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Bug #5545 regular expression matching goes into almost infinite loop
Submitted: 2000-07-13 01:03 UTC Modified: 2000-07-13 03:28 UTC
From: elkan at cs dot ucsd dot edu Assigned:
Status: Closed Package: Scripting Engine problem
PHP Version: 4.0 Release Candidate 2 OS: Mandrake Linux 7.0r2
Private report: No CVE-ID: None
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From: elkan at cs dot ucsd dot edu
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 [2000-07-13 01:03 UTC] elkan at cs dot ucsd dot edu 
I am using 4.0.0 with Apache 1.3.12 and MySQL, all standard.
The following code works fine:

	$tpattern = ".*<big><b>(.*)</b></big>";
        if (eregi($tpattern,$text,$match)) {
                 $title = $match[1];

But adding .* at the end of the pattern, making

	$tpattern = ".*<big><b>(.*)</b></big>.*";

can take 41 seconds to run, measured using time().
Sometimes it gives the error message
	Fatal error: Maximum execution time of 30 seconds
	exceeded in /home/elkan/public_html/crawler.php on 		line 58

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 [2000-07-13 03:28 UTC] stas at cvs dot php dot net 
This is not a bug. You are just forcing regexp working too hard. Please take a good book on regular experssions (like Mastering Regular Experssions) and read about backtracking and how bad could it be.
 
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