On Fri, Jul 30, 2021 at 01:10:33AM -0400, Jason Merrill wrote:
> On 7/29/21 10:21 AM, Jakub Jelinek wrote:
> > On Thu, Jul 29, 2021 at 09:50:10AM +0200, Jakub Jelinek via Gcc-patches
> > wrote:
> > > Now that I'm writing the above text and rereading the
> > > pointer-interconvertibility definition, I think my
> > > first_nonstatic_data_member_p
> > > and fold_builtin_is_pointer_inverconvertible_with_class have one bug,
> > > for unions the pointer inter-convertibility doesn't talk about std layout
> > > at
> > > all, so I think I need to check for std_layout_type_p only for non-union
> > > class types and accept any union, std_layout_type_p or not. But when
> > > recursing from a union type into anonymous structure type punt if the
> > > anonymous structure type is not std_layout_type_p + add testcase coverage.
> >
> > For this part, here is an incremental fix. Tested on x86_64-linux.
> >
> > It also shows that in the case (we're beyond the standard in this case
> > because anonymous structures are not in the standard) of union with
> > non-std-layout anonymous structure in it, in the case in the testcases like:
> > struct D {};
> > struct E { [[no_unique_address]] D e; };
> > union Y { int a; struct : public E { short b; long c; }; long long d; };
>
> We don't already reject an anonymous struct with bases? I think we should
> do so, in fixup_anonymous_aggr. We might even require anonymous structs to
> be standard-layout.
Apparently not, the above is accepted. I was looking for an example of
non-stdlayout anon aggregate in union and my first try (mixing
private/public members) has been rejected.
> I'm inclined not to handle this extension case specifically.
You mean not to even recurse into anonymous structures in the function,
or something else?
Jakub
