1extern double sqrt (double); 2extern void abort (void); 3int once; 4 5double foo (void) 6{ 7 if (once++) 8 abort (); 9 return 0.0 / 0.0; 10} 11 12double x; 13int main (void) 14{ 15 x = sqrt (foo ()); 16 return 0; 17} 18