int
main(void) {
  int p=0, e=0;
  int a = 0;

  a = &p - &e;
  printf("p = %p\n", &p);
  printf("e = %p\n", &e);
  a = &p - &e;
  printf("a = %d\n", a);
  a = (long)&p - (long)&e;
  printf("a = %d\n", a);
}

p = 0xbf6ad954
e = 0xbf6ad950
a = 1
a = 4
 Exited: ExitFailure 6