C++虚函数指针和虚函数表推导原理

#include 
#include 

using namespace std;


class CAnimal;


typedef void (CAnimal::*PFN_FUNC)(void);

class CAnimal {
public:
	// 定义两个成员函数指针分别指向两个函数
	PFN_FUNC m_pfnEat;
	PFN_FUNC m_pfnBark;
	CAnimal(){
		this->m_pfnEat = &CAnimal::Eat;
		this->m_pfnBark = &CAnimal::Bark;
	}
	void Eat(){
		cout << "Animal Eat()" << endl;
	}
	void Bark() {
		cout << "Animal Bark()" << endl;
	}
};

class CCat :public CAnimal {
public:
	CCat() {
		this->m_pfnEat = (PFN_FUNC)&CCat::Eat;
		this->m_pfnBark = (PFN_FUNC)&CCat::Bark;
	}
	void Eat() {
		cout << "喵吃老鼠" << endl;
	}
	void Bark() {
		cout << "我们一起学喵叫" << endl;
	}
};

class CMouse :public CAnimal {
public:
	CMouse() {
		this->m_pfnEat = (PFN_FUNC)&CMouse::Eat;
		this->m_pfnBark = (PFN_FUNC)&CMouse::Bark;
	}
	void Eat() {
		cout << "老鼠吃奶酪" << endl;
	}
	void Bark() {
		cout << "老鼠吱吱叫" << endl;
	}
};

int main()
{
	{
		CAnimal* aryAnimals[] = {
			new CCat,
			new CMouse,
			new CMouse
		};

		for(int i = 0; i < sizeof(aryAnimals)/sizeof(aryAnimals[0]);i++){
			
			
			(aryAnimals[i]->*aryAnimals[i]->m_pfnEat)();
			(aryAnimals[i]->*aryAnimals[i]->m_pfnBark)();
		}

		for (int i = 0; i < sizeof(aryAnimals) / sizeof(aryAnimals[0]); i++) {
			delete aryAnimals[i];
		}
	}
	system("pause");
	return 0;
}



#include 
#include 

using namespace std;


class CAnimal;


typedef void (CAnimal::*PFN_FUNC)(void);

class CAnimal {
public:
	// 定义一个函数指针 指向保存所有函数地址的数组
	PFN_FUNC* __vfptr;
	CAnimal(){
		this->__vfptr = __vtable_animal;
	}
	void Eat(){
		cout << "Animal Eat()" << endl;
	}
	void Bark() {
		cout << "Animal Bark()" << endl;
	}

	// 全局函数指针数组
	static PFN_FUNC __vtable_animal[2];
};

// 静态变量初始化
PFN_FUNC CAnimal::__vtable_animal[2] = { &CAnimal::Eat,&CAnimal::Bark };

class CCat :public CAnimal {
public:
	CCat() {
		// 修改函数指针的指向  指向自己的函数地址表
		this->__vfptr = __vtable_cat;
	}
	void Eat() {
		cout << "喵吃老鼠" << endl;
	}
	void Bark() {
		cout << "我们一起学喵叫" << endl;
	}

	// 全局函数指针数组
	static PFN_FUNC __vtable_cat[2];
};

// 静态变量初始化
PFN_FUNC CCat::__vtable_cat[2] = { (PFN_FUNC)&CCat::Eat,(PFN_FUNC)&CCat::Bark };


class CMouse :public CAnimal {
public:
	CMouse() {
		// 修改函数指针的指向  指向自己的函数地址表
		this->__vfptr = __vtable_mouse;
	}
	void Eat() {
		cout << "老鼠吃奶酪" << endl;
	}
	void Bark() {
		cout << "老鼠吱吱叫" << endl;
	}
	// 全局函数指针数组
	static PFN_FUNC __vtable_mouse[2];
};

// 静态变量初始化
PFN_FUNC CMouse::__vtable_mouse[2] = { (PFN_FUNC)&CMouse::Eat,(PFN_FUNC)&CMouse::Bark };

int main()
{
	{
		CAnimal* aryAnimals[] = {
			new CCat,
			new CMouse,
			new CMouse
		};

		for(int i = 0; i < sizeof(aryAnimals)/sizeof(aryAnimals[0]);i++){
			
			(aryAnimals[i]->*aryAnimals[i]->__vfptr[0])();
			(aryAnimals[i]->*aryAnimals[i]->__vfptr[1])();
		}

		for (int i = 0; i < sizeof(aryAnimals) / sizeof(aryAnimals[0]); i++) {
			delete aryAnimals[i];
		}
	}
	system("pause");
	return 0;
}