1 /* 2 * Copyright (c) 2017, 2018, Red Hat, Inc. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 /** 25 * @test TestMaybeNullUnsafeAccess 26 * @summary cast before unsafe access moved in dominating null check null path causes crash 27 * @key gc 28 * @requires vm.gc.Shenandoah 29 * @modules java.base/jdk.internal.misc:+open 30 * 31 * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation 32 * TestMaybeNullUnsafeAccess 33 * 34 * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation 35 * -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC 36 * TestMaybeNullUnsafeAccess 37 * 38 */ 39 40 import jdk.internal.misc.Unsafe; 41 42 import java.lang.reflect.Field; 43 44 public class TestMaybeNullUnsafeAccess { 45 46 static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe(); 47 static final long F_OFFSET; 48 49 static class A { 50 int f; 51 } 52 53 static { 54 try { 55 Field fField = A.class.getDeclaredField("f"); 56 F_OFFSET = UNSAFE.objectFieldOffset(fField); 57 } catch (Exception e) { 58 throw new RuntimeException(e); 59 } 60 } 61 62 static A test_helper(Object o) { 63 return (A) o; 64 } 65 66 static int test(Object o) { 67 int f = 0; 68 for (int i = 0; i < 100; i++) { 69 A a = test_helper(o); 70 f = UNSAFE.getInt(a, F_OFFSET); 71 } 72 return f; 73 } 74 75 static public void main(String[] args) { 76 A a = new A(); 77 for (int i = 0; i < 20000; i++) { 78 test_helper(null); 79 test_helper(a); 80 test(a); 81 } 82 } 83 84 }