Better Callback

main.cpp

#include <algorithm>
#include <string>
#include <vector>
#include <type_traits>
#include <functional>
#include <iostream>

template<typename T>
using fn = T*;

void foo(int i, fn<void(int, void*)> callback, void* data) {
	std::cout << i << '\n';
	callback(i, data);
}


template<typename Function, typename T>
void good_foo(int i, Function callback, T&& data) {
	struct callback_data {
		Function callback;
		T&& data;
	};
	auto bar = callback_data{callback, std::forward<T>(data)};
	foo(i, [](int i, void* data) {
			auto tmp = reinterpret_cast<callback_data*>(data);
				tmp->callback(i, tmp->data);
			}, &bar);
}

int main() {
	int x = 5;
	good_foo(3, [&x](int i, std::string str) {std::cout << i << ", " << str << ", " << x << '\n';}, "blub");
}