Subsystem Registration/Initialization

main.cpp

#include <iostream>
#include "module.h"

class MyModule : public Module {
	DECLARE_MODULE(Module::M_TYPE_ONE);
public:
	MyModule() {}
};

REGISTER_MODULE(MyModule);

int main() {
	printf("Hello, World\n");
	return 0;
}

module.cpp

#include "module.h"

Module *Module::instances[] = {};

void Module::registerModule(Module* instance) {
	auto type = instance->getModuleType();
  
  // NOTE: warn for overwritting
	
  instances[type] = instance;
}

module.h

#pragma once

#define DECLARE_MODULE(type) \
    public: \
		ModuleType getModuleType() const final { return type; }

#define REGISTER_MODULE(className) \
	namespace { \
		Module* __CreateModule##className() { \
			return new className(); \
		} \
		class __register##className { \
		public: \
			__register##className() { \
				Module::registerModule(__CreateModule##className()); \
			} \
		}; \
		__register##className __g_instance##className; \
	}

class Module {
public:
	enum ModuleType {
		M_TYPE_ONE,
		M_COUNT,
	};
	
public:
	// NOTE: this causes memory leaks.
	// Either use std::unique_ptr or handle destruction of pointers in instances[]
	virtual ~Module() {}
	virtual ModuleType getModuleType() const = 0;

	static void registerModule(Module* instance);

private:
	static Module* instances[M_COUNT];
};