
23446 <li> The pointer argument to the free or realloc function does not match a pointer
23447 earlier returned by calloc, malloc, or realloc, or the space has been
23448 deallocated by a call to free or realloc (<a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a>).
23449 <li> The value of the object allocated by the malloc function is used (<a href="#7.20.3.3">7.20.3.3</a>).
23450 <li> The value of any bytes in a new object allocated by the realloc function beyond
23451 the size of the old object are used (<a href="#7.20.3.4">7.20.3.4</a>).
23452 <li> The program executes more than one call to the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
23453 <li> During the call to a function registered with the atexit function, a call is made to
23454 the longjmp function that would terminate the call to the registered function
23455 (<a href="#7.20.4.3">7.20.4.3</a>).
23456 <li> The string set up by the getenv or strerror function is modified by the program
23457 (<a href="#7.20.4.5">7.20.4.5</a>, <a href="#7.21.6.2">7.21.6.2</a>).
23458 <li> A command is executed through the system function in a way that is documented as
23459 causing termination or some other form of undefined behavior (<a href="#7.20.4.6">7.20.4.6</a>).
23460 <li> A searching or sorting utility function is called with an invalid pointer argument, even
23461 if the number of elements is zero (<a href="#7.20.5">7.20.5</a>).
23462 <li> The comparison function called by a searching or sorting utility function alters the
23463 contents of the array being searched or sorted, or returns ordering values
23464 inconsistently (<a href="#7.20.5">7.20.5</a>).
23466 <li> The array being searched by the bsearch function does not have its elements in
23467 proper order (<a href="#7.20.5.1">7.20.5.1</a>).
23468 <li> The current conversion state is used by a multibyte/wide character conversion
23469 function after changing the LC_CTYPE category (<a href="#7.20.7">7.20.7</a>).
23470 <li> A string or wide string utility function is instructed to access an array beyond the end
23471 of an object (<a href="#7.21.1">7.21.1</a>, <a href="#7.24.4">7.24.4</a>).
23472 <li> A string or wide string utility function is called with an invalid pointer argument, even
23473 if the length is zero (<a href="#7.21.1">7.21.1</a>, <a href="#7.24.4">7.24.4</a>).
23474 <li> The contents of the destination array are used after a call to the strxfrm,
23475 strftime, wcsxfrm, or wcsftime function in which the specified length was
23476 too small to hold the entire null-terminated result (<a href="#7.21.4.5">7.21.4.5</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a>,
23477 <a href="#7.24.5.1">7.24.5.1</a>).
23478 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
23479 (<a href="#7.21.5.8">7.21.5.8</a>, <a href="#7.24.4.5.7">7.24.4.5.7</a>).
23480 <li> The type of an argument to a type-generic macro is not compatible with the type of
23481 the corresponding parameter of the selected function (<a href="#7.22">7.22</a>).
23482 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
23483 has no corresponding complex function (<a href="#7.22">7.22</a>).
23484 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
23485 fwprintf function does not point to a valid multibyte character sequence that
23486 begins in the initial shift state (<a href="#7.24.2.11">7.24.2.11</a>).
23487 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
23488 value stored by the previous call for the same wide string (<a href="#7.24.4.5.7">7.24.4.5.7</a>).
23489 <li> An mbstate_t object is used inappropriately (<a href="#7.24.6">7.24.6</a>).
23490 <li> The value of an argument of type wint_t to a wide character classification or case
23491 mapping function is neither equal to the value of WEOF nor representable as a
23492 wchar_t (<a href="#7.25.1">7.25.1</a>).
23493 <li> The iswctype function is called using a different LC_CTYPE category from the
23494 one in effect for the call to the wctype function that returned the description
23495 (<a href="#7.25.2.2.1">7.25.2.2.1</a>).
23496 <li> The towctrans function is called using a different LC_CTYPE category from the
23497 one in effect for the call to the wctrans function that returned the description
23498 (<a href="#7.25.3.2.1">7.25.3.2.1</a>).
23502 <h3><a name="J.3" href="#J.3">J.3 Implementation-defined behavior</a></h3>
23504 A conforming implementation is required to document its choice of behavior in each of
23505 the areas listed in this subclause. The following are implementation-defined:
23507 <h4><a name="J.3.1" href="#J.3.1">J.3.1 Translation</a></h4>
23510 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
23511 <li> Whether each nonempty sequence of white-space characters other than new-line is
23512 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
23515 <h4><a name="J.3.2" href="#J.3.2">J.3.2 Environment</a></h4>
23518 <li> The mapping between physical source file multibyte characters and the source
23519 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
23520 <li> The name and type of the function called at program startup in a freestanding
23521 environment (<a href="#5.1.2.1">5.1.2.1</a>).
23522 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
23523 <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>).
23524 <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>).
23525 <li> What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
23526 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
23527 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
23528 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
23529 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
23530 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
23531 <li> The set of environment names and the method for altering the environment list used
23532 by the getenv function (<a href="#7.20.4.5">7.20.4.5</a>).
23533 <li> The manner of execution of the string by the system function (<a href="#7.20.4.6">7.20.4.6</a>).
23536 <h4><a name="J.3.3" href="#J.3.3">J.3.3 Identifiers</a></h4>
23539 <li> Which additional multibyte characters may appear in identifiers and their
23540 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
23541 <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>).
23545 <h4><a name="J.3.4" href="#J.3.4">J.3.4 Characters</a></h4>
23548 <li> The number of bits in a byte (<a href="#3.6">3.6</a>).
23549 <li> The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
23550 <li> The unique value of the member of the execution character set produced for each of
23551 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
23552 <li> The value of a char object into which has been stored any character other than a
23553 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
23554 <li> Which of signed char or unsigned char has the same range, representation,
23555 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>).
23556 <li> The mapping of members of the source character set (in character constants and string
23557 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>).
23558 <li> The value of an integer character constant containing more than one character or
23559 containing a character or escape sequence that does not map to a single-byte
23560 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
23561 <li> The value of a wide character constant containing more than one multibyte character,
23562 or containing a multibyte character or escape sequence not represented in the
23563 extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
23564 <li> The current locale used to convert a wide character constant consisting of a single
23565 multibyte character that maps to a member of the extended execution character set
23566 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
23567 <li> The current locale used to convert a wide string literal into corresponding wide
23568 character codes (<a href="#6.4.5">6.4.5</a>).
23569 <li> The value of a string literal containing a multibyte character or escape sequence not
23570 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
23573 <h4><a name="J.3.5" href="#J.3.5">J.3.5 Integers</a></h4>
23576 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
23577 <li> Whether signed integer types are represented using sign and magnitude, two's
23578 complement, or ones' complement, and whether the extraordinary value is a trap
23579 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
23580 <li> The rank of any extended integer type relative to another extended integer type with
23581 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
23582 <li> The result of, or the signal raised by, converting an integer to a signed integer type
23583 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
23585 <li> The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
23588 <h4><a name="J.3.6" href="#J.3.6">J.3.6 Floating point</a></h4>
23591 <li> The accuracy of the floating-point operations and of the library functions in
23592 <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>).
23593 <li> The accuracy of the conversions between floating-point internal representations and
23594 string representations performed by the library functions in <a href="#7.19"><stdio.h></a>,
23595 <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23596 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
23597 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23598 <li> The evaluation methods characterized by non-standard negative values of
23599 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23600 <li> The direction of rounding when an integer is converted to a floating-point number that
23601 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
23602 <li> The direction of rounding when a floating-point number is converted to a narrower
23603 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
23604 <li> How the nearest representable value or the larger or smaller representable value
23605 immediately adjacent to the nearest representable value is chosen for certain floating
23606 constants (<a href="#6.4.4.2">6.4.4.2</a>).
23607 <li> Whether and how floating expressions are contracted when not disallowed by the
23608 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
23609 <li> The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
23610 <li> Additional floating-point exceptions, rounding modes, environments, and
23611 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
23612 <li> The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>). *
23615 <h4><a name="J.3.7" href="#J.3.7">J.3.7 Arrays and pointers</a></h4>
23618 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
23619 <li> The size of the result of subtracting two pointers to elements of the same array
23620 (<a href="#6.5.6">6.5.6</a>).
23624 <h4><a name="J.3.8" href="#J.3.8">J.3.8 Hints</a></h4>
23627 <li> The extent to which suggestions made by using the register storage-class
23628 specifier are effective (<a href="#6.7.1">6.7.1</a>).
23629 <li> The extent to which suggestions made by using the inline function specifier are
23630 effective (<a href="#6.7.4">6.7.4</a>).
23633 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
23636 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
23637 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
23638 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
23639 (<a href="#6.7.2.1">6.7.2.1</a>).
23640 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
23641 <li> The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
23642 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
23643 no problem unless binary data written by one implementation is read by another.
23644 <li> The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
23647 <h4><a name="J.3.10" href="#J.3.10">J.3.10 Qualifiers</a></h4>
23650 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23653 <h4><a name="J.3.11" href="#J.3.11">J.3.11 Preprocessing directives</a></h4>
23656 <li> The locations within #pragma directives where header name preprocessing tokens
23657 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
23658 <li> How sequences in both forms of header names are mapped to headers or external
23659 source file names (<a href="#6.4.7">6.4.7</a>).
23660 <li> Whether the value of a character constant in a constant expression that controls
23661 conditional inclusion matches the value of the same character constant in the
23662 execution character set (<a href="#6.10.1">6.10.1</a>).
23663 <li> Whether the value of a single-character character constant in a constant expression
23664 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
23665 <li> The places that are searched for an included < > delimited header, and how the places
23666 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
23667 <li> How the named source file is searched for in an included " " delimited header
23668 (<a href="#6.10.2">6.10.2</a>).
23669 <li> The method by which preprocessing tokens (possibly resulting from macro
23670 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
23672 <li> The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
23673 <li> Whether the # operator inserts a \ character before the \ character that begins a
23674 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
23675 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
23676 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
23677 time of translation are not available (<a href="#6.10.8">6.10.8</a>).
23680 <h4><a name="J.3.12" href="#J.3.12">J.3.12 Library functions</a></h4>
23683 <li> Any library facilities available to a freestanding program, other than the minimal set
23684 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
23685 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
23686 <li> The representation of the floating-point status flags stored by the
23687 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
23688 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
23689 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
23690 (<a href="#7.6.2.3">7.6.2.3</a>).
23691 <li> Strings other than "C" and "" that may be passed as the second argument to the
23692 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
23693 <li> The types defined for float_t and double_t when the value of the
23694 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
23695 <li> Domain errors for the mathematics functions, other than those required by this
23696 International Standard (<a href="#7.12.1">7.12.1</a>).
23697 <li> The values returned by the mathematics functions on domain errors (<a href="#7.12.1">7.12.1</a>).
23698 <li> The values returned by the mathematics functions on underflow range errors, whether
23699 errno is set to the value of the macro ERANGE when the integer expression
23700 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
23701 floating-point exception is raised when the integer expression math_errhandling
23702 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
23703 <li> Whether a domain error occurs or zero is returned when an fmod function has a
23704 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
23705 <li> Whether a domain error occurs or zero is returned when a remainder function has
23706 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
23707 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
23708 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
23710 <li> Whether a domain error occurs or zero is returned when a remquo function has a
23711 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
23712 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
23713 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>).
23714 <li> The null pointer constant to which the macro NULL expands (<a href="#7.17">7.17</a>).
23715 <li> Whether the last line of a text stream requires a terminating new-line character
23716 (<a href="#7.19.2">7.19.2</a>).
23717 <li> Whether space characters that are written out to a text stream immediately before a
23718 new-line character appear when read in (<a href="#7.19.2">7.19.2</a>).
23719 <li> The number of null characters that may be appended to data written to a binary
23720 stream (<a href="#7.19.2">7.19.2</a>).
23721 <li> Whether the file position indicator of an append-mode stream is initially positioned at
23722 the beginning or end of the file (<a href="#7.19.3">7.19.3</a>).
23723 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
23724 point (<a href="#7.19.3">7.19.3</a>).
23725 <li> The characteristics of file buffering (<a href="#7.19.3">7.19.3</a>).
23726 <li> Whether a zero-length file actually exists (<a href="#7.19.3">7.19.3</a>).
23727 <li> The rules for composing valid file names (<a href="#7.19.3">7.19.3</a>).
23728 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.19.3">7.19.3</a>).
23729 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.19.3">7.19.3</a>).
23730 <li> The effect of the remove function on an open file (<a href="#7.19.4.1">7.19.4.1</a>).
23731 <li> The effect if a file with the new name exists prior to a call to the rename function
23732 (<a href="#7.19.4.2">7.19.4.2</a>).
23733 <li> Whether an open temporary file is removed upon abnormal program termination
23734 (<a href="#7.19.4.3">7.19.4.3</a>).
23735 <li> Which changes of mode are permitted (if any), and under what circumstances
23736 (<a href="#7.19.5.4">7.19.5.4</a>).
23737 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
23738 sequence printed for a NaN (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23739 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.19.6.1">7.19.6.1</a>,
23740 <a href="#7.24.2.1">7.24.2.1</a>).
23741 <li> The interpretation of a - character that is neither the first nor the last character, nor
23742 the second where a ^ character is the first, in the scanlist for %[ conversion in the
23743 fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23745 <li> The set of sequences matched by a %p conversion and the interpretation of the
23746 corresponding input item in the fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23747 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
23748 functions on failure (<a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>).
23749 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
23750 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23751 function (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23752 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23753 function sets errno to ERANGE when underflow occurs (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23754 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
23755 pointer to an allocated object when the size requested is zero (<a href="#7.20.3">7.20.3</a>).
