[Bug c++/99535] New: g++ rejects valid code in constexpr copy ctor and volatile submember

[Bug c++/99535] New: g++ rejects valid code in constexpr copy ctor and volatile submember

[Darrell.Wright at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99535

            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 


struct Thing0 {
  volatile int a;

  constexpr Thing0( int v ): a{v} {}
  constexpr Thing0(Thing0 const& other) : a(other.a) {}
  constexpr Thing0& operator=(Thing0 const& rhs) {
    a = rhs.a;
    return *this;
  }
  ~Thing0() = 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=(const
Thing0&)':
<source>:9:13: error: lvalue-to-rvalue conversion of a volatile lvalue
'rhs.Thing0::a' with type 'const volatile int'
    9 |     a = rhs.a;
      |         ~~~~^

The code should be accepted and is when the special methods are not constexpr.

[Bug c++/99535] g++ rejects valid code in constexpr copy ctor and volatile submember

[Darrell.Wright at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99535

--- Comment #1 from Darrell Wright <Darrell.Wright at gmail dot com> ---
I was wrong, http://eel.is/c++draft/expr.const#5.8

[Bug c++/99535] g++ rejects valid code in constexpr copy ctor and volatile submember

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99535

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, I think the special member functions are ill-formed (no diagnostic
required) as per http://eel.is/c++draft/dcl.constexpr#6.sentence-1