[Bug libstdc++/114891] New: Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[Bug libstdc++/114891] New: Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[de34 at live dot cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

            Bug ID: 114891
           Summary: Unconditional use of
                    std::is_pointer_interconvertible_base_of_v in
                    <generator> makes the header unusable with Clang 18
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: de34 at live dot cn
  Target Milestone: ---

Clang only supports the intrinsic for is_pointer_interconvertible_base_of_v
since 19 (https://github.com/llvm/llvm-project/pull/88473).
It seems that the uses of is_pointer_interconvertible_base_of_v is not strictly
needed. Perhaps we should guard the uses with
__cpp_lib_is_pointer_interconvertible to support old versions of Clang.

[Bug libstdc++/114891] Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So a C++23 library header (generator) is using a C++20 feature
(is_pointer_interconvertible_base_of_v) ...

Especially since GCC 14.1.0 will most likely be released with this header and
14.2.0 won't come out until Summer end (around most likely around the same time
as clang 19). And GCC 15.1.0 won't come out until April/May 2025.
Supporting older clang which does not have C++20 support for something which is
C++23 (which itself won't fully be supported until GCC 15 at earliest).

[Bug libstdc++/114891] Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-04-30

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's only used for static assertions, so we can just disable those when the
feature isn't supported. But it's not a big deal, Clang users can just not use
<generator> for now.

[Bug libstdc++/114891] Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:1fbe1a50d86df11f434351cf62461a32747f9710

commit r15-92-g1fbe1a50d86df11f434351cf62461a32747f9710
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Apr 30 09:48:00 2024 +0100

    libstdc++: Guard uses of is_pointer_interconvertible_v [PR114891]

    This type trait isn't supported by Clang 18. It's only used in static
    assertions, so they can just be omitted if the trait isn't available.

    libstdc++-v3/ChangeLog:

            PR libstdc++/114891
            * include/std/generator: Check feature test macro before using
            is_pointer_interconvertible_v.

[Bug libstdc++/114891] Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.2

[Bug libstdc++/114891] Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:4d3b358fd757ddd09cbee202f47939043c78676c

commit r14-10206-g4d3b358fd757ddd09cbee202f47939043c78676c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Apr 30 09:48:00 2024 +0100

    libstdc++: Guard uses of is_pointer_interconvertible_v [PR114891]

    This type trait isn't supported by Clang 18. It's only used in static
    assertions, so they can just be omitted if the trait isn't available.

    libstdc++-v3/ChangeLog:

            PR libstdc++/114891
            * include/std/generator: Check feature test macro before using
            is_pointer_interconvertible_v.

    (cherry picked from commit 1fbe1a50d86df11f434351cf62461a32747f9710)

[Bug libstdc++/114891] Unconditional use of std::is_pointer_interconvertible_base_of_v in <generator> makes the header unusable with Clang 18

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 14.2