Char Linked list with Buffer Ring in C - c

Question

I have a server and a client. The client can send request like ADD to list by entering ADD:Joe:2 it should add to list. Key = Joe Value =2.
I'm trying to ADD a key:value into a linked list that uses a buffer ring of max 5 elements. When the linked list reaches the max size of elements(5) and a new key:value is entered, the oldest element is overwritten with the new element.
Every time I adding it seems to add fine, but when the max size is reached and tries to delete the first KEY:VALUE it crashes.
Add to LIST:
void push_item(struct item** Front,struct item** Rear,char *new_key,char *new_value,int newsockfd)
{
char buffer [50] = {0};
struct item* new_node = malloc(sizeof(struct item));
strcpy(new_node->value,new_value);
strcpy(new_node->key,new_key);
//new_node->next = NULL;
if(p_size==5)
{
char *itemVal;
char *itemKey;
/* if queue is empty */
if ( *Front == NULL )
{
printf ( "List is empty");
}
else
{
if (*Front == *Rear)
{
strcpy(itemVal,(*Front)->value);
strcpy(itemKey,(*Front)->key);
free(*Front);
*Front = NULL ;
*Rear = NULL ;
}
else
{
//delete node
new_node = *Front;
strcpy(itemVal,new_node->value);
strcpy(itemKey,new_node->key);
*Front=(*Front)->next;
(*Rear)->next=*Front;
free(new_node);
}
printf("Node deleted Key: %s Value: %s",itemKey,itemVal);
}
}
else
{
*Rear=new_node;
(*Rear)->next=new_node;
if(*Front==NULL)
{
(*Front)=new_node;
p_size++;
}
else
{
(*Rear)->next=new_node;
p_size++;
printf("Elements in List: %d\n",p_size);
}
}
sprintf(buffer,"Added");
int num_bytes = write(newsockfd, buffer, strlen(buffer));
if (num_bytes < 0)
{
fprintf(stderr, "Thread ERROR: write() failed\n");
}
}
Server:
struct item *Front = NULL;
struct item *Rear = NULL;
char buffer[BUFFER_SIZE] = {0};
void* handle_client(void *socket)
{
int newsockfd = (int)socket;
pthread_t thread_id = pthread_self();
printf("----------\nThread %lu using socket %x\n", (unsigned long)thread_id, newsockfd);
/* Start communicating */
int num_bytes = read(newsockfd, buffer, BUFFER_SIZE-1);
if (num_bytes < 0) {
fprintf(stderr, "Thread %lu ERROR: read() failed\n", (unsigned long)thread_id);
return NULL;
}
printf("Thread %lu recieved request\n", (unsigned long)thread_id);
if(strncmp(buffer,"ADD",3)==0)
{
char* key = buffer+4;
int charIndex;
char *new_value = strchr(buffer+4 , ':')+1;
charIndex = (int)(new_value-buffer)-1;
buffer[charIndex] = '\0';
push_item(&Front,&Rear,key,new_value,newsockfd);
printf("Value:%s Key:%s\n",new_value,key);
}
EDIT:
Images of CMD :
Left cmd is the client and the right one is the server
The p_size represents the current number of elements in the linked list.
It Crashes after it enters the if condition P_size == 5.

Answer 1

When looking on the push_item() function for the problem located in case of if(p_size==5), the error is when writing data of the node to be removed.
Error 1 - temporary itemVal and itemKey are declared as char * but never allocated to an array.
// To do
strcpy(itemVal,(*Front)->value);
strcpy(itemKey,(*Front)->key);
// or
strcpy(itemVal,new_node->value);
strcpy(itemKey,new_node->key);
Both char *itemVal; and char *itemKey; shall be allocated.
// Local variables (STR_SIZE has to be adjusted)
char itemVal[STR_SIZE+1];
char itemKey[STR_SIZE+1];
Warning 1 - but solving that issue will reveal a malfunction in the Ring Buffer algorithm when using linked-list.
In the push_item() function, the writing/push pointer *Front and
the reading/pop pointer *Rear are managed independently. When the
Ring Buffer is full (if(p_size==5)) the new item is deleted instead
of the oldest one.