1 /*
2  * Copyright (C) 2018 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 import java.lang.reflect.InvocationHandler;
18 import java.lang.reflect.Method;
19 import java.lang.reflect.Proxy;
20 import java.util.ArrayList;
21 
22 class OOMEHelper {
23     int nullField;
24 }
25 
26 /**
27  * Test that null field access under an OOME situation works.
28  *
29  * The test relies on compile-time verification. This class is compile-time verifiable, so when
30  * loaded at runtime will not transitively load referenced types eagerly. In that case, our code
31  * to give descriptive NullPointerExceptions for the field access to the null "instance" of
32  * OOMEHelper in nullAccess() will be the first attempting to load the class, and, under the
33  * induced low-memory situation, will throw itself an OutOfMemoryError.
34  */
35 public class OOMEOnNullAccess {
36 
37     static ArrayList<Object> storage = new ArrayList<>(100000);
38 
main(String[] args)39     public static void main(String[] args) {
40         // Stop the JIT to be sure nothing is running that could be resolving classes or causing
41         // verification.
42         Main.stopJit();
43         Main.waitForCompilation();
44 
45         int l = 1024 * 1024;
46         while (l > 8) {
47           try {
48             storage.add(new byte[l]);
49           } catch (OutOfMemoryError e) {
50             l = l/2;
51           }
52         }
53 
54         try {
55             nullAccess(null);
56             storage.clear();
57             throw new RuntimeException("Did not receive exception!");
58         } catch (OutOfMemoryError oome) {
59             storage.clear();
60             System.err.println("Received OOME");
61         } finally {
62             // Even if it's an unexpected error, clear so that we can print things later.
63             storage.clear();
64         }
65 
66         Main.startJit();
67     }
68 
nullAccess(OOMEHelper nullInstance)69     public static int nullAccess(OOMEHelper nullInstance) {
70         // Under AOT, this access is the first one to actually load the OOMEHelper class, so
71         // we can pretty print the name and such.
72         return nullInstance.nullField;
73     }
74 }
75