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From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: ccsmile2008@outlook.com, npostavs@gmail.com, emacs-devel@gnu.org
Subject: Re: beginning-of-defun-comments bug [was: Re: 26.0.90: mark-defun problem in c-mode]
Date: Sat, 30 Dec 2017 13:05:29 +0000	[thread overview]
Message-ID: <20171230130529.GE10623@ACM> (raw)
In-Reply-To: <83shbse5rs.fsf@gnu.org>

Hello, Eli.

On Sat, Dec 30, 2017 at 14:53:27 +0200, Eli Zaretskii wrote:
> > Date: Sat, 30 Dec 2017 12:01:36 +0000
> > Cc: emacs-devel@gnu.org, zhang cc <ccsmile2008@outlook.com>,
> >   Noam Postavsky <npostavs@gmail.com>
> > From: Alan Mackenzie <acm@muc.de>

> > > I see the error, with point anywhere in the body of the second function.
> > > Critical seems to be there being no blank line between the functions.

> > > I think there's a bug in beginning-of-defun-comments, which I'm in the
> > > middle of edebugging.  It moves point into the first function.

> > beginning-of-defun-comments has a bug.  On doing M-x
> > beginning-of-defun-comments from the inside of a function, when there's
> > no blank lines between it and the previous function, point ends up
> > inside that previous function, not at the comments which may separate
> > them.

> > Perhaps this bug should be fixed before the next Emacs-26 pretest.

> How old is this problem?  It looks like it's new in Emacs 26?  If so,
> we should try fixing it on the release branch.

beginning-of-defun-comments came into existence on 2017-03-31, so this
problem is definitely new in Emacs 26.

I've diagnosed the bug.  At one place, it is necessary to scan a line of
text from BOL to detect any non-comment/non-space character.  The
current code tries to do this by using parse-partial-sexp with the
fourth argument STOPBEFORE non-nil.

This STOPBEFORE causes the scanning to stop at any character which
begins a sexp.  A closing brace doesn't fit into this category.  The
scan therefore reaches EOL, and the code therefore falsely assumes there
are no non-syntactic-ws characters on that line.

I'm sure I can fix this today.

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2017-12-30 13:05 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-30  9:49 26.0.90: mark-defun problem in c-mode zhang cc
2017-12-30 10:30 ` Eli Zaretskii
2017-12-30 10:34   ` Alan Mackenzie
2017-12-30 12:01     ` beginning-of-defun-comments bug [was: Re: 26.0.90: mark-defun problem in c-mode] Alan Mackenzie
2017-12-30 12:53       ` Eli Zaretskii
2017-12-30 13:05         ` Alan Mackenzie [this message]
2018-01-03  4:51           ` Marcin Borkowski
2018-01-03 16:24             ` Alan Mackenzie
2018-01-05 14:55               ` zhang cc
2018-01-06 12:00                 ` Alan Mackenzie
2018-01-06 13:54                   ` zhang cc
2018-01-07  6:25                   ` Marcin Borkowski
2018-03-26  6:57               ` Marcin Borkowski
2017-12-30 15:43         ` Alan Mackenzie
2017-12-30 18:43           ` Stephen Leake
2017-12-31 10:55             ` Alan Mackenzie
2017-12-31  4:26           ` Stefan Monnier
2017-12-31 10:50             ` Alan Mackenzie

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