Exception Handled this was Nullptr?

Question

I've been working on this assignment, and been running into this bug I haven't been able to fix for hours. It's saying unhandled exception thrown, read access violation. I heard you're not suppose to deference nullptrs, however I don't believe that's what I'm doing.

void Linkedlist::insertnode(string key, string value) {
    Node* newNode;                      //This points to the following node
    Node* cursor;                       //This will traverse through list
    newNode = new Node;                 //create a new node
    newNode->data = new HashEntry(key, value);              //Initialize the data 
    newNode->next = nullptr;            //Leave the pointer for the node following after empty at inception;
    if (!head) {
        head = newNode;                 //if head is empty, this will make the first user input the head
        return;
    }
    
    else {
        cursor = head;
        while (cursor->next)
            ;       
        //We'll traverse list to add newNode to tail
        cursor->next = newNode;     //for now the order doesn't matter since they're strings so we add new cluster to tail
    }
}

Answer 1

"read access violation" is most likely an uninitialized variable. It happens when you try to access data from memory outside your program memory. This is a protection mechanism of your system to prevent you from overwriting data you shouldn't.

Therefore I'd recommend checking your definition of the class HashEntry as well as the definition of the Pointer head which isn't in your posted code.

What also came in my view is your infinite loop while (cursor->next);

I get what you're trying to do - iterate over the elements until you're at the end of the list. But you have to use an iterator:

Node* iterator = cursor;
while (iterator)
{
  iterator = iterator->next;
}