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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #ifndef BASE_THREADING_THREAD_CHECKER_H_ | |
| 6 #define BASE_THREADING_THREAD_CHECKER_H_ | |
| 7 | |
| 8 // Apart from debug builds, we also enable the thread checker in | |
| 9 // builds with DCHECK_ALWAYS_ON so that trybots and waterfall bots | |
| 10 // with this define will get the same level of thread checking as | |
| 11 // debug bots. | |
| 12 // | |
| 13 // Note that this does not perfectly match situations where DCHECK is | |
| 14 // enabled. For example a non-official release build may have | |
| 15 // DCHECK_ALWAYS_ON undefined (and therefore ThreadChecker would be | |
| 16 // disabled) but have DCHECKs enabled at runtime. | |
| 17 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) | |
| 18 #define ENABLE_THREAD_CHECKER 1 | |
| 19 #else | |
| 20 #define ENABLE_THREAD_CHECKER 0 | |
| 21 #endif | |
| 22 | |
| 23 #include "base/threading/thread_checker_impl.h" | |
| 24 | |
| 25 namespace base { | |
| 26 | |
| 27 // Do nothing implementation, for use in release mode. | |
| 28 // | |
| 29 // Note: You should almost always use the ThreadChecker class to get the | |
| 30 // right version for your build configuration. | |
| 31 class ThreadCheckerDoNothing { | |
| 32 public: | |
| 33 bool CalledOnValidThread() const WARN_UNUSED_RESULT { | |
| 34 return true; | |
| 35 } | |
| 36 | |
| 37 void DetachFromThread() {} | |
| 38 }; | |
| 39 | |
| 40 // ThreadChecker is a helper class used to help verify that some methods of a | |
| 41 // class are called from the same thread. It provides identical functionality to | |
| 42 // base::NonThreadSafe, but it is meant to be held as a member variable, rather | |
| 43 // than inherited from base::NonThreadSafe. | |
| 44 // | |
| 45 // While inheriting from base::NonThreadSafe may give a clear indication about | |
| 46 // the thread-safety of a class, it may also lead to violations of the style | |
| 47 // guide with regard to multiple inheritance. The choice between having a | |
| 48 // ThreadChecker member and inheriting from base::NonThreadSafe should be based | |
| 49 // on whether: | |
| 50 // - Derived classes need to know the thread they belong to, as opposed to | |
| 51 // having that functionality fully encapsulated in the base class. | |
| 52 // - Derived classes should be able to reassign the base class to another | |
| 53 // thread, via DetachFromThread. | |
| 54 // | |
| 55 // If neither of these are true, then having a ThreadChecker member and calling | |
| 56 // CalledOnValidThread is the preferable solution. | |
| 57 // | |
| 58 // Example: | |
| 59 // class MyClass { | |
| 60 // public: | |
| 61 // void Foo() { | |
| 62 // DCHECK(thread_checker_.CalledOnValidThread()); | |
| 63 // ... (do stuff) ... | |
| 64 // } | |
| 65 // | |
| 66 // private: | |
| 67 // ThreadChecker thread_checker_; | |
| 68 // } | |
| 69 // | |
| 70 // In Release mode, CalledOnValidThread will always return true. | |
| 71 #if ENABLE_THREAD_CHECKER | |
| 72 class ThreadChecker : public ThreadCheckerImpl { | |
| 73 }; | |
| 74 #else | |
| 75 class ThreadChecker : public ThreadCheckerDoNothing { | |
| 76 }; | |
| 77 #endif // ENABLE_THREAD_CHECKER | |
| 78 | |
| 79 #undef ENABLE_THREAD_CHECKER | |
| 80 | |
| 81 } // namespace base | |
| 82 | |
| 83 #endif // BASE_THREADING_THREAD_CHECKER_H_ | |
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