Multiple arrow operators between structs

Question

I am trying to create doubly linked list with a function to add a node at the end of the list. I have two typedef structs: one for Node and one for the doubly linked list.

In insertion_last() I am getting an error when trying to set list->tail->next to new_node. The error is "pointer to incomplete class type is not allowed" and is referring to DoublyLinkedList. I suppose I have done something wrong in making the structs, but cannot quite figure out why it is not working.

#include <stdio.h>
#include <stdlib.h>

typedef struct NodeStruct
{
    int data;
    struct Node *next;
    struct Node *prev;
} Node;

typedef struct DoublyLinkedListStruct
{
    int size;
    struct Node *head;
    struct Node *tail;
} DoublyLinkedList;

Node* newNode(int data, Node* next, Node* prev)
{
    Node* new_node = (Node*)malloc(sizeof(Node));
    new_node->data = data;
    new_node->next = next;;
    new_node->prev = prev;
    return new_node;
};

void insertion_beginning(DoublyLinkedList* list, int new_data)
{
    Node* new_node = newNode(new_data, list->head, NULL);
    list->head = new_node;
    if (!list->tail)
    {
        list->tail = new_node;
    }
    list->size++;
    
}
void insertion_last(DoublyLinkedList* list, int new_data)
{
    Node *new_node = newNode(new_data, NULL, list->tail);
    if(list->tail)
    {
        list->tail->next = new_node;
    }
    else
    {
        list->head = new_node;
    }
    list->tail = new_node;
    list->size++;
}

Answer 1

You define tail and several others fields to have type struct Node *. You don't have any such struct defined.

You want to change those to use struct NodeStruct * instead.