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Date: Fri, 29 Aug 2003 16:17:11 +0300
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Subject: Shared module problems (core dumps) (under apache 1.3)
From: andrey@php.net ("Andrey Hristov")

 Hi,
till today I had a big problem with my Apache 1.3 segfaulting when I try to
instantiate from a class. The class is declared in a C extesion (named
xml_parser.so, class name WebgateXMLParser). Few week after the
implementation it worked well since I just loaded the extension with dl() :
dl('xml_parser.so').
At some point I decided to include a check whether the module is loaded
(compiled statically) and in this case not to dl() it. Just around the time
I
implemented (in PHP) this check my Apache/PHP started to core. Sadly
I found the reason just today.
My check is this :
 if (!class_exists('WebgateXmlParser')) { // if it's built into the PHP
binary don't load
  dl('xml_parser.so');
 }// if
What happens? After the request is finished the module is unloaded - this
can easily be seen just
by doing a var_dump(get_loaded_extensions()); before the "if". However
PHP/Zend still thinks that
there is WebgateXmlParser class. Briefly : Zend DOES NOT unregister classes
on module unload.
Now you may imagine what happens when the extension is not loaded since Zend
Engine thinks that
the class exists (but it does not) and the code tries to instantiate an
object of the class - core dump.

IMO IT IS a bug that the class entries are not unregistered when the module
is unloaded after the request. I have not tried this but the same error may
apply to functions exported by a C extension and thus leading
to the same effect - crashes that are hard to explain.



Regards,
Andrey

P.S.
Yes, there is a workaround for my case : to check whether the module is
loaded but not checking whether the class exists.