Pass params of shareable type by const-ref rather than by value

...where passing them by value was not intentional.

Change-Id: Ifd5036d57b41fddeeacfbd3f5890881605b80647
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

57 files changed, 82 insertions, 82 deletions

diff --git a/src/corelib/doc/snippets/qsignalmapper/buttonwidget.cpp b/src/corelib/doc/snippets/qsignalmapper/buttonwidget.cpp
index 230be1f524..067853a5f6 100644
--- a/src/corelib/doc/snippets/qsignalmapper/buttonwidget.cpp
+++ b/src/corelib/doc/snippets/qsignalmapper/buttonwidget.cpp
@@ -43,7 +43,7 @@
 #include "buttonwidget.h"
 
 //! [0]
-ButtonWidget::ButtonWidget(QStringList texts, QWidget *parent)
+ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent)
     : QWidget(parent)
 {
     signalMapper = new QSignalMapper(this);
diff --git a/src/corelib/doc/snippets/qsignalmapper/buttonwidget.h b/src/corelib/doc/snippets/qsignalmapper/buttonwidget.h
index a6939603e8..b1803cf203 100644
--- a/src/corelib/doc/snippets/qsignalmapper/buttonwidget.h
+++ b/src/corelib/doc/snippets/qsignalmapper/buttonwidget.h
@@ -53,7 +53,7 @@ class ButtonWidget : public QWidget
     Q_OBJECT
 
 public:
-    ButtonWidget(QStringList texts, QWidget *parent = 0);
+    ButtonWidget(const QStringList &texts, QWidget *parent = 0);
 
 signals:
     void clicked(const QString &text);
diff --git a/src/corelib/doc/snippets/sharedemployee/employee.h b/src/corelib/doc/snippets/sharedemployee/employee.h
index 9b673dceeb..83f630d299 100644
--- a/src/corelib/doc/snippets/sharedemployee/employee.h
+++ b/src/corelib/doc/snippets/sharedemployee/employee.h
@@ -63,7 +63,7 @@ class Employee
 //! [1]
     Employee() { d = new EmployeeData; }
 //! [1] //! [2]
-    Employee(int id, QString name) {
+    Employee(int id, const QString &name) {
         d = new EmployeeData;
         setId(id);
         setName(name);
@@ -77,7 +77,7 @@ class Employee
 //! [3]
     void setId(int id) { d->id = id; }
 //! [3] //! [4]
-    void setName(QString name) { d->name = name; }
+    void setName(const QString &name) { d->name = name; }
 //! [4]
 
 //! [5]
diff --git a/src/corelib/io/qfilesystemwatcher_fsevents.mm b/src/corelib/io/qfilesystemwatcher_fsevents.mm
index 1dc45a7e41..1076b8f5b4 100644
--- a/src/corelib/io/qfilesystemwatcher_fsevents.mm
+++ b/src/corelib/io/qfilesystemwatcher_fsevents.mm
@@ -283,13 +283,13 @@ void QFseventsFileSystemWatcherEngine::processEvent(ConstFSEventStreamRef stream
 #endif
 }
 
-void QFseventsFileSystemWatcherEngine::doEmitFileChanged(const QString path, bool removed)
+void QFseventsFileSystemWatcherEngine::doEmitFileChanged(const QString &path, bool removed)
 {
     DEBUG() << "emitting fileChanged for" << path << "with removed =" << removed;
     emit fileChanged(path, removed);
 }
 
-void QFseventsFileSystemWatcherEngine::doEmitDirectoryChanged(const QString path, bool removed)
+void QFseventsFileSystemWatcherEngine::doEmitDirectoryChanged(const QString &path, bool removed)
 {
     DEBUG() << "emitting directoryChanged for" << path << "with removed =" << removed;
     emit directoryChanged(path, removed);
@@ -316,10 +316,10 @@ QFseventsFileSystemWatcherEngine::QFseventsFileSystemWatcherEngine(QObject *pare
 
