Hashtables in C

Question

In this code I need to initialize, insert in a hashtable and print the values in these 2 stuctures:

• hashTable (number of nodes and a double pointer to the struct hashElem)
• hashElem (containing a char key and an int that counts every time there's been a node with the same key)

The error (see line in the print function) it gives me is this:
warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char **' [-Wformat=]

#include <stdio.h>
#include <stdlib.h>
//GNU.txt at the end
#define m 89
 
typedef char *keyType;
typedef int valueType;
 
typedef struct hashElem{
    keyType *key;
    valueType freq;
}hashElem;
 
struct hashTable{
    int N;
    hashElem **array;
};
 
int hash(char *key, int i){
    int sum=0;
    while( *key!='\0' ){
        sum = sum + *key;
        key++;
    }
    return (sum+i)%m;
}
 
struct hashTable *createHashTable(){
    struct hashTable *ht=malloc(sizeof(struct hashTable));
    if( ht==NULL )
        printf("Error in memory allocation.\n");
 
    ht->N = 0;
    ht->array=malloc(m*sizeof(hashElem *));
    if( ht->array==NULL )
        printf("Error in memory allocation.\n");
    for(int i=0; i<m; i++ )
        ht->array[i] = NULL;
    return ht;
}
 
void freeHashTable(struct hashTable *ht){
    free(ht->array);
    free(ht);
}
 
void printHashTable(struct hashTable *ht){
    printf("Printing hash table without sorting:\n");
    for(int i=0; i<m; i++)
        if( ht->array[i]!=NULL )
            printf("%s: %d\n", ht->array[i]->key, ht->array[i]->freq);
    printf("---------end.\n");
}
 
void printOrderedHashTable(struct hashTable *ht){
    printf("Printing sorted hash table:\n");
    //add sorting
    for(int i=0; i<m; i++)
        if( ht->array[i]!=NULL )
            printf("%s: %d\n", ht->array[i]->key, ht->array[i]->freq);
    printf("---------end.\n");
}
 
int insert(struct hashTable *ht, keyType key){
    int index;
    int i=0;
    int collision=1;
    while( collision && i<m ){
        index = hash(key, i);
        if( ht->array[index]!=NULL ){
            if( ht->array[index]!=key ){
                collision=1;
                i++;
            }else
                ht->array[index]->freq++;
        }else{
            collision = 0;
            hashElem *s;
            s=malloc(sizeof(hashElem));
            s->freq++;
            s->key = key;
            ht->array[index] = s;
            ht->N++;
        }
    }
    if( collision==1 )
        return -1;
    else
        return 1;
}
 
int main(){
    struct hashTable *ht;
    ht=createHashTable();
 
    FILE *f;
    f=fopen("GNU.txt", "r"); //you can find the file at the end
    if( f==NULL )
        printf("Error in file opening.\n");
 
    char input[255];
    printf("Reading file...\n");
    while( !feof(f) && ht->N<m ){
        fscanf(f, "%s", input);
        insert(ht, input);
    }
    fclose(f);
 
    printHashTable(ht);
    //printOrderedHashTable(ht);
    freeHashTable(ht);
    return 0;
}
 
 
 
// GNU.txt file
 
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Answer 1

The problem is in the linked code in pastebin:

typedef char *keyType;
typedef int valueType;

typedef struct hashElem{
    keyType *key;
    ...

Here keyType is an alias of char *, but then, in the struct, you add an extra * in keyType *key;, this results in:

typedef struct hashElem{
    char **key;

That's why your compiler complains about:

warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char **' 

Fix-it using:

typedef struct hashElem{
    char *key; // As in the snippet showed in your thread :)

or

typedef struct hashElem{
    keyType key; // Hidding pointers with typedefs is a bad idea