#44463 [Bgs]: preg_match_all makes extra matches on empty alternatives
| From: | php at sameprecision dot org | Date: | Mon, 17 Mar 2008 23:25:40 +0000 |
| Subject: | #44463 [Bgs]: preg_match_all makes extra matches on empty alternatives | ||
| References: | 1 | Groups: | php.bugs |
| Request: | Send a blank email to php-bugs+get-123406@lists.php.net to get a copy of this message | ||
ID: 44463
User updated by: php at sameprecision dot org
Reported By: php at sameprecision dot org
Status: Bogus
Bug Type: PCRE related
Operating System: irrelevant
PHP Version: 5.2.5
New Comment:
I am querying PCRE developers about it...
A global search SHOULD end if the last match matched a end of subject
assertion...
What is really happening is that at the end of the subject string, a
global search performs another test--if the regex matches empty string,
it produces this additional match... That is ambiguous.
Previous Comments:
------------------------------------------------------------------------
[2008-03-17 23:19:22] felipe@php.net
Well, at least isn't a PHP bug.
However, seems to me that the $ is matching twice...
File a bug in the PCRE bug repository:
http://bugs.exim.org/enter_bug.cgi?product=PCRE
------------------------------------------------------------------------
[2008-03-17 22:49:25] php at sameprecision dot org
Why would you expect three matches for a,a ?
------------------------------------------------------------------------
[2008-03-17 22:41:00] felipe@php.net
This result is expected.
Using pcretest:
PCRE version 7.5-RC2 2007-12-27
re> /(a|)(,|$)/g
data> a,
0: a,
1: a
2: ,
0:
1:
2:
data> a,a
0: a,
1: a
2: ,
0: a
1: a
2:
0:
1:
2:
Thanks.
------------------------------------------------------------------------
[2008-03-17 22:13:54] php at sameprecision dot org
Description:
------------
Performing a global match with empty alternative in subpattern followed
by $ alternative in subpattern results in "extra" match.
In the example below, I believe that preg_match_all should match the
second 'a' in the first subpattern, match the end of subject assertion
in the second subpattern and flag the global search as over.
I've tried this with php5.2.5/pcre7.3 on linux.
Reproduce code:
---------------
$regex = '/(a|)(,|$)/';
echo preg_match_all($regex, 'a,', $m1, PREG_SET_ORDER)."\n";
print_r($m1);
echo preg_match_all($regex, 'a,a' ,$m2, PREG_SET_ORDER)."\n";
print_r($m2);
Expected result:
----------------
2
Array
(
[0] => Array
(
[0] => a,
[1] => a
[2] => ,
)
[1] => Array
(
[0] =>
[1] =>
[2] =>
)
)
2
Array
(
[0] => Array
(
[0] => a,
[1] => a
[2] => ,
)
[1] => Array
(
[0] => a
[1] => a
[2] =>
)
)
Actual result:
--------------
2
Array
(
[0] => Array
(
[0] => a,
[1] => a
[2] => ,
)
[1] => Array
(
[0] =>
[1] =>
[2] =>
)
)
3
Array
(
[0] => Array
(
[0] => a,
[1] => a
[2] => ,
)
[1] => Array
(
[0] => a
[1] => a
[2] =>
)
[2] => Array
(
[0] =>
[1] =>
[2] =>
)
)
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=44463&edit=1