Subject: bug#14553: 24.3.50; C-g doesn't break inf-loop

From: Ken Brown <[email-masked]>
Date: Wed, 03 Jul 2013 07:13:49 -0400

On 7/2/2013 7:17 PM, Josh wrote:
> On Tue, Jul 2, 2013 at 1:12 PM, Ken Brown <[email-masked]> wrote:
>> On 6/4/2013 2:10 AM, Katsumi Yamaoka wrote:
>>>
>>> Hi,
>>>
>>> Start Emacs with the -Q option.
>>> Eval the form: (while t)
>>>
>>> Then I get unable to break it.  So is Emacs 24.3.  This may happen
>>> only on Cygwin, though.  It makes me hard to debug a code suspected
>>> to have an infinite loop.
>
>> I can confirm that this happens on Cygwin but not on GNU/Linux.  This may
>> just reflect the fact that Cygwin doesn't have SIGIO.  Maybe someone who
>> understands how Emacs handles keyboard input can weigh in on this and
>> suggest a workaround.
>
> FWIW, I am able to successfully interrupt that loop via C-g on my
> Cygwin system, which was configured with the --with-w32 flag and built
> from yesterday's trunk.

And this also works with the X11 build if Emacs is run in the Cygwin 
terminal (mintty).  So it appears that the problem only occurs when 
Emacs is running under X11.  I don't know anything about how keyboard 
input works under X11, so I'm not sure where to go from here.

Ken