<stdint.h>(P) POSIX Programmer's Manual <stdint.h>(P)
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NAMEstdint.h - integer types
SYNOPSIS
#include <stdint.h>
DESCRIPTION
Some of the functionality described on this reference page extends the
ISO C standard. Applications shall define the appropriate feature test
macro (see the System Interfaces volume of IEEE Std 1003.1-2001, Sec‐
tion 2.2, The Compilation Environment) to enable the visibility of
these symbols in this header.
The <stdint.h> header shall declare sets of integer types having speci‐
fied widths, and shall define corresponding sets of macros. It shall
also define macros that specify limits of integer types corresponding
to types defined in other standard headers.
Note: The "width" of an integer type is the number of bits used to
store its value in a pure binary system; the actual type may use
more bits than that (for example, a 28-bit type could be stored
in 32 bits of actual storage). An N-bit signed type has values
in the range -2**N-1 or 1-2**N-1 to 2**N-1-1, while an N-bit
unsigned type has values in the range 0 to 2**N-1.
Types are defined in the following categories:
* Integer types having certain exact widths
* Integer types having at least certain specified widths
* Fastest integer types having at least certain specified widths
* Integer types wide enough to hold pointers to objects
* Integer types having greatest width
(Some of these types may denote the same type.)
Corresponding macros specify limits of the declared types and construct
suitable constants.
For each type described herein that the implementation provides, the
<stdint.h> header shall declare that typedef name and define the asso‐
ciated macros. Conversely, for each type described herein that the
implementation does not provide, the <stdint.h> header shall not
declare that typedef name, nor shall it define the associated macros.
An implementation shall provide those types described as required, but
need not provide any of the others (described as optional).
Integer Types
When typedef names differing only in the absence or presence of the
initial u are defined, they shall denote corresponding signed and
unsigned types as described in the ISO/IEC 9899:1999 standard, Section
6.2.5; an implementation providing one of these corresponding types
shall also provide the other.
In the following descriptions, the symbol N represents an unsigned dec‐
imal integer with no leading zeros (for example, 8 or 24, but not 04 or
048).
* Exact-width integer types
The typedef name int N _t designates a signed integer type with width
N, no padding bits, and a two's-complement representation. Thus, int8_t
denotes a signed integer type with a width of exactly 8 bits.
The typedef name uint N _t designates an unsigned integer type with
width N. Thus, uint24_t denotes an unsigned integer type with a width
of exactly 24 bits.
The following types are required:
int8_t
int16_t
int32_t
uint8_t
uint16_t
uint32_t
If an implementation provides integer types with width 64 that meet
these requirements, then the following types are required: int64_t
uint64_t
In particular, this will be the case if any of the following are true:
* The implementation supports the _POSIX_V6_ILP32_OFFBIG pro‐
gramming environment and the application is being built in
the _POSIX_V6_ILP32_OFFBIG programming environment (see the
Shell and Utilities volume of IEEE Std 1003.1-2001, c99, Pro‐
gramming Environments).
* The implementation supports the _POSIX_V6_LP64_OFF64 program‐
ming environment and the application is being built in the
_POSIX_V6_LP64_OFF64 programming environment.
* The implementation supports the _POSIX_V6_LPBIG_OFFBIG pro‐
gramming environment and the application is being built in
the _POSIX_V6_LPBIG_OFFBIG programming environment.
All other types of this form are optional.
* Minimum-width integer types
The typedef name int_least N _t designates a signed integer type with a
width of at least N, such that no signed integer type with lesser size
has at least the specified width. Thus, int_least32_t denotes a signed
integer type with a width of at least 32 bits.
The typedef name uint_least N _t designates an unsigned integer type
with a width of at least N, such that no unsigned integer type with
lesser size has at least the specified width. Thus, uint_least16_t
denotes an unsigned integer type with a width of at least 16 bits.
The following types are required: int_least8_t int_least16_t
int_least32_t int_least64_t uint_least8_t uint_least16_t uint_least32_t
uint_least64_t
All other types of this form are optional.
* Fastest minimum-width integer types
Each of the following types designates an integer type that is usually
fastest to operate with among all integer types that have at least the
specified width.
