gcc/testsuite/gcc.dg/torture/20200311-1.c

   1 /* { dg-do run } */
   2
   3 struct list { struct list *n; };
   4
   5 struct obj {
   6     int n;
   7     struct list l;
   8 } _o;
   9
  10 struct list _l = { .n = &_o.l };
  11
  12 int main(int argc, char *argv[])
  13 {
  14   struct obj *o = &_o;
  15   _o.l.n = &_l;
  16   while (&o->l != &_l)
  17     /* Note the following is invoking undefined behavior but in
  18        this kind of "obvious" cases we don't want to break things
  19        unnecessarily and thus we avoid analyzing o as pointing
  20        to nothing via the undefined pointer subtraction.  Instead
  21        we canonicalize the pointer subtraction followed by the
  22        pointer conversion to pointer offsetting.  */
  23     o = ((struct obj *)((const char *)(o->l.n)
  24                         - (const char *)&((struct obj *)0)->l));
  25   return 0;
  26 }