From: Jakub Jelinek <jakub@redhat.com>
To: Jason Merrill <jason@redhat.com>, Jonathan Wakely <jwakely@redhat.com>
Cc: gcc-patches@gcc.gnu.org, Marek Polacek <polacek@redhat.com>
Subject: Re: [PATCH] c++, v2: Implement C++23 P2647R1 - Permitting static constexpr variables in constexpr functions
Date: Wed, 16 Nov 2022 07:19:50 +0100 [thread overview]
Message-ID: <Y3SBBsx+jLD5xs5R@tucnak> (raw)
In-Reply-To: <CACb0b4msuM8Ec14qR4PuKqqVHy+r8AdGgJhp_5sKhJE6W=vN4A@mail.gmail.com>
On Wed, Nov 16, 2022 at 12:27:02AM +0000, Jonathan Wakely wrote:
> On Tue, 15 Nov 2022 at 23:50, Jakub Jelinek <jakub@redhat.com> wrote:
> >
> > On Tue, Nov 15, 2022 at 06:36:38PM -0500, Jason Merrill wrote:
> > > > Here is an updated patch that passed bootstrap/regtest, the only
> > > > change is another testcase tweak.
> > > >
> > > > 2022-11-13 Jakub Jelinek <jakub@redhat.com>
> > > >
> > > > gcc/c-family/
> > > > * c-cppbuiltin.cc (c_cpp_builtins): Bump __cpp_constexpr
> > > > value from 202207L to 202211L.
> > > > gcc/cp/
> > > > * constexpr.cc (cxx_eval_constant_expression): Implement C++23
> > > > P2647R1 - Permitting static constexpr variables in constexpr functions.
> > > > Allow decl_maybe_constant_var_p static or thread_local vars for
> > > > C++23.
> > >
> > > This was accepted as a DR, so it shouldn't be limited to C++23 mode.
> > > Certainly it should be allowed in C++20 mode; I don't have a strong opinion
> > > about C++14/17. Jonathan, do you?
> >
> > How will a feature with feature test macro with multiple values work as DR?
> > Or will everything but the macro be treated as a DR (so __cpp_constexpr >=
> > 202211L only for C++23)?
>
> Yes, I think so. We just won't be able to advertise this feature as
> supported in C++20.
Ok. But there is another issue, the
https://eel.is/c++draft/expr.const#5.2
spot that P2647R1 is changing didn't exist in C++20, it was only added with
P2242R3. So, if one would treat P2647R1 as a DR for C++20, one has to come up with
a different standard modification.
Probably change the last bullet of:
[dcl.constexpr]/3
its function-body shall not enclose
a goto statement,
an identifier label,
a definition of a variable of non-literal type or of static or thread storage duration.
to
a definition of a variable of non-literal type or of a non-constexpr
variable of static or thread storage duration.
or so.
Jakub
next prev parent reply other threads:[~2022-11-16 6:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-11 17:07 [PATCH] c++: " Jakub Jelinek
2022-11-13 11:45 ` [PATCH] c++, v2: " Jakub Jelinek
2022-11-15 23:36 ` Jason Merrill
2022-11-15 23:50 ` Jakub Jelinek
2022-11-16 0:27 ` Jonathan Wakely
2022-11-16 6:19 ` Jakub Jelinek [this message]
2022-11-16 13:20 ` Jason Merrill
2022-11-16 14:08 ` Jakub Jelinek
2022-11-16 14:33 ` Jason Merrill
2022-11-16 14:46 ` Jakub Jelinek
2022-11-16 20:26 ` Jason Merrill
2022-11-17 9:13 ` [PATCH] c++, v3: " Jakub Jelinek
2022-11-17 14:42 ` Jason Merrill
2022-11-17 18:42 ` Jakub Jelinek
2022-11-17 20:42 ` [PATCH] c++, v4: " Jakub Jelinek
2022-11-18 0:15 ` Marek Polacek
2022-11-18 7:48 ` Jakub Jelinek
2022-11-18 15:03 ` Marek Polacek
2022-11-18 15:14 ` Jakub Jelinek
2022-11-18 16:24 ` Jason Merrill
2022-11-18 16:34 ` Jakub Jelinek
2022-11-18 16:52 ` Jason Merrill
2022-11-18 0:28 ` Jason Merrill
2022-11-18 9:10 ` [PATCH] c++, v5: " Jakub Jelinek
2022-11-16 0:26 ` [PATCH] c++, v2: " Jonathan Wakely
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