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Bug #66172 Garbage collector won't collect circullar dependecy if SPL classes involved
Submitted: 2013-11-26 03:07 UTC Modified: 2017-01-02 12:19 UTC
From: aleksey at roave dot com Assigned: nikic (profile)
Status: Closed Package: Scripting Engine problem
PHP Version: 5.5.6 OS: Any
Private report: No CVE-ID: None
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From: aleksey at roave dot com
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 [2013-11-26 03:07 UTC] aleksey at roave dot com 
Description:
------------
This affects all versions with gc, 5.3 to 5.5
Tried script on http://3v4l.org/KmGDj

I can't tell what happens internally, but it looks like garbage collector will not detect and collect circular dependencies if there are SPL classes involved (i suspect other built-in classes are affected too)

Test script:
---------------
https://gist.github.com/Xerkus/7562464/raw/f6d0ff3f1fbc24a3a3ca99ac974571748103ab51/test.php

Expected result:
----------------
Memory stays at about the same level

Actual result:
--------------
Used memory grows constantly

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 [2013-11-26 03:22 UTC] aleksey at roave dot com 
Sorry, linked wrong test run
http://3v4l.org/21Tdf
 [2013-11-27 09:28 UTC] colder@php.net
-Status: Open +Status: Assigned -Assigned To: +Assigned To: colder
 [2013-11-27 15:23 UTC] colder@php.net 
I have a patch here: https://github.com/colder/php-src/commit/abf152b260dbcc1da1eb850c9f10098b812c67d4

It indeed affects any internal class with hidden (not property-based) state that is not exposed via get_gc, which includes most SPL classes.. This patch is only about SplHeaps/Priority Queues, I will need more time to generalize.
 [2017-01-02 12:19 UTC] nikic@php.net
-Status: Assigned +Status: Closed -Assigned To: colder +Assigned To: nikic
 [2017-01-02 12:19 UTC] nikic@php.net 
All cycle leaks for SPL data structures should be fixed in PHP 7.0. As PHP 5.6 is no longer actively supported I'm closing this issue.
 
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