C ++是=原子的静态变量初始化吗? [英] C++ is static variable initialization with = atomic?

问题描述

Meyers Singleton取决于以下事实:局部静态变量初始化为原子.

The Meyers Singleton depends on the fact that local static variable initialization is atomic.

我正在构建类似的东西，但我希望单例实际上是许多派生类型之一.基类 getInstance()方法应调用一个将返回适当类型的工厂.

I'm building something similar but I want the singleton to actually be one of a number of derived types. The base class getInstance() method should call a factory that will return the appropriate type.

我的第一个想法是

static Foo *instance = FooFactory(...);

8.5p2， N3337 似乎表明这严格是初始化，而不是初始化和赋值，我认为这意味着整个语句都是原子的.这样对吗?

8.5p2 of N3337 seems to indicate that this is strictly initialization and not initialization and assignment and I interpret that to mean the entire statement is atomic. Is this correct?

如果不是，则声明

static Foo *instance(FooFactory(...));

与众不同吗?

编辑8.5.2-> 8.5.p2

Edit 8.5.2 -> 8.5.p2

推荐答案

8.5.2是"[dcl.init.string]"，似乎并不相关.我认为您的意思是8.5 para2.

8.5.2 is "[dcl.init.string]", and doesn't seem to be relevant. I think you mean 8.5 para2.

是的，这是严格的初始化(特别是复制初始化-参见8.5 para14).

Yes, this is strictly initialization (specifically copy initialization - see 8.5 para14).

如果声明在函数内部，那么，如所链接问题的答案所示，一切都很好.

If the declaration is inside a function, then, as the answer to the linked question shows, all is well.

但是，如果这是命名空间范围内的静态变量，那么我看不到任何需要初始化才能保证线程安全的东西.(这仅是初始化创建线程的问题，但我敢打赌.)

However if this is a static variable at namespace scope, then I can't see anything which requires the initialization to be thread safe. (That is only a problem if initialization creates threads - but I bet it does.)

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