void_sucks.cc

#include <chrono>
#include <tuple>

template <typename Duration = typename std::chrono::steady_clock::duration, typename F>
auto time (F&& f)
{
	using result_type = std::tuple <decltype (std::forward <F> (f) ()), Duration>;

	auto start = std::chrono::steady_clock::now ();
	decltype (auto) result = std::forward <F> (f) ();
	auto stop = std::chrono::steady_clock::now ();
	auto duration = std::chrono::duration_cast <Duration> (stop - start);

	return result_type {std::forward <decltype (result)> (result), duration};
}


#include <iostream>
#include <thread>

int foo ()
{
	std::this_thread::sleep_for (std::chrono::seconds {1});
	return 42;
}

void bar ()
{
	std::this_thread::sleep_for (std::chrono::seconds {2});
}

int main ()
{
	std::cout << std::get <1> (time <std::chrono::seconds> (foo)).count () << " s\n";
//	std::cout << std::get <1> (time <std::chrono::seconds> (bar)).count () << " s\n";
}