Introduce QSocketNotifier::activate(QSocketDescriptor, QSN::Type)

The pre-existing overload passes an int, but this can mean the
descriptor gets truncated in compilations where the descriptor
is 64-bit.

The old overload with int is visible when querying the metaobject system
so string-based connects still work as before, and connecting to it will
produce a deprecation warning in the output.
At the same time the PMF-based connect will, on recompile, pick the
QSocketDescriptor overload. As an added improvement it also comes with
the notification type, removing the need for separate slots where the
code would be mostly shared anyway.

The QSocketDescriptor type can be implicitly converted to and from
qintptr to ensure existing code still compiles. It can also be
constructed from Qt::HANDLE on Windows.

In this same patch I also update the existing string-based connects in
this module, which then includes updating the parameters for some slots
as well.

[ChangeLog][QtCore][QSocketNotifier] Added
QSocketNotifier::activated(QSocketDescriptor, QSocketNotifier::Type).
This replaces the activated(int) signal which in 64-bit environments
could truncate the socket descriptor. If you use "activated" with the
string-based connect() then you need to update the parameter type of the
signal and slot if it had one. If you use it with the pointer to member
function based connect() then all you need to do is update your slot's
parameter type if it has one. If you need to compile your source code
with multiple versions of Qt then connect() to this function using
pointer to member function and update the slot's parameter type if
needed.

Task-number: QTBUG-70441
Change-Id: Ic43d6bc4c5bcb4040867b2ffad8d36fb01eed8af
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

18 files changed, 234 insertions, 38 deletions

diff --git a/src/corelib/io/qfilesystemwatcher_inotify.cpp b/src/corelib/io/qfilesystemwatcher_inotify.cpp
index 888af998a5..94d9d06bcb 100644
--- a/src/corelib/io/qfilesystemwatcher_inotify.cpp
+++ b/src/corelib/io/qfilesystemwatcher_inotify.cpp
@@ -253,7 +253,7 @@ QInotifyFileSystemWatcherEngine::QInotifyFileSystemWatcherEngine(int fd, QObject
       notifier(fd, QSocketNotifier::Read, this)
 {
     fcntl(inotifyFd, F_SETFD, FD_CLOEXEC);
-    connect(&notifier, SIGNAL(activated(int)), SLOT(readFromInotify()));
+    connect(&notifier, SIGNAL(activated(QSocketDescriptor)), SLOT(readFromInotify()));
 }
 
 QInotifyFileSystemWatcherEngine::~QInotifyFileSystemWatcherEngine()
diff --git a/src/corelib/io/qfilesystemwatcher_kqueue.cpp b/src/corelib/io/qfilesystemwatcher_kqueue.cpp
index c2028e3641..06383a103a 100644
--- a/src/corelib/io/qfilesystemwatcher_kqueue.cpp
+++ b/src/corelib/io/qfilesystemwatcher_kqueue.cpp
@@ -77,7 +77,7 @@ QKqueueFileSystemWatcherEngine::QKqueueFileSystemWatcherEngine(int kqfd, QObject
       kqfd(kqfd),
       notifier(kqfd, QSocketNotifier::Read, this)
 {
-    connect(&notifier, SIGNAL(activated(int)), SLOT(readFromKqueue()));
+    connect(&notifier, SIGNAL(activated(QSocketDescriptor)), SLOT(readFromKqueue()));
 
     fcntl(kqfd, F_SETFD, FD_CLOEXEC);
 }
diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 930007ff04..e8efe6481f 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -251,7 +251,7 @@ bool QProcessPrivate::openChannel(Channel &channel)
                 channel.notifier = new QSocketNotifier(channel.pipe[1],
                                                        QSocketNotifier::Write, q);
                 channel.notifier->setEnabled(false);
-                QObject::connect(channel.notifier, SIGNAL(activated(int)),
+                QObject::connect(channel.notifier, SIGNAL(activated(QSocketDescriptor)),
                                  q, SLOT(_q_canWrite()));
             } else {
                 channel.notifier = new QSocketNotifier(channel.pipe[0],
@@ -261,7 +261,7 @@ bool QProcessPrivate::openChannel(Channel &channel)
                     receiver = SLOT(_q_canReadStandardOutput());
                 else
                     receiver = SLOT(_q_canReadStandardError());
-                QObject::connect(channel.notifier, SIGNAL(activated(int)),
+                QObject::connect(channel.notifier, SIGNAL(activated(QSocketDescriptor)),
                                  q, receiver);
             }
         }
@@ -380,7 +380,7 @@ void QProcessPrivate::startProcess()
     if (threadData.loadRelaxed()->hasEventDispatcher()) {
         startupSocketNotifier = new QSocketNotifier(childStartedPipe[0],
                                                     QSocketNotifier::Read, q);
-        QObject::connect(startupSocketNotifier, SIGNAL(activated(int)),
+        QObject::connect(startupSocketNotifier, SIGNAL(activated(QSocketDescriptor)),
                          q, SLOT(_q_startupNotification()));
     }
 
