foo.c

#include <stdio.h>
#include <math.h>

#define BUG_ON_GCC
#ifdef BUG_ON_GCC
__attribute__((noinline))
#else
inline __attribute__((always_inline))
#endif
double safe_pow(
  double x,
  double y)
{
  printf("x = %llx\n", *((unsigned long long *)&x));
  printf("y = %llx\n", *((unsigned long long *)&y));
  double result = pow(x, y);
  printf("r = %llx\n", *((unsigned long long *)&result));
  return result;
}

int main() {
  printf("%ld\n", sizeof(pow(15.034465284692086, 3.466120406090667)));
  printf("%.24f\n", pow(15.034465284692086, 3.466120406090667));
  printf("%ld\n", sizeof(safe_pow(15.034465284692086, 3.466120406090667)));
  printf("%.24f\n", safe_pow(15.034465284692086, 3.466120406090667));
  return 0;
}