C++中的类继承的问题

#include <iostream>

using namespace std;

static int x;

class A
{
public:
A() {x = 1;}

virtual ~A(){x = 2;}
virtual void foo() {x = 3;}
};

class B :public A
{
public:
B(){x = 4;}
virtual ~B(){x = 5;}
void foo(){x = 6;}
void bar(){foo();}
};

class C:public B
{
public:
C() {x = 7;}
virtual ~C(){x = 8;}
void foo() {x = 9;}
void bar(){foo();}
};

C testc;

void main(void)
{
A *testa = NULL;
B *testb = NULL;

testa = (A*)&testc;
cout << x << endl;
testa->foo();
cout << x << endl;

((B)testc).bar();

cout << x << endl;
testb = new B;
cout << x << endl;
testb->foo();
cout << x << endl;
delete testb;
cout << x << endl;
((B*)(&testc))->bar();
cout << x << endl;
testa = NULL;
cout << x << endl;
}

输出为：

7

9

2

4

6

2

9

9

第三个输出很奇怪，原来 是((B)testc).bar()，原来先转换成一个临时对象，调用bar后会析构，最终调用基类的析构函数

倒数第二个输出，虽然bar不是虚函数，但是当中调用了foo这个虚函数，还是会根据动态类型找到C的foo