#include<iostream>
using namespace std;
class A
{
public:
	A(int a1, int a2);
private:
	int a;
	int b;
};
A::A(int a1, int a2) :a(a1), b(a2)
{

}
class B
{
public:
	int a = 1;
	int b = 3;
};
int main()
{
	A a(1, 33);
	char*p = (char*)(&a);

	cout << (reinterpret_cast<B*>(p))->b;
	cin.get();
	return 0;
}

看起来内存结构一样。。就能够这样来操作