[PATCH] [11/12/13/14 Regression] ABI break in _Hash_node_value_base since GCC 11 [PR 111050]

[Jonathan Wakely]

On Mon, 11 Sept 2023 at 18:19, François Dumont <frs.dumont@gmail.com> wrote:
>
>
> On 11/09/2023 13:51, Jonathan Wakely wrote:
> > On Sun, 10 Sept 2023 at 14:57, François Dumont via Libstdc++
> > <libstdc++@gcc.gnu.org> wrote:
> >> Following confirmation of the fix by TC here is the patch where I'm
> >> simply adding a 'constexpr' on _M_next().
> >>
> >> Please let me know this ChangeLog entry is correct. I would prefer this
> >> patch to be assigned to 'TC' with me as co-author but I don't know how
> >> to do such a thing. Unless I need to change my user git identity to do so ?
> > Sam already explained that, but please check with Tim how he wants to
> > be credited, if at all. He doesn't have a copyright assignment, and
> > hasn't added a DCO sign-off to the patch, but it's small enough to not
> > need it as this is the first contribution credited to him.
> >
> >
> >>       libstdc++: Add constexpr qualification to _Hash_node::_M_next()
> > What has this constexpr addition got to do with the ABI change and the
> > always_inline attributes?
> >
> > It certainly doesn't seem like it should be the summary line of the
> > git commit message.
>
> Oops, sorry, that's what I had started to do before Tim submitted anything.
>
> Here is latest version:

No patch attached, and the ChangeLog below still mentions the constexpr.

I've pinged Tim via another channel to ask him about the author attribution.


>
> Author: TC <rs2740@gmail.com>
> Date:   Wed Sep 6 19:31:55 2023 +0200
>
>      libstdc++: Force inline on _Hash_node_value_base methods to fix abi
> (PR111050)
>
> https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=1b6f0476837205932613ddb2b3429a55c26c409d
>      changed _Hash_node_value_base to no longer derive from
> _Hash_node_base, which means
>      that its member functions expect _M_storage to be at a different
> offset. So explosions
>      result if an out-of-line definition is emitted for any of the
> member functions (say,
>      in a non-optimized build) and the resulting object file is then
> linked with code built
>      using older version of GCC/libstdc++.
>
>      libstdc++-v3/ChangeLog:
>
>              PR libstdc++/111050
>              * include/bits/hashtable_policy.h
>              (_Hash_node_value_base<>::_M_valptr(),
> _Hash_node_value_base<>::_M_v())
>              Add [[__gnu__::__always_inline__]].
>              (_Hash_node<>::_M_next()): Add constexpr.
>
>      Co-authored-by: François Dumont <fdumont@gcc.gnu.org>
>
> Ok for you TC (Tim ?) ?
>
>