CppCoreGuidelines CP.41 减少线程的创建和销毁

void worker(Message m)
{
    // process
}

void dispatcher(istream& is)
{
    for (Message m; is >> m; )
        run_list.push_back(new thread(worker, m));
}

Sync_queue<Message> work;

void dispatcher(istream& is)
{
    for (Message m; is >> m; )
        work.put(m);
}

void worker()
{
    for (Message m; m = work.get(); ) {
        // process
    }
}

void workers()  // set up worker threads (specifically 4 worker threads)
{
    joining_thread w1 {worker};
    joining_thread w2 {worker};
    joining_thread w3 {worker};
    joining_thread w4 {worker};
}