C++ Q_BASIC_ATOMIC_INITIALIZER函数代码示例

 static int qt_metatype_id() \
 { \
     static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
     if (!metatype_id.load()) \
         metatype_id.store(qRegisterMetaType< QPair<qreal,QColor > >("QPair<qreal,QColor >")); \
     return metatype_id.load(); \
 } \

 static int qt_metatype_id() \
 { \
     static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
     if (!metatype_id) \
         metatype_id = qRegisterMetaType< QVector<QPair<qreal,QColor> > >("QVector<QPair<qreal,QColor> >"); \
     return metatype_id; \
 } \

static int unixCheckClockType()
{
#if (_POSIX_MONOTONIC_CLOCK-0 == 0) && defined(_SC_MONOTONIC_CLOCK)
    // we need a value we can store in a clockid_t that isn't a valid clock
    // check if the valid ones are both non-negative or both non-positive
#  if CLOCK_MONOTONIC >= 0 && CLOCK_REALTIME >= 0
#    define IS_VALID_CLOCK(clock)    (clock >= 0)
#    define INVALID_CLOCK            -1
#  elif CLOCK_MONOTONIC <= 0 && CLOCK_REALTIME <= 0
#    define IS_VALID_CLOCK(clock)    (clock <= 0)
#    define INVALID_CLOCK            1
#  else
#    error "Sorry, your system has weird values for CLOCK_MONOTONIC and CLOCK_REALTIME"
#  endif

    static QBasicAtomicInt clockToUse = Q_BASIC_ATOMIC_INITIALIZER(INVALID_CLOCK);
    int clock = clockToUse.loadAcquire();
    if (Q_LIKELY(IS_VALID_CLOCK(clock)))
        return clock;

    // detect if the system supports monotonic timers
    clock = sysconf(_SC_MONOTONIC_CLOCK) > 0 ? CLOCK_MONOTONIC : CLOCK_REALTIME;
    clockToUse.storeRelease(clock);
    return clock;

#  undef INVALID_CLOCK
#  undef IS_VALID_CLOCK
#elif (_POSIX_MONOTONIC_CLOCK-0) > 0
    return CLOCK_MONOTONIC;
#else
    return CLOCK_REALTIME;
#endif
}

 static int qt_metatype_id() \
 { \
     static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
     if (!metatype_id.load()) \
         metatype_id.store(qRegisterMetaType< QHash<int,QByteArray > >("QHash<int,QByteArray >")); \
     return metatype_id.load(); \
 } \

 static int qt_metatype_id() \
 { \
     static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
     if (!metatype_id) \
         metatype_id = qRegisterMetaType< QMap<int,QVariant> >("QMap<int,QVariant>"); \
     return metatype_id; \
 } \

 static int qt_metatype_id() \
 { \
     static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
     if (!metatype_id) \
         metatype_id = qRegisterMetaType< QList<QPair<QByteArray,QString> > >("QList<QPair<QByteArray,QString> >"); \
     return metatype_id; \
 } \

 static int qt_metatype_id() \
 { \
     static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
     if (!metatype_id) \
         metatype_id = qRegisterMetaType< QMultiMap<QString,QString> >("QMultiMap<QString,QString>"); \
     return metatype_id; \
 } \

// Lifted from Qt. I don't think they would mind. ;)
// Re-lift again from Qt whenever a proper replacement for pthread_once appears
static void qt_ignore_sigpipe()
{
    static QBasicAtomicInt atom = Q_BASIC_ATOMIC_INITIALIZER(0);
    if (atom.testAndSetRelaxed(0, 1)) {
        struct sigaction noaction;
        memset(&noaction, 0, sizeof(noaction));
        noaction.sa_handler = SIG_IGN;
        sigaction(SIGPIPE, &noaction, 0);
    }
}

    static void messageHandler(QtMsgType type, const QMessageLogContext & context, const QString &message)
    {
        static QBasicAtomicInt counter = Q_BASIC_ATOMIC_INITIALIZER(QTest::maxWarnings);

        if (QTest::TestLoggers::loggerCount() == 0) {
            // if this goes wrong, something is seriously broken.
            qInstallMessageHandler(oldMessageHandler);
            QTEST_ASSERT(QTest::TestLoggers::loggerCount() != 0);
        }

        if (handleIgnoredMessage(type, message))
            // the message is expected, so just swallow it.
            return;

