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Re: Edebug corrupting point in buffers; we need buffer-point and set-buf
From: |
Eli Zaretskii |
Subject: |
Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps. |
Date: |
Mon, 31 Oct 2022 19:55:40 +0200 |
> Date: Mon, 31 Oct 2022 15:46:07 +0000
> Cc: emacs-devel@gnu.org
> From: Alan Mackenzie <acm@muc.de>
>
> > I'm not sure performance in a debugger is a reason good enough to add
> > 2 more primitives. The fact that we didn't need them until now should
> > tell us something, no?
>
> Well, I timed it. With 207 buffers, creating an alist of (buffer .
> buffere-point) with my new function was 17 times as fast as using
> with-current-buffer and point.
17 times faster doesn't yet tell how important is the speedup, because
you give no absolute numbers, and they are what's important here.
> But on the other hand, these two functions feel like they ought to exist.
> They could save a lot of clumsy programming with swapping the buffer,
> just to get or set point.
There's nothing clumsy with what we did, and the fact that we did
manage without them speaks volumes.
> > > +DEFUN ("buffer-point", Fbuffer_point, Sbuffer_point, 1, 1, 0,
> > > + doc: /* Return the buffer point of BUFFER-OR-NAME.
> > > +The argument may be a buffer or the name of an existing buffer. */)
> > > + (Lisp_Object buffer_or_name)
>
> > Why not an optional argument to 'point'? And why in buffer.c and not
> > in editfns.c?
>
> I'm not sure what you mean by an optional argument, here.
I mean (point &optional buffer), of course, what else could I mean?
> > > + return (make_fixnum (b->pt));
>
> > Please never-ever use b->pt etc. directly. We have BUF_PT and other
> > macros for that, and for a good reason.
>
> BUF_PT and friends work specifically on current_buffer.
No, they don't:
/* Position of point in buffer. */
INLINE ptrdiff_t
BUF_PT (struct buffer *buf)
{
return (buf == current_buffer ? PT
: NILP (BVAR (buf, pt_marker)) ? buf->pt
: marker_position (BVAR (buf, pt_marker)));
}
> The whole idea of the new functions is to avoid having to switch
> buffers.
We do this from C in a gazillion of places.
- Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Alan Mackenzie, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Eli Zaretskii, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Alan Mackenzie, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Eli Zaretskii, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Alan Mackenzie, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Stefan Monnier, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps.,
Eli Zaretskii <=
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Alan Mackenzie, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Stefan Monnier, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Eli Zaretskii, 2022/10/31
- Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Stefan Monnier, 2022/10/31
Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Stefan Monnier, 2022/10/31
Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps., Alan Mackenzie, 2022/10/31