@@ -531,7 +531,7 @@ void QProcessPrivate::startProcess()
 
     if (threadData.loadRelaxed()->eventDispatcher.loadAcquire()) {
         deathNotifier = new QSocketNotifier(forkfd, QSocketNotifier::Read, q);
-        QObject::connect(deathNotifier, SIGNAL(activated(int)),
+        QObject::connect(deathNotifier, SIGNAL(activated(QSocketDescriptor)),
                          q, SLOT(_q_processDied()));
     }
 }
diff --git a/src/corelib/kernel/qsocketnotifier.cpp b/src/corelib/kernel/qsocketnotifier.cpp
index 78269ee605..6c032d13ae 100644
--- a/src/corelib/kernel/qsocketnotifier.cpp
+++ b/src/corelib/kernel/qsocketnotifier.cpp
@@ -37,23 +37,32 @@
 **
 ****************************************************************************/
 
+#define BUILDING_QSOCKETNOTIFIER
 #include "qsocketnotifier.h"
+#undef BUILDING_QSOCKETNOTIFIER
 
 #include "qplatformdefs.h"
 
 #include "qabstracteventdispatcher.h"
 #include "qcoreapplication.h"
 
+#include "qmetatype.h"
+
 #include "qobject_p.h"
 #include <private/qthread_p.h>
 
+#include <QtCore/QLoggingCategory>
+
 QT_BEGIN_NAMESPACE
 
+Q_DECLARE_LOGGING_CATEGORY(lcSocketNotifierDeprecation)
+Q_LOGGING_CATEGORY(lcSocketNotifierDeprecation, "qt.core.socketnotifier_deprecation");
+
 class QSocketNotifierPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QSocketNotifier)
 public:
-    qintptr sockfd;
+    QSocketDescriptor sockfd;
     QSocketNotifier::Type sntype;
     bool snenabled;
 };
@@ -143,13 +152,17 @@ QSocketNotifier::QSocketNotifier(qintptr socket, Type type, QObject *parent)
     : QObject(*new QSocketNotifierPrivate, parent)
 {
     Q_D(QSocketNotifier);
+
+    qRegisterMetaType<QSocketDescriptor>();
+    qRegisterMetaType<QSocketNotifier::Type>();
+
     d->sockfd = socket;
     d->sntype = type;
     d->snenabled = true;
 
     auto thisThreadData = d->threadData.loadRelaxed();
 
-    if (socket < 0)
+    if (!d->sockfd.isValid())
         qWarning("QSocketNotifier: Invalid socket specified");
     else if (!thisThreadData->hasEventDispatcher())
         qWarning("QSocketNotifier: Can only be used with threads started with QThread");
@@ -169,6 +182,11 @@ QSocketNotifier::~QSocketNotifier()
 
 /*!
     \fn void QSocketNotifier::activated(int socket)
+    \obsolete To avoid unintended truncation of the descriptor, use
+    the QSocketDescriptor overload of this function. If you need
+    compatibility with versions older than 5.15 you need to change
+    the slot to accept qintptr if it currently accepts an int, and
+    then connect using Functor-Based Connection.
 
