20000503-1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

unsigned long
sub (int a)
{
  return ((0 > a - 2) ? 0 : a - 2) * sizeof (long);
}

main ()
{
  if (sub (0) != 0)
    abort ();

  exit (0);
}