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Date: Tue, 20 Jan 2004 14:36:50 +0100
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Subject: solution for DL's using atexit()
From: abies@php.net (Ard Biesheuvel)

Hello group,

I'm looking for a way to fix http://bugs.php.net/26968. This bug is 
caused by the underlying client .so using atexit() to register a cleanup 
function. As the library is unloaded before process shutdown, the 
atexit() stack no longer contains a valid reference when it is called, 
resulting in a segfault.

IMO there are three ways to fix this:
- Use some linker magic to redirect the call to atexit() to a wrapper 
function that effectively nulls it, and call the cleanup function 
ourselves in the MSHUTDOWN function. I'm not sure if this is possible, 
so any help is appreciated.

- Disallow unloading of the PHP module. I'm not sure if this is a good 
idea, but it seems to be the most portable solution, and the most 
unintrusive, because it will only affect those who actually use the module.

- Link the main binary to the client .so instead of just the PHP module. 
This will make sure that the cleanup function is present when exit() is 
called, but it kind of defeats the purpose of using shared modules in 
the first place.

Of course, the best solution would be to nuke the atexit() call from the 
client .so, but since this problem has been around for so long, in both 
Interbase and Firebird, I'm afraid it's something we will have to deal 
with ourselves.

-- 
Ard