condition_variable

static std::mutex m;
void worker(int& result, std::condition_variable& cv, int set) {
    std::this_thread::sleep_for(std::chrono::milliseconds(200));
    result = set;
    cv.notify_all();
}
void consumer(std::condition_variable& cv, int idx) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock);
    std::cout << "consumer #" << idx << " receive notification" << std::endl;
}
int main(int argc, char* argv[]) {
    int cnt = 0;
    std::condition_variable cv;
    std::thread t1(worker, std::ref(cnt), std::ref(cv), 1);
    std::thread t2(worker, std::ref(cnt), std::ref(cv), 2);
    std::thread t3(consumer, std::ref(cv), 3);
    std::thread t4(consumer, std::ref(cv), 4);
    std::thread t5(consumer, std::ref(cv), 5);
    std::thread t6(consumer, std::ref(cv), 6);
    std::thread t7(consumer, std::ref(cv), 7);
    std::thread t8(consumer, std::ref(cv), 8);
    t1.detach();
    t2.detach();
    t3.detach();
    t4.detach();
    t5.detach();
    t6.detach();
    t7.detach();
    t8.detach();
    {
        std::unique_lock<std::mutex> lock(m);
        cv.wait(lock);
        std::cout << cnt << std::endl;
    }
    while (true) {
        std::this_thread::sleep_for(std::chrono::milliseconds(200));
    }
    return 0;
}