libstdc++: Avoid symlink race in filesystem::remove_all [PR104161]
This adds a new internal flag to the filesystem::directory_iterator
constructor that makes it fail if the path is a symlink that resolves to
a directory. This prevents filesystem::remove_all from following a
symlink to a directory, rather than deleting the symlink itself.
We can also use that new flag in recursive_directory_iterator to ensure
that we don't follow symlinks if the follow_directory_symlink option is
not set.
This also moves an error check in filesystem::remove_all after the while
loop, so that errors from the directory_iterator constructor are
reproted, instead of continuing to the filesystem::remove call below.
libstdc++-v3/ChangeLog:
PR libstdc++/104161
* acinclude.m4 (GLIBCXX_CHECK_FILESYSTEM_DEPS): Check for
fdopendir.
* config.h.in: Regenerate.
* configure: Regenerate.
* src/c++17/fs_dir.cc (_Dir): Add nofollow flag to constructor
and pass it to base class constructor.
(directory_iterator): Pass nofollow flag to _Dir constructor.
(fs::recursive_directory_iterator::increment): Likewise.
* src/c++17/fs_ops.cc (do_remove_all): Use nofollow option for
directory_iterator constructor. Move error check outside loop.
* src/filesystem/dir-common.h (_Dir_base): Add nofollow flag to
constructor and when it's set use ::open with O_NOFOLLOW and
O_DIRECTORY.
* src/filesystem/dir.cc (_Dir): Add nofollow flag to constructor
and pass it to base class constructor.
(directory_iterator): Pass nofollow flag to _Dir constructor.
(fs::recursive_directory_iterator::increment): Likewise.
* src/filesystem/ops.cc (remove_all): Use nofollow option for
directory_iterator constructor. Move error check outside loop.