bug#21430: 25.0.50; resizing window in exwm crashes emacs

[martin rudalics]

> Out of curiosity: What was the problem? I had originally filed an exwm
> issue and would like to add this information there, too.

The bug was caused by my commit from 2014-07-27 with the ChangeLog entry

        * gtkutil.c (xg_frame_resized): Call do_pending_window_change.

Note that at the time of the commit that ChangeLog entry was

        * gtkutil.c (xg_frame_resized): Don't call
        do_pending_window_change.

so the commit was wrong twice: Once because the corresponding change
actually _added_ the call and once because adding the call was bad.

All this remained undetected for more than a year until Pip Cet filed
bug#21380 with a precise recipe.  I hopefully fixed the problem in a
commit with the ChangeLog entry

2015-08-31  Martin Rudalics  <rudalics@gmx.at>

        Don't call do_pending_window_change in signal handlers (Bug#21380)
        * src/gtkutil.c (xg_frame_resized):
        * src/xterm.c (x_set_window_size):
        * src/w32term.c (x_set_window_size): Don't call
        do_pending_window_change.

Apparently, the bug became virulent only when you've put something more
involved on ‘window-configuration-change-hook’.  What do you have there
(if it's no secret)?

martin