mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-27 06:43:32 +00:00
e3ebda1914
CLOSED TREE
We don't need these macros anymore, for two reasons:
1. We have static analysis to provide the same sort of checks via `MOZ_RAII`
and friends.
2. clang now warns for the "temporary that should have been a declaration" case.
The extra requirements on class construction also show up during debug tests
as performance problems.
This change was automated by using the following sed script:
```
# Remove declarations in classes.
/MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER/d
/MOZ_GUARD_OBJECT_NOTIFIER_INIT/d
# Remove individual macros, carefully.
{
# We don't have to worry about substrings here because the closing
# parenthesis "anchors" the match.
s/MOZ_GUARD_OBJECT_NOTIFIER_PARAM)/)/g;
s/MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)/)/g;
s/MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)/)/g;
s/MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)/)/g;
# Remove the longer identifier first.
s/MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_TO_PARENT//g;
s/MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM//g;
}
# Remove the actual include.
\@# *include "mozilla/GuardObjects.h"@d
```
and running:
```
find . -name \*.cpp -o -name \*.h | grep -v 'GuardObjects.h' |xargs sed -i -f script 2>/dev/null
mach clang-format
```
Differential Revision: https://phabricator.services.mozilla.com/D85168
127 lines
3.2 KiB
C++
127 lines
3.2 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* RAII class for executing arbitrary actions at scope end. */
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#ifndef mozilla_ScopeExit_h
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#define mozilla_ScopeExit_h
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/*
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* See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4189.pdf for a
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* standards-track version of this.
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*
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* Error handling can be complex when various actions need to be performed that
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* need to be undone if an error occurs midway. This can be handled with a
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* collection of boolean state variables and gotos, which can get clunky and
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* error-prone:
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*
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* {
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* if (!a.setup())
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* goto fail;
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* isASetup = true;
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*
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* if (!b.setup())
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* goto fail;
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* isBSetup = true;
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*
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* ...
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* return true;
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*
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* fail:
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* if (isASetup)
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* a.teardown();
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* if (isBSetup)
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* b.teardown();
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* return false;
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* }
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*
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* ScopeExit is a mechanism to simplify this pattern by keeping an RAII guard
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* class that will perform the teardown on destruction, unless released. So the
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* above would become:
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*
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* {
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* if (!a.setup()) {
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* return false;
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* }
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* auto guardA = MakeScopeExit([&] {
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* a.teardown();
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* });
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*
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* if (!b.setup()) {
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* return false;
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* }
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* auto guardB = MakeScopeExit([&] {
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* b.teardown();
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* });
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*
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* ...
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* guardA.release();
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* guardB.release();
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* return true;
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* }
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*
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* This header provides:
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*
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* - |ScopeExit| - a container for a cleanup call, automically called at the
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* end of the scope;
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* - |MakeScopeExit| - a convenience function for constructing a |ScopeExit|
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* with a given cleanup routine, commonly used with a lambda function.
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*
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* Note that the RAII classes defined in this header do _not_ perform any form
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* of reference-counting or garbage-collection. These classes have exactly two
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* behaviors:
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*
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* - if |release()| has not been called, the cleanup is always performed at
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* the end of the scope;
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* - if |release()| has been called, nothing will happen at the end of the
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* scope.
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*/
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#include <utility>
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#include "mozilla/Attributes.h"
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namespace mozilla {
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template <typename ExitFunction>
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class MOZ_STACK_CLASS ScopeExit {
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ExitFunction mExitFunction;
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bool mExecuteOnDestruction;
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public:
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explicit ScopeExit(ExitFunction&& cleanup)
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: mExitFunction(cleanup), mExecuteOnDestruction(true) {}
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ScopeExit(ScopeExit&& rhs)
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: mExitFunction(std::move(rhs.mExitFunction)),
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mExecuteOnDestruction(rhs.mExecuteOnDestruction) {
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rhs.release();
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}
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~ScopeExit() {
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if (mExecuteOnDestruction) {
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mExitFunction();
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}
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}
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void release() { mExecuteOnDestruction = false; }
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private:
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explicit ScopeExit(const ScopeExit&) = delete;
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ScopeExit& operator=(const ScopeExit&) = delete;
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ScopeExit& operator=(ScopeExit&&) = delete;
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};
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template <typename ExitFunction>
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MOZ_MUST_USE ScopeExit<ExitFunction> MakeScopeExit(
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ExitFunction&& exitFunction) {
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return ScopeExit<ExitFunction>(std::move(exitFunction));
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}
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} /* namespace mozilla */
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#endif /* mozilla_ScopeExit_h */
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