While using pthread_key_create() to prepare a key to be used by various threads to maintain thread specific data, ensure that the data stored for a key is cleaned up after the key is no longer used, otherwise there could be potential memory leaks or misuse of data at the memory locations pointed to by the value.
Noncompliant Code Example
#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;
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, NULL );
   /* create threads 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);
       printf("Join return value for thread[%d] = %d",i,ret);
   }
   pthread_key_delete(key);
}
/* Getting some random data */
int *get_data()
{
   int *arr = malloc(2*sizeof(int));
   *arr = rand();
   *(arr+1) = rand();
   return arr;
}
void *function(void)
{
   add_data();
   print_data();
   pthread_exit(NULL);
}
void add_data(void)
{
   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
   * priority_key */
   int *data = pthread_getspecific(
   key );
   printf("thread id = %u, data[0] = %d, data[1] = %d \n",(size_t)pthread_self(),*data,*(data+1));
}
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