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Re: [RFC] Call lstat() before setting flags to FTW_SLN
- From: DJ Delorie <dj at redhat dot com>
- To: "Tulio Magno Quites Machado Filho" <tuliom at linux dot vnet dot ibm dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Fri, 24 Feb 2017 22:26:51 -0500
- Subject: Re: [RFC] Call lstat() before setting flags to FTW_SLN
- Authentication-results: sourceware.org; auth=none
- References: <1487981243-16382-1-git-send-email-tuliom@linux.vnet.ibm.com>
"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)