23756 <li> Whether open streams with unwritten buffered data are flushed, open streams are
23757 closed, or temporary files are removed when the abort or _Exit function is called
23758 (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23759 <li> The termination status returned to the host environment by the abort, exit, or
23760 _Exit function (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23761 <li> The value returned by the system function when its argument is not a null pointer
23762 (<a href="#7.20.4.6">7.20.4.6</a>).
23763 <li> The local time zone and Daylight Saving Time (<a href="#7.23.1">7.23.1</a>).
23764 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.23">7.23</a>).
23765 <li> The era for the clock function (<a href="#7.23.2.1">7.23.2.1</a>).
23766 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
23767 functions in the "C" locale (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23768 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
23769 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.9">F.9</a>).
23772 <h4><a name="J.3.13" href="#J.3.13">J.3.13 Architecture</a></h4>
23775 <li> The values or expressions assigned to the macros specified in the headers
23776 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.18"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>).
23777 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
23778 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
23779 <li> The value of the result of the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>).
23783 <h3><a name="J.4" href="#J.4">J.4 Locale-specific behavior</a></h3>
23785 The following characteristics of a hosted environment are locale-specific and are required
23786 to be documented by the implementation:
23788 <li> Additional members of the source and execution character sets beyond the basic
23789 character set (<a href="#5.2.1">5.2.1</a>).
23790 <li> The presence, meaning, and representation of additional multibyte characters in the
23791 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
23792 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
23793 <li> The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
23794 <li> The decimal-point character (<a href="#7.1.1">7.1.1</a>).
23795 <li> The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.25.2">7.25.2</a>).
23796 <li> The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.25.2">7.25.2</a>).
23797 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
23798 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
23799 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>,
23800 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>).
23801 <li> The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
23802 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.20.1">7.20.1</a>,
23803 <a href="#7.24.4.1">7.24.4.1</a>).
23804 <li> The collation sequence of the execution character set (<a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>).
23805 <li> The contents of the error message strings set up by the strerror function
23806 (<a href="#7.21.6.2">7.21.6.2</a>).
23807 <li> The formats for time and date (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23808 <li> Character mappings that are supported by the towctrans function (<a href="#7.25.1">7.25.1</a>).
23809 <li> Character classifications that are supported by the iswctype function (<a href="#7.25.1">7.25.1</a>).
23813 <h3><a name="J.5" href="#J.5">J.5 Common extensions</a></h3>
23815 The following extensions are widely used in many systems, but are not portable to all
23816 implementations. The inclusion of any extension that may cause a strictly conforming
23817 program to become invalid renders an implementation nonconforming. Examples of such
23818 extensions are new keywords, extra library functions declared in standard headers, or
23819 predefined macros with names that do not begin with an underscore.
23821 <h4><a name="J.5.1" href="#J.5.1">J.5.1 Environment arguments</a></h4>
23823 In a hosted environment, the main function receives a third argument, char *envp[],
23824 that points to a null-terminated array of pointers to char, each of which points to a string
23825 that provides information about the environment for this execution of the program
23826 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23828 <h4><a name="J.5.2" href="#J.5.2">J.5.2 Specialized identifiers</a></h4>
23830 Characters other than the underscore _, letters, and digits, that are not part of the basic
23831 source character set (such as the dollar sign $, or characters in national character sets)
23832 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
23834 <h4><a name="J.5.3" href="#J.5.3">J.5.3 Lengths and cases of identifiers</a></h4>
23836 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
23838 <h4><a name="J.5.4" href="#J.5.4">J.5.4 Scopes of identifiers</a></h4>
23840 A function identifier, or the identifier of an object the declaration of which contains the
23841 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
23843 <h4><a name="J.5.5" href="#J.5.5">J.5.5 Writable string literals</a></h4>
23845 String literals are modifiable (in which case, identical string literals should denote distinct
23846 objects) (<a href="#6.4.5">6.4.5</a>).
23848 <h4><a name="J.5.6" href="#J.5.6">J.5.6 Other arithmetic types</a></h4>
23850 Additional arithmetic types, such as __int128 or double double, and their
23851 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
23852 more range or precision than long double, may be used for evaluating expressions of
23853 other floating types, and may be used to define float_t or double_t.
23856 <h4><a name="J.5.7" href="#J.5.7">J.5.7 Function pointer casts</a></h4>
23858 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
23859 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
23861 A pointer to a function may be cast to a pointer to an object or to void, allowing a
23862 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
23864 <h4><a name="J.5.8" href="#J.5.8">J.5.8 Extended bit-field types</a></h4>
23866 A bit-field may be declared with a type other than _Bool, unsigned int, or
23867 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
23869 <h4><a name="J.5.9" href="#J.5.9">J.5.9 The fortran keyword</a></h4>
23871 The fortran function specifier may be used in a function declaration to indicate that
23872 calls suitable for FORTRAN should be generated, or that a different representation for the
23873 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
23875 <h4><a name="J.5.10" href="#J.5.10">J.5.10 The asm keyword</a></h4>
23877 The asm keyword may be used to insert assembly language directly into the translator
23878 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
23880 asm ( character-string-literal );</pre>
23882 <h4><a name="J.5.11" href="#J.5.11">J.5.11 Multiple external definitions</a></h4>
23884 There may be more than one external definition for the identifier of an object, with or
23885 without the explicit use of the keyword extern; if the definitions disagree, or more than
23886 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
23888 <h4><a name="J.5.12" href="#J.5.12">J.5.12 Predefined macro names</a></h4>
23890 Macro names that do not begin with an underscore, describing the translation and
23891 execution environments, are defined by the implementation before translation begins
23892 (<a href="#6.10.8">6.10.8</a>).
23894 <h4><a name="J.5.13" href="#J.5.13">J.5.13 Floating-point status flags</a></h4>
23896 If any floating-point status flags are set on normal termination after all calls to functions
23897 registered by the atexit function have been made (see <a href="#7.20.4.3">7.20.4.3</a>), the implementation
23898 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
23901 <h4><a name="J.5.14" href="#J.5.14">J.5.14 Extra arguments for signal handlers</a></h4>
23903 Handlers for specific signals are called with extra arguments in addition to the signal
23904 number (<a href="#7.14.1.1">7.14.1.1</a>).
23906 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
23908 Additional mappings from files to streams are supported (<a href="#7.19.2">7.19.2</a>).
23910 Additional file-opening modes may be specified by characters appended to the mode
23911 argument of the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
23913 <h4><a name="J.5.16" href="#J.5.16">J.5.16 Defined file position indicator</a></h4>
23915 The file position indicator is decremented by each successful call to the ungetc or
23916 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.19.7.11">7.19.7.11</a>,
23917 <a href="#7.24.3.10">7.24.3.10</a>).
23919 <h4><a name="J.5.17" href="#J.5.17">J.5.17 Math error reporting</a></h4>
23921 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
23922 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
23923 <a href="#7.12">7.12</a>).
23926 <h2><a name="Bibliography" href="#Bibliography">Bibliography</a></h2>
23928 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
23929 published in The C Programming Language by Brian W. Kernighan and Dennis
23930 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
23931 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
23932 California, USA, November 1984.
23933 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
23934 Processing Systems, Information Processing Systems Technical Report.
23935 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
23937 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
23938 Floating-Point Arithmetic.
23939 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
23940 second edition (previously designated IEC 559:1989).
23941 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
23942 symbols for use in the physical sciences and technology.
23943 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
23944 information interchange.
23945 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
23947 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
23948 <li> ISO 8601:1988, Data elements and interchange formats -- Information
23949 interchange -- Representation of dates and times.
23950 <li> ISO/IEC 9899:1990, Programming languages -- C.
23951 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
23952 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
23953 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
23954 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
23955 Interface (POSIX) -- Part 2: Shell and Utilities.
23956 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
23957 preparation of programming language standards.
23958 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
23959 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
23961 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
23962 ISO/IEC 10646-1:1993.
23963 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
23964 ISO/IEC 10646-1:1993.
23965 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
23966 Transformation Format for 16 planes of group 00 (UTF-16).
23967 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
23968 Transformation Format 8 (UTF-8).
23969 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
23970 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
23971 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
23973 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
23974 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
23975 additional characters.
23976 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
23977 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
23978 Identifiers for characters.
23979 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
23981 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
23982 Unified Canadian Aboriginal Syllabics.
23983 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
23985 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
23986 arithmetic -- Part 1: Integer and floating point arithmetic.
23991 <h2><a name="Index" href="#Index">Index</a></h2>
23993 ??? x ???, <a href="#3.18">3.18</a> , (comma punctuator), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>,
23994 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>
23995 ??? x ???, <a href="#3.19">3.19</a> - (subtraction operator), <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
23996 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
23997 != (inequality operator), <a href="#6.5.9">6.5.9</a> -- (postfix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
23998 # operator, <a href="#6.10.3.2">6.10.3.2</a> -- (prefix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
23999 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24000 # punctuator, <a href="#6.10">6.10</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
24001 ## operator, <a href="#6.10.3.3">6.10.3.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
24002 #define preprocessing directive, <a href="#6.10.3">6.10.3</a> <a href="#6.5.2.3">6.5.2.3</a>
24003 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.8">6.7.8</a>
24004 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> ... (ellipsis punctuator), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24005 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> / (division operator), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
24006 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
24007 #if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, // (comment delimiter), <a href="#6.4.9">6.4.9</a>
24008 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24009 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
24010 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
24011 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, ; (semicolon punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
24012 <a href="#6.10.2">6.10.2</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
24013 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
24014 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
24015 #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>
24016 <a href="#7.1.4">7.1.4</a> << (left-shift operator), <a href="#6.5.7">6.5.7</a>
24017 % (remainder operator), <a href="#6.5.5">6.5.5</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24018 %: (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>
24019 %:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24020 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>,
24021 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.26.1">7.26.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24022 & (address operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24023 & (bitwise AND operator), <a href="#6.5.10">6.5.10</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24024 && (logical AND operator), <a href="#6.5.13">6.5.13</a> <a href="#7.6"><fenv.h></a> header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>,
24025 &= (bitwise AND assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#H">H</a>
24026 ' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.7"><float.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24027 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24028 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24029 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24030 ( ) (parentheses punctuator), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> <a href="#7.10"><limits.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
24031 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24032 * (asterisk punctuator), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a> <a href="#7.12"><math.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>,
24033 * (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#F.9">F.9</a>, <a href="#J.5.17">J.5.17</a>
24034 * (multiplication operator), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
24035 *= (multiplication assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.14"><signal.h></a> header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
24036 + (addition operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#7.15"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24037 <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24038 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><stddef.h></a> header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24039 ++ (postfix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
24040 ++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.18"><stdint.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>,
24041 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.18">7.18</a>, <a href="#7.26.8">7.26.8</a>
24042 , (comma operator), <a href="#6.5.17">6.5.17</a>
24044 <a href="#7.19"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
24045 <a href="#7.20"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> __DATE__ macro, <a href="#6.10.8">6.10.8</a>
24046 <a href="#7.21"><string.h></a> header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a> __FILE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
24047 <a href="#7.22"><tgmath.h></a> header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> __func__ identifier, <a href="#6.4.2.2">6.4.2.2</a>, <a href="#7.2.1.1">7.2.1.1</a>
24048 <a href="#7.23"><time.h></a> header, <a href="#7.23">7.23</a> __LINE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
24049 <a href="#7.24"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, __STDC_, <a href="#6.11.9">6.11.9</a>
24050 <a href="#7.26.12">7.26.12</a>, <a href="#F">F</a> __STDC__ macro, <a href="#6.10.8">6.10.8</a>
24051 <a href="#7.25"><wctype.h></a> header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a> __STDC_CONSTANT_MACROS macro, <a href="#7.18.4">7.18.4</a>
24052 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_FORMAT_MACROS macro, <a href="#7.8.1">7.8.1</a>
24053 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8">6.10.8</a>
24054 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#F.1">F.1</a>
24055 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
24056 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8">6.10.8</a>, <a href="#G.1">G.1</a>