     This signal is emitted whenever the socket notifier is enabled and
     a socket event corresponding to its \l {Type}{type} occurs.
@@ -178,6 +196,18 @@ QSocketNotifier::~QSocketNotifier()
     \sa type(), socket()
 */
 
+/*!
+    \fn void QSocketNotifier::activated(QSocketDescriptor socket, QSocketNotifier::Type type)
+    \since 5.15
+
+    This signal is emitted whenever the socket notifier is enabled and
+    a socket event corresponding to its \a type occurs.
+
+    The socket identifier is passed in the \a socket parameter.
+
+    \sa type(), socket()
+*/
+
 
 /*!
     Returns the socket identifier specified to the constructor.
@@ -187,7 +217,7 @@ QSocketNotifier::~QSocketNotifier()
 qintptr QSocketNotifier::socket() const
 {
     Q_D(const QSocketNotifier);
-    return d->sockfd;
+    return qintptr(d->sockfd);
 }
 
 /*!
@@ -230,7 +260,7 @@ bool QSocketNotifier::isEnabled() const
 void QSocketNotifier::setEnabled(bool enable)
 {
     Q_D(QSocketNotifier);
-    if (d->sockfd < 0)
+    if (!d->sockfd.isValid())
         return;
     if (d->snenabled == enable)                        // no change
         return;
@@ -268,12 +298,57 @@ bool QSocketNotifier::event(QEvent *e)
     }
     QObject::event(e);                        // will activate filters
     if ((e->type() == QEvent::SockAct) || (e->type() == QEvent::SockClose)) {
-        emit activated(d->sockfd, QPrivateSignal());
+        QPointer<QSocketNotifier> alive(this);
+        emit activated(d->sockfd, d->sntype, QPrivateSignal());
+        // ### Qt7: Remove emission if the activated(int) signal is removed
+        if (alive)
+            emit activated(int(qintptr(d->sockfd)), QPrivateSignal());
+
         return true;
     }
     return false;
 }
 
+/*!
+    \class QSocketDescriptor
+    \inmodule QtCore
+    \brief A class which holds a native socket descriptor.
+
+    \ingroup network
+    \ingroup io
+
+    \since 5.15
+
+    QSocketDescriptor makes it easier to handle native socket
+    descriptors in cross-platform code.
+
+    On Windows it holds a \c {Qt::HANDLE} and on Unix it holds an \c int.
+    The class will implicitly convert between the class and the
+    native descriptor type.
+*/
+
+/*!
+    \fn QSocketDescriptor::QSocketDescriptor(DescriptorType descriptor)
+
+    Construct a QSocketDescriptor from a native socket \a descriptor.
+*/
+
+/*!
+    \fn QSocketDescriptor::QSocketDescriptor(qintptr descriptor)
+
+    Construct a QSocketDescriptor from a native socket \a descriptor.
+
+    \note This constructor is only available on Windows.
+*/
+
+/*!
+    \fn Qt::HANDLE QSocketDescriptor::winHandle() const noexcept
+
+    Returns the internal handle.
+
+    \note This function is only available on Windows.
+*/
+
 QT_END_NAMESPACE
 
 #include "moc_qsocketnotifier.cpp"
diff --git a/src/corelib/kernel/qsocketnotifier.h b/src/corelib/kernel/qsocketnotifier.h
index 38e5f27247..808931e04b 100644
--- a/src/corelib/kernel/qsocketnotifier.h
+++ b/src/corelib/kernel/qsocketnotifier.h
@@ -44,6 +44,7 @@
 
 QT_BEGIN_NAMESPACE
 
+class QSocketDescriptor;
 class QSocketNotifierPrivate;
 class Q_CORE_EXPORT QSocketNotifier : public QObject
 {
@@ -65,7 +66,23 @@ public Q_SLOTS:
     void setEnabled(bool);
 
 Q_SIGNALS:
+#if defined(Q_MOC_RUN)
+    // Add default arguments during Q_MOC_RUN which makes moc generate "signals" which takes less
+    // parameters, but we won't actually allow emitting without all 3. This lets users use the
+    // string-based connect without specifying QSocketNotifier::Type as one of the parameters.
+    void activated(QSocketDescriptor socket, QSocketNotifier::Type activationEvent = Read,
+                   QPrivateSignal = {});
+#else
+    void activated(QSocketDescriptor socket, QSocketNotifier::Type activationEvent, QPrivateSignal);
+#endif
+
+    // ### Qt7: consider removing it.
+    // The old signal is compiled internally, but hidden outside of this class.
+    // This means the PMF-based connect(..) will automatically, on recompile, pick up the new
+    // version while the old-style connect(..) can query the metaobject system for this version.
+#if defined(Q_MOC_RUN) || defined(BUILDING_QSOCKETNOTIFIER) || defined(Q_QDOC)
     void activated(int socket, QPrivateSignal);
+#endif
 
 protected:
     bool event(QEvent *) override;
@@ -74,6 +91,50 @@ private:
     Q_DISABLE_COPY(QSocketNotifier)
 };
 
