c++虚函数重写的权限问题

cbase.h:

　#ifndef CBASE_H

#define CBASE_H

#include<iostream>

using std::cout;

using std::endl;

class CBase{

public:

    virtual void show();

};

#endif // CBASE_H

cbase.cpp:
#include"cbase.h"

void CBase::show()

{

    cout<<"CBase"<<endl;

}

cderived.h:
#ifndef CDERIVED_H

#define CDERIVED_H

#include"cbase.h"

class CDerived:public CBase{

private:

    void show() override;

};

#endif // CDERIVED_H

cderived.cpp:
#include"cderived.h"

void CDerived::show()

{

    cout<<"CDerived"<<endl;

}

main.cpp:
#include <iostream>

#include"cderived.h"

using namespace std;

int main()

{

    CBase* pBase=new CDerived;

    pBase->show();

    dynamic_cast<CDerived*>(pBase)->show();

    delete pBase;

    CDerived* pDerived=new CDerived;

    pDerived->show();

    static_cast<CBase*>(pDerived)->show();

    delete pDerived;
    return 0
}
程序运行会报错：dynamic_cast<CDerived*>(pBase)->show();pDerived->show();
说是私有的不可调用
可见编译器只看到了他所看到的，要从编译器的角度看问题。只是把指针是什类型就是什么类型。理解(*（p->vptr）[n])(p,...)