C++11 关键字 thread

thread_local 线程本地变量

1. 需要在可访问的作用域中声明
2. 声明时可以初始化，但只有在线程中被使用时才实例化，随线程销毁时销毁

#include 
#include 
#include 
#include 
#include 

class Cls_A
{
    int data;
public:
    Cls_A(const int x):data{x}
    {
        std::cout << "Cls_A construct in thread:" << std::this_thread::get_id()<<" and data is "<< data << std::endl;
    }
    ~Cls_A()
    {
        std::cout << "Cls_A destruct in thread:" << std::this_thread::get_id() <
        ++data;
    }
    int get() const
    {
        return data;
    }
};

thread_local Cls_A x{21};

std::mutex mtx;

void func_0()
{
    std::lock_guard lock(mtx);
    x.add();
    std::cout << "thread:" << std::this_thread::get_id() << "'s x is " << x.get() << std::endl;
}

int main()
{
    std::cout << x.get() << std::endl;
    std::thread t1{func_0};
    std::thread t2{func_0};
    t1.join();
    t2.join();
    return 0;
}