+class QSocketDescriptor
+{
+public:
+#if defined(Q_OS_WIN)
+    using DescriptorType = Qt::HANDLE;
+#define Q_DECL_CONSTEXPR_NOT_WIN
+#else
+    using DescriptorType = int;
+#define Q_DECL_CONSTEXPR_NOT_WIN Q_DECL_CONSTEXPR
+#endif
+
+    /* implicit */ Q_DECL_CONSTEXPR_NOT_WIN
+    QSocketDescriptor(DescriptorType descriptor = DescriptorType(-1)) noexcept : sockfd(descriptor)
+    {
+    }
+
+#if defined(Q_OS_WIN) || defined(Q_QDOC)
+    /* implicit */ QSocketDescriptor(qintptr desc) noexcept : sockfd(DescriptorType(desc)) {}
+    operator qintptr() const noexcept { return qintptr(sockfd); }
+    Q_DECL_CONSTEXPR Qt::HANDLE winHandle() const noexcept { return sockfd; }
+#endif
+    Q_DECL_CONSTEXPR operator DescriptorType() const noexcept { return sockfd; }
+
+    Q_DECL_CONSTEXPR_NOT_WIN bool isValid() const noexcept { return *this != QSocketDescriptor(); }
+
+    friend Q_DECL_CONSTEXPR_NOT_WIN bool operator==(QSocketDescriptor lhs,
+                                                    QSocketDescriptor rhs) noexcept
+    {
+        return lhs.sockfd == rhs.sockfd;
+    }
+    friend Q_DECL_CONSTEXPR_NOT_WIN bool operator!=(QSocketDescriptor lhs,
+                                                    QSocketDescriptor rhs) noexcept
+    {
+        return lhs.sockfd != rhs.sockfd;
+    }
+
+#undef Q_DECL_CONSTEXPR_NOT_WIN
+
+private:
+    DescriptorType sockfd;
+};
+
 QT_END_NAMESPACE
+Q_DECLARE_METATYPE(QSocketNotifier::Type)
+Q_DECLARE_METATYPE(QSocketDescriptor)
 
 #endif // QSOCKETNOTIFIER_H
diff --git a/src/dbus/qdbusconnection_p.h b/src/dbus/qdbusconnection_p.h
index da67a6c5d4..9bedbcc3a5 100644
--- a/src/dbus/qdbusconnection_p.h
+++ b/src/dbus/qdbusconnection_p.h
@@ -173,7 +173,7 @@ public:
 
 public:
     // typedefs
-    typedef QMultiHash<int, Watcher> WatcherHash;
+    typedef QMultiHash<qintptr, Watcher> WatcherHash;
     typedef QHash<int, DBusTimeout *> TimeoutHash;
     typedef QVector<QDBusMessage> PendingMessageList;
 
@@ -283,8 +283,8 @@ public slots:
     // public slots
     void setDispatchEnabled(bool enable);
     void doDispatch();
-    void socketRead(int);
-    void socketWrite(int);
+    void socketRead(qintptr);
+    void socketWrite(qintptr);
     void objectDestroyed(QObject *o);
     void relaySignal(QObject *obj, const QMetaObject *, int signalId, const QVariantList &args);
     bool addSignalHook(const QString &key, const SignalHook &hook);
diff --git a/src/dbus/qdbusintegrator.cpp b/src/dbus/qdbusintegrator.cpp
index 669b330f1d..b0a9342515 100644
--- a/src/dbus/qdbusintegrator.cpp
+++ b/src/dbus/qdbusintegrator.cpp
@@ -1205,7 +1205,7 @@ void QDBusConnectionPrivate::doDispatch()
     }
 }
 
-void QDBusConnectionPrivate::socketRead(int fd)
+void QDBusConnectionPrivate::socketRead(qintptr fd)
 {
     WatcherHash::ConstIterator it = watchers.constFind(fd);
     while (it != watchers.constEnd() && it.key() == fd) {
@@ -1219,7 +1219,7 @@ void QDBusConnectionPrivate::socketRead(int fd)
     doDispatch();
 }
 
