pset5 load null pointer issue

Question

Working through the load portion of pset5. Everything compiles, but when I run valgrind it looks as if nothing is actually loading in, with the error of "null pointer passed as argument 1, which is declared to never be null."

In valgrind it is pointing to the following code within my hash function:

int hash(char *w)    // Hash function 
{
    hash_value = 1;
    int len = strlen(w);
....}

However I think the error is actually taking place when inserting new values into the hashtable:

FILE* dict = fopen(dictionary, "r");
char word[LENGTH+1];
if (dict == NULL)
{
    fprintf(stderr, "Invalid Dictionary");
    return 1;
}

while (fscanf(dict, "%s", word) != EOF)
{
node* new_node = malloc(sizeof(node));
    // Check if malloc succeeeded
    if (new_node == NULL)
    {
        //unload(dict);
        return 1;
    }
word_count++;
//new_node->word = word; //Insert Word into the nodes "word" section

//Hash value.
hash_value = hash(word);
strcpy(new_node->word, word);
 if (hashtable[hash_value] == NULL)
    {
        hashtable[hash_value] = new_node;
        new_node->next = NULL;
    }
else
    {
        new_node->next = hashtable[hash_value];
        hashtable[hash_value] = new_node;
    }
}

Do I have to do something different since I'm inserting into a hashtable? I initialize hashtable earlier on as follows:

node* hashtable[15625]; //Number of buckets for hashtable 

Any hints or pointers appreciated!

Answer 1

char *word = NULL;

while (fscanf(dict, "%s", word) != EOF)

The problem lies with word. It's a pointer to NULL. Next, the fscanf does a read and stores it at NULL, the infinite bit bucket. In other words, it discards it.

Either space for the read has to be malloc'd and the address stored in word, or, a different approach, create a char array large enough to hold any word plus the end of string marker.

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