/* TESTED WITH GCC 12.2.0
* 1) By default the compiler assumes exceptions can occur. Compile with:
* 	gcc -O3 -lm test_fpexcept.c
* run ./a.out prints "0 0"
* 
* 2) Now tell the compiler no exceptions will occur, to enable further optimizations. Compile with:
*     gcc -O3 -fno-trapping-math -lm test_fpexcept.c
* run ./a.out generates a spurious exception.
*/


#define _GNU_SOURCE
#include <stdio.h>
#include <fenv.h>


#define N 1000
int l[N];
float l_2[N];

void init(int* x, int n)
{
	for (int i=0; i<n; i++)  x[i] = i*(i+1);
	x[100] = 0;	// add some zeros at random places
	x[30] = 0;
}


int main()
{
	init(l,N);

	// -fno-trapping-math basically tells the compiler (among other things) we will NOT call the following line:
	feenableexcept(FE_DIVBYZERO | FE_INVALID | FE_OVERFLOW);                // turn this on to track NaNs or other floating-point exceptions (requires gcc, #define _GNU_SOURCE and #include <fenv.h>)

	// This loop can be vectorized when compiled with -fno-trapping-math
	for (int i=0; i<N; i++) {
		int ii = l[i];
		l_2[i] = (ii==0) ? 0.0f : 1.0f/ii;            // avoid division by 0 !
	}

	printf("%g %g\n", l_2[30], l_2[100]);		// do something with data to avoid eliminating all code.
}