[Bug libstdc++/121071] New: std::hash<__int128> and std::hash ignore bits >= SIZE_WIDTH

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121071

            Bug ID: 121071
           Summary: std::hash<__int128> and std::hash<long long> ignore
                    bits >= SIZE_WIDTH
           Product: gcc
           Version: 15.1.0
            Status: UNCONFIRMED
          Keywords: ABI
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

For all integer types std::hash just returns the original value:

  template<>                                            \
    struct hash<_Tp> : public __hash_base<size_t, _Tp>  \
    {                                                   \
      size_t                                            \
      operator()(_Tp __val) const noexcept              \
      { return static_cast<size_t>(__val); }            \
    };

For types wider than size_t this discards all the high bits