Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps.

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Alan Mackenzie <acm@muc.de>,  emacs-devel@gnu.org
> Date: Mon, 31 Oct 2022 13:19:34 -0400
> 
> >> +  CHECK_FIXNUM_COERCE_MARKER (pos);
> >> +  p = XFIXNUM (pos);
> >
> > This is sub-optimal: a marker holds both character and byte position,
> > and you lose it here.  Ignoring the byte position is only justified if
> > the marker belongs to the wrong buffer.
> 
> I suspect the performance impact is negligible

Are you talking about using character and byte position, or are you
talking about something else?  The performance impact of char_to_byte
is not negligible at all!

> compared to what it would
> cost using `set-buffer`.  Since we're not convinced the cost of
> `set-buffer` is high enough to justify `set-buffer-point`, I wouldn't
> worry about optimizing the case where the arg is a marker.

My remarks were general, not necessarily related to this particular
patch.  The principle should always be if you already have a byte
position, use it!