纯虚拟调用从构造函数和析构函数 [英] Pure virtual invocation from constructor and destructor

问题描述

C ++标准说，禁止从构造函数或析构函数调用纯虚函数。这是什么原因？为什么标准应该这样限制？

The C++ standard says that invoking a pure virtual function from a constructor or destructor is forbidden. What is the reason for this? Why should the standard place a restriction like this?

推荐答案

当一个类析构函数运行时，所有子类析构函数都有已经运行。调用由子类定义的虚方法是无效的，它的析构函数已经运行了。

At the point a class destructor is run, all subclass destructors have already been run. It would not be valid to call a virtual method defined by a subclass, for which its destructor has already run.

在构造函数中调用虚方法时存在类似的限制。您不能为其构造函数尚未运行的子类调用虚拟方法。

A similar restriction exists around calling virtual methods in constructors. You can't call a virtual method for a subclass whose constructor has not yet run.

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