GNU bug report logs - #57957
29.0.50; Native compilation hangs on cyclic lists

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Package: emacs;

Reported by: Lars Tveito <larstvei <at> ifi.uio.no>

Date: Tue, 20 Sep 2022 14:28:02 UTC

Severity: normal

Tags: confirmed

Merged with 67883, 69872

Found in versions 29.0.50, 29.1.90, 29.2

Done: Andrea Corallo <acorallo <at> gnu.org>

Bug is archived. No further changes may be made.

Full log

Message #28 received at 57957 <at> debbugs.gnu.org (full text, mbox):

From: Gerd Möllmann <gerd.moellmann <at> gmail.com>
To: Andrea Corallo <akrl <at> sdf.org>
Cc: Lars Ingebrigtsen <larsi <at> gnus.org>, Lars Tveito <larstvei <at> ifi.uio.no>,
 57957 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#57957: 29.0.50; Native compilation hangs on cyclic lists
Date: Thu, 22 Sep 2022 18:41:04 +0200

Andrea Corallo <akrl <at> sdf.org> writes:

>>>>From Common Lisp I can say that these functions expect a "tree",
>> i.e. not a circular list.
>
> Okay I tried an adhoc substitute but this is not the only place in the
> compiler not robust against cyclic lists, so more work will be needed.

The question is of course also how much effort circular lists deserve in
the compiler.  From my point of view, not too much because they aren't
very useful, in code at least.  And dealing with them costs runtime.

Maybe some places could use cl-list-length?  That function deals with
circular lists and returns nil then.  We could then refuse to compile.
This bug report was last modified 1 year and 49 days ago.

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