The designated type is not guaranteed to be fastest for all purposes;
if the implementation has no clear grounds for choosing one type over
another, it will simply pick some integer type satisfying the signed‐
ness and width requirements.
The typedef name int_fast N _t designates the fastest signed integer
type with a width of at least N. The typedef name uint_fast N _t desig‐
nates the fastest unsigned integer type with a width of at least N.
The following types are required: int_fast8_t int_fast16_t int_fast32_t
int_fast64_t uint_fast8_t uint_fast16_t uint_fast32_t uint_fast64_t
All other types of this form are optional.
* Integer types capable of holding object pointers
The following type designates a signed integer type with the property
that any valid pointer to void can be converted to this type, then con‐
verted back to a pointer to void, and the result will compare equal to
the original pointer: intptr_t
The following type designates an unsigned integer type with the prop‐
erty that any valid pointer to void can be converted to this type, then
converted back to a pointer to void, and the result will compare equal
to the original pointer: uintptr_t
On XSI-conformant systems, the intptr_t and uintptr_t types are
required; otherwise, they are optional.
* Greatest-width integer types
The following type designates a signed integer type capable of repre‐
senting any value of any signed integer type: intmax_t
The following type designates an unsigned integer type capable of rep‐
resenting any value of any unsigned integer type: uintmax_t
These types are required.
Note: Applications can test for optional types by using the corre‐
sponding limit macro from Limits of Specified-Width Integer
Types .
Limits of Specified-Width Integer Types
The following macros specify the minimum and maximum limits of the
types declared in the <stdint.h> header. Each macro name corresponds to
a similar type name in Integer Types .
Each instance of any defined macro shall be replaced by a constant
expression suitable for use in #if preprocessing directives, and this
expression shall have the same type as would an expression that is an
object of the corresponding type converted according to the integer
promotions. Its implementation-defined value shall be equal to or
greater in magnitude (absolute value) than the corresponding value
given below, with the same sign, except where stated to be exactly the
given value.
* Limits of exact-width integer types
* Minimum values of exact-width signed integer types:
{INTN_MIN}
Exactly -(2 **N-1)
* Maximum values of exact-width signed integer types:
{INTN_MAX}
Exactly 2**N-1 -1
* Maximum values of exact-width unsigned integer types:
{UINTN_MAX}
Exactly 2 **N -1
* Limits of minimum-width integer types
* Minimum values of minimum-width signed integer types:
{INT_LEASTN_MIN}
-(2 ** N-1 -1)
* Maximum values of minimum-width signed integer types:
{INT_LEASTN_MAX}
2 ** N-1 -1
* Maximum values of minimum-width unsigned integer types:
{UINT_LEASTN_MAX}
2 ** N -1
* Limits of fastest minimum-width integer types
* Minimum values of fastest minimum-width signed integer types:
{INT_FASTN_MIN}
-(2 ** N-1 -1)
* Maximum values of fastest minimum-width signed integer types:
{INT_FASTN_MAX}
2 ** N-1 -1
* Maximum values of fastest minimum-width unsigned integer types:
{UINT_FASTN_MAX}
2 ** N -1
* Limits of integer types capable of holding object pointers
* Minimum value of pointer-holding signed integer type:
{INTPTR_MIN}
-(2 ** 15 -1)
* Maximum value of pointer-holding signed integer type:
{INTPTR_MAX}
2 ** 15 -1
* Maximum value of pointer-holding unsigned integer type:
{UINTPTR_MAX}
2 ** 16 -1
* Limits of greatest-width integer types
* Minimum value of greatest-width signed integer type:
{INTMAX_MIN}
-(2 ** 63 -1)
* Maximum value of greatest-width signed integer type:
{INTMAX_MAX}
2 ** 63 -1
* Maximum value of greatest-width unsigned integer type:
{UINTMAX_MAX}
2 ** 64 -1
Limits of Other Integer Types
The following macros specify the minimum and maximum limits of integer
types corresponding to types defined in other standard headers.
Each instance of these macros shall be replaced by a constant expres‐
sion suitable for use in #if preprocessing directives, and this expres‐
sion shall have the same type as would an expression that is an object
of the corresponding type converted according to the integer promo‐
tions. Its implementation-defined value shall be equal to or greater in
magnitude (absolute value) than the corresponding value given below,
with the same sign.
