passing pointers using LuaBridge

[Moose <moose@...>]

Hi all,

I am making moderate progress integrating Lua into my C++ environment. 
After trying many different ways of wrapping C or C++ code I ended up 
with two candidates that seemed to suit my needs best. LuaBridge 
(https://github.com/vinniefalco/LuaBridge) and LuaWrapper 
(https://bitbucket.org/alexames/luawrapper).

I was able to create C++ wrappers for existing classes with both, and, 
inside my scripts, to create objects of those types and call methods 
upon them. So far so good. However, with both implementations I have 
failed to pass existing objects with C++ lifetime into the script.

With LuaBridge for example I do this (simplified):

int luaopen_mylib_1(lua_State *L) {

	using namespace luabridge;
	getGlobalNamespace(L)
		.beginNamespace("mylib")
			.addFunction ("testfree", testfree)
			.beginClass<MyClass>("MyClass")
				.addFunction("foo",   &MyClass::foo   )
			.endClass()
		.endNamespace();

	// quite like this interface btw.

	return 0;
}

... then ...

   using namespace luabridge;
   lua_State *L = luaL_newstate();
   luaL_openlibs(L);

   // and register the functions within that context
   luaopen_mylib_1(L);

   // create MyClass instance
   MyClass *p = new MyClass();
   setGlobal(L, p, "mc");     // a LuaBridge Method that pushes the 
pointer as
                                         // global userdata on the 
stack

   if (luaL_dofile(L, "luawrapper_reuse.lua")) {
		std::cerr << "Lua program returned an error: \n";
		std::cerr << lua_tostring(L, -1);
		std::cerr << std::endl;
		lua_close(L);
   }

   delete p;



All very straight forward.
Then in my script...

[[
print("Executing LuaBridge test")
mylib.testfree()
mc:foo()
]]

The method testfree() is being called all right. At least I see the 
output. But then, when I try to access the instance "mc", I get:

luawrapper_reuse.lua:6: attempt to index global 'mc' (a userdata value)


Despite the fact that I do everything by the book, exactly the way it 
is described in LuaBridges manual. Can anyone tell me what I do wrong? 
How can I access the object?
It seems like Lua does know it. A pointer by the name 'mc' has been 
pushed as userdata into the context, which is how I understand this is 
supposed to work. But why can I not de-reference it and call a method?
So close to the goal and yet all my efforts fail on this....

With that Test I use LuaJit 2.0 on Windows64 (MSVC9).


Help is much appreciated.

Thanks,
Moose.