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From: "ryan_greenblatt at brown dot edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/98712] New: Incorrect defaulted operator== at compile time
 and runtime when declared constexpr and inheriting
Date: Sun, 17 Jan 2021 18:31:00 +0000
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X-Bugzilla-Version: 11.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98712

            Bug ID: 98712
           Summary: Incorrect defaulted operator=3D=3D at compile time and
                    runtime when declared constexpr and inheriting
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ryan_greenblatt at brown dot edu
  Target Milestone: ---

```
struct IntHolder {
  int v;
  bool operator=3D=3D(const IntHolder &) const =3D default;
};

struct Inherits : IntHolder {
  // without constexpr here the issue goes away...
  constexpr bool operator=3D=3D(const Inherits &) const =3D default;
};

#if 0
static_assert(Inherits{1} !=3D Inherits{2});
#else
#include <iostream>

int main() {
  // should output true...
  volatile int l =3D 1;
  std::cout << std::boolalpha << (Inherits{l} !=3D Inherits{2}) << std::end=
l;
}
#endif
```
https://godbolt.org/z/145dbq=