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From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 33784@debbugs.gnu.org, linux.xhyang@gmail.com
Subject: bug#33784: 27.0.50; some case c-backward-token-2 takes cpu more and emacs hang
Date: Tue, 18 Dec 2018 21:05:07 +0000	[thread overview]
Message-ID: <20181218210507.GD8949@ACM> (raw)
In-Reply-To: <83r2eed4fy.fsf@gnu.org>

Hello, Eli.

On Tue, Dec 18, 2018 at 21:23:45 +0200, Eli Zaretskii wrote:
> > Date: Tue, 18 Dec 2018 18:55:05 +0000
> > Cc: linux.xhyang@gmail.com, 33784@debbugs.gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > The current strategy is silently to ignore (font-lock-mode) when the
> > buffer name begins with a space.  It feels to me like an easy to
> > implement, but suboptimal, workaround to a real problem, whatever that
> > real problem might be.

> The real problem is probably performance.  But that's a guess; someone
> will have to do the forensics to find out which change did that, and
> then try to find related bug reports and/or discussions.

Hah!  The change, not to fontify buffers with names beginning with
spaces, was made by Simon Marshall on 1995-12-09.  The list archives only
go back to 2000.  :-(

I suspect what happened was that back last millenium, there was a strong
convention for what a buffer with a name beginning with a space meant,
and it was perfectly OK then not to fontify such a buffer.  Over time,
that convention became diluted such that even buffers created by users
(e.g. by with-temp-buffer) get names starting with a space.  But that's
only a guess.

Maybe the solution would be not to start with-temp-buffer names with a
space.

Indeed page "Buffer Names" in Elisp states "Buffers that are ephemeral
and generally uninteresting to the user have names starting with a
space", which is ambiguous - does a buffer have to be both ephemeral and
generally uninteresting, or will one of these properties do?  Probably
the latter.

Maybe the documentation for with-temp-buffer should be amended to
recommend Lisp programmers not to use it for buffers holding user text.

Or something like that.

-- 
Alan Mackenzie (Nuremberg, Germany).





  reply	other threads:[~2018-12-18 21:05 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-18  4:09 bug#33784: 27.0.50; some case c-backward-token-2 takes cpu more and emacs hang xh yang
     [not found] ` <mailman.5878.1545108246.1284.bug-gnu-emacs@gnu.org>
2018-12-18 17:47   ` Alan Mackenzie
     [not found] ` <20181218174716.96822.qmail@mail.muc.de>
2018-12-18 18:51   ` Eli Zaretskii
2018-12-18 18:55     ` Alan Mackenzie
     [not found]     ` <20181218185505.GC8949@ACM>
2018-12-18 19:23       ` Eli Zaretskii
2018-12-18 21:05         ` Alan Mackenzie [this message]
2018-12-18 22:05           ` Glenn Morris
2018-12-19 19:20             ` Alan Mackenzie
2018-12-19 15:22           ` Eli Zaretskii
2018-12-20  7:18 ` bug#33784: xh yang
2018-12-20 12:53   ` bug#33784: Alan Mackenzie

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