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

 *

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 * 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.

 *

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 */

/*

 * @test

 * @bug 8161720

 * @modules java.base/jdk.internal.misc

 * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -Xbatch -XX:-TieredCompilation UnsafeSmallOffsetBooleanAccessTest

 * @run main/othervm -Xbatch UnsafeSmallOffsetBooleanAccessTest

 */

import java.util.Random;

import jdk.internal.misc.Unsafe;

public class UnsafeSmallOffsetBooleanAccessTest {

    static final Unsafe UNSAFE = Unsafe.getUnsafe();

    static final long F_OFFSET;

    static final Random random = new Random();

    static {

        try {

            F_OFFSET = UNSAFE.objectFieldOffset(T.class.getDeclaredField("f"));

            System.out.println("The offset is: " + F_OFFSET);

        } catch (Exception e) {

            throw new Error(e);

        }

    }

    static class T {

        boolean f;

    }

    // Always return false in a way that is not obvious to the compiler.

    public static boolean myRandom() {

        if (random.nextInt(101) > 134) {

            return true;

        } else {

            return false;

        }

    }

    public static boolean test(T t) {

        boolean result = false;

        for (int i = 0; i < 20000; i++) {

            boolean random = myRandom();

            // If myRandom() returns false, access t.f.

            //

            // If myRandom() returns true, access virtual address

            // F_OFFSET. That address is most likely not mapped,

            // therefore the access will most likely cause a

            // crash. We're not concerned about that, though, because

            // myRandom() always returns false. However, the C2

            // compiler avoids normalization of the value returned by

            // getBoolean in this case.

            result = UNSAFE.getBoolean(myRandom() ? null : t, F_OFFSET);

        }

        return result;

    }

    public static void main(String[] args) {

        T t = new T();

        UNSAFE.putBoolean(t, F_OFFSET, true);

        System.out.println("The result for t is: " + test(t));

    }

}