1  char *a = 0;
       2  char *b = 0;
       3  
       4  g (x)
       5       int x;
       6  {
       7    if ((!!a) != (!!b))
       8      abort ();
       9  }
      10  
      11  f (x)
      12       int x;
      13  {
      14    g (x * x);
      15  }
      16  
      17  main ()
      18  {
      19    f (100);
      20    exit (0);
      21  }