Re: Hang in make check

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Sun, 28 Mar 2021 21:51:29 +0200
> Cc: Emacs developers <emacs-devel@gnu.org>
> 
> Lars Ingebrigtsen <larsi@gnus.org> writes:
> 
> > Ah; "make keyboard-tests" with those options does indeed hang (when
> > testing on Debian/bullseye).
> 
> Seems to have something to do with timers and timeouts.  This hangs:
> 
> (read-event nil nil 1)
> 
> when run in batch mode, apparently (instead of timing out after one
> second).

But that's not what the test does (if it did, it would have hanged for
everyone, regardless of the build details).  The test does:

  (let ((unread-command-events nil))
    (should (equal (progn (push ?\C-a unread-command-events)
                          (read-event nil nil 1))
                   ?\C-a))

When there's some stuff in unread-command-events, read-event should
return immediately with the first element of what's in
unread-command-events.  Why doesn't it happen in that build?  Can you
step through the code and tell why not?