doubly linked list not getting displayed

[simons]

Hi,
The following doubly linked list program is working till the first call to insertInDlinkedList. After that the list is not being displayed.
Any help would be great.

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

void create(struct node **, int );
void display(struct node *);
void insertInDlinkedList(struct node **, int, int);
struct node {
	int data;
	struct node * prev;
	struct node * next;
};

int main()
{
	struct node *head;
	head = NULL; /*empty doubly linked list*/
	create(&head, 11); /* creating the first node with data 11 */
	insertInDlinkedList(&head, 20, 1); /*working till this point */
	insertInDlinkedList(&head, 23, 1);
	insertInDlinkedList(&head, 26, 2);
	display(head);
}

void create(struct node **h, int num){

	if (*h == NULL){
		/*create a new node*/
		*h = (struct node *)malloc(sizeof(struct node *));
		(*h)->data = num;
		(*h)->prev = NULL;
		(*h)->next = NULL;

	}

}

void insertInDlinkedList(struct node **h, int data, int pos){
	struct node *newnode , *temp = nullptr;
	int k = 1;
	newnode = (struct node *)malloc(sizeof(struct node));
	if (!newnode){
		printf("Memory Error \n");
		return;
	}
	newnode->data = data;
	if (pos == 1){
		newnode->next = *h;
		newnode->prev= NULL;
		(*h)->prev = newnode;
		*h = newnode;
		//return;
	}
	
	else {
		temp = *h;
		while (temp->next != NULL && (k < pos)){
			k++;
			temp = temp->next;
		}
		if (temp->next == NULL){
			newnode->next = temp->next;
			newnode->prev = temp;
			temp->next = newnode;

		}
		else {
			newnode->next = temp->next;
			newnode->prev = temp;
			temp->next->prev = newnode;
			temp->next = newnode;
		}
		return;
	}

}

void display(struct node *h){
	struct node * current;
	current = h;
	printf("inside display\n");
	while (current != NULL){
		printf("%d ->", current->data);
		current = current->next;
	}
	printf("NULL");
	printf("\n");
}

[cire]

Tell us what line 28 is supposed to do. The comment on line 27 suggests it is supposed to create a new node, but does it?

[simons]

thanks for pointing out the mistake. I corrected it and it started working.
I changed line 28 to the following :

*h = (struct node *)malloc(sizeof(struct node ));

But my question is , why did it even allow to create the second node having data 20. ?
If I comment out all the insertInDlinkedList calls except the first one , the linked list gets
formed as below :

20->11->NULL

[cire]

But my question is , why did it even allow to create the second node having data 20. ?

It "appeared" to work. That's one thing that may happen with undefined behavior.

[simons]

Ok.

But as the insert operation is working now at every position, I hope the implmentation of the doubly linked list code is correct now.