前言

std::lock_guard类是C++11新加入的特性，它是一个mutex包装器，提供了一种方便的RAII风格机制，该包装器在构造时自动绑定传入的mutex并加锁，在其析构函数中解锁，从而实现在作用域块的持续时间内拥有mutex而无需手动解锁，从而大大减少了死锁的可能性。

使用示例

#include <thread>
#include <mutex>
#include <iostream>
 
int g_i = 0;
std::mutex g_i_mutex;  // protects g_i
 
void safe_increment()
{
    const std::lock_guard<std::mutex> lock(g_i_mutex);
    ++g_i;
 
    std::cout << "g_i: " << g_i << "; in thread #"
              << std::this_thread::get_id() << '\n';
 
    // g_i_mutex is automatically released when lock
    // goes out of scope
}
 
int main()
{
    std::cout << "g_i: " << g_i << "; in main()\n";
 
    std::thread t1(safe_increment);
    std::thread t2(safe_increment);
 
    t1.join();
    t2.join();
 
    std::cout << "g_i: " << g_i << "; in main()\n";
}