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 TestMaybeNullUnsafeAccess 32 * 33 */ 34 35 import jdk.internal.misc.Unsafe; 36 37 import java.lang.reflect.Field; 38 39 public class TestMaybeNullUnsafeAccess { 40 41 static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe(); 42 static final long F_OFFSET; 43 44 static class A { 45 int f; 46 } 47 48 static { 49 try { 50 Field fField = A.class.getDeclaredField("f"); 51 F_OFFSET = UNSAFE.objectFieldOffset(fField); 52 } catch (Exception e) { 53 throw new RuntimeException(e); 54 } 55 } 56 57 static A test_helper(Object o) { 58 return (A) o; 59 } 60 61 static int test(Object o) { 62 int f = 0; 63 for (int i = 0; i < 100; i++) { 64 A a = test_helper(o); 65 f = UNSAFE.getInt(a, F_OFFSET); 66 } 67 return f; 68 } 69 70 static public void main(String[] args) { 71 A a = new A(); 72 for (int i = 0; i < 20000; i++) { 73 test_helper(null); 74 test_helper(a); 75 test(a); 76 } 77 } 78 79 }