GNU bug report logs - #394
wdired-change-to-wdired-mode can cause file deletion

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: xah lee <xah <at> xahlee.org>
To: bug-gnu-emacs <at> gnu.org
Subject: wdired-change-to-wdired-mode can cause file deletion
Date: Thu, 12 Jun 2008 01:39:07 -0700

In dired, do M-x wdired-change-to-wdired-mode.

Then, swap 2 files's names.

Emacs will ask if the first file should be overwritten. If answer  
yes, it'll be deleted, and it wont be renamed. i.e. you lose a file.

This can be reproduced if you created 2 files, one named A and other  
B. Then renamed them to B and A. (Possibly you will need to create 3  
files and rename in particular cycle depending on how emacs choose  
the order to rename... The key is to get emacs to prompte for the  
overwrite of a file that should be renamed to something else later.)

This behavior is slightly unexpected and caused me to retrieve from  
my backup disk. (the files are images and never edited, so it isn't  
in emacs's backup)

  Xah
∑ http://xahlee.org/

☄

Message #10 received at 394-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: 394-done <at> debbugs.gnu.org
Subject: Re: bug#394: wdired-change-to-wdired-mode can cause file deletion
Date: Sat, 14 Jun 2008 13:01:52 -0400

> In dired, do M-x wdired-change-to-wdired-mode.
> Then, swap 2 files's names.
> Emacs will ask if the first file should be overwritten. If answer yes, it'll
> be deleted, and it wont be renamed. i.e. you lose a file.

Indeed, dired's rename is a "parallel" rename, whereas our underlying
C primitives only offer sequential renaming, so we need to de more work
to handle those cases.

I've installed a patch into the CVS trunk which should fix it (or at
least catch the problem before it's too late).


        Stefan

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