Test7190310.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * 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 7190310
 * @summary Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops
 * @run main/othervm/timeout=600 -Xbatch Test7190310
 */

/*
 * Note bug exhibits as infinite loop, timeout is helpful.
 * It should normally finish pretty quickly, but on some especially slow machines
 * it may not.  The companion _unsafe test lacks a timeout, but that is okay.
 */

import java.lang.ref.*;

public class Test7190310 {
  private static Object str = new Object() {
    public String toString() {
      return "The Object";
    }

    protected void finalize() throws Throwable {
      System.out.println("The Object is being finalized");
      super.finalize();
    }
  };
  private final static ReferenceQueue<Object> rq =
      new ReferenceQueue<Object>();
  private final static WeakReference<Object> wr =
      new WeakReference<Object>(str, rq);

  public static void main(String[] args)
      throws InterruptedException {
    Thread reader = new Thread() {
      public void run() {
        while (wr.get() != null) {
        }
        System.out.println("wr.get() returned null");
      }
    };

    Thread queueReader = new Thread() {
      public void run() {
        try {
          Reference<? extends Object> ref = rq.remove();
          System.out.println(ref);
          System.out.println("queueReader returned, ref==wr is "
              + (ref == wr));
        } catch (InterruptedException e) {
          System.err.println("Sleep interrupted - exiting");
        }
      }
    };

    reader.start();
    queueReader.start();

    Thread.sleep(1000);
    str = null;
    System.gc();
  }
}