1  struct s
       2  {
       3    int a;
       4    int b;
       5    struct s *dummy;
       6  };
       7  
       8  f (struct s *sp)
       9  {
      10    return sp && sp->a == -1 && sp->b == -1;
      11  }
      12  
      13  main ()
      14  {
      15    struct s x;
      16    x.a = x.b = -1;
      17    if (f (&x) == 0)
      18      abort ();
      19    exit (0);
      20  }