[Bug c++/109623] New: constexpr restrictions are not relaxed enough

[Bug c++/109623] New: constexpr restrictions are not relaxed enough

[oleksandr.koval.dev at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109623

            Bug ID: 109623
           Summary: constexpr restrictions are not relaxed enough
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: oleksandr.koval.dev at gmail dot com
  Target Milestone: ---

https://godbolt.org/z/eo8K3Ehqq

```cpp
#include <unordered_map>

struct S{
    constexpr S() = default;       // error, not implicitly constexpr
    constexpr S(){}                // this works
    std::unordered_map<int, int> m;
};

```

My understanding is that in C++23 this should be allowed because the only
restriction for constexpr constructors and destructors is the absence of
virtual base classes.

[Bug c++/109623] constexpr restrictions are not relaxed enough

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109623

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=106649

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think this shoulda been done for Bug 106649, IIUC

[Bug c++/109623] constexpr restrictions are not relaxed enough

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109623

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-04-27
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Most likely, mine thus.

[Bug c++/109623] constexpr restrictions are not relaxed enough

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109623

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
// PR c++/109623

struct U {
  U() { }
};

struct S {
  constexpr S() = default;
  U u;
};