From: Nikolas Klauser <nikolasklauser@berlin.de>
To: Jason Merrill <jason@redhat.com>
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: Mon, 7 Aug 2023 20:03:05 -0700 [thread overview]
Message-ID: <19c14d57-574b-9b31-de5a-a0590e189ce6@berlin.de> (raw)
In-Reply-To: <CADzB+2mGjdH6xDnJq+So4h2+56SQsNjFDmRVid9dCZ0evieE-g@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2453 bytes --]
On 06.08.23 12:19, Jason Merrill wrote:
> 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
Thanks for the answers!
There are a few really interesting extensions that I would like to use:
- inline variables
- variable templates
- `if constexpr`
- fold expressions
- conditional explicit
- static operator()
(https://godbolt.org/z/5n9Y4h69n)
Is anybody aware of any problems with these extensions? I'd be happy to
provide a patch to add these extensions to the documentation, but I
couldn't figure out how to build the documentation without building all
of gcc.
Nikolas
next prev parent reply other threads:[~2023-08-08 3:03 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3A4C9996-750B-4E3F-8F30-E3DA4366C7B5@berlin.de>
2023-08-06 19:19 ` Jason Merrill
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 [this message]
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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