C++中通过指针修改类内私有成员变量 & 类的大小

#include <iostream>

using namespace std;

class T{
public:
	void set(int value){ 
		a = value;
	}
	int getValue(){
		return a;
	}
	virtual void X(){
		return;
	}
private:
	int a;
};

class K{
public:
	void set(int value){
		a = value;
	}
	int getValue(){
		return a;
	}
	void X(){
		return;
	}
private:
	int a;
};

int main(){

	T t;
	t.set(5);
	printf("%d\n", t.getValue());
	T *a;
	a = &t;
	*(int *)a = 4;

	printf("%d\n", t.getValue());

	printf("%d %d\n", sizeof(T),sizeof(int));
	printf("%d %d\n", sizeof(K), sizeof(int));

	return 0;
}