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如果我有运算符 T *()，我是否需要重载删除？

发布于 2024-10-28 07:40:38 字数 166 浏览 1 评论 0原文

如果我有一个包含指针的模板类 A，并且 A 有一个将返回该指针的隐式转换运算符，我是否需要或应该定义一个如果我打算将 delete 应用于此类的对象，请使用 A 的 delete 运算符？

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佞臣 2024-11-04 07:40:38

如果定义operator new，则只需定义operator delete - 在这种情况下，您几乎必须这样做。

这并不意味着某些东西不需要删除您的 A* —— 但您不需要为此定义任何运算符，它会默认工作。

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等风来 2024-11-04 07:40:38

我相信您已经得到了类似以下内容：

template <typename T>
struct A {
  T * t;
  operator T* () { return t; } 
};

您打算“将删除应用于此类的对象”，因此我假设您的意思是：

void foo ()
{
  A<int> * p = new A<int>;
  delete p;     // Applying 'delete'
}

如果是这种情况，那么对delete的调用正确地销毁了对象并释放了通过在前一行使用“new”分配的内存，并且您的问题的答案是“否”。

因为您已经声明了一个指针转换运算符，所以可以对 A 类型的对象使用 delete（与 A相反） ;*）。 delete 的使用将应用于调用转换运算符的结果：

void foo ()
{
  A<int> a;
  a.t = new int;
  delete a;       // Same as: delete a.operator T*()
}

delete 工作原理的基本知识：

表达式 delete p 执行以下两个操作：不同的事情。首先，它调用p指向的对象的析构函数，然后释放内存。如果您为类定义了operator delete 成员，那么delete p 将使用该函数来释放内存。

一般来说，只有当您想要控制如何分配或释放该类的动态对象的内存时，才定义这些运算符。

I believe that you've got something like the following:

template <typename T>
struct A {
  T * t;
  operator T* () { return t; } 
};

An you intend to "apply delete to objects of this class", so by that I'm assuming you mean:

void foo ()
{
  A<int> * p = new A<int>;
  delete p;     // Applying 'delete'
}

If this is the case, then the call to delete correctly destroys the object and frees the the memory allocated by the use of 'new' on the previous line and the answer to your question is 'no'.

Because you have declared a conversion operator to a pointer, it is possible to use delete on an object of type A<int> (a opposed to A<int>*). The use of delete will be applied to the result of calling the conversion operator:

void foo ()
{
  A<int> a;
  a.t = new int;
  delete a;       // Same as: delete a.operator T*()
}

Basics of how delete works:

The expression delete p, does two different things. Firstly, it calls the destructor for the object pointed to by p and then it frees the memory. If you define an operator delete member for your class then it will be that function which will be used by delete p to free the memory.

In general, you only define those operators when you want to control how the memory for dynamic objects of that class should be allocated or freed.

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