bug#30182: Update

[Eli Zaretskii]

> Date: Wed, 24 Jan 2018 09:38:49 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: m.sujith@gmail.com, 30182@debbugs.gnu.org
> 
> I asked the OP to
> 
>    Just to eliminate one possible cause: Does the bug disappear when you
>    customize `mode-line-default-help-echo' to the default value of the
>    'string' alternative?
> 
> and he answered that
> 
>    Yes, if that is done, then the crash doesn't happen.

OK, thanks.

>  > So if using a string instead of a function the returns a string solves
>  > the problem, then I guess we should try and understand why a function
>  > causes the problem.
> 
> Apparently because evaluating that function creates a timer.

You mean, mode-line-default-help-echo creates a timer?  If it does, I
don't see where it does that.

> w3m.el, when creating a buffer for its purposes, does
> 
>    (setq mode-line-buffer-identification
>       `(
> [...]
>         (w3m-current-process
>          "Loading..." ,(if (fboundp 'format-mode-line)
>                            '(:eval (w3m-modeline-title))
> 
> where the latter contains
> 
> (defun w3m-modeline-title ()
> [...]
>                               (condition-case nil
>                                   (format-mode-line mode-line-format 1)
>                                 (error "")))
> [...]
>           (run-at-time 0.5 nil
>                        (lambda (buffer)
>                          (when (buffer-live-p buffer)
>                            (with-current-buffer buffer
>                              (setq w3m-modeline-title-timer nil))))
>                        (current-buffer)))))))
> 
> 
> But I haven't been able yet to trigger the crash from here.

What I don't understand is how is the above :eval form related to
mode-line-default-help-echo.  They are both properties of parts of the
mode line, but how is that relevant to the issue at hand?