ID: 50264 Updated by: j...@php.net Reported By: laszlo dot janszky at gmail dot com -Status: Open +Status: Bogus Bug Type: PCRE related Operating System: Windows XP PHP Version: 5.3.1 New Comment:
Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php Previous Comments: ------------------------------------------------------------------------ [2009-11-23 19:38:35] laszlo dot janszky at gmail dot com If it is not clear, by the test: the 8 tokens withBlock (M1) test string is: $test=' {display} {display} {display} {display} {display} {display} {display} {display} {/display} {/display} {/display} {/display} {/display} {/display} {/display} {/display} '; and the 8 tokens withoutBlock (M2) test string is: $test=' {display} {display} {display} {display} {display} {display} {display} {display} '; ------------------------------------------------------------------------ [2009-11-23 19:21:02] laszlo dot janszky at gmail dot com The leak is in relation with this http://bugs.php.net/bug.php?id=49333 Here is a simplyfied example with eight "withoutBlock" tokens: <?php ini_set('pcre.backtrack_limit', 40000); ini_set('pcre.recursion_limit', 1000); $pattern= '% {(\w+)(?:} (.*?(?:(?0).*?)*?) {/\1)?} %usDx'; $test=' {display} {display} {display} {display} {display} {display} {display} {display} '; preg_match_all($pattern,$test,$matches,PREG_SET_ORDER); var_dump($matches); ?> The basic syntax is: {withBlock}block{/withBlock} or {withoutBlock} As the {withBlock} opener part is of the same structure like the {withoutBlock}, it starts to collect the string after the {withoutBlock} to the backtrace. But for some kind of reason the {withoutBlock} backtrace eats up the memory superexponential, not linear like in the case of {withBlock}. A measured the memory usage with the simplyfied example. It was not superexponential, just exponential. I think cause I have in this example two capturing groups only, not a lot like in the original code. tokens M1[b] M2[b] LN(M2) 1 19 22 3,0910 2 53 115 4,7449 3 87 405 6,0039 4 121 1286 7,1593 5 155 3940 8,2789 6 189 11913 9,3854 7 223 35843 10,4869 8 257 107644 11,6204 M1 = 34 * N - 15 R^2 = 1 M2 = exp ( 1,1192 * N + 2,6669 ) R^2 = 0,9999 for the 3-8 part Btw. it's funny memory usage..................... ------------------------------------------------------------------------ [2009-11-22 18:53:14] laszlo dot janszky at gmail dot com If I remove the recursive part (?:\\}(?<block>.*?(?:(?0).*?)*?)\\{/(?P=function))? from the end of the regex, then it works fine... ------------------------------------------------------------------------ [2009-11-22 18:47:14] laszlo dot janszky at gmail dot com Description: ------------ I have a huge recursive regex (about 500bytes), which needs a lot of memory for backtrace. The regex matches on templates like {command1 arg1=$arg1 arg2=$arg2|modifier2 arg3="text"|modifier3:modarg31:modarg32} etc.... If I use the regex with preg_match_all, then the backtrace memory usage depends on the count of the commands superexponential. So: R^2 = 0,9977 (R^2 for trendline) ln ln M = 0,0787 * N + 1,9304 [M] = used backtrack memory in bytes [N] = number of command calls It don't think that more than 1Mb memory usage is normal for a 0.0002Mb string. The recursion memory usage is normal(under 1kb). I'm pretty disappointed because I can't use my template engine because of a badly written pcre engine. Reproduce code: --------------- $template1=' {display var=$link} {display var=$link} {display var=$link} {display var=$link} {display var=$link} {display var=$link} {display var=$link} {display var=$link} {display var=$link} {display var=$link} '; $template2=' {display var=$link} {display var=$link} {display var=$link} {display var=$link} test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test test '; $regex='%\\{(?<function>(?:\\w+))(?:(?<list>\\s(?:[\\w_]+(?:\\s[\\w_]+)*\\s)?(?:\\$\\w+(?:->\\w+|\\.\\w+)*|"(?:.*?)"|\\d+(?:\\.\\d+)?)(?:\\|\\w+(?::(?:\\$\\w+(?:->\\w+|\\.\\w+)*|"(?:.*?)"|\\d+(?:\\.\\d+)?))*)*(?:\\s[\\w_]+(?:\\s[\\w_]+)*\\s(?:\\$\\w+(?:->\\w+|\\.\\w+)*|"(?:.*?)"|\\d+(?:\\.\\d+)?)(?:\\|\\w+(?::(?:\\$\\w+(?:->\\w+|\\.\\w+)*|"(?:.*?)"|\\d+(?:\\.\\d+)?))*)*)*(?:\\s[\\w_]+(?:\\s[\\w_]+)*)?)|(?<hash>(?:\\s\\w+=(?:\\$\\w+(?:->\\w+|\\.\\w+)*|"(?:.*?)"|\\d+(?:\\.\\d+)?)(?:\\|\\w+(?::(?:\\$\\w+(?:->\\w+|\\.\\w+)*|"(?:.*?)"|\\d+(?:\\.\\d+)?))*)*)*))(?:\\}(?<block>.*?(?:(?0).*?)*?)\\{/(?P=function))?\\}%usD'; $one_Mb=1024*1024; $one_kb=1024; ini_set('pcre.backtrack_limit', $one_Mb); ini_set('pcre.recursion_limit', $one_kb); preg_match_all($regex,$template1,$matches1,PREG_SET_ORDER); preg_match_all($regex,$template2,$matches2,PREG_SET_ORDER); echo 'test1:<br />'; echo (!count($matches1)?'failed':'ok').'<br />'; echo 'test2:<br />'; echo (!count($matches2)?'failed':'ok').'<br />'; Expected result: ---------------- test1: ok test2: ok Actual result: -------------- test1: failed test2: ok ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=50264&edit=1
