C++知识积累：类继承中构造函数与析构函数的调用顺序问题

先来看单继承的情况，以类A为基类，类B为类A的派生类，试运行以下程序：

class A
{
public:
    A():age(1),name("ll")
    {
        cout<<"Class A Empty Constructor !"<<endl;
    }
    A(A &a)
    {
        cout<<"Class A Copy Constructor !"<<endl;
    }
    ~A()
    {
        cout<<"Class A Destructor !"<<endl;
    }
protected:
    string name;
    int age;
};
class B:public A
{
public:

    B()
    {
        cout<<"Class B Empty Constructor !"<<endl;
    }
    B(B &b)
    {
        cout<<"Class B Copy Constructor !"<<endl;
    }
    B(A &a)
    {
        cout<<"Class B Copy A Constructor !"<<endl;
    }
    ~B()
    {
        cout<<"Class B Destructor !"<<endl;
    }
};
int main()
{
    B b;
    cout<<"--------------------------------"<<endl;
    A a;
    cout<<"--------------------------------"<<endl;
    B b1(a);
    cout<<"--------------------------------"<<endl;
    B