// Copyright (c) 2012 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef BASE_SEQUENCE_CHECKER_H_ #define BASE_SEQUENCE_CHECKER_H_ #include "base/base_export.h" #include "base/dcheck_is_on.h" #include "base/sequence_checker_impl.h" // SequenceChecker is a helper class used to help verify that some methods of a // class are called sequentially (for thread-safety). It supports thread safety // annotations (see base/thread_annotations.h). // // Use the macros below instead of the SequenceChecker directly so that the // unused member doesn't result in an extra byte (four when padded) per // instance in production. // // This class is much prefered to ThreadChecker for thread-safety checks. // ThreadChecker should only be used for classes that are truly thread-affine // (use thread-local-storage or a third-party API that does). // // Debugging: // If SequenceChecker::EnableStackLogging() is called beforehand, then when // SequenceChecker fails, in addition to crashing with a stack trace of where // the violation occurred, it will also dump a stack trace of where the // checker was bound to a sequence. // // Usage: // class MyClass { // public: // MyClass() { // // Detaching on construction is necessary for objects that are // // constructed on one sequence and forever after used from another // // sequence. // DETACH_FROM_SEQUENCE(my_sequence_checker_); // } // // ~MyClass() { // // SequenceChecker doesn't automatically check it's destroyed on origin // // sequence for the same reason it's sometimes detached in the // // constructor. It's okay to destroy off sequence if the owner // // otherwise knows usage on the associated sequence is done. If you're // // not detaching in the constructor, you probably want to explicitly // // check in the destructor. // DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_); // } // void MyMethod() { // DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_); // ... (do stuff) ... // MyOtherMethod(); // } // // void MyOtherMethod() // VALID_CONTEXT_REQUIRED(my_sequence_checker_) { // foo_ = 42; // } // // private: // // GUARDED_BY_CONTEXT() enforces that this member is only // // accessed from a scope that invokes DCHECK_CALLED_ON_VALID_SEQUENCE() // // or from a function annotated with VALID_CONTEXT_REQUIRED(). A // // DCHECK build will not compile if the member is accessed and these // // conditions are not met. // int foo_ GUARDED_BY_CONTEXT(my_sequence_checker_); // // SEQUENCE_CHECKER(my_sequence_checker_); // } #define SEQUENCE_CHECKER_INTERNAL_CONCAT2(a, b) a##b #define SEQUENCE_CHECKER_INTERNAL_CONCAT(a, b) \ SEQUENCE_CHECKER_INTERNAL_CONCAT2(a, b) #define SEQUENCE_CHECKER_INTERNAL_UID(prefix) \ SEQUENCE_CHECKER_INTERNAL_CONCAT(prefix, __LINE__) #if DCHECK_IS_ON() #define SEQUENCE_CHECKER(name) base::SequenceChecker name #define DCHECK_CALLED_ON_VALID_SEQUENCE(name, ...) \ base::ScopedValidateSequenceChecker SEQUENCE_CHECKER_INTERNAL_UID( \ scoped_validate_sequence_checker_)(name, ##__VA_ARGS__) #define DETACH_FROM_SEQUENCE(name) (name).DetachFromSequence() #else // DCHECK_IS_ON() // A no-op expansion that can be followed by a semicolon at class level. #define SEQUENCE_CHECKER(name) static_assert(true, "") #define DCHECK_CALLED_ON_VALID_SEQUENCE(name, ...) EAT_CHECK_STREAM_PARAMS() #define DETACH_FROM_SEQUENCE(name) #endif // DCHECK_IS_ON() namespace base { // Do nothing implementation, for use in release mode. // // Note: You should almost always use the SequenceChecker class (through the // above macros) to get the right version for your build configuration. // Note: This is marked with "context" capability in order to support // thread_annotations.h. class THREAD_ANNOTATION_ATTRIBUTE__(capability("context")) SequenceCheckerDoNothing { public: static void EnableStackLogging() {} SequenceCheckerDoNothing() = default; // Moving between matching sequences is allowed to help classes with // SequenceCheckers that want a default move-construct/assign. SequenceCheckerDoNothing(SequenceCheckerDoNothing&& other) = default; SequenceCheckerDoNothing& operator=(SequenceCheckerDoNothing&& other) = default; SequenceCheckerDoNothing(const SequenceCheckerDoNothing&) = delete; SequenceCheckerDoNothing& operator=(const SequenceCheckerDoNothing&) = delete; [[nodiscard]] bool CalledOnValidSequence(void* = nullptr) const { return true; } void DetachFromSequence() {} }; #if DCHECK_IS_ON() using SequenceChecker = SequenceCheckerImpl; #else using SequenceChecker = SequenceCheckerDoNothing; #endif // DCHECK_IS_ON() #if DCHECK_IS_ON() class BASE_EXPORT SCOPED_LOCKABLE ScopedValidateSequenceChecker { public: explicit ScopedValidateSequenceChecker(const SequenceChecker& checker) EXCLUSIVE_LOCK_FUNCTION(checker); ~ScopedValidateSequenceChecker() UNLOCK_FUNCTION(); }; #endif } // namespace base #endif // BASE_SEQUENCE_CHECKER_H_