     // We cannot use signal-to-signal queued connections, because the
     // QSignalSpy cannot spot signals fired from other/alien threads.
-    connect(this, SIGNAL(emitDirectoryChanged(const QString, bool)),
-            this, SLOT(doEmitDirectoryChanged(const QString, bool)), Qt::QueuedConnection);
-    connect(this, SIGNAL(emitFileChanged(const QString, bool)),
-            this, SLOT(doEmitFileChanged(const QString, bool)), Qt::QueuedConnection);
+    connect(this, SIGNAL(emitDirectoryChanged(QString,bool)),
+            this, SLOT(doEmitDirectoryChanged(QString,bool)), Qt::QueuedConnection);
+    connect(this, SIGNAL(emitFileChanged(QString,bool)),
+            this, SLOT(doEmitFileChanged(QString,bool)), Qt::QueuedConnection);
     connect(this, SIGNAL(scheduleStreamRestart()),
             this, SLOT(restartStream()), Qt::QueuedConnection);
 
diff --git a/src/corelib/io/qfilesystemwatcher_fsevents_p.h b/src/corelib/io/qfilesystemwatcher_fsevents_p.h
index bd75a0aa32..b4640afc4e 100644
--- a/src/corelib/io/qfilesystemwatcher_fsevents_p.h
+++ b/src/corelib/io/qfilesystemwatcher_fsevents_p.h
@@ -74,13 +74,13 @@ public:
     void processEvent(ConstFSEventStreamRef streamRef, size_t numEvents, char **eventPaths, const FSEventStreamEventFlags eventFlags[], const FSEventStreamEventId eventIds[]);
 
 Q_SIGNALS:
-    void emitFileChanged(const QString path, bool removed);
-    void emitDirectoryChanged(const QString path, bool removed);
+    void emitFileChanged(const QString &path, bool removed);
+    void emitDirectoryChanged(const QString &path, bool removed);
     void scheduleStreamRestart();
 
 private slots:
-    void doEmitFileChanged(const QString path, bool removed);
-    void doEmitDirectoryChanged(const QString path, bool removed);
+    void doEmitFileChanged(const QString &path, bool removed);
+    void doEmitDirectoryChanged(const QString &path, bool removed);
     void restartStream();
 
 private:
diff --git a/src/corelib/io/qsettings_winrt.cpp b/src/corelib/io/qsettings_winrt.cpp
index 8f9d6d3692..bf8b157d00 100644
--- a/src/corelib/io/qsettings_winrt.cpp
+++ b/src/corelib/io/qsettings_winrt.cpp
@@ -281,7 +281,7 @@ class QWinRTSettingsPrivate : public QSettingsPrivate
 public:
     QWinRTSettingsPrivate(QSettings::Scope scope, const QString &organization,
                           const QString &application);
-    QWinRTSettingsPrivate(QString rKey);
+    QWinRTSettingsPrivate(const QString &rKey);
     ~QWinRTSettingsPrivate();
 
     void remove(const QString &uKey);
@@ -315,7 +315,7 @@ QWinRTSettingsPrivate::QWinRTSettingsPrivate(QSettings::Scope scope, const QStri
     init(scope);
 }
 
-QWinRTSettingsPrivate::QWinRTSettingsPrivate(QString rPath)
+QWinRTSettingsPrivate::QWinRTSettingsPrivate(const QString &rPath)
     : QSettingsPrivate(QSettings::NativeFormat, QSettings::UserScope, rPath, QString())
     , writeContainer(0)
 {
diff --git a/src/corelib/itemmodels/qabstractitemmodel.cpp b/src/corelib/itemmodels/qabstractitemmodel.cpp
index 213394e4b7..60ac75133c 100644
--- a/src/corelib/itemmodels/qabstractitemmodel.cpp
+++ b/src/corelib/itemmodels/qabstractitemmodel.cpp
@@ -677,7 +677,7 @@ void QAbstractItemModelPrivate::itemsAboutToBeMoved(const QModelIndex &srcParent
   column value depending on the value of \a orientation. The indexes may also be moved to a different parent if \a parent
   differs from the existing parent for the index.
 */
-void QAbstractItemModelPrivate::movePersistentIndexes(QVector<QPersistentModelIndexData *> indexes, int change, const QModelIndex &parent, Qt::Orientation orientation)
+void QAbstractItemModelPrivate::movePersistentIndexes(const QVector<QPersistentModelIndexData *> &indexes, int change, const QModelIndex &parent, Qt::Orientation orientation)
 {
     QVector<QPersistentModelIndexData *>::const_iterator it;
     const QVector<QPersistentModelIndexData *>::const_iterator begin = indexes.constBegin();
diff --git a/src/corelib/itemmodels/qabstractitemmodel_p.h b/src/corelib/itemmodels/qabstractitemmodel_p.h
index 1ff758f7ce..075e6a9018 100644
--- a/src/corelib/itemmodels/qabstractitemmodel_p.h
+++ b/src/corelib/itemmodels/qabstractitemmodel_p.h
@@ -72,7 +72,7 @@ class Q_CORE_EXPORT QAbstractItemModelPrivate : public QObjectPrivate
 public:
     QAbstractItemModelPrivate() : QObjectPrivate(), supportedDragActions(-1), roleNames(defaultRoleNames()) {}
     void removePersistentIndexData(QPersistentModelIndexData *data);
-    void movePersistentIndexes(QVector<QPersistentModelIndexData *> indexes, int change, const QModelIndex &parent, Qt::Orientation orientation);
+    void movePersistentIndexes(const QVector<QPersistentModelIndexData *> &indexes, int change, const QModelIndex &parent, Qt::Orientation orientation);
     void rowsAboutToBeInserted(const QModelIndex &parent, int first, int last);
     void rowsInserted(const QModelIndex &parent, int first, int last);
     void rowsAboutToBeRemoved(const QModelIndex &parent, int first, int last);
diff --git a/src/corelib/kernel/qsharedmemory_p.h b/src/corelib/kernel/qsharedmemory_p.h
index 8c5cf52b9f..0308dde57f 100644
--- a/src/corelib/kernel/qsharedmemory_p.h
+++ b/src/corelib/kernel/qsharedmemory_p.h
@@ -136,7 +136,7 @@ public:
     void setErrorString(const QString &function);
 
