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_NON_THREAD_SAFE_H_ 6 #define BASE_THREADING_NON_THREAD_SAFE_H_ 7 8 // Classes deriving from NonThreadSafe may need to suppress MSVC warning 4275: 9 // non dll-interface class 'Bar' used as base for dll-interface class 'Foo'. 10 // There is a specific macro to do it: NON_EXPORTED_BASE(), defined in 11 // compiler_specific.h 12 #include "base/compiler_specific.h" 13 14 // See comment at top of thread_checker.h 15 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) 16 #define ENABLE_NON_THREAD_SAFE 1 17 #else 18 #define ENABLE_NON_THREAD_SAFE 0 19 #endif 20 21 #include "base/threading/non_thread_safe_impl.h" 22 23 namespace base { 24 25 // Do nothing implementation of NonThreadSafe, for release mode. 26 // 27 // Note: You should almost always use the NonThreadSafe class to get 28 // the right version of the class for your build configuration. 29 class NonThreadSafeDoNothing { 30 public: CalledOnValidThread()31 bool CalledOnValidThread() const { 32 return true; 33 } 34 35 protected: ~NonThreadSafeDoNothing()36 ~NonThreadSafeDoNothing() {} DetachFromThread()37 void DetachFromThread() {} 38 }; 39 40 // NonThreadSafe is a helper class used to help verify that methods of a 41 // class are called from the same thread. One can inherit from this class 42 // and use CalledOnValidThread() to verify. 43 // 44 // This is intended to be used with classes that appear to be thread safe, but 45 // aren't. For example, a service or a singleton like the preferences system. 46 // 47 // Example: 48 // class MyClass : public base::NonThreadSafe { 49 // public: 50 // void Foo() { 51 // DCHECK(CalledOnValidThread()); 52 // ... (do stuff) ... 53 // } 54 // } 55 // 56 // Note that base::ThreadChecker offers identical functionality to 57 // NonThreadSafe, but does not require inheritance. In general, it is preferable 58 // to have a base::ThreadChecker as a member, rather than inherit from 59 // NonThreadSafe. For more details about when to choose one over the other, see 60 // the documentation for base::ThreadChecker. 61 #if ENABLE_NON_THREAD_SAFE 62 typedef NonThreadSafeImpl NonThreadSafe; 63 #else 64 typedef NonThreadSafeDoNothing NonThreadSafe; 65 #endif // ENABLE_NON_THREAD_SAFE 66 67 #undef ENABLE_NON_THREAD_SAFE 68 69 } // namespace base 70 71 #endif // BASE_THREADING_NON_THREAD_SAFE_H_ 72