[Bug c++/111410] New: Bogus Wdangling-reference warning with ranges pipe expression in for loop

[Bug c++/111410] New: Bogus Wdangling-reference warning with ranges pipe expression in for loop

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111410

            Bug ID: 111410
           Summary: Bogus Wdangling-reference warning with ranges pipe
                    expression in for loop
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

#include <iostream>
#include <vector>
#include <ranges>

int main()
{
  std::vector v{1, 2, 3, 4, 5};
  for (auto i : std::span{v} | std::views::take(1))
    std::cout << i << '\n';
}

GCC-trunk reports the following warning when the -Wall flag is used:

<source>:8:51: warning: possibly dangling reference to a temporary
[-Wdangling-reference]
    8 |   for ( auto i : std::span{v} | std::views::take(1))
      |                                                   ^


https://godbolt.org/z/5jhnTTej9

[Bug c++/111410] Bogus Wdangling-reference warning with ranges pipe expression in for loop

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111410

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-01-18
                 CC|                            |mpolacek at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

[Bug c++/111410] Bogus Wdangling-reference warning with ranges pipe expression in for loop

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111410

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Thanks for the report.  I think we should disable the warning for operator|
coming from std::ranges.

[Bug c++/111410] Bogus Wdangling-reference warning with ranges pipe expression in for loop

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111410

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:7db802d972e622242d015ecd5a8cecf63e69a45a

commit r14-8307-g7db802d972e622242d015ecd5a8cecf63e69a45a
Author: Marek Polacek <polacek@redhat.com>
Date:   Fri Jan 19 15:27:51 2024 -0500

    libstdc++: suppress -Wdangling-reference with operator| [PR111410]

    It seems to me that we should exclude
std::ranges::views::__adaptor::operator|
    from the -Wdangling-reference warning.  It's commonly used when handling
    ranges.

            PR c++/111410

    libstdc++-v3/ChangeLog:

            * include/std/ranges: Add #pragma to disable -Wdangling-reference
with
            std::ranges::views::__adaptor::operator|.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Wdangling-reference17.C: New test.

[Bug c++/111410] Bogus Wdangling-reference warning with ranges pipe expression in for loop

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111410

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed for 14.