diff options
Diffstat (limited to 'src/corelib/kernel/qapplicationstatic.h')
-rw-r--r-- | src/corelib/kernel/qapplicationstatic.h | 75 |
1 files changed, 22 insertions, 53 deletions
diff --git a/src/corelib/kernel/qapplicationstatic.h b/src/corelib/kernel/qapplicationstatic.h index 93a5062776..bf5e79b8bf 100644 --- a/src/corelib/kernel/qapplicationstatic.h +++ b/src/corelib/kernel/qapplicationstatic.h @@ -1,42 +1,6 @@ -/**************************************************************************** -** -** Copyright (C) 2021 The Qt Company Ltd. -** Copyright (C) 2021 Intel Corporation. -** Contact: https://www.qt.io/licensing/ -** -** This file is part of the QtCore module of the Qt Toolkit. -** -** $QT_BEGIN_LICENSE:LGPL$ -** Commercial License Usage -** Licensees holding valid commercial Qt licenses may use this file in -** accordance with the commercial license agreement provided with the -** Software or, alternatively, in accordance with the terms contained in -** a written agreement between you and The Qt Company. For licensing terms -** and conditions see https://www.qt.io/terms-conditions. For further -** information use the contact form at https://www.qt.io/contact-us. -** -** GNU Lesser General Public License Usage -** Alternatively, this file may be used under the terms of the GNU Lesser -** General Public License version 3 as published by the Free Software -** Foundation and appearing in the file LICENSE.LGPL3 included in the -** packaging of this file. Please review the following information to -** ensure the GNU Lesser General Public License version 3 requirements -** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. -** -** GNU General Public License Usage -** Alternatively, this file may be used under the terms of the GNU -** General Public License version 2.0 or (at your option) the GNU General -** Public license version 3 or any later version approved by the KDE Free -** Qt Foundation. The licenses are as published by the Free Software -** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 -** included in the packaging of this file. Please review the following -** information to ensure the GNU General Public License requirements will -** be met: https://www.gnu.org/licenses/gpl-2.0.html and -** https://www.gnu.org/licenses/gpl-3.0.html. -** -** $QT_END_LICENSE$ -** -****************************************************************************/ +// Copyright (C) 2021 The Qt Company Ltd. +// Copyright (C) 2021 Intel Corporation. +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only #ifndef QAPPLICATIONSTATIC_H #define QAPPLICATIONSTATIC_H @@ -45,6 +9,8 @@ #include <QtCore/qcoreapplication.h> #include <QtCore/qglobalstatic.h> +#include <new> + QT_BEGIN_NAMESPACE namespace QtGlobalStatic { @@ -53,9 +19,9 @@ template <typename QAS> struct ApplicationHolder using Type = typename QAS::QAS_Type; using PlainType = std::remove_cv_t<Type>; - static inline std::aligned_union_t<1, PlainType> storage; - static inline QBasicAtomicInteger<qint8> guard = { QtGlobalStatic::Uninitialized }; - static inline QBasicMutex mutex {}; + Q_CONSTINIT static inline struct { alignas(Type) unsigned char data[sizeof(Type)]; } storage = {}; + Q_CONSTINIT static inline QBasicAtomicInteger<qint8> guard = { QtGlobalStatic::Uninitialized }; + Q_CONSTINIT static inline QBasicMutex mutex {}; static constexpr bool MutexLockIsNoexcept = noexcept(mutex.lock()); static constexpr bool ConstructionIsNoexcept = noexcept(QAS::innerFunction(nullptr)); @@ -64,7 +30,8 @@ template <typename QAS> struct ApplicationHolder Q_DISABLE_COPY_MOVE(ApplicationHolder) ~ApplicationHolder() { - if (guard.loadRelaxed() == QtGlobalStatic::Initialized) { + if (guard.loadAcquire() == QtGlobalStatic::Initialized) { + // No mutex! Up to external code to ensure no race happens. guard.storeRelease(QtGlobalStatic::Destroyed); realPointer()->~PlainType(); } @@ -72,30 +39,32 @@ template <typename QAS> struct ApplicationHolder static PlainType *realPointer() { - return reinterpret_cast<PlainType *>(&storage); + return std::launder(reinterpret_cast<PlainType *>(&storage)); } // called from QGlobalStatic::instance() PlainType *pointer() noexcept(MutexLockIsNoexcept && ConstructionIsNoexcept) { - if (guard.loadRelaxed() == QtGlobalStatic::Initialized) + if (guard.loadAcquire() == QtGlobalStatic::Initialized) return realPointer(); QMutexLocker locker(&mutex); if (guard.loadRelaxed() == QtGlobalStatic::Uninitialized) { - QAS::innerFunction(realPointer()); - QObject::connect(QCoreApplication::instance(), &QObject::destroyed, reset); - guard.storeRelaxed(QtGlobalStatic::Initialized); + QAS::innerFunction(&storage); + const auto *app = QCoreApplication::instance(); + Q_ASSERT_X(app, Q_FUNC_INFO, + "The application static was used without a QCoreApplication instance"); + QObject::connect(app, &QObject::destroyed, app, reset, Qt::DirectConnection); + guard.storeRelease(QtGlobalStatic::Initialized); } return realPointer(); } static void reset() { - if (guard.loadRelaxed() == QtGlobalStatic::Initialized) { - QMutexLocker locker(&mutex); - realPointer()->~PlainType(); - guard.storeRelaxed(QtGlobalStatic::Uninitialized); - } + // we only synchronize using the mutex here, not the guard + QMutexLocker locker(&mutex); + realPointer()->~PlainType(); + guard.storeRelaxed(QtGlobalStatic::Uninitialized); } }; } // namespace QtGlobalStatic |