C++ 是否可以确定指针是否指向有效对象?

C++ Is it possible to determine whether a pointer points to a valid object?(C++ 是否可以确定指针是否指向有效对象?)

问题描述

我正在学习 C++ 并阅读 C++ Primer.有一个问题我想知道答案:

I'm learning C++ and reading C++ Primer. There's a question I would like to know the answer:

给定一个指针p，你能判断p是否指向一个有效的对象吗?如果是这样，如何?如果没有，为什么不呢?

Given a pointer p, can you determine whether p points to a valid object? If so, how? If not, why not?

推荐答案

不，你不能.为什么?因为维护关于什么构成有效指针和什么无效的元数据会很昂贵，而且在 C++ 中，您不需要为不想要的东西付费.

No, you can't. Why? Because it would be expensive to maintain meta data about what constitutes a valid pointer and what doesn't, and in C++ you don't pay for what you don't want.

并且您不希望检查指针是否有效，因为您知道指针来自哪里，或者因为它是您的代码的私有部分您控制，或者因为您在面向外部的合同中指定了它.

And you don't want to check whether a pointer is valid, because you know where a pointer comes from, either because it's a private part of your code that you control, or because you specified it in your external-facing contracts.

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