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Date: Mon, 31 Mar 2003 20:18:25 +0200
To: Rob Richards <rrichards@digarc.com>
Cc: php-dev <internals@lists.php.net>
Message-ID: <20030331181825.GB32131@schnuffel.thieso.net>
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Subject: Re: [PHP-DEV] modules and registering destructors
From: thies@thiesos.org ("Thies C. Arntzen")

On Sun, Mar 30, 2003 at 04:34:36PM -0500, Rob Richards wrote:
> My questions for the other day seem a lot off. After going through modules
> much more, I need someone to either confirm or explain a little more on how
> resources within a module are destroyed. What I am seeing stepping through
> the code is the following:
> 
> a module loaded from the ini file destroys its resources in the reverse
> order that they are created via the script.
> 
> a module loaded from a dl command destroys resources in the order that they
> are registered in the PHP_MINIT_FUNCTION via
> zend_register_list_destructors_ex.
> 
> The memory leaks I seem to be seeing then would be due to the fact that
> there are some dependencies on the resource destructions, which would mean
> that the destructors would need to be defined in the order they should be
> destroyed in (to support loading via dl).
> 
> Is correct? If not can someone shed a little more light on this?

    using dl() is generally not as "good" as loading extensions via
    php.ini.

> 
> The problem I am stepping through is in the domxml. php_free_xml_doc is the
> first destructor registered, so when the extension is loaded via the dl
> command, php_free_xml_doc is the first destructor called, leaving the other
> resources (node references, etc..) which were created in the script to crash
> when they get called to be destroyed since xmlFreeDoc was already called.

    i was the guy that requested the destructors to be called in
    reverse order of creation, but i have never invstigated what
    happens if extensions are loaded via dl().

> 
> Any info on how the destructors work in the 2 different scenarios would be
> greatly helpful.

    they shouldn't IMHO. if you could prepare a patch that fixes
    this i'm sure it'll be discussed here. but as not too many
    ppls actually think that dl() is a GoodFunction(tm) don't
    expect that anyone will "jump on" you problem just 'cause you
    reported it.

    so - my advice: a) include domxml in your php-build -or- b)
    load the shared lib via php.ini. if you _have_ to use dl()
    during your script (which will always be waaay slower than a
    or b) you will have to either c) fix the problem yourself and
    propose a patch or d) find someone who does that for you.


    my 2c,
    tc