1 #include <stdio.h> 2 3 #pragma weak undef_func 4 5 extern int undef_func (void); 6 int (*ptr_to_func)(void) = undef_func; 7 8 int main(void)9 main (void) 10 { 11 if (ptr_to_func == NULL) 12 printf ("PASSED\n"); 13 14 return 0; 15 } 16