* Limits of ptrdiff_t:
{PTRDIFF_MIN}
-65535
{PTRDIFF_MAX}
+65535
* Limits of sig_atomic_t:
{SIG_ATOMIC_MIN}
See below.
{SIG_ATOMIC_MAX}
See below.
* Limit of size_t:
{SIZE_MAX}
65535
* Limits of wchar_t:
{WCHAR_MIN}
See below.
{WCHAR_MAX}
See below.
* Limits of wint_t:
{WINT_MIN}
See below.
{WINT_MAX}
See below.
If sig_atomic_t (see the <signal.h> header) is defined as a signed
integer type, the value of {SIG_ATOMIC_MIN} shall be no greater than
-127 and the value of {SIG_ATOMIC_MAX} shall be no less than 127; oth‐
erwise, sig_atomic_t shall be defined as an unsigned integer type, and
the value of {SIG_ATOMIC_MIN} shall be 0 and the value of
{SIG_ATOMIC_MAX} shall be no less than 255.
If wchar_t (see the <stddef.h> header) is defined as a signed integer
type, the value of {WCHAR_MIN} shall be no greater than -127 and the
value of {WCHAR_MAX} shall be no less than 127; otherwise, wchar_t
shall be defined as an unsigned integer type, and the value of
{WCHAR_MIN} shall be 0 and the value of {WCHAR_MAX} shall be no less
than 255.
If wint_t (see the <wchar.h> header) is defined as a signed integer
type, the value of {WINT_MIN} shall be no greater than -32767 and the
value of {WINT_MAX} shall be no less than 32767; otherwise, wint_t
shall be defined as an unsigned integer type, and the value of
{WINT_MIN} shall be 0 and the value of {WINT_MAX} shall be no less than
65535.
Macros for Integer Constant Expressions
The following macros expand to integer constant expressions suitable
for initializing objects that have integer types corresponding to types
defined in the <stdint.h> header. Each macro name corresponds to a sim‐
ilar type name listed under Minimum-width integer types and Greatest-
width integer types.
Each invocation of one of these macros shall expand to an integer con‐
stant expression suitable for use in #if preprocessing directives. The
type of the expression shall have the same type as would an expression
that is an object of the corresponding type converted according to the
integer promotions. The value of the expression shall be that of the
argument.
The argument in any instance of these macros shall be a decimal, octal,
or hexadecimal constant with a value that does not exceed the limits
for the corresponding type.
* Macros for minimum-width integer constant expressions
The macro INTN_C( value) shall expand to an integer constant expression
corresponding to the type int_least N _t. The macro UINTN_C( value)
shall expand to an integer constant expression corresponding to the
type uint_least N _t. For example, if uint_least64_t is a name for the
type unsigned long long, then UINT64_C(0x123) might expand to the inte‐
ger constant 0x123ULL.
* Macros for greatest-width integer constant expressions
The following macro expands to an integer constant expression having
the value specified by its argument and the type intmax_t: INT‐
MAX_C(value)
The following macro expands to an integer constant expression having
the value specified by its argument and the type uintmax_t: UINT‐
MAX_C(value)
The following sections are informative.
APPLICATION USAGE
None.
RATIONALE
The <stdint.h> header is a subset of the <inttypes.h> header more suit‐
able for use in freestanding environments, which might not support the
formatted I/O functions. In some environments, if the formatted conver‐
sion support is not wanted, using this header instead of the <int‐
types.h> header avoids defining such a large number of macros.
As a consequence of adding int8_t, the following are true:
* A byte is exactly 8 bits.
* {CHAR_BIT} has the value 8, {SCHAR_MAX} has the value 127,
{SCHAR_MIN} has the value -127 or -128, and {UCHAR_MAX} has the
value 255.
FUTURE DIRECTIONS
typedef names beginning with int or uint and ending with _t may be
added to the types defined in the <stdint.h> header. Macro names begin‐
ning with INT or UINT and ending with _MAX, _MIN, or _C may be added to
the macros defined in the <stdint.h> header.
SEE ALSO
<inttypes.h> , <signal.h> , <stddef.h> , <wchar.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 <stdint.h>(P)
