Accessing structure within structure times 3? - c

Question

I have an assignment in C and I have trouble accessing different members within my structs(some levels deep). I understand the basic principles, but I kinda lose it somewhere. I have 3 structures, with the top one containing an array of the second, which in turn contains an array of the third. My current issue is using malloc the correct way. Here is some of my code. I would appreciate any kind of information or tip, because i still have a long way to go and as you can see the structures are kinda complicated.
.h file
typedef struct user {
char* userID;
int wallet;
bitCoinList userBC; //Also a list
senderTransList userSendList; //Yes it has lists too..
receiverTransList userReceiveList;
}user;
typedef struct bucket {
struct bucket* next;
user** users;
}bucket;
typedef struct hashtable {
unsigned int hashSize;
unsigned int bucketSize;
bucket** buckets;
}hashtable;
Here is my function for creating and initializing the hashtable..I get the error when I try to access users with HT->buckets->users (request for member users in something not a structure or a union)
.c file
// Creation and Initialization of HashTable
hashtable* createInit(unsigned int HTSize,unsigned int buckSize){
hashtable* HT = (hashtable*)malloc(sizeof(hashtable));
if(HT==NULL) {
printf("Error in hashtable memory allocation... \n");
return NULL;
}
HT->hashSize=HTSize;
HT->bucketSize=buckSize;
HT->buckets = malloc(HTSize * sizeof(HT->buckets));
if(HT->buckets==NULL) {
printf("Error in Buckets memory allocation... \n");
return NULL;
}
HT->buckets->users = malloc(buckSize * sizeof(HT->buckets->users));
if(HT->buckets->users==NULL) {
printf("Error in Users memory allocation... \n");
return NULL;
}
for(int i=0; i <HTSize; i++){
HT->buckets[i] = malloc(sizeof(bucket));
HT->buckets[i]->next = NULL;
if(HT->buckets[i]==NULL) {
printf("Error in Bucket %d memory allocation... \n",i);
return NULL;
}
for(int j=0; j <buckSize; j++){
HT->buckets[i]->users[j] = malloc(sizeof(user));
if(HT->buckets[i]==NULL) {
printf("Error in User %d memory allocation... \n",i);
return NULL;
}
}
}
return HT;
}

Answer 1

Because buckets is pointer to pointer type you need to:
(*(HT-> buckets)) ->users = ....
or
HT-> buckets[0] ->users = .... // or any other index depending of the program logic
or (for the n-th pointer)
(*(HT-> buckets + n)) ->users = ....
or
HT-> buckets[n] ->users = .... // or any other index depending of the program logic
This only the syntax answer and I do not analyze the program logic

Answer 2

At least one problem: wrong size allocation.
Allocate to the size of the data pointed to by HT->buckets, not to the size of the pointer.
Avoid mistakes. The below idiom is easy to code to, review and maintain.
ptr = malloc(sizeof *ptr * n);
// HT->buckets = malloc(HTSize * sizeof(HT->buckets));
HT->buckets = malloc(HTSize * sizeof *(HT->buckets));
// HT->buckets->users = malloc(buckSize * sizeof(HT->buckets->users));
HT->buckets->users = malloc(buckSize * sizeof *(HT->buckets->users));
// HT->buckets[i] = malloc(sizeof(bucket));
HT->buckets[i] = malloc(sizeof *(HT->buckets[i]));
// HT->buckets[i]->users[j] = malloc(sizeof(user));
HT->buckets[i]->users[j] = malloc(sizeof *(HT->buckets[i]->users[j]));