C++ 类构造函数初始化顺序

#include <iostream>
using namespace std;

class A {
private:
    int n1;
    int n2;
public:
    A(): n2(0), n1(n2 + 2){}
    void Print() {
        cout<<n1<<" "<<n2<<endl;
    }
};

int main() {
    A a;
    a.Print();
}

#include <iostream>

using namespace std;

class OBJ1
{
public:
    OBJ1(){ cout <<"OBJ1\n"; }
};

class OBJ2
{
public:
    OBJ2(){ cout <<"OBJ2\n"; }
};

class Base1
{
public:
    Base1(){ cout <<"Base1\n"; }
};

class Base2
{
public:
    Base2(){ cout <<"Base2\n"; }
};

class Base3
{
public:
    Base3(){ cout <<"Base3\n"; }
};

class Base4
{
public:
    Base4(){ cout <<"Base4\n"; }
};

class Derived :public Base1, virtual public Base2,
    public Base3, virtual public Base4
{
public:
    Derived() :Base4(), Base3(), Base2(),
        Base1(), obj2(), obj1()
    {
        cout <<"Derived ok.\n";
    }
protected:
    OBJ1 obj1;
    OBJ2 obj2;
};

int main()
{
    Derived aa;
    cout <<"This is ok.\n";
}