Description

   This routine obtains the detachstate attribute of a thread
   attributes object. This attribute specifies whether threads
   created using the specified thread attributes object are created
   in a detached state.

   On successful completion, this routine returns a zero and the
   detachstate attribute is set in detachstate. A value of PTHREAD_
   CREATE_JOINABLE indicates the thread is not detached, and a value
   of PTHREAD_CREATE_DETACHED indicates the thread is detached.

   See the pthread_attr_setdetachstate() description for information
   about the detachstate attribute.