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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * particular file as subject to the "Classpath" exception as provided

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 * 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).

 *

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package jdk.jfr.jvm;

import java.time.Duration;

import java.util.List;

import jdk.jfr.consumer.RecordedClass;

import jdk.jfr.consumer.RecordedClassLoader;

import jdk.jfr.consumer.RecordedEvent;

import jdk.jfr.internal.JVM;

import jdk.jfr.Recording;

import jdk.test.lib.Asserts;

import jdk.test.lib.jfr.EventNames;

import jdk.test.lib.jfr.Events;

import jdk.test.lib.jfr.TestClassLoader;

/**

 * @test

 * @bug 8231081

 * @key jfr

 * @requires vm.hasJFR

 * @modules jdk.jfr/jdk.jfr.internal

 * @library /test/lib /test/jdk

 * @run main/othervm -Xlog:class+unload -Xlog:gc -Xmx16m jdk.jfr.jvm.TestClearStaleConstants

 */

/**

 * System.gc() will trigger class unloading if -XX:+ExplicitGCInvokesConcurrent is NOT set.

 * If this flag is set G1 will never unload classes on System.gc() and

 * As far as the "jfr" key guarantees no VM flags are set from the outside

 * it should be enough with System.gc().

 */

public final class TestClearStaleConstants {

    static class MyClass {

    }

    private final static String TEST_CLASS_NAME = "jdk.jfr.jvm.TestClearStaleConstants$MyClass";

    private final static String EVENT_NAME = EventNames.ClassDefine;

    // to prevent the compiler to optimize away all unread writes

    public static TestClassLoader firstClassLoader;

    public static TestClassLoader secondClassLoader;

    public static void main(String... args) throws Exception {

        firstClassLoader = new TestClassLoader();

        // define a  class using a class loader under a recording

        Class<?> clz = recordClassDefinition(firstClassLoader);

        JVM jvm = JVM.getJVM();

        // we will now tag the defined and loaded clz as being in use (no recordings are running here)

        jvm.getClassIdNonIntrinsic(clz);

        // null out for unload to occur

        firstClassLoader = null;

        clz = null;

        // provoke unload

        System.gc();

        // try to define another class _with the same name_ using a different class loader

        secondClassLoader = new TestClassLoader();

        // this will throw a NPE for 8231081 because it will reuse the same class name

        // that symbol was  marked as already serialized by the unload, but since no recordings were running

        // it was not written to any chunk. This creates a reference to a non-existing symbol, leading to an NPE (no symbol at the expected location).

        recordClassDefinition(secondClassLoader);

    }

    private static Class<?> recordClassDefinition(TestClassLoader classLoader) throws Exception  {

        try (Recording recording = new Recording())  {

            recording.enable(EVENT_NAME);

            recording.start();

            Class<?> clz = classLoader.loadClass(TEST_CLASS_NAME);

            recording.stop();

            assertClassDefineEvent(recording);

            return clz;

        }

    }

    private static void assertClassDefineEvent(Recording recording) throws Exception {

        boolean isAnyFound = false;

        for (RecordedEvent event : Events.fromRecording(recording)) {

            System.out.println(event);

            RecordedClass definedClass = event.getValue("definedClass");

            if (TEST_CLASS_NAME.equals(definedClass.getName())) {

                RecordedClassLoader definingClassLoader = definedClass.getClassLoader();

                String definingName = definingClassLoader.getType().getName();

                String testName = TestClassLoader.class.getName();

                String errorMsg = "Expected " + testName + ", got " + definingName;

                Asserts.assertEquals(testName, definingName, errorMsg);

                Asserts.assertFalse(isAnyFound, "Found more than 1 event");

                isAnyFound = true;

            }

        }

        Asserts.assertTrue(isAnyFound, "No events found");

    }

}