warning C4541: “dynamic_cast”用在了带 /GR- 的多态类型“ANIMAL”上；可能导致不可预知的行为

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配置属性-〉C/C++

 1 class Base
 2 {
 3 public:
 4     Base(){};
 5     virtual void Show(){cout<<"This is Base calss";}
 6 };
 7 class Derived:public Base
 8 {
 9 public:
10     Derived(){};
11     void Show(){cout<<"This is Derived class";}
12 };
13 int main()
14 {
15     Base *base ;
16     Derived *der = new Derived;
17     //base = dynamic_cast<Base*>(der); //正确，但不必要。
18     base = der; //先上转换总是安全的
19     base->Show();
20     system("pause");
21 }

#include "stdafx.h"
#include<iostream>
using namespace std;class Base
{
public:Base(){};virtual void Show(){cout<<"This is Base calss";}
};
class Derived:public Base
{
public:Derived(){};void Show(){cout<<"This is Derived class";}
};
int main()
{    //这是第一种情况Base* base = new Derived;if(Derived *der= dynamic_cast<Derived*>(base)){cout<<"第一种情况转换成功"<<endl;der->Show();cout<<endl;}//这是第二种情况Base * base1 = new Base;if(Derived *der1 = dynamic_cast<Derived*>(base1)){cout<<"第二种情况转换成功"<<endl;der1->Show();}else {cout<<"第二种情况转换失败"<<endl;}delete(base);delete(base1);system("pause");
}

    Derived c;Derived & der2= c;Base & base2= dynamic_cast<Base&>(der2);//向上转换，安全base2.Show();

int main()
{    //第一种情况，转换成功
    Derived b ;Base &base1= b;Derived &der1 = dynamic_cast<Derived&>(base1);cout<<"第一种情况：";der1.Show();cout<<endl;//第二种情况
    Base a ;Base &base = a ;cout<<"第二种情况：";try{Derived & der = dynamic_cast<Derived&>(base);}catch(bad_cast){cout<<"转化失败,抛出bad_cast异常"<<endl;}system("pause");
}