From: Jason Merrill <jason@redhat.com>
To: Nikolas Klauser <nikolasklauser@berlin.de>
Cc: gcc@gcc.gnu.org, Louis Dionne <ldionne.2@gmail.com>,
Mark de Wever <koraq@xs4all.nl>,
aaron@aaronballman.com, "libstdc++" <libstdc++@gcc.gnu.org>
Subject: Re: GCC support for extensions from later standards
Date: Sun, 6 Aug 2023 12:19:44 -0700 [thread overview]
Message-ID: <CADzB+2mGjdH6xDnJq+So4h2+56SQsNjFDmRVid9dCZ0evieE-g@mail.gmail.com> (raw)
In-Reply-To: <3A4C9996-750B-4E3F-8F30-E3DA4366C7B5@berlin.de>
[-- Attachment #1: Type: text/plain, Size: 1845 bytes --]
On Wed, Aug 2, 2023 at 12:02 PM Nikolas Klauser <nikolasklauser@berlin.de>
wrote:
> Hi everyone!
>
> I'm working on libc++ and we are currently discussing using language
> extensions from later standards (
> https://discourse.llvm.org/t/rfc-use-language-extensions-from-future-standards-in-libc/71898/4).
> By that I mean things like using `if constexpr` with `-std=c++11`. GCC has
> quite a lot of these kinds of conforming extensions, but doesn't document
> them AFAICT. While discussing using these extensions, the question came up
> what GCCs support policy for these is. Aaron was kind enough to answer
> these questions for us on the Clang side. Since I couldn't find anything in
> the documentation, I thought I'd ask here.
>
> So, here are my questions:
>
> Do you expect that these extensions will ever be removed for some reason?
> If yes, what could those reasons be?
>
Potentially, if they don't actually work properly in earlier standard
modes. I recently noticed that while we allow DMI and =default in C++03
mode with a pedwarn, combining them doesn't work.
Some of the extensions are needed by libstdc++ and are therefore well
tested; these are extremely unlikely to ever be removed. libstdc++ folks,
is there a list of these?
Would you be interested in documenting them?
>
That would be useful, yes.
There is a patch in review to add __has_feature/__has_extension to G++,
which would seem like a suitable context for this documentation.
Aaron noted that we should ask the Clang folks before using them, so they
> can evaluated whether the extension makes sense, since they might not be
> aware of them, and some might be broken. So I'd be interested whether you
> would also like us to ask whether you want to actually support these
> extensions.
>
Sounds good.
Jason
next prev parent reply other threads:[~2023-08-06 19:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-02 19:01 Nikolas Klauser
2023-08-06 19:19 ` Jason Merrill [this message]
2023-08-06 19:43 ` Jonathan Wakely
2023-08-07 13:04 ` Jonathan Wakely
2023-08-08 8:55 ` Jonathan Wakely
2023-08-08 3:03 ` Nikolas Klauser
2023-08-08 7:33 ` Jakub Jelinek
2023-08-08 16:03 ` Nikolas Klauser
2023-08-08 16:07 ` Jonathan Wakely
2023-08-08 16:10 ` Jonathan Wakely
2023-08-08 16:33 ` Nikolas Klauser
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