stuck on small bug

[bigwillys111]

I have a program I'm working on that will read a txt file and count the unique words and how many times that word appears.

I'm getting an error when I try to run it that says "Debug Error! Run-Time Check Failure #3 - The variable 'last' is being used without being initialized."

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <sys/stat.h>

/*
	Custom list data type
*/
typedef struct list_s {
	struct list_s *prev, *next;
	char *text;
	int count;
} list_t;

/*
	Add text to the list.
	Returns the list on sucess.
	Returns NULL on addition failures,
		i.e. the text already there or no memory available.
*/
static list_t *list_add(list_t *list, char *text)
{
	list_t *last, *node, *n;

	for (n = list; n != NULL; n = n->next) {
		if (!stricmp(n->text, text)) {
			n->count++;
			return NULL;
		}
		last = n;
	}

	if (!(node = malloc(sizeof(list_t)))) {
		return NULL;
	}
	node->text = strdup(text);
	node->count = 1;
	node->next = NULL;

	if (last == NULL) {
		node->prev = NULL;
		return node;
	}

	node->prev = last;
	last->next = node;

	return list;
}

/*
	free the whole list and its associated data
*/
static void list_free(list_t *list)
{
	list_t *node = list;

	while (node != NULL) {
		list_t *next = node->next;
		if (node->text)
			free(node->text);
		free(node);
		node = next;
	}
}

/*
	simple print of word list
*/
static void list_print(list_t *list)
{
	list_t *node;
	for (node = list; node; node = node->next)
		printf("%s %d\n", node->text, node->count);
}

/*
	simple file print of word list
*/
static void list_fprintf(FILE *fp, list_t *list)
{
	list_t *node;
	for (node = list; node; node = node->next)
		fprintf(fp, "%s %d\n", node->text, node->count);
}


list_t *word_list = NULL; /* our word list */


int main(int argc, char **argv)
{
	struct stat buff;
	int size;
	FILE *file = NULL;
	unsigned char *data = NULL;
	char *ptr, *text = NULL;
	list_t *list = NULL;

	/* check arguments for input */
	if (argc < 2) {
		printf("Usage: %s <INPUT> [OUTPUT]\n", argv[0]);
		return -1;
	}

	/* get input file information */
	if (stat(argv[1], &buff)) {
		printf("Error: can't open file \"%s\"\n", argv[1]);
		return -1;
	}
	size = buff.st_size;
	if (size < 1) {
		printf("Info: empty file\n");
		return 0;
	}

	/* allocate memory to load the file */
	if (!(data = malloc(size + 1))) {
		printf("Error: not enough memory\n");
		return -1;
	}

	/* now load the file to memory */
	if (!(file = fopen(argv[1], "rb"))) {
		printf("Error: can't open file \"%s\"\n", argv[1]);
		return -1;
	}
	fread(data, size, 1, file);
	data[size] = 0;
	fclose(file);

	/* reassign to standard output */
	file = stdout;

	/* now parse the data */
	for (ptr = data; ptr - data < size; ) {
		int c = *ptr;
		if (isalnum(c)) {
			if (!text) /* word starts */
				text = ptr;
		} else {
			if (text) { /* word ends */
				c = *ptr;
				*ptr = 0;

				/* add word to the list */
				if (list = list_add(word_list, text))
					word_list = list;

				*ptr = c;

				text = NULL; /* reset state */
			}
		}
		ptr++;
	}

	/* free memory */
	free(data);

	/* optionally opens output file */
	if (argc > 2) {
		if (!(file = fopen(argv[2], "w"))) {
			printf("Info: can't open \"%s\"\n", argv[2]);
			file = stdout;
		}
	}

	/* now output the list */
	/*list_print(word_list); */

	list_fprintf(file, word_list);

	/* optionally close the file */
	if (file && file != stdout)
		fclose(file);

	/* free the list */
	list_free(word_list);

	return 0; /* done */
}

[Salem]

That's because there is a path through list_add() where you don't do
last = someValidPointer;

before you try
if ( last == NULL )

As error messages go, it's pretty damn obvious what it means.

[bigwillys111]

I apologize for posting something so simple. I have only been messing with C for a couple months and have only done a couple simple programs with it.

Anyways I fixed the error by adding this

last = 0;