[Bug libstdc++/96816] New: bitset: debug mode: operator== ambiguous

[Bug libstdc++/96816] New: bitset: debug mode: operator== ambiguous

[jeanmichael.celerier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96816

            Bug ID: 96816
           Summary: bitset: debug mode: operator== ambiguous
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jeanmichael.celerier at gmail dot com
  Target Milestone: ---

Hello,

Given the following code: 

```
#define _GLIBCXX_DEBUG 1
#include <bitset>

std::bitset<3> a, b;
bool test = (a == b);
```

clang gives the following error: 

```
$ clang++ -c foo.cpp -std=c++20 
In file included from foo.cpp:2:
In file included from
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../include/c++/10.2.0/bitset:1595:
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../include/c++/10.2.0/debug/bitset:356:26:
error: use of overloaded operator '==' is ambiguous (with operand types 'const
std::__debug::bitset<3>::_Base' (aka 'const bitset<3UL>') and 'const
bitset<3UL>' (aka 'const std::__debug::bitset<3>'))
      { return _M_base() == __rhs; }
               ~~~~~~~~~ ^  ~~~~~
foo.cpp:5:16: note: in instantiation of member function
'std::__debug::bitset<3>::operator==' requested here
bool test = (a == b);
               ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../include/c++/10.2.0/bitset:1306:7:
note: candidate function
      operator==(const bitset<_Nb>& __rhs) const _GLIBCXX_NOEXCEPT
      ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../include/c++/10.2.0/debug/bitset:355:7:
note: candidate function (with reversed parameter order)
      operator==(const bitset<_Nb>& __rhs) const _GLIBCXX_NOEXCEPT
      ^
1 error generated
```

g++ does not, but I guess this still warrants checking ?

[Bug libstdc++/96816] bitset: debug mode: operator== ambiguous

[jeanmichael.celerier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96816

--- Comment #1 from Jean-Michaël Celerier <jeanmichael.celerier at gmail dot com> ---
gcc.godbolt.org link for easy repro: https://gcc.godbolt.org/z/WYbzfT

[Bug libstdc++/96816] bitset: debug mode: operator== ambiguous

[jeanmichael.celerier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96816

--- Comment #2 from Jean-Michaël Celerier <jeanmichael.celerier at gmail dot com> ---
I'd wager this is a result of C++20 operator<=> changes and operator==
synthesis.

[Bug libstdc++/96816] bitset: debug mode: operator== ambiguous

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96816

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

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

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Already fixed.

*** This bug has been marked as a duplicate of bug 96303 ***

[Bug libstdc++/96816] bitset: debug mode: operator== ambiguous

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96816

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jean-Michaël Celerier from comment #0)
> g++ does not, but I guess this still warrants checking ?

N.B. GCC does give an error if you compile with -Wpedantic -std=c++20