/**************************************************************************** ** ** Copyright (C) 2016 The Qt Company Ltd. ** 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 "qatomic.h" /*! \class QAtomicInt \inmodule QtCore \brief The QAtomicInt class provides platform-independent atomic operations on int. \since 4.4 This class is a equivalent to \c{QAtomicInteger}. All other functionality is equivalent. Please see that class for more information. \sa QAtomicInteger, QAtomicPointer */ /*! \class QAtomicInteger \inmodule QtCore \brief The QAtomicInteger class provides platform-independent atomic operations on integers. \ingroup thread \since 5.3 For atomic operations on pointers, see the QAtomicPointer class. An \e atomic operation is a complex operation that completes without interruption. The QAtomicInteger class provides atomic reference counting, test-and-set, fetch-and-store, and fetch-and-add for integers. The template parameter \c T must be a C++ integer type: \list \li 8-bit: char, signed char, unsigned char, qint8, quint8 \li 16-bit: short, unsigned short, qint16, quint16, char16_t (C++11) \li 32-bit: int, unsigned int, qint32, quint32, char32_t (C++11) \li 64-bit: long long, unsigned long long, qint64, quint64 \li platform-specific size: long, unsigned long \li pointer size: qintptr, quintptr, qptrdiff \endlist Of the list above, only the 32-bit- and pointer-sized instantiations are guaranteed to work on all platforms. Support for other sizes depends on the compiler and processor architecture the code is being compiled for. To test whether the other types are supported, check the macro \c Q_ATOMIC_INT\e{nn}_IS_SUPPORTED, where \c{\e{nn}} is the number of bits desired. \section1 The Atomic API \section2 Reference counting The ref() and deref() functions provide an efficient reference counting API. The return value of these functions are used to indicate when the last reference has been released. These functions allow you to implement your own implicitly shared classes. \snippet code/src_corelib_thread_qatomic.cpp 0 \section2 Memory ordering QAtomicInteger provides several implementations of the atomic test-and-set, fetch-and-store, and fetch-and-add functions. Each implementation defines a memory ordering semantic that describes how memory accesses surrounding the atomic instruction are executed by the processor. Since many modern architectures allow out-of-order execution and memory ordering, using the correct semantic is necessary to ensure that your application functions properly on all processors. \list \li Relaxed - memory ordering is unspecified, leaving the compiler and processor to freely reorder memory accesses. \li Acquire - memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \li Release - memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \li Ordered - the same Acquire and Release semantics combined. \endlist \section2 Test-and-set If the current value of the QAtomicInteger is an expected value, the test-and-set functions assign a new value to the QAtomicInteger and return true. If values are \a not the same, these functions do nothing and return false. This operation equates to the following code: \snippet code/src_corelib_thread_qatomic.cpp 1 There are 4 test-and-set functions: testAndSetRelaxed(), testAndSetAcquire(), testAndSetRelease(), and testAndSetOrdered(). See above for an explanation of the different memory ordering semantics. \section2 Fetch-and-store The atomic fetch-and-store functions read the current value of the QAtomicInteger and then assign a new value, returning the original value. This operation equates to the following code: \snippet code/src_corelib_thread_qatomic.cpp 2 There are 4 fetch-and-store functions: fetchAndStoreRelaxed(), fetchAndStoreAcquire(), fetchAndStoreRelease(), and fetchAndStoreOrdered(). See above for an explanation of the different memory ordering semantics. \section2 Fetch-and-add The atomic fetch-and-add functions read the current value of the QAtomicInteger and then add the given value to the current value, returning the original value. This operation equates to the following code: \snippet code/src_corelib_thread_qatomic.cpp 3 There are 4 fetch-and-add functions: fetchAndAddRelaxed(), fetchAndAddAcquire(), fetchAndAddRelease(), and fetchAndAddOrdered(). See above for an explanation of the different memory ordering semantics. \section1 Feature Tests for the Atomic API Providing a platform-independent atomic API that works on all processors is challenging. The API provided by QAtomicInteger is guaranteed to work atomically on all processors. However, since not all processors implement support for every operation provided by QAtomicInteger, it is necessary to expose information about the processor. You can check at compile time which features are supported on your hardware using various macros. These will tell you if your hardware always, sometimes, or does not support a particular operation. The macros have the form Q_ATOMIC_INT\e{nn}_\e{OPERATION}_IS_\e{HOW}_NATIVE. \e{nn} is the size of the integer (in bits), \e{OPERATION} is one of REFERENCE_COUNTING, TEST_AND_SET, FETCH_AND_STORE, or FETCH_AND_ADD, and \e{HOW} is one of ALWAYS, SOMETIMES, or NOT. There will always be exactly one defined macro per operation. For example, if Q_ATOMIC_INT32_REFERENCE_COUNTING_IS_ALWAYS_NATIVE is defined, neither Q_ATOMIC_INT_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE nor Q_ATOMIC_INT32_REFERENCE_COUNTING_IS_NOT_NATIVE will be defined. An operation that completes in constant time is said to be wait-free. Such operations are not implemented using locks or loops of any kind. For atomic operations that are always supported, and that are wait-free, Qt defines the Q_ATOMIC_INT\e{nn}_\e{OPERATION}_IS_WAIT_FREE in addition to the Q_ATOMIC_INT\e{nn}_\e{OPERATION}_IS_ALWAYS_NATIVE. In cases where an atomic operation is only supported in newer generations of the processor, QAtomicInteger also provides a way to check at runtime what your hardware supports with the isReferenceCountingNative(), isTestAndSetNative(), isFetchAndStoreNative(), and isFetchAndAddNative() functions. Wait-free implementations can be detected using the isReferenceCountingWaitFree(), isTestAndSetWaitFree(), isFetchAndStoreWaitFree(), and isFetchAndAddWaitFree() functions. Below is a complete list of all feature macros for QAtomicInteger: \list \li Q_ATOMIC_INT\e{nn}_REFERENCE_COUNTING_IS_ALWAYS_NATIVE \li Q_ATOMIC_INT\e{nn}_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE \li Q_ATOMIC_INT\e{nn}_REFERENCE_COUNTING_IS_NOT_NATIVE \li Q_ATOMIC_INT\e{nn}_REFERENCE_COUNTING_IS_WAIT_FREE \li Q_ATOMIC_INT\e{nn}_TEST_AND_SET_IS_ALWAYS_NATIVE \li Q_ATOMIC_INT\e{nn}_TEST_AND_SET_IS_SOMETIMES_NATIVE \li Q_ATOMIC_INT\e{nn}_TEST_AND_SET_IS_NOT_NATIVE \li Q_ATOMIC_INT\e{nn}_TEST_AND_SET_IS_WAIT_FREE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_STORE_IS_ALWAYS_NATIVE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_STORE_IS_SOMETIMES_NATIVE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_STORE_IS_NOT_NATIVE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_STORE_IS_WAIT_FREE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_ADD_IS_ALWAYS_NATIVE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_ADD_IS_SOMETIMES_NATIVE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_ADD_IS_NOT_NATIVE \li Q_ATOMIC_INT\e{nn}_FETCH_AND_ADD_IS_WAIT_FREE \endlist For compatibility with previous versions of Qt, macros with an empty \e{nn} are equivalent to the 32-bit macros. For example, Q_ATOMIC_INT_REFERENCE_COUNTING_IS_WAIT_FREE is the same as Q_ATOMIC_INT32_REFERENCE_COUNTING_IS_WAIT_FREE. \sa QAtomicPointer */ /*! \fn QAtomicInt::QAtomicInt(int value) Constructs a QAtomicInt with the given \a value. */ /*! \fn QAtomicInteger::QAtomicInteger(T value) Constructs a QAtomicInteger with the given \a value. */ /*! \fn QAtomicInteger::QAtomicInteger(const QAtomicInteger &other) Constructs a copy of \a other. */ /*! \fn QAtomicInteger &QAtomicInteger::operator=(const QAtomicInteger &other) Assigns \a other to this QAtomicInteger and returns a reference to this QAtomicInteger. */ /*! \fn T QAtomicInteger::load() const Atomically loads the value of this QAtomicInteger using relaxed memory ordering. The value is not modified in any way, but note that there's no guarantee that it remains so. \sa store(), loadAcquire() */ /*! \fn T QAtomicInteger::loadAcquire() const Atomically loads the value of this QAtomicInteger using the "Acquire" memory ordering. The value is not modified in any way, but note that there's no guarantee that it remains so. \sa store(), load() */ /*! \fn void QAtomicInteger::store(T newValue) Atomically stores the \a newValue value into this atomic type, using relaxed memory ordering. \sa storeRelease(), load() */ /*! \fn void QAtomicInteger::storeRelease(T newValue) Atomically stores the \a newValue value into this atomic type, using the "Release" memory ordering. \sa store(), load() */ /*! \fn QAtomicInteger::operator T() const \since 5.3 Atomically loads the value of this QAtomicInteger using a sequentially consistent memory ordering if possible; or "Acquire" ordering if not. The value is not modified in any way, but note that there's no guarantee that it remains so. \sa load(), loadAcquire() */ /*! \fn QAtomicInteger &QAtomicInteger::operator=(T newValue) \since 5.3 Atomically stores the \a newValue value into this atomic type using a sequentially consistent memory ordering if possible; or "Release" ordering if not. This function returns a reference to this object. \sa store(), storeRelease() */ /*! \fn bool QAtomicInteger::isReferenceCountingNative() Returns \c true if reference counting is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicInteger::isReferenceCountingWaitFree() Returns \c true if atomic reference counting is wait-free, false otherwise. */ /*! \fn bool QAtomicInteger::ref() Atomically increments the value of this QAtomicInteger. Returns \c true if the new value is non-zero, false otherwise. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa deref(), operator++() */ /*! \fn T QAtomicInteger::operator++() \since 5.3 Atomically pre-increments the value of this QAtomicInteger. Returns the new value of this atomic. