c++ - 为什么 pA、pB、pC 不相等？

Question

考虑下面的程序

 #include<iostream>
 using namespace std;
 class ClassA
{
public:
    virtual ~ClassA(){};
    virtual void FunctionA(){};

};

class ClassB
{
 public:
    virtual void FunctionB(){};
};



class ClassC : public ClassA,public ClassB
{

};

void main()
{
    ClassC aObject;
    ClassA* pA = &aObject;
    ClassB* pB = &aObject;
    ClassC* pC = &aObject;

    cout<<"pA = "<<pA<<endl;
    cout<<"pB = "<<pB<<endl;
    cout<<"pC = "<<pC<<endl;

}

pA,pB,pC应该是相等的，结果却是

pA = 0031FD90

pB = 0031FD94

pC = 0031FD90

为什么 pB = pA + 4？当我改变时

class ClassA
{
public:
    virtual ~ClassA(){};
    virtual void FunctionA(){};

};
class ClassB
{
 public:
    virtual void FunctionB(){};
};

到

class ClassA
{
};

class ClassB
{
};

结果是

pA = 0030FAA3

pB = 0030FAA4

pC = 0030FAA3

pB = pA + 1?

Answer 1

多重继承的对象有两个合并的子对象。我会猜测编译器将其中一个指针指向内部对象。