Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:16301
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
To: "'Derick Rethans'" <derick@derickrethans.nl>
Cc: "'Marcus Brg'" <helly@php.net>, "'Andi Gutmans'" <andi@zend.com>,
	"'PHP Developers Mailing List'" <internals@lists.php.net>
Date: Fri, 27 May 2005 17:06:53 +0400
Message-ID: <000001c562bc$f781a690$8202a8c0@thinkpad>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Importance: Normal
In-Reply-To: <Pine.LNX.4.62.0505271404140.2796@localhost>
Subject: RE: Another Interesting Reference Issue
From: dmitry@zend.com ("Dmitry Stogov")
References: <Pine.LNX.4.62.0505271404140.2796@localhost>

Hi Derick,

One for global $tree.

One for stack.

One for local $node.

= 3

What is wrong?

Thanks. Dmitry.

> -----Original Message-----
> From: Derick Rethans [mailto:derick@derickrethans.nl] 
> Sent: Friday, May 27, 2005 4:21 PM
> To: dmitry@zend.com
> Cc: Marcus Brg; Andi Gutmans; PHP Developers Mailing List
> Subject: Another Interesting Reference Issue
> 
> 
> Hello,
> 
> I encountered a strange increase of the refcount with the following 
> script:
> 
> <?php
> 	error_reporting(E_ALL);
> 	$tree = array (
> 		1 => 'one',
> 		2 => 'two',
> 		3 => 'three'
> 	);
> 
> 	function &find_node($key, &$node)
> 	{
> 		xdebug_debug_zval('node');
> 		$item =& $node[$key];
> 		return $item;
> 	}
> 
> 	$node =& find_node(3, $tree);
> 	$node = 'drie';
> 
> The xdebug_debug_zval() function looks up the given symbol in 
> the symbol 
> table, and it prints it's refcount/is_ref value too (unlike the 
> debug_zval_dump() function available in PHP which actually modifies 
> those values). Logically you expect the refcount of $node to 
> be 2 (once 
> through the global var $tree, and once as local variable 
> $node. But the 
> refcount actually seems to be 3.
> 
> I've been tracing things in the engine and found the following places 
> where the refcount of this variable is modified (file/line 
> nos are from 
> php 5.0-dev):
> 
> Old value = 1
> New value = 2
> zend_send_ref_handler (execute_data=0xbfffd410, 
> opline=0x85f5440, op_array=0x85f0b64) at 
> /dat/dev/php/php-5.0dev/Zend/zend_execute.c:3077
> 3077            zend_ptr_stack_push(&EG(argument_stack), varptr);
> (gdb) bt
> #0  zend_send_ref_handler (execute_data=0xbfffd410, 
> opline=0x85f5440, op_array=0x85f0b64) 
>     at /dat/dev/php/php-5.0dev/Zend/zend_execute.c:3077
> #1  0x0831de66 in execute (op_array=0x85f0b64) at 
> /dat/dev/php/php-5.0dev/Zend/zend_execute.c:1415
> 
> 
> Old value = 2
> New value = 3
> 0x0831c192 in zend_assign_to_variable_reference (result=0x0, 
> variable_ptr_ptr=0x85f74c8, value_ptr_ptr=0x85e4b8c, Ts=0x0) 
> at /dat/dev/php/php-5.0dev/Zend/zend_execute.c:262
> 262                     value_ptr->refcount++;
> (gdb) bt
> #0  0x0831c192 in zend_assign_to_variable_reference 
> (result=0x0, variable_ptr_ptr=0x85f74c8, 
> value_ptr_ptr=0x85e4b8c, Ts=0x0)
>     at /dat/dev/php/php-5.0dev/Zend/zend_execute.c:262
> #1  0x083227d7 in zend_recv_handler (execute_data=0xbfffd1a0, 
> opline=0x85f63bc, op_array=0x85f7a18)
>     at /dat/dev/php/php-5.0dev/Zend/zend_execute.c:3109
> #2  0x0831de66 in execute (op_array=0x85f7a18) at 
> /dat/dev/php/php-5.0dev/Zend/zend_execute.c:1415
> 
> It does not matter if it's passed by reference or not - the value is 
> always 3 inside the function. What is the reason for this?
> 
> regards,
> Derick
> 
> -- 
> Derick Rethans
> http://derickrethans.nl | http://ez.no | http://xdebug.org
> 
>