Program is crashing since I added a new function. Where have I gone wrong?? :S

I've made a program that takes information from a list of mp3s in a text file and stores them into a structure, which is then looked up using an array of pointers.
Each mp3 has the info: Track No - Title - Artist - Album - Genre
My program was working fine until tonight when I added a function that looks up all the different genres of music and displays a list of the genres to the user (I later want to allow the user to select one of these genres and have a playlist created with all the mp3s in this genre).
Now whenever I execute the program, it stops when it reaches the part when the new function is used, saying:

Code:

lab1.exe has encountered a problem and needs to close.  We are sorry for the inconvenience.

I tried to Debug, and it gave me this message

Code:

Unhandled exception in mp3list.exe: 0xC0000005: Access violation

Does anyone know what the problem might be?
Here is the code I have written. The function that's causing the problem is the 'lookupgenres' function.

Code:

/* A program to take information from a .txt file and store it in structures
   which can be looked up via an array of pointers */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <console_lib.h>
#include <conio.h>

typedef struct mp3info
{
	char title[100];
	char artist[100];
	char album[100];
	char genre[100];
} SONG;

void lookupgenres ( SONG *array[20001] )
{
	typedef struct genrelist
	{
		char name[100];
		struct genrelist *next;
	} GENRES;

	int tracknumber;
	GENRES genre;
	GENRES *current;
	int compare;
	int count;

	/* Check through all tracks for different genres */

	for ( tracknumber = 1; tracknumber <= 100; tracknumber++ )
	{
		/* Check to see if genre has been added */

		/* If the genre list is empty, the check does not need to be made and the
		   genre of the first track can be added to the list */

		if ( genre.name == NULL )
			strcpy ( genre.name, array[tracknumber]->genre );
		else
		{
			compare = 1;
			current = &genre;

			compare = strcmp ( current->name, array[tracknumber]->genre );

			while ( ( compare != 0 ) && ( current->next != NULL ) )
			{
				current = current->next;
				compare = strcmp ( current->name, array[tracknumber]->genre );
			}

			/* If the genre has not been added to the list, add it */

			if ( compare != 0 )
			{
				current = &genre;
				while ( current->next != NULL )
					current = current->next;
				current->next = malloc ( sizeof ( GENRES ) );
				current = current->next;
				strcpy ( current->name, array[tracknumber]->genre );
			}
		}
	}

	current = &genre;

	for ( count = 1; count != 0 ; count++ )
	{
		printf ( "%d - %s\n", count, current->name );
		if ( current->next != NULL )
			current = current->next;
		else
			count = 0;
	}
}

/* ------------------------------------------------------------------------ */

int main (void)
{
	char string[500];
	int tracknumber;
	SONG *current;
	SONG *array[20001];

	/* Open file mp3list.txt for reading */

	FILE *fp;
	fp = fopen ( "C:\\mp3list.txt", "r" );

	while ( tracknumber < 100 )
	{
		fgets ( string, 500, fp );
		current = store ( string, &tracknumber );
		array[tracknumber] = current;
		printf ( "%d - %s - %s - %s - %s", tracknumber, current->title, current->artist, current->album, current->genre );
	}

	printf ( "Loading Complete!\n\n");

	lookupgenres ( array );

	return 0;

}

If anyone has any idea where I might be going wrong with this the help would be really appreciated!

That appears to be some sort of segfault. Could be your store function. At least, that's what I think it is, right now.

Use a debugger, makes it easy to find where you are segfaulting.

Array indexes start at zero, not one.

Code:

for ( tracknumber = 1; tracknumber <= 100; tracknumber++ )
	{
		/* Check to see if genre has been added */

		/* If the genre list is empty, the check does not need to be made and the
		   genre of the first track can be added to the list */

		if ( genre.name == NULL )
			strcpy ( genre.name, array[tracknumber]->genre );

Also, genre.name will never be NULL because it is an array, not a pointer.

Code:

GENRES genre;
GENRES *current;

You can't use these pointers to walk through your array, and you genre->next isn't ever pointed to anything useful. So anything you do with it is undefined behavior (ie: bad). Such as:

Code:

while ( ( compare != 0 ) && ( current->next != NULL ) )
			{
				current = current->next;

That'll get you started.

My program was working fine until tonight when I added a function

Very tempting to just say "I bet it's your new function."

Guess what? I'd have been right.


Quzah.

if ( genre.name == NULL )

always false

> current = store ( string, &tracknumber );
It's also possible that this is also messing with memory given that your new function shows weaknesses.

When dealing with memory problems, cause and effect are usually in two very different places in the code. Meaning you might get to the point where nobody can see anything wrong with lookupgenres(), yet its still crashing.