公共运营商新建，私有运营商删除:获取C2248“无法访问私有成员"当使用新 [英] Public operator new, private operator delete: getting C2248 "can not access private member" when using new

问题描述

一个类具有重载运算符 new 和 delete.new 是公开的，delete 是私有的.

A class has overloaded operators new and delete. new is public, delete is private.

在构造此类的实例时，出现以下错误:

When constructing an instance of this class, I get the following error:

pFoo = new Foo(bar)

example.cpp(1): 错误 C2248: 'Foo:operator delete': 无法访问类 'Foo' 中声明的私有成员

但是这里没有调用delete，那么编译器的扭曲思想是怎么回事?:)

But there's no call to delete here, so what is going on in the twisted mind of the compiler? :)

1. 错误的原因是什么?
2. 是否可以在不求助于成员 CreateInstance 函数的情况下解决问题?

1. What is the reason for the error?
2. Is it possible to resolve the problem without resorting to a member CreateInstance function?

推荐答案

当你执行 new Foo() 时，会发生两件事:首先调用 operator new 来分配内存，然后调用 Foo 的构造函数.如果该构造函数抛出异常，因为您无法访问已分配的内存，C++ 运行时将通过将其传递给适当的 operator delete 来处理它.这就是为什么你总是必须为你编写的每个 operator new 实现一个匹配的 operator delete 并且这就是它需要可访问的原因.

When you do new Foo() then two things happen: First operator new is invoked to allocate memory, then a constructor for Foo is called. If that constructor throws, since you cannot access the memory already allocated, the C++ runtime will take care of it by passing it to the appropriate operator delete. That's why you always must implement a matching operator delete for every operator new you write and that's why it needs to be accessible.

作为一种出路，您可以将它们都设为私有并从公共成员函数(如 create())调用 operator new.

As a way out you could make both of them private and invoke operator new from a public member function (like create()).

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