C++11 STL 容器和线程安全
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C++11 STL containers and thread safety
提问by ?imon Tóth
I have trouble finding any up-to-date information on this.
我很难找到任何关于此的最新信息。
Do C++11 versions of STL containers have some level of thread safety guaranteed?
C++11 版本的 STL 容器是否有一定程度的线程安全保证？
I do expect that they don't, due to performance reasons. But then again, that's why we have both std::vector::operator[]and std::vector::at.
由于性能原因，我确实希望它们不会。但话又说回来，这就是为什么我们同时拥有std::vector::operator[]和的原因std::vector::at。
采纳答案by Jonathan Wakely
Since the existing answers don't cover it (only a comment does), I'll just mention 23.2.2 [container.requirements.dataraces] of the current C++ standard specificationwhich says:
由于现有的答案没有涵盖它（只有评论可以），我将仅提及当前C++ 标准规范的23.2.2 [container.requirements.dataraces]，其中说：
implementations are required to avoid data races when the contents of the contained object in different elements in the same sequence, excepting
vector<bool>, are modified concurrently.
当
vector<bool>同时修改同一序列中不同元素中包含的对象的内容时，需要实现来避免数据竞争，除了。
i.e. it's safe to access distinct elements of the same container, so for example you can have a global std::vector<std::future<int>>of ten elements and have ten threads which each write to a different element of the vector.
即访问同一个容器的不同元素是安全的，例如，您可以拥有std::vector<std::future<int>>十个元素的全局和十个线程，每个线程写入向量的不同元素。
Apart from that, the same rules apply to containers as for the rest of the standard library (see 17.6.5.9 [res.on.data.races]), as Mr.C64's answersays, and additionally [container.requirements.dataraces] lists some non-const member functions of containers that can be called safely because they only return non-const references to elements, they don't actually modify anything (in general any non-const member function must be considered a modification.)
除此之外，与标准库的其余部分相同的规则适用于容器（参见 17.6.5.9 [res.on.data.races]），正如Mr.C64 的回答所说，另外还有 [container.requirements.dataraces]列出了一些可以安全调用的容器的非常量成员函数，因为它们只返回对元素的非常量引用，它们实际上并没有修改任何东西（通常任何非常量成员函数都必须被视为修改。）
回答by Mr.C64
I think STL containers offer the following basic thread-safety guarantee:
我认为 STL 容器提供以下基本的线程安全保证：
simultaneous readsof the sameobject are OK
simultaneous read/writesof differentobjects are OK
同时读取的的同一个对象都OK
同时读/写操作的不同对象确定
But you have to use some form of custom synchronization (e.g. critical section) if you want to do something different, like e.g. simultaneous writes on the same object.
但是如果你想做一些不同的事情，比如在同一个对象上同时写入，你必须使用某种形式的自定义同步（例如临界区）。
回答by NoSenseEtAl
No. Check out PPL or Intel TBB for thread safe STL-like containers.
否。查看 PPL 或 Intel TBB 以获取线程安全的 STL 类容器。
Like others have noted they have usual "multiple reader thread safety" but that is even pre C++11. Ofc this doesnt mean single writer multiple readers. It means 0 writers. :)
就像其他人指出的那样，他们通常具有“多读取器线程安全性”，但这甚至是 C++11 之前的内容。Ofc 这并不意味着单个作者多个读者。这意味着 0 个作者。:)
