Delete Linked List Function

Question

Here's my function to delete a linked list:

void deleteList( NODE* head )
{
    NODE* temp1; 
    NODE* tempNext;
    temp1 = head;
    tempNext = NULL;

    while( temp1 != NULL )
    {
        tempNext = temp1->next;
        free(temp1);
        temp1 = tempNext;
    }
}

So temp1 first points where the head pointer is pointing. If it isn't NULL, tempNext will be set to point to the next element of the list. Then the first element (temp1) is free'd, and temp1 is reassigned to point to where tempNext is pointing and process repeats.

Is this the right approach to deleting an entire list?

I ask this because when I print the list after using this function, it still prints the list. And IIRC freeing something doesn't delete it but only marks it as available so I'm not sure how to tell if this is correct or not.

Answer 1

Your code looks correct.

You're also correct that freeing a list's elements doesn't immediately change the memory they pointed to. It just returns the memory to the heap manager which may reallocate it in future.

If you want to make sure that client code doesn't continue to use a freed list, you could change deleteList to also NULL their NODE pointer:

void deleteList( NODE** head )
{
    NODE* temp1 = *head;
    /* your code as before */
    *head = NULL;
}