Word occurrences and line numbers - c

Question

I'm making a program that generates a text file that contains the occurrences of words and the line number of each occurrence of another text file. I'm using an AVL tree struct that contains the word and a linked list struct that contains one node for each line number. Here are the struct definitions:
struct llnode {
struct llnode *next;
int num;
};
struct node {
char *word;
struct llnode *head;
struct node *left;
struct node *right;
int height;
};
I get a segmentation fault when I try to print to the text file using the below functions.
void listprint(struct llnode *p) {
if(p->next == NULL) {
printf("%d", p->num);
} else {
printf("%d, ", p->num);
listprint(p->next);
}
}
void treeprint(struct node *p) {
if(p != NULL) {
treeprint(p->left);
printf("%s: ", p->word);
listprint(p->head);
treeprint(p->right);
}
}
Specifically the problem is this line
if(p->next == null) {
gdb gives me
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000000
Thanks for your help.
Edit:
void listinsert(struct llnode *p) {
struct llnode *prev = p;
while(p != NULL) {
prev = p;
p = p->next;
}
p = lalloc();
p->num = line;
p->next = NULL;
prev->next = p;
struct node *addtree(struct node *p, char *w) {
int cond;
if(p == NULL) {
p = talloc();
p->head = NULL;
p->word = mystrdup(w);
p->head = listinsert(p->head);
p->left = p->right = NULL;
} else if((cond = strcmp(w, p->word)) == 0) {
listinsert(p->head);
} else if(cond < 0) {
p->left = addtree(p->left, w);
if(height(p->left)-height(p->right) == 2) {
if(strcmp(w, p->left->word) < 0) {
p = singleleft(p);
} else {
p = doubleleft(p);
}
}
} else {
p->right = addtree(p->right, w);
if(height(p->right)-height(p->left) == 2) {
if(strcmp(w, p->right->word) > 0) {
p = singleright(p);
} else {
p = singleleft(p);
}
}
}
return p;
int getword(char *word, int lim) {
int c;
char *w = word;
while(isspace(c = getch()));
if(c == '\n') {
line++;
}
if(c != EOF) {
*w++ = c;
}
if(!isalpha(c)) {
*w = '\0';
return c;
}
for( ; --lim > 0; w++) {
if(!isalnum(*w = getch())) {
ungetch(*w);
break;
}
}
*w = '\0';
return word[0];

Answer 1

In listprint, you are not checking if p is null before checking if p->next is null.

Answer 2

Try this.
llnode* listinsert(struct llnode *p) {
struct llnode *prev = p;
if( NULL == prev ) {
prev = lalloc();
prev->num= line;
prev->next = NULL;
return prev;
}
while(prev->next != NULL) {
prev = prev->next;
}
prev->next = lalloc();
prev = prev->next;
prev->num = line;
prev->next = NULL;
return p;
}