 #ifndef QT_NO_SYSTEMSEMAPHORE
-    bool tryLocker(QSharedMemoryLocker *locker, const QString function) {
+    bool tryLocker(QSharedMemoryLocker *locker, const QString &function) {
         if (!locker->lock()) {
             errorString = QSharedMemory::tr("%1: unable to lock").arg(function);
             error = QSharedMemory::LockError;
diff --git a/src/corelib/tools/qtimezoneprivate_tz.cpp b/src/corelib/tools/qtimezoneprivate_tz.cpp
index 74499bf52f..0d8ae3b47f 100644
--- a/src/corelib/tools/qtimezoneprivate_tz.cpp
+++ b/src/corelib/tools/qtimezoneprivate_tz.cpp
@@ -343,7 +343,7 @@ static QDate calculateDowDate(int year, int month, int dayOfWeek, int week)
     return date;
 }
 
-static QDate calculatePosixDate(const QByteArray dateRule, int year)
+static QDate calculatePosixDate(const QByteArray &dateRule, int year)
 {
     // Can start with M, J, or a digit
     if (dateRule.at(0) == 'M') {
diff --git a/src/gui/image/qpicture.cpp b/src/gui/image/qpicture.cpp
index 1f02520ff2..8b62183c20 100644
--- a/src/gui/image/qpicture.cpp
+++ b/src/gui/image/qpicture.cpp
@@ -1213,7 +1213,7 @@ QList<QByteArray> QPicture::inputFormats()
     return QPictureIO::inputFormats();
 }
 
-static QStringList qToStringList(const QList<QByteArray> arr)
+static QStringList qToStringList(const QList<QByteArray> &arr)
 {
     QStringList list;
     for (int i = 0; i < arr.count(); ++i)
diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index 6a98487287..77d134cb28 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -974,7 +974,7 @@ static
 unsigned int bestFoundry(int script, unsigned int score, int styleStrategy,
                          const QtFontFamily *family, const QString &foundry_name,
                          QtFontStyle::Key styleKey, int pixelSize, char pitch,
-                         QtFontDesc *desc, int force_encoding_id, QString styleName = QString())
+                         QtFontDesc *desc, int force_encoding_id, const QString &styleName = QString())
 {
     Q_UNUSED(force_encoding_id);
     Q_UNUSED(script);
diff --git a/src/network/access/qftp.cpp b/src/network/access/qftp.cpp
index badcb5b021..bb89eece4b 100644
--- a/src/network/access/qftp.cpp
+++ b/src/network/access/qftp.cpp
@@ -225,8 +225,8 @@ private:
 class QFtpCommand
 {
 public:
-    QFtpCommand(QFtp::Command cmd, QStringList raw, const QByteArray &ba);
-    QFtpCommand(QFtp::Command cmd, QStringList raw, QIODevice *dev = 0);
+    QFtpCommand(QFtp::Command cmd, const QStringList &raw, const QByteArray &ba);
+    QFtpCommand(QFtp::Command cmd, const QStringList &raw, QIODevice *dev = 0);
     ~QFtpCommand();
 
     int id;
@@ -246,14 +246,14 @@ public:
 
 QBasicAtomicInt QFtpCommand::idCounter = Q_BASIC_ATOMIC_INITIALIZER(1);
 
-QFtpCommand::QFtpCommand(QFtp::Command cmd, QStringList raw, const QByteArray &ba)
+QFtpCommand::QFtpCommand(QFtp::Command cmd, const QStringList &raw, const QByteArray &ba)
     : command(cmd), rawCmds(raw), is_ba(true)
 {
     id = idCounter.fetchAndAddRelaxed(1);
     data.ba = new QByteArray(ba);
 }
 
