[Bug libstdc++/107799] New: Wrong return type for std::bit_width

[Bug libstdc++/107799] New: Wrong return type for std::bit_width

[diego at baldassar dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107799

            Bug ID: 107799
           Summary: Wrong return type for std::bit_width
           Product: gcc
           Version: 12.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: diego at baldassar dot net
  Target Milestone: ---

According to the C++20 standard, std::bit_width returns an int; in libstdc++ it
returns the same type as the argument.

The return type should probably be _If_is_unsigned_integer<_Tp, int> instead of
_If_is_unsigned_integer<_Tp>.

[Bug libstdc++/107799] Wrong return type for std::bit_width

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107799

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-11-22

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
No, according to the published C++20 standard it returns the same type as the
argument.

That was changed in July 2022 by https://cplusplus.github.io/LWG/issue3656 and
libstdc++ doesn't implement that change yet.

[Bug libstdc++/107799] Wrong return type for std::bit_width

[diego at baldassar dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107799

--- Comment #2 from Diego Baldassar <diego at baldassar dot net> ---
Ah I see, it was a DR. My mistake.

Will we see this updated for GCC 13? Or is it considered a breaking change
that's too late to fix?

[Bug libstdc++/107799] Wrong return type for std::bit_width

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107799

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It will get updated.

[Bug libstdc++/107799] Wrong return type for std::bit_width

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107799

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED
   Target Milestone|---                         |13.0

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Done in r13-4293-g4581328022615c