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/* @test

 * @bug 8166188

 * @requires vm.opt.ExplicitGCInvokesConcurrent != true

 * @summary Test return of JNI weak global refs from native calls.

 * @modules java.base

 * @run main/othervm/native -Xint ReturnJNIWeak

 * @run main/othervm/native -Xcomp ReturnJNIWeak

 */

public final class ReturnJNIWeak {

    static {

        System.loadLibrary("ReturnJNIWeak");

    }

    private static final class TestObject {

        public final int value;

        public TestObject(int value) {

            this.value = value;

        }

    }

    private static volatile TestObject testObject = null;

    private static native void registerObject(Object o);

    private static native void unregisterObject();

    private static native Object getObject();

    // Create the test object and record it both strongly and weakly.

    private static void remember(int value) {

        TestObject o = new TestObject(value);

        registerObject(o);

        testObject = o;

    }

    // Remove both strong and weak references to the current test object.

    private static void forget() {

        unregisterObject();

        testObject = null;

    }

    // Verify the weakly recorded object

    private static void checkValue(int value) throws Exception {

        Object o = getObject();

        if (o == null) {

            throw new RuntimeException("Weak reference unexpectedly null");

        }

        TestObject t = (TestObject)o;

        if (t.value != value) {

            throw new RuntimeException("Incorrect value");

        }

    }

    // Verify we can create a weak reference and get it back.

    private static void testSanity() throws Exception {

        System.out.println("running testSanity");

        int value = 5;

        try {

            remember(value);

            checkValue(value);

        } finally {

            forget();

        }

    }

    // Verify weak ref value survives across collection if strong ref exists.

    private static void testSurvival() throws Exception {

        System.out.println("running testSurvival");

        int value = 10;

        try {

            remember(value);

            checkValue(value);

            System.gc();

            // Verify weak ref still has expected value.

            checkValue(value);

        } finally {

            forget();

        }

    }

    // Verify weak ref cleared if no strong ref exists.

    private static void testClear() throws Exception {

        System.out.println("running testClear");

        int value = 15;

        try {

          remember(value);

          checkValue(value);

          // Verify still good.

          checkValue(value);

          // Drop reference.

          testObject = null;

          System.gc();

          // Verify weak ref cleared as expected.

          Object recorded = getObject();

          if (recorded != null) {

            throw new RuntimeException("expected clear");

          }

        } finally {

          forget();

        }

    }

    public static void main(String[] args) throws Exception {

        testSanity();

        testSurvival();

        testClear();

    }

}