Discussion of these changes can be found on the Mercury developers
mailing list archives from June 2018.
COPYING.LIB:
Add a special linking exception to the LGPL.
*:
Update references to COPYING.LIB.
Clean up some minor errors that have accumulated in copyright
messages.
finalisers should be executed only if main/2 returns normally, it does not
throw an exception. The C backends already do this correctly but the Java
backend did not. The C# backend has the same bug, this patch does not fix
the C# backend.
java/runtime/MercuryThreadPool.java:
Add a parameter to the shutdown() method to specify whether the backend
is aborting.
In runMain(), run finalisers only if the runtime is exiting normally.
java/runtime/MercuryRuntime.java:
Add a new finalise() method that takes a parameter allowing standalone
Java applications to specify whether or not they are aborting when the
finalise the RTS.
doc/reference_manual.texi:
Specify the behaviour of finalise directives if main/2 terminates
with an uncaught exception.
samples/java_interface/standalone_java/JavaMain.java:
Conform to changes in MercuryRuntime.java.
When main/2 throws an exception we did not properly shutdown the thread pool
and therefore the JVM would not shut down. Simply calling shutdown() in a
finally block is insufficient because then the primordial thread may finish
before the worker thread is able to report the exception thrown by main/2.
This doesn't seem right because the JVM is supposed to wait for all the
non-daemon threads to finish before it exits. I suspect that the primordial
thread is closing stdout and stderr as it exits and therefore the exception
is never seen, but I don't know.
This change fixes the issue by ensuring that shutdown() is always called (in
a finally block) and that the main thread waits for the thread pool to
shutdown before it exits.
java/runtime/MercuryThreadPool.java:
runMain() will not exit until the worker threads have exited.
Create a new method waitForShutdown() that will wait for the thread pool
to shutdown.
Signal the main thread when a worker thread exits.
java/runtime/MercuryWorkerThread.java:
Worker threads now exit if their task raises an unhanded exception.
java/runtime/MercuryRuntime.java:
Allow standalone programs to have the same behavour as programs whose
entrypoint is written in Mercury.
The thread pool code used in the Java backend was tied the execution of
main/2. However if Mercury is used as a library the thread pool won't have
been started and threads created with thread.spawn would not be executed.
This patch makes it possible to start and stop the thread pool independently of
main/2 by calling startup() and shutdown(). These calls are called
implicitly by calling runMain(). The thread pool can also be started on
demand.
This patch also adds the MercuryRuntime class, which now contains methods
that may be called by users' Java code to interact with the Mercury runtime
system, including a new finalise() method.
java/runtime/MercuryThreadPool.java:
Add startup() method.
shutdown() method is now public and it's meaning has changed, it now
requests the shutdown rather than performing it.
Renamed some variables to make their meanings clearer.
java/runtime/JavaInternal.java:
Initialise the ThreadPool and MercuryOptions objects on demand.
Make all members of this class static to avoid confusion.
Add a private constructor.
java/runtime/MercuryRuntime.java:
Add methods that can be called by Mercury users to interact with the
runtime system. Including a convenient finalise() method that does all
the finalisation.
samples/java_interface/standalone_java/mercury_lib.m:
samples/java_interface/standalone_java/JavaMain.java:
Extend the standalone Java example so that it makes use of threads: Add
a fibs function in Mercury that uses concurrency and therefore starts
the thread pool; call it from the Java code.
Use the new finalise() method from the MercuryRuntime class inside of a
finally block.
samples/java_interface/standalone_java/Makefile:
Fix a minor error.
