From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: Jason Merrill <jason@redhat.com>
Cc: Nikolas Klauser <nikolasklauser@berlin.de>,
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 14:04:17 +0100 [thread overview]
Message-ID: <CAH6eHdT9RB4tErYquB2Fq06PUWnGv17VmqYsnPM2ke1Na-dKug@mail.gmail.com> (raw)
In-Reply-To: <CAH6eHdSbCLE6VtdNF16TXynWf=bjNedjFxdSVCMkqgyp2M7PQw@mail.gmail.com>
On Sun, 6 Aug 2023 at 20:43, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>
> On Sun, 6 Aug 2023 at 20:20, Jason Merrill via Libstdc++
> <libstdc++@gcc.gnu.org> 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?
>
> We use variadic templates and long long in C++98. We use a DMI in
> __gnu_cxx::__mutex even in C++98. I don't think we unconditionally use
> anything else, because we can't rely on it being available when using
> non-GCC compilers, or when compiling with -Wsystem-headers -pedantic.
> We don't use if-constexpr before C++17 for example.
Oh, but we do use __decltype in a few places.
next prev parent reply other threads:[~2023-08-07 13:04 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
2023-08-06 19:43 ` Jonathan Wakely
2023-08-07 13:04 ` Jonathan Wakely [this message]
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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