bug#23842: 24.4; Runaway background process

[Eli Zaretskii <eliz@gnu.org>]

> From: Ian Perryman <iperryman@xtreme-eda.com>
> Date: Fri, 24 Jun 2016 15:08:50 -0400
> 
> Open a new buffer called "moo.sv"
> 
> Paste this text into it without the tags:
> <start of file>
> module moo.sv;
>    ini
> <end of file>
> 
> Move point to the end of the second line.
> 
> Ensure that verilog-mode is enabled.  If it is not use "M-x
> verilog-mode"
> 
> Press M-?
> 
> This will open a buffer with possible completions ... there will only be
> one... "initial"
> 
> Use mouse-1 to select it.

With the current Emacs 25 pretest, this signals an error:

  Wrong type argument: window-live-p, #<window 7>

> This will cause the emacs session to start using 100% of the CPU (you
> should have a top session running separately to notice.  However this
> process is a background process and normal editing can continue until
> the process uses up all available memory.  I kill it quickly using
> "C-g".

Can someone reproduce this with the latest pretest of Emacs 25?

> Here is a dribble file including the C-g.  If you delete everything
> after the C-g, you will see the bad behavior.
> 
> 
> \x06moo.sv<return>module moo;ini<return><up> 0x800003f<help-echo><help-echo><help-echo><help-echo><help-echo><help-echo><help-echo><down-mouse-1><mouse-1>\a<help-echo><help-echo><help-echo><help-echo><help-echo><help-echo><help-echo>\x13\x03

Looks like some help-echo event is constantly generated, but I don't
understand what portion of which buffer causes this, and as I say
above I see a different problem.