bug#30937: In `comment-region', C-g doesn't work.

[Eli Zaretskii]

> Date: Sun, 25 Mar 2018 14:28:55 +0000
> From: Alan Mackenzie <acm@muc.de>
> 
> emacs-26.0.91 -Q
> C-x C-f Any largish file.c
> C-x h                 ; mark buffer.
> C-c C-c               ; comment-region.
> 
> This is the sort of thing that can happen by accident.  Depending on the
> size of the file.c and the speed of your machine, you've now got a long,
> long wait.  C-g doesn't work.  This is a bug.

C-g does work for me just fine in the above recipe.  Maybe it's
platform dependent, and the problem happens only on X?