1stdint.h(0P) POSIX Programmer's Manual stdint.h(0P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 stdint.h — integer types
13
15 #include <stdint.h>
16
18 Some of the functionality described on this reference page extends the
19 ISO C standard. Applications shall define the appropriate feature test
20 macro (see the System Interfaces volume of POSIX.1‐2017, Section 2.2,
21 The Compilation Environment) to enable the visibility of these symbols
22 in this header.
23 The <stdint.h> header shall declare sets of integer types having speci‐
25 fied widths, and shall define corresponding sets of macros. It shall
26 also define macros that specify limits of integer types corresponding
27 to types defined in other standard headers.
28 Note: The ``width'' of an integer type is the number of bits used
30 to store its value in a pure binary system; the actual type
31 may use more bits than that (for example, a 28-bit type could
32 be stored in 32 bits of actual storage). An N-bit signed type
33 has values in the range -2N-1 or 1-2N-1 to 2N-1-1, while an
34 N-bit unsigned type has values in the range 0 to 2N-1.
35 Types are defined in the following categories:
37 * Integer types having certain exact widths
39 * Integer types having at least certain specified widths
41 * Fastest integer types having at least certain specified widths
43 * Integer types wide enough to hold pointers to objects
45 * Integer types having greatest width
47 (Some of these types may denote the same type.)
49 Corresponding macros specify limits of the declared types and construct
51 suitable constants.
52 For each type described herein that the implementation provides, the
54 <stdint.h> header shall declare that typedef name and define the asso‐
55 ciated macros. Conversely, for each type described herein that the
56 implementation does not provide, the <stdint.h> header shall not
57 declare that typedef name, nor shall it define the associated macros.
58 An implementation shall provide those types described as required, but
59 need not provide any of the others (described as optional).
60 Integer Types
62 When typedef names differing only in the absence or presence of the
63 initial u are defined, they shall denote corresponding signed and
64 unsigned types as described in the ISO/IEC 9899:1999 standard, Section
65 6.2.5; an implementation providing one of these corresponding types
66 shall also provide the other.
67 In the following descriptions, the symbol N represents an unsigned dec‐
69 imal integer with no leading zeros (for example, 8 or 24, but not 04 or
70 048).
71 * Exact-width integer types
73 The typedef name intN_t designates a signed integer type with width
75 N, no padding bits, and a two's-complement representation. Thus,
76 int8_t denotes a signed integer type with a width of exactly 8
77 bits.
78 The typedef name uintN_t designates an unsigned integer type with
80 width N. Thus, uint24_t denotes an unsigned integer type with a
81 width of exactly 24 bits.
82 The following types are required:
84 int8_t
86 int16_t
87 int32_t
88 uint8_t
89 uint16_t
90 uint32_t
91 If an implementation provides integer types with width 64 that meet
93 these requirements, then the following types are required: int64_t
94 uint64_t
95 In particular, this will be the case if any of the following are
97 true:
98 -- The implementation supports the _POSIX_V7_ILP32_OFFBIG program‐
100 ming environment and the application is being built in the
101 _POSIX_V7_ILP32_OFFBIG programming environment (see the Shell
102 and Utilities volume of POSIX.1‐2017, c99, Programming Environ‐
103 ments).
104 -- The implementation supports the _POSIX_V7_LP64_OFF64 program‐
106 ming environment and the application is being built in the
107 _POSIX_V7_LP64_OFF64 programming environment.
108 -- The implementation supports the _POSIX_V7_LPBIG_OFFBIG program‐
110 ming environment and the application is being built in the
111 _POSIX_V7_LPBIG_OFFBIG programming environment.
112 All other types of this form are optional.
114 * Minimum-width integer types
116 The typedef name int_leastN_t designates a signed integer type with
118 a width of at least N, such that no signed integer type with lesser
119 size has at least the specified width. Thus, int_least32_t denotes
120 a signed integer type with a width of at least 32 bits.
121 The typedef name uint_leastN_t designates an unsigned integer type
123 with a width of at least N, such that no unsigned integer type with
124 lesser size has at least the specified width. Thus, uint_least16_t
125 denotes an unsigned integer type with a width of at least 16 bits.
126 The following types are required: int_least8_t int_least16_t
128 int_least32_t int_least64_t uint_least8_t uint_least16_t
129 uint_least32_t uint_least64_t
130 All other types of this form are optional.
132 * Fastest minimum-width integer types
134 Each of the following types designates an integer type that is usu‐
136 ally fastest to operate with among all integer types that have at
137 least the specified width.
138 The designated type is not guaranteed to be fastest for all pur‐
140 poses; if the implementation has no clear grounds for choosing one
141 type over another, it will simply pick some integer type satisfying
142 the signedness and width requirements.
143 The typedef name int_fastN_t designates the fastest signed integer
145 type with a width of at least N. The typedef name uint_fastN_t
146 designates the fastest unsigned integer type with a width of at
147 least N.
