freeing a double pointer to a linked list in C

Question

I am kind of new to c and tried to use a single linked list for stack implementation. To implement push() and pop() functions I passed a double pointer. In main I initialize Node *node_head to NULL

I use malloc() and free() to successfully handle memory leaks but it seems that I have memory leaks somewhere that I can't figure out. Should I take a different approach when freeing a double pointer? Thank you and here are the two functions:

void stack_push(Node **node_head, int d)
{
    Node *node_new = malloc(sizeof(Node));

    node_new -> data = d;
    node_new -> next = *node_head;
    *node_head = node_new;
}

int stack_pop(Node **node_head)
{
    Node *node_togo = *node_head;
    int d = 0;

    if(node_head)
    {
        d = node_togo -> data;
        *node_head = node_togo -> next;
        free(node_togo);
    }
    return d;
}

Answer 1

The only error in your code is in function stack_pop.

if(node_head)

Of course you may check whether node_head is equal to NULL though in my opinion it is a superflouos check. But you have to check that *node_head is not equal to NULL.

The function could look like

int stack_pop(Node **node_head)
{
    int d = 0;

    if( *node_head )
    {
        Node *node_togo = *node_head;

        d = node_togo -> data;

        *node_head = node_togo -> next;

        free( node_togo );

    }

    return d;
}