24057 >> (right-shift operator), <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8">6.10.8</a>
24058 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIMIT_MACROS macro, <a href="#7.18.2">7.18.2</a>,
24059 ? : (conditional operator), <a href="#6.5.15">6.5.15</a> <a href="#7.18.3">7.18.3</a>
24060 ?? (trigraph sequences), <a href="#5.2.1.1">5.2.1.1</a> __STDC_MB_MIGHT_NEQ_WC__ macro,
24061 [ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>
24062 [ ] (brackets punctuator), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_VERSION__ macro, <a href="#6.10.8">6.10.8</a>
24063 \ (backslash character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a> __TIME__ macro, <a href="#6.10.8">6.10.8</a>
24064 \ (escape character), <a href="#6.4.4.4">6.4.4.4</a> __VA_ARGS__ identifier, <a href="#6.10.3">6.10.3</a>, <a href="#6.10.3.1">6.10.3.1</a>
24065 \" (double-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, _Bool type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>, <a href="#6.7.2">6.7.2</a>
24066 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
24067 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> _Complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
24068 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Complex_I macro, <a href="#7.3.1">7.3.1</a>
24069 \0 (null character), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Exit function, <a href="#7.20.4.4">7.20.4.4</a>
24070 padding of binary stream, <a href="#7.19.2">7.19.2</a> _Imaginary keyword, <a href="#G.2">G.2</a>
24071 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
24072 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
24073 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _IOFBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24074 \f (form-feed escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _IOLBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.6">7.19.5.6</a>
24075 <a href="#7.4.1.10">7.4.1.10</a> _IONBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24076 \n (new-line escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
24077 <a href="#7.4.1.10">7.4.1.10</a> { } (braces punctuator), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>,
24078 \octal digits (octal-character escape sequence), <a href="#6.8.2">6.8.2</a>
24079 <a href="#6.4.4.4">6.4.4.4</a> { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a>
24080 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, | (bitwise inclusive OR operator), <a href="#6.5.12">6.5.12</a>
24081 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> |= (bitwise inclusive OR assignment operator),
24082 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.5.16.2">6.5.16.2</a>
24083 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> || (logical OR operator), <a href="#6.5.14">6.5.14</a>
24084 \U (universal character names), <a href="#6.4.3">6.4.3</a> ~ (bitwise complement operator), <a href="#6.5.3.3">6.5.3.3</a>
24085 \u (universal character names), <a href="#6.4.3">6.4.3</a>
24086 \v (vertical-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, abort function, <a href="#7.2.1.1">7.2.1.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>,
24087 <a href="#7.4.1.10">7.4.1.10</a> <a href="#7.20.4.1">7.20.4.1</a>
24088 \x hexadecimal digits (hexadecimal-character abs function, <a href="#7.20.6.1">7.20.6.1</a>
24089 escape sequence), <a href="#6.4.4.4">6.4.4.4</a> absolute-value functions
24090 ^ (bitwise exclusive OR operator), <a href="#6.5.11">6.5.11</a> complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
24091 ^= (bitwise exclusive OR assignment operator), integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.20.6.1">7.20.6.1</a>
24092 <a href="#6.5.16.2">6.5.16.2</a> real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a>
24093 __bool_true_false_are_defined abstract declarator, <a href="#6.7.6">6.7.6</a>
24094 macro, <a href="#7.16">7.16</a> abstract machine, <a href="#5.1.2.3">5.1.2.3</a>
24096 access, <a href="#3.1">3.1</a>, <a href="#6.7.3">6.7.3</a> array
24097 accuracy, see floating-point accuracy argument, <a href="#6.9.1">6.9.1</a>
24098 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.9.1.1">F.9.1.1</a> declarator, <a href="#6.7.5.2">6.7.5.2</a>
24099 acos type-generic macro, <a href="#7.22">7.22</a> initialization, <a href="#6.7.8">6.7.8</a>
24100 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.9.2.1">F.9.2.1</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
24101 acosh type-generic macro, <a href="#7.22">7.22</a> parameter, <a href="#6.9.1">6.9.1</a>
24102 active position, <a href="#5.2.2">5.2.2</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
24103 actual argument, <a href="#3.3">3.3</a> subscript operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
24104 actual parameter (deprecated), <a href="#3.3">3.3</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24105 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> type, <a href="#6.2.5">6.2.5</a>
24106 addition operator (+), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
24107 <a href="#G.5.2">G.5.2</a> variable length, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
24108 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24109 address constant, <a href="#6.6">6.6</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
24110 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
24111 aggregate initialization, <a href="#6.7.8">6.7.8</a> asctime function, <a href="#7.23.3.1">7.23.3.1</a>
24112 aggregate types, <a href="#6.2.5">6.2.5</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.9.1.2">F.9.1.2</a>
24113 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> asin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24114 aliasing, <a href="#6.5">6.5</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.9.2.2">F.9.2.2</a>
24115 alignment, <a href="#3.2">3.2</a> asinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24116 pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> asm keyword, <a href="#J.5.10">J.5.10</a>
24117 structure/union member, <a href="#6.7.2.1">6.7.2.1</a> assert macro, <a href="#7.2.1.1">7.2.1.1</a>
24118 allocated storage, order and contiguity, <a href="#7.20.3">7.20.3</a> assert.h header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24119 and macro, <a href="#7.9">7.9</a> assignment
24120 AND operators compound, <a href="#6.5.16.2">6.5.16.2</a>
24121 bitwise (&), <a href="#6.5.10">6.5.10</a> conversion, <a href="#6.5.16.1">6.5.16.1</a>
24122 bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> expression, <a href="#6.5.16">6.5.16</a>
24123 logical (&&), <a href="#6.5.13">6.5.13</a> operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>
24124 and_eq macro, <a href="#7.9">7.9</a> simple, <a href="#6.5.16.1">6.5.16.1</a>
24125 ANSI/IEEE 754, <a href="#F.1">F.1</a> associativity of operators, <a href="#6.5">6.5</a>
24126 ANSI/IEEE 854, <a href="#F.1">F.1</a> asterisk punctuator (*), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a>
24127 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.9.1.3">F.9.1.3</a>
24128 argument, <a href="#3.3">3.3</a> atan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24129 array, <a href="#6.9.1">6.9.1</a> atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.9.1.4">F.9.1.4</a>
24130 default promotions, <a href="#6.5.2.2">6.5.2.2</a> atan2 type-generic macro, <a href="#7.22">7.22</a>
24131 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.9.2.3">F.9.2.3</a>
24132 macro, substitution, <a href="#6.10.3.1">6.10.3.1</a> atanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24133 argument, complex, <a href="#7.3.9.1">7.3.9.1</a> atexit function, <a href="#7.20.4.2">7.20.4.2</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>,
24134 argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> <a href="#J.5.13">J.5.13</a>
24135 arithmetic constant expression, <a href="#6.6">6.6</a> atof function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.1">7.20.1.1</a>
24136 arithmetic conversions, usual, see usual arithmetic atoi function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24137 conversions atol function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24138 arithmetic operators atoll function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24139 additive, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
24140 bitwise, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
24141 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>
24142 multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24143 shift, <a href="#6.5.7">6.5.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
24144 unary, <a href="#6.5.3.3">6.5.3.3</a> backspace escape sequence (\b), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24145 arithmetic types, <a href="#6.2.5">6.2.5</a> basic character set, <a href="#3.6">3.6</a>, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>
24146 arithmetic, pointer, <a href="#6.5.6">6.5.6</a> basic types, <a href="#6.2.5">6.2.5</a>
24148 behavior, <a href="#3.4">3.4</a> call by value, <a href="#6.5.2.2">6.5.2.2</a>
24149 binary streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, calloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.1">7.20.3.1</a>, <a href="#7.20.3.2">7.20.3.2</a>,
24150 <a href="#7.19.9.4">7.19.9.4</a> <a href="#7.20.3.4">7.20.3.4</a>
24151 bit, <a href="#3.5">3.5</a> carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a>
24152 high order, <a href="#3.6">3.6</a> carg type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24153 low order, <a href="#3.6">3.6</a> carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>,
24154 bit-field, <a href="#6.7.2.1">6.7.2.1</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a>
24155 bitand macro, <a href="#7.9">7.9</a> case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24156 bitor macro, <a href="#7.9">7.9</a> case mapping functions
24157 bitwise operators, <a href="#6.5">6.5</a> character, <a href="#7.4.2">7.4.2</a>
24158 AND, <a href="#6.5.10">6.5.10</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24159 AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24160 complement (~), <a href="#6.5.3.3">6.5.3.3</a> casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a>
24161 exclusive OR, <a href="#6.5.11">6.5.11</a> type-generic macro for, <a href="#7.22">7.22</a>
24162 exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a>
24163 inclusive OR, <a href="#6.5.12">6.5.12</a> type-generic macro for, <a href="#7.22">7.22</a>
24164 inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> cast expression, <a href="#6.5.4">6.5.4</a>
24165 shift, <a href="#6.5.7">6.5.7</a> cast operator (( )), <a href="#6.5.4">6.5.4</a>
24166 blank character, <a href="#7.4.1.3">7.4.1.3</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
24167 block, <a href="#6.8">6.8</a>, <a href="#6.8.2">6.8.2</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24168 block scope, <a href="#6.2.1">6.2.1</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
24169 block structure, <a href="#6.2.1">6.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24170 bold type convention, <a href="#6.1">6.1</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.9.4.1">F.9.4.1</a>
24171 bool macro, <a href="#7.16">7.16</a> cbrt type-generic macro, <a href="#7.22">7.22</a>
24172 boolean type, <a href="#6.3.1.2">6.3.1.2</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
24173 boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24174 braces punctuator ({ }), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>, ccosh functions, <a href="#7.3.6.4">7.3.6.4</a>, <a href="#G.6.2.4">G.6.2.4</a>
24175 <a href="#6.8.2">6.8.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24176 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.9.6.1">F.9.6.1</a>
24177 brackets punctuator ([ ]), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> ceil type-generic macro, <a href="#7.22">7.22</a>
24178 branch cuts, <a href="#7.3.3">7.3.3</a> cerf function, <a href="#7.26.1">7.26.1</a>
24179 break statement, <a href="#6.8.6.3">6.8.6.3</a> cerfc function, <a href="#7.26.1">7.26.1</a>
24180 broken-down time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, cexp functions, <a href="#7.3.7.1">7.3.7.1</a>, <a href="#G.6.3.1">G.6.3.1</a>
24181 <a href="#7.23.3.1">7.23.3.1</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24182 bsearch function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a> cexp2 function, <a href="#7.26.1">7.26.1</a>
24183 btowc function, <a href="#7.24.6.1.1">7.24.6.1.1</a> cexpm1 function, <a href="#7.26.1">7.26.1</a>
24184 BUFSIZ macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.5">7.19.5.5</a> char type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>
24185 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> char type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24186 byte input/output functions, <a href="#7.19.1">7.19.1</a> <a href="#6.3.1.8">6.3.1.8</a>
24187 byte-oriented stream, <a href="#7.19.2">7.19.2</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24188 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>
24189 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24190 <a href="#C">C</a>++, <a href="#7.8.1">7.8.1</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.18.4">7.18.4</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
24191 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> character array initialization, <a href="#6.7.8">6.7.8</a>
24192 type-generic macro for, <a href="#7.22">7.22</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
24193 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24194 type-generic macro for, <a href="#7.22">7.22</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24195 cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> character classification functions, <a href="#7.4.1">7.4.1</a>
24196 type-generic macro for, <a href="#7.22">7.22</a> wide character, <a href="#7.25.2.1">7.25.2.1</a>
24197 calendar time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
24198 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> character constant, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24200 character display semantics, <a href="#5.2.2">5.2.2</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24201 character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24202 character input/output functions, <a href="#7.19.7">7.19.7</a> compliance, see conformance
24203 wide character, <a href="#7.24.3">7.24.3</a> components of time, <a href="#7.23.1">7.23.1</a>
24204 character sets, <a href="#5.2.1">5.2.1</a> composite type, <a href="#6.2.7">6.2.7</a>
24205 character string literal, see string literal compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
24206 character type conversion, <a href="#6.3.1.1">6.3.1.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
24207 character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.8">6.7.8</a> compound statement, <a href="#6.8.2">6.8.2</a>
24208 cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
24209 cimag type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> concatenation functions
24210 cis function, <a href="#G.6">G.6</a> string, <a href="#7.21.3">7.21.3</a>
24211 classification functions wide string, <a href="#7.24.4.3">7.24.4.3</a>
24212 character, <a href="#7.4.1">7.4.1</a> concatenation, preprocessing, see preprocessing
24213 floating-point, <a href="#7.12.3">7.12.3</a> concatenation
24214 wide character, <a href="#7.25.2.1">7.25.2.1</a> conceptual models, <a href="#5.1">5.1</a>
24215 extensible, <a href="#7.25.2.2">7.25.2.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
24216 clearerr function, <a href="#7.19.10.1">7.19.10.1</a> conditional operator (? :), <a href="#6.5.15">6.5.15</a>
24217 clgamma function, <a href="#7.26.1">7.26.1</a> conformance, <a href="#4">4</a>
24218 clock function, <a href="#7.23.2.1">7.23.2.1</a> conj functions, <a href="#7.3.9.3">7.3.9.3</a>, <a href="#G.6">G.6</a>
24219 clock_t type, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> conj type-generic macro, <a href="#7.22">7.22</a>
24220 CLOCKS_PER_SEC macro, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
24221 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a> const-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.7.3">6.7.3</a>
24222 type-generic macro for, <a href="#7.22">7.22</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.7.4">F.7.4</a>
24223 clog10 function, <a href="#7.26.1">7.26.1</a> constants, <a href="#6.4.4">6.4.4</a>
24224 clog1p function, <a href="#7.26.1">7.26.1</a> as primary expression, <a href="#6.5.1">6.5.1</a>
24225 clog2 function, <a href="#7.26.1">7.26.1</a> character, <a href="#6.4.4.4">6.4.4.4</a>
24226 collating sequences, <a href="#5.2.1">5.2.1</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24227 colon punctuator (:), <a href="#6.7.2.1">6.7.2.1</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
24228 comma operator (,), <a href="#6.5.17">6.5.17</a> hexadecimal, <a href="#6.4.4.1">6.4.4.1</a>
24229 comma punctuator (,), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>, integer, <a href="#6.4.4.1">6.4.4.1</a>
24230 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
24231 command processor, <a href="#7.20.4.6">7.20.4.6</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
24232 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
24233 comments, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.4.9">6.4.9</a> contiguity of allocated storage, <a href="#7.20.3">7.20.3</a>
24234 common extensions, <a href="#J.5">J.5</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
24235 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.6">F.6</a>
24236 common real type, <a href="#6.3.1.8">6.3.1.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
24237 common warnings, <a href="#I">I</a> control wide character, <a href="#7.25.2">7.25.2</a>
24238 comparison functions, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a>, <a href="#7.20.5.2">7.20.5.2</a> conversion, <a href="#6.3">6.3</a>
24239 string, <a href="#7.21.4">7.21.4</a> arithmetic operands, <a href="#6.3.1">6.3.1</a>
