Re: [boost] Fwd: [Thread] Solution to conflict with MFC?

Subject: Re: [boost] Fwd: [Thread] Solution to conflict with MFC?
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2011-04-28 02:41:32

Thorsten Ottosen <thorsten.ottosen_at_[hidden]> writes:

> Den 27-04-2011 18:21, Anthony Williams skrev:
>> Thorsten Ottosen<thorsten.ottosen_at_[hidden]>  writes:
>>
>>> Den 27-04-2011 17:13, Anthony Williams skrev:
>>>> Thorsten Ottosen<thorsten.ottosen_at_[hidden]>   writes:
>
>>> Is there any possibility that the initialization of this pointer
>>> in tss_pe.cpp can be made dynamic based on some parameter
>>> passed to the code? It would be really cool if we could just say
>>>
>>> #define BOOST_THREAD_DISABLED_DLL_CALLBACK 1
>>> #include<boost/thread.hpp>
>>>
>>> in the code that needs it. AFAICR, we can have global data in headers
>>> as long as it is inside some template.
>>
>> For the DLL callback to be called automatically, there must be an extern
>> "C" global variable called _pRawDllMain, which must be statically
>> initialized to point to the callback function.
>>
>> I don't see how you could put that in a header without risking >
>> multiple
>> definition errors --- the header that initialized it would have to be
>> included exactly once across the whole project. Failure to include it
>> anywhere would mean that the init function would not be linked.
>
> I searched the source directory to locate this variable. Is
>
> extern BOOL (WINAPI * const _pRawDllMain)(HANDLE, DWORD,LPVOID);
>
> not just a declaration of a variable located somewhere else?

As you've written it, it would be. In the real code there's actually an initializer:

extern BOOL (WINAPI * const _pRawDllMain)(HANDLE, DWORD, LPVOID)=&dll_callback;

which means that it is a const variable with external linkage.

> If so, we only need to put the initialization of this variable
> in a header.

But doing so would yield multiple initialization errors.

>> I haven't tried it, but I think that if the application defines
>> boost::tss_cleanup_implemented() then tss_pe.cpp will not get linked
>> from the library, so the DLL callback will not be linked, and the MFC
>> one should therefore work. Of course, you will then need to ensure that
>> boost::on_thread_exit() is called when every thread exits to avoid
>> leaking memory and/or resources.
>
> yeah, that won't work well. Then it's far better to include a seperate
> .cpp file.

Anyone care to try the attached file?

Anthony
-- 
Author of C++ Concurrency in Action     http://www.stdthread.co.uk/book/
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