98 lines
2.9 KiB
Java
98 lines
2.9 KiB
Java
/*
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* Copyright (c) 2017, Red Hat, Inc. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/**
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* @test
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* @bug 8176506
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* @summary cast before unsafe access moved in dominating null check null path causes crash
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* @modules java.base/jdk.internal.misc:+open
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*
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* @run main/othervm -Xbatch -XX:-UseOnStackReplacement TestMaybeNullUnsafeAccess
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*
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*/
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import jdk.internal.misc.Unsafe;
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import java.lang.reflect.Field;
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public class TestMaybeNullUnsafeAccess {
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static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe();
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static final long F_OFFSET;
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static class A {
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int f;
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A(int f) {
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this.f = f;
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}
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}
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static {
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try {
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Field fField = A.class.getDeclaredField("f");
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F_OFFSET = UNSAFE.objectFieldOffset(fField);
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} catch (Exception e) {
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throw new RuntimeException(e);
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}
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}
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static A test_helper(Object o) {
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// this includes a check for null with both branches taken
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return (A)o;
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}
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// Loop is unswitched because of the test for null from the
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// checkcast above, unsafe access is copied in each branch, the
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// compiler sees a memory access to a null object
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static int test1(Object o, long offset) {
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int f = 0;
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for (int i = 0; i < 100; i++) {
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A a = test_helper(o);
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f = UNSAFE.getInt(a, offset);
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}
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return f;
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}
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// Same as above except because we know the offset of the access
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// is small, we can deduce object a cannot be null
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static int test2(Object o) {
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int f = 0;
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for (int i = 0; i < 100; i++) {
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A a = test_helper(o);
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f = UNSAFE.getInt(a, F_OFFSET);
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}
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return f;
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}
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static public void main(String[] args) {
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A a = new A(0x42);
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for (int i = 0; i < 20000; i++) {
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test_helper(null);
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test_helper(a);
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test1(a, F_OFFSET);
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test2(a);
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}
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}
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}
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