Question

I am trying to do a consumer / producer program with multiple consumers and producers. Im just trying to do something simple as have a producer add a random number to a shared array and have a consumer take it out.

I am getting errors though with the thread create. I see the error and what its saying but not sure how to fix it.

I will show you the producer function and main and i will separate them for easy reading.

#define BUFFER_SIZE 30

struct sharedBuffer{

int resource[BUFFER_SIZE];
int produced, consumed;
int in;
int out;

};

struct sharedBuffer shared;
struct sharedBuffer s_instance = { in:0, out:0, };

void *producer(void *arg){

int item = 0;
int itemCount =0;
//shared.in =0;
  while (1) {
    item = produceItem();           //generate the random number
   // while (shared.produced == BUFFER_SIZE);   //spin if buffer is full

    if(shared.produced == BUFFER_SIZE){
        fprintf (stdout, "Producer added : %d items \n",  shared.produced);
       return NULL;

    }
    /* put new item in buffer */
    shared.resource[shared.in] = item;
    shared.in = (shared.in+1) % BUFFER_SIZE;
    shared.resource[shared.in] = item;
    fprintf (stdout, "Producer added: %d \n",  item);
    shared.produced++;
    //item++;
    itemCount++;
}
}

Here is main()

int main(int argc, char* argv[])
{

int i;
int result;
int num_producers;
int num_consumers;

pthread_attr_t attrs;
pthread_attr_init (&attrs);
//int producerArray[num_producers],consumerArray[num_consumers];
pthread_t producer[num_producers],consumer[num_consumers];

printf("Enter the number of Producers: \n");

scanf("%d", &num_producers);

printf("Enter the number of Consumers: \n");

scanf("%d", &num_consumers);  

for(i=0; i< num_producers; i++)
{
    //producerArray[i]=0;
    //pthread_create(&producer[i],NULL, producer,&producerArray[i]);
    pthread_create(&producer[i],NULL, producer,NULL);
}

for(i=0; i< num_consumers; i++)
{
    //consumerArray[i]=0;
    // pthread_create(&tid[i], NULL, &compute_prime, NULL);
    //pthread_create(&consumer[i],NULL, consumer, &consumerArray[i]);
    pthread_create(&consumer[i], NULL, consumer, NULL);
}

for(i=0;i<num_producers;i++)
{
    pthread_join(producer[i],NULL);
    //printf("\nThe Producer (%d) produced: [%d] Items",i,producerArray[i]);
    sleep(1);
}

return 0;
}

Here is the error i am getting.

Consumer_producer2.c:125: warning: passing argument 3 of âpthread_createâ from  incompatible pointer type
/usr/include/pthread.h:227: note: expected âvoid * (*)(void *)â but argument is of type âpthread_t *â
Consumer_producer2.c:133: warning: passing argument 3 of âpthread_createâ from incompatible pointer type
/usr/include/pthread.h:227: note: expected âvoid * (*)(void *)â but argument is of type âpthread_t *â

if i run it i get a Segmentation fault
Thank you.

Answer 1

You’ve defeated yourself with your naming scheme: You have both a free function called producer and a local array called producer. Pick better names that are unique, and you should be able to fix this.