        QString msg = qFormatLogMessage(type, context, message);

        if (type != QtFatalMsg) {
            if (counter.load() <= 0)
                return;

            if (!counter.deref()) {
                QTest::TestLoggers::addMessage(QAbstractTestLogger::QSystem,
                        QStringLiteral("Maximum amount of warnings exceeded. Use -maxwarnings to override."));
                return;
            }
        }

        switch (type) {
        case QtDebugMsg:
            QTest::TestLoggers::addMessage(QAbstractTestLogger::QDebug, msg);
            break;
        case QtCriticalMsg:
            QTest::TestLoggers::addMessage(QAbstractTestLogger::QSystem, msg);
            break;
        case QtWarningMsg:
            QTest::TestLoggers::addMessage(QAbstractTestLogger::QWarning, msg);
            break;
        case QtFatalMsg:
            QTest::TestLoggers::addMessage(QAbstractTestLogger::QFatal, msg);
            /* Right now, we're inside the custom message handler and we're
             * being qt_message_output in qglobal.cpp. After we return from
             * this function, it will proceed with calling exit() and abort()
             * and hence crash. Therefore, we call these logging functions such
             * that we wrap up nicely, and in particular produce well-formed XML. */
            QTestResult::addFailure("Received a fatal error.", "Unknown file", 0);
            QTestLog::leaveTestFunction();
            QTestLog::stopLogging();
            break;
        }
    }

KConfigPrivate::KConfigPrivate(KConfig::OpenFlags flags,
                               QStandardPaths::StandardLocation resourceType)
    : openFlags(flags), resourceType(resourceType), mBackend(Q_NULLPTR),
      bDynamicBackend(true),  bDirty(false), bReadDefaults(false),
      bFileImmutable(false), bForceGlobal(false), bSuppressGlobal(false),
      configState(KConfigBase::NoAccess)
{
    static QBasicAtomicInt use_etc_kderc = Q_BASIC_ATOMIC_INITIALIZER(-1);
    if (use_etc_kderc.load() < 0) {
        use_etc_kderc.store( !qEnvironmentVariableIsSet("KDE_SKIP_KDERC"));    // for unit tests
    }
    if (use_etc_kderc.load()) {

        etc_kderc =
#ifdef Q_OS_WIN
            QFile::decodeName(qgetenv("WINDIR") + "/kde5rc");
#else
            QStringLiteral("/etc/kde5rc");
#endif
        if (!QFileInfo(etc_kderc).isReadable()) {
            etc_kderc.clear();
        }
    }

//    if (!mappingsRegistered) {
//        KEntryMap tmp;
//        if (!etc_kderc.isEmpty()) {
//            QExplicitlySharedDataPointer<KConfigBackend> backend = KConfigBackend::create(etc_kderc, QLatin1String("INI"));
//            backend->parseConfig( "en_US", tmp, KConfigBackend::ParseDefaults);
//        }
//        const QString kde5rc(QDir::home().filePath(".kde5rc"));
//        if (KStandardDirs::checkAccess(kde5rc, R_OK)) {
//            QExplicitlySharedDataPointer<KConfigBackend> backend = KConfigBackend::create(kde5rc, QLatin1String("INI"));
//            backend->parseConfig( "en_US", tmp, KConfigBackend::ParseOptions());
//        }
//        KConfigBackend::registerMappings(tmp);
//        mappingsRegistered = true;
//    }

    setLocale(QLocale().name());
}

static qint64 getticks()
{
#if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0)
    clockid_t clockId;

#ifndef _POSIX_THREAD_CPUTIME
    clockId = CLOCK_REALTIME;
#elif (_POSIX_THREAD_CPUTIME-0 <= 0)
    // if we don't have CLOCK_THREAD_CPUTIME_ID, we have to just use elapsed realtime instead
    clockId = CLOCK_REALTIME;

#  if (_POSIX_THREAD_CPUTIME-0 == 0)
    // detect availablility of CLOCK_THREAD_CPUTIME_ID
    static QBasicAtomicInt sUseThreadCpuTime = Q_BASIC_ATOMIC_INITIALIZER(-2);
    int useThreadCpuTime = sUseThreadCpuTime.load();
    if (useThreadCpuTime == -2) {
        // sysconf() will return either -1L or _POSIX_VERSION
        // (don't care about sysconf's exact return value)
        useThreadCpuTime = sysconf(_SC_THREAD_CPUTIME) == -1L ? -1 : 0 ;
        sUseThreadCpuTime.store(useThreadCpuTime); // might happen multiple times, but doesn't matter
    }
    if (useThreadCpuTime != -1)
        clockId = CLOCK_THREAD_CPUTIME_ID;
#  endif
#else
    clockId = CLOCK_THREAD_CPUTIME_ID;
#endif

    struct timespec ts;
    if (clock_gettime(clockId, &ts) == -1)
        return 0;
    return (ts.tv_sec * 1000000000) + ts.tv_nsec;
#else

    // no clock_gettime(), fall back to wall time
    struct timeval tv;
    gettimeofday(&tv, 0);
    return (tv.tv_sec * 1000000) + tv.tv_usec;
#endif
}

void QVariantAnimationPrivate::setCurrentValueForProgress(const qreal progress)
{
    Q_Q(QVariantAnimation);

    const qreal startProgress = currentInterval.start.first;
    const qreal endProgress = currentInterval.end.first;
    const qreal localProgress = (progress - startProgress) / (endProgress - startProgress);

