1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
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  23 
  24 /* @test
  25  * @bug 8166188
  26  * @requires vm.opt.ExplicitGCInvokesConcurrent != true
  27  * @summary Test return of JNI weak global refs from native calls.
  28  * @modules java.base
  29  * @run main/othervm/native -Xint ReturnJNIWeak
  30  * @run main/othervm/native -Xcomp ReturnJNIWeak
  31  */
  32 
  33 public final class ReturnJNIWeak {
  34 
  35     static {
  36         System.loadLibrary("ReturnJNIWeak");
  37     }
  38 
  39     private static final class TestObject {
  40         public final int value;
  41 
  42         public TestObject(int value) {
  43             this.value = value;
  44         }
  45     }
  46 
  47     private static volatile TestObject testObject = null;
  48 
  49     private static native void registerObject(Object o);
  50     private static native void unregisterObject();
  51     private static native Object getObject();
  52 
  53     // Create the test object and record it both strongly and weakly.
  54     private static void remember(int value) {
  55         TestObject o = new TestObject(value);
  56         registerObject(o);
  57         testObject = o;
  58     }
  59 
  60     // Remove both strong and weak references to the current test object.
  61     private static void forget() {
  62         unregisterObject();
  63         testObject = null;
  64     }
  65 
  66     // Verify the weakly recorded object
  67     private static void checkValue(int value) throws Exception {
  68         Object o = getObject();
  69         if (o == null) {
  70             throw new RuntimeException("Weak reference unexpectedly null");
  71         }
  72         TestObject t = (TestObject)o;
  73         if (t.value != value) {
  74             throw new RuntimeException("Incorrect value");
  75         }
  76     }
  77 
  78     // Verify we can create a weak reference and get it back.
  79     private static void testSanity() throws Exception {
  80         System.out.println("running testSanity");
  81         int value = 5;
  82         try {
  83             remember(value);
  84             checkValue(value);
  85         } finally {
  86             forget();
  87         }
  88     }
  89 
  90     // Verify weak ref value survives across collection if strong ref exists.
  91     private static void testSurvival() throws Exception {
  92         System.out.println("running testSurvival");
  93         int value = 10;
  94         try {
  95             remember(value);
  96             checkValue(value);
  97             System.gc();
  98             // Verify weak ref still has expected value.
  99             checkValue(value);
 100         } finally {
 101             forget();
 102         }
 103     }
 104 
 105     // Verify weak ref cleared if no strong ref exists.
 106     private static void testClear() throws Exception {
 107         System.out.println("running testClear");
 108         int value = 15;
 109         try {
 110           remember(value);
 111           checkValue(value);
 112           // Verify still good.
 113           checkValue(value);
 114           // Drop reference.
 115           testObject = null;
 116           System.gc();
 117           // Verify weak ref cleared as expected.
 118           Object recorded = getObject();
 119           if (recorded != null) {
 120             throw new RuntimeException("expected clear");
 121           }
 122         } finally {
 123           forget();
 124         }
 125     }
 126 
 127     public static void main(String[] args) throws Exception {
 128         testSanity();
 129         testSurvival();
 130         testClear();
 131     }
 132 }