On Mon, Jan 28, 2019 at 01:55:38PM +0100, Richard Biener wrote:
> So I guess in the end we're being lucky. Somehow. I've played with
>
> __attribute__((noipa)) void
> qux ()
> {
> S buf1;
> foo ((char *)&buf1);
> S *p = new (&buf1) (S);
> bar (p);
> p->~S ();
> {
> char buf2[128];
> baz (buf2);
> }
> }
I'd think the above is already invalid, by doing a placement new into
a variable with non-trivial ctor and dtor while it is still constructed,
then destruct the placement new created var in there and after a while
destruct the original variable doesn't feel right to me, but I'm not a C++
language lawyer. I'd expect that usually either the whole var has
char/std::byte etc. array type, or the placement new is into a field inside
of some class (again char/std::byte etc. array type).
Would could be valid is:
__attribute__((noipa)) void
qux ()
{
S buf1;
foo (buf1.buf);
S *p = new (buf1.buf) (S);
bar (p);
p->~S ();
{
char buf2[128];
baz (buf2);
}
}
but we don't really fold that into VAR_DECL lhs either, the type in the
MEM_REF isn't really S even in this case, but CLASSTYPE_AS_BASE of the S
type.
Jakub
