bug#37671: 27.0.50; Segmentation fault with --fg-daemon on Linux

[Eli Zaretskii]

> From: Frank Terbeck <ft@bewatermyfriend.org>
> Cc: 37671@debbugs.gnu.org
> Date: Sat, 01 Feb 2020 03:28:09 +0100
> 
> Eli Zaretskii wrote:
> > (I assume that you still have the crashed session in the debugger.)
> 
> Okay, new chance. :)

Thanks.

> Thread 1 "emacs-28.0.50" received signal SIGSEGV, Segmentation fault.
> show_mouse_face (hlinfo=0x555556d00830, draw=DRAW_NORMAL_TEXT) at 
> xdisp.c:31447
> 31447         && hlinfo->mouse_face_end_row < w->current_matrix->nrows)
[...]
> (gdb) p *hlinfo
> $9 = {mouse_face_beg_row = 16,
>       mouse_face_beg_col = 21,
>       mouse_face_beg_x = 252,
>       mouse_face_end_row = 16,
>       mouse_face_end_col = 35,
>       mouse_face_end_x = 420,
>       mouse_face_window = 0x5555571b9bc5,
>       mouse_face_face_id = 52,
>       mouse_face_overlay = 0x0,
>       mouse_face_mouse_frame = 0x5555589ff5d0,
>       mouse_face_mouse_x = 401,
>       mouse_face_mouse_y = 425,
>       mouse_face_past_end = false,
>       mouse_face_defer = false,
>       mouse_face_hidden = false}

So hlinfo seems to be OK.  What about this part:

> 31447         && hlinfo->mouse_face_end_row < w->current_matrix->nrows)
                                                ^^^^^^^^^^^^^^^^^^^^^^^^

Try:

  (gdb) p *w

and then

  (gdb) p *w->current_matrix