-void QDBusConnectionPrivate::socketWrite(int fd)
+void QDBusConnectionPrivate::socketWrite(qintptr fd)
 {
     WatcherHash::ConstIterator it = watchers.constFind(fd);
     while (it != watchers.constEnd() && it.key() == fd) {
diff --git a/src/network/socket/qlocalserver_unix.cpp b/src/network/socket/qlocalserver_unix.cpp
index 88367d680d..c4085b440e 100644
--- a/src/network/socket/qlocalserver_unix.cpp
+++ b/src/network/socket/qlocalserver_unix.cpp
@@ -185,7 +185,7 @@ bool QLocalServerPrivate::listen(const QString &requestedServerName)
     Q_ASSERT(!socketNotifier);
     socketNotifier = new QSocketNotifier(listenSocket,
                                          QSocketNotifier::Read, q);
-    q->connect(socketNotifier, SIGNAL(activated(int)),
+    q->connect(socketNotifier, SIGNAL(activated(QSocketDescriptor)),
                q, SLOT(_q_onNewConnection()));
     socketNotifier->setEnabled(maxPendingConnections > 0);
     return true;
@@ -227,7 +227,7 @@ bool QLocalServerPrivate::listen(qintptr socketDescriptor)
     Q_ASSERT(!socketNotifier);
     socketNotifier = new QSocketNotifier(listenSocket,
                                          QSocketNotifier::Read, q);
-    q->connect(socketNotifier, SIGNAL(activated(int)),
+    q->connect(socketNotifier, SIGNAL(activated(QSocketDescriptor)),
                q, SLOT(_q_onNewConnection()));
     socketNotifier->setEnabled(maxPendingConnections > 0);
     return true;
diff --git a/src/network/socket/qlocalsocket_unix.cpp b/src/network/socket/qlocalsocket_unix.cpp
index d9b39a7752..52067a265c 100644
--- a/src/network/socket/qlocalsocket_unix.cpp
+++ b/src/network/socket/qlocalsocket_unix.cpp
@@ -308,7 +308,7 @@ void QLocalSocketPrivate::_q_connectToSocket()
             // Try again later, all of the sockets listening are full
             if (!delayConnect) {
                 delayConnect = new QSocketNotifier(connectingSocket, QSocketNotifier::Write, q);
-                q->connect(delayConnect, SIGNAL(activated(int)), q, SLOT(_q_connectToSocket()));
+                q->connect(delayConnect, SIGNAL(activated(QSocketDescriptor)), q, SLOT(_q_connectToSocket()));
             }
             if (!connectTimer) {
                 connectTimer = new QTimer(q);
diff --git a/src/platformsupport/devicediscovery/qdevicediscovery_udev.cpp b/src/platformsupport/devicediscovery/qdevicediscovery_udev.cpp
index 9cf5c9096e..118940c634 100644
--- a/src/platformsupport/devicediscovery/qdevicediscovery_udev.cpp
+++ b/src/platformsupport/devicediscovery/qdevicediscovery_udev.cpp
@@ -92,7 +92,7 @@ QDeviceDiscoveryUDev::QDeviceDiscoveryUDev(QDeviceTypes types, struct udev *udev
     m_udevMonitorFileDescriptor = udev_monitor_get_fd(m_udevMonitor);
 
     m_udevSocketNotifier = new QSocketNotifier(m_udevMonitorFileDescriptor, QSocketNotifier::Read, this);
-    connect(m_udevSocketNotifier, SIGNAL(activated(int)), this, SLOT(handleUDevNotification()));
+    connect(m_udevSocketNotifier, SIGNAL(activated(QSocketDescriptor)), this, SLOT(handleUDevNotification()));
 }
 
 QDeviceDiscoveryUDev::~QDeviceDiscoveryUDev()
diff --git a/src/plugins/platforms/openwfd/qopenwfddevice.cpp b/src/plugins/platforms/openwfd/qopenwfddevice.cpp
index 7a9d22e74d..99896151b2 100644
--- a/src/plugins/platforms/openwfd/qopenwfddevice.cpp
+++ b/src/plugins/platforms/openwfd/qopenwfddevice.cpp
@@ -83,7 +83,7 @@ QOpenWFDDevice::QOpenWFDDevice(QOpenWFDIntegration *integration, WFDint device_e
 
