[RFC] Call lstat() before setting flags to FTW_SLN

[DJ Delorie]

"Tulio Magno Quites Machado Filho" <tuliom@linux.vnet.ibm.com> writes:
> POSIX.1-2008 doesn't describe this behavior explicitly in this case.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1422736
and http://austingroupbugs.net/view.php?id=1121

The spec also says "If FTW_PHYS is clear ... nftw() shall follow links
instead of reporting them" but calling lstat() *is* reporting them,
which the spec specifically forbids, if you read it that way.

Hence, the clarification I requested from the Austin Group.  If the spec
says we're not allowed to call lstat(), your patch is inappropriate.  If
we are allowed to call lstat(), I think your patch is wrong - it may
return FTW_NS for cases where lstat() might fail, where FTW_SLN should
have been returned.  I can't think of any such cases, but I've been
surprised before.  Also, cases where FTW_NS should be returned due to
errors reading *non*dangling links should be preserved.

(I suspect calling LXSTAT() when we set the flag where your patch
 deleted lines, should result in the desired behavior, though, possibly
 with a test for !FTW_PHYS)