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa ref(), operator++(int), operator--() */ /*! \fn T QAtomicInteger::operator++(int) \since 5.3 Atomically post-increments the value of this QAtomicInteger. Returns the old value of this atomic. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa ref(), operator++(), operator--(int) */ /*! \fn bool QAtomicInteger::deref() Atomically decrements the value of this QAtomicInteger. Returns \c true if the new value is non-zero, false otherwise. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa ref(), operator--() */ /*! \fn T QAtomicInteger::operator--() \since 5.3 Atomically pre-decrements the value of this QAtomicInteger. Returns the new value of this atomic. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa deref(), operator--(int), operator++() */ /*! \fn T QAtomicInteger::operator--(int) \since 5.3 Atomically post-decrements the value of this QAtomicInteger. Returns the old value of this atomic. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa deref(), operator--(), operator++(int) */ /*! \fn bool QAtomicInteger::isTestAndSetNative() Returns \c true if test-and-set is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicInteger::isTestAndSetWaitFree() Returns \c true if atomic test-and-set is wait-free, false otherwise. */ /*! \fn bool QAtomicInteger::testAndSetRelaxed(T expectedValue, T newValue) Atomic test-and-set. If the current value of this QAtomicInteger is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicInteger and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. */ /*! \fn bool QAtomicInteger::testAndSetAcquire(T expectedValue, T newValue) Atomic test-and-set. If the current value of this QAtomicInteger is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicInteger and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. */ /*! \fn bool QAtomicInteger::testAndSetRelease(T expectedValue, T newValue) Atomic test-and-set. If the current value of this QAtomicInteger is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicInteger and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. */ /*! \fn bool QAtomicInteger::testAndSetOrdered(T expectedValue, T newValue) Atomic test-and-set. If the current value of this QAtomicInteger is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicInteger and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. */ /*! \fn bool QAtomicInteger::isFetchAndStoreNative() Returns \c true if fetch-and-store is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicInteger::isFetchAndStoreWaitFree() Returns \c true if atomic fetch-and-store is wait-free, false otherwise. */ /*! \fn T QAtomicInteger::fetchAndStoreRelaxed(T newValue) Atomic fetch-and-store. Reads the current value of this QAtomicInteger and then assigns it the \a newValue, returning the original value. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. */ /*! \fn T QAtomicInteger::fetchAndStoreAcquire(T newValue) Atomic fetch-and-store. Reads the current value of this QAtomicInteger and then assigns it the \a newValue, returning the original value. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. */ /*! \fn T QAtomicInteger::fetchAndStoreRelease(T newValue) Atomic fetch-and-store. Reads the current value of this QAtomicInteger and then assigns it the \a newValue, returning the original value. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. */ /*! \fn T QAtomicInteger::fetchAndStoreOrdered(T newValue) Atomic fetch-and-store. Reads the current value of this QAtomicInteger and then assigns it the \a newValue, returning the original value. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. */ /*! \fn bool QAtomicInteger::isFetchAndAddNative() Returns \c true if fetch-and-add is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicInteger::isFetchAndAddWaitFree() Returns \c true if atomic fetch-and-add is wait-free, false otherwise. */ /*! \fn T QAtomicInteger::fetchAndAddRelaxed(T valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicInteger and then adds \a valueToAdd to the current value, returning the original value. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. \sa operator+=(), fetchAndSubRelaxed() */ /*! \fn T QAtomicInteger::fetchAndAddAcquire(T valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicInteger and then adds \a valueToAdd to the current value, returning the original value. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \sa operator+=(), fetchAndSubAcquire() */ /*! \fn T QAtomicInteger::fetchAndAddRelease(T valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicInteger and then adds \a valueToAdd to the current value, returning the original value. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \sa operator+=(), fetchAndSubRelease() */ /*! \fn T QAtomicInteger::fetchAndAddOrdered(T valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicInteger and then adds \a valueToAdd to the current value, returning the original value. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa operator+=(), fetchAndSubOrdered() */ /*! \fn T QAtomicInteger::operator+=(T valueToAdd) \since 5.3 Atomic add-and-fetch. Reads the current value of this QAtomicInteger and then adds \a valueToAdd to the current value, returning the new value value. