atomic

1、atomic 简介

https://blog.youkuaiyun.com/zxc024000/article/details/100767211

2、C++ 并行编程之memory_order

https://www.cnblogs.com/zifeiye/p/8194949.html

3、

std::atomic::compare_exchange_weak

bool compare_exchange_weak (T& expected, T val,
           memory_order sync = memory_order_seq_cst) volatile noexcept;
bool compare_exchange_weak (T& expected, T val,
           memory_order sync = memory_order_seq_cst) noexcept;

bool compare_exchange_weak (T& expected, T val,
           memory_order success, memory_order failure) volatile noexcept;
bool compare_exchange_weak (T& expected, T val,
           memory_order success, memory_order failure) noexcept;

       当前值与期望值相等时，修改当前值为设定值，返回true
        当前值与期望值不等时，将期望值修改为当前值，返回false
        这个函数可能在满足true的情况下仍然返回false，所以只能在循环里使用，否则可以使用它的strong版本