Segmentation fault (core dumped) when I delete pointer

Question

I am trying to remove duplicates from a linked list, and encountered a problem, which is probably obvious and straightforward but I haven\'t used C++ in many years

Answer 1

In this case having the code of the constructor and also of destructor is very important.

By default you should use "new" in constructor and "delete" in destructor. To be more specific, is very important to allocate all the resources you need in constructor and deallocate in destructor, this way you ensure you don't have any memory leaks.

free(temp);//You don't need this, also you don't need delete.

Please post your constructor and your destructor code.

L.E:

I think you should do something like this:

template
class LinkedList
{
  private:
    struct Node {
        T m_data;
        Node *m_next;
        Node *m_prev;
    };
    Node* m_first;
    Node* m_last;
    int m_count;
  public:
    LinkedList();
    ~LinkedList();
    T GetFirst();
    T GetLast();
    void AddNode(T node);
    void RemoveAt(int index);
    T GetAt(int index);
    int Count();
};

//constructor
template 
LinkedList::LinkedList(){
    m_count = -1;//-1 == "The list is empty!
}

template 
void LinkedList::AddNode(T data){
    Node* temp = new Node; //new is called only here -> delete is called in destructor or in RemoveAt
    temp->m_data = data;
    if (m_count > -1){//If the list contains one or more items
        temp->m_next = m_first;
        temp->m_prev = m_last;
        m_last->m_next = temp;
        m_last = temp;
        m_count++;
    }
    else if (m_count == -1)
    {//If no items are present in the list
        m_first = temp;
        m_first->m_next = temp;
        m_first->m_prev = temp;
        m_last = temp;
        m_last->m_next = temp;
        m_last->m_prev = temp;
        m_count = 0;
    }
}

template 
void LinkedList::RemoveAt(int index){
    if (index <= m_count)//verify this request is valid
    {
        Node* temp = m_last;
        for (int i = 0; i <= index; ++i){
            temp = temp->m_next;
        }
        temp->m_prev->m_next = temp->m_next;
        temp->m_next->m_prev = temp->m_prev;
        delete temp;
        m_count--;
    }
}

template 
T LinkedList::GetAt(int index)
{
    Node* temp = m_first;
    if (index <= m_count && index > -1){
        int i = 0;
        while(i < index){
            temp = temp->m_next;
            i++;
        }
    }
    return temp->m_data;
}

template 
T LinkedList::GetFirst() {
    return m_first->data;
}

template 
T LinkedList::GetLast(){
    return m_last->data;
}

template 
int LinkedList::Count(){
    return m_count;
}

template 
LinkedList::~LinkedList(){
   while(m_count > -1){
        Node* temp = m_first;
        m_first = temp->m_next;
        delete temp;//delete in destructor
        m_count--;
    }
}