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

[YAMAMOTO Mitsuharu]

>>>>> On Wed, 04 Oct 2017 10:39:05 +0300, Eli Zaretskii <eliz@gnu.org> said:

>> I think the second thread calls setjmp and clobbers the values set
>> by the main thread, when the main thread called setjmp.

> That guess was correct.

> I hope I fixed this now, but please test this in a GUI session on X,
> as I couldn't test that configuration.  If there are still crashes,
> please post a backtrace.

My patch was a bit late :-)

I confirmed the original test case no longer crashes with your patch
on X11 (and also on my internal version of the Mac port for Emacs 26).
Thanks.

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp