<stdbit.h>

<stdbit.h> provides standard bit manipulation (C23): stdc_popcount (population count), stdc_leading_zeros, stdc_trailing_zeros, stdc_rotl, stdc_rotr. Previously you needed GCC builtins or platform-specific code.

Use it for portable bit operations without compiler-specific extensions.

This example demonstrates bit counting and rotation on integers.

// compile: gcc -std=c2x -o stdbitexample stdbitexample.c
// run: ./stdbitexample
// description: bit manipulation functions
 
#include <stdbit.h>
#include <stdio.h>
 
int main() {
    unsigned int x = 0b11010011;
 
    printf("popcount(0b11010011) = %u\n", stdc_popcount(x));
    printf("leading zeros = %u\n", stdc_leading_zeros(x));
    printf("trailing zeros = %u\n", stdc_trailing_zeros(x));
    printf("rotl(x, 2) = 0x%x\n", stdc_rotl(x, 2));
 
    return 0;
}

Bit counting:

• stdc_popcount(x): count set bits (population count)
• stdc_popcount_uc(x), stdc_popcount_us(x), stdc_popcount_ui(x), stdc_popcount_ul(x), stdc_popcount_ull(x): type-specific variants

Leading/trailing zeros:

• stdc_leading_zeros(x): count leading zero bits
• stdc_trailing_zeros(x): count trailing zero bits
• Type-specific variants: _uc, _us, _ui, _ul, _ull

Bit rotation:

• stdc_rotl(x, n): rotate left by n bits
• stdc_rotr(x, n): rotate right by n bits
• Type-specific variants: _uc, _us, _ui, _ul, _ull

Bit flag checks:

• stdc_has_single_bit(x): check if exactly one bit is set (is power of 2)