1 /* 2 * Copyright (c) 2014 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 // Borrowed from Chromium's src/base/threading/thread_checker.h. 12 13 #ifndef WEBRTC_BASE_THREAD_CHECKER_H_ 14 #define WEBRTC_BASE_THREAD_CHECKER_H_ 15 16 // Apart from debug builds, we also enable the thread checker in 17 // builds with DCHECK_ALWAYS_ON so that trybots and waterfall bots 18 // with this define will get the same level of thread checking as 19 // debug bots. 20 // 21 // Note that this does not perfectly match situations where RTC_DCHECK is 22 // enabled. For example a non-official release build may have 23 // DCHECK_ALWAYS_ON undefined (and therefore ThreadChecker would be 24 // disabled) but have RTC_DCHECKs enabled at runtime. 25 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) 26 #define ENABLE_THREAD_CHECKER 1 27 #else 28 #define ENABLE_THREAD_CHECKER 0 29 #endif 30 31 #include "webrtc/base/thread_checker_impl.h" 32 33 namespace rtc { 34 35 // Do nothing implementation, for use in release mode. 36 // 37 // Note: You should almost always use the ThreadChecker class to get the 38 // right version for your build configuration. 39 class ThreadCheckerDoNothing { 40 public: 41 bool CalledOnValidThread() const { 42 return true; 43 } 44 45 void DetachFromThread() {} 46 }; 47 48 // ThreadChecker is a helper class used to help verify that some methods of a 49 // class are called from the same thread. It provides identical functionality to 50 // base::NonThreadSafe, but it is meant to be held as a member variable, rather 51 // than inherited from base::NonThreadSafe. 52 // 53 // While inheriting from base::NonThreadSafe may give a clear indication about 54 // the thread-safety of a class, it may also lead to violations of the style 55 // guide with regard to multiple inheritance. The choice between having a 56 // ThreadChecker member and inheriting from base::NonThreadSafe should be based 57 // on whether: 58 // - Derived classes need to know the thread they belong to, as opposed to 59 // having that functionality fully encapsulated in the base class. 60 // - Derived classes should be able to reassign the base class to another 61 // thread, via DetachFromThread. 62 // 63 // If neither of these are true, then having a ThreadChecker member and calling 64 // CalledOnValidThread is the preferable solution. 65 // 66 // Example: 67 // class MyClass { 68 // public: 69 // void Foo() { 70 // RTC_DCHECK(thread_checker_.CalledOnValidThread()); 71 // ... (do stuff) ... 72 // } 73 // 74 // private: 75 // ThreadChecker thread_checker_; 76 // } 77 // 78 // In Release mode, CalledOnValidThread will always return true. 79 #if ENABLE_THREAD_CHECKER 80 class ThreadChecker : public ThreadCheckerImpl { 81 }; 82 #else 83 class ThreadChecker : public ThreadCheckerDoNothing { 84 }; 85 #endif // ENABLE_THREAD_CHECKER 86 87 #undef ENABLE_THREAD_CHECKER 88 89 } // namespace rtc 90 91 #endif // WEBRTC_BASE_THREAD_CHECKER_H_ 92
