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.
5 #ifndef BASE_SEQUENCE_CHECKER_H_
6 #define BASE_SEQUENCE_CHECKER_H_
8 #include "base/compiler_specific.h"
9 #include "base/logging.h"
10 #include "base/sequence_checker_impl.h"
12 // SequenceChecker is a helper class used to help verify that some methods of a
13 // class are called sequentially (for thread-safety).
15 // Use the macros below instead of the SequenceChecker directly so that the
16 // unused member doesn't result in an extra byte (four when padded) per
17 // instance in production.
19 // This class is much prefered to ThreadChecker for thread-safety checks.
20 // ThreadChecker should only be used for classes that are truly thread-affine
21 // (use thread-local-storage or a third-party API that does).
27 // // It's sometimes useful to detach on construction for objects that are
28 // // constructed in one place and forever after used from another
30 // DETACH_FROM_SEQUENCE(my_sequence_checker_);
34 // // SequenceChecker doesn't automatically check it's destroyed on origin
35 // // sequence for the same reason it's sometimes detached in the
36 // // constructor. It's okay to destroy off sequence if the owner
37 // // otherwise knows usage on the associated sequence is done. If you're
38 // // not detaching in the constructor, you probably want to explicitly
39 // // check in the destructor.
40 // DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_);
43 // DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_);
48 // SEQUENCE_CHECKER(my_sequence_checker_);
52 #define SEQUENCE_CHECKER(name) base::SequenceChecker name
53 #define DCHECK_CALLED_ON_VALID_SEQUENCE(name) \
54 DCHECK((name).CalledOnValidSequence())
55 #define DETACH_FROM_SEQUENCE(name) (name).DetachFromSequence()
56 #else // DCHECK_IS_ON()
57 #define SEQUENCE_CHECKER(name)
58 #define DCHECK_CALLED_ON_VALID_SEQUENCE(name) EAT_STREAM_PARAMETERS
59 #define DETACH_FROM_SEQUENCE(name)
60 #endif // DCHECK_IS_ON()
64 // Do nothing implementation, for use in release mode.
66 // Note: You should almost always use the SequenceChecker class (through the
67 // above macros) to get the right version for your build configuration.
68 class SequenceCheckerDoNothing {
70 SequenceCheckerDoNothing() = default;
71 bool CalledOnValidSequence() const WARN_UNUSED_RESULT { return true; }
72 void DetachFromSequence() {}
75 DISALLOW_COPY_AND_ASSIGN(SequenceCheckerDoNothing);
79 class SequenceChecker : public SequenceCheckerImpl {
82 class SequenceChecker : public SequenceCheckerDoNothing {
84 #endif // DCHECK_IS_ON()
88 #endif // BASE_SEQUENCE_CHECKER_H_