24240 wide string, <a href="#7.24.4.4">7.24.4.4</a> array argument, <a href="#6.9.1">6.9.1</a> *
24241 comparison macros, <a href="#7.12.14">7.12.14</a> array parameter, <a href="#6.9.1">6.9.1</a>
24242 comparison, pointer, <a href="#6.5.8">6.5.8</a> arrays, <a href="#6.3.2.1">6.3.2.1</a>
24243 compatible type, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a> boolean, <a href="#6.3.1.2">6.3.1.2</a>
24244 compl macro, <a href="#7.9">7.9</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
24245 complement operator (~), <a href="#6.5.3.3">6.5.3.3</a> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
24246 complex macro, <a href="#7.3.1">7.3.1</a> by return statement, <a href="#6.8.6.4">6.8.6.4</a>
24247 complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
24248 complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a> explicit, <a href="#6.3">6.3</a>
24249 complex type domain, <a href="#6.2.5">6.2.5</a> function, <a href="#6.3.2.1">6.3.2.1</a>
24250 complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#G">G</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
24252 function designators, <a href="#6.3.2.1">6.3.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24253 function parameter, <a href="#6.9.1">6.9.1</a> csinh functions, <a href="#7.3.6.5">7.3.6.5</a>, <a href="#G.6.2.5">G.6.2.5</a>
24254 imaginary, <a href="#G.4.1">G.4.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24255 imaginary and complex, <a href="#G.4.3">G.4.3</a> csqrt functions, <a href="#7.3.8.3">7.3.8.3</a>, <a href="#G.6.4.2">G.6.4.2</a>
24256 implicit, <a href="#6.3">6.3</a> type-generic macro for, <a href="#7.22">7.22</a>
24257 lvalues, <a href="#6.3.2.1">6.3.2.1</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
24258 pointer, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> type-generic macro for, <a href="#7.22">7.22</a>
24259 real and complex, <a href="#6.3.1.7">6.3.1.7</a> ctanh functions, <a href="#7.3.6.6">7.3.6.6</a>, <a href="#G.6.2.6">G.6.2.6</a>
24260 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24261 real floating and integer, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ctgamma function, <a href="#7.26.1">7.26.1</a>
24262 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> ctime function, <a href="#7.23.3.2">7.23.3.2</a>
24263 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24264 usual arithmetic, see usual arithmetic current object, <a href="#6.7.8">6.7.8</a>
24265 conversions CX_LIMITED_RANGE pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.3.4">7.3.4</a>
24266 void type, <a href="#6.3.2.2">6.3.2.2</a>
24267 conversion functions data stream, see streams
24268 multibyte/wide character, <a href="#7.20.7">7.20.7</a> date and time header, <a href="#7.23">7.23</a>
24269 extended, <a href="#7.24.6">7.24.6</a> Daylight Saving Time, <a href="#7.23.1">7.23.1</a>
24270 restartable, <a href="#7.24.6.3">7.24.6.3</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24271 multibyte/wide string, <a href="#7.20.8">7.20.8</a> DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24272 restartable, <a href="#7.24.6.4">7.24.6.4</a> DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24273 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24274 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24275 single byte/wide character, <a href="#7.24.6.1">7.24.6.1</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24276 time, <a href="#7.23.3">7.23.3</a> DBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24277 wide character, <a href="#7.24.5">7.24.5</a> DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24278 conversion specifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24279 <a href="#7.24.2.2">7.24.2.2</a> decimal constant, <a href="#6.4.4.1">6.4.4.1</a>
24280 conversion state, <a href="#7.20.7">7.20.7</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.24.6.2.1">7.24.6.2.1</a>, decimal digit, <a href="#5.2.1">5.2.1</a>
24281 <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4">7.24.6.4</a>, decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24282 <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24283 conversion state functions, <a href="#7.24.6.2">7.24.6.2</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.5">F.5</a>
24284 copying functions declaration specifiers, <a href="#6.7">6.7</a>
24285 string, <a href="#7.21.2">7.21.2</a> declarations, <a href="#6.7">6.7</a>
24286 wide string, <a href="#7.24.4.2">7.24.4.2</a> function, <a href="#6.7.5.3">6.7.5.3</a>
24287 copysign functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, pointer, <a href="#6.7.5.1">6.7.5.1</a>
24288 <a href="#F.9.8.1">F.9.8.1</a> structure/union, <a href="#6.7.2.1">6.7.2.1</a>
24289 copysign type-generic macro, <a href="#7.22">7.22</a> typedef, <a href="#6.7.7">6.7.7</a>
24290 correctly rounded result, <a href="#3.9">3.9</a> declarator, <a href="#6.7.5">6.7.5</a>
24291 corresponding real type, <a href="#6.2.5">6.2.5</a> abstract, <a href="#6.7.6">6.7.6</a>
24292 cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.9.1.5">F.9.1.5</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.5">6.7.5</a>
24293 cos type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
24294 cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.9.2.4">F.9.2.4</a> increment and decrement
24295 cosh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
24296 cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> default initialization, <a href="#6.7.8">6.7.8</a>
24297 type-generic macro for, <a href="#7.22">7.22</a> default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24298 cproj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> define preprocessing directive, <a href="#6.10.3">6.10.3</a>
24299 cproj type-generic macro, <a href="#7.22">7.22</a> defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a>
24300 creal functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> definition, <a href="#6.7">6.7</a>
24301 creal type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> function, <a href="#6.9.1">6.9.1</a>
24302 csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> derived declarator types, <a href="#6.2.5">6.2.5</a>
24304 derived types, <a href="#6.2.5">6.2.5</a> end-of-file indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>,
24305 designated initializer, <a href="#6.7.8">6.7.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>,
24306 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.2">7.19.10.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24307 device input/output, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.24.3.10">7.24.3.10</a>
24308 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> end-of-file macro, see EOF macro
24309 diagnostics, <a href="#5.1.1.3">5.1.1.3</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
24310 diagnostics header, <a href="#7.2">7.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
24311 difftime function, <a href="#7.23.2.2">7.23.2.2</a> enum type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.2">6.7.2.2</a>
24312 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> enumerated type, <a href="#6.2.5">6.2.5</a>
24313 digraphs, <a href="#6.4.6">6.4.6</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
24314 direct input/output functions, <a href="#7.19.8">7.19.8</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24315 display device, <a href="#5.2.2">5.2.2</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
24316 div function, <a href="#7.20.6.2">7.20.6.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
24317 div_t type, <a href="#7.20">7.20</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
24318 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24319 division operator (/), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> enumerator, <a href="#6.7.2.2">6.7.2.2</a>
24320 do statement, <a href="#6.8.5.2">6.8.5.2</a> environment, <a href="#5">5</a>
24321 documentation of implementation, <a href="#4">4</a> environment functions, <a href="#7.20.4">7.20.4</a>
24322 domain error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#7.12.4.4">7.12.4.4</a>, environment list, <a href="#7.20.4.5">7.20.4.5</a>
24323 <a href="#7.12.5.1">7.12.5.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.7">7.12.6.7</a>, environmental considerations, <a href="#5.2">5.2</a>
24324 <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.19.2">7.19.2</a>,
24325 <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.4">7.19.4.4</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.4.2">7.20.4.2</a>,
24326 <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a> <a href="#7.24.2.1">7.24.2.1</a>
24327 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> EOF macro, <a href="#7.4">7.4</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.2">7.19.5.2</a>,
24328 double _Complex type, <a href="#6.2.5">6.2.5</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.11">7.19.6.11</a>,
24329 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.4">7.19.7.4</a>,
24330 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>,
24331 double _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.4">7.24.2.4</a>,
24332 double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
24333 <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a> <a href="#7.24.3.4">7.24.3.4</a>, <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.24.6.1.2">7.24.6.1.2</a>
24334 double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a>
24335 <a href="#6.3.1.8">6.3.1.8</a> equal-to operator, see equality operator
24336 double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> equality expressions, <a href="#6.5.9">6.5.9</a>
24337 double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
24338 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> ERANGE macro, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.12.1">7.12.1</a>,
24339 double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, see
24341 EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.9.5.1">F.9.5.1</a>
24342 effective type, <a href="#6.5">6.5</a> erf type-generic macro, <a href="#7.22">7.22</a>
24343 EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.9.5.2">F.9.5.2</a>
24344 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, erfc type-generic macro, <a href="#7.22">7.22</a>
24345 see also encoding error errno macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.3.2">7.3.2</a>, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>,
24346 element type, <a href="#6.2.5">6.2.5</a> <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.4">7.19.10.4</a>,
24347 elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24348 ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a> <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>,
24349 else preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, <a href="#J.5.17">J.5.17</a>
24350 else statement, <a href="#6.8.4.1">6.8.4.1</a> errno.h header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24351 empty statement, <a href="#6.8.3">6.8.3</a> error
24352 encoding error, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, domain, see domain error
24353 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> encoding, see encoding error
24354 end-of-file, <a href="#7.24.1">7.24.1</a> range, see range error
24356 error conditions, <a href="#7.12.1">7.12.1</a> extended characters, <a href="#5.2.1">5.2.1</a>
24357 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a> extended integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>,
24358 error indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.18">7.18</a>
24359 <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.8">7.19.7.8</a>, extended multibyte/wide character conversion
24360 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.3">7.19.10.3</a>, utilities, <a href="#7.24.6">7.24.6</a>
24361 <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a> extensible wide character case mapping functions,
24362 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.25.3.2">7.25.3.2</a>
24363 error-handling functions, <a href="#7.19.10">7.19.10</a>, <a href="#7.21.6.2">7.21.6.2</a> extensible wide character classification functions,
24364 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.25.2.2">7.25.2.2</a>
24365 escape sequences, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.11.4">6.11.4</a> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
24366 evaluation format, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#7.12">7.12</a> external definition, <a href="#6.9">6.9</a>
24367 evaluation method, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#F.7.5">F.7.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
24368 evaluation order, <a href="#6.5">6.5</a> external linkage, <a href="#6.2.2">6.2.2</a>
24369 exceptional condition, <a href="#6.5">6.5</a>, <a href="#7.12.1">7.12.1</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
24370 excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, external object definitions, <a href="#6.9.2">6.9.2</a>
24371 <a href="#6.8.6.4">6.8.6.4</a>
24372 excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.9.4.2">F.9.4.2</a>
24373 exclusive OR operators fabs type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24374 bitwise (^), <a href="#6.5.11">6.5.11</a> false macro, <a href="#7.16">7.16</a>
24375 bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fclose function, <a href="#7.19.5.1">7.19.5.1</a>
24376 executable program, <a href="#5.1.1.1">5.1.1.1</a> fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.9.9.1">F.9.9.1</a>
24377 execution character set, <a href="#5.2.1">5.2.1</a> fdim type-generic macro, <a href="#7.22">7.22</a>
24378 execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
24379 environmental limits FE_DFL_ENV macro, <a href="#7.6">7.6</a>
24380 execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a> FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24381 exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a>, FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24382 <a href="#7.20.4.4">7.20.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24383 EXIT_FAILURE macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a> FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24384 EXIT_SUCCESS macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a> FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24385 exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.9.3.1">F.9.3.1</a> FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24386 exp type-generic macro, <a href="#7.22">7.22</a> FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24387 exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.9.3.2">F.9.3.2</a> FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24388 exp2 type-generic macro, <a href="#7.22">7.22</a> FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24389 explicit conversion, <a href="#6.3">6.3</a> feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a>
24390 expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.9.3.3">F.9.3.3</a> fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24391 expm1 type-generic macro, <a href="#7.22">7.22</a> fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a>
24392 exponent part, <a href="#6.4.4.2">6.4.4.2</a> fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a>
24393 exponential functions feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>,
24394 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24395 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a> fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24396 expression, <a href="#6.5">6.5</a> FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.7">F.7</a>, <a href="#F.8">F.8</a>,
24397 assignment, <a href="#6.5.16">6.5.16</a> <a href="#F.9">F.9</a>
24398 cast, <a href="#6.5.4">6.5.4</a> fenv_t type, <a href="#7.6">7.6</a>
24399 constant, <a href="#6.6">6.6</a> feof function, <a href="#7.19.10.2">7.19.10.2</a>
24400 full, <a href="#6.8">6.8</a> feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a>
24401 order of evaluation, <a href="#6.5">6.5</a> ferror function, <a href="#7.19.10.3">7.19.10.3</a>
24402 parenthesized, <a href="#6.5.1">6.5.1</a> fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a>
24403 primary, <a href="#6.5.1">6.5.1</a> fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a>
24404 unary, <a href="#6.5.3">6.5.3</a> fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a>
24405 expression statement, <a href="#6.8.3">6.8.3</a> fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a>
24406 extended character set, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.1.2">5.2.1.2</a> feupdateenv function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24408 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a>
24409 fflush function, <a href="#7.19.5.2">7.19.5.2</a>, <a href="#7.19.5.3">7.19.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.9.6.2">F.9.6.2</a>
24410 fgetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, floor type-generic macro, <a href="#7.22">7.22</a>
24411 <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.8.1">7.19.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24412 fgetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24413 fgets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.2">7.19.7.2</a> FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.8.6.4">6.8.6.4</a>,
24414 fgetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.12">7.12</a>
24415 <a href="#7.24.3.6">7.24.3.6</a> FLT_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24416 fgetws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.2">7.24.3.2</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24417 field width, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24418 file, <a href="#7.19.3">7.19.3</a> FLT_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24419 access functions, <a href="#7.19.5">7.19.5</a> FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24420 name, <a href="#7.19.3">7.19.3</a> FLT_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24421 operations, <a href="#7.19.4">7.19.4</a> FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24422 position indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24423 <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24424 <a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.2">7.19.9.2</a>, FLT_ROUNDS macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24425 <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.1">7.24.3.1</a>, fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.9.10.1">F.9.10.1</a>
