Question

I have following method in the c code.

    void add(int number)
    {
    Node node1; // a new node should be created
    createNodeRelationshipBetween(&node1, current);
    setData(&node1, number);
    setCurrentNode(&node1);
    incrementSize();
    printf("Inserted Node [data:- %d, Node address:- %p\n", node1.data, &node1);
   }

where Node is defined as

typedef struct node
 {
    struct node *prior;
    struct node *next;
    int data;
 } Node;

I am calling add() in a loop. My understanding is that every time i call add(i), a new Node should be created. Instead when i print the address of node1, it is same every time. Can someone please explain where the error is and how do i create a new node?

Answer 1

Your function does create a new Node, but only as a local variable. When your add() function returns, it vanishes. If you’re calling add() in a loop, the address of the Node object on the stack is always going to be the same.

To make your new Node persistent, you will need to allocate some persistent memory for it – check out malloc(3) and free(3). A quick example:

Node *node1 = malloc(sizeof(Node));

You will need to keep track of the node1 pointer so as not to introduce a memory leak. You can use free(3) later to destroy the allocation.