New type-based pool allocator code miscompiled due to aliasing issue?
Richard Biener
richard.guenther@gmail.com
Thu Jun 11 19:50:00 GMT 2015
On June 11, 2015 7:50:36 PM GMT+02:00, Jakub Jelinek <jakub@redhat.com> wrote:
>On Fri, Jun 12, 2015 at 12:58:12AM +0800, pinskia@gmail.com wrote:
>> This is just a bug in the older compiler. There was a change to fix
>in
>> placement new operator. I can't find the reference right now but
>this is
>> the same issue as that.
>
>I'm not claiming 4.1 is aliasing bug free, there are various known
>issues in
>it. But, is that the case here?
>
> empty_var = onepart_pool (onepart).allocate ();
> empty_var->dv = dv;
> empty_var->refcount = 1;
> empty_var->n_var_parts = 0;
>
>doesn't really seem to use operator new at all, so I'd say the bug is
>in
>all the spots that call allocate () method of the pool, but don't
>really
>use operator new.
Yeah. BTW, I see the same issue on x86_64 and on ia64 with a gcc 4.1 host compiler. I think allocate itself should use placement new, not just a static pointer conversion.
Richard.
> Jakub
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