ID: 34530
User updated by: php at clayst dot com
Reported By: php at clayst dot com
Status: Bogus
Bug Type: PCRE related
Operating System: Windows XP Pro
PHP Version: 4.4.0
New Comment:
There is no need to be nasty, particularly since you have no idea what
I did and did not do and in fact your deductions are wrong on both
counts.
I am a developer myself and I know better than to submit a bug report
without trying to see if someone else found the same thing first. You
have the advantage of knowing about the prior reports which make make
the similarities obvious. I did not.
I searched the bugs database several times using the advanced search
page and several different sets of keywords and other conditions. I
did not find anything that looked like this bug. I also reviewed each
of the reports that the system pulled up on my initial submission as
potentially similar bugs and found nothing that matched.
I also read the Pattern Syntax and preg_match pages of the manual,
multiple times in fact, and have read them many times before. I saw
several statements that explain about various types of loops, stack
space, etc. Some of them might apply but there is no way to tell
which, if any, do apply.
More generally, IMO PHP should not fail silently and relatively
randomly (in this case depending on the length of an input to a
function) due to some kind of overflow condition. In the software I
write I'd consider that to be a bug, whether it occurred in an external
library I chose to use or in my own code. If a limitation can't be
worked around that's completely fine and not unusual, but IMO running
into it should produce an error, not silence. PHP developers might
make a different choice and decide that silent failure in this case is
within their design parameters but then that should be documented. I
don't see that it is.
Previous Comments:
------------------------------------------------------------------------
[2005-09-16 21:02:10] [EMAIL PROTECTED]
Thank you for not searching the bug database before submitting yet
another bogus bug report about this issue.
Read about the limitations in PCRE library here:
http://www.pcre.org/pcre.txt
This is not PHP bug, just PCRE library's limitation.
(also mentioned in the manual, if you had bothered reading it)
------------------------------------------------------------------------
[2005-09-16 19:27:39] php at clayst dot com
Description:
------------
A regular expression which involves some unnecessary extra loops in
execution will give the proper result (a match) with a given input
string but will fail to match when it should if the input is one
character longer.
In the example, the pattern is intended to match a string which
contains:
(1) An optional substring consisting of one or more groups of word
characters separated by dashes, with the entire substring (if present)
terminated by a period; followed by
(2) A required substring consisting of one or more groups of word
characters separated by dashes.
The 'good' pattern shown does this properly. The 'bad' pattern
incorrectly makes the dashes between substrings optional -- i.e.
there's an extra '?" after the '-' in both portions of the pattern.
This error makes the pattern inefficient as there are many possible
matching substrings, but I believe it should still match a simple alpha
string. In fact it fails to match if the input string is more than 20
characters long.
Reproduce code:
---------------
<?php
$goodpattern = '/^((\w+(-\w+)*)\.)?(\w+(-\w+)*)$/';
$badpattern = '/^((\w+(-?\w+)*)\.)?(\w+(-?\w+)*)$/';
$string1 = str_repeat('a', 20);
$string2 = str_repeat('a', 21);
print('Good pattern, 20 characters: ' . preg_match($goodpattern,
$string1) . "\n");
print('Good pattern, 21 characters: ' . preg_match($goodpattern,
$string2) . "\n");
print('Bad pattern, 20 characters: ' . preg_match($badpattern,
$string1) . "\n");
print('Bad pattern, 21 characters: ' . preg_match($badpattern,
$string2) . "\n");
?>
Expected result:
----------------
All matches should return a 1 because they all match the given string.
Actual result:
--------------
The first three matches return a 1 but the last returns a 0:
Good pattern, 20 characters: 1
Good pattern, 21 characters: 1
Bad pattern, 20 characters: 1
Bad pattern, 21 characters: 0
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=34530&edit=1
