[Bug middle-end/29272] [4.2 Regression] memcpy optimization causes wrong-code

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2006-09-29 22:04 -------
Is:
extern void abort (void);

struct S { struct S *s; } s;
struct T { struct T *t; } t;

static inline void
foo (void *s)
{
  struct T *p = s;
  __builtin_memcpy (&p->t, &t.t, sizeof (t.t));
}

void *
__attribute__((noinline))
bar (void *p, struct S *q)
{
  q->s = &s;
  foo (p);
  return q->s;
}

int
main (void)
{
  t.t = &t;
  if (bar (&s, &s) != (void *) &t)
    abort ();
  return 0;
}

valid?  I'd say yes, we either access s.s using its declared (== effective)
type,
or through memcpy (which is supposed tobe a char array access and therefore
ok wrt. aliasing).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29272