GNU bug report logs - #6960
mv refuses to move a symlink over a hard link to the same file

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Message #80 received at 6960 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Jim Meyering <jim <at> meyering.net>
Cc: 6960 <at> debbugs.gnu.org, Pádraig Brady <P <at> draigBrady.com>,
	Anders Kaseorg <andersk <at> MIT.EDU>
Subject: Re: bug#6960: mv refuses to move a symlink over a hard link to the
	same file
Date: Mon, 30 Jan 2012 09:46:24 -0800

On 01/30/2012 03:41 AM, Jim Meyering wrote:
>   /* At this point, it is normally an error (data loss) to move a symlink
>      onto its referent, but in at least one narrow case, it is not:
>      In move mode, when
>      1) src is a symlink,
>      2) dest is not a symlink,
>      3) dest has a link count of 2 or more and
>      4) dest and the referent of src are not the same entry,
>      then it's ok, since while we'll lose one of those hard links,
>      src will still point to a remaining link.
>      Note that technically, condition #4 obviates condition #2, but we
>      retain the 1 < st_nlink condition because that means fewer invocations
>      of the more expensive #4.

The last 3 lines are confusing.
Don't you mean "condition #3" and not "condition #2"?
The last 2 lines talk about condition 3, not condition 2.

Come to think of it, why is condition 2 needed at all?
Can't we eliminate it, both in the commentary and in the code?
If a symlink has a link count greater than 1, then overwriting
it won't lose the link; in that sense it's just like a regular
file with a link count greater than 1.  So why are symlinks
special there?

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