标准的原子布尔值和原子标记之间的区别 [英] difference between standard's atomic bool and atomic flag
问题描述
我不知道std::atomic变量，但是知道标准提供的std::mutex(很奇怪！).然而，有一件事引起了我的注意:标准提供了两种看似相同的原子类型(对我而言)，如下所示:
I wasn't aware of the std::atomic variables but was aware about the std::mutex (weird right!) provided by the standard; however one thing caught my eye: there are two seemingly-same (to me) atomic types provided by the standard, listed below:
std::atomic_flag包含以下说明:
std::atomic_flag是原子布尔类型.与std::atomic的所有专门技术不同，它保证是无锁的.与std::atomic<bool>不同，std::atomic_flag不提供加载或存储操作.
std::atomic_flagis an atomic boolean type. Unlike all specializations ofstd::atomic, it is guaranteed to be lock-free. Unlikestd::atomic<bool>,std::atomic_flagdoes not provide load or store operations.
我不明白.是否不能保证std::atomic<bool>是无锁的?那不是原子的还是什么?
which I fail to understand. Is std::atomic<bool> not guaranteed to be lock-free? Then it's not atomic or what?
那么两者之间有什么区别，什么时候应该使用呢?
So what's the difference between the two and when should I use which?
推荐答案
std :: atomic bool类型不保证无锁吗?
std::atomic bool type not guranteed to be lock-free?
正确. std::atomic可以使用锁来实现.
Correct. std::atomic may be implemented using locks.
那不是原子的还是什么?
then it's not atomic or what?
std::atomic是原子的，无论是否已使用锁实现.保证std::atomic_flag无需使用锁即可实现.
std::atomic is atomic whether it has been implemented using locks, or without. std::atomic_flag is guaranteed to be implemented without using locks.
那么两个黑白有什么区别
So what's the difference b/w two
除无锁保证外，主要区别在于:
The primary difference besides the lock-free guarantee is:
std::atomic_flag不提供加载或存储操作.
std::atomic_flagdoes not provide load or store operations.
什么时候应该使用哪个?
and when should I use which?
通常，当需要原子布尔变量时，将要使用std::atomic<bool>. std::atomic_flag是可用于实现自定义原子结构的低级结构.
Usually, you will want to use std::atomic<bool> when you need an atomic boolean variable. std::atomic_flag is a low level structure that can be used to implement custom atomic structures.
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