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

[Eli Zaretskii]

> From: Matthias Güdemann <matthias.guedemann@googlemail.com>
> Date: Mon, 07 Sep 2015 08:57:59 +0100
> 
> When using exwm (https://github.com/ch11ng/exwm) as window manager with
> the standard configuration given in
> 
> https://github.com/ch11ng/exwm/wiki/Configuration-Example
> 
> emacs25 (installed from Debian packages) crashes reproducably for me
> when doing: 
> 
>  - start emacs25
>  - M-x eshell
>  - start: mplayer -quiet $SOME_VIDEO
>  - C-c m (toogle MPlayer window as float)
>  - resize MPlayer window holding (s-MouseRight) and moving the mouse for
>    some seconds
> 
> gdb backtrace:

What is the value of waiting_for_input when it crashes?

Also, can you reproduce this in a non-optimized build, and present
backtrace (including "xbacktrace") from that?