1 char *a = 0; 2 char *b = 0; 3 g(x)4 g (x) 5 int x; 6 { 7 if ((!!a) != (!!b)) 8 abort (); 9 } 10 f(x)11 f (x) 12 int x; 13 { 14 g (x * x); 15 } 16 main()17 main () 18 { 19 f (100); 20 exit (0); 21 } 22