Subject: bug#35273: "Marker does not point anywhere" when reading next article

From: Leah Neukirchen <[email-masked]>
Date: Tue, 16 Apr 2019 16:04:01 +0200

Noam Postavsky <[email-masked]> writes:

>> (gdb) bt
>> #0  marker_position (marker=XIL(0x5555578a47c5)) at marker.c:680
>> #1  0x00005555556fc2dd in mouse_face_overlay_overlaps (
>>     overlay=XIL(0x5555578a4825)) at buffer.c:3047
>> #2  0x0000555555606f5f in note_mouse_highlight (f=0x55555610dbf0, x=100, y=9)
>>     at xdisp.c:31631
>
>> (gdb) up
>> #1  0x00005555556fc2dd in mouse_face_overlay_overlaps (
>>     overlay=XIL(0x5555578a4825)) at buffer.c:3047
>> 3047	  ptrdiff_t start = OVERLAY_POSITION (OVERLAY_START (overlay));
>> (gdb) l
>> 3042	   `mouse-face' property overlapping OVERLAY.  */
>> 3043	
>> 3044	bool
>> 3045	mouse_face_overlay_overlaps (Lisp_Object overlay)
>> 3046	{
>> 3047	  ptrdiff_t start = OVERLAY_POSITION (OVERLAY_START (overlay));
>> 3048	  ptrdiff_t end = OVERLAY_POSITION (OVERLAY_END (overlay));
>
> Oh right, OVERLAY_POSITION calls marker_position.  I think the patch
> below should paper over the problem, but I'm not sure if it's the right
> thing.
>
> --- i/src/buffer.c
> +++ w/src/buffer.c
> @@ -3044,8 +3044,13 @@ overlays_in (EMACS_INT beg, EMACS_INT end, bool extend,
>  bool
>  mouse_face_overlay_overlaps (Lisp_Object overlay)
>  {
> -  ptrdiff_t start = OVERLAY_POSITION (OVERLAY_START (overlay));
> -  ptrdiff_t end = OVERLAY_POSITION (OVERLAY_END (overlay));
> +  Lisp_Object start_pos = Fmarker_position (OVERLAY_START (overlay));
> +  Lisp_Object end_pos = Fmarker_position (OVERLAY_END (overlay));
> +  if (!(INTEGERP (start_pos) && INTEGERP (end_pos)))
> +    return false;
> +  intmax_t start, end;
> +  integer_to_intmax (start_pos, &start);
> +  integer_to_intmax (end_pos, &end);
>    ptrdiff_t n, i, size;
>    Lisp_Object *v, tem;
>    Lisp_Object vbuf[10];
>

I cannot reproduce the error anymore after applying the patch.

Thanks,
-- 
Leah Neukirchen  <[email-masked]>  http://leah.zone