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Date: Wed, 30 Jul 2003 02:03:49 +0900
To: Magnus Maatta <magnus@php.net>
Cc: internals@lists.php.net
Message-ID: <20030730020349.0b036b9b.moriyoshi@at.wakwak.com>
In-Reply-To: <20030729135239.1251bcab.magnus@php.net>
References: <20030729135239.1251bcab.magnus@php.net>
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Subject: Re: [PHP-DEV] Memory leaks in PHP_4_3 and HEAD
From: moriyoshi@at.wakwak.com (Moriyoshi Koizumi)

On Tue, 29 Jul 2003 13:52:39 +0200
Magnus Maatta <magnus@php.net> wrote:

> <?php
> class a {
>     var $items = array();
>     function a() {
>     }
> 
> }
> class b {
>     var $a;
>     function b(&$a) {
>         $this->a = &$a;
>     }
> }
> $a = new a();
> for ($i = 0; $i <= 4; $i++) {
>     $a->items[] = new b($a);
> }
> print_r($a);
> ?>
> 
> 
> With PHP5:
>             [4] => b Object
>                 (
>                     [a] => a Object
>  *RECURSION*
>                 )
> 
>         )
> 
> )
> /opt/dev/php/php5/Zend/zend_hash.c(374) :  Freeing 0x4153718C (35 bytes), script=24811.php
> Last leak repeated 4 times
> /opt/dev/php/php5/Zend/zend_hash.c(233) :  Freeing 0x41537130 (37 bytes), script=24811.php
> Last leak repeated 5 times
> /opt/dev/php/php5/Zend/zend_API.c(677) :  Freeing 0x415370DC (32 bytes), script=24811.php
> /opt/dev/php/php5/Zend/zend_hash.c(154) : Actual location (location was relayed)
> Last leak repeated 5 times
> /opt/dev/php/php5/Zend/zend_execute.c(3037) :  Freeing 0x41537078 (44 bytes), script=24811.php
> /opt/dev/php/php5/Zend/zend_API.c(676) : Actual location (location was relayed)
> Last leak repeated 5 times
> /opt/dev/php/php5/Zend/zend_objects.c(95) :  Freeing 0x41537034 (12 bytes), script=24811.php
> Last leak repeated 5 times
> /opt/dev/php/php5/Zend/zend_execute.c(3036) :  Freeing 0x41536FF0 (16 bytes), script=24811.php
> Last leak repeated 5 times
> /opt/dev/php/php5/Zend/zend_variables.c(123) :  Freeing 0x41538EE8 (32 bytes), script=24811.php
> /opt/dev/php/php5/Zend/zend_hash.c(154) : Actual location (location was relayed)
> /opt/dev/php/php5/Zend/zend_execute.c(793) :  Freeing 0x41538E84 (44 bytes), script=24811.php
> /opt/dev/php/php5/Zend/zend_variables.c(122) : Actual location (location was relayed)
> Last leak repeated 1 time
> 
> 
> PHP4:
>             [4] => b Object
>                 (
>                     [a] => a Object
>                         (
>                             [items] => Array
>  *RECURSION*
>                         )
> 
>                 )
> 
>         )
> 
> )
> /opt/dev/php/php4/Zend/zend_hash.c(406) :  Freeing 0x081F009C (35 bytes), script=24811.php
> Last leak repeated 4 times
> /opt/dev/php/php4/Zend/zend_hash.c(178) :  Freeing 0x081EFFF4 (32 bytes), script=24811.php
> Last leak repeated 6 times
> /opt/dev/php/php4/Zend/zend_API.c(594) :  Freeing 0x081EFF94 (44 bytes), script=24811.php
> /opt/dev/php/php4/Zend/zend_API.c(582) : Actual location (location was relayed)
> Last leak repeated 5 times
> /opt/dev/php/php4/Zend/zend_execute.c(1975) :  Freeing 0x081EFF54 (12 bytes), script=24811.php
> Last leak repeated 5 times
> /opt/dev/php/php4/Zend/zend_hash.c(262) :  Freeing 0x081EFEA4 (37 bytes), script=24811.php
> Last leak repeated 5 times
> /opt/dev/php/php4/Zend/zend_execute.c(774) :  Freeing 0x081F1454 (44 bytes), script=24811.php
> /opt/dev/php/php4/Zend/zend_variables.c(122) : Actual location (location was relayed)
> Last leak repeated 1 time

That's a known problem. As of the current engine implementation,
circular referencing is just inevitable and will end up with lots of leaks.
This couldn't be a big deal unless you are trying to make a long-living
application with a reference-count-based scripting language.
(But it can be prevented with some trick IMO)

http://msdn.microsoft.com/library/en-us/vbcon98/html/vbcondealingwithcircularreferences.asp

Hope this helps.

Moriyoshi