user2506293 user2506293 - 1 month ago 17
C Question

Setting Pointer References

I have a rehash function for a hash table like so:

int hash_rehash(hash_table *ht) {
list *l = hash_list(ht); // creates a linked list of hash table members
hash_table *nht = hash_createTable(ht->buckets * 2, ht->maxLoad, ht->hash); // new hash table with 2x the buckets
unsigned int i = 0;
list_node *c = l->head;
hash_destroyTable(ht); // destroy the old hash table
for (; i < l->size; i++, c = c->next) {
hash_insert(nht, c->data); // loop through linked list to re-insert old hash table members
}
*ht = *nht; // reference of old hash table = reference of new hash table?
list_destroyList(l);
return 0;
}


However if I destroy the old hash table I run into a SIGABRT error when reading out all the members of the new table because nht is using the same memory I allocated for ht. What's the correct way to change the old hash table ht to reference the new hash table nht?

Answer

Accept a hash_table ** instead of a hash_table *. Then if your caller has a hash_table *ht, they will call hash_rehash(&ht), allowing the function to modify ht.