     int fd = wfdDeviceEventGetFD(mDevice,mEvent);
     mEventSocketNotifier = new QSocketNotifier(fd,QSocketNotifier::Read,this);
-    connect(mEventSocketNotifier,SIGNAL(activated(int)),SLOT(readEvents()));
+    connect(mEventSocketNotifier,SIGNAL(activated(QSocketDescriptor)),SLOT(readEvents()));
 
     mCommitedDevice = true;
     commit(WFD_COMMIT_ENTIRE_DEVICE, handle());
diff --git a/src/plugins/platforms/qnx/qqnxbuttoneventnotifier.cpp b/src/plugins/platforms/qnx/qqnxbuttoneventnotifier.cpp
index a6236f2376..f0c4c385ef 100644
--- a/src/plugins/platforms/qnx/qqnxbuttoneventnotifier.cpp
+++ b/src/plugins/platforms/qnx/qqnxbuttoneventnotifier.cpp
@@ -96,7 +96,7 @@ void QQnxButtonEventNotifier::start()
     }
 
     m_readNotifier = new QSocketNotifier(m_fd, QSocketNotifier::Read);
-    QObject::connect(m_readNotifier, SIGNAL(activated(int)), this, SLOT(updateButtonStates()));
+    QObject::connect(m_readNotifier, SIGNAL(activated(QSocketDescriptor)), this, SLOT(updateButtonStates()));
 
     qButtonDebug("successfully connected to Navigator. fd = %d", m_fd);
 }
diff --git a/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp b/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp
index 1f630863b7..f7e8e7966c 100644
--- a/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp
+++ b/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp
@@ -96,7 +96,7 @@ void QQnxNavigatorEventNotifier::start()
     }
 
     m_readNotifier = new QSocketNotifier(m_fd, QSocketNotifier::Read);
-    connect(m_readNotifier, SIGNAL(activated(int)), this, SLOT(readData()));
+    connect(m_readNotifier, SIGNAL(activated(QSocketDescriptor)), this, SLOT(readData()));
 }
 
 void QQnxNavigatorEventNotifier::parsePPS(const QByteArray &ppsData, QByteArray &msg, QByteArray &dat, QByteArray &id)
diff --git a/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp b/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp
index 025c03c058..6f496571fa 100644
--- a/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp
+++ b/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp
@@ -143,7 +143,7 @@ bool QQnxVirtualKeyboardPps::connect()
         return false;
 
     m_readNotifier = new QSocketNotifier(m_fd, QSocketNotifier::Read);
-    QObject::connect(m_readNotifier, SIGNAL(activated(int)), this, SLOT(ppsDataReady()));
+    QObject::connect(m_readNotifier, SIGNAL(activated(QSocketDescriptor)), this, SLOT(ppsDataReady()));
 
     return true;
 }
diff --git a/src/plugins/platforms/xcb/qxcbsessionmanager.cpp b/src/plugins/platforms/xcb/qxcbsessionmanager.cpp
index 2eb32c069e..e9697f505b 100644
--- a/src/plugins/platforms/xcb/qxcbsessionmanager.cpp
+++ b/src/plugins/platforms/xcb/qxcbsessionmanager.cpp
@@ -61,11 +61,11 @@ public:
     QSmSocketReceiver(int socket)
     {
         QSocketNotifier* sn = new QSocketNotifier(socket, QSocketNotifier::Read, this);
-        connect(sn, SIGNAL(activated(int)), this, SLOT(socketActivated(int)));
+        connect(sn, SIGNAL(activated(QSocketDescriptor)), this, SLOT(socketActivated()));
     }
 
 public Q_SLOTS:
-     void socketActivated(int);
+     void socketActivated();
 };
 
 
@@ -327,7 +327,7 @@ static void sm_saveYourselfPhase2Callback(SmcConn smcConn, SmPointer clientData)
 }
 
 
-void QSmSocketReceiver::socketActivated(int)
+void QSmSocketReceiver::socketActivated()
 {
     IceProcessMessages(SmcGetIceConnection(smcConnection), nullptr, nullptr);
 }
diff --git a/src/plugins/sqldrivers/psql/qsql_psql.cpp b/src/plugins/sqldrivers/psql/qsql_psql.cpp
index 38bf355856..c5895f281d 100644
--- a/src/plugins/sqldrivers/psql/qsql_psql.cpp
+++ b/src/plugins/sqldrivers/psql/qsql_psql.cpp
@@ -279,7 +279,7 @@ void QPSQLDriverPrivate::checkPendingNotifications() const
     Q_Q(const QPSQLDriver);
     if (seid.size() && !pendingNotifyCheck) {
         pendingNotifyCheck = true;
-        QMetaObject::invokeMethod(const_cast<QPSQLDriver*>(q), "_q_handleNotification", Qt::QueuedConnection, Q_ARG(int,0));
+        QMetaObject::invokeMethod(const_cast<QPSQLDriver*>(q), "_q_handleNotification", Qt::QueuedConnection);
     }
 }
 
