C ++ LinkedList错误：访问冲突错误

Question

I am trying to implement Linked List in C++. Following is my code and I am getting this exception

First-chance exception at 0x012F4C61 in LinkedList.exe: 0xC0000005: Access violation reading location 0xCDFCA94C.

header file

#pragma once
#include "LinkNode.h"

class LinkedList
{
 private:
    LinkNode *head;
    LinkNode *tail;
    public:
    LinkNode add(int data);
    void print();
    LinkNode getHead();
    LinkedList(void);
    ~LinkedList(void);

    private:
    void modify();
 };

Cpp file

#include "stdafx.h"
#include "LinkedList.h"
#include <iostream>

using namespace std;

LinkedList::LinkedList(void)
{
 this->head = NULL;
 this->tail = NULL;
}

LinkedList::~LinkedList(void)
{ 
}


LinkNode LinkedList :: add(int data)
{
  if(this->head == NULL)
  {
    this->head = new LinkNode(data);
    this->tail = head;
    return *head;
}
else
{
    LinkNode node(data);
    tail->next = &node; 
    tail = tail->next;
 }
}

Main function

int _tmain(int argc, _TCHAR* argv[])
{
   LinkedList linklist;
   linklist.add(1);
   linklist.add(2);
   linklist.add(3);
   linklist.add(4);
   linklist.add(5); 
   linklist.print();
   system("pause");
}

Answer 1

LinkNode node(data);
tail->next = &node; 
tail = tail->next;

node resides on stack and life time of it ends as control leaves the LinkedList::add member function. Dynamically allocate the tail->next node instead.

Also destructor needs to properly deallocate the resources dynamically acquired. Currently, the program has memory leaks.