Segmentation fault when freeing at specific indices - c

Question

Following this tutorial on Hash Tables, I implemented a sort of simplified version. However, whenever delete_entry is called on every 4th index(4,8,12...), I get a segmentation fault. Else, it works fine
Here's the code I run:
#include <stdio.h>
typedef struct {
int key;
int value;
} entry;
typedef struct{
int length;
int count;
entry** items;
} table;
entry *new_entry(const int, const int);
table *create_table();
void destroy_table(table *t);
void delete_entry(entry *e);
void table_insert(table *, const int, const int);
int main(){
table *new_table = create_table();
printf("[INFO] Created new table successfully!!\n");
for(int i=0; i<16; i++){
table_insert(new_table,i,i+i);
}
printf("[INFO] Inserted %d items\n",new_table->count);
destroy_table(new_table);
printf("[INFO] Destroyed table successfully!!\n");
return 0;
}
table *create_table(){
table *new_table = malloc(sizeof(table));
if(new_table == NULL){
printf("[WARNING] Malloc failure, returning NULL");
return NULL;
}
new_table->length = 16;
new_table->count = 0;
new_table->items = calloc((size_t)new_table->length, sizeof(entry*));
return new_table;
}
entry *new_entry(const int k, const int val){
entry *new_item = malloc(sizeof(entry));
if(new_item == NULL){
printf("[WARNING] Malloc failure, returning NULL");
return NULL;
}
new_item->key = k;
new_item->value = val;
return new_item;
}
void destroy_table(table *t){
for(int i=0; i<t->count; i++){
if(i== 4 || i == 8|| i==12) //Without this program terminates after 3rd index
continue;
entry *e = t->items[i];
if (e != NULL){
delete_entry(e);
}
}
free(t->items);
free(t);
}
void delete_entry(entry *e){
free(e->key);
free(e->value);
free(e);
}
void table_insert(table *t, const int k, const int v){
entry *e = new_entry(k, v);
t->items[t->count] = e;
t->count++;
}

Answer 1

Try to replace delete_entry() with:
void delete_entry(entry *e){
free(e);
}
Freeing values of integers e->key and e->value will likely result in Undefined Behavior. You should use free() only on objects produced by malloc() and friends.