1extern void abort(void);
2void foo(int *p)
3{
4  int x;
5  int y;
6  x = *p;
7  *p = 0;
8  y = *p;
9  if (x != y)
10    return;
11  abort ();
12}
13
14int main()
15{
16  int a = 1;
17  foo(&a);
18  return 0;
19}
20