The function void *pthread_getspecific(pthread_key_t key) shall return the value currently bound to the specified key on behalf of the calling thread. Calling pthread_getspecific() with a key value not obtained from pthread_key_create() or after key has been deleted with pthread_key_delete() is undefined. pthread_getspecific can be called from a thread-specific data destructor function. A call to pthread_getspecific() for the thread-specific data key being destroyed shall return the value NULL, unless the value is changed (after the destructor starts) by a call to pthread_setspecific(). It shall return the thread-specific data value associated with the given 'key'. If no thread-specific data value is associated with 'key, then the value NULL shall be returned. It does not return any errors.