static char help[] = "Tests not trapping an underflow\n\n";

#include <petscsys.h>
#include <float.h>
#include <math.h>

/* From https://stackoverflow.com/questions/37193363/float-underflow-in-c-explanation */
void demo(void)
{
  /*
  FLT_MIN, FLT_MIN and the display of the floating point numbers are not portable

  const char *format = "%.10e %a\n";
  printf(format, FLT_MIN, FLT_MIN);
  printf(format, FLT_TRUE_MIN, FLT_TRUE_MIN);
  */

  float f = nextafterf(1.0f, 2.0f);
  do {
    /* if trapping of underflow is turned on then this will generate an exception */
    f /= 2;
    /* printf(format, f, f); */
  } while (f);
}

int main(int argc, char **argv)
{
  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
  demo();
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
     TODO: Doesn't work on AArch64 targets. There's a known hardware limitation. arch-ci-linux-cmplx-single
     args: -fp_trap

TEST*/