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 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

 * 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 * questions.

 */

import sun.hotspot.WhiteBox;

import java.lang.reflect.Method;

import java.net.URL;

import java.net.URLClassLoader;

/*

 * @test MethodUnloadingTest

 * @bug 8029443

 * @summary "Tests the unloading of methods to to class unloading"

 * @build TestMethodUnloading

 * @build WorkerClass

 * @run main ClassFileInstaller sun.hotspot.WhiteBox

 *                              sun.hotspot.WhiteBox$WhiteBoxPermission

 * @run main/othervm -Xbootclasspath/a:. -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:-BackgroundCompilation -XX:-UseCompressedOops -XX:CompileOnly=TestMethodUnloading::doWork TestMethodUnloading

 */

public class TestMethodUnloading {

    private static final String workerClassName = "WorkerClass";

    private static int work = -1;

    private static final WhiteBox WHITE_BOX = WhiteBox.getWhiteBox();

    private static int COMP_LEVEL_SIMPLE = 1;

    private static int COMP_LEVEL_FULL_OPTIMIZATION = 4;

    /**

     * Does some work by either using the workerClass or locally producing values.

     * @param workerClass Class performing some work (will be unloaded)

     * @param useWorker If true the workerClass is used

     */

    static private void doWork(Class<?> workerClass, boolean useWorker) throws InstantiationException, IllegalAccessException {

        if (useWorker) {

            // Create a new instance

            Object worker = workerClass.newInstance();

            // We would like to call a method of WorkerClass here but we cannot cast to WorkerClass

            // because the class was loaded by a different class loader. One solution would be to use

            // reflection but since we want C2 to implement the call as an optimized IC we call

            // Object::hashCode() here which actually calls WorkerClass::hashCode().

            // C2 will then implement this call as an optimized IC that points to a to-interpreter stub

            // referencing the Method* for WorkerClass::hashCode().

            work = worker.hashCode();

            if (work != 42) {

                new RuntimeException("Work not done");

            }

        } else {

            // Do some important work here

            work = 1;

        }

    }

    /**

     * Makes sure that method is compiled by forcing compilation if not yet compiled.

     * @param m Method to be checked

     */

    static private void makeSureIsCompiled(Method m) {

        // Make sure background compilation is disabled

        if (WHITE_BOX.getBooleanVMFlag("BackgroundCompilation")) {

            throw new RuntimeException("Background compilation enabled");

        }

        // Check if already compiled

        if (!WHITE_BOX.isMethodCompiled(m)) {

            // If not, try to compile it with C2

            if(!WHITE_BOX.enqueueMethodForCompilation(m, COMP_LEVEL_FULL_OPTIMIZATION)) {

                // C2 compiler not available, try to compile with C1

                WHITE_BOX.enqueueMethodForCompilation(m, COMP_LEVEL_SIMPLE);

            }

            // Because background compilation is disabled, method should now be compiled

            if(!WHITE_BOX.isMethodCompiled(m)) {

                throw new RuntimeException(m + " not compiled");

            }

        }

    }

    /**

     * This test creates stale Method* metadata in a to-interpreter stub of an optimized IC.

     *

     * The following steps are performed:

     * (1) A workerClass is loaded by a custom class loader

     * (2) The method doWork that calls a method of the workerClass is compiled. The call

     *     is implemented as an optimized IC calling a to-interpreted stub. The to-interpreter

     *     stub contains a Method* to a workerClass method.

     * (3) Unloading of the workerClass is enforced. The to-interpreter stub now contains a dead Method*.

     * (4) Depending on the implementation of the IC, the compiled version of doWork should still be

     *     valid. We call it again without using the workerClass.

     */

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

        // (1) Create a custom class loader with no parent class loader

        URL url = TestMethodUnloading.class.getProtectionDomain().getCodeSource().getLocation();

        URLClassLoader loader = new URLClassLoader(new URL[] {url}, null);

        // Load worker class with custom class loader

        Class<?> workerClass = Class.forName(workerClassName, true, loader);

        // (2) Make sure all paths of doWork are profiled and compiled

        for (int i = 0; i < 100000; ++i) {

            doWork(workerClass, true);

            doWork(workerClass, false);

        }

        // Make sure doWork is compiled now

        Method doWork = TestMethodUnloading.class.getDeclaredMethod("doWork", Class.class, boolean.class);

        makeSureIsCompiled(doWork);

        // (3) Throw away class loader and reference to workerClass to allow unloading

        loader.close();

        loader = null;

        workerClass = null;

        // Force garbage collection to trigger unloading of workerClass

        // Dead reference to WorkerClass::hashCode triggers JDK-8029443

        WHITE_BOX.fullGC();

        // (4) Depending on the implementation of the IC, the compiled version of doWork

        // may still be valid here. Execute it without a workerClass.

        doWork(null, false);

        if (work != 1) {

            throw new RuntimeException("Work not done");

        }

        doWork(Object.class, false);

    }

}