Re: [Boost-users] Windows API callback, using boost::bind

Subject: Re: [Boost-users] Windows API callback, using boost::bind
From: John Dlugosz (JDlugosz_at_[hidden])
Date: 2010-10-29 13:31:10

> The common approach is to generate code that translates from the
> thiscall calling convention to stdcall.
> 
> There might be third party libraries that can do this, but I'm unsure
> if
> it's possible at all on x64, if that matters.

I have a free library that does this for 32-bit code.  It's fairly easy to translate from "thiscall" calling convention to "stdcall".  The same trick won't work for x64.  Generating an actual call to re-push the arguments needs to know more details about the number and type of arguments!  However, a typed thunk generator could be crafted for the specific signature needed.  You also need to allocate the thunk's memory in a page that was VirtualAlloc'ed to hold code (in 32-bit code you can just disable the feature), which complicates management of thunks as value objects.   I've not gotten around to it, and don't have an immediate need for it.  But I'd be happy to give some pointers if someone were writing such a thing.

> 
> The other common solutions is to have a global pointer to your instance
> and use that from a static member function, 

For real things I've encountered, the number of callbacks needed is limited to a small value known at compile time.  Using a fixed global or a small pool of individually written global wrappers is much simpler than anything else.  Hmm, using a numeric template argument it would be trivial to create a "pool" of any size N, without excessive source code.

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