@@ -1246,7 +1246,7 @@ void QPSQLDriver::close()
 
         d->seid.clear();
         if (d->sn) {
-            disconnect(d->sn, SIGNAL(activated(int)), this, SLOT(_q_handleNotification(int)));
+            disconnect(d->sn, SIGNAL(activated(QSocketDescriptor)), this, SLOT(_q_handleNotification()));
             delete d->sn;
             d->sn = nullptr;
         }
@@ -1603,7 +1603,7 @@ bool QPSQLDriver::subscribeToNotification(const QString &name)
 
         if (!d->sn) {
             d->sn = new QSocketNotifier(socket, QSocketNotifier::Read);
-            connect(d->sn, SIGNAL(activated(int)), this, SLOT(_q_handleNotification(int)));
+            connect(d->sn, SIGNAL(activated(QSocketDescriptor)), this, SLOT(_q_handleNotification()));
         }
     } else {
         qWarning("QPSQLDriver::subscribeToNotificationImplementation: PQsocket didn't return a valid socket to listen on");
@@ -1639,7 +1639,7 @@ bool QPSQLDriver::unsubscribeFromNotification(const QString &name)
     d->seid.removeAll(name);
 
     if (d->seid.isEmpty()) {
-        disconnect(d->sn, SIGNAL(activated(int)), this, SLOT(_q_handleNotification(int)));
+        disconnect(d->sn, SIGNAL(activated(QSocketDescriptor)), this, SLOT(_q_handleNotification()));
         delete d->sn;
         d->sn = nullptr;
     }
@@ -1653,7 +1653,7 @@ QStringList QPSQLDriver::subscribedToNotifications() const
     return d->seid;
 }
 
-void QPSQLDriver::_q_handleNotification(int)
+void QPSQLDriver::_q_handleNotification()
 {
     Q_D(QPSQLDriver);
     d->pendingNotifyCheck = false;
diff --git a/src/plugins/sqldrivers/psql/qsql_psql_p.h b/src/plugins/sqldrivers/psql/qsql_psql_p.h
index 9ac1fb50d7..22c0761667 100644
--- a/src/plugins/sqldrivers/psql/qsql_psql_p.h
+++ b/src/plugins/sqldrivers/psql/qsql_psql_p.h
@@ -130,7 +130,7 @@ protected:
     bool rollbackTransaction() override;
 
 private Q_SLOTS:
-    void _q_handleNotification(int);
+    void _q_handleNotification();
 };
 
 QT_END_NAMESPACE
diff --git a/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp b/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp
index e3f45df27d..8ba3505d8b 100644
--- a/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp
+++ b/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp
@@ -53,6 +53,7 @@
 #  undef min
 #endif // Q_CC_MSVC
 
+
 class tst_QSocketNotifier : public QObject
 {
     Q_OBJECT
@@ -63,6 +64,9 @@ private slots:
     void posixSockets();
 #endif
     void asyncMultipleDatagram();
+    void activationReason_data();
+    void activationReason();
+    void legacyConnect();
 
 protected slots:
     void async_readDatagramSlot();
@@ -97,10 +101,10 @@ public:
     {
         QSocketNotifier *notifier1 =
             new QSocketNotifier(readEnd1->socketDescriptor(), QSocketNotifier::Read, this);
-        connect(notifier1, SIGNAL(activated(int)), SLOT(handleActivated()));
+        connect(notifier1, SIGNAL(activated(QSocketDescriptor)), SLOT(handleActivated()));
         QSocketNotifier *notifier2 =
             new QSocketNotifier(readEnd2->socketDescriptor(), QSocketNotifier::Read, this);
-        connect(notifier2, SIGNAL(activated(int)), SLOT(handleActivated()));
+        connect(notifier2, SIGNAL(activated(QSocketDescriptor)), SLOT(handleActivated()));
     }
 
 public slots:
@@ -284,12 +288,12 @@ void tst_QSocketNotifier::posixSockets()
 
