为什么简单的可复制类需要析构函数必须是微不足道的 [英] Why trivial copyable class require the destructor must be trivial

问题描述

基于C ++标准。 普通可复制类定义如下：

Base on the C++ standard. The trivial copyable class are define as following:

根据9/5，

A trivially copyable class is a class that:
- has no non-trivial copy constructors (12.8),
- has no non-trivial move constructors (12.8),
- has no non-trivial copy assignment operators (13.5.3, 12.8),
- has no non-trivial move assignment operators (13.5.3, 12.8), and
- has a trivial destructor (12.4).

据我理解，平凡可复制类按位复制。
所以直觉和理由需要平凡析构函数，这与位元复制无关。

By my understanding, the trivially copyable class is which can be copied by bitwise copied. So what's the intuition and reason to require trivial destructor which is unrelated to the bitwise copy.

推荐答案

原因很简单。简单地可复制意味着它是有效和定义的行为，将一个对象A复制到另一个B的顶部。显然，B的析构函数不会被调用，因此它必须是微不足道的。

The reason is simple enough. Trivially copyable means that it is valid and defined behaviour to copy one object A over the top of another B. Obviously the destructor for B will not be called, so it has to be trivial.

在N3797 3.8 / 4有一个对象生命周期的描述，似乎覆盖了这种情况。然而，如果程序不依赖于析构函数的副作用，则可能存在关于重用存储和不调用非平凡析构函数的漏洞。

There is a description of object lifetime at N3797 3.8/4 which appears to cover the situation. However, there could be a loophole regarding reuse of storage and non-calling of non-trivial destructor provided the program does not depend on side effects of the destructor.

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