DefaultValue.java

/*
 * Copyright (c) 2013, 2015, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.lang.Class;
import java.lang.String;
import java.lang.System;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CyclicBarrier;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import sun.misc.Unsafe;
import sun.misc.Contended;

/*
 * @test
 * @bug     8014509
 * @summary \@Contended: explicit default value behaves differently from the implicit value
 *
 * @modules java.base/sun.misc
 * @run main/othervm -XX:-RestrictContended DefaultValue
 */
public class DefaultValue {

    private static final Unsafe U;
    private static int ADDRESS_SIZE;
    private static int HEADER_SIZE;

    static {
        // steal Unsafe
        try {
            Field unsafe = Unsafe.class.getDeclaredField("theUnsafe");
            unsafe.setAccessible(true);
            U = (Unsafe) unsafe.get(null);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new IllegalStateException(e);
        }

        // When running with CompressedOops on 64-bit platform, the address size
        // reported by Unsafe is still 8, while the real reference fields are 4 bytes long.
        // Try to guess the reference field size with this naive trick.
        try {
            long off1 = U.objectFieldOffset(CompressedOopsClass.class.getField("obj1"));
            long off2 = U.objectFieldOffset(CompressedOopsClass.class.getField("obj2"));
            ADDRESS_SIZE = (int) Math.abs(off2 - off1);
            HEADER_SIZE = (int) Math.min(off1, off2);
        } catch (NoSuchFieldException e) {
            ADDRESS_SIZE = -1;
        }
    }

    static class CompressedOopsClass {
        public Object obj1;
        public Object obj2;
    }

    public static boolean arePaddedPairwise(Class klass, String field1, String field2) throws Exception {
        Field f1 = klass.getField(field1);
        Field f2 = klass.getField(field2);

        int diff = offset(f1) - offset(f2);
        if (diff < 0) {
            // f1 is first
            return (offset(f2) - (offset(f1) + getSize(f1))) > 64;
        } else {
            // f2 is first
            return (offset(f1) - (offset(f2) + getSize(f2))) > 64;
        }
    }

    public static boolean sameLayout(Class klass1, Class klass2) throws Exception {
        for (Field f1 : klass1.getDeclaredFields()) {
            Field f2 = klass2.getDeclaredField(f1.getName());
            if (offset(f1) != offset(f2)) {
                return false;
            }
        }

        for (Field f2 : klass1.getDeclaredFields()) {
            Field f1 = klass2.getDeclaredField(f2.getName());
            if (offset(f1) != offset(f2)) {
                return false;
            }
        }

        return true;
    }

    public static boolean isStatic(Field field) {
        return Modifier.isStatic(field.getModifiers());
    }

    public static int offset(Field field) {
        if (isStatic(field)) {
            return (int) U.staticFieldOffset(field);
        } else {
            return (int) U.objectFieldOffset(field);
        }
    }

    public static int getSize(Field field) {
        Class type = field.getType();
        if (type == byte.class)    { return 1; }
        if (type == boolean.class) { return 1; }
        if (type == short.class)   { return 2; }
        if (type == char.class)    { return 2; }
        if (type == int.class)     { return 4; }
        if (type == float.class)   { return 4; }
        if (type == long.class)    { return 8; }
        if (type == double.class)  { return 8; }
        return ADDRESS_SIZE;
    }

    public static void main(String[] args) throws Exception {
        boolean endResult = true;

        if (!arePaddedPairwise(R1.class, "int1", "int2")) {
            System.err.println("R1 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(R2.class, "int1", "int2")) {
            System.err.println("R2 failed");
            endResult &= false;
        }

        if (!arePaddedPairwise(R3.class, "int1", "int2")) {
            System.err.println("R3 failed");
            endResult &= false;
        }

        System.out.println(endResult ? "Test PASSES" : "Test FAILS");
        if (!endResult) {
           throw new Error("Test failed");
        }
    }

    public static class R1 {
        @Contended
        public int int1;
        @Contended
        public int int2;
    }

    public static class R2 {
        @Contended("")
        public int int1;
        @Contended("")
        public int int2;
    }

    public static class R3 {
        @Contended()
        public int int1;
        @Contended()
        public int int2;
    }

}