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#include <pthread.h>
#include <stdio.h>
#include<malloc.h>

#define MAX_NUMBER_OF_THREADS 3

/* function prototypes */
void destructor(void * data);
void* function();
void add_data();
void print_data();

/* global key to the thread specific data */
pthread_key_t key;

void destructor(void * data){
    pthread_setspecific(key, NULL); // thread specific should be cleared (could be sensitive)
    free(data);
}


/* Getting some random data */
int *get_data(){
    int *arr = malloc(2*sizeof(int));
    *arr = rand();
    *(arr+1) = rand();
    return arr;
}

void *function()
{
    add_data();
    print_data();
    pthread_exit(NULL);
}

void add_data()
{
    int *data = get_data();
    printf("some data = %p\n",data);
    pthread_setspecific( key,
    (void *) data);
}

void print_data()
{
    /* get this thread's global data from key */
    int *data = pthread_getspecific(key);
    printf("thread id = %u, data[0] = %d, data[1] = %d \n",(size_t)pthread_self(),*data,*(data+1));
}

int main( void )
{
    int i;
    pthread_t thread_id[MAX_NUMBER_OF_THREADS];

    /* create the thread specific data key before creating the threads */
    pthread_key_create( &key, destructor );

    /* create thread that will use the key */
    for(i =0; i < MAX_NUMBER_OF_THREADS; i++){
        pthread_create( &thread_id[i], NULL, function, NULL );
    }
 
    for(i=0;i < MAX_NUMBER_OF_THREADS; i++){
        int ret = pthread_join(thread_id[i], NULL);
        if(ret !=0){
            /* Handle Error */
        }
    }
    pthread_key_delete(key);
}