Thread: No Stack Error

Seg fault means that you are trying to access memory which you don't access to.
Check to see if fopen/malloc does not return NULL before using them.

Two problems become immediately obvious:

1. Your head element doesn't get a word assigned to it, so every time you do a strcmp, you're comparing an uninitialized pointer.

Code:

node_t *head = malloc(sizeof(node_t));

2. Your currWord only is allocating one byte to store the new word read from the file - basically, you only buffer enough space for one character, and since you're using fscanf, you have no way of knowing if you've overrun your buffer or not.

Code:

char *currWord = malloc(sizeof(char));

Originally Posted by Clayton Cuteri

Alright, I changed the currWord line, that makes sense but the first part doesnt matter, I assign a word to it when i run

Code:

 head = insert(currWord, head);

if head == NULL

Well, sort of, but only because you have another bug in the code (in your if statement, you're doing = NULL instead of == NULL). Think about how this code executes:

Code:

node_t *insert(char *currWord, node_t *head){

    node_t *curr_node = head, *new_node = malloc(sizeof(node_t));
    new_node->right = NULL;
    new_node->left = NULL;
    new_node->word = currWord;


    // At this point, new_node has a word in it, and curr_node 
    // points to head, which has all of its members undefined.
    
    // Head is not null; it points to the uninitialized block of memory returned by malloc() in main,
    //  so this if statement - assuming you fix the bug with = and == - will always be false
    if (head = NULL)
        return new_node;
    while (1) {
        // Now you get to this point, with currNode equal to
        // your head node.  curr_node->word is undefined, as are all
        // other members of curr_node
        if (strcmp(currWord, curr_node->word) > 0) {

You never pass a null value of HEAD in. malloc() will not return a null pointer, it returns a new node with uninitialized values. You pass this uninitialized head in to the insert function.

If you want it to work the way you think it does, you'd need this in main instead:

Code:

node_t *head = NULL;

Then head WOULD be null the first time through the loop, and the node would be created and assigned back to head.