Re: readdir and ENOENT error or EOF?

[Florian Weimer <fweimer@redhat.com>]

* Mark Olesen via Libc-alpha:

> There appears to be ambiguity in user documentation for readdir when
> it returns NULL and errno is set to ENOENT.
>
> Is this an EOF condition or an actual error that should be handled?
>
> ...
> /* On some systems getdents fails with ENOENT when the
> open directory has been rmdir'd already. POSIX.1
> requires that we treat this condition like normal EOF. */
> if (bytes < 0 && errno == ENOENT)
> bytes = 0;
> ...
> https://code.woboq.org/userspace/glibc/sysdeps/posix/readdir.c.htmlin

Note that the Linux implementation is in
sysdeps/unix/sysv/linux/readdir.c, but it has this quirk as well.

I believe this has been copied over from historic times.  In general,
Linux handles this corner case differently.  However, the Linux VFS
layer will pass through ENOENT from file system implementations, so if a
file system implementation generates ENOENT in its readdir
implementation, we might still see ENOENT in userspace.  That's why it's
difficult to remove the check from glibc's readdir implementation.

Thanks,
Florian