-QFtpCommand::QFtpCommand(QFtp::Command cmd, QStringList raw, QIODevice *dev)
+QFtpCommand::QFtpCommand(QFtp::Command cmd, const QStringList &raw, QIODevice *dev)
     : command(cmd), rawCmds(raw), is_ba(false)
 {
     id = idCounter.fetchAndAddRelaxed(1);
diff --git a/src/network/access/qnetworkcookiejar.cpp b/src/network/access/qnetworkcookiejar.cpp
index f5c97aeaae..3cefb28f68 100644
--- a/src/network/access/qnetworkcookiejar.cpp
+++ b/src/network/access/qnetworkcookiejar.cpp
@@ -130,7 +130,7 @@ void QNetworkCookieJar::setAllCookies(const QList<QNetworkCookie> &cookieList)
     d->allCookies = cookieList;
 }
 
-static inline bool isParentPath(QString path, QString reference)
+static inline bool isParentPath(const QString &path, const QString &reference)
 {
     if (path.startsWith(reference)) {
         //The cookie-path and the request-path are identical.
@@ -149,7 +149,7 @@ static inline bool isParentPath(QString path, QString reference)
     return false;
 }
 
-static inline bool isParentDomain(QString domain, QString reference)
+static inline bool isParentDomain(const QString &domain, const QString &reference)
 {
     if (!reference.startsWith(QLatin1Char('.')))
         return domain == reference;
diff --git a/src/network/kernel/qhostinfo.cpp b/src/network/kernel/qhostinfo.cpp
index 2912c6fef3..d2dc7c4850 100644
--- a/src/network/kernel/qhostinfo.cpp
+++ b/src/network/kernel/qhostinfo.cpp
@@ -431,7 +431,7 @@ void QHostInfo::setErrorString(const QString &str)
     \sa hostName()
 */
 
-QHostInfoRunnable::QHostInfoRunnable(QString hn, int i) : toBeLookedUp(hn), id(i)
+QHostInfoRunnable::QHostInfoRunnable(const QString &hn, int i) : toBeLookedUp(hn), id(i)
 {
     setAutoDelete(true);
 }
diff --git a/src/network/kernel/qhostinfo_p.h b/src/network/kernel/qhostinfo_p.h
index 5400b18b37..74cfe2a9aa 100644
--- a/src/network/kernel/qhostinfo_p.h
+++ b/src/network/kernel/qhostinfo_p.h
@@ -145,7 +145,7 @@ private:
 class QHostInfoRunnable : public QRunnable
 {
 public:
-    QHostInfoRunnable (QString hn, int i);
+    QHostInfoRunnable(const QString &hn, int i);
     void run() Q_DECL_OVERRIDE;
 
     QString toBeLookedUp;
diff --git a/src/network/socket/qsocks5socketengine.cpp b/src/network/socket/qsocks5socketengine.cpp
index 2a23642f26..bdeee4195c 100644
--- a/src/network/socket/qsocks5socketengine.cpp
+++ b/src/network/socket/qsocks5socketengine.cpp
@@ -438,13 +438,13 @@ bool QSocks5Authenticator::continueAuthenticate(QTcpSocket *socket, bool *comple
     return true;
 }
 
-bool QSocks5Authenticator::seal(const QByteArray buf, QByteArray *sealedBuf)
+bool QSocks5Authenticator::seal(const QByteArray &buf, QByteArray *sealedBuf)
 {
     *sealedBuf = buf;
     return true;
 }
 
-bool QSocks5Authenticator::unSeal(const QByteArray sealedBuf, QByteArray *buf)
+bool QSocks5Authenticator::unSeal(const QByteArray &sealedBuf, QByteArray *buf)
 {
     *buf = sealedBuf;
     return true;
diff --git a/src/network/socket/qsocks5socketengine_p.h b/src/network/socket/qsocks5socketengine_p.h
index 185d973e06..c97b0e89ce 100644
--- a/src/network/socket/qsocks5socketengine_p.h
+++ b/src/network/socket/qsocks5socketengine_p.h
@@ -149,8 +149,8 @@ public:
     virtual bool beginAuthenticate(QTcpSocket *socket, bool *completed);
     virtual bool continueAuthenticate(QTcpSocket *socket, bool *completed);
 
