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From: "Darrell.Wright at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/99535] New: g++ rejects valid code in constexpr copy ctor
 and volatile submember
Date: Thu, 11 Mar 2021 00:51:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99535

            Bug ID: 99535
           Summary: g++ rejects valid code in constexpr copy ctor and
                    volatile submember
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Darrell.Wright at gmail dot com
  Target Milestone: ---

The following code produces an error=20


struct Thing0 {
  volatile int a;

  constexpr Thing0( int v ): a{v} {}
  constexpr Thing0(Thing0 const& other) : a(other.a) {}
  constexpr Thing0& operator=3D(Thing0 const& rhs) {
    a =3D rhs.a;
    return *this;
  }
  ~Thing0() =3D default;
};

Thing0 func0() { return Thing0{5}; }

<source>: In copy constructor 'constexpr Thing0::Thing0(const Thing0&)':
<source>:7:51: error: lvalue-to-rvalue conversion of a volatile lvalue
'other.Thing0::a' with type 'const volatile int'
    7 |   constexpr Thing0(Thing0 const& other) : a(other.a) {}
      |                                             ~~~~~~^
<source>: In member function 'constexpr Thing0& Thing0::operator=3D(const
Thing0&)':
<source>:9:13: error: lvalue-to-rvalue conversion of a volatile lvalue
'rhs.Thing0::a' with type 'const volatile int'
    9 |     a =3D rhs.a;
      |         ~~~~^

The code should be accepted and is when the special methods are not constex=
pr.=