Example code to go along with https://github.com/progschj/LuaBridge/commit/b0c51a91740011266b7281163fc92d26d3b04269

LuaBridgeSharedPtrExample.cpp

#include <iostream>
#include <memory>

#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>

#include <LuaBridge/LuaBridge.h>


namespace luabridge {
	// register shared_ptr as container
  	template <class T>
	struct ContainerTraits <std::shared_ptr<T> >
	{
		typedef T Type;

		static T* get (std::shared_ptr<T> const& c)
		{
			return c.get();
		}
	};
	// make sure shared_ptr isn't usable with not instrumented types
	template <class T>
	struct ContainerTraits2< std::shared_ptr<T> > { };
}

// class with shared_from_this that friends ContainerTraits2
class A : public std::enable_shared_from_this<A> {
public:
	friend class luabridge::ContainerTraits2< std::shared_ptr<A> >;

	A(int v) : value(v) { std::cout << "A::A(" << value << ")" << std::endl; }
	~A() { std::cout << "A::~A(" << value << ")" << std::endl; }

	int value;

	static void register_lua(lua_State *L)
	{
		using namespace luabridge;
		getGlobalNamespace (L)
		.beginNamespace ("test")
			.beginClass <A> ("A")
				.addConstructor<void(*)(int), std::shared_ptr<A> >()
			.endClass ()
		.endNamespace ();
	}

};

namespace luabridge {
	// second traits are able to obtain a shared_ptr from a raw pointer
	template <>
	struct ContainerTraits2< std::shared_ptr<A> >
	{
		static std::shared_ptr<A> getContainer(A *t)
		{
			return t->shared_from_this();
		}
	};
}

int main(int argc, char *argv[]) {
    int iarg;
    lua_State *L = luaL_newstate();

	luaL_openlibs(L);
	A::register_lua(L);
	{
		std::shared_ptr<A> a(new A(1));

		luabridge::setGlobal (L, a, "a");

		lua_getglobal(L, "a");
		std::shared_ptr<A> a2 = luabridge::Stack< std::shared_ptr<A> >::get(L,1);

		int s = luaL_dostring(L, "b = test.A(2)");
        	if(s != 0) {
            		std::cerr << "Error: " <<  lua_tostring(L, -1) << std::endl;
            		lua_pop(L, 1);
        	}

		lua_getglobal(L, "b");
		std::shared_ptr<A> b = luabridge::Stack< std::shared_ptr<A> >::get(L,1);

		s = luaL_dostring(L, "c = a");
        	if(s != 0) {
            		std::cerr << "Error: " <<  lua_tostring(L, -1) << std::endl;
            		lua_pop(L, 1);
        	}

		lua_getglobal(L, "c");
		std::shared_ptr<A> c = luabridge::Stack< std::shared_ptr<A> >::get(L,1);

	}

    lua_close(L);

    return 0;
}

You can replace

luabridge::Stack< std::shared_ptr<A> >::push(L, a);
lua_setglobal(L, "a");

with

luabridge::setGlobal (L, a, "a");

Did just that, thanks.