Am Donnerstag, dem 23.05.2024 um 14:30 -0700 schrieb Ian Lance Taylor:
> On Thu, May 23, 2024 at 2:00 PM Joseph Myers <josmy...@redhat.com> wrote:
> >
> > On Tue, 21 May 2024, Martin Uecker wrote:
> > >
> > > C: allow aliasing of compatible types derived from enumeral types
> > > [PR115157]
> > >
> > > Aliasing of enumeral types with the underlying integer is now allowed
> > > by setting the aliasing set to zero. But this does not allow aliasing
> > > of derived types which are compatible as required by ISO C. Instead,
> > > initially set structural equality. Then set TYPE_CANONICAL and update
> > > pointers and main variants when the type is completed (as done for
> > > structures and unions in C23).
> > >
> > > PR 115157
> > >
> > > gcc/c/
> > > * c-decl.cc (shadow_tag-warned,parse_xref_tag,start_enum,
> > > finish_enum): Set SET_TYPE_STRUCTURAL_EQUALITY /
> > > TYPE_CANONICAL.
> > > * c-obj-common.cc (get_alias_set): Remove special case.
> > > (get_aka_type): Add special case.
> > >
> > > gcc/
> > > * godump.cc (go_output_typedef): use TYPE_MAIN_VARIANT instead
> > > of TYPE_CANONICAL.
> > >
> > > gcc/testsuite/
> > > * gcc.dg/enum-alias-1.c: New test.
> > > * gcc.dg/enum-alias-2.c: New test.
> > > * gcc.dg/enum-alias-3.c: New test.
> >
> > OK, in the absence of objections on middle-end or Go grounds within the
> > next week.
>
> The godump.cc patch is
>
> && (TYPE_CANONICAL (TREE_TYPE (decl)) == NULL_TREE
> || !container->decls_seen.contains
> - (TYPE_CANONICAL (TREE_TYPE (decl)))))
> + (TYPE_MAIN_VARIANT (TREE_TYPE (decl)))))
> {
>
> What is the problem you are seeing?
Test failures in godump-1.c
>
> This patch isn't right:
>
> 1) The code is saying if "X == NULL_TREE || !already_seen(X)". This
> patch is changing the latter X but not the former. They should be
> consistent.
Maybe the X == NULL_TREE can be removed if we
add TYPE_MAIN_VARIANTs instead?
>
> 2) At the bottom of that conditional block is code that adds a value
> to container->decls_seen. Today that code is adding TYPE_CANONICAL.
> If we change the condition to test TYPE_MAIN_VARIANT, then we need to
> add TYPE_MAIN_VARIANT to decls_seen.
Yes, obviously this is wrong. Thanks!
Martin
>
> Hope that makes sense.
>
> I don't know why the patch is required, but it's fine with those
> changes as long as the libgo tests continue to pass.
>
> Ian
