[PATCH] libstdc++-v3: check for openat

[Jonathan Wakely]

On Mon, 27 Jun 2022 at 14:05, Alexandre Oliva <oliva@adacore.com> wrote:
>
> On Jun 27, 2022, Alexandre Oliva <oliva@adacore.com> wrote:
>
> > It looks like the atp.pathname is missing the nonexistent_path
> > assigned to variable dir in test_pr99290, so we attempt to open
> > subdirs thereof as if with openat.
>
> This appears to be caused by the early return in fs::_Dir's ctor:
>
>   _Dir(const fs::path& p, bool skip_permission_denied, bool nofollow,
>        [[maybe_unused]] bool filename_only, error_code& ec)
>   : _Dir_base(p.c_str(), skip_permission_denied, nofollow, ec)
>   {
> #if _GLIBCXX_HAVE_DIRFD // && 0
>     if (filename_only)
>       return; // Do not store path p when we aren't going to use it.
> #endif

Yes, this needs a fix. If we don't have openat then we always need a
full path relative to the CWD, not just a filename relative to a file
descriptor for the parent directory.

I think we need to store the directory's path if any of dirfd, openat
or unlinkat is missing.


>
>     if (!ec)
>       path = p;
>   }
>
> but somehow disabling the early return to force the saving of path
> appears to break copy(): copy.cc's test01() succeeded without the '&& 0'
> that I've commented-out above, but started failing to create 'to' in the
> copy at line copy.cc:54 when I put it in to prevent the early return.
>
> Does that make any sense to you?

No, I'll have to debug the test. I thought that not storing the path
was just an optimization (to avoid parsing, decomposing, and
allocating a path object that we will never use).