__STDC_ENDIAN_LITTLE, STDC_ENDIAN_BIG, STDC_ENDIAN_NATIVE__

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Numerics

Common mathematical functions
Floating-point environment(C99)
Pseudo-random number generation
Complex number arithmetic(C99)
Type-generic math(C99)
Bit manipulation(C23)
Checked integer arithmetic(C23)

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Bit manipulation

Functions
stdc_leading_zeros (C23)
stdc_leading_ones (C23)
stdc_trailing_zeros (C23)
stdc_trailing_ones (C23)
stdc_first_leading_zero (C23)
stdc_first_leading_one (C23)
stdc_first_trailing_zero (C23)
stdc_first_trailing_one (C23)
stdc_count_zeros (C23)
stdc_count_ones (C23)
stdc_has_single_bit (C23)
stdc_bit_width (C23)
stdc_bit_floor (C23)
stdc_bit_ceil (C23)
Macro constants
__STDC_ENDIAN_LITTLE__ __STDC_ENDIAN_BIG__ __STDC_ENDIAN_NATIVE__ (C23)(C23)(C23)

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Defined in header`<stdbit.h>`
#define __STDC_ENDIAN_LITTLE__ /* implementation-defined */	(1)	(since C23)
#define __STDC_ENDIAN_BIG__ /* implementation-defined */	(2)	(since C23)
#define __STDC_ENDIAN_NATIVE__ /* implementation-defined */	(3)	(since C23)

Indicates theendianness of allscalar types:

If all scalar types are little-endian,__STDC_ENDIAN_NATIVE__ equals__STDC_ENDIAN_LITTLE__.
If all scalar types are big-endian,__STDC_ENDIAN_NATIVE__ equals__STDC_ENDIAN_BIG__.
If the platform uses neither little-endian nor big-endian,__STDC_ENDIAN_NATIVE__ equals neither__STDC_ENDIAN_BIG__ nor__STDC_ENDIAN_LITTLE__.
The values of the integer constant expressions for__STDC_ENDIAN_BIG__ and__STDC_ENDIAN_LITTLE__ are not equal.

[edit]Example

Run this code

#include <stdbit.h>#include <stdio.h> int main(){switch(__STDC_ENDIAN_NATIVE__){case __STDC_ENDIAN_LITTLE__:printf("__STDC_ENDIAN_LITTLE__\n");break;case __STDC_ENDIAN_BIG__:printf("__STDC_ENDIAN_BIG__\n");break;default:printf("mixed-endian\n");}return __STDC_ENDIAN_NATIVE__;}