bug#28630: 27.0.50; C-g while a non-main thread is sitting crashes Emacs

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Sat, 07 Oct 2017 13:53:43 +0000
> Cc: 28630@debbugs.gnu.org, tom@tromey.com, agrambot@gmail.com
> 
> I'd rather see this as a bug and document it in etc/PROBLEMS.

PROBLEMS is not about Emacs bugs, it's about bugs in other software
that affect Emacs users and uses.  Emacs bugs are "documented" in the
bug tracker.

In any case, this is not a bug, this is how the feature was designed
and coded.  It's just that the consequences of this design were not
immediately apparent.

> Also, if the behavior between main and non-main threads differ, there should 
> probably a `in-main-thread-p'
> function. 

I'd rather not add primitives before there are real-life applications
that need them and can describe the needs and the requirements.  (We
have such a function on the C level, because it was actually needed.)