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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/101588] New: rejects valid constexpr when binding from a
 constexpr function
Date: Fri, 23 Jul 2021 02:17:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101588

            Bug ID: 101588
           Summary: rejects valid constexpr when binding from a constexpr
                    function
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Split out from PR 66287.

Take:
struct T { int i; };
constexpr T copy(const T& v) { return v; }
constexpr const auto& r =3D T{42};
constexpr const auto& c =3D copy(r);
int main() {}
----- CUT ----
This should be accepted by GCC but currently is rejected:
<source>:11:33: error: modification of '<temporary>' is not a constant
expression
   11 | constexpr const auto& c =3D copy(r);
      |                                 ^=