[Bug c++/116168] New: Segmentation fault when compiling user-defined partial_ordering

[daidodo at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116168

            Bug ID: 116168
           Summary: Segmentation fault when compiling user-defined
                    partial_ordering
           Product: gcc
           Version: 14.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daidodo at gmail dot com
  Target Milestone: ---

Created attachment 58790
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58790&action=edit
Details of the segment fault.

Hi,

The following code will cause Segmentation Fault when compiled with G++ 14.1.0:

```
// g++ main.cpp -std=c++23

namespace my
{
    struct partial_ordering
    {
        signed char v_;
        static const partial_ordering less;
        static const partial_ordering equivalent;
        static const partial_ordering greater;
        static const partial_ordering unordered;
    };

    constexpr partial_ordering partial_ordering::less{-1};
    constexpr partial_ordering partial_ordering::equivalent{0};
    constexpr partial_ordering partial_ordering::greater{1};
    constexpr partial_ordering partial_ordering::unordered{2};
}

namespace std
{
    using partial_ordering = my::partial_ordering;
}

int main() {
    auto a = 1.0 <=> 2.0;
}
```
I understand it may not be recommended to "replace" std::partial_ordering in
practice. But I'd expect more useful error messages when a user does so,
instead of a segment fault with encrypted text.

I've attached the -freport-bug result.

Thanks,
Zhao