xref: /aosp_15_r20/system/unwinding/libunwindstack/tests/TestLocal.cpp (revision eb293b8f56ee8303637c5595cfcdeef8039e85c6)

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdint.h>
#include <stdlib.h>

#include "TestUtils.h"

// The loop in this function is only guaranteed to not be optimized away by the compiler
// if optimizations are turned off. This is partially because the compiler doesn't have
// any idea about the function since it is retrieved using dlsym.
//
// In an effort to defend against the compiler:
//  1. The loop iteration variable is volatile.
//  2. A call to this function should be wrapped in TestUtils::DoNotOptimize().
extern "C" int BusyWait() {
  for (size_t i = 0; i < 1000000;) {
    unwindstack::DoNotOptimize(i++);
  }
  return 0;
}

// Do a loop that guarantees the terminating leaf frame will be in
// the this library and not a function from a different library.
extern "C" void WaitForever() {
  bool run = true;
  while (run) {
    unwindstack::DoNotOptimize(run = true);
  }
}