#44463 [Bgs]: preg_match_all makes extra matches on empty alternatives

[php at sameprecision dot org]

 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] [EMAIL PROTECTED]

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] [EMAIL PROTECTED]

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] => 
        )

)



------------------------------------------------------------------------


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Edit this bug report at http://bugs.php.net/?id=44463&edit=1