24426 <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.10">7.24.3.10</a> fma type-generic macro, <a href="#7.22">7.22</a>
24427 positioning functions, <a href="#7.19.9">7.19.9</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.9.9.2">F.9.9.2</a>
24428 file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fmax type-generic macro, <a href="#7.22">7.22</a>
24429 FILE type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.9.9.3">F.9.9.3</a>
24430 FILENAME_MAX macro, <a href="#7.19.1">7.19.1</a> fmin type-generic macro, <a href="#7.22">7.22</a>
24431 flags, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.9.7.1">F.9.7.1</a>
24432 floating-point status, see floating-point status fmod type-generic macro, <a href="#7.22">7.22</a>
24433 flag fopen function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.5.4">7.19.5.4</a>
24434 flexible array member, <a href="#6.7.2.1">6.7.2.1</a> FOPEN_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.3">7.19.4.3</a>
24435 float _Complex type, <a href="#6.2.5">6.2.5</a> for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a>
24436 float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24437 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24438 float _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.4.1.10">7.4.1.10</a>
24439 float type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.2">F.2</a> formal argument (deprecated), <a href="#3.15">3.15</a>
24440 float type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, formal parameter, <a href="#3.15">3.15</a>
24441 <a href="#6.3.1.8">6.3.1.8</a> formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.19.6">7.19.6</a>
24442 float.h header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>, wide character, <a href="#7.24.2">7.24.2</a>
24443 <a href="#7.24.4.1.1">7.24.4.1.1</a> fortran keyword, <a href="#J.5.9">J.5.9</a>
24444 float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> forward reference, <a href="#3.11">3.11</a>
24445 floating constant, <a href="#6.4.4.2">6.4.4.2</a> FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see
24446 floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a> also contracted expression
24447 floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, FP_FAST_FMA macro, <a href="#7.12">7.12</a>
24448 <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> FP_FAST_FMAF macro, <a href="#7.12">7.12</a>
24449 floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a> FP_FAST_FMAL macro, <a href="#7.12">7.12</a>
24450 floating-point accuracy, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.5">6.5</a>, FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24451 <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24452 floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24453 floating-point classification functions, <a href="#7.12.3">7.12.3</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24454 floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24455 floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.7">F.7</a>, <a href="#F.7.6">F.7.6</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24456 floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.9">F.9</a> FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24457 floating-point number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
24458 floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>
24460 fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, language, <a href="#6.11">6.11</a>
24461 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.6">7.19.6.6</a>, library, <a href="#7.26">7.26</a>
24462 <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a> fwide function, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24463 fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.3">7.19.7.3</a>, fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
24464 <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.8.2">7.19.8.2</a> <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.5">7.24.2.5</a>,
24465 fputs function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.4">7.19.7.4</a> <a href="#7.24.2.11">7.24.2.11</a>
24466 fputwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.3">7.24.3.3</a>, fwrite function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.2">7.19.8.2</a>
24467 <a href="#7.24.3.8">7.24.3.8</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24468 fputws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.4">7.24.3.4</a> <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.10">7.24.3.10</a>
24469 fread function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.1">7.19.8.1</a>
24470 free function, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a>
24471 freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, general utilities, <a href="#7.20">7.20</a>
24472 <a href="#5.1.2.1">5.1.2.1</a> wide string, <a href="#7.24.4">7.24.4</a>
24473 freopen function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.4">7.19.5.4</a> general wide string utilities, <a href="#7.24.4">7.24.4</a>
24474 frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.9.3.4">F.9.3.4</a> generic parameters, <a href="#7.22">7.22</a>
24475 frexp type-generic macro, <a href="#7.22">7.22</a> getc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>
24476 fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, getchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.6">7.19.7.6</a>
24477 <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#F.3">F.3</a> getenv function, <a href="#7.20.4.5">7.20.4.5</a>
24478 fseek function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, gets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.26.9">7.26.9</a>
24479 <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.10">7.24.3.10</a> getwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.6">7.24.3.6</a>, <a href="#7.24.3.7">7.24.3.7</a>
24480 fsetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, getwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.7">7.24.3.7</a>
24481 <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.24.3.10">7.24.3.10</a> gmtime function, <a href="#7.23.3.3">7.23.3.3</a>
24482 ftell function, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a>
24483 full declarator, <a href="#6.7.5">6.7.5</a> graphic characters, <a href="#5.2.1">5.2.1</a>
24484 full expression, <a href="#6.8">6.8</a> greater-than operator (>), <a href="#6.5.8">6.5.8</a>
24485 fully buffered stream, <a href="#7.19.3">7.19.3</a> greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a>
24487 argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
24488 body, <a href="#6.9.1">6.9.1</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
24489 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>
24490 library, <a href="#7.1.4">7.1.4</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24491 declarator, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.11.6">6.11.6</a> hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a>
24492 definition, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a> hexadecimal-character escape sequence
24493 designator, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
24494 image, <a href="#5.2.3">5.2.3</a> high-order bit, <a href="#3.6">3.6</a>
24495 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24496 name length, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> horizontal-tab escape sequence (\r), <a href="#7.25.2.1.3">7.25.2.1.3</a>
24497 parameter, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
24498 prototype, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.7">6.2.7</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>
24499 <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.6">6.11.6</a>, <a href="#6.11.7">6.11.7</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.12">7.12</a> hosted execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.2">5.1.2.2</a>
24500 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.5.2">6.7.5.2</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24501 recursive call, <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24502 return, <a href="#6.8.6.4">6.8.6.4</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24503 scope, <a href="#6.2.1">6.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24504 type, <a href="#6.2.5">6.2.5</a> HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24505 type conversion, <a href="#6.3.2.1">6.3.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24506 function specifiers, <a href="#6.7.4">6.7.4</a> hyperbolic functions
24507 function type, <a href="#6.2.5">6.2.5</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
24508 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> real, <a href="#7.12.5">7.12.5</a>, <a href="#F.9.2">F.9.2</a>
24509 function-like macro, <a href="#6.10.3">6.10.3</a> hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.9.4.3">F.9.4.3</a>
24510 future directions hypot type-generic macro, <a href="#7.22">7.22</a>
24512 <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> initial position, <a href="#5.2.2">5.2.2</a>
24513 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> initial shift state, <a href="#5.2.1.2">5.2.1.2</a>
24514 linkage, see linkage initialization, <a href="#5.1.2">5.1.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.5">6.5.2.5</a>, <a href="#6.7.8">6.7.8</a>,
24515 maximum length, <a href="#6.4.2.1">6.4.2.1</a> <a href="#F.7.5">F.7.5</a>
24516 name spaces, <a href="#6.2.3">6.2.3</a> in blocks, <a href="#6.8">6.8</a>
24517 reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> initializer, <a href="#6.7.8">6.7.8</a>
24518 scope, <a href="#6.2.1">6.2.1</a> permitted form, <a href="#6.6">6.6</a>
24519 type, <a href="#6.2.5">6.2.5</a> string literal, <a href="#6.3.2.1">6.3.2.1</a>
24520 identifier list, <a href="#6.7.5">6.7.5</a> inline, <a href="#6.7.4">6.7.4</a>
24521 identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a> inner scope, <a href="#6.2.1">6.2.1</a>
24522 IEC 559, <a href="#F.1">F.1</a> input failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>
24523 IEC 60559, <a href="#2">2</a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8">6.10.8</a>, <a href="#7.3.3">7.3.3</a>, <a href="#7.6">7.6</a>, input/output functions
24524 <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.14">7.12.14</a>, <a href="#F">F</a>, <a href="#G">G</a>, <a href="#H.1">H.1</a> character, <a href="#7.19.7">7.19.7</a>
24525 IEEE 754, <a href="#F.1">F.1</a> direct, <a href="#7.19.8">7.19.8</a>
24526 IEEE 854, <a href="#F.1">F.1</a> formatted, <a href="#7.19.6">7.19.6</a>
24527 IEEE floating-point arithmetic standard, see wide character, <a href="#7.24.2">7.24.2</a>
24528 IEC 60559, ANSI/IEEE 754, wide character, <a href="#7.24.3">7.24.3</a>
24529 ANSI/IEEE 854 formatted, <a href="#7.24.2">7.24.2</a>
24530 if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, input/output header, <a href="#7.19">7.19</a>
24531 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> input/output, device, <a href="#5.1.2.3">5.1.2.3</a>
24532 if statement, <a href="#6.8.4.1">6.8.4.1</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
24533 ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24534 ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.3.1.8">6.3.1.8</a>
24535 ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a> INT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
24536 ilogb type-generic macro, <a href="#7.22">7.22</a> INT_FASTN_MIN macros, <a href="#7.18.2.3">7.18.2.3</a>
24537 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> int_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
24538 imaginary numbers, <a href="#G">G</a> INT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
24539 imaginary type domain, <a href="#G.2">G.2</a> INT_LEASTN_MIN macros, <a href="#7.18.2.2">7.18.2.2</a>
24540 imaginary types, <a href="#G">G</a> int_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
24541 imaxabs function, <a href="#7.8.2.1">7.8.2.1</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24542 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
24543 imaxdiv_t type, <a href="#7.8">7.8</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
24544 implementation, <a href="#3.12">3.12</a> <a href="#7.20.6">7.20.6</a>
24545 implementation limit, <a href="#3.13">3.13</a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.4.2.1">6.4.2.1</a>, integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
24546 <a href="#6.7.5">6.7.5</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental integer constant, <a href="#6.4.4.1">6.4.4.1</a>
24547 limits integer constant expression, <a href="#6.6">6.6</a>
24548 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
24549 implementation-defined value, <a href="#3.17.1">3.17.1</a> integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>,
24550 implicit conversion, <a href="#6.3">6.3</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>,
24551 implicit initialization, <a href="#6.7.8">6.7.8</a> <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>
24552 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
24553 inclusive OR operators integer type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24554 bitwise (|), <a href="#6.5.12">6.5.12</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
24555 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.18">7.18</a>
24556 incomplete type, <a href="#6.2.5">6.2.5</a> extended, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#7.18">7.18</a>
24557 increment operators, see arithmetic operators, interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
24558 increment and decrement internal linkage, <a href="#6.2.2">6.2.2</a>
24559 indeterminate value, <a href="#3.17.2">3.17.2</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
24560 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> interrupt, <a href="#5.2.3">5.2.3</a>
24561 inequality operator (!=), <a href="#6.5.9">6.5.9</a> INTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
24562 INFINITY macro, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> INTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
24564 INTMAX_MIN macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a> iswalpha function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24565 intmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24566 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> iswblank function, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24567 INTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> iswcntrl function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.4">7.25.2.1.4</a>,
24568 INTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24569 INTN_MIN macros, <a href="#7.18.2.1">7.18.2.1</a> iswctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
24570 intN_t types, <a href="#7.18.1.1">7.18.1.1</a> iswdigit function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24571 INTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a> <a href="#7.25.2.1.5">7.25.2.1.5</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24572 INTPTR_MIN macro, <a href="#7.18.2.4">7.18.2.4</a> iswgraph function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24573 intptr_t type, <a href="#7.18.1.4">7.18.1.4</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24574 inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a> iswlower function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>,
24575 isalnum function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24576 isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a> iswprint function, <a href="#7.25.2.1.6">7.25.2.1.6</a>, <a href="#7.25.2.1.8">7.25.2.1.8</a>,
24577 isblank function, <a href="#7.4.1.3">7.4.1.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>
24578 iscntrl function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.4">7.4.1.4</a>, <a href="#7.4.1.7">7.4.1.7</a>, iswpunct function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24579 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24580 isdigit function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.5">7.4.1.5</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24581 <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.11.1.1">7.11.1.1</a> iswspace function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24582 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24583 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24584 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24585 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>,
24586 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24587 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> iswxdigit function, <a href="#7.25.2.1.12">7.25.2.1.12</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24588 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
24589 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
24590 islower function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.2.1">7.4.2.1</a>, iteration statements, <a href="#6.8.5">6.8.5</a>
24591 <a href="#7.4.2.2">7.4.2.2</a>
24592 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jmp_buf type, <a href="#7.13">7.13</a>
24593 isnormal macro, <a href="#7.12.3.5">7.12.3.5</a> jump statements, <a href="#6.8.6">6.8.6</a>
24594 ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a>
24595 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
24596 ISO 8601, <a href="#2">2</a>, <a href="#7.23.3.5">7.23.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
