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 #include <stdint.h>
18 #include <stdlib.h>
19
20 #include "TestUtils.h"
21
22 // The loop in this function is only guaranteed to not be optimized away by the compiler
23 // if optimizations are turned off. This is partially because the compiler doesn't have
24 // any idea about the function since it is retrieved using dlsym.
25 //
26 // In an effort to defend against the compiler:
27 // 1. The loop iteration variable is volatile.
28 // 2. A call to this function should be wrapped in TestUtils::DoNotOptimize().
BusyWait()29 extern "C" int BusyWait() {
30 for (size_t i = 0; i < 1000000;) {
31 unwindstack::DoNotOptimize(i++);
32 }
33 return 0;
34 }
35
36 // Do a loop that guarantees the terminating leaf frame will be in
37 // the this library and not a function from a different library.
WaitForever()38 extern "C" void WaitForever() {
39 bool run = true;
40 while (run) {
41 unwindstack::DoNotOptimize(run = true);
42 }
43 }
44