如何定义包含指向自身的指针的 typedef 结构? [英] How to define a typedef struct containing pointers to itself?

问题描述

我正在用 C 编写一个 LinkedList，下面的代码代表我的 Node 定义.

I am writing a LinkedList in C, the below code represent my Node definition.

typedef struct {
    int value;
    struct Node* next;
    struct Node* prev;
} Node;

我理解(或认为我知道)struct Node 与 typedef struct Node 不同.允许我的代码按预期编译和运行，但是，在分配 next 和 prev 时我收到很多警告(警告:从不兼容的指针类型分配).我猜这与我如何在 Node 结构中定义它们有关.我上传了完整的源代码这里

I understand (or think that I do) that struct Node not the same as typedef struct Node. Granted my code compiles and runs as it's supposed to, however, I get a lot of warnings when assigning next and prev (warning: assignment from incompatible pointer type). I am guessing that this has to do with how I'm defining them in the Node structure. I uploaded the full source here

那么，如果这确实是问题所在，我应该如何在 typedef struct Node 中定义 next 和 prev ?

So, if that is indeed the problem, how should I define next and prev inside the typedef struct Node?

我担心这可能是转帖，但找不到我要找的内容.谢谢.

I was worried this may be a repost, but couldn't quite find what I was looking for. Thanks.

推荐答案

你需要按照这个顺序进行:

You need to do it in this order:

typedef struct Node Node;

struct Node
{
  int value;
  Node *next;
  Node *prev;
};

这并不完全符合您的要求，但它解决了问题，并且通常是这样做的.我认为没有更好的方法.

That doesn't do exactly what you asked, but it solves the problem and is how this generally is done. I don't think there's a better way.

这种前向声明还有第二个用途，即数据隐藏.如果列表是在库中实现的，则您可以在公共标头中只包含 typedef 以及如下函数:

This kind of forward declaration has a second usage, in data hiding. If the list was implemented in a library, you could have just the typedef in the public header, along with functions like:

Node * list_new(void);
Node * list_append(Node *head, Node *new_tail);
size_t list_length(const Node *head);

通过这种方式，库的用户无法轻松访问库的内部，即 Node 结构的字段.

This way, users of the library don't have easy access to the internals of your library, i.e. the fields of the Node structure.

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