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa fetchAndAddOrdered(), operator-=() */ /*! \fn T QAtomicInteger::fetchAndSubRelaxed(T valueToSub) \since 5.3 Atomic fetch-and-sub. Reads the current value of this QAtomicInteger and then subtracts \a valueToSub to the current value, returning the original value. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. \sa operator-=(), fetchAndAddRelaxed() */ /*! \fn T QAtomicInteger::fetchAndSubAcquire(T valueToSub) \since 5.3 Atomic fetch-and-sub. Reads the current value of this QAtomicInteger and then subtracts \a valueToSub to the current value, returning the original value. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \sa operator-=(), fetchAndAddAcquire() */ /*! \fn T QAtomicInteger::fetchAndSubRelease(T valueToSub) \since 5.3 Atomic fetch-and-sub. Reads the current value of this QAtomicInteger and then subtracts \a valueToSub to the current value, returning the original value. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \sa operator-=(), fetchAndAddRelease() */ /*! \fn T QAtomicInteger::fetchAndSubOrdered(T valueToSub) \since 5.3 Atomic fetch-and-sub. Reads the current value of this QAtomicInteger and then subtracts \a valueToSub to the current value, returning the original value. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa operator-=(), fetchAndAddOrdered() */ /*! \fn T QAtomicInteger::operator-=(T valueToSub) \since 5.3 Atomic sub-and-fetch. Reads the current value of this QAtomicInteger and then subtracts \a valueToSub to the current value, returning the new value value. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa fetchAndSubOrdered(), operator+=() */ /*! \fn T QAtomicInteger::fetchAndOrRelaxed(T valueToOr) \since 5.3 Atomic fetch-and-or. Reads the current value of this QAtomicInteger and then bitwise-ORs \a valueToOr to the current value, returning the original value. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. \sa operator|=() */ /*! \fn T QAtomicInteger::fetchAndOrAcquire(T valueToOr) \since 5.3 Atomic fetch-and-or. Reads the current value of this QAtomicInteger and then bitwise-ORs \a valueToOr to the current value, returning the original value. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \sa operator|=() */ /*! \fn T QAtomicInteger::fetchAndOrRelease(T valueToOr) \since 5.3 Atomic fetch-and-or. Reads the current value of this QAtomicInteger and then bitwise-ORs \a valueToOr to the current value, returning the original value. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \sa operator|=() */ /*! \fn T QAtomicInteger::fetchAndOrOrdered(T valueToOr) \since 5.3 Atomic fetch-and-or. Reads the current value of this QAtomicInteger and then bitwise-ORs \a valueToOr to the current value, returning the original value. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa operator|=() */ /*! \fn T QAtomicInteger::operator|=(T valueToOr) \since 5.3 Atomic or-and-fetch. Reads the current value of this QAtomicInteger and then bitwise-ORs \a valueToOr to the current value, returning the new value value. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa fetchAndOrOrdered() */ /*! \fn T QAtomicInteger::fetchAndXorRelaxed(T valueToXor) \since 5.3 Atomic fetch-and-xor. Reads the current value of this QAtomicInteger and then bitwise-XORs \a valueToXor to the current value, returning the original value. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. \sa operator^=() */ /*! \fn T QAtomicInteger::fetchAndXorAcquire(T valueToXor) \since 5.3 Atomic fetch-and-xor. Reads the current value of this QAtomicInteger and then bitwise-XORs \a valueToXor to the current value, returning the original value. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \sa operator^=() */ /*! \fn T QAtomicInteger::fetchAndXorRelease(T valueToXor) \since 5.3 Atomic fetch-and-xor. Reads the current value of this QAtomicInteger and then bitwise-XORs \a valueToXor to the current value, returning the original value. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \sa operator^=() */ /*! \fn T QAtomicInteger::fetchAndXorOrdered(T valueToXor) \since 5.3 Atomic fetch-and-xor. Reads the current value of this QAtomicInteger and then bitwise-XORs \a valueToXor to the current value, returning the original value. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa operator^=() */ /*! \fn T QAtomicInteger::operator^=(T valueToXor) \since 5.3 Atomic xor-and-fetch. Reads the current value of this QAtomicInteger and then bitwise-XORs \a valueToXor to the current value, returning the new value value. