Node pointer to current Node during mutile function call - c

Question

I have declared a global pointer ptr and want that it should point to current node during different function call.
This is a sample code where I am creating a new node in fun1 and inserting in link list. In func2 I want to update the other members of newNode in linklist with a different value.
Currently I am traversing the link list to get the current Node or last Node which I dont want since during insertion of new Records already we have to traverse to reach to last Node thus storing the address of last Node.
But by doing the below I am not getting the proper values. Kindly someone suggest where I went wrong.
I am doing like this :
#include<stdio.h>
#include <stdlib.h>
struct Node
{
int data1;
int data2;
struct Node* next;
};
struct Node* head=NULL;
struct Node* ptr =NULL; /* Global pointer */
void insertNode(struct Node ** , struct Node* );
void fun1();
void fun2();
void fun1()
{
struct Node* ptr1 =NULL;
ptr1 = (struct Node*)malloc(sizeof(struct Node*));
ptr1->data1=1; /* intilaizing with some values */
insertNode(&head,ptr1);
}
void fun2()
{
/* Updating the current Node in the linklist with new value . */
ptr->data2=2;
}
void insertNode(struct Node ** head, struct Node* NewRec)
{
if(*head ==NULL )
{
NewRec->next = *head;
*head = NewRec;
ptr=*head;
}
else
{
/* Locate the node before the point of insertion */
struct Node* current=NULL;
current = *head;
while (current->next!=NULL )
{
current = current->next;
}
NewRec->next = current->next;
current->next = NewRec;
ptr=current->next;
}
}
int main ()
{
fun1();
fun2();
while(head!=NULL)
{
printf("%d", head->data1);
printf("%d",head->data2);
head=head->next;
}
return 0;
}

Answer 1

You made a classic mistake.
This is wrong:
ptr1 = (struct Node*)malloc(sizeof(struct Node*));
The allocated space here is sizeof(struct Node*) which is the size of a pointer (usually 4 or 8 bytes depending on the platform). But you need to allocate space for the whole struct Node structure, whose size is sizeof(struct Node).
So you simply need this:
ptr1 = (struct Node*)malloc(sizeof(struct Node));
BTW: in C you don't cast the return value of malloc so you actually should write this:
ptr1 = malloc(sizeof(struct Node));