关于c ++：存储在ptr_vector中的派生类没有被破坏


Derived class stored in ptr_vector not being destructed

试图找到使用ptr_向量存储、访问和释放对象的最佳方法，尤其是当存储的对象从其他对象继承时(ptr_向量不应存在任何对象切片问题)。但是当运行下面的程序时，令人惊讶的是派生类没有被破坏。有人知道为什么吗？

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
#include <boost/ptr_container/ptr_vector.hpp>
#include <iostream>
#include <boost/ptr_container/ptr_map.hpp>
#include <boost/foreach.hpp>
using namespace std;

class A
{
 public:
 int id;
 A() {cout<<"Constructed A()"<<endl;}
 A(int i):id(i) {cout<<"Constructed A"<<i<<endl;}
 ~A() {cout<<"* Destructed A"<<id<<endl;}
};
class B:public A
{
 public:
 int i;
 B() {cout<<"Constructed B"<<endl;}
 B(int ii):i(ii) {id=ii;cout<<"Constructed B"<<i<<endl;}
 ~B() {cout<<"* Destructed B"<<i<<endl;}
};

class zoo
{
 boost::ptr_vector<A> the_animals;
public:
 void addAnimal(A* a) {the_animals.push_back( a );}
 void removeAnimal(int id) {the_animals.release(the_animals.begin()+id); }
 void removeOwnership(int id) {the_animals.release(the_animals.begin()+id).release();}
};

int main()
{
 zoo z;
 z.addAnimal( new B(0) );
 //delete abc;z.addAnimal(abc);//doing this will cause heap corruption
 B* lion=new B(1);
 z.addAnimal(lion);
 z.removeOwnership(1);
        delete lion;
 z.removeAnimal(0);
}//main

程序输出为：

1
2
3
4
5
6
7
Constructed A()
Constructed B0
Constructed A()
Constructed B1
* Destructed B1
* Destructed A1
* Destructed A0

为什么b0没有被摧毁？物体被切割了吗？

基类的析构函数不是虚拟的：

1
 ~A() {cout<<"* Destructed A"<<id<<endl;}

应该是：

1
 virtual ~A() {cout<<"* Destructed A"<<id<<endl;}

为什么？看看什么时候你的析构函数应该是虚拟的？

相关讨论