[PATCH] libstdc++: Add std::inplace_vector for C++26 (P0843R14) [PR119137]

[Tomasz Kaminski]

On Thu, Jul 17, 2025 at 3:41 PM Jakub Jelinek <jakub@redhat.com> wrote:

> On Thu, Jul 17, 2025 at 03:31:57PM +0200, Tomasz Kamiński wrote:
> > From: Jonathan Wakely <jwakely@redhat.com>
> >
> > Implement std::inplace_vector as specified in P0843R14, without follow
> > up papers, in particular P3074R7 (trivial unions). In consequence
>
> I think implementation of that paper is waiting mainly for
> https://wg21.link/cwg2999 resolution.
>
Yes, I have worked with Bary on handling that:
https://brevzin.github.io/cpp_proposals/3726_union_lifetime/p3726r0.html.
But inplace_vector as implemented in the patch is still usable at runtime,
and despite my initial concern, we can implement
the partial compile time support, without pessimizing runtime.

Would you be interested in looking at:
> However, we still have one -Waggressive-loop-optimizations (to best of our
> knowledge false-positive warning produced in cons/from_range.cc and
> cons/throws.cc. Currently it is pruned using dg-prune-output and tracked
by
> PR121143.


>         Jakub
>
>
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