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From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps.
Date: Mon, 31 Oct 2022 20:46:12 +0000	[thread overview]
Message-ID: <Y2A0FJS6dJa7shE6@ACM> (raw)
In-Reply-To: <83mt9bev37.fsf@gnu.org>

Hello, Eli.

On Mon, Oct 31, 2022 at 19:55:40 +0200, Eli Zaretskii wrote:
> > 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.

I think I did.  To quote:
> > It's probably moot, though, since the "slow" restoration only took
> > 0.00137 seconds for all 207 buffers.

> > 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.

OK.

> > > > +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?

OK.

> > > > +  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:

Apologies.  I got that wrong.

>   /* 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.

OK.  I now think these new functions aren't really needed, mainly because
the current way, though much slower, is fast enough.  I still think they
would be a neater way of getting/setting a buffer point, but it's not a
big thing.

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2022-10-31 20:46 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-31 11:43 Edebug corrupting point in buffers; we need buffer-point and set-buffer-point, perhaps Alan Mackenzie
2022-10-31 13:16 ` Eli Zaretskii
2022-10-31 14:32   ` Alan Mackenzie
2022-10-31 14:50     ` Eli Zaretskii
2022-10-31 15:46       ` Alan Mackenzie
2022-10-31 17:33         ` Stefan Monnier
2022-10-31 17:55         ` Eli Zaretskii
2022-10-31 20:46           ` Alan Mackenzie [this message]
2022-11-01  6:21             ` Eli Zaretskii
2022-10-31 17:19       ` Stefan Monnier
2022-10-31 18:09         ` Eli Zaretskii
2022-10-31 20:35           ` Stefan Monnier
2022-10-31 17:21 ` Stefan Monnier
2022-10-31 18:10   ` Eli Zaretskii
2022-10-31 23:14     ` Stefan Monnier
2022-11-01  7:06       ` Eli Zaretskii
2022-10-31 21:25 ` Alan Mackenzie
2022-11-01  6:45   ` Eli Zaretskii
2022-11-01 11:41     ` Edebug corrupting point in buffers Alan Mackenzie
2022-11-01 11:53       ` Eli Zaretskii
2022-11-01 13:42         ` Alan Mackenzie
2022-11-01 14:42           ` Eli Zaretskii
2022-11-01 17:06             ` Alan Mackenzie
2022-11-01 17:12               ` Eli Zaretskii
2022-11-01 17:24                 ` Alan Mackenzie
2022-11-01 17:57                   ` Eli Zaretskii
2022-11-01 19:02                     ` Alan Mackenzie
2022-11-01 19:47                       ` Stefan Monnier
2022-11-01 20:53                         ` Alan Mackenzie
2022-11-01 21:51                           ` Stefan Monnier
2022-11-02 10:40                             ` Alan Mackenzie
2022-11-02 13:12                               ` Stefan Monnier
2022-11-02 13:28                                 ` Eli Zaretskii
2022-11-02  3:28                         ` Eli Zaretskii
2022-11-02 12:53                           ` Stefan Monnier
2022-11-02 17:40                       ` Juri Linkov
2022-11-02 18:26                         ` Eli Zaretskii
2022-11-02 18:36                           ` Juri Linkov
2022-11-02 18:52                             ` Eli Zaretskii
2022-11-03 17:25                               ` Juri Linkov
2022-11-03 18:06                                 ` Eli Zaretskii
2022-11-03 18:31                                   ` Juri Linkov
2022-11-02 11:34                     ` Alan Mackenzie
2022-11-02 14:00                       ` Eli Zaretskii
2022-11-02 16:18                         ` Alan Mackenzie
2022-11-02 16:57                           ` Eli Zaretskii
2022-11-03 11:32                             ` Alan Mackenzie
2022-11-03 13:29                               ` Eli Zaretskii
2022-11-03 18:07                                 ` Alan Mackenzie
2022-11-03 18:15                                   ` Eli Zaretskii
2022-11-03 20:25                                     ` Alan Mackenzie
2022-11-05 11:24                                       ` Eli Zaretskii
2022-11-05 16:50                                         ` Alan Mackenzie
2022-11-06  8:10                                           ` Eli Zaretskii
2022-11-06 14:40                                             ` Alan Mackenzie
2022-11-03 19:29                         ` Stefan Monnier
2022-11-03 19:36                           ` Eli Zaretskii
2022-11-03 20:39                             ` Stefan Monnier
2022-11-04  6:34                               ` Eli Zaretskii
2022-11-04  6:37                               ` Eli Zaretskii
2022-11-03 19:57                           ` Alan Mackenzie
2022-11-03 20:35                             ` Stefan Monnier

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