24597 ISO/IEC 10646, <a href="#2">2</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.4.3">6.4.3</a>, <a href="#6.10.8">6.10.8</a>
24598 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.4">7.19.4.4</a>
24599 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
24600 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> labeled statement, <a href="#6.8.1">6.8.1</a>
24601 ISO/IEC 9945-2, <a href="#7.11">7.11</a> labs function, <a href="#7.20.6.1">7.20.6.1</a>
24602 ISO/IEC TR 10176, <a href="#D">D</a> language, <a href="#6">6</a>
24603 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> future directions, <a href="#6.11">6.11</a>
24604 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> syntax summary, <a href="#A">A</a>
24605 ispunct function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24606 <a href="#7.4.1.11">7.4.1.11</a> LC_ALL macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24607 isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>,
24608 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>
24609 <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a> LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7">7.20.7</a>,
24610 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.20.8">7.20.8</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>,
24611 isupper function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.4.2.1">7.4.2.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24612 <a href="#7.4.2.2">7.4.2.2</a> LC_MONETARY macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24613 iswalnum function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, LC_NUMERIC macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24614 <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3.5">7.23.3.5</a>
24616 lconv structure type, <a href="#7.11">7.11</a> llabs function, <a href="#7.20.6.1">7.20.6.1</a>
24617 LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv function, <a href="#7.20.6.2">7.20.6.2</a>
24618 LDBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv_t type, <a href="#7.20">7.20</a>
24619 LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24620 LDBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.24.4.1.2">7.24.4.1.2</a>
24621 LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24622 LDBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.24.4.1.2">7.24.4.1.2</a>
24623 LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a>
24624 LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint type-generic macro, <a href="#7.22">7.22</a>
24625 LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a>
24626 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.9.3.6">F.9.3.6</a> llround type-generic macro, <a href="#7.22">7.22</a>
24627 ldexp type-generic macro, <a href="#7.22">7.22</a> local time, <a href="#7.23.1">7.23.1</a>
24628 ldiv function, <a href="#7.20.6.2">7.20.6.2</a> locale, <a href="#3.4.2">3.4.2</a>
24629 ldiv_t type, <a href="#7.20">7.20</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
24630 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24631 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>
24632 left-shift operator (<<), <a href="#6.5.7">6.5.7</a> localization, <a href="#7.11">7.11</a>
24633 length localtime function, <a href="#7.23.3.4">7.23.3.4</a>
24634 external name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.9.3.7">F.9.3.7</a>
24635 function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log type-generic macro, <a href="#7.22">7.22</a>
24636 identifier, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.9.3.8">F.9.3.8</a>
24637 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 type-generic macro, <a href="#7.22">7.22</a>
24638 length function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.24.4.6.1">7.24.4.6.1</a>, log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.9.3.9">F.9.3.9</a>
24639 <a href="#7.24.6.3.1">7.24.6.3.1</a> log1p type-generic macro, <a href="#7.22">7.22</a>
24640 length modifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.9.3.10">F.9.3.10</a>
24641 <a href="#7.24.2.2">7.24.2.2</a> log2 type-generic macro, <a href="#7.22">7.22</a>
24642 less-than operator (<), <a href="#6.5.8">6.5.8</a> logarithmic functions
24643 less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
24644 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a>
24645 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.11">F.9.3.11</a>
24646 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.9.5.3">F.9.5.3</a> logb type-generic macro, <a href="#7.22">7.22</a>
24647 lgamma type-generic macro, <a href="#7.22">7.22</a> logical operators
24648 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a> AND (&&), <a href="#6.5.13">6.5.13</a>
24649 future directions, <a href="#7.26">7.26</a> negation (!), <a href="#6.5.3.3">6.5.3.3</a>
24650 summary, <a href="#B">B</a> OR (||), <a href="#6.5.14">6.5.14</a>
24651 terms, <a href="#7.1.1">7.1.1</a> logical source lines, <a href="#5.1.1.2">5.1.1.2</a>
24652 use of functions, <a href="#7.1.4">7.1.4</a> long double _Complex type, <a href="#6.2.5">6.2.5</a>
24653 lifetime, <a href="#6.2.4">6.2.4</a> long double _Complex type conversion,
24654 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>
24655 environmental, see environmental limits long double _Imaginary type, <a href="#G.2">G.2</a>
24656 implementation, see implementation limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
24657 numerical, see numerical limits long double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>,
24658 translation, see translation limits <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a>
24659 limits.h header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> long double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>,
24660 line buffered stream, <a href="#7.19.3">7.19.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
24661 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24662 line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24663 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.19.2">7.19.2</a> long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24664 preprocessing directive, <a href="#6.10">6.10</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24665 linkage, <a href="#6.2.2">6.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.4">6.7.4</a>, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
24666 <a href="#6.11.2">6.11.2</a> long long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>,
24668 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> mbsinit function, <a href="#7.24.6.2.1">7.24.6.2.1</a>
24669 long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, mbsrtowcs function, <a href="#7.24.6.4.1">7.24.6.4.1</a>
24670 <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> mbstate_t type, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24671 long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6">7.24.6</a>,
24672 LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.6.2.1">7.24.6.2.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24673 LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.20.8.1">7.20.8.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24674 longjmp function, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>, <a href="#7.20.4.3">7.20.4.3</a> mbtowc function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.20.7.2">7.20.7.2</a>, <a href="#7.20.8.1">7.20.8.1</a>,
24675 loop body, <a href="#6.8.5">6.8.5</a> <a href="#7.24.6.3">7.24.6.3</a>
24676 low-order bit, <a href="#3.6">3.6</a> member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a>
24677 lowercase letter, <a href="#5.2.1">5.2.1</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
24678 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a> memchr function, <a href="#7.21.5.1">7.21.5.1</a>
24679 lrint type-generic macro, <a href="#7.22">7.22</a> memcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.1">7.21.4.1</a>
24680 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a> memcpy function, <a href="#7.21.2.1">7.21.2.1</a>
24681 lround type-generic macro, <a href="#7.22">7.22</a> memmove function, <a href="#7.21.2.2">7.21.2.2</a>
24682 lvalue, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>, <a href="#6.5.16">6.5.16</a> memory management functions, <a href="#7.20.3">7.20.3</a>
24683 memset function, <a href="#7.21.6.1">7.21.6.1</a>
24684 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a>
24685 macro definition minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a>
24686 library function, <a href="#7.1.4">7.1.4</a> miscellaneous functions
24687 macro invocation, <a href="#6.10.3">6.10.3</a> string, <a href="#7.21.6">7.21.6</a>
24688 macro name, <a href="#6.10.3">6.10.3</a> wide string, <a href="#7.24.4.6">7.24.4.6</a>
24689 length, <a href="#5.2.4.1">5.2.4.1</a> mktime function, <a href="#7.23.2.3">7.23.2.3</a>
24690 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.9.3.12">F.9.3.12</a>
24691 redefinition, <a href="#6.10.3">6.10.3</a> modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
24692 scope, <a href="#6.10.3.5">6.10.3.5</a> modulus functions, <a href="#7.12.6.12">7.12.6.12</a>
24693 macro parameter, <a href="#6.10.3">6.10.3</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
24694 macro preprocessor, <a href="#6.10">6.10</a> multibyte character, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24695 macro replacement, <a href="#6.10.3">6.10.3</a> multibyte conversion functions
24696 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> wide character, <a href="#7.20.7">7.20.7</a>
24697 main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.4">6.7.4</a>, extended, <a href="#7.24.6">7.24.6</a>
24698 <a href="#7.19.3">7.19.3</a> restartable, <a href="#7.24.6.3">7.24.6.3</a>
24699 malloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.3">7.20.3.3</a>, wide string, <a href="#7.20.8">7.20.8</a>
24700 <a href="#7.20.3.4">7.20.3.4</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24701 manipulation functions multibyte string, <a href="#7.1.1">7.1.1</a>
24702 complex, <a href="#7.3.9">7.3.9</a> multibyte/wide character conversion functions,
24703 real, <a href="#7.12.11">7.12.11</a>, <a href="#F.9.8">F.9.8</a> <a href="#7.20.7">7.20.7</a>
24704 matching failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a> extended, <a href="#7.24.6">7.24.6</a>
24705 math.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>, restartable, <a href="#7.24.6.3">7.24.6.3</a>
24706 <a href="#J.5.17">J.5.17</a> multibyte/wide string conversion functions, <a href="#7.20.8">7.20.8</a>
24707 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24708 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
24709 MATH_ERRNO macro, <a href="#7.12">7.12</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
24710 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> multiplication operator (*), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
24711 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7.2">7.20.7.2</a>, multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24712 <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>
24713 MB_LEN_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a> n-char sequence, <a href="#7.20.1.3">7.20.1.3</a>
24714 mblen function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a> n-wchar sequence, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24715 mbrlen function, <a href="#7.24.6.3.1">7.24.6.3.1</a> name
24716 mbrtowc function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, external, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
24717 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, file, <a href="#7.19.3">7.19.3</a>
24718 <a href="#7.24.6.4.1">7.24.6.4.1</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24720 label, <a href="#6.2.3">6.2.3</a> octal-character escape sequence (\octal digits),
24721 structure/union member, <a href="#6.2.3">6.2.3</a> <a href="#6.4.4.4">6.4.4.4</a>
24722 name spaces, <a href="#6.2.3">6.2.3</a> offsetof macro, <a href="#7.17">7.17</a>
24723 named label, <a href="#6.8.1">6.8.1</a> on-off switch, <a href="#6.10.6">6.10.6</a>
24724 NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a> ones' complement, <a href="#6.2.6.2">6.2.6.2</a>
24725 nan functions, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#F.2.1">F.2.1</a>, <a href="#F.9.8.2">F.9.8.2</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
24726 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.20.4.6">7.20.4.6</a>
24727 NDEBUG macro, <a href="#7.2">7.2</a> operations on files, <a href="#7.19.4">7.19.4</a>
24728 nearbyint functions, <a href="#7.12.9.3">7.12.9.3</a>, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, operator, <a href="#6.4.6">6.4.6</a>
24729 <a href="#F.9.6.3">F.9.6.3</a> operators, <a href="#6.5">6.5</a>
24730 nearbyint type-generic macro, <a href="#7.22">7.22</a> assignment, <a href="#6.5.16">6.5.16</a>
24731 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.9.6">F.9.6</a> associativity, <a href="#6.5">6.5</a>
24732 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> equality, <a href="#6.5.9">6.5.9</a>
24733 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24734 new-line character, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#6.10.4">6.10.4</a> postfix, <a href="#6.5.2">6.5.2</a>
24735 new-line escape sequence (\n), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, precedence, <a href="#6.5">6.5</a>
24736 <a href="#7.4.1.10">7.4.1.10</a> preprocessing, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, <a href="#6.10.9">6.10.9</a>
24737 nextafter functions, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, relational, <a href="#6.5.8">6.5.8</a>
24738 <a href="#F.9.8.3">F.9.8.3</a> shift, <a href="#6.5.7">6.5.7</a>
24739 nextafter type-generic macro, <a href="#7.22">7.22</a> unary, <a href="#6.5.3">6.5.3</a>
24740 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.8.4">F.9.8.4</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
24741 nexttoward type-generic macro, <a href="#7.22">7.22</a> or macro, <a href="#7.9">7.9</a>
24742 no linkage, <a href="#6.2.2">6.2.2</a> OR operators
24743 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> bitwise exclusive (^), <a href="#6.5.11">6.5.11</a>
24744 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
24745 nonlocal jumps header, <a href="#7.13">7.13</a> bitwise inclusive (|), <a href="#6.5.12">6.5.12</a>
24746 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
24747 not macro, <a href="#7.9">7.9</a> logical (||), <a href="#6.5.14">6.5.14</a>
24748 not-equal-to operator, see inequality operator or_eq macro, <a href="#7.9">7.9</a>
24749 not_eq macro, <a href="#7.9">7.9</a> order of allocated storage, <a href="#7.20.3">7.20.3</a>
24750 null character (\0), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> order of evaluation, <a href="#6.5">6.5</a>
24751 padding of binary stream, <a href="#7.19.2">7.19.2</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
24752 NULL macro, <a href="#7.11">7.11</a>, <a href="#7.17">7.17</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, orientation of stream, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24753 <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> outer scope, <a href="#6.2.1">6.2.1</a>
24754 null pointer, <a href="#6.3.2.3">6.3.2.3</a>
24755 null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> padding
24756 null preprocessing directive, <a href="#6.10.7">6.10.7</a> binary stream, <a href="#7.19.2">7.19.2</a>
24757 null statement, <a href="#6.8.3">6.8.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
24758 null wide character, <a href="#7.1.1">7.1.1</a> structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
24759 number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> parameter, <a href="#3.15">3.15</a>
24760 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> array, <a href="#6.9.1">6.9.1</a>
24761 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> ellipsis, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24762 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
24763 macro, <a href="#6.10.3">6.10.3</a>
24764 object, <a href="#3.14">3.14</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24765 object representation, <a href="#6.2.6.1">6.2.6.1</a> program, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24766 object type, <a href="#6.2.5">6.2.5</a> parameter type list, <a href="#6.7.5.3">6.7.5.3</a>
24767 object-like macro, <a href="#6.10.3">6.10.3</a> parentheses punctuator (( )), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
24768 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.26">7.26</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
24769 octal constant, <a href="#6.4.4.1">6.4.4.1</a> parse state, <a href="#7.19.2">7.19.2</a>
24770 octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> permitted form of initializer, <a href="#6.6">6.6</a>
24772 perror function, <a href="#7.19.10.4">7.19.10.4</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
24773 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> primary expression, <a href="#6.5.1">6.5.1</a>
24774 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> printf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.10">7.19.6.10</a>
24775 placemarker, <a href="#6.10.3.3">6.10.3.3</a> printing character, <a href="#5.2.2">5.2.2</a>, <a href="#7.4">7.4</a>, <a href="#7.4.1.8">7.4.1.8</a>
24776 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> printing wide character, <a href="#7.25.2">7.25.2</a>
24777 pointer arithmetic, <a href="#6.5.6">6.5.6</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
24778 pointer comparison, <a href="#6.5.8">6.5.8</a> program execution, <a href="#5.1.2.2.2">5.1.2.2.2</a>, <a href="#5.1.2.3">5.1.2.3</a>
24779 pointer declarator, <a href="#6.7.5.1">6.7.5.1</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
24780 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> program image, <a href="#5.1.1.2">5.1.1.2</a>
24781 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
