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-rw-r--r--src/corelib/kernel/qapplicationstatic.h75
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