On 09/12/2012 11:02 PM, Eli Zaretskii wrote:

> The reason for the assertion violation is the assertion in
> marker_position:
>
>    eassert (BUF_BEG (buf) <= m->charpos && m->charpos <= BUF_Z (buf));
>
> This was introduced recently by Dmitry, in revision 108906.  A similar
> assertion was added to marker_byte_position.
>
> Dmitry, why did you add them?  Who said that a marker cannot
> legitimately have a position outside of its buffer's range of
> character positions?

IIUC marker can have out-of-buffer-range position, but only somewhere in the
middle of an insertion/deletion/replace operation; out-of-range position should
be detected and immediately fixed by adjust_markers_for_{delete,insert,replace}.

BTW, look at this code from replace_range:

  /* Adjust the overlay center as needed.  This must be done after
      adjusting the markers that bound the overlays.  */
   adjust_overlays_for_delete (from, nchars_del);
   adjust_overlays_for_insert (from, inschars);

   /* Adjust markers for the deletion and the insertion.  */
   if (markers)
     adjust_markers_for_replace (from, from_byte, nchars_del, nbytes_del,
				inschars, outgoing_insbytes);

The comment explicitly says that overlays should be adjusted _after_ markers,
but the code adjusts overlays and then markers :-(. Since an overlays are
bounded by markers, the comment looks correct but the code isn't. I suppose
that the code snippets above should be swapped.

Dmitry