148 The following types are required: int_fast8_t int_fast16_t
150 int_fast32_t int_fast64_t uint_fast8_t uint_fast16_t uint_fast32_t
151 uint_fast64_t
152 All other types of this form are optional.
154 * Integer types capable of holding object pointers
156 The following type designates a signed integer type with the prop‐
158 erty that any valid pointer to void can be converted to this type,
159 then converted back to a pointer to void, and the result will com‐
160 pare equal to the original pointer: intptr_t
161 The following type designates an unsigned integer type with the
163 property that any valid pointer to void can be converted to this
164 type, then converted back to a pointer to void, and the result will
165 compare equal to the original pointer: uintptr_t
166 On XSI-conformant systems, the intptr_t and uintptr_t types are
168 required; otherwise, they are optional.
169 * Greatest-width integer types
171 The following type designates a signed integer type capable of rep‐
173 resenting any value of any signed integer type: intmax_t
174 The following type designates an unsigned integer type capable of
176 representing any value of any unsigned integer type: uintmax_t
177 These types are required.
179 Note: Applications can test for optional types by using the corre‐
181 sponding limit macro from Limits of Specified-Width Integer
182 Types.
183 Limits of Specified-Width Integer Types
185 The following macros specify the minimum and maximum limits of the
186 types declared in the <stdint.h> header. Each macro name corresponds to
187 a similar type name in Integer Types.
188 Each instance of any defined macro shall be replaced by a constant
190 expression suitable for use in #if preprocessing directives, and this
191 expression shall have the same type as would an expression that is an
192 object of the corresponding type converted according to the integer
193 promotions. Its implementation-defined value shall be equal to or
194 greater in magnitude (absolute value) than the corresponding value
195 given below, with the same sign, except where stated to be exactly the
196 given value.
197 * Limits of exact-width integer types
199 -- Minimum values of exact-width signed integer types:
201 {INTN_MIN} Exactly -(2^N-1)
203 -- Maximum values of exact-width signed integer types:
205 {INTN_MAX} Exactly 2^N-1 -1
207 -- Maximum values of exact-width unsigned integer types:
209 {UINTN_MAX} Exactly 2^N -1
211 * Limits of minimum-width integer types
213 -- Minimum values of minimum-width signed integer types:
215 {INT_LEASTN_MIN}
217 -(2^N-1 -1)
218 -- Maximum values of minimum-width signed integer types:
220 {INT_LEASTN_MAX}
222 2^N-1 -1
223 -- Maximum values of minimum-width unsigned integer types:
225 {UINT_LEASTN_MAX}
227 2^N -1
228 * Limits of fastest minimum-width integer types
230 -- Minimum values of fastest minimum-width signed integer types:
232 {INT_FASTN_MIN} -(2^N-1 -1)
234 -- Maximum values of fastest minimum-width signed integer types:
236 {INT_FASTN_MAX} 2^N-1 -1
238 -- Maximum values of fastest minimum-width unsigned integer types:
240 {UINT_FASTN_MAX}
242 2^N -1
243 * Limits of integer types capable of holding object pointers
245 -- Minimum value of pointer-holding signed integer type:
247 {INTPTR_MIN} -(2^15 -1)
249 -- Maximum value of pointer-holding signed integer type:
251 {INTPTR_MAX} 2^15 -1
253 -- Maximum value of pointer-holding unsigned integer type:
255 {UINTPTR_MAX} 2^16 -1
257 * Limits of greatest-width integer types
259 -- Minimum value of greatest-width signed integer type:
261 {INTMAX_MIN} -(2^63 -1)
263 -- Maximum value of greatest-width signed integer type:
265 {INTMAX_MAX} 2^63 -1
267 -- Maximum value of greatest-width unsigned integer type:
269 {UINTMAX_MAX} 2^64 -1
271 Limits of Other Integer Types
273 The following macros specify the minimum and maximum limits of integer
274 types corresponding to types defined in other standard headers.
275 Each instance of these macros shall be replaced by a constant expres‐
277 sion suitable for use in #if preprocessing directives, and this expres‐
278 sion shall have the same type as would an expression that is an object
279 of the corresponding type converted according to the integer promo‐
280 tions. Its implementation-defined value shall be equal to or greater in
281 magnitude (absolute value) than the corresponding value given below,
282 with the same sign.
283 * Limits of ptrdiff_t:
285 {PTRDIFF_MIN} -65535
287 {PTRDIFF_MAX} +65535
289 * Limits of sig_atomic_t:
291 {SIG_ATOMIC_MIN}
293 See below.
294 {SIG_ATOMIC_MAX}
296 See below.
297 * Limit of size_t:
299 {SIZE_MAX} 65535
301 * Limits of wchar_t:
303 {WCHAR_MIN} See below.
305 {WCHAR_MAX} See below.
