Thread-Specific Data: Example - Thread function.

void start_func(int thread_num)
{
    char    *buf;

    pthread_setspecific(key1, (void *)thread_num);
    buf = (char *) malloc(100);
    pthread_setspecific(key2, (void *)buf);
    pthread_setspecific(key1, (void *)NULL);
    buf = pthread_getspecific(key2);
    free(buf);
    pthread_setspecific(key2, (void *)NULL);
}

void destruct(void *value)
{
    free(value);
}