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From: "valentin.david at codethink dot co.uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/94681] New: filesystem::sysmlink_status using stat
 instead of lstat when --disable-libstdcxx-filesystem-ts
Date: Tue, 21 Apr 2020 08:41:10 +0000
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X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 9.3.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94681

            Bug ID: 94681
           Summary: filesystem::sysmlink_status using stat instead of
                    lstat when --disable-libstdcxx-filesystem-ts
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: valentin.david at codethink dot co.uk
  Target Milestone: ---

Created attachment 48321
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D48321&action=3Dedit
Proposed fix

std::filesystem::sysmlink_status follows symlinks when GCC has been configu=
red
with --disable-libstdcxx-filesystem-ts, but it works fine when it has been
configured with --enable-libstdcxx-filesystem-ts.

The reason is that libstdc++-v3/src/c++17/fs_ops.cc includes
libstdc++-v3/src/filesystem/ops-common.h which has some requirements in the
configure script that are not executed.

In libstdc++-v3/acinclude.m4, GLIBCXX_CHECK_FILESYSTEM_DEPS is guarded by t=
est
"$enable_libstdcxx_filesystem_ts =3D yes". But this should be run even if
enable_libstdcxx_filesystem_ts is "no" since
libstdc++-v3/src/filesystem/ops-common.h is used when
--disable-libstdcxx-filesystem-ts is used.

Removing this "if" fixed the issue for me.

While I have not tested master, I believe the issue is still there.=