bug#39977: 28.0.50; Unhelpful stack trace

[Eli Zaretskii]

Ping!  Can you please try the proposed patch?

Martin, any thoughts or comments about this?

> Date: Sat, 07 Mar 2020 20:50:42 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 39977@debbugs.gnu.org
> 
> > From: Madhu <enometh@meer.net>
> > Date: Sat, 07 Mar 2020 23:13:16 +0530
> > 
> > Thanks Eli, Following up on the emacs-devel message, I recompiled emacs
> > and get substantially the same stack trace. This is with my ~/.emacs and
> > all my local customizations loaded.
> > 
> > when evaluating a form in a sly lisp buffer with
> >  (break)
> > M-x sly-eval-last-sexp
> > pops up a sly debug window in a new frame
> > quitting the window (and frame) tries to select the previous window
> > and the crash apparently happens at this point. I'm attaching the
> > backtraces as attachments
> > 
> > With a little guidance I expect to be able to investigate this further
> 
> Thanks.  Please try the patch below, and tell if it makes the crash
> go away.
> 
> diff --git a/src/window.c b/src/window.c
> index 8cdad27..863fac4 100644
> --- a/src/window.c
> +++ b/src/window.c
> @@ -541,8 +541,11 @@ select_window (Lisp_Object window, Lisp_Object norecord,
>    else
>      redisplay_other_windows ();
>  
> -  sf = SELECTED_FRAME ();
> -  if (XFRAME (WINDOW_FRAME (w)) != sf)
> +  if (FRAMEP (selected_frame) && FRAME_LIVE_P (XFRAME (selected_frame)))
> +    sf = XFRAME (selected_frame);
> +  else
> +    sf = NULL;
> +  if (!sf || XFRAME (WINDOW_FRAME (w)) != sf)
>      {
>        fset_selected_window (XFRAME (WINDOW_FRAME (w)), window);
>        /* Use this rather than Fhandle_switch_frame
> 
> 
> 
>