     {
         QSocketNotifier rn(posixSocket, QSocketNotifier::Read);
-        connect(&rn, SIGNAL(activated(int)), &QTestEventLoop::instance(), SLOT(exitLoop()));
+        connect(&rn, SIGNAL(activated(QSocketDescriptor)), &QTestEventLoop::instance(), SLOT(exitLoop()));
         QSignalSpy readSpy(&rn, &QSocketNotifier::activated);
         QVERIFY(readSpy.isValid());
         // No write notifier, some systems trigger write notification on socket creation, but not all
         QSocketNotifier en(posixSocket, QSocketNotifier::Exception);
-        connect(&en, SIGNAL(activated(int)), &QTestEventLoop::instance(), SLOT(exitLoop()));
+        connect(&en, SIGNAL(activated(QSocketDescriptor)), &QTestEventLoop::instance(), SLOT(exitLoop()));
         QSignalSpy errorSpy(&en, &QSocketNotifier::activated);
         QVERIFY(errorSpy.isValid());
 
@@ -306,7 +310,7 @@ void tst_QSocketNotifier::posixSockets()
         QCOMPARE(buffer, "hello");
 
         QSocketNotifier wn(posixSocket, QSocketNotifier::Write);
-        connect(&wn, SIGNAL(activated(int)), &QTestEventLoop::instance(), SLOT(exitLoop()));
+        connect(&wn, SIGNAL(activated(QSocketDescriptor)), &QTestEventLoop::instance(), SLOT(exitLoop()));
         QSignalSpy writeSpy(&wn, &QSocketNotifier::activated);
         QVERIFY(writeSpy.isValid());
         qt_safe_write(posixSocket, "goodbye", 8);
@@ -385,5 +389,61 @@ void tst_QSocketNotifier::asyncMultipleDatagram()
     #endif // !Q_OS_WINRT
 }
 
+void tst_QSocketNotifier::activationReason_data()
+{
+    QTest::addColumn<QSocketNotifier::Type>("type");
+    QTest::addRow("read") << QSocketNotifier::Read;
+    QTest::addRow("write") << QSocketNotifier::Write;
+    QTest::addRow("exception") << QSocketNotifier::Exception;
+}
+void tst_QSocketNotifier::activationReason()
+{
+    QSocketDescriptor fd = 15;
+
+    QFETCH(QSocketNotifier::Type, type);
+
+    QSocketNotifier notifier(fd, type);
+    auto activation = new QEvent(QEvent::SockAct);
+    QCoreApplication::postEvent(&notifier, activation);
+
+    QSocketNotifier::Type notifierType;
+    connect(&notifier, &QSocketNotifier::activated, this,
+            [&notifierType, fd](QSocketDescriptor sockfd, QSocketNotifier::Type sntype) {
+                if (sockfd == fd)
+                    notifierType = sntype;
+                else
+                    qWarning() << "Got an unexpected socket file descriptor:" << qintptr(sockfd);
+            });
+
+    QCoreApplication::processEvents();
+    QCOMPARE(notifierType, type);
+}
+
+// This test ensures that we can connect QSocketNotifier::activated to a slot taking an integer
+// or qintptr.
+void tst_QSocketNotifier::legacyConnect()
+{
+    qintptr fd = 15;
+    QSocketNotifier notifier(fd, QSocketNotifier::Read);
+    auto activation = new QEvent(QEvent::SockAct);
+    QCoreApplication::postEvent(&notifier, activation);
+
+    bool receivedQIntPtr = false;
+    connect(&notifier, &QSocketNotifier::activated, this, [&receivedQIntPtr, fd](qintptr q){
+        if (q == fd)
+            receivedQIntPtr = true;
+    });
+    bool receivedInt = false;
+    connect(&notifier, &QSocketNotifier::activated, this, [&receivedInt, fd](int q){
+        if (q == fd)
+            receivedInt = true;
+    });
+
+    QCoreApplication::processEvents();
+    QVERIFY(receivedQIntPtr);
+    QVERIFY(receivedInt);
+}
+
+
 QTEST_MAIN(tst_QSocketNotifier)
 #include <tst_qsocketnotifier.moc>