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

["François Dumont" <frs.dumont@gmail.com>]

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:

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 ?) ?