bug#53680: Endless loop in peculiar case of string-match and string-match-p 27.02 and 28.0.50

[Andreas Schwab]

On Feb 01 2022, Lars Ingebrigtsen wrote:

> I guess the · are supposed to be spaces, so it's:
>
> (string-match
>  "[\r\t ]*implements[\r\t ]+\\([\r\t ]*[\\a-zA-Z_0-9_]+,?\\)+[\r\t ]*{$"
>  "ariable implements \\Magento\\Framework\\Event\\OberserverInterface\r{\r    
> public function __construct()\r ")
>
> And I can reproduce this on master, too.  Is it a problem with excessive
> backtracking, perhaps?

It sure is.  The nesting of the + operator without proper anchoring
makes the search space explode.

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Andreas Schwab, schwab@linux-m68k.org
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