GNU bug report logs - #58158
29.0.50; [overlay] Interval tree iteration considered harmful

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From: Richard Stallman <rms <at> gnu.org>
To: Gerd Möllmann <gerd.moellmann <at> gmail.com>
Cc: eliz <at> gnu.org, 58158 <at> debbugs.gnu.org, monnier <at> iro.umontreal.ca
Subject: bug#58158: 29.0.50; [overlay] Interval tree iteration considered harmful
Date: Fri, 30 Sep 2022 21:57:36 -0400

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  > I think it simply can't be that what is basically walking a binary tree
  > requires such restrictions.

If we allow running complicated code during the tree walk, that would
be asking for trouble.  But if the operations done during the tree
walk are simple and written in C, it should be clear that there is no
possibility of this kind of a bug.  Isn't that the case?

  > > What has to do with overlays.  To name a few: overlay-at, overlays-in,
  > > next-overlay-change, previous-overlay-change, overlay-lists, ...

Those operations can be done in C with no risk of signaling an error.

That ought to be sufficient, as long as we don't need the code to be
reentrant.  If the code needs to be reentrant then we would have
to eliminate the "visited" flag.  But if we don't run Lisp code
during the tree-walk, we should not need it to be reentrant.

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)

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