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/****************************************************************************
**
** 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>
#ifndef QGLOBALSTATIC_H
#define QGLOBALSTATIC_H
#include <QtCore/qatomic.h>
QT_BEGIN_NAMESPACE
namespace QtGlobalStatic {
enum GuardValues {
Destroyed = -2,
Initialized = -1,
Uninitialized = 0,
Initializing = 1
};
}
#if defined(QT_NO_THREAD) || defined(Q_COMPILER_THREADSAFE_STATICS)
// some compilers support thread-safe statics
// The IA-64 C++ ABI requires this, so we know that all GCC versions since 3.4
// support it. C++11 also requires this behavior.
// Clang and Intel CC masquerade as GCC when compiling on Linux.
//
// Apple's libc++abi however uses a global lock for initializing local statics,
// which will block other threads also trying to initialize a local static
// until the constructor returns ...
// We better avoid these kind of problems by using our own locked implementation.
#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
#endif
#define Q_GLOBAL_STATIC_INTERNAL(ARGS) \
Q_GLOBAL_STATIC_INTERNAL_DECORATION Type *innerFunction() \
{ \
struct HolderBase { \
~HolderBase() Q_DECL_NOTHROW \
{ if (guard.load() == QtGlobalStatic::Initialized) \
guard.store(QtGlobalStatic::Destroyed); } \
}; \
static struct Holder : public HolderBase { \
Type value; \
Holder() \
Q_DECL_NOEXCEPT_EXPR(noexcept(Type ARGS)) \
: value ARGS \
{ guard.store(QtGlobalStatic::Initialized); } \
} holder; \
return &holder.value; \
}
#else
// We don't know if this compiler supports thread-safe global statics
// so use our own locked implementation
QT_END_NAMESPACE
#include <QtCore/qmutex.h>
QT_BEGIN_NAMESPACE
#define Q_GLOBAL_STATIC_INTERNAL(ARGS) \
Q_DECL_HIDDEN inline Type *innerFunction() \
{ \
static Type *d; \
static QBasicMutex mutex; \
int x = guard.loadAcquire(); \
if (Q_UNLIKELY(x >= QtGlobalStatic::Uninitialized)) { \
QMutexLocker locker(&mutex); \
if (guard.load() == QtGlobalStatic::Uninitialized) { \
d = new Type ARGS; \
static struct Cleanup { \
~Cleanup() { \
delete d; \
guard.store(QtGlobalStatic::Destroyed); \
} \
} cleanup; \
guard.storeRelease(QtGlobalStatic::Initialized); \
} \
} \
return d; \
}
#endif
// this class must be POD, unless the compiler supports thread-safe statics
template <typename T, T *(&innerFunction)(), QBasicAtomicInt &guard>
struct QGlobalStatic
{
typedef T Type;
bool isDestroyed() const { return guard.load() <= QtGlobalStatic::Destroyed; }
bool exists() const { return guard.load() == QtGlobalStatic::Initialized; }
operator Type *() { if (isDestroyed()) return 0; return innerFunction(); }
Type *operator()() { if (isDestroyed()) return 0; return innerFunction(); }
Type *operator->()
{
Q_ASSERT_X(!isDestroyed(), "Q_GLOBAL_STATIC", "The global static was used after being destroyed");
return innerFunction();
}
Type &operator*()
{
Q_ASSERT_X(!isDestroyed(), "Q_GLOBAL_STATIC", "The global static was used after being destroyed");
return *innerFunction();
}
};
#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_END_NAMESPACE
#endif // QGLOBALSTATIC_H
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