Segmentation Fault because of Pointers

I have been having a ton of trouble because I have forgotten all of the rules of pointers. I learned about pointers 3 years ago and haven't used them since. I am receiving a segmentation fault in the line contents -> setPrevious(&node) in the function add in the LinkedList.cpp file. I believe it has something to do either with calling the setPrevious function or passing node as a pointer. Any help would be great. Thanks!

LinkedList.h

#ifndef LINEARNODE_H
#define LINEARNODE_H

#include<iostream>

using namespace std;

class LinearNode
{
    public:
        //Constructor for the LinearNode class that takes no arguments 
        LinearNode();
        //Constructor for the LinearNode class that takes the element as an argument
        LinearNode(int el);
        //returns the next node in the set.
        LinearNode* getNext();
        //returns the previous node in the set
        LinearNode* getPrevious();
        //sets the next element in the set
        void setNext(LinearNode* node);
        //sets the previous element in the set
        void setPrevious(LinearNode* node);
        //sets the element of the node
        void setElement(int el);
        //gets the element of the node
        int getElement();

    private: 
        LinearNode* next;
        LinearNode* previous;
        int element;        
};//ends the LinearNode class

#endif

LinkedList.cpp

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

using namespace std;

//linkedlist constructor for an empty linked list
LinkedList::LinkedList()
{
    count = 0;
    contents = NULL;
}//ends the constructor

//adds an element to the front of the linked list
void LinkedList::add(int element)
{

    int found = 0, current = 0;

    for (int index = 0; index < count; index++)
    {
        if (contents -> getElement() == element)
            found = 1;
        else    
        {

            contents = contents -> getNext();
        }//ends the else statement
    }//ends the while loop

    if ((found == 0) && (count == 0))
    {
        LinearNode node;
        node.setElement(element);
        contents = &node;
        count++;
print();
    }//ends the if statement
    else
    {

        LinearNode node;
        node.setElement(element);
        node.setNext(contents);
        contents -> setP开发者_如何学编程revious(&node);
        contents = &node;
        count++;
//print();
cout << endl;
    }//ends the found == 0 if statment
}//ends the add function

//this function removes one element from the linked list.
int LinkedList::remove(int element)
{
    int found = 0, result = 0; 
    LinearNode* previous;
    LinearNode* current;

    if (count == 0)
        cout << "The list is empty" << endl;
    else 
    {
        if (contents -> getElement() == element)
        {
            result = contents -> getElement();
            contents = contents -> getNext();
        }//ends the contents.getElement() == element
        else 
        {
            previous = contents;
            current = contents -> getNext();
            for (int index = 0; ( (index < count) && (found == 0) ); index++)
                if (current -> getElement() == element)
                    found = 1;
                else
                {
                    previous = current;
                    current = current -> getNext();
                }//ends the else statement 

            if (found == 0)
                cout << "The element is not in the list" << endl;
            else
            {
                result = current -> getElement();
                previous -> setNext(current -> getNext());
            }//ends else statement  

        }//ends the else stamtement

        count--;
    }//ends the else statement of count == 0
    return result;
}//ends the remove function


void LinkedList::print()
{
    LinearNode* current;
    current = contents; 

    for (int index = 0; index < count; index++)
    {
        cout << current -> getElement() << endl;
        current = current -> getNext();
    }//ends the for loop
}//ends Print function

LinearNode.h

 #ifndef LINEARNODE_H
#define LINEARNODE_H

#include<iostream>

using namespace std;

class LinearNode
{
    public:
        //Constructor for the LinearNode class that takes no arguments 
        LinearNode();
        //Constructor for the LinearNode class that takes the element as an argument
        LinearNode(int el);
        //returns the next node in the set.
        LinearNode* getNext();
        //returns the previous node in the set
        LinearNode* getPrevious();
        //sets the next element in the set
        void setNext(LinearNode* node);
        //sets the previous element in the set
        void setPrevious(LinearNode* node);
        //sets the element of the node
        void setElement(int el);
        //gets the element of the node
        int getElement();

    private: 
        LinearNode* next;
        LinearNode* previous;
        int element;        
};//ends the LinearNode class

#endif

LinearNode.cpp

#include<iostream>
#include"LinearNode.h"

using namespace std;

//Constructor for LinearNode, sets next and element to initialized states
LinearNode::LinearNode()
{
    next = NULL;
    element = 0;
}//ends LinearNode default constructor

//Constructor for LinearNode takes an element as argument.
LinearNode::LinearNode(int el)
{
    next = NULL;
    previous = NULL;
    element = el;
}//ends LinearNode constructor

//returns the next element in the structure
LinearNode* LinearNode::getNext()
{
    return next;
}//ends getNext function

//returns previous element in structure
LinearNode* LinearNode::getPrevious()
{
    return previous;
}//ends getPrevious function

//sets the next variable for the node
void LinearNode::setNext(LinearNode* node)
{
    next = node;

}//ends the setNext function

//sets previous for the node
void LinearNode::setPrevious(LinearNode* node)
{
    previous = node;
}//ends the setPrevious function

//returns element of the node
int LinearNode::getElement()
{
    return element;
}//ends the getelement function

//sets the element of the node
void LinearNode::setElement(int el)
{
    element = el;
}//ends the setElement function

---

    LinearNode node;
    node.setElement(element);
    contents = &node;
    count++;

This creates a LinearNode on stack, makes contents point to this node, leaves the scope at the following } - which invalidates node - and contents thereafter points to invalid data.

You need to rethink your whole class - a linked list requires heap storage, so you have to use new and delete

There's several other errors in your source, but you should fix this basic misconception first, and then come back with an updated question if needed.

Some of the other errors:

• Lack of copy constructors, assignment operators and destructors
• No check for null before dereferencing pointers
• Not setting all pointers to null in constructors

---

The problem is that you are not allocating Node in the heap, only on the stack.

In the add function

 LinearNode node;
 node.setElement(element);
 contents = &node;
 count++;

Should be:

 LinearNode* node = new LinearNode;
 node->setElement(element);
 contents = node;
 count++;

---

That's a lot of code to go through looking for every little problem, but one bad thing that jumps out is in LinkedList::add(). There you're declaring "node" on the stack, and then setting a pointer to point to it. When add() returns, that pointed-to object becomes trash -- the destructor is called. That's the kind of thing that leads quickly to segfaults.