CODEWITHSUNDEEP
c
Adam Wolf
Adam Wolf

Reputation: 309

Why do I get "initialization makes pointer from integer" when a function returns a pointer?

I am making an anagram program that takes a word and finds its anagrams then returns the list of anagrams from a given dictionary file. I am using a linked list as a hash map and a list for each node of the hash map (as per my assignment). I am pretty new to C so I am having a lot of issues with memory and pointers.

Some of the common errors I am getting when I compile: warning: initialization makes pointer from integer without a cast list *pList = getListFromMap(key); I don't understand this one, pList is a list pointer and getListFromMap is returning a list pointer.

conflicting types for getListFromMap() list *getListFromMap(int key) {

previous delcaration of getListFromMap was here getListFromMap(key); I read something about forward declaration? Though I am not sure how this works, I got an error trying it.

 typedef struct list {
     char *word;
     struct list *next;
 } list;

 typedef struct hashmap {
     list *words;
     int key;
     struct hashmap *next;
 } hashmap;

hashmap *pMapHead;
hashmap *pMapCurr;
list *pListHead;
list *pListCurrd;
int sum = 0; // sum of words
int hCount = 0;

void addWordsToMap(int key, list *words) { // create hashmap

    hashmap *pHash = pMapHead;
    pMapCurr = pHash;
    while (pMapCurr) {
            pMapCurr = pMapCurr->next;
    }
    pMapCurr->words = words;
    pMapCurr->key = key;
    pMapCurr->next = NULL;
    hCount += 1;
}


list *addWord(int key) {
    pListHead = getListFromMap(key); 
    pListCurr = pListHead;
    while (pListCurr) {
        pListCurr = pListCurr->next;    
    }
    pList->word = word;
    pList->next = NULL;
    pCurr->next = pList;
    pCurr = pList;

    return pListHead;
}

list *getListFromMap(int key) {
    hashmap *map = pMapHead;
    pMapCurr = map;
    while (pMapCurr != NULL) {
        if (pMapCurr->key == key) {
            return pMapCurr->words;
            free(map);
        }
        pMapCurr = pMapCurr->next;
    }
}

  int getSum(char* word) {
    int sum = 0;
    int i = 0;
    while (word[i]) {
        word[i] = toupper(word[i]);
        sum += word[i] - '@';
        i++;
    }
    return sum;
}

void loadWords() {
    FILE* dict = fopen("/home/akw54/Desktop/CS283/akw54-cs283-            summer2016/A1/dict", "r");
    if (dict == NULL) {
        return;
    }

    pListHead = (list *) malloc(sizeof(pListHead));
    pListCurr = pListHead;
    pMapHead = (hashmap *) malloc(sizeof(pMapHead));
    pMapCurr = pMapHead;
    int key = 0;    
    list wordList;
    char word[128];
    while(fgets(word, sizeof(word), dict) != NULL) {
        key = getSum(word);
        addWordsToMap(key, addWord(key));
    }   
    free(dict);
}

void main() {
    loadWords();
    free(pMapHead);
    free(pMapCurr);
    free(pListHead);
    free(pListCurr);
}

Upvotes: 0

Views: 696

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726479

The reason that you get "initialization makes pointer from integer" warning, despite the function returning a pointer, is somewhat obscure. The root case is that the function has no prototype, but that's not the whole story. According to pre-C99 rules, you were allowed to call a function that has no forward declaration, but the compiler must assume that all parameters are subject to default type promotions, and the return type is int as well.

That is why when the compiler sees pListHead = getListFromMap(key) call, it assumes that the function returns an int. In order to avoid this problem, add a forward declaration at the top of the file, right after the typedefs:

list *getListFromMap(int key);

Upvotes: 3

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