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bug#53680: Endless loop in peculiar case of string-match and string-matc
From: |
Lars Ingebrigtsen |
Subject: |
bug#53680: Endless loop in peculiar case of string-match and string-match-p 27.02 and 28.0.50 |
Date: |
Tue, 01 Feb 2022 13:16:30 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
Andreas Schwab <schwab@linux-m68k.org> writes:
> It sure is. The nesting of the + operator without proper anchoring
> makes the search space explode.
Yup. So something like
(string-match
"[\r\t ]*implements\\([\r\t ]+[\\a-zA-Z_0-9_]+,?\\)+[\r\t ]*{$"
"ariable implements \\Magento\\Framework\\Event\\OberserverInterface\r{\r
public function __construct()\r ")
won't have the same explosion (and indeed finished immediately).
So I don't think this is an Emacs bug, just a very tough regexp to
match. There's been some talk about replacing Emacs' regexp motor with
something that has better backtracking characteristics, but I don't
recall if anybody has actually made any moves to make that happen.
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no