/*

std::lock_guard:更方便线程对于互斥量的上锁操作

std::lock_guard:在定义一个lock_guard时上锁，保证在析构或者异常时解锁

*/

#include <iostream>       // std::cout

#include <thread>         // std::thread

#include <mutex>          // std::mutex, std::lock_guard

#include <stdexcept>      // std::logic_error

std::mutex mtx;

void print_even (int x) {

    if (x%==) std::cout << x << " is even\n";

    else throw (std::logic_error("not even"));

}

void print_thread_id (int id) {

    try {

        // using a local lock_guard to lock mtx guarantees unlocking on destruction / exception:

        std::lock_guard<std::mutex> lck (mtx);//对mtx上锁，保证在析构时解锁

        print_even(id);

    }

    catch (std::logic_error&) {

        std::cout << "[exception caught]\n";

    }

}

int main ()

{

    std::thread threads[];

    // spawn 10 threads:

    for (int i=; i<; ++i)

        threads[i] = std::thread(print_thread_id,i+);

    for (auto& th : threads) th.join();

    getchar();

    return ;

}