24782 pointer type, <a href="#6.2.5">6.2.5</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24783 pointer type conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> program startup, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24784 pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program structure, <a href="#5.1.1.1">5.1.1.1</a>
24785 portability, <a href="#4">4</a>, <a href="#J">J</a> program termination, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>,
24786 position indicator, file, see file position indicator <a href="#5.1.2.3">5.1.2.3</a>
24787 positive difference, <a href="#7.12.12.1">7.12.12.1</a> program, conforming, <a href="#4">4</a>
24788 positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> program, strictly conforming, <a href="#4">4</a>
24789 postfix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> promotions
24790 postfix expressions, <a href="#6.5.2">6.5.2</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
24791 postfix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
24792 pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.9.4.4">F.9.4.4</a> prototype, see function prototype
24793 pow type-generic macro, <a href="#7.22">7.22</a> pseudo-random sequence functions, <a href="#7.20.2">7.20.2</a>
24794 power functions PTRDIFF_MAX macro, <a href="#7.18.3">7.18.3</a>
24795 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> PTRDIFF_MIN macro, <a href="#7.18.3">7.18.3</a>
24796 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a> ptrdiff_t type, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24797 pp-number, <a href="#6.4.8">6.4.8</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24798 pragma operator, <a href="#6.10.9">6.10.9</a> punctuators, <a href="#6.4.6">6.4.6</a>
24799 pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> putc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.7.9">7.19.7.9</a>
24800 precedence of operators, <a href="#6.5">6.5</a> putchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.9">7.19.7.9</a>
24801 precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> puts function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.10">7.19.7.10</a>
24802 precision, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> putwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>
24803 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> putwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.9">7.24.3.9</a>
24804 predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
24805 prefix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> qsort function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.2">7.20.5.2</a>
24806 prefix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> qualified types, <a href="#6.2.5">6.2.5</a>
24807 preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
24808 preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
24809 preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24810 preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a>
24811 preprocessing operators raise function, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>, <a href="#7.20.4.1">7.20.4.1</a>
24812 #, <a href="#6.10.3.2">6.10.3.2</a> rand function, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.2.2">7.20.2.2</a>
24813 ##, <a href="#6.10.3.3">6.10.3.3</a> RAND_MAX macro, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>
24814 _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> range
24815 defined, <a href="#6.10.1">6.10.1</a> excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
24816 preprocessing tokens, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a> range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>,
24817 preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>,
24818 preprocessor, <a href="#6.10">6.10</a> <a href="#7.12.6.6">7.12.6.6</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>,
24819 PRIcFASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>,
24820 PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>,
24821 PRIcMAX macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>,
24822 PRIcN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.13.1">7.12.13.1</a>
24824 rank, see integer conversion rank same scope, <a href="#6.2.1">6.2.1</a>
24825 real floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, save calling environment function, <a href="#7.13.1">7.13.1</a>
24826 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> scalar types, <a href="#6.2.5">6.2.5</a>
24827 real floating types, <a href="#6.2.5">6.2.5</a> scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24828 real type domain, <a href="#6.2.5">6.2.5</a> scalbln type-generic macro, <a href="#7.22">7.22</a>
24829 real types, <a href="#6.2.5">6.2.5</a> scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24830 real-floating, <a href="#7.12.3">7.12.3</a> scalbn type-generic macro, <a href="#7.22">7.22</a>
24831 realloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> scanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.11">7.19.6.11</a>
24832 recommended practice, <a href="#3.16">3.16</a> scanlist, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24833 recursion, <a href="#6.5.2.2">6.5.2.2</a> scanset, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24834 recursive function call, <a href="#6.5.2.2">6.5.2.2</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24835 redefinition of macro, <a href="#6.10.3">6.10.3</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24836 reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
24837 library functions, <a href="#7.1.4">7.1.4</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
24838 referenced type, <a href="#6.2.5">6.2.5</a> SCNcMAX macros, <a href="#7.8.1">7.8.1</a>
24839 register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> SCNcN macros, <a href="#7.8.1">7.8.1</a>
24840 relational expressions, <a href="#6.5.8">6.5.8</a> SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
24841 reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
24842 remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a> search functions
24843 remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.9.7">F.9.7</a> string, <a href="#7.21.5">7.21.5</a>
24844 remainder functions, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, utility, <a href="#7.20.5">7.20.5</a>
24845 <a href="#F.9.7.2">F.9.7.2</a> wide string, <a href="#7.24.4.5">7.24.4.5</a>
24846 remainder operator (%), <a href="#6.5.5">6.5.5</a> SEEK_CUR macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24847 remainder type-generic macro, <a href="#7.22">7.22</a> SEEK_END macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24848 remove function, <a href="#7.19.4.1">7.19.4.1</a>, <a href="#7.19.4.4">7.19.4.4</a> SEEK_SET macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24849 remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.9.7.3">F.9.7.3</a> selection statements, <a href="#6.8.4">6.8.4</a>
24850 remquo type-generic macro, <a href="#7.22">7.22</a> self-referential structure, <a href="#6.7.2.3">6.7.2.3</a>
24851 rename function, <a href="#7.19.4.2">7.19.4.2</a> semicolon punctuator (;), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
24852 representations of types, <a href="#6.2.6">6.2.6</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
24853 pointer, <a href="#6.2.5">6.2.5</a> separate compilation, <a href="#5.1.1.1">5.1.1.1</a>
24854 rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> separate translation, <a href="#5.1.1.1">5.1.1.1</a>
24855 reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.8">6.8</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.19.6">7.19.6</a>,
24856 restartable multibyte/wide character conversion <a href="#7.20.5">7.20.5</a>, <a href="#7.24.2">7.24.2</a>, <a href="#C">C</a>
24857 functions, <a href="#7.24.6.3">7.24.6.3</a> sequencing of statements, <a href="#6.8">6.8</a>
24858 restartable multibyte/wide string conversion setbuf function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.5">7.19.5.5</a>
24859 functions, <a href="#7.24.6.4">7.24.6.4</a> setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
24860 restore calling environment function, <a href="#7.13.2">7.13.2</a> setjmp.h header, <a href="#7.13">7.13</a>
24861 restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24862 restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> setvbuf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>,
24863 return statement, <a href="#6.8.6.4">6.8.6.4</a> <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24864 rewind function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.5">7.19.9.5</a>, shall, <a href="#4">4</a>
24865 <a href="#7.24.3.10">7.24.3.10</a> shift expressions, <a href="#6.5.7">6.5.7</a>
24866 right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a> shift sequence, <a href="#7.1.1">7.1.1</a>
24867 right-shift operator (>>), <a href="#6.5.7">6.5.7</a> shift states, <a href="#5.2.1.2">5.2.1.2</a>
24868 rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.4">F.9.6.4</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
24869 rint type-generic macro, <a href="#7.22">7.22</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24870 round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.9.6.6">F.9.6.6</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24871 round type-generic macro, <a href="#7.22">7.22</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24872 rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24873 rvalue, <a href="#6.3.2.1">6.3.2.1</a> SHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24874 SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24876 side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
24877 SIG_ATOMIC_MAX macro, <a href="#7.18.3">7.18.3</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
24878 SIG_ATOMIC_MIN macro, <a href="#7.18.3">7.18.3</a> space character (' '), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>,
24879 sig_atomic_t type, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.18.3">7.18.3</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>
24880 SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sprintf function, <a href="#7.19.6.6">7.19.6.6</a>, <a href="#7.19.6.13">7.19.6.13</a>
24881 SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.4.5">F.9.4.5</a>
24882 SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt type-generic macro, <a href="#7.22">7.22</a>
24883 SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.20.4.1">7.20.4.1</a> srand function, <a href="#7.20.2.2">7.20.2.2</a>
24884 SIGFPE macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.5.17">J.5.17</a> sscanf function, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.14">7.19.6.14</a>
24885 SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> standard error stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.10.4">7.19.10.4</a>
24886 SIGINT macro, <a href="#7.14">7.14</a> standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a>
24887 sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24888 sign bit, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24889 signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.20.4.4">7.20.4.4</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24890 signal handler, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a> <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24891 signal handling functions, <a href="#7.14.1">7.14.1</a> <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24892 signal.h header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a> <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24893 signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a> <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24894 signals, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1">7.14.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24895 signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24896 signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24897 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
24898 signed character, <a href="#6.3.1.1">6.3.1.1</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24899 signed integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.12"><math.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>,
24900 signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#J.5.17">J.5.17</a>
24901 <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.13"><setjmp.h></a>, <a href="#7.13">7.13</a>
24902 signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
24903 significand part, <a href="#6.4.4.2">6.4.4.2</a> <a href="#7.15"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24904 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> <a href="#7.16"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24905 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.17"><stddef.h></a>, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24906 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
24907 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.9.1.6">F.9.1.6</a> <a href="#7.18"><stdint.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.18">7.18</a>,
24908 sin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#7.26.8">7.26.8</a>
24909 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#7.19"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a>
24910 single-byte/wide character conversion functions, <a href="#7.20"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a>
24911 <a href="#7.24.6.1">7.24.6.1</a> <a href="#7.21"><string.h></a>, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24912 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.22"><tgmath.h></a>, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24913 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.23"><time.h></a>, <a href="#7.23">7.23</a>
24914 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.9.2.5">F.9.2.5</a> <a href="#7.24"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>,
24915 sinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#F">F</a>
24916 SIZE_MAX macro, <a href="#7.18.3">7.18.3</a> <a href="#7.25"><wctype.h></a>, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
24917 size_t type, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.1">7.19.1</a>, standard input stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24918 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.23.1">7.23.1</a>, standard integer types, <a href="#6.2.5">6.2.5</a>
24919 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> standard output stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24920 sizeof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> standard signed integer types, <a href="#6.2.5">6.2.5</a>
24921 snprintf function, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.12">7.19.6.12</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.20.7">7.20.7</a>
24922 sorting utility functions, <a href="#7.20.5">7.20.5</a> statements, <a href="#6.8">6.8</a>
24923 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> break, <a href="#6.8.6.3">6.8.6.3</a>
24924 source file, <a href="#5.1.1.1">5.1.1.1</a> compound, <a href="#6.8.2">6.8.2</a>
24925 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> continue, <a href="#6.8.6.2">6.8.6.2</a>
24926 source file inclusion, <a href="#6.10.2">6.10.2</a> do, <a href="#6.8.5.2">6.8.5.2</a>
24928 else, <a href="#6.8.4.1">6.8.4.1</a> strictly conforming program, <a href="#4">4</a>
24929 expression, <a href="#6.8.3">6.8.3</a> string, <a href="#7.1.1">7.1.1</a>
24930 for, <a href="#6.8.5.3">6.8.5.3</a> comparison functions, <a href="#7.21.4">7.21.4</a>
24931 goto, <a href="#6.8.6.1">6.8.6.1</a> concatenation functions, <a href="#7.21.3">7.21.3</a>
24932 if, <a href="#6.8.4.1">6.8.4.1</a> conversion functions, <a href="#7.11.1.1">7.11.1.1</a>
24933 iteration, <a href="#6.8.5">6.8.5</a> copying functions, <a href="#7.21.2">7.21.2</a>
24934 jump, <a href="#6.8.6">6.8.6</a> library function conventions, <a href="#7.21.1">7.21.1</a>
24935 labeled, <a href="#6.8.1">6.8.1</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.8">6.7.8</a>
24936 null, <a href="#6.8.3">6.8.3</a> miscellaneous functions, <a href="#7.21.6">7.21.6</a>
24937 return, <a href="#6.8.6.4">6.8.6.4</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a>
24938 selection, <a href="#6.8.4">6.8.4</a> search functions, <a href="#7.21.5">7.21.5</a>
24939 sequencing, <a href="#6.8">6.8</a> string handling header, <a href="#7.21">7.21</a>
24940 switch, <a href="#6.8.4.2">6.8.4.2</a> string.h header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24941 while, <a href="#6.8.5.1">6.8.5.1</a> stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
24942 static storage duration, <a href="#6.2.4">6.2.4</a> strlen function, <a href="#7.21.6.3">7.21.6.3</a>
24943 static storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.7.1">6.7.1</a> strncat function, <a href="#7.21.3.2">7.21.3.2</a>
24944 static, in array declarators, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.5.3">6.7.5.3</a> strncmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.4">7.21.4.4</a>
24945 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a> strncpy function, <a href="#7.21.2.4">7.21.2.4</a>
24946 stdbool.h header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a> strpbrk function, <a href="#7.21.5.4">7.21.5.4</a>
24947 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> strrchr function, <a href="#7.21.5.5">7.21.5.5</a>
24948 stddef.h header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, strspn function, <a href="#7.21.5.6">7.21.5.6</a>
24949 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a> strstr function, <a href="#7.21.5.7">7.21.5.7</a>
24950 stderr macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24951 stdin macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a>
24952 <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.7">7.24.3.7</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24953 stdint.h header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.18">7.18</a>, strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
24954 <a href="#7.26.8">7.26.8</a> strtok function, <a href="#7.21.5.8">7.21.5.8</a>
