多繼承指針轉化的問題

多繼承指針轉化的問題

多繼承的指針轉化跟數據在內存的布局有極大的關系。目前，用msvc11和gcc4.8.3去測試指針轉化之後的結果。發現只要不涉及編譯增加虛表指針的情況下，派生類的地址多數是和繼承列表的首個父類地址相同。當然會有其他問題影響到布局的指針轉化。此次要提的內容是，別使用c_style指針轉化。正確的指針轉化來自於：dynamic_cast/static_cast。

編譯器內部生成的指針對象有某個反射機制，能從父類指針正確的映射出派生類地址。無論是普通繼承還是virtual繼承。具體的內存布局我還要看完書才行，待續。

編譯器的實現真是太有學問啦，同時也影響著我們使用這門語言。為了未來幾十年能在游戲引擎有所作為，必須吃透C++/C、數學和計算機圖形學應用方向等。

#include 
#include 
#include 
#include 




class A
{
public:
	A()
	{
		i = 10;
	};
	~A(){};
	virtual void display()
	{

	}
	int i;
};

class B
{
public:
	virtual void display()
	{

	}
	int j;
};

class C :public A,public B
{
public:
	int i;
	int k;
private:
	
	
};

class D:virtual public A
{
public:
	int di;
	virtual void display() override
	{

	}
private:

};

class  E :virtual public A
{
public:
	int ei;
	virtual void display() override
	{

	}

private:

};

class F : public D,public E
{
public:
	int fi;

	virtual void display() override
	{

	}

private:

};








int main(int argv, char **argc)
{


	C * pC = new C();
	B * pB = dynamic_cast(pC);
	A * pA = dynamic_cast(pC);
	B * pB_s = static_cast(pC);
	A * pA_s = static_cast(pC);
	C * pCB_D = dynamic_cast(pB);
	C * pCA_D = dynamic_cast(pA);
	C * pCB_S = static_cast(pB);
	C * pCA_S = static_cast(pA);

	pC->i = 100;
	printf("%d\n",pA->i);
	

	printf("pC = %d,pB_d = %d,pA_d = %d,pB_s = %d,pA_s = %d\n", pC, pB, pA, pB_s, pA_s);

	printf("pCB_D = %d,pCA_D = %d,pCB_S = %d,pCA_S = %d\n", pCB_D, pCA_D, pCB_S, pCA_S);

	F * pF = new F();

	D * pD = dynamic_cast(pF);
	E * pE = dynamic_cast(pF);
	D * pD_s = static_cast(pF);
	E * pE_s = static_cast(pF);

	F * pFD_D = dynamic_cast(pD);
	F * pFE_D = dynamic_cast(pE);
	F * pFD_S = static_cast(pD);
	F * pFE_S = static_cast(pE);

	printf("pF = %d,pD_d = %d,pE_d = %d,pD_s = %d,pE_s = %d\n", pF, pD, pE, pD_s, pE_s);
	
	printf("pFD_D = %d, pFE_D = %d,pFD_S = %d, pFE_S = %d\n", pFD_D, pFE_D, pFD_S, pFE_S);
	
	return 0;
}