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Date: Wed, 24 Oct 2012 17:01:27 -0400
From: Ken Brown <kbrown AT cornell DOT edu>
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Subject: Re: Emacs crashing on C-x C-g
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On 10/24/2012 9:09 AM, Ryan Johnson wrote:
> On 01/10/2012 4:08 PM, Ryan Johnson wrote:
>  > On 01/10/2012 3:07 PM, Ken Brown wrote:
>  >> On 10/1/2012 2:51 PM, Ryan Johnson wrote:
>  >>> I'm hitting a strange behavior with emacs lately, where hitting
>  >>> C-x C-g [1] sometimes causes it to quit instantly: no request to
>  >>> save files, no seg fault, no error message, just gone (have to
>  >>> reset the terminal to clear out emacs' ncurses settings). It
>  >>> invariably happens after I've been away from the terminal for a
>  >>> while (days) and then come back use it again.
>  >>>
>  >>> has anyone else had this happen to them?
>  >> I haven't seen it, and I do leave emacs running for days or weeks.
>  >> But I almost always run emacs under X, not in a terminal. Also, I
>  >> generally use the latest Cygwin snapshot.  Have you tried that?
>  >> Maybe you're being bitten by the /etc problem that Corinna fixed in
>  >> late July (http://cygwin.com/ml/cygwin/2012-07/msg00666.html).
>  > OK, I'll give the snapshot a try when I get a chance.
>
> Rats. I thought it was working, but the problem just it again. This time
> the emacs session had just been created by a mercurial check-in (to edit
> the changelog message) and crashed when I hit C-g to cancel an ESC I no
> longer needed.
>
> Packages:
> cygwin snapshot 1.7.17s(0.262/5/3) 20120917
> bash-4.1.10-4
> emacs-24.2-1
> emacs-x11-24.2-1
> mercurial-2.3.1-1
> mintty-1.1.2-1
>
> This time the crash is reproducible, and the test case below paints an
> "interesting" story:
>
> mkdir foo
> cd foo
> hg init
> touch foo
> hg add foo
> EDITOR='emacs -q -nw' hg ci
> ESC C-g
> <<<crash>>>
> reset
> <<<"reset is control-G (^G).">>>
> EDITOR='emacs -q -nw' hg ci
> C-g
> <<<"interrupted!">>>
> python
> C-g
> <<<"KeyboardInterrupt">>>
> quit # python still running
> reset -i ^c
> <<<no message>>>
> hg record foo
> C-g
> <<<"Quit (core dumped)">>>
> hg record foo
> C-c
> <<<"interrupted">>>
> python
> C-g
> <<<"Quit (core dumped)">>>
> python
> C-c
> <<<"KeyboardInterrupt">>>
> quit # python still running
>
> Apparently, emacs sets the terminal's interrupt character to ^G, causing
> ^G to interrupt the python script controlling emacs, causing the latter
> to not set interrupt back to ^C (due to abnormal exit), and causing
> serious (and permanent) confusion for bash: after setting the interrupt
> char back to ^C, ^C behaves as expected, but ^G crashes the app. In
> addition to mercurial/python above, the same core dump occurs with
> gnuplot, cat, and bash history search (^R).

This looks like a known Emacs issue:

   http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12697

I imagine it will be fixed before the release of Emacs 24.3.

Ken

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