GNU bug report logs - #530
Emacs 22 occasionally loses undo buffer?

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Date: Thu, 3 Jul 2008 16:14:29 -0700
From: "Casey Muratori" <casey <at> mollyrocket.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Emacs 22 occasionally loses undo buffer?
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I'm a long-time GNU Emacs user, and recently I updated to 22.x.

In 21.x, I never had any problems with undo, but in both 22.1 and 22.2
I will get an occasional loss of undo information for no apparent
reason.  After some editing operation, usually a kill or the undo of a
kill, etc., Emacs spontaneously decides that there is "no further undo
information", even though there clearly was, and the buffer is still
marked as modified.

It seems to happen _less_ frequently in 22.2 than in 22.1 so far, but
it's hard to tell, since I've been unable to come up with a reliable
way to reproduce the bug.

Is this a known problem?  Has anyone else reported something similar?
I've been trying to think of a way to debug it, but it seems very
difficult since there's no way to know when the bug will happen, and
once it happens, it's presumably too late to find out why...

This is running under Win32, btw, if that makes any difference: GNU
Emacs 22.2.1 (i386-mingw-nt5.1.2600)

- Casey