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From: "mpolacek at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/100976] [C++23] Make constexpr reference temp constexpr
Date: Thu, 01 Jul 2021 20:09:58 +0000	[thread overview]
Message-ID: <bug-100976-4-2U1gN3Fmol@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-100976-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100976

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Jason Merrill from comment #2)
> Or rather,
> 
> int main()
> {
>   constexpr const int &r = 42;
>   static_assert(r == 42); // { dg-bogus "" }
> }
> 
> [expr.const]/4.7 says that "a temporary object of non-volatile
> const-qualified literal type whose lifetime is extended to that
> of a variable that is usable in constant expressions" is usable in a
> constant expression.

This was actually CWG 2126 which we don't seem to fully implement:

struct A { int n; };

const A &a = {1};              // const temporary
A &b = (A &)(const A &)A{1};   // const temporary
A &&c = (A &&)(const A &)A{1}; // const temporary

static_assert(a.n == 1, "");
static_assert(b.n == 1, "");
static_assert(c.n == 1, "");

  parent reply	other threads:[~2021-07-01 20:09 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-08 17:46 [Bug c++/100976] New: " jason at gcc dot gnu.org
2021-06-08 17:46 ` [Bug c++/100976] " mpolacek at gcc dot gnu.org
2021-06-08 18:45 ` jason at gcc dot gnu.org
2021-06-08 20:51 ` jason at gcc dot gnu.org
2021-07-01 16:55 ` mpolacek at gcc dot gnu.org
2021-07-01 20:09 ` mpolacek at gcc dot gnu.org [this message]
2021-07-19 13:59 ` mpolacek at gcc dot gnu.org

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