Re: GCC optimizes integer overflow: bug or feature?

[Rask Ingemann Lambertsen]

On Fri, Dec 22, 2006 at 01:58:39AM +0100, Denis Vlasenko wrote:
> 
> Or this, absolutely typical C code. i386 arch can compare
> 16 bits at a time here (luckily, no alighment worries on this arch):
> 
> # cat tt.c
> int f(char *p)
> {
>     if (p[0] == 1 && p[1] == 2) return 1;
>     return 0;
> }

   No, because you'd read past the end of the array:

#include <stdlib.h>

int main (int argc, char *argv[])
{
  char *a;
  if ((a == malloc (sizeof (char))))
    {
      int r;

      a[0] = 1;
      r = f (a);
      free (a);
      return (r);
    }
  return (0);
}

-- 
Rask Ingemann Lambertsen