[Bug libstdc++/99995] New: [11 Regression] FAIL: 17_intro/headers/c++1998/49745.cc with -std=gnu++20

[Bug libstdc++/99995] New: [11 Regression] FAIL: 17_intro/headers/c++1998/49745.cc with -std=gnu++20

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

            Bug ID: 99995
           Summary: [11 Regression] FAIL:
                    17_intro/headers/c++1998/49745.cc with -std=gnu++20
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

In C++20 mode <memory> includes <bits/atomic_wait.h> which includes <unistd.h>
for SYS_futex, and that means that POSIX truncate is declared, leading to:

In file included from
/home/jwakely/build/powerpc64le-unknown-linux-gnu/libstdc++-v3/include/bits/atomic_wait.h:44,
                 from
/home/jwakely/build/powerpc64le-unknown-linux-gnu/libstdc++-v3/include/bits/atomic_base.h:41,
                 from
/home/jwakely/build/powerpc64le-unknown-linux-gnu/libstdc++-v3/include/bits/shared_ptr_atomic.h:33,
                 from
/home/jwakely/build/powerpc64le-unknown-linux-gnu/libstdc++-v3/include/memory:78,
                 from
/home/jwakely/build/powerpc64le-unknown-linux-gnu/libstdc++-v3/include/powerpc64le-unknown-linux-gnu/bits/stdc++.h:82,
                 from <command-line>:
/usr/include/unistd.h:1015: note: previous declaration 'int truncate(const
char*, __off_t)'
compiler exited with status 1
FAIL: 17_intro/headers/c++1998/49745.cc (test for excess errors)
Excess errors:
/home/jwakely/src/gcc/libstdc++-v3/testsuite/17_intro/headers/c++1998/49745.cc:22:
error: 'int truncate' redeclared as different kind of entity

This is only seen when adding -std=gnu++20 (or similar) to the test flags
explicitly, and only when PCH is enabled so that -include bits/stdc++.h is
added to the test flags, because otherwise that test doesn't include <memory>.
But the underlying problem is that including <unistd.h> means Bug 49745 has
returned: we include <unistd.h> from C++ library headers.

This is only an issue for C++20 mode, and will fix itself when the code to use
futexes moves into libstdc++.so rather than being in headers.

In the meantime, we might want to XFAIL that test for c++20 mode.

[Bug libstdc++/99995] [11 Regression] FAIL: 17_intro/headers/c++1998/49745.cc with -std=gnu++20

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.0

[Bug libstdc++/99995] [11 Regression] FAIL: 17_intro/headers/c++1998/49745.cc with -std=gnu++20

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

--- Comment #1 from CVS 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:29046e02b84a16b6315d952d7f76c502d0d021c2

commit r11-8127-g29046e02b84a16b6315d952d7f76c502d0d021c2
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Apr 12 11:12:47 2021 +0100

    libstdc++: Fix test that fails in C++20 mode [PR 99995]

    The 17_intro/headers/c++1998/49745.cc test fails for C++20 mode with PCH
    enabled, because PCH makes it include <bits/stdc++.h>, which includes
    <atomic>, and that includes <unistd.h> in C++20 mode. The <unistd.h>
    dependency should go away when C++20 atomic waiting is stable, but will
    probably remain while the feature is experimental. Change the test to
    always include <bits/stdc++.h>, and XFAIL for C++20 and later.

    libstdc++-v3/ChangeLog:

            PR libstdc++/99995
            * testsuite/17_intro/headers/c++1998/49745.cc: Include all
            standard headers and XFAIL for effective-target c++20.

[Bug libstdc++/99995] [11 Regression] should not include <unistd.h> in c++20 mode

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-04-12
             Status|UNCONFIRMED                 |SUSPENDED
            Summary|[11 Regression] FAIL:       |[11 Regression] should not
                   |17_intro/headers/c++1998/49 |include <unistd.h> in c++20
                   |745.cc with -std=gnu++20    |mode
   Target Milestone|11.0                        |12.0

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I've done the XFAIL. Removing the <unistd.h> dependency isn't going to happen
for GCC 11.

[Bug libstdc++/99995] [11/12 Regression] should not include <unistd.h> in c++20 mode

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Similarly, <semaphore> unconditionally includes POSIX <semaphore.h> even if
we're not going to use it.

[Bug libstdc++/99995] [11/12/13 Regression] should not include <unistd.h> in c++20 mode

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|12.0                        |12.2

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 12.1 is being released, retargeting bugs to GCC 12.2.

[Bug libstdc++/99995] [11/12/13/14 Regression] should not include <unistd.h> in c++20 mode

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99995

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|12.3                        |12.4

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 12.3 is being released, retargeting bugs to GCC 12.4.