使用优化器构建和销毁局部变量 [英] Local variables construction and destruction with optimizer involved

问题描述

如果我有此代码：

class A { ... };
class B { ... };

void dummy()
{
    A a(...);
    B b(...);
    ...
}

我知道变量 a 和 b 将以反向分配顺序销毁（ b ，然后 a ）;但是我可以确定优化器永远不会交换 a 和 b 的分配和构造？或者我必须使用 volatile 才能执行它吗？

I know that variables a and b will be destroyed in reverse allocation order (b will be destroyed first, then a); but can I be sure that the optimizer will never swap the allocation and construction of a and b? Or I must use volatile to enforce it?

推荐答案

是任何可观察的副作用（即读取和写入 volatile 对象和调用I / O函数） a 的任何副作用以及 a 的任何副作用， b 需要在需要之前发生。

The only guarantees are that any observable side effects (that is, reads and writes to volatile objects and calls to I/O functions) of the construction of a will happen before any observable side effects of the construction of b, and any side effects of a required by b will happen before they are needed.

很难想象为什么你需要更严格的排序但是使对象 volatile 将确保 a 在初始化 b ，但是在 a 完成之前，构造函数中的一些代码仍可能发生。

It's hard to imagine why you would need a stricter ordering than that, but making the objects volatile will ensure that a is completely initialised before initialising any part of b, although some code from the constructor could still happen before a is complete.

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