Description of problem:
Compiling with -O produces a different result:

$ cat bla.c
#include <stdio.h>

int main() {

  printf( "%d\n", 0 / 0 );

  return 0;
}
$ gcc bla.c
bla.c: In function 'main':
bla.c:5:21: warning: division by zero [-Wdiv-by-zero]
$ ./a.out 
Floating point exception
$ gcc -O bla.c
bla.c: In function 'main':
bla.c:5:21: warning: division by zero [-Wdiv-by-zero]
$ ./a.out 
0

Version-Release number of selected component (if applicable):
gcc version 4.7.0 20120507 (Red Hat 4.7.0-5) (GCC) 

How reproducible:
Always.