24955 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24956 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24957 stdout macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.3">7.19.6.3</a>, strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24958 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>, <a href="#7.24.2.11">7.24.2.11</a>, <a href="#7.24.3.9">7.24.3.9</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24959 storage duration, <a href="#6.2.4">6.2.4</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24960 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24961 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24962 strcat function, <a href="#7.21.3.1">7.21.3.1</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
24963 strchr function, <a href="#7.21.5.2">7.21.5.2</a> struct hack, see flexible array member
24964 strcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.2">7.21.4.2</a> structure
24965 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.5">7.21.4.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24966 strcpy function, <a href="#7.21.2.3">7.21.2.3</a> content, <a href="#6.7.2.3">6.7.2.3</a>
24967 strcspn function, <a href="#7.21.5.3">7.21.5.3</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
24968 streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.20.4.3">7.20.4.3</a> initialization, <a href="#6.7.8">6.7.8</a>
24969 fully buffered, <a href="#7.19.3">7.19.3</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
24970 line buffered, <a href="#7.19.3">7.19.3</a> member name space, <a href="#6.2.3">6.2.3</a>
24971 orientation, <a href="#7.19.2">7.19.2</a> member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>
24972 standard error, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24973 standard input, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
24974 standard output, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24975 unbuffered, <a href="#7.19.3">7.19.3</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
24976 strerror function, <a href="#7.19.10.4">7.19.10.4</a>, <a href="#7.21.6.2">7.21.6.2</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.5">7.21.4.5</a>
24977 strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.5">7.23.3.5</a>, subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24978 <a href="#7.24.5.1">7.24.5.1</a> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
24980 subtraction operator (-), <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
24981 suffix toupper function, <a href="#7.4.2.2">7.4.2.2</a>
24982 floating constant, <a href="#6.4.4.2">6.4.4.2</a> towctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24983 integer constant, <a href="#6.4.4.1">6.4.4.1</a> towlower function, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24984 switch body, <a href="#6.8.4.2">6.8.4.2</a> towupper function, <a href="#7.25.3.1.2">7.25.3.1.2</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24985 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
24986 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
24987 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
24988 swprintf function, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.7">7.24.2.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
24989 swscanf function, <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.8">7.24.2.8</a> trap representation, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.2.3">6.3.2.3</a>,
24990 symbols, <a href="#3">3</a> <a href="#6.5.2.3">6.5.2.3</a>
24991 syntactic categories, <a href="#6.1">6.1</a> trigonometric functions
24992 syntax notation, <a href="#6.1">6.1</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
24993 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.9.1">F.9.1</a>
24994 syntax summary, language, <a href="#A">A</a> trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a>
24995 system function, <a href="#7.20.4.6">7.20.4.6</a> true macro, <a href="#7.16">7.16</a>
24996 trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.9.6.8">F.9.6.8</a>
24997 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> trunc type-generic macro, <a href="#7.22">7.22</a>
24998 tag compatibility, <a href="#6.2.7">6.2.7</a> truncation, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
24999 tag name space, <a href="#6.2.3">6.2.3</a> truncation toward zero, <a href="#6.5.5">6.5.5</a>
25000 tags, <a href="#6.7.2.3">6.7.2.3</a> two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
25001 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.9.1.7">F.9.1.7</a> type category, <a href="#6.2.5">6.2.5</a>
25002 tan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type conversion, <a href="#6.3">6.3</a>
25003 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.9.2.6">F.9.2.6</a> type definitions, <a href="#6.7.7">6.7.7</a>
25004 tanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
25005 tentative definition, <a href="#6.9.2">6.9.2</a> type names, <a href="#6.7.6">6.7.6</a>
25006 terms, <a href="#3">3</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
25007 text streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> type qualifiers, <a href="#6.7.3">6.7.3</a>
25008 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.9.5.4">F.9.5.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
25009 tgamma type-generic macro, <a href="#7.22">7.22</a> type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25010 tgmath.h header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> typedef declaration, <a href="#6.7.7">6.7.7</a>
25011 time typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.7">6.7.7</a>
25012 broken down, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.1">7.23.3.1</a>, types, <a href="#6.2.5">6.2.5</a>
25013 <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> character, <a href="#6.7.8">6.7.8</a>
25014 calendar, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a>
25015 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
25016 components, <a href="#7.23.1">7.23.1</a> composite, <a href="#6.2.7">6.2.7</a>
25017 conversion functions, <a href="#7.23.3">7.23.3</a> const qualified, <a href="#6.7.3">6.7.3</a>
25018 wide character, <a href="#7.24.5">7.24.5</a> conversions, <a href="#6.3">6.3</a>
25019 local, <a href="#7.23.1">7.23.1</a> imaginary, <a href="#G">G</a>
25020 manipulation functions, <a href="#7.23.2">7.23.2</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
25021 time function, <a href="#7.23.2.4">7.23.2.4</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
25022 time.h header, <a href="#7.23">7.23</a>
25023 time_t type, <a href="#7.23.1">7.23.1</a> UCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25024 tm structure type, <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> UINT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
25025 TMP_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
25026 tmpfile function, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.20.4.3">7.20.4.3</a> UINT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
25027 tmpnam function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
25028 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25029 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
25030 token pasting, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
25032 uintmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25033 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> usual arithmetic conversions, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.5.5">6.5.5</a>, <a href="#6.5.6">6.5.6</a>,
25034 UINTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> <a href="#6.5.8">6.5.8</a>, <a href="#6.5.9">6.5.9</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>, <a href="#6.5.15">6.5.15</a>
25035 UINTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> utilities, general, <a href="#7.20">7.20</a>
25036 uintN_t types, <a href="#7.18.1.1">7.18.1.1</a> wide string, <a href="#7.24.4">7.24.4</a>
25037 UINTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a>
25038 uintptr_t type, <a href="#7.18.1.4">7.18.1.4</a> va_arg macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
25039 ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
25040 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
25041 ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
25042 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25043 unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> va_copy macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
25044 unary expression, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.3">7.15.1.3</a>
25045 unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.3">7.15.1.3</a>,
25046 unary operators, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
25047 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
25048 unbuffered stream, <a href="#7.19.3">7.19.3</a> <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
25049 undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25050 <a href="#7.1.4">7.1.4</a> va_list type, <a href="#7.15">7.15</a>, <a href="#7.15.1.3">7.15.1.3</a>
25051 undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> va_start macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>,
25052 underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>,
25053 underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a> <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>,
25054 ungetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>,
25055 <a href="#7.19.9.3">7.19.9.3</a> <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25056 ungetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.10">7.24.3.10</a> value, <a href="#3.17">3.17</a>
25057 Unicode required set, <a href="#6.10.8">6.10.8</a> value bits, <a href="#6.2.6.2">6.2.6.2</a>
25058 union variable arguments, <a href="#6.10.3">6.10.3</a>, <a href="#7.15">7.15</a>
25059 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> variable arguments header, <a href="#7.15">7.15</a>
25060 content, <a href="#6.7.2.3">6.7.2.3</a> variable length array, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25061 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> variably modified type, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25062 initialization, <a href="#6.7.8">6.7.8</a> vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
25063 member alignment, <a href="#6.7.2.1">6.7.2.1</a> vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
25064 member name space, <a href="#6.2.3">6.2.3</a> <a href="#7.4.1.10">7.4.1.10</a>
25065 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> vfprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>
25066 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> vfscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>
25067 specifier, <a href="#6.7.2.1">6.7.2.1</a> vfwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.5">7.24.2.5</a>
25068 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> vfwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.3.10">7.24.3.10</a>
25069 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
25070 universal character name, <a href="#6.4.3">6.4.3</a> VLA, see variable length array
25071 unqualified type, <a href="#6.2.5">6.2.5</a> void expression, <a href="#6.3.2.2">6.3.2.2</a>
25072 unqualified version of type, <a href="#6.2.5">6.2.5</a> void function parameter, <a href="#6.7.5.3">6.7.5.3</a>
25073 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>
25074 unsigned integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
25075 unsigned type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, volatile storage, <a href="#5.1.2.3">5.1.2.3</a>
25076 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> volatile type qualifier, <a href="#6.7.3">6.7.3</a>
25077 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
25078 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> vprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>
25079 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.11">7.19.6.11</a>
25080 unspecified value, <a href="#3.17.3">3.17.3</a> vsnprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.12">7.19.6.12</a>
25081 uppercase letter, <a href="#5.2.1">5.2.1</a> vsprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.13">7.19.6.13</a>
25082 use of library functions, <a href="#7.1.4">7.1.4</a> vsscanf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.14">7.19.6.14</a>
25084 vswprintf function, <a href="#7.24.2.7">7.24.2.7</a> wctype.h header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
25085 vswscanf function, <a href="#7.24.2.8">7.24.2.8</a> wctype_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
25086 vwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a> WEOF macro, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.6">7.24.3.6</a>,
25087 vwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.3.10">7.24.3.10</a> <a href="#7.24.3.7">7.24.3.7</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>, <a href="#7.24.3.10">7.24.3.10</a>,
25088 <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.25.1">7.25.1</a>
25089 warnings, <a href="#I">I</a> while statement, <a href="#6.8.5.1">6.8.5.1</a>
25090 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>, white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
25091 <a href="#F">F</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>
25092 WCHAR_MAX macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> white-space characters, <a href="#6.4">6.4</a>
25093 WCHAR_MIN macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> wide character, <a href="#3.7.3">3.7.3</a>
25094 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.8">6.7.8</a>, case mapping functions, <a href="#7.25.3.1">7.25.3.1</a>
25095 <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, extensible, <a href="#7.25.3.2">7.25.3.2</a>
25096 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> classification functions, <a href="#7.25.2.1">7.25.2.1</a>
25097 wcrtomb function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
25098 <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
25099 wcscat function, <a href="#7.24.4.3.1">7.24.4.3.1</a> formatted input/output functions, <a href="#7.24.2">7.24.2</a>
25100 wcschr function, <a href="#7.24.4.5.1">7.24.4.5.1</a> input functions, <a href="#7.19.1">7.19.1</a>
25101 wcscmp function, <a href="#7.24.4.4.1">7.24.4.4.1</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> input/output functions, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3">7.24.3</a>
25102 wcscoll function, <a href="#7.24.4.4.2">7.24.4.4.2</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> output functions, <a href="#7.19.1">7.19.1</a>
25103 wcscpy function, <a href="#7.24.4.2.1">7.24.4.2.1</a> single-byte conversion functions, <a href="#7.24.6.1">7.24.6.1</a>
25104 wcscspn function, <a href="#7.24.4.5.2">7.24.4.5.2</a> wide string, <a href="#7.1.1">7.1.1</a>
25105 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.5.1">7.24.5.1</a> wide string comparison functions, <a href="#7.24.4.4">7.24.4.4</a>
25106 wcslen function, <a href="#7.24.4.6.1">7.24.4.6.1</a> wide string concatenation functions, <a href="#7.24.4.3">7.24.4.3</a>
25107 wcsncat function, <a href="#7.24.4.3.2">7.24.4.3.2</a> wide string copying functions, <a href="#7.24.4.2">7.24.4.2</a>
25108 wcsncmp function, <a href="#7.24.4.4.3">7.24.4.4.3</a> wide string literal, see string literal
25109 wcsncpy function, <a href="#7.24.4.2.2">7.24.4.2.2</a> wide string miscellaneous functions, <a href="#7.24.4.6">7.24.4.6</a>
25110 wcspbrk function, <a href="#7.24.4.5.3">7.24.4.5.3</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
25111 wcsrchr function, <a href="#7.24.4.5.4">7.24.4.5.4</a> <a href="#7.24.4.1">7.24.4.1</a>
25112 wcsrtombs function, <a href="#7.24.6.4.2">7.24.6.4.2</a> wide string search functions, <a href="#7.24.4.5">7.24.4.5</a>
25113 wcsspn function, <a href="#7.24.4.5.5">7.24.4.5.5</a> wide-oriented stream, <a href="#7.19.2">7.19.2</a>
25114 wcsstr function, <a href="#7.24.4.5.6">7.24.4.5.6</a> width, <a href="#6.2.6.2">6.2.6.2</a>
25115 wcstod function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a> WINT_MAX macro, <a href="#7.18.3">7.18.3</a>
25116 wcstod function, <a href="#7.24.4.1.1">7.24.4.1.1</a> WINT_MIN macro, <a href="#7.18.3">7.18.3</a>
25117 wcstof function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wint_t type, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>,
25118 wcstoimax function, <a href="#7.8.2.4">7.8.2.4</a> <a href="#7.25.1">7.25.1</a>
25119 wcstok function, <a href="#7.24.4.5.7">7.24.4.5.7</a> wmemchr function, <a href="#7.24.4.5.8">7.24.4.5.8</a>
25120 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wmemcmp function, <a href="#7.24.4.4.5">7.24.4.4.5</a>
25121 <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemcpy function, <a href="#7.24.4.2.3">7.24.4.2.3</a>
25122 wcstold function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wmemmove function, <a href="#7.24.4.2.4">7.24.4.2.4</a>
25123 wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemset function, <a href="#7.24.4.6.2">7.24.4.6.2</a>
25124 wcstombs function, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.4">7.24.6.4</a> wprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.11">7.24.2.11</a>
25125 wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
25126 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.3.10">7.24.3.10</a>
25127 wcstoull function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>
25128 wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a> xor macro, <a href="#7.9">7.9</a>
25129 wcsxfrm function, <a href="#7.24.4.4.4">7.24.4.4.4</a> xor_eq macro, <a href="#7.9">7.9</a>
25130 wctob function, <a href="#7.24.6.1.2">7.24.6.1.2</a>, <a href="#7.25.2.1">7.25.2.1</a>
25131 wctomb function, <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.3">7.24.6.3</a>
25132 wctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
25133 wctrans_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
25134 wctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>