ffast-math demo

#include <math.h>
#include <float.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>

__attribute__((noinline))
double nafter(double x) {
   return nextafter(x, INFINITY);
}

int main(void) {
   double dbl = nafter(0.0);
   int64_t i64 = 0;
   memcpy(&i64, &dbl, sizeof i64);
   printf("%lld\n", (long long)i64);
   printf("positive: %d\n", dbl > 0.0);
}