| 1 | // Copyright (C) 2021 The Qt Company Ltd. |
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| 2 | // Copyright (C) 2021 Intel Corporation. |
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| 3 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 4 | |
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| 5 | #ifndef QAPPLICATIONSTATIC_H |
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| 6 | #define QAPPLICATIONSTATIC_H |
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| 7 | |
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| 8 | #include <QtCore/QMutex> |
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| 9 | #include <QtCore/qcoreapplication.h> |
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| 10 | #include <QtCore/qglobalstatic.h> |
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| 11 | |
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| 12 | #include <new> |
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| 13 | |
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| 14 | #if 0 |
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| 15 | #pragma qt_class(QApplicationStatic) |
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| 16 | #endif |
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| 17 | |
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| 18 | QT_BEGIN_NAMESPACE |
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| 19 | |
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| 20 | namespace QtGlobalStatic { |
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| 21 | template <typename QAS> struct ApplicationHolder |
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| 22 | { |
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| 23 | using Type = typename QAS::QAS_Type; |
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| 24 | using PlainType = std::remove_cv_t<Type>; |
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| 25 | |
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| 26 | Q_CONSTINIT static inline struct { alignas(Type) unsigned char data[sizeof(Type)]; } storage = {}; |
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| 27 | Q_CONSTINIT static inline QBasicAtomicInteger<qint8> guard = { QtGlobalStatic::Uninitialized }; |
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| 28 | Q_CONSTINIT static inline QBasicMutex mutex {}; |
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| 29 | |
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| 30 | static constexpr bool MutexLockIsNoexcept = noexcept(mutex.lock()); |
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| 31 | static constexpr bool ConstructionIsNoexcept = noexcept(QAS::innerFunction(nullptr)); |
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| 32 | |
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| 33 | ApplicationHolder() = default; |
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| 34 | Q_DISABLE_COPY_MOVE(ApplicationHolder) |
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| 35 | ~ApplicationHolder() |
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| 36 | { |
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| 37 | if (guard.loadAcquire() == QtGlobalStatic::Initialized) { |
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| 38 | // No mutex! Up to external code to ensure no race happens. |
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| 39 | guard.storeRelease(newValue: QtGlobalStatic::Destroyed); |
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| 40 | realPointer()->~PlainType(); |
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| 41 | } |
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| 42 | } |
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| 43 | |
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| 44 | static PlainType *realPointer() |
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| 45 | { |
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| 46 | return std::launder(reinterpret_cast<PlainType *>(&storage)); |
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| 47 | } |
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| 48 | |
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| 49 | // called from QGlobalStatic::instance() |
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| 50 | PlainType *pointer() noexcept(MutexLockIsNoexcept && ConstructionIsNoexcept) |
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| 51 | { |
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| 52 | if (guard.loadAcquire() == QtGlobalStatic::Initialized) |
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| 53 | return realPointer(); |
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| 54 | QMutexLocker locker(&mutex); |
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| 55 | if (guard.loadRelaxed() == QtGlobalStatic::Uninitialized) { |
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| 56 | QAS::innerFunction(&storage); |
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| 57 | const auto *app = QCoreApplication::instance(); |
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| 58 | Q_ASSERT_X(app, Q_FUNC_INFO, |
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| 59 | "The application static was used without a QCoreApplication instance" ); |
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| 60 | QObject::connect(app, &QObject::destroyed, app, reset, Qt::DirectConnection); |
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| 61 | guard.storeRelease(newValue: QtGlobalStatic::Initialized); |
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| 62 | } |
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| 63 | return realPointer(); |
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| 64 | } |
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| 65 | |
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| 66 | static void reset() |
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| 67 | { |
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| 68 | // we only synchronize using the mutex here, not the guard |
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| 69 | QMutexLocker locker(&mutex); |
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| 70 | realPointer()->~PlainType(); |
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| 71 | guard.storeRelaxed(newValue: QtGlobalStatic::Uninitialized); |
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| 72 | } |
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| 73 | }; |
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| 74 | } // namespace QtGlobalStatic |
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| 75 | |
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| 76 | #define Q_APPLICATION_STATIC(TYPE, NAME, ...) \ |
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| 77 | namespace { struct Q_QAS_ ## NAME { \ |
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| 78 | typedef TYPE QAS_Type; \ |
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| 79 | static void innerFunction(void *pointer) \ |
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| 80 | noexcept(noexcept(std::remove_cv_t<QAS_Type>(__VA_ARGS__))) \ |
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| 81 | { \ |
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| 82 | new (pointer) QAS_Type(__VA_ARGS__); \ |
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| 83 | } \ |
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| 84 | }; } \ |
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| 85 | static QGlobalStatic<QtGlobalStatic::ApplicationHolder<Q_QAS_ ## NAME>> NAME;\ |
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| 86 | /**/ |
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| 87 | |
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| 88 | QT_END_NAMESPACE |
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| 89 | |
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| 90 | #endif // QAPPLICATIONSTATIC_H |
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| 91 | |
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