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zend_list_addref and object resources

php.internals

Marshall A. Greenblatt

22 years ago

Hi,

I'm having a bit of a conundrum that maybe someone here can help me out with
:-).

When assigning an object resource to either 'getThis()' or 'return_value' as
shown below, is it necessary to manually increment the reference count?

For example, /ext/ming/ming.c (version 1.70) contains many code fragments
like the following where zend_list_addref() is used with 'getThis()', and
not used with 'return_value':

<snip ming.c:297>
ret = zend_list_insert(action, le_swfactionp);

object_init_ex(getThis(), action_class_entry_ptr);
add_property_resource(getThis(), "action", ret);
zend_list_addref(ret);
</snip>

<snip ming.c:1979>
ret = zend_list_insert(item, le_swfdisplayitemp);
object_init_ex(return_value, displayitem_class_entry_ptr);
add_property_resource(return_value, "displayitem", ret);
</snip>

Looking at earlier revisions of this file, it appears that usage of
zend_list_addref() with 'return_value' has been steadily decreasing.  There
is, however, one place where zend_list_addref() with 'return_value' is still
being called:

<snip ming.c:1686>
int ret = zend_list_insert(shape, le_swfshapep);

object_init_ex(return_value, shape_class_entry_ptr);
add_property_resource(return_value, "shape", ret);
zend_list_addref(ret);
</snip>

I can't find enough examples in other modules to feel confident that
zend_list_addref() with 'return_value' is a bad thing (some use it, some
don't), and my testing seems to show that everything works fine with or
without the explicit zend_list_addref() call for both 'return_value' and
'getThis()'.

That said, is there a "correct" way to handle reference counting with
'getThis()' and 'return_value' in this situation?

Thanks,
Marshall

Marshall A. Greenblatt

22 years ago

----- Original Message -----
From: "Marshall A. Greenblatt" <marshall@magpcss.com>
To: <internals@lists.php.net>
Sent: Monday, August 09, 2004 11:38 PM
Subject: [PHP-DEV] zend_list_addref and object resources


[snip]

> When assigning an object resource to either 'getThis()' or 'return_value'

as

> shown below, is it necessary to manually increment the reference count?
>
> For example, /ext/ming/ming.c (version 1.70) contains many code fragments
> like the following where zend_list_addref() is used with 'getThis()', and
> not used with 'return_value':
>
> <snip ming.c:297>
>  ret = zend_list_insert(action, le_swfactionp);
>
>  object_init_ex(getThis(), action_class_entry_ptr);
>  add_property_resource(getThis(), "action", ret);
>  zend_list_addref(ret);
> </snip>

[snip]

In answer to my own question:  No, at least not with PHP4.3.1.

<?php
/* Create an object with a resource and return via 'getThis()'. */
$foo = new myobj();
print_zval($foo);


/* Create an object with a resource and return via 'return_value'. */
$bar = getmyobj();
print_zval($bar);
?>

In either case, irregardless of whether zend_list_addref() is explicitly
called for the resource ID, output (via print_zval) is as follows:

Addr:[9F75D0] is_ref:[0] refcount:[2] Type:[OBJECT] Class:[myobj] Val:[
Name:[value] => Addr:[9F7798] is_ref:[0] refcount:[1] Type:[RESOURCE]
Val:[1]
]
Addr:[9F7638] is_ref:[0] refcount:[2] Type:[OBJECT] Class:[myobj] Val:[
Name:[value] => Addr:[9F79B8] is_ref:[0] refcount:[1] Type:[RESOURCE]
Val:[2]
]

If anyone is interested in playing with this, email me and I'll make the
source code available online.

- Marshall

Note: The print_zval function takes any type of variable and displays the
value, similar to print_r, but in a more useful debugging format.