[prog] C++ - linked list and segmentation fault

[Jennifer Davis]

I was wondering if I could get some advice on a program I am trying to
complete for class.  It is a killer as I am new to linked lists.  I write
the program and it compiles.  However, when it runs, it segfaults.  I'm
sure it happens when I am creating the list.  All help would be very much
appreciated.

Jennifer S. Davis
Computer Programming, 1st year
Algonquin College
davi0302 at algonquinc.on.ca


#include<iostream.h> // for cin & cout
#include<stdio.h>    // for I don't know what
#include<stdlib.h>   // for I don't know what
#include<conio.h>    // for getch()
#include<fstream.h>  // for file i/o

struct INVENTORY_ITEM{
    INVENTORY_ITEM *nextItem;
    char itemCode[7];
    int quantity;
    float price;
    }; // end struct INVENTORY_ITEM

void createFile  (INVENTORY_ITEM *pStart);
void createOutput(INVENTORY_ITEM *pStart);
void deAllocate  (INVENTORY_ITEM *pStart);

int main(){
    INVENTORY_ITEM* pStart;
    createFile     (pStart);
    createOutput   (pStart);
    deAllocate     (pStart);
    }//end main

void createFile(INVENTORY_ITEM *pStart){

    ifstream in;
    in.open("infile.txt");

    INVENTORY_ITEM  temp;
    INVENTORY_ITEM* p;
    INVENTORY_ITEM* current;

    in >> temp.itemCode;
    while (!in.eof()){
        in >> temp.quantity;
        in >> temp.price;
        current=new INVENTORY_ITEM;
        *current=temp;
        current->nextItem=NULL;
        p=pStart;
        while ((p!=NULL)&&(strcmp(current->itemCode,p->itemCode)<0))
                p=p->nextItem;
        p->nextItem=current;
        in >> temp.itemCode;
        } // end while
    in.close();
    }// end createFile

void createOutput(INVENTORY_ITEM *pStart){
    ofstream out;
    out.open("outfile.txt");
    INVENTORY_ITEM* current;
    current=pStart;
    while(current!=NULL){
        out     << current->itemCode << "\t"
                << current->quantity << "\t"
                << current->price    << "\n";
        current=current->nextItem;
        } // end while
    out.close();
    } // end createOutput

void deAllocate(INVENTORY_ITEM *pStart){
    INVENTORY_ITEM* current;
    INVENTORY_ITEM* temp;
    current=pStart;
    while (current !=NULL){
        temp->nextItem=current;
        delete current;
        current=temp;
        } // end while
    } // end deAllocate