classUnloading/anonymousClass/TestAnonymousClassUnloading.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * @test TestAnonymousClassUnloading
 * @bug 8054402
 * @summary "Tests unloading of anonymous classes."
 * @library /testlibrary /test/lib /
 * @modules java.base/jdk.internal.misc
 *
 * @run main/othervm/bootclasspath -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
 *      -XX:-BackgroundCompilation
 *      compiler.classUnloading.anonymousClass.TestAnonymousClassUnloading
 */

package compiler.classUnloading.anonymousClass;

import jdk.internal.misc.Unsafe;
import sun.hotspot.WhiteBox;

import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLConnection;

public class TestAnonymousClassUnloading {
    private static final WhiteBox WHITE_BOX = WhiteBox.getWhiteBox();
    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
    private static int COMP_LEVEL_SIMPLE = 1;
    private static int COMP_LEVEL_FULL_OPTIMIZATION = 4;

    /**
     * We override hashCode here to be able to access this implementation
     * via an Object reference (we cannot cast to TestAnonymousClassUnloading).
     */
    @Override
    public int hashCode() {
        return 42;
    }

    /**
     * Does some work by using the anonymousClass.
     * @param anonymousClass Class performing some work (will be unloaded)
     */
    static private void doWork(Class<?> anonymousClass) throws InstantiationException, IllegalAccessException {
        // Create a new instance
        Object anon = anonymousClass.newInstance();
        // We would like to call a method of anonymousClass here but we cannot cast 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 IC we call Object::hashCode() here which actually
        // calls anonymousClass::hashCode(). C2 will then implement this call as an IC.
        if (anon.hashCode() != 42) {
            new RuntimeException("Work not done");
        }
    }

    /**
     * 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 Klass* metadata referenced by a compiled IC.
     *
     * The following steps are performed:
     * (1) An anonymous version of TestAnonymousClassUnloading is loaded by a custom class loader
     * (2) The method doWork that calls a method of the anonymous class is compiled. The call
     *     is implemented as an IC referencing Klass* metadata of the anonymous class.
     * (3) Unloading of the anonymous class is enforced. The IC now references dead metadata.
     */
    static public void main(String[] args) throws Exception {
        // (1) Load an anonymous version of this class using the corresponding Unsafe method
        URL classUrl = TestAnonymousClassUnloading.class.getResource(
                TestAnonymousClassUnloading.class.getName().replace('.', '/') + ".class");
        URLConnection connection = classUrl.openConnection();

        int length = connection.getContentLength();
        byte[] classBytes = connection.getInputStream().readAllBytes();
        if (length != -1 && classBytes.length != length) {
            throw new IOException("Expected:" + length + ", actual: " + classBytes.length);
        }

        Class<?> anonymousClass = UNSAFE.defineAnonymousClass(TestAnonymousClassUnloading.class, classBytes, null);

        // (2) Make sure all paths of doWork are profiled and compiled
        for (int i = 0; i < 100000; ++i) {
            doWork(anonymousClass);
        }

        // Make sure doWork is compiled now
        Method doWork = TestAnonymousClassUnloading.class.getDeclaredMethod("doWork", Class.class);
        makeSureIsCompiled(doWork);

        // (3) Throw away reference to anonymousClass to allow unloading
        anonymousClass = null;

        // Force garbage collection to trigger unloading of anonymousClass
        // Dead metadata reference to anonymousClass triggers JDK-8054402
        WHITE_BOX.fullGC();
    }
}