Segmentation Fault in Producer Consumer C - c

Question

I tried to simulate the producer consumer problem using bounder buffer in C and threads.
Mutex and semaphores are also used.
The expected output is to display the state of buffer every time an item is produced or consumed.
Buffer size is fixed as 10. Initially buffer items are all -1. When a producer produces an item into it, the item replaces -1.
Item in 0th index is 0 ,1st index is 1 and so on.....which doesn't matter.
The program asks the number of producers and consumer we want to create.
The production is working fine....but not consumption.
Segmentation fault arises in Thread 1.I am not sure what Thread 1 is.
I tried to debug using GDB many times....without no hope.
// Producer consumer.
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
#include <stdlib.h>
#include <unistd.h>
#define TRUE 1
int buff_size=10,i;
int buffer[25];
pthread_mutex_t mutex;
sem_t full, empty;
int counter = 0;
int consume_count=0; //No of Consumers created
int produce_count=0; //No of Producers created
void initializeData()
{
sem_init(&full, 0, 0);
sem_init(&empty, 0, buff_size);
pthread_mutex_init(&mutex, NULL);
}
int insert_item(int counter)
{
if (counter < buff_size) {
buffer[counter] = counter;
counter++;
//produce_count++;
return 0;
}
else {
printf("\n[BUFFER FULL!]");
return -1;
}
}
int remove_item()
{
printf("\n[GOING TO REMOVE AN ITEM]\n");
if (buffer[counter-1] != -1) {
buffer[counter-1] = -1;
counter--;
//consume_count++; // Commented out...
return 0;
}
else {
printf("\n[EMPTY]\n");
return -1;
}
}
void *producer(void *arg)
{
int RET = 0;
while( TRUE ) {
sem_wait(&empty);
pthread_mutex_lock(&mutex);
RET = insert_item(counter);
if (RET){
printf("\nProducer Sleeping...zzZZ\n");
sleep(2);
}
pthread_mutex_unlock(&mutex);
sem_post(&full);
if(!RET)
printf("\n[ INSERTED ]\n" );
printf("\n");
for(i=0; i < buff_size ;i++)
printf("[%d] ",buffer[i]);
printf("\n");
sleep(3);
} // end of while...
}
void *consumer(void *arg)
{
int RET = 0;
while( TRUE ) {
sem_wait(&full);
pthread_mutex_lock(&mutex);
RET = remove_item(buffer);
if (RET){
printf("\nConsumer Sleeping\n");
sleep(3);
}
pthread_mutex_unlock(&mutex);
sem_post(&empty);
if(!RET) {
printf("\nConsumed\n");
printf("\n");
}
for(i=0 ; i < buff_size ; i++)
printf("%4d",buffer[i]);
printf("\n");
sleep(2);
} //end of while...
}
void main()
{
int produce, consume;
pthread_t *prod;//thread ID
pthread_t *cons;//thread ID
printf("\nEnter the no of producers: ");
scanf("%d",&produce);
printf("\nEnter the no of consumers: ");
scanf("%d",&consume);
putchar('\n');
for (i=0; i < buff_size; i++)
buffer[i] = -1;
for (i=0; i < buff_size; i++)
printf("[%d] ", buffer[i]);
printf("\n");
initializeData();
for (i = 0; i < produce; i++)
{
pthread_create(&prod[i], NULL, producer, NULL);
produce_count++;
}
for (i = 0; i < consume; i++)
{
pthread_create(&cons[i], NULL, consumer, NULL);
consume_count++;
printf("AAAAA");
}
/*for (i = 0; i < produce; i++)
pthread_join(producer, NULL);
for (i = 0; i < consume; i++)
pthread_join(consumer, NULL);*/
printf("\n===============\n[ PRODUCED: %d ]", produce_count);
printf("\n[ CONSUMED: %d ]\n==============", consume_count);
}

Answer 1

pthread_create(&prod[i], NULL, producer, NULL);
In this call pthread_create will create new thread and try to return thread id in prod[i]
But:
pthread_t *prod;//thread ID
pthread_t *cons;//thread ID
These are uninitiaised pointers, if you want to collect threadids in them, you need to allocate memory to them with malloc like:
prod = malloc(sizeof(pthread_t) * produce);
cons = malloc(sizeof(pthread_t) * consume);
Otherwise pthread_create will be storing threadid in invalid memory leading to segment fault