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa fetchAndXorOrdered() */ /*! \fn T QAtomicInteger::fetchAndAndRelaxed(T valueToAnd) \since 5.3 Atomic fetch-and-and. Reads the current value of this QAtomicInteger and then bitwise-ANDs \a valueToAnd to the current value, returning the original value. This function uses \e relaxed \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. \sa operator&=() */ /*! \fn T QAtomicInteger::fetchAndAndAcquire(T valueToAnd) \since 5.3 Atomic fetch-and-and. Reads the current value of this QAtomicInteger and then bitwise-ANDs \a valueToAnd to the current value, returning the original value. This function uses \e acquire \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \sa operator&=() */ /*! \fn T QAtomicInteger::fetchAndAndRelease(T valueToAnd) \since 5.3 Atomic fetch-and-and. Reads the current value of this QAtomicInteger and then bitwise-ANDs \a valueToAnd to the current value, returning the original value. This function uses \e release \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \sa operator&=() */ /*! \fn T QAtomicInteger::fetchAndAndOrdered(T valueToAnd) \since 5.3 Atomic fetch-and-and. Reads the current value of this QAtomicInteger and then bitwise-ANDs \a valueToAnd to the current value, returning the original value. This function uses \e ordered \l {QAtomicInteger#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. \sa operator&=() */ /*! \fn T QAtomicInteger::operator&=(T valueToAnd) \since 5.3 Atomic add-and-fetch. Reads the current value of this QAtomicInteger and then bitwise-ANDs \a valueToAnd to the current value, returning the new value value. This function uses a sequentially consistent memory ordering if possible; or "Ordered" ordering if not. \sa fetchAndAndOrdered() */ /*! \macro Q_ATOMIC_INTnn_IS_SUPPORTED \relates QAtomicInteger This macro is defined if atomic integers of size \e{nn} (in bits) are supported in this compiler / architecture combination. Q_ATOMIC_INT32_IS_SUPPORTED is always defined. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_REFERENCE_COUNTING_IS_ALWAYS_NATIVE \relates QAtomicInteger This macro is defined if and only if all generations of your processor support atomic reference counting. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE \relates QAtomicInteger This macro is defined when only certain generations of the processor support atomic reference counting. Use the QAtomicInteger::isReferenceCountingNative() function to check what your processor supports. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_REFERENCE_COUNTING_IS_NOT_NATIVE \relates QAtomicInteger This macro is defined when the hardware does not support atomic reference counting. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_REFERENCE_COUNTING_IS_WAIT_FREE \relates QAtomicInteger This macro is defined together with Q_ATOMIC_INTnn_REFERENCE_COUNTING_IS_ALWAYS_NATIVE to indicate that the reference counting is wait-free. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_TEST_AND_SET_IS_ALWAYS_NATIVE \relates QAtomicInteger This macro is defined if and only if your processor supports atomic test-and-set on integers. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_TEST_AND_SET_IS_SOMETIMES_NATIVE \relates QAtomicInteger This macro is defined when only certain generations of the processor support atomic test-and-set on integers. Use the QAtomicInteger::isTestAndSetNative() function to check what your processor supports. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_TEST_AND_SET_IS_NOT_NATIVE \relates QAtomicInteger This macro is defined when the hardware does not support atomic test-and-set on integers. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_TEST_AND_SET_IS_WAIT_FREE \relates QAtomicInteger This macro is defined together with Q_ATOMIC_INTnn_TEST_AND_SET_IS_ALWAYS_NATIVE to indicate that the atomic test-and-set on integers is wait-free. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_STORE_IS_ALWAYS_NATIVE \relates QAtomicInteger This macro is defined if and only if your processor supports atomic fetch-and-store on integers. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_STORE_IS_SOMETIMES_NATIVE \relates QAtomicInteger This macro is defined when only certain generations of the processor support atomic fetch-and-store on integers. Use the QAtomicInteger::isFetchAndStoreNative() function to check what your processor supports. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_STORE_IS_NOT_NATIVE \relates QAtomicInteger This macro is defined when the hardware does not support atomic fetch-and-store on integers. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_STORE_IS_WAIT_FREE \relates QAtomicInteger This macro is defined together with Q_ATOMIC_INTnn_FETCH_AND_STORE_IS_ALWAYS_NATIVE to indicate that the atomic fetch-and-store on integers is wait-free. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_ADD_IS_ALWAYS_NATIVE \relates QAtomicInteger This macro is defined if and only if your processor supports atomic fetch-and-add on integers. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_ADD_IS_SOMETIMES_NATIVE \relates QAtomicInteger This macro is defined when only certain generations of the processor support atomic fetch-and-add on integers. Use the QAtomicInteger::isFetchAndAddNative() function to check what your processor supports. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_ADD_IS_NOT_NATIVE \relates QAtomicInteger This macro is defined when the hardware does not support atomic fetch-and-add on integers. