Bug #54614 [Opn]: Trivial RE failure: /([^b]*a*)*$/
Edit report at http://bugs.php.net/bug.php?id=54614&edit=1
ID: 54614
Updated by: felipe@php.net
Reported by: php at richardneill dot org
Summary: Trivial RE failure: /([^b]*a*)*$/
Status: Open
Type: Bug
-Package: *Regular Expressions
+Package: PCRE related
Operating System: Linux
PHP Version: 5.3.6
Block user comment: N
Private report: N
New Comment:
Not a PHP bug.
Previous Comments:
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[2011-04-27 23:47:20] php at richardneill dot org
Sorry, my bad (sort of).
There is a genuine bug that affected longer regexps even with
backtrack.limit set
to 32M, which I saw on 5.3.2, but is now solved on 5.3.6.
Unfortunately, the test-case which I simplified for the bug-report
didn't
remember to set backtrack.limit (I thought I'd done it in php.ini, but
had
actually done it explicitly with ini.set in my original script). So the
test
case:
- works for backtrack.limit = 1M (on both 5.3.2 and 5.3.6)
- fails for the default 100k on both.
Either way, it's still something that, imho, should work on a default
install.
May I make a few suggestions:
* backtrack.limit should be raised by default, to at least 10M.
* backtrack.limit should default to 100M for the CLI version of PHP.
* validating bug reports is painful, partly because I had to spend some
extra
time tracking down the latest version of PHP and building it. This is
error-
prone. How about providing a sandboxed VM on bugs.php.net where we can
paste our
own code to check it? This would make it far easier to file correct bug
reports.
(it would take the reporter 3 minutes, rather than an hour).
------------------------------------------------------------------------
[2011-04-27 21:54:07] rasmus@php.net
With pcre.backtrack_limit = 1000000 this works fine for me on 5.3.6. Are
you sure
you increased the limit in the right place?
------------------------------------------------------------------------
[2011-04-27 21:15:34] php at richardneill dot org
A slightly simpler test case is:
$contents = "aaaaaaaab";
$search = '/(a*a*)*$/';
------------------------------------------------------------------------
[2011-04-27 18:43:02] php at richardneill dot org
Description:
------------
If I search in the string : 'aaaaaaaab'
with the RE: '/([^b]*a*)*$/'
then preg_replace fails with a backtrack-limit error. (error 2)
I have backtrack.limit configured to 32MB, so something is very wrong.
The example fails on several different PHP versions, CPU architectures
and Linux
Distros. However, using Perl for the same RE works fine.
Test script:
---------------
$contents = "aaaaaaaab";
$search = '/([^b]*a*)*$/';
$result = preg_replace($search,"x",$contents);
if ($result === NULL){
echo "preg failed, error is ".preg_last_error()."\n";
}else{
echo "success\n";
}
Expected result:
----------------
preg_replace shouldn't fail.
Actual result:
--------------
preg_replace returns NULL, and preg_last_error returns 2.
------------------------------------------------------------------------
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