#46790 [Com]: Memory leak with classes

From: Date: Sun, 07 Dec 2008 13:18:17 +0000
Subject: #46790 [Com]: Memory leak with classes
References: 1  Groups: php.bugs 
Request: Send a blank email to php-bugs+get-131715@lists.php.net to get a copy of this message 
 ID:               46790
 Comment by:       o_O_Tync at mail dot ru
 Reported By:      o_O_Tync at mail dot ru
 Status:           Feedback
 Bug Type:         Class/Object related
 Operating System: Win, FreeBSD
 PHP Version:      5.2.7
 New Comment:

>php.exe -v
PHP 5.3.0alpha4-dev (cli) (built: Dec  6 2008 17:07:05)
Copyright (c) 1997-2008 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2008 Zend Technologies

Without the 'this helps' line
>php.exe -f memleak.php
Mem: 1166 Kb

With the 'this helps' line
>php.exe -f memleak.php
Mem: 321 Kb

The problem remains


Previous Comments:
------------------------------------------------------------------------

[2008-12-07 07:13:01] lstrojny@php.net

Please try using this CVS snapshot:

  http://snaps.php.net/php5.3-latest.tar.gz
 
For Windows:

  http://windows.php.net/snapshots/



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

[2008-12-07 06:34:02] o_O_Tync at mail dot ru

Description:
------------
I've come across a memory leak: garbage collector failes to free memory
occupied by linked objects, such as:

$obj1->pair = $obj2; $obj2->pair = $obj1;

Below goes the problematic piece of code: over many iterations - it
occupies a lot of memory.

If we comment 'line1' or 'line2' or both - memory is okay (48 Kb), but
cross-linking reveals a bug (839 Kb) despite of explicit unsetting.
The commented 'this helps' line solves the problem.

Tested under WinXP, and FreeBSD 6.1 using the latest PHP 5.2.7

Reproduce code:
---------------
<?php
class Paired
	{
	/** Paired object
	 * @var Paired
	 */
	public $pair;
	}

for ($i=0;$i<2000;$i++)
	{
	$obj1 = new Paired; $obj2 = new Paired;
	$obj1->pair = $obj2; // 'line1'
	$obj2->pair = $obj1; // 'line2'
	// $obj1->pair = null; $obj2->pair = null; // this helps
	unset($obj1); unset($obj2); // Explicitly
	}

print 'Mem: '.floor(memory_get_usage()/1024).' Kb';
?>

Expected result:
----------------
Mem: 48 Kb

Actual result:
--------------
Mem: 839 Kb


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


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