/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
/* @test
* @bug 4178693
* @summary Ensure that null queue arguments don't crash the Reference handler
* @author Mark Reinhold
*/
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
public class NullQueue {
private static Reference r = null;
private static Thread findThread(String name) {
/* Find reference-handler thread */
ThreadGroup tg = Thread.currentThread().getThreadGroup();
for (ThreadGroup tgn = tg;
tgn != null;
tg = tgn, tgn = tg.getParent());
int nt = tg.activeCount();
Thread[] ts = new Thread[nt];
tg.enumerate(ts);
Thread refHandler = null;
for (int i = 0; i < ts.length; i++) {
if (ts[i].getName().equals(name)) return ts[i];
}
return null;
}
private static void fork(Runnable proc) throws InterruptedException {
Thread t = new Thread(proc);
t.start();
t.join();
}
public static void main(String[] args) throws Exception {
Thread refHandler = findThread("Reference Handler");
if (refHandler == null)
throw new Exception("Couldn't find Reference-handler thread");
if (!refHandler.isAlive())
throw new Exception("Reference-handler thread is not alive");
/* Invoke a Reference constructor, passing null for the queue */
fork(new Runnable() {
public void run() {
r = new WeakReference(new Object(), null);
}});
/* Force the reference to be cleared and enqueued by the GC */
for (int i = 0;; i++) {
Thread.sleep(10);
System.gc();
if (r.get() == null) break;
if (i >= 10)
throw new Exception("Couldn't cause weak ref to be cleared");
}
/* Check that the handler is still alive */
if (!refHandler.isAlive())
throw new Exception("Reference-handler thread died");
}
}