fusl/src/math/copysignf.c

#include <math.h>
#include <stdint.h>

float copysignf(float x, float y) {
  union {
    float f;
    uint32_t i;
  } ux = {x}, uy = {y};
  ux.i &= 0x7fffffff;
  ux.i |= uy.i & 0x80000000;
  return ux.f;
}