正向声明和析构函数之间的关系 [英] The relation between Forward declaration and destructors

问题描述

我有以下代码：

#include <iostream>
using namespace std;

class CForward;

void func(CForward* frw) { delete frw; }

class CForward
{
public:
    ~CForward() { cout << "Forward" << endl; }
};

int main()
{
    func(new CForward);
    cin.get();
}

我运行程序，并且什么都不打印。

I ran the program, and it printed nothing.

为什么？

在main中，我创建了 new CFoward code> func 我删除它并将其称为析构函数。

in main, I created new CFoward, and in func I deleted it and called it destructor.

似乎析构函数没有被调用。为什么？

It seems that the destructor have not been called. Why? Is that related anyhow to the forward decleration?

推荐答案

事实上，你的前向声明引入了一个不完整的类型，并且不能在删除表达式中使用：

Indeed, your forward declaration introduces an incomplete type that is later defined with a non-trivial destructor, and that can't be used in a delete expression:

从n3337第5.3.5 / 5节：

From n3337, paragraph 5.3.5/5:

5如果被删除的对象在删除点处具有不完整的类类型，并且完整类具有
非平凡析构函数或释放函数，则行为是未定义。

5 If the object being deleted has incomplete class type at the point of deletion and the complete class has a non-trivial destructor or a deallocation function, the behavior is undefined.

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