helloworld.cpp

// Clearly the best hello world out there.
#define _ATL_ATTRIBUTES 1
#define _WINDLL 1
#include <atlbase.h>
#include <atlcom.h>
#include <string.h>
#include <comdef.h>
#include <string>
#include <fstream>
#include <iostream>

[module(name = "HelloWorld")];

[object, uuid("08FA02D2-21F4-11E8-B467-0ED5F89F718B"), library_block]
__interface IMessageFactory : IUnknown {
	// interesting it doesnt allow me to use std::string as a param
	[id(0)] void InternalPrintToConsole(BSTR *str);
};

[coclass, uuid("883F0C9E-21F5-11E8-B467-0ED5F89F718B")]
class MessageFactory : public IMessageFactory {

private:

	void InternalPrintToConsole(BSTR *str) {
		std::wstring wstr;
		wstr.assign(reinterpret_cast<WCHAR *>(*str));
		std::wcout << wstr << std::endl;
	}

public:
	MessageFactory() {
	}

	~MessageFactory() {
	}

	void PrintStringToConsole(_bstr_t str) {
		this->InternalPrintToConsole(&str.GetBSTR());
	}
};

MessageFactory *CreateMessageFactory() {
	CComObject<MessageFactory> *msg_fac;
	if (SUCCEEDED(CComObject<MessageFactory>::CreateInstance(&msg_fac))) {
		return msg_fac;
	}

	std::ifstream fail_msg("Unable to create message factory!");
	fail_msg.exceptions(fail_msg.failbit);
}

int main(int argc, char **argv) {
	try {
		if (SUCCEEDED(CoInitialize(NULL))) {
			MessageFactory *message_factory = CreateMessageFactory();
			_bstr_t hello_str("Hello World!");
			message_factory->PrintStringToConsole(hello_str);
		} else {
			std::ifstream fail_msg("CoInitalize failed!");
			fail_msg.exceptions(fail_msg.failbit);
		}
	}
	catch (std::exception &ex) {
		std::cout << ex.what() << std::endl;
	}
	return 0;
}

Where is AddRef and Release. This program leaks memory.

COM makes me twitch.

Put your VC projcet full, please. On Vc2017 community console app do not compile.

Note that usage of ATL attributes is deprecated and produces warning C4467.

I was doing this in C#.