虚析构函数（C++）

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4.3 虚析构函数

C++允许将析构函数定义为虚函数，为什么？

#include <iostream>
using namespace std;class Base{
public:Base(){cout << "Base 通过 new 申请100个字节内存空间" << endl;}~Base(){cout << "~Base 通过 delete 释放100个字节内存空间" << endl;}
};class Derived:public Base{
public:Derived(){cout << "Derived 通过 new 申请200个字节内存空间" << endl;}~Derived(){cout << "~Derived 通过 delete 释放200个字节内存空间" << endl;}
};int main(void) {Base *pb = new Derived;delete pb; //只调用了基类的析构函数 造成内存泄漏return 0;
}
//输出结果  
myubuntu@ubuntu:~/lv19/cplusplus/dy05$ ./a.out 
Base 通过 new 申请100个字节内存空间
Derived 通过 new 申请200个字节内存空间
~Base 通过 delete 释放100个字节内存空间

如何解决该问题？将基类析构函数定义为虚函数

#include <iostream>
using namespace std;class Base{
public:Base(){cout << "Base 通过 new 申请100个字节内存空间" << endl;}virtual ~Base(){  //定义为虚函数cout << "~Base 通过 delete 释放100个字节内存空间" << endl;}
};class Derived:public Base{
public:Derived(){cout << "Derived 通过 new 申请200个字节内存空间" << endl;}~Derived(){cout << "~Derived 通过 delete 释放200个字节内存空间" << endl;}
};int main(void) {Base *pb = new Derived;delete pb;return 0;
}
//输出结果  
myubuntu@ubuntu:~/lv19/cplusplus/dy05$ ./a.out 
Base 通过 new 申请100个字节内存空间
Derived 通过 new 申请200个字节内存空间
~Derived 通过 delete 释放200个字节内存空间
~Base 通过 delete 释放100个字节内存空间
myubuntu@ubuntu:~/lv19/cplusplus/dy05$ 

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