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \macro Q_ATOMIC_INTnn_FETCH_AND_ADD_IS_WAIT_FREE \relates QAtomicInteger This macro is defined together with Q_ATOMIC_INTnn_FETCH_AND_ADD_IS_ALWAYS_NATIVE to indicate that the atomic fetch-and-add on integers is wait-free. \e{nn} is the size of the integer, in bits (8, 16, 32 or 64). */ /*! \class QAtomicPointer \inmodule QtCore \brief The QAtomicPointer class is a template class that provides platform-independent atomic operations on pointers. \since 4.4 \ingroup thread For atomic operations on integers, see the QAtomicInteger class. An \e atomic operation is a complex operation that completes without interruption. The QAtomicPointer class provides atomic test-and-set, fetch-and-store, and fetch-and-add for pointers. \section1 The Atomic API \section2 Memory ordering QAtomicPointer provides several implementations of the atomic test-and-set, fetch-and-store, and fetch-and-add functions. Each implementation defines a memory ordering semantic that describes how memory accesses surrounding the atomic instruction are executed by the processor. Since many modern architectures allow out-of-order execution and memory ordering, using the correct semantic is necessary to ensure that your application functions properly on all processors. \list \li Relaxed - memory ordering is unspecified, leaving the compiler and processor to freely reorder memory accesses. \li Acquire - memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. \li Release - memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. \li Ordered - the same Acquire and Release semantics combined. \endlist \section2 Test-and-set If the current value of the QAtomicPointer is an expected value, the test-and-set functions assign a new value to the QAtomicPointer and return true. If values are \a not the same, these functions do nothing and return false. This operation equates to the following code: \snippet code/src_corelib_thread_qatomic.cpp 4 There are 4 test-and-set functions: testAndSetRelaxed(), testAndSetAcquire(), testAndSetRelease(), and testAndSetOrdered(). See above for an explanation of the different memory ordering semantics. \section2 Fetch-and-store The atomic fetch-and-store functions read the current value of the QAtomicPointer and then assign a new value, returning the original value. This operation equates to the following code: \snippet code/src_corelib_thread_qatomic.cpp 5 There are 4 fetch-and-store functions: fetchAndStoreRelaxed(), fetchAndStoreAcquire(), fetchAndStoreRelease(), and fetchAndStoreOrdered(). See above for an explanation of the different memory ordering semantics. \section2 Fetch-and-add The atomic fetch-and-add functions read the current value of the QAtomicPointer and then add the given value to the current value, returning the original value. This operation equates to the following code: \snippet code/src_corelib_thread_qatomic.cpp 6 There are 4 fetch-and-add functions: fetchAndAddRelaxed(), fetchAndAddAcquire(), fetchAndAddRelease(), and fetchAndAddOrdered(). See above for an explanation of the different memory ordering semantics. \section1 Feature Tests for the Atomic API Providing a platform-independent atomic API that works on all processors is challenging. The API provided by QAtomicPointer is guaranteed to work atomically on all processors. However, since not all processors implement support for every operation provided by QAtomicPointer, it is necessary to expose information about the processor. You can check at compile time which features are supported on your hardware using various macros. These will tell you if your hardware always, sometimes, or does not support a particular operation. The macros have the form Q_ATOMIC_POINTER_\e{OPERATION}_IS_\e{HOW}_NATIVE. \e{OPERATION} is one of TEST_AND_SET, FETCH_AND_STORE, or FETCH_AND_ADD, and \e{HOW} is one of ALWAYS, SOMETIMES, or NOT. There will always be exactly one defined macro per operation. For example, if Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE is defined, neither Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE nor Q_ATOMIC_POINTER_TEST_AND_SET_IS_NOT_NATIVE will be defined. An operation that completes in constant time is said to be wait-free. Such operations are not implemented using locks or loops of any kind. For atomic operations that are always supported, and that are wait-free, Qt defines the Q_ATOMIC_POINTER_\e{OPERATION}_IS_WAIT_FREE in addition to the Q_ATOMIC_POINTER_\e{OPERATION}_IS_ALWAYS_NATIVE. In cases where an atomic operation is only supported in newer generations of the processor, QAtomicPointer also provides a way to check at runtime what your hardware supports with the isTestAndSetNative(), isFetchAndStoreNative(), and isFetchAndAddNative() functions. Wait-free implementations can be detected using the isTestAndSetWaitFree(), isFetchAndStoreWaitFree(), and isFetchAndAddWaitFree() functions. Below is a complete list of all feature macros for QAtomicPointer: \list \li Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE \li Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE \li Q_ATOMIC_POINTER_TEST_AND_SET_IS_NOT_NATIVE \li Q_ATOMIC_POINTER_TEST_AND_SET_IS_WAIT_FREE \li Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE \li Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_SOMETIMES_NATIVE \li Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_NOT_NATIVE \li Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_WAIT_FREE \li Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE \li Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_SOMETIMES_NATIVE \li Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_NOT_NATIVE \li Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_WAIT_FREE \endlist \sa QAtomicInteger */ /*! \fn QAtomicPointer::QAtomicPointer(T *value) Constructs a QAtomicPointer with the given \a value. */ /*! \fn QAtomicPointer::QAtomicPointer(const QAtomicPointer &other) Constructs a copy of \a other. */ /*! \fn QAtomicPointer &QAtomicPointer::operator=(const QAtomicPointer &other) Assigns \a other to this QAtomicPointer and returns a reference to this QAtomicPointer. */ /*! \fn T *QAtomicPointer::load() const Atomically loads the value of this QAtomicPointer using relaxed memory ordering. The value is not modified in any way, but note that there's no guarantee that it remains so. \sa store(), loadAcquire() */ /*! \fn T *QAtomicPointer::loadAcquire() const Atomically loads the value of this QAtomicPointer using the "Acquire" memory ordering. The value is not modified in any way, but note that there's no guarantee that it remains so. \sa store(), load() */ /*! \fn void QAtomicPointer::store(T *newValue) Atomically stores the \a newValue value into this atomic type, using relaxed memory ordering. \sa storeRelease(), load() */ /*! \fn void QAtomicPointer::storeRelease(T *newValue) Atomically stores the \a newValue value into this atomic type, using the "Release" memory ordering. \sa store(), load() */ /*! \fn bool QAtomicPointer::isTestAndSetNative() Returns \c true if test-and-set is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicPointer::isTestAndSetWaitFree() Returns \c true if atomic test-and-set is wait-free, false otherwise. */ /*! \fn bool QAtomicPointer::testAndSetRelaxed(T *expectedValue, T *newValue) Atomic test-and-set. If the current value of this QAtomicPointer is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicPointer and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e relaxed \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. */ /*! \fn bool QAtomicPointer::testAndSetAcquire(T *expectedValue, T *newValue) Atomic test-and-set. If the current value of this QAtomicPointer is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicPointer and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e acquire \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. */ /*! \fn bool QAtomicPointer::testAndSetRelease(T *expectedValue, T *newValue) Atomic test-and-set. If the current value of this QAtomicPointer is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicPointer and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e release \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. */ /*! \fn bool QAtomicPointer::testAndSetOrdered(T *expectedValue, T *newValue) Atomic test-and-set. If the current value of this QAtomicPointer is the \a expectedValue, the test-and-set functions assign the \a newValue to this QAtomicPointer and return true. If the values are \e not the same, this function does nothing and returns \c false. This function uses \e ordered \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. */ /*! \fn bool QAtomicPointer::isFetchAndStoreNative() Returns \c true if fetch-and-store is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicPointer::isFetchAndStoreWaitFree() Returns \c true if atomic fetch-and-store is wait-free, false otherwise. */ /*! \fn T *QAtomicPointer::fetchAndStoreRelaxed(T *newValue) Atomic fetch-and-store. Reads the current value of this QAtomicPointer and then assigns it the \a newValue, returning the original value. This function uses \e relaxed \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. */ /*! \fn T *QAtomicPointer::fetchAndStoreAcquire(T *newValue) Atomic fetch-and-store. Reads the current value of this QAtomicPointer and then assigns it the \a newValue, returning the original value. This function uses \e acquire \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. */ /*! \fn T *QAtomicPointer::fetchAndStoreRelease(T *newValue) Atomic fetch-and-store. Reads the current value of this QAtomicPointer and then assigns it the \a newValue, returning the original value. This function uses \e release \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. */ /*! \fn T *QAtomicPointer::fetchAndStoreOrdered(T *newValue) Atomic fetch-and-store. Reads the current value of this QAtomicPointer and then assigns it the \a newValue, returning the original value. This function uses \e ordered \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. */ /*! \fn bool QAtomicPointer::isFetchAndAddNative() Returns \c true if fetch-and-add is implemented using atomic processor instructions, false otherwise. */ /*! \fn bool QAtomicPointer::isFetchAndAddWaitFree() Returns \c true if atomic fetch-and-add is wait-free, false otherwise. */ /*! \fn T *QAtomicPointer::fetchAndAddRelaxed(qptrdiff valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicPointer and then adds \a valueToAdd to the current value, returning the original value. This function uses \e relaxed \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, leaving the compiler and processor to freely reorder memory accesses. */ /*! \fn T *QAtomicPointer::fetchAndAddAcquire(qptrdiff valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicPointer and then adds \a valueToAdd to the current value, returning the original value. This function uses \e acquire \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access following the atomic operation (in program order) may not be re-ordered before the atomic operation. */ /*! \fn T *QAtomicPointer::fetchAndAddRelease(qptrdiff valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicPointer and then adds \a valueToAdd to the current value, returning the original value. This function uses \e release \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access before the atomic operation (in program order) may not be re-ordered after the atomic operation. */ /*! \fn T *QAtomicPointer::fetchAndAddOrdered(qptrdiff valueToAdd) Atomic fetch-and-add. Reads the current value of this QAtomicPointer and then adds \a valueToAdd to the current value, returning the original value. This function uses \e ordered \l {QAtomicPointer#Memory ordering}{memory ordering} semantics, which ensures that memory access before and after the atomic operation (in program order) may not be re-ordered. */ /*! \macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE \relates QAtomicPointer This macro is defined if and only if your processor supports atomic test-and-set on pointers. */ /*! \macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE \relates QAtomicPointer This macro is defined when only certain generations of the processor support atomic test-and-set on pointers. Use the QAtomicPointer::isTestAndSetNative() function to check what your processor supports. */ /*! \macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_NOT_NATIVE \relates QAtomicPointer This macro is defined when the hardware does not support atomic test-and-set on pointers. */ /*! \macro Q_ATOMIC_POINTER_TEST_AND_SET_IS_WAIT_FREE \relates QAtomicPointer This macro is defined together with Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE to indicate that the atomic test-and-set on pointers is wait-free. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE \relates QAtomicPointer This macro is defined if and only if your processor supports atomic fetch-and-store on pointers. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_SOMETIMES_NATIVE \relates QAtomicPointer This macro is defined when only certain generations of the processor support atomic fetch-and-store on pointers. Use the QAtomicPointer::isFetchAndStoreNative() function to check what your processor supports. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_NOT_NATIVE \relates QAtomicPointer This macro is defined when the hardware does not support atomic fetch-and-store on pointers. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_WAIT_FREE \relates QAtomicPointer This macro is defined together with Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE to indicate that the atomic fetch-and-store on pointers is wait-free. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE \relates QAtomicPointer This macro is defined if and only if your processor supports atomic fetch-and-add on pointers. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_SOMETIMES_NATIVE \relates QAtomicPointer This macro is defined when only certain generations of the processor support atomic fetch-and-add on pointers. Use the QAtomicPointer::isFetchAndAddNative() function to check what your processor supports. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_NOT_NATIVE \relates QAtomicPointer This macro is defined when the hardware does not support atomic fetch-and-add on pointers. */ /*! \macro Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_WAIT_FREE \relates QAtomicPointer This macro is defined together with Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE to indicate that the atomic fetch-and-add on pointers is wait-free. */ // static checks #ifndef Q_ATOMIC_INT32_IS_SUPPORTED # error "Q_ATOMIC_INT32_IS_SUPPORTED must be defined" #endif #if !defined(Q_ATOMIC_INT64_IS_SUPPORTED) && QT_POINTER_SIZE == 8 // 64-bit platform # error "Q_ATOMIC_INT64_IS_SUPPORTED must be defined on a 64-bit platform" #endif QT_BEGIN_NAMESPACE // The following specializations must always be defined Q_STATIC_ASSERT(sizeof(QAtomicInteger)); Q_STATIC_ASSERT(sizeof(QAtomicInteger)); Q_STATIC_ASSERT(sizeof(QAtomicInteger)); Q_STATIC_ASSERT(sizeof(QAtomicInteger)); Q_STATIC_ASSERT(sizeof(QAtomicInteger)); #ifdef Q_COMPILER_UNICODE_STRINGS Q_STATIC_ASSERT(sizeof(QAtomicInteger)); #endif #ifdef Q_ATOMIC_INT16_IS_SUPPORTED Q_STATIC_ASSERT(sizeof(QAtomicInteger)); Q_STATIC_ASSERT(sizeof(QAtomicInteger)); # if WCHAR_MAX < 0x10000 Q_STATIC_ASSERT(sizeof(QAtomicInteger)); # endif # ifdef Q_COMPILER_UNICODE_STRINGS Q_STATIC_ASSERT(sizeof(QAtomicInteger)); # endif #endif #ifdef Q_ATOMIC_INT64_IS_SUPPORTED Q_STATIC_ASSERT(sizeof(QAtomicInteger)); Q_STATIC_ASSERT(sizeof(QAtomicInteger)); #endif #if WCHAR_MAX == INT_MAX Q_STATIC_ASSERT(sizeof(QAtomicInteger)); #endif QT_END_NAMESPACE