GNU bug report logs - #58726
29.0.50; Bug in regexp matching with shy groups

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Package: emacs;

Reported by: Michael Heerdegen <michael_heerdegen <at> web.de>

Date: Sun, 23 Oct 2022 01:42:02 UTC

Severity: normal

Found in version 29.0.50

Done: Mattias Engdegård <mattiase <at> acm.org>

Bug is archived. No further changes may be made.

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From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: 58726 <at> debbugs.gnu.org
Subject: bug#58726: 29.0.50; Bug in regexp matching with shy groups
Date: Sun, 23 Oct 2022 03:41:25 +0200

Hello,

  (string-match-p "\\`\\(?:ab\\)*\\'" "a") ==> 0

That's wrong, the expected result is nil.  The language matched by that
regexp is {"", "ab", "abab", "ababab", ...}.

Changing to a non-shy group doesn't exploit the issue:

  (string-match-p "\\`\\(ab\\)*\\'" "a")  ==> nil

as expected.

I've been told (emacs-help, Bruno Barbier) that the problem exists at
least in emacs 27, emacs 28 and emacs 29.


TIA,

Michael.
This bug report was last modified 2 years and 267 days ago.

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