307 * Limits of wint_t:
309 {WINT_MIN} See below.
311 {WINT_MAX} See below.
313 If sig_atomic_t (see the <signal.h> header) is defined as a signed
315 integer type, the value of {SIG_ATOMIC_MIN} shall be no greater than
316 -127 and the value of {SIG_ATOMIC_MAX} shall be no less than 127; oth‐
317 erwise, sig_atomic_t shall be defined as an unsigned integer type, and
318 the value of {SIG_ATOMIC_MIN} shall be 0 and the value of
319 {SIG_ATOMIC_MAX} shall be no less than 255.
320 If wchar_t (see the <stddef.h> header) is defined as a signed integer
322 type, the value of {WCHAR_MIN} shall be no greater than -127 and the
323 value of {WCHAR_MAX} shall be no less than 127; otherwise, wchar_t
324 shall be defined as an unsigned integer type, and the value of
325 {WCHAR_MIN} shall be 0 and the value of {WCHAR_MAX} shall be no less
326 than 255.
327 If wint_t (see the <wchar.h> header) is defined as a signed integer
329 type, the value of {WINT_MIN} shall be no greater than -32767 and the
330 value of {WINT_MAX} shall be no less than 32767; otherwise, wint_t
331 shall be defined as an unsigned integer type, and the value of
332 {WINT_MIN} shall be 0 and the value of {WINT_MAX} shall be no less than
333 65535.
334 Macros for Integer Constant Expressions
336 The following macros expand to integer constant expressions suitable
337 for initializing objects that have integer types corresponding to types
338 defined in the <stdint.h> header. Each macro name corresponds to a sim‐
339 ilar type name listed under Minimum-width integer types and Greatest-
340 width integer types.
341 Each invocation of one of these macros shall expand to an integer con‐
343 stant expression suitable for use in #if preprocessing directives. The
344 type of the expression shall have the same type as would an expression
345 that is an object of the corresponding type converted according to the
346 integer promotions. The value of the expression shall be that of the
347 argument.
348 The argument in any instance of these macros shall be an unsuffixed
350 integer constant with a value that does not exceed the limits for the
351 corresponding type.
352 * Macros for minimum-width integer constant expressions
354 The macro INTN_C(value) shall expand to an integer constant expres‐
356 sion corresponding to the type int_leastN_t. The macro
357 UINTN_C(value) shall expand to an integer constant expression cor‐
358 responding to the type uint_leastN_t. For example, if
359 uint_least64_t is a name for the type unsigned long long, then
360 UINT64_C(0x123) might expand to the integer constant 0x123ULL.
361 * Macros for greatest-width integer constant expressions
363 The following macro expands to an integer constant expression hav‐
365 ing the value specified by its argument and the type intmax_t: INT‐
366 MAX_C(value)
367 The following macro expands to an integer constant expression hav‐
369 ing the value specified by its argument and the type uintmax_t:
370 UINTMAX_C(value)
371 The following sections are informative.
373
375 None.
376
378 The <stdint.h> header is a subset of the <inttypes.h> header more suit‐
379 able for use in freestanding environments, which might not support the
380 formatted I/O functions. In some environments, if the formatted conver‐
381 sion support is not wanted, using this header instead of the <int‐
382 types.h> header avoids defining such a large number of macros.
383 As a consequence of adding int8_t, the following are true:
385 * A byte is exactly 8 bits.
387 * {CHAR_BIT} has the value 8, {SCHAR_MAX} has the value 127,
389 {SCHAR_MIN} has the value -128, and {UCHAR_MAX} has the value 255.
390 (The POSIX standard explicitly requires 8-bit char and two's-complement
392 arithmetic.)
393
395 typedef names beginning with int or uint and ending with _t may be
396 added to the types defined in the <stdint.h> header. Macro names begin‐
397 ning with INT or UINT and ending with _MAX, _MIN, or _C may be added to
398 the macros defined in the <stdint.h> header.
399
401 <inttypes.h>, <signal.h>, <stddef.h>, <wchar.h>
402 The System Interfaces volume of POSIX.1‐2017, Section 2.2, The Compila‐
404 tion Environment
405
407 Portions of this text are reprinted and reproduced in electronic form
408 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
409 table Operating System Interface (POSIX), The Open Group Base Specifi‐
410 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
411 Electrical and Electronics Engineers, Inc and The Open Group. In the
412 event of any discrepancy between this version and the original IEEE and
413 The Open Group Standard, the original IEEE and The Open Group Standard
414 is the referee document. The original Standard can be obtained online
415 at http://www.opengroup.org/unix/online.html .
416 Any typographical or formatting errors that appear in this page are
418 most likely to have been introduced during the conversion of the source
419 files to man page format. To report such errors, see https://www.ker‐
420 nel.org/doc/man-pages/reporting_bugs.html .
421IEEE/The Open Group 2017 stdint.h(0P)