C++虚继承和普通继承实现测试对比记录

1.重复继承的普通继承和虚继承实现代码

1.1普通重复继承测试代码实现：

//普通的重复继承实现栗子：
class Base
{
public:
    Base(): m_a(1), m_b("Base"){ cout << "Base()" << endl; };
    ~Base() {};
 
private:
    int m_a;
    char m_b[64];
};
 
class Sub1: public Base
{
public:
    Sub1() : m_a1(101), m_b1("Sub1") { cout << "Sub1()" << endl; };
    ~Sub1() {};
 
private:
    int m_a1;
    char m_b1[64];
};
 
class Sub2 : public Base
{
public:
    Sub2() : m_a2(102), m_b2("Sub2") { cout << "Sub2()" << endl; };
    ~Sub2() {};
 
private:
    int m_a2;
    char m_b2[64];
};
 
class SubSub : public Sub2, public Sub1
{
public:
    SubSub() { cout << "Sub2()" << endl; };
    ~SubSub() {};
};
 
void Func_virtualSubClass()
{
    std::cout << "Func_virtualSubClass()!\n";
    Base base;
    std::cout << &base << "; size:" << sizeof(base) << endl;
    Sub1 sub1;
    std::cout << &sub1 << "; size:" << sizeof(sub1) << endl;
    Sub2 sub2;
    std::cout << &sub2 << "; size:" << sizeof(sub2) << endl;
    SubSub subSub;
    std::cout << &subSub << "; size:" << sizeof(subSub) << endl;
}

1.2.虚继承测试代码实现：

//虚继承重复继承实现栗子
class Base
{
public:
    Base(): m_a(1), m_b("Base"){ cout << "Base()" << endl; };
    ~Base() {};
 
private:
    int m_a;
    char m_b[64];
};
 
class Sub1: public virtual Base
{
public:
    Sub1() : m_a1(101), m_b1("Sub1") { cout << "Sub1()" << endl; };
    ~Sub1() {};
 
private:
    int m_a1;
    char m_b1[64];
};
 
class Sub2 : public virtual Base
{
public:
    Sub2() : m_a2(102), m_b2("Sub2") { cout << "Sub2()" << endl; };
    ~Sub2() {};
 
private:
    int m_a2;
    char m_b2[64];
};
 
class SubSub : public Sub2, public Sub1
{
public:
    SubSub() { cout << "Sub2()" << endl; };
    ~SubSub() {};
};
 
void Func_virtualSubClass()
{
    std::cout << "Func_virtualSubClass()!\n";
    Base base;
    std::cout << &base << "; size:" << sizeof(base) << endl;
    Sub1 sub1;
    std::cout << &sub1 << "; size:" << sizeof(sub1) << endl;
    Sub2 sub2;
    std::cout << &sub2 << "; size:" << sizeof(sub2) << endl;
    SubSub subSub;
    std::cout << &subSub << "; size:" << sizeof(subSub) << endl;
}

2.重复继承的测试结果：

2.1.普通继承的重复继承代码运行结果：

 

2.2.虚继承的重复继承代码运行结果：

 3.测试结果数据对比总结：

 虚继承于多继承相比，Sub1，Sub2的头部Base数据变成4字节的值，而Base的数据在Sub1，Sub2数据之后，且两个数据之间多了4字节的cc值，类似分割符，这导致虚继承的Sub1，Sub2的数据大小比普通继承的多了16个字节。然后SubSub子类中确实只有一份Base。