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89 lines
2.9 KiB
89 lines
2.9 KiB
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_SEQUENCE_CHECKER_H_
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#define BASE_SEQUENCE_CHECKER_H_
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#include "base/compiler_specific.h"
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#include "base/logging.h"
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#include "base/sequence_checker_impl.h"
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// SequenceChecker is a helper class used to help verify that some methods of a
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// class are called sequentially (for thread-safety).
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//
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// Use the macros below instead of the SequenceChecker directly so that the
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// unused member doesn't result in an extra byte (four when padded) per
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// instance in production.
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//
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// This class is much prefered to ThreadChecker for thread-safety checks.
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// ThreadChecker should only be used for classes that are truly thread-affine
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// (use thread-local-storage or a third-party API that does).
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//
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// Usage:
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// class MyClass {
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// public:
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// MyClass() {
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// // It's sometimes useful to detach on construction for objects that are
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// // constructed in one place and forever after used from another
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// // sequence.
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// DETACH_FROM_SEQUENCE(my_sequence_checker_);
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// }
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//
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// ~MyClass() {
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// // SequenceChecker doesn't automatically check it's destroyed on origin
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// // sequence for the same reason it's sometimes detached in the
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// // constructor. It's okay to destroy off sequence if the owner
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// // otherwise knows usage on the associated sequence is done. If you're
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// // not detaching in the constructor, you probably want to explicitly
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// // check in the destructor.
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// DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_);
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// }
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// void MyMethod() {
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// DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_);
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// ... (do stuff) ...
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// }
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//
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// private:
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// SEQUENCE_CHECKER(my_sequence_checker_);
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// }
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#if DCHECK_IS_ON()
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#define SEQUENCE_CHECKER(name) base::SequenceChecker name
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#define DCHECK_CALLED_ON_VALID_SEQUENCE(name) \
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DCHECK((name).CalledOnValidSequence())
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#define DETACH_FROM_SEQUENCE(name) (name).DetachFromSequence()
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#else // DCHECK_IS_ON()
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#define SEQUENCE_CHECKER(name)
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#define DCHECK_CALLED_ON_VALID_SEQUENCE(name) EAT_STREAM_PARAMETERS
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#define DETACH_FROM_SEQUENCE(name)
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#endif // DCHECK_IS_ON()
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namespace base {
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// Do nothing implementation, for use in release mode.
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//
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// Note: You should almost always use the SequenceChecker class (through the
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// above macros) to get the right version for your build configuration.
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class SequenceCheckerDoNothing {
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public:
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SequenceCheckerDoNothing() = default;
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bool CalledOnValidSequence() const WARN_UNUSED_RESULT { return true; }
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void DetachFromSequence() {}
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private:
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DISALLOW_COPY_AND_ASSIGN(SequenceCheckerDoNothing);
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};
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#if DCHECK_IS_ON()
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class SequenceChecker : public SequenceCheckerImpl {
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};
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#else
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class SequenceChecker : public SequenceCheckerDoNothing {
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};
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#endif // DCHECK_IS_ON()
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} // namespace base
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#endif // BASE_SEQUENCE_CHECKER_H_
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