bug#20074: edebug tracing can't be stopped with 'S'

[Alexis <flexibeast@gmail.com>]

On 2015-03-14T00:20:52+1100, Stefan Monnier 
<monnier@iro.umontreal.ca> said:

 SM> Normally this should never happen.  In practice there are 
 various SM> cases where this can happen for two reasons:
 SM> - A bug.  Some of those can be difficult to fix, tho.
 SM> - `inhibit-quit' is non-nil while running this inf-loop.  In 
 this SM> case, indeed, it's usually a bug in the Elisp code 
 rather than in SM> the C code: code that runs with inhibit-quit 
 (e.g. code run from a SM> timer) should be careful to avoid long 
 run-times.  This isn't SM> great, but it's what we have so far.

*nod* i've never set `inhibit-quit` non-nil in my own code, but i 
imagine it's more than possible that something i was calling was 
setting it non-nil, so i'll keep that in mind.

More generally, if i again encounter an unresponsive-Emacs 
scenario like the one i mentioned, i'll note it on help-gnu-emacs, 
to get others' input about whether or not it's an Emacs bug.

Thanks!


Alexis.