stdint.h
Section: POSIX Programmer's Manual (0P)
Updated: 2013
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NAME
stdint.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 POSIX.12008,
Section 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 specified 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 28bit type could be stored in 32 bits of
actual storage). An
Nbit
signed type has values in the range 2N1 or
12N1 to 2N11, while
an
Nbit
unsigned type has values in the range 0 to 2N1.
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 associated 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 decimal integer with no leading zeros (for
example, 8 or 24, but not 04 or 048).
 *

Exactwidth integer types

The
typedef
name
intN_t
designates a signed integer type with width
N,
no padding bits, and a two'scomplement representation. Thus,
int8_t
denotes a signed integer type with a width of exactly 8 bits.
The
typedef
name
uintN_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_V7_ILP32_OFFBIG programming
environment and the application is being built in the
_POSIX_V7_ILP32_OFFBIG programming environment (see the Shell and Utilities volume of POSIX.12008,
c99,
Programming Environments).
 

The implementation supports the _POSIX_V7_LP64_OFF64 programming
environment and the application is being built in the
_POSIX_V7_LP64_OFF64 programming environment.
 

The implementation supports the _POSIX_V7_LPBIG_OFFBIG programming
environment and the application is being built in the
_POSIX_V7_LPBIG_OFFBIG programming environment.
All other types of this form are optional.
 *

Minimumwidth integer types

The
typedef
name
int_leastN_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_leastN_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 minimumwidth 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
signedness and width requirements.
The
typedef
name
int_fastN_t
designates the fastest signed integer type with a width of at least
N.
The
typedef
name
uint_fastN_t
designates 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 converted 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
property 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 XSIconformant systems, the
intptr_t
and
uintptr_t
types are required;
otherwise, they are optional.
 *

Greatestwidth integer types

The following type designates a signed integer type capable of
representing any value of any signed integer type:
intmax_t
The following type designates an unsigned integer type capable of
representing any value of any unsigned integer type:
uintmax_t
These types are required.
 Note:

Applications can test for optional types by using the corresponding
limit macro from
Limits of SpecifiedWidth Integer Types.
Limits of SpecifiedWidth 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
implementationdefined 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 exactwidth integer types

 

Minimum values of exactwidth signed integer types:

 {INTN_MIN}

Exactly ($2"^" N1$)
 

Maximum values of exactwidth signed integer types:

 {INTN_MAX}

Exactly $2"^" N1$ 1
 

Maximum values of exactwidth unsigned integer types:

 {UINTN_MAX}

Exactly $2"^" N$ 1
 *

Limits of minimumwidth integer types

 

Minimum values of minimumwidth signed integer types:

 {INT_LEASTN_MIN}

($2"^" N1$ 1)
 

Maximum values of minimumwidth signed integer types:

 {INT_LEASTN_MAX}

$2"^" N1$ 1
 

Maximum values of minimumwidth unsigned integer types:

 {UINT_LEASTN_MAX}

$2"^" N$ 1
 *

Limits of fastest minimumwidth integer types

 

Minimum values of fastest minimumwidth signed integer types:

 {INT_FASTN_MIN}

($2"^" N1$ 1)
 

Maximum values of fastest minimumwidth signed integer types:

 {INT_FASTN_MAX}

$2"^" N1$ 1
 

Maximum values of fastest minimumwidth unsigned integer types:

 {UINT_FASTN_MAX}

$2"^" N$ 1
 *

Limits of integer types capable of holding object pointers

 

Minimum value of pointerholding signed integer type:

 {INTPTR_MIN}

($2"^" 15$ 1)
 

Maximum value of pointerholding signed integer type:

 {INTPTR_MAX}

$2"^" 15$ 1
 

Maximum value of pointerholding unsigned integer type:

 {UINTPTR_MAX}

$2"^" 16$ 1
 *

Limits of greatestwidth integer types

 

Minimum value of greatestwidth signed integer type:

 {INTMAX_MIN}

($2"^" 63$ 1)
 

Maximum value of greatestwidth signed integer type:

 {INTMAX_MAX}

$2"^" 63$ 1
 

Maximum value of greatestwidth 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
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
implementationdefined 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; otherwise,
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 similar type name listed under
Minimumwidth integer types and
Greatestwidth integer
types.
Each invocation of one of these macros shall expand to an integer
constant 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 an unsuffixed
integer constant with a value that does not exceed the limits for the
corresponding type.
 *

Macros for minimumwidth integer constant expressions

The macro
INTN_C(value)
shall expand to an integer constant expression corresponding to the
type
int_leastN_t.
The macro
UINTN_C(value)
shall expand to an integer constant expression corresponding to the
type
uint_leastN_t.
For example, if
uint_least64_t
is a name for the type
unsigned long long,
then
UINT64_C(0x123)
might expand to the integer constant 0x123ULL.
 *

Macros for greatestwidth integer constant expressions

The following macro expands to an integer constant expression having
the value specified by its argument and the type
intmax_t:
INTMAX_C(value)
The following macro expands to an integer constant expression having
the value specified by its argument and the type
uintmax_t:
UINTMAX_C(value)
The following sections are informative.
APPLICATION USAGE
None.
RATIONALE
The
<stdint.h>
header is a subset of the
<inttypes.h>
header more suitable for use in freestanding environments, which might
not support the formatted I/O functions. In some environments, if the
formatted conversion support is not wanted, using this header instead
of the
<inttypes.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 128, and
{UCHAR_MAX}
has the value 255.
(The POSIX standard explicitly requires 8bit char and
two'scomplement arithmetic.)
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 beginning 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>
The System Interfaces volume of POSIX.12008,
Section 2.2,
The Compilation Environment
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
 Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.12008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/manpages/reporting_bugs.html .
Index
 PROLOG

 NAME

 SYNOPSIS

 DESCRIPTION

 Integer Types

 Limits of SpecifiedWidth Integer Types

 Limits of Other Integer Types

 Macros for Integer Constant Expressions

 APPLICATION USAGE

 RATIONALE

 FUTURE DIRECTIONS

 SEE ALSO

 COPYRIGHT
