Doubly Linked List Class constructor segmentation fault

Question

I'm implementing DLL Class. But I can't figure out why calling my constructor always fail.

class Node {
public:
    Node();
    Node(int value, Node *next, Node *prev);
    ~Node();
    int value;
    Node *next;
    Node *prev;
};
Node::Node() {
    this->value = 0;
    this->next = NULL;
    this->prev = NULL;
}
Node::Node(int value, Node *next, Node *prev) {
    this->value = value;
    this->next = next;
    this->prev = prev;
}

class DLLStructure {
public:
    DLLStructure();
    DLLStructure(int *arr, int size);
    
    ~DLLStructure();
    
private:
    Node *first;
    Node *last;
};
DLLStructure::DLLStructure(int arr[], int size) {
    Node *first = NULL;
    Node *last;
    Node *prev;

    for (int i = 0; i < size; i++) {

        //initialize the current node
        last = new Node(arr[i], NULL, NULL);
        if (!first) {
            first = last;
            prev = last;
            continue;
        }

        prev->next = last;
        last->prev = prev;
        prev = last;

    }

    this->first = first;
    this->last = last;
}

int main(){
  int arr[5] = {1,1,1,1,1};
  DLLStructure dll(arr, 5);
  return 0;
}

The weird thing is when I comment out first = last in the if block in DLL Constructor , the program returns zero but when I try to print the value of the list, it's again segmentation fault.

Answer 1

The bug is in my destructor. I mistakenly make Node *cur pointing to null and call cur->prev .