虚拟继承+虚函数，含有虚函数的菱形虚拟继承

一、虚拟继承+虚函数

场景①：派生类没有自己的虚函数，只是继承基类的虚函数

我们看一个例子：

class Base{public:virtual void FunTest1(){cout << "Base::FunTest1()" << endl;}virtual void FunTest2(){cout << "Base::FunTest2()" << endl;}int _b;};class Derived :virtual public Base{public:virtual void FunTest1(){cout << "Derived::FunTest1()" << endl;}virtual void FunTest2(){cout << "Derived::FunTest2()" << endl;}int _d;};typedef void(*FunSrc)();void print(Base&b)//打印函数{FunSrc* pfun = (FunSrc*)(*(int*)&b);while (*pfun){(*pfun)();pfun++;}}int main(){Derived d;Derived& d1 = d;d._b = 1;d._d = 2;print(d);system("pause:");return 0;}

分析一下：

②派生类有自己的虚函数

class Base{public:virtual void FunTest1(){cout << "Base::FunTest1()" << endl;}virtual void FunTest2(){cout << "Base::FunTest2()" << endl;}int _b;};class Derived :virtual public Base{public:virtual void FunTest1(){cout << "Derived::FunTest1()" << endl;}virtual void FunTest2(){cout << "Derived::FunTest2()" << endl;}virtual void FunTest3(){cout << "Derived::FunTest3()" << endl;}int _d;};typedef void(*FunSrc)();void print(Base&b)//打印函数{FunSrc* pfun = (FunSrc*)(*(int*)&b);while (*pfun){(*pfun)();pfun++;}}void print(Derived&d)//打印函数{FunSrc* pfun = (FunSrc*)(*(int*)&d);while (*pfun){(*pfun)();pfun++;}}

分析一下：

总结：

1.同一个类的对象共用一张虚表；

2.派生类和基类各自的虚表。

二、菱形虚拟继承（含虚函数）

举个例子:

class B{public:virtual void FunTest1(){cout << "B::FunTest1()" << endl;}virtual void FunTest2(){cout << "B::FunTest2()" << endl;}int _b;};class C1 :virtual public B{public:virtual void FunTest1(){cout << "C1::FunTest1()" << endl;}virtual void FunTest3(){cout << "C1::FunTest3()" << endl;}int _c1;};class C2 :virtual public B{public:virtual void FunTest1(){cout << "C2::FunTest1()" << endl;}virtual void FunTest4(){cout << "C2::FunTest4()" << endl;}int _c2;};class D :public C1,public C2{public:virtual void FunTest1(){cout << "D::FunTest1()" << endl;}virtual void FunTest3(){cout << "D::FunTest3()" << endl;}virtual void FunTest5(){cout << "D::FunTest5()" << endl;}int _d;};

分析一下：

对于含有虚函数的菱形虚拟继承，我们要考虑的内容就比较复杂了，菱形虚拟继承存在多继承的，多继承的规则要把握好。虚拟继承包括偏移量表格。