    QVariant ret = q->interpolated(currentInterval.start.second,
                                   currentInterval.end.second,
                                   localProgress);
    qSwap(currentValue, ret);
    q->updateCurrentValue(currentValue);
    static QBasicAtomicInt changedSignalIndex = Q_BASIC_ATOMIC_INITIALIZER(0);
    if (!changedSignalIndex) {
        //we keep the mask so that we emit valueChanged only when needed (for performance reasons)
        changedSignalIndex.testAndSetRelaxed(0, signalIndex("valueChanged(QVariant)"));
    }
    if (isSignalConnected(changedSignalIndex) && currentValue != ret) {
        //the value has changed
        emit q->valueChanged(currentValue);
    }
}

QT_BEGIN_NAMESPACE

static void resolveLibrary()
{
    static QBasicAtomicInt triedResolve = Q_BASIC_ATOMIC_INITIALIZER(false);

    if (!triedResolve.loadAcquire()) {
#ifndef QT_NO_THREAD
        QMutexLocker locker(QMutexPool::globalInstanceGet(&local_WlanOpenHandle));
#endif

        if (!triedResolve.load()) {
            local_WlanOpenHandle = (WlanOpenHandleProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanOpenHandle");
            local_WlanRegisterNotification = (WlanRegisterNotificationProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanRegisterNotification");
            local_WlanEnumInterfaces = (WlanEnumInterfacesProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanEnumInterfaces");
            local_WlanGetAvailableNetworkList = (WlanGetAvailableNetworkListProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanGetAvailableNetworkList");
            local_WlanQueryInterface = (WlanQueryInterfaceProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanQueryInterface");
            local_WlanConnect = (WlanConnectProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanConnect");
            local_WlanDisconnect = (WlanDisconnectProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanDisconnect");
            local_WlanScan = (WlanScanProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanScan");
            local_WlanFreeMemory = (WlanFreeMemoryProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanFreeMemory");
            local_WlanCloseHandle = (WlanCloseHandleProto)
                QLibrary::resolve(QLatin1String("wlanapi.dll"), "WlanCloseHandle");

            triedResolve.storeRelease(true);
        }
    }
}

    QNetworkAccessBackendFactoryData() : mutex(QMutex::Recursive)
    {
        valid.ref();
    }
    ~QNetworkAccessBackendFactoryData()
    {
        QMutexLocker locker(&mutex); // why do we need to lock?
        valid.deref();
    }

    QMutex mutex;
    //this is used to avoid (re)constructing factory data from destructors of other global classes
    static QBasicAtomicInt valid;
};
Q_GLOBAL_STATIC(QNetworkAccessBackendFactoryData, factoryData)
QBasicAtomicInt QNetworkAccessBackendFactoryData::valid = Q_BASIC_ATOMIC_INITIALIZER(0);

QNetworkAccessBackendFactory::QNetworkAccessBackendFactory()
{
    QMutexLocker locker(&factoryData()->mutex);
    factoryData()->append(this);
}

QNetworkAccessBackendFactory::~QNetworkAccessBackendFactory()
{
    if (QNetworkAccessBackendFactoryData::valid.load()) {
        QMutexLocker locker(&factoryData()->mutex);
        factoryData()->removeAll(this);
    }
}

 * return -1 / EWOULDBLOCK, in which case we have to start over. And even if we
 * are woken up directly by a FUTEX_WAKE, we need to acquire the mutex, so we
 * start over again.
 *
 * UNLOCKING (non-recursive):
 *
 * To unlock, we need to set a value of 0x0 to indicate it's unlocked. The
 * first attempt is a testAndSetRelease operation from 0x1 to 0x0. If that
 * succeeds, we're done.
 *
 * If it fails, unlockInternal() is called. The only possibility is that the
 * mutex value was 0x3, which indicates some other thread is waiting or was
 * waiting in the past. We then set the mutex to 0x0 and perform a FUTEX_WAKE.
 */

static QBasicAtomicInt futexFlagSupport = Q_BASIC_ATOMIC_INITIALIZER(-1);

static int checkFutexPrivateSupport()
{
    int value = 0;
#if defined(FUTEX_PRIVATE_FLAG)
    // check if the kernel supports extra futex flags
    // FUTEX_PRIVATE_FLAG appeared in v2.6.22
    Q_STATIC_ASSERT(FUTEX_PRIVATE_FLAG != 0x80000000);

    // try an operation that has no side-effects: wake up 42 threads
    // futex will return -1 (errno==ENOSYS) if the flag isn't supported
    // there should be no other error conditions
    value = syscall(__NR_futex, &futexFlagSupport,
                    FUTEX_WAKE | FUTEX_PRIVATE_FLAG,
                    42, 0, 0, 0);