为什么C ++默认析构函数不销毁我的对象？ [英] Why doesn't the C++ default destructor destroy my objects?

问题描述

C ++规范说，默认析构函数删除所有非静态成员。

The C++ specification says the default destructor deletes all non-static members. Nevertheless, I can't manage to achieve that.

我有这个：

class N {
public:
    ~N() {
        std::cout << "Destroying object of type N";
    }
};

class M {
public:
    M() {
        n = new N;
    }
//  ~M() { //this should happen by default
//      delete n;
//  }
private:
    N* n;
};

然后这应该打印给定的消息，但它不：

Then this should print the given message, but it doesn't:

M* m = new M();
delete m; //this should invoke the default destructor

推荐答案

认为对象 n 指向应该在默认情况下删除？默认析构函数销毁指针，而不是指向它。

What makes you think the object n points to should be deleted by default? The default destructor destroys the pointer, not what it's pointing to.

编辑：我会看看我是否可以更清楚一点。

I'll see if I can make this a little more clear.

如果你有一个局部指针，并且它超出范围，你会指望它指向的对象被销毁吗？

If you had a local pointer, and it went out of scope, would you expect the object it points to to be destroyed?

{
    Thing* t = new Thing;

    // do some stuff here

    // no "delete t;"
}

t 指针被清理，但 Thing 它指向是不是。这是一个泄漏。基本上同样的事情发生在你的班上。

The t pointer is cleaned up, but the Thing it points to is not. This is a leak. Essentially the same thing is happening in your class.

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