I cannot typedef a pointer to structure that has already been typedef-ed

Question

I am a bit comfused about the row of these declarations. I want to make a linked-list for my program but for some reason it keeps putting error when I try to compile it. Basically this will be my main node model and I also have another struct after it (WITHOUT TYPEDEF) for my list. Which compiles just fine. I don't know what's wrong.

I have already tried to put the typedef over the struct student.

typedef struct
{
    char name[50];
    int id;
    node next;

}student;

typedef student* node;

typedef struct listR* list;

struct listR
{
    node head,tail;
    int size;

};

error: unknown type name 'node' warning: initialization make pointer from integer without a cast

On which line is the "unknown type name `node`" reported? Is it perhaps the line in `student` which is using `node` before it's been defined? — Angew is no longer proud of SO, May 16 '19 at 09:50
Watch the difference between listR and student, On struct listR I don't have any error — Panagiss, May 16 '19 at 09:53

score 2 · Accepted Answer · answered May 16 '19 at 09:55

2

The compiler doesn't know what a node is, because you create the node type after creating the structure.

You can do either :

typedef struct node node;

struct node
{
  char name[50];
  int id;
  node* next;
};

To tell the compiler what a node is,

Or

typedef struct node {
    char name[50];
    int id;
    struct node* next;
} node;

answered May 16 '19 at 09:55

Luc A

98
8

Both your ways in some way solved the problem! but I also did that and worked: typedef struct student * node; typedef struct student{ char name[50]; int id; node next; } – Panagiss May 16 '19 at 10:31
My solution was generic. Glad it helped. Your last solution (in the comment above) works because you prototype your structure, like in the first example. – Luc A May 16 '19 at 10:31

score 0 · Answer 2 · answered Apr 15 '21 at 21:15

0

I would use this:

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

But then I happen to be one of those who does not like typedeffing structs without a good reason. Read more here: https://stackoverflow.com/a/54752982/6699433

answered Apr 15 '21 at 21:15

klutt

30,332
17
55
95

I cannot typedef a pointer to structure that has already been typedef-ed

2 Answers2