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-rw-r--r--src/corelib/global/qglobalstatic.h168
1 files changed, 79 insertions, 89 deletions
diff --git a/src/corelib/global/qglobalstatic.h b/src/corelib/global/qglobalstatic.h
index 4aa496e7f6..93127adab3 100644
--- a/src/corelib/global/qglobalstatic.h
+++ b/src/corelib/global/qglobalstatic.h
@@ -1,49 +1,14 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 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.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include <QtCore/qglobal.h>
+// 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 QGLOBALSTATIC_H
#define QGLOBALSTATIC_H
+#include <QtCore/qassert.h>
#include <QtCore/qatomic.h>
+#include <QtCore/qtclasshelpermacros.h>
+#include <atomic> // for bootstrapped (no thread) builds
#include <type_traits>
QT_BEGIN_NAMESPACE
@@ -55,84 +20,109 @@ enum GuardValues {
Uninitialized = 0,
Initializing = 1
};
-}
-#if defined(Q_OS_UNIX) && defined(Q_CC_INTEL)
-// Work around Intel issue ID 6000058488:
-// local statics inside an inline function inside an anonymous namespace are global
-// symbols (this affects the IA-64 C++ ABI, so OS X and Linux only)
-# define Q_GLOBAL_STATIC_INTERNAL_DECORATION Q_DECL_HIDDEN
-#else
-# define Q_GLOBAL_STATIC_INTERNAL_DECORATION Q_DECL_HIDDEN inline
+template <typename QGS> union Holder
+{
+ using Type = typename QGS::QGS_Type;
+ using PlainType = std::remove_cv_t<Type>;
+
+ static constexpr bool ConstructionIsNoexcept = noexcept(QGS::innerFunction(nullptr));
+ Q_CONSTINIT static inline QBasicAtomicInteger<qint8> guard = { QtGlobalStatic::Uninitialized };
+
+ // union's sole member
+ PlainType storage;
+
+ Holder() noexcept(ConstructionIsNoexcept)
+ {
+ QGS::innerFunction(pointer());
+ guard.storeRelaxed(QtGlobalStatic::Initialized);
+ }
+
+ ~Holder()
+ {
+ // TSAN does not support atomic_thread_fence and GCC complains:
+ // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97868
+ // https://github.com/google/sanitizers/issues/1352
+QT_WARNING_PUSH
+#if defined(Q_CC_GNU_ONLY) && Q_CC_GNU >= 1100
+QT_WARNING_DISABLE_GCC("-Wtsan")
#endif
+ // import changes to *pointer() by other threads before running ~PlainType():
+ std::atomic_thread_fence(std::memory_order_acquire);
+QT_WARNING_POP
+ pointer()->~PlainType();
+ guard.storeRelease(QtGlobalStatic::Destroyed);
+ }
-#define Q_GLOBAL_STATIC_INTERNAL(ARGS) \
- Q_GLOBAL_STATIC_INTERNAL_DECORATION Type *innerFunction() \
- { \
- struct HolderBase { \
- HolderBase() = default; \
- ~HolderBase() noexcept \
- { if (guard.loadRelaxed() == QtGlobalStatic::Initialized) \
- guard.storeRelaxed(QtGlobalStatic::Destroyed); } \
- Q_DISABLE_COPY_MOVE(HolderBase) \
- }; \
- static struct Holder : public HolderBase { \
- Type value; \
- Holder() \
- noexcept(noexcept(typename std::remove_cv<Type>::type ARGS)) \
- : value ARGS \
- { guard.storeRelaxed(QtGlobalStatic::Initialized); } \
- } holder; \
- return &holder.value; \
+ PlainType *pointer() noexcept
+ {
+ return &storage;
}
+ Q_DISABLE_COPY_MOVE(Holder)
+};
+}
-// this class must be POD, unless the compiler supports thread-safe statics
-template <typename T, T *(&innerFunction)(), QBasicAtomicInt &guard>
-struct QGlobalStatic
+template <typename Holder> struct QGlobalStatic
{
- typedef T Type;
+ using Type = typename Holder::Type;
- bool isDestroyed() const { return guard.loadRelaxed() <= QtGlobalStatic::Destroyed; }
- bool exists() const { return guard.loadRelaxed() == QtGlobalStatic::Initialized; }
+ bool isDestroyed() const noexcept { return guardValue() <= QtGlobalStatic::Destroyed; }
+ bool exists() const noexcept { return guardValue() == QtGlobalStatic::Initialized; }
operator Type *()
{
if (isDestroyed())
return nullptr;
- return innerFunction();
+ return instance();
}
Type *operator()()
{
if (isDestroyed())
return nullptr;
- return innerFunction();
+ return instance();
}
Type *operator->()
{
- Q_ASSERT_X(!isDestroyed(), "Q_GLOBAL_STATIC",
+ Q_ASSERT_X(!isDestroyed(), Q_FUNC_INFO,
"The global static was used after being destroyed");
- return innerFunction();
+ return instance();
}
Type &operator*()
{
- Q_ASSERT_X(!isDestroyed(), "Q_GLOBAL_STATIC",
+ Q_ASSERT_X(!isDestroyed(), Q_FUNC_INFO,
"The global static was used after being destroyed");
- return *innerFunction();
+ return *instance();
+ }
+
+protected:
+ static Type *instance() noexcept(Holder::ConstructionIsNoexcept)
+ {
+ static Holder holder;
+ return holder.pointer();
+ }
+ static QtGlobalStatic::GuardValues guardValue() noexcept
+ {
+ return QtGlobalStatic::GuardValues(Holder::guard.loadAcquire());
}
};
#define Q_GLOBAL_STATIC_WITH_ARGS(TYPE, NAME, ARGS) \
- namespace { namespace Q_QGS_ ## NAME { \
- typedef TYPE Type; \
- QBasicAtomicInt guard = Q_BASIC_ATOMIC_INITIALIZER(QtGlobalStatic::Uninitialized); \
- Q_GLOBAL_STATIC_INTERNAL(ARGS) \
- } } \
- static QGlobalStatic<TYPE, \
- Q_QGS_ ## NAME::innerFunction, \
- Q_QGS_ ## NAME::guard> NAME;
-
-#define Q_GLOBAL_STATIC(TYPE, NAME) \
- Q_GLOBAL_STATIC_WITH_ARGS(TYPE, NAME, ())
+ QT_WARNING_PUSH \
+ QT_WARNING_DISABLE_CLANG("-Wunevaluated-expression") \
+ namespace { struct Q_QGS_ ## NAME { \
+ typedef TYPE QGS_Type; \
+ static void innerFunction(void *pointer) \
+ noexcept(noexcept(std::remove_cv_t<QGS_Type> ARGS)) \
+ { \
+ new (pointer) QGS_Type ARGS; \
+ } \
+ }; } \
+ Q_CONSTINIT static QGlobalStatic<QtGlobalStatic::Holder<Q_QGS_ ## NAME>> NAME; \
+ QT_WARNING_POP
+ /**/
+
+#define Q_GLOBAL_STATIC(TYPE, NAME, ...) \
+ Q_GLOBAL_STATIC_WITH_ARGS(TYPE, NAME, (__VA_ARGS__))
QT_END_NAMESPACE
#endif // QGLOBALSTATIC_H