On Tue, Oct 06, 2020 at 10:47:34AM +0200, Andreas Schwab wrote:
> On Okt 06 2020, Jakub Jelinek via Gcc-patches wrote:
>
> > I mean, we could just use:
> > size_t nbytes = sizeof (irange) + sizeof (tree) * 2 * num_pairs;
> > irange *r = (irange *) obstack_alloc (&m_obstack, nbytes);
> > return new (r) irange ((tree *) (r + 1), num_pairs);
> > without any new type.
>
> Modulo proper alignment.
Sure, but irange's last element is tree * which is pointer to pointer,
and we need here an array of tree, i.e. pointers. So, it would indeed break
on a hypothetical host that has smaller struct X ** alignment than struct X *
alignment. I'm not aware of any.
One could add a static_assert to verify that (that alignof (irange) >= alignof
(tree)
and that sizeof (irange) % alignof (tree) == 0).
Jakub
