#include <condition_variable>
#include <iostream>
#include <mutex>
#include <thread>

#include <unistd.h>

std::condition_variable v;
std::mutex m;

int main()
{
	std::thread t([]
		{
			{
				std::unique_lock<std::mutex> l(m);
				v.wait(l);
			}

			usleep(1000 * 1000);
			std::cout << 42 << '\n';
		});

	t.detach();
	v.notify_one();
}