GNU bug report logs - #78042
31.0.50; Improper sequence of `before/after-change-functions` calls

Previous Next

Full log

View this message in rfc822 format

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 78042 <at> debbugs.gnu.org
Subject: bug#78042: 31.0.50; Improper sequence of `before/after-change-functions` calls
Date: Fri, 25 Apr 2025 21:39:46 +0300

> From: Stefan Monnier <monnier <at> iro.umontreal.ca>
> Cc: 78042 <at> debbugs.gnu.org
> Date: Fri, 25 Apr 2025 12:37:34 -0400
> 
> > Sorry, I don't think I understand the problem.  Is the problem that we
> > have "nested" notifications, whereby you have
> >
> >   before-change-functions A1 B1
> >   before-change-functions A2 B2
> >   after-change-functions  A2 B2
> >   after-change-functions  A1 B1
> >
> > IOW, _any_ situation where we have nested pairs of notifications is
> > "breaking our promise"?
> 
> Yup: the `before-change-functions A2 B2` promises that there won't be
> any changes to the buffer outside of A2...B2 until the next
> `before-change-functions`.
> 
> > If so, how can that be avoided in principle in Emacs, given its
> > recursive nature, except by some mechanism which collects all the
> > notifications and rearranges them to "keep our promise"?
> 
> There is currently no attempt in the C code to solve this "by
> construction" or "by design".  Instead we fix the offenders as we bump
> into them.

I submit that we will never be able to solve all of them.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.