C programming, causing unhandled win32 exception, possibly in strlen function. - c

Question

My c program, written in the visual-studio 2010, is throwing an unhandled win32 exception.
I think it's in a strlen function, based on the debugger output, but I'm not sure.
The file I'm reading in is multiple lines with ; used as a delimiter, and the error seems to happen as I reach the end of the first linked list so presumably in readFile or insertNode.
The first line of the file is something like:
blah division;first department;second department
Any help would be appreciated. I searched through the first few pages of a StackOverflow search on unhandled win32 exceptions, and they seem to relate to access violations or memory overflow problems
#define _CRT_SECURE_NO_WARNINGS 1
#define FLUSH while (getchar () != '\n')
#define DEFAULT "dept.txt"
#define LENGTH 50
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
//Structures
typedef struct DEPT {
char * DeptName;
struct DEPT * link;
} DEPT;
typedef struct {
char divisionName[LENGTH];
DEPT * first;
} DIVISION;
//Function Declarations
int ReadFile (DIVISION DivArr [], int * lastDiv);
FILE * getFileName (void);
DEPT * insertNODE (DEPT * pList, char * string);
int main (void) {
//Local Declarations
//Create the array of the DIVISION Structure
DIVISION DivArr[20];
int i;
int lastDiv;
//Statements
//Read in File
if (ReadFile (DivArr, &lastDiv)) {
return 1;
}
for (i = 0; i < lastDiv; i++) {
printf ("%s\n",DivArr[i].divisionName);
}
return 0;
}
/*==================================ReadFile==================================
Calls getFileName to get the file name to open, then reads the file's data into
DivArr, parsing them appropriately, returning 1 if the file can't be opened */
int ReadFile (DIVISION DivArr [], int * lastDiv){
//Local Declarations
FILE * datafile;
char tempstring[300], *Ptoken;
int linenum = 0;
//Statements
datafile = getFileName();
//return from function with 1 if file can't be opened
//go through file line by line
while (fgets(tempstring, sizeof(tempstring), datafile)) {
//tokenize string
Ptoken = strtok (tempstring , ";");
//first part of string is assigned to divisionName
strncpy(DivArr[linenum].divisionName, Ptoken, LENGTH - 1);
DivArr[linenum].first = NULL;
//subsequent parts are assigned to linked list
while(Ptoken) {
Ptoken = strtok (NULL, ";\n");
DivArr[linenum].first = insertNODE (DivArr[linenum].first, Ptoken);
}
linenum++;
}
*lastDiv = linenum;
fclose(datafile);
return 0;
} //ReadFile
/* =================================getFileName===============================
Gets input from the keyboard and if enter is pressed, returns default, otherwise returns specified filename */
FILE * getFileName (void){
//local declarations
int open = 1;
char read[LENGTH];
FILE * datafile = NULL;
//Statements
//open file
do{
printf ("Enter a filename to open, or press enter for default:");
fgets (read, LENGTH - 1, stdin);
if ('\n' == read[0]) {
strncpy (read , DEFAULT, LENGTH - 1);
}
else
read[strlen(read) - 1] = '\0';
if((datafile = fopen(read, "r")) == NULL)
printf ("Error opening %s\n", read);
else
open = 0;
} while (open == 1);
return datafile;
} //getFileName
/* =================================insertNODE================================
Gets the address of the beginning of the list for the structure, then
allocates memory for nodes, then allocates memory for string, then passes
string to allocated memory, then links node
*/
DEPT * insertNODE (DEPT * pList, char * string)
{
//Local Declarations
DEPT * pNew;
DEPT * pWalker = pList;
DEPT * pPre;
//Statements
if ( !(pNew = (DEPT*)malloc(sizeof(DEPT))))
printf ("\nMemory overflow in insert\n"),
exit (100);
printf ("size of string + null = %d\n",strlen(string) + 1);
if(!(pNew->DeptName =(char*)calloc(strlen(string) + 1, sizeof(char))))
{
printf ("\nMemory overflow in string creation\n");
exit (100);
}
strncpy(pNew->DeptName, string, strlen(string));
printf("%s is %d long", pNew->DeptName, strlen(pNew->DeptName));
if (pWalker == NULL) //first node in list
{
pNew->link = pList;
pList = pNew;
}
else {
while (pWalker){
pPre = pWalker;
pWalker = pWalker->link;
}
pPre->link = pNew;
pNew->link = NULL;
}
return pList;
}

Answer 1

This loop might be the reason of your error:
//subsequent parts are assigned to linked list
while(Ptoken) {
Ptoken = strtok (NULL, ";\n");
DivArr[linenum].first = insertNODE (DivArr[linenum].first, Ptoken);
}
What happens when strtok returns NULL? Add a check for that between strtok and insertNODE.