c++ 虚析构函数

class Base1 {
public:
Base1() { cout << "Base1::Base1 1"<<endl; };
Base1(int i, int j) :i(i), j(j) {
cout << "Base1::Base1 2"<<endl ;
};
~Base1() {
cout << "Base1::~Base1"<<endl;
}
void basemem() { cout << i <<","<< j<<endl; };
protected:
int i;
private:
int j;
};

struct public_derived : public Base1
{
public:
public_derived() { cout << "public_derived::public_derived 1" << endl; };
public_derived(int i, int j, int k) : Base1(i, j), k(k) { cout << "public_derived::public_derived 2" << endl; };
int use_base() { return i; }
~public_derived() { cout << "public_derived::~public_derived" << endl; };
protected:
int k;
};