Availability:built-in
thread_join(+Id,
-Status)Wait for the termination of the thread with the given Id.
Then unify the result status of the thread with Status. After
this call, Id becomes invalid and all resources associated
with the thread are reclaimed. It is not allowed for two threads to join
the same thread and the thread being joined cannot be detached
(see the
detached(true) option for thread_create/3
and thread_detach/1).
A thread that has been completed without thread_join/2
being called on it is partly reclaimed: the Prolog stacks are released
and the C thread is destroyed. A small data structure representing the
exit status of the thread is retained until thread_join/2
is called on the thread. Defined values for Status are:
- true
- The goal has been proven successfully.
- false
- The goal has failed.
- exception(Term)
- The thread is terminated on an exception. See print_message/2
to turn system exceptions into readable messages.
- exited(Term)
- The thread is terminated on thread_exit/1
using the argument Term.
Note that the pthread primitive pthread_join() cannot be
interrupted. Some systems provide pthread_timedjoin_np(). If this
is provided
thread_join/2
is implemented as a loop of timed joins with a 0.25 sec timeout while
signals are being tested after each timeout. Such systems allow
combining thread_join/2
with call_with_time_limit/2
as well as signalling threads blocked in thread_join/2
using thread_signal/2.
