Fixed width integer types (since C++11)

Types

The implementation may define typedef names intN_t, int_fastN_t, int_leastN_t, uintN_t, uint_fastN_t, and uint_leastN_t when N is not 8, 16, 32 or 64. Typedef names of the form intN_t may only be defined if the implementation supports an integer type of that width with no padding. Thus, std::uint24_t denotes an unsigned integer type with a width of exactly 24 bits.

Each of the macros listed in below is defined if and only if the implementation defines the corresponding typedef name. The macros INTN_C and UINTN_C correspond to the typedef names int_leastN_t and uint_leastN_t, respectively.

Macro constants

Function macros for minimum-width integer constants

#include <cstdint>
UINT64_C(0x123) // expands to a literal of type uint_least64_t and value 0x123

Format macro constants

Format constants for the std::fprintf family of functions

Each of the PRI macros listed here is defined if and only if the implementation defines the corresponding typedef name.

Format constants for the std::fscanf family of functions

Each of the SCN macros listed in here is defined if and only if the implementation defines the corresponding typedef name and has a suitable std::fscanf length modifier for the type.

Notes

Because C++ interprets a character immediately following a string literal as a user-defined string literal, C code such as printf("%"PRId64"\n",n); is invalid C++ and requires a space before PRId64.

The C99 standard suggests that C++ implementations should not define the above limit, constant, or format macros unless the macros __STDC_LIMIT_MACROS, __STDC_CONSTANT_MACROS or __STDC_FORMAT_MACROS (respectively) are defined before including the relevant C header (stdint.h or inttypes.h). This recommendation was not adopted by any C++ standard and was removed in C11. However, some implementations (such as glibc 2.17) try to apply this rule, and it may be necessary to define the __STDC macros; C++ compilers may try to work around this by automatically defining them in some circumstances.

std::int8_t may be signed char and std::uint8_t may be unsigned char, but neither can be char regardless of its signedness (because char is not considered a "signed integer type" or "unsigned integer type").

Example

#include <cstdio>
#include <cinttypes>
 
int main()
{
    std::printf("%zu\n", sizeof(std::int64_t));
    std::printf("%s\n", PRId64);
    std::printf("%+" PRId64 "\n", INT64_MIN);
    std::printf("%+" PRId64 "\n", INT64_MAX);
 
    std::int64_t n = 7;
    std::printf("%+" PRId64 "\n", n);
}

8
lld
-9223372036854775808
+9223372036854775807
+7

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

References

• C++23 standard (ISO/IEC 14882:2023):
• 17.4 Integer types [cstdint]
• 31.13.2 Header <cinttypes> synopsis [cinttypes.syn]
• C++20 standard (ISO/IEC 14882:2020):
• 17.4 Integer types [cstdint]
• 29.12.2 Header <cinttypes> synopsis [cinttypes.syn]
• C++17 standard (ISO/IEC 14882:2017):
• 21.4 Integer types [cstdint]
• 30.11.2 Header <cinttypes> synopsis [cinttypes.syn]
• C++14 standard (ISO/IEC 14882:2014):
• 18.4 Integer types [cstdint]
• 27.9.2 C library files [c.files]
• C++11 standard (ISO/IEC 14882:2011):
• 18.4 Integer types [cstdint]
• 27.9.2 C library files [c.files]

See also

• Fundamental types