C++ Inheritance

最新推荐文章于 2024-09-19 14:42:21 发布

原创最新推荐文章于 2024-09-19 14:42:21 发布 · 660 阅读

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#inheritance #c++ #class #c #iostream #table

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本文探讨了C++中多重继承和虚继承的概念及其内存布局。通过具体示例，展示了不同继承方式下对象的内存组织形式及虚函数表的作用。

----------- Class A---------------

class A

{
public:
       virtual void foo1() { printf("in A::foo1()/n");};
       virtual void foo2() { printf("in A::foo2()/n"); }

public:
        A():a1('A') {};
        int a1;
};

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----------- Class B---------------

         A
       /
     B

class B : public A
{
public:
       virtual void foo1() { printf("in B::foo1()/n"); }
       virtual void foo2() { printf("in B::foo2()/n"); }

public:
       B():b1('B'),b2('B') {};
       int b1;
       int b2;
};

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[X+0xc]:0x42

----------- Class B (virtual inheritance)---------------

         A
       / (virtual)
     B

class B : virtual public A
{
public:
       virtual void foo1() { printf("in B::foo1()/n"); }
       virtual void foo2() { printf("in B::foo2()/n"); }

public:
       B():b1('B'),b2('B') {};
       int b1;
       int b2;
};

[X+0x0]:0x21640 #virtual table of class B
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[X+0xc]:0x21640+0x10 #virtual table of class A
[X+0x10]:0x41

----------- Class D --------------

         A
       /    /
     B     C
       /   /
         D

class C : public A

{
public:
virtual void foo1() { printf("in C::foo1()/n"); }
virtual void foo2() { printf("in C::foo2()/n"); }

public:
       C():c1('C'),c2('C'),c3('C') {};
       int c1;
       int c2;
       int c3;
};

class D : public B, public C
{
public:
virtual void foo1() { printf("in D::foo1()/n"); }
virtual void foo2() { printf("in D::foo2()/n"); }

public:
       D():d1('D'),d2('D'),d3('D'),d4('D') {};
       int d1;
       int d2;
       int d3;
       int d4;
};

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----------- Class D (virtual inheritance)---------------

         A
       /    / (virtual)
     B     C
       /   /
         D

class C : virtual public A

{
public:
virtual void foo1() { printf("in C::foo1()/n"); }
virtual void foo2() { printf("in C::foo2()/n"); }

public:
       C():c1('C'),c2('C'),c3('C') {};
       int c1;
       int c2;
       int c3;
};

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[X+0x4]:0x42
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[X+0xc]:0x21b20+0x18
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---------------------------------------------------------------------------------------------------------

#include <iostream>

using namespace std;

class A
{
public:
       virtual void foo1() { printf("in A::foo1()/n"); };
       virtual void foo2() { printf("in A::foo2()/n"); }

public:
        A():a1('A') {};
        int a1;
};

//class B : virtual public A
class B : public A
{
public:
       virtual void foo1() { printf("in B::foo1()/n"); }
       virtual void foo2() { printf("in B::foo2()/n"); }

public:
       B():b1('B'),b2('B') {};
       int b1;
       int b2;
};

//class C : virtual public A
class C : public A
{
public:
       virtual void foo1() { printf("in C::foo1()/n"); }
       virtual void foo2() { printf("in C::foo2()/n"); }

public:
       C():c1('C'),c2('C'),c3('C') {};
       int c1;
       int c2;
       int c3;
};

class D : public B, public C
{
public:
       virtual void foo1() { printf("in D::foo1()/n"); }
       virtual void foo2() { printf("in D::foo2()/n"); }

public:
       D():d1('D'),d2('D'),d3('D'),d4('D') {};
       int d1;
       int d2;
       int d3;
       int d4;
};

int main()
{
#define X D

X d;
int * p = (int *)&d;
int size = sizeof (X)/4;
for (int i=0;i<size;i++)
if ((*(p+i)) > (*p))
printf("[X+0x%x]:0x%x+0x%x/n", i*4,(*p), (*(p+i)) - (*p));
else
printf("[X+0x%x]:0x%x/n", i*4,(*(p+i)));
}