虚拟继承情况下的 vtable [英] vtable in case of virtual inheritance

问题描述

在虚拟继承的情况下，vtable 有什么用(或者为什么需要 vtable)?在这种情况下，这个 vtable 指向什么.

What is the use of vtable (or why is vtable required ) in case of virtual inheritance ? what does this vtable points to in this case.

示例:

class A
{
    void show()
    { }
};

class B : virtual A
{
    void disp()
    { }
};

在上面的例子中，B 类的大小是 8 个字节.这意味着 B 类的 vptr 指向一个 Vtable.这个 vtable 指向什么.

In the above example the size of class B is 8 bytes. which means class B has vptr pointing to a Vtable. What does this vtable point to .

推荐答案

vtable 是在 C++ 中实现 virtual 关键字的最常见方式——任何使用 virtual 关键字将为它创建一个 vtable，并且该类的每个实例都将包含一个指向该(单个)vtable 的指针.vtable 包含有关对象动态类的信息(以支持 dynamic_cast 和 typeinfo)以及有关该类的虚拟基类和函数所在位置的信息.

A vtable is the most common way of implementing the virtual keyword in C++ -- any class that uses the virtual keyword will have a vtable created for it and every instance of that class will contain a pointer to that (single) vtable. The vtable contains information on the dynamic class of the object (to support dynamic_cast and typeinfo) as well as information as to where virtual base classes and functions of the class are located.

在这种特定情况下，B 的 vtable 可能只包含动态类信息，因为 A 没有数据成员或虚函数.

In this specific case, the vtable for B will likely contain just dynamic class info, as A has no data members or virtual functions.

这篇关于虚拟继承情况下的 vtable的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！