-    virtual bool seal(const QByteArray buf, QByteArray *sealedBuf);
-    virtual bool unSeal(const QByteArray sealedBuf, QByteArray *buf);
+    virtual bool seal(const QByteArray &buf, QByteArray *sealedBuf);
+    virtual bool unSeal(const QByteArray &sealedBuf, QByteArray *buf);
     virtual bool unSeal(QTcpSocket *sealedSocket, QByteArray *buf);
 
     virtual QString errorString() { return QString(); }
diff --git a/src/platformsupport/services/genericunix/qgenericunixservices.cpp b/src/platformsupport/services/genericunix/qgenericunixservices.cpp
index 99ca855a28..b59ae431f4 100644
--- a/src/platformsupport/services/genericunix/qgenericunixservices.cpp
+++ b/src/platformsupport/services/genericunix/qgenericunixservices.cpp
@@ -72,7 +72,7 @@ static inline bool checkExecutable(const QString &candidate, QString *result)
     return !result->isEmpty();
 }
 
-static inline bool detectWebBrowser(QByteArray desktop,
+static inline bool detectWebBrowser(const QByteArray &desktop,
                                     bool checkBrowserVariable,
                                     QString *browser)
 {
diff --git a/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp b/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp
index f8ced57553..3fffec0dfd 100644
--- a/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp
+++ b/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp
@@ -565,7 +565,7 @@ class QGnomeThemePrivate : public QPlatformThemePrivate
 {
 public:
     QGnomeThemePrivate() : fontsConfigured(false) { }
-    void configureFonts(QString gtkFontName) const
+    void configureFonts(const QString &gtkFontName) const
     {
         Q_ASSERT(!fontsConfigured);
         const int split = gtkFontName.lastIndexOf(QChar::Space);
diff --git a/src/plugins/bearer/android/src/wrappers/androidconnectivitymanager.cpp b/src/plugins/bearer/android/src/wrappers/androidconnectivitymanager.cpp
index 971c694ce1..8b10c17bb5 100644
--- a/src/plugins/bearer/android/src/wrappers/androidconnectivitymanager.cpp
+++ b/src/plugins/bearer/android/src/wrappers/androidconnectivitymanager.cpp
@@ -116,7 +116,7 @@ bool AndroidTrafficStats::isTrafficStatsSupported()
             && AndroidTrafficStats::getTotalRxBytes() != -1);
 }
 
-static AndroidNetworkInfo::NetworkState stateForName(const QString stateName)
+static AndroidNetworkInfo::NetworkState stateForName(const QString &stateName)
 {
     if (stateName == QLatin1String("CONNECTED"))
         return AndroidNetworkInfo::Connected;
diff --git a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp b/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp
index 4697613833..4784a6e828 100644
--- a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp
+++ b/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp
@@ -259,7 +259,7 @@ QByteArray TableGenerator::readLocaleAliases(const QByteArray &locale)
     return fullLocaleName;
 }
 
-bool TableGenerator::processFile(QString composeFileName)
+bool TableGenerator::processFile(const QString &composeFileName)
 {
     QFile composeFile(composeFileName);
     if (composeFile.open(QIODevice::ReadOnly)) {
diff --git a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h b/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h
index 4ce23f4576..468da4cad1 100644
--- a/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h
+++ b/src/plugins/platforminputcontexts/compose/generator/qtablegenerator.h
@@ -103,7 +103,7 @@ public:
     TableState tableState() const { return m_state; }
 
 protected:
-    bool processFile(QString composeFileName);
+    bool processFile(const QString &composeFileName);
     void parseKeySequence(char *line);
     void parseIncludeInstruction(QString line);
 
diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.h b/src/plugins/platforms/cocoa/qcocoaintegration.h
index 12270b954f..3b79717472 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.h
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.h
@@ -77,7 +77,7 @@ public:
 
     // ----------------------------------------------------
     // Additional methods
-    void setVirtualSiblings(QList<QPlatformScreen *> siblings) { m_siblings = siblings; }
+    void setVirtualSiblings(const QList<QPlatformScreen *> &siblings) { m_siblings = siblings; }
     NSScreen *osScreen() const;
     void updateGeometry();
 
diff --git a/src/plugins/platforms/cocoa/qcocoasystemtrayicon.mm b/src/plugins/platforms/cocoa/qcocoasystemtrayicon.mm
index a2be0c9f72..1904a43276 100755
--- a/src/plugins/platforms/cocoa/qcocoasystemtrayicon.mm
+++ b/src/plugins/platforms/cocoa/qcocoasystemtrayicon.mm
@@ -180,7 +180,7 @@ void QCocoaSystemTrayIcon::cleanup()
 }
 
 static bool heightCompareFunction (QSize a, QSize b) { return (a.height() < b.height()); }
-static QList<QSize> sortByHeight(const QList<QSize> sizes)
+static QList<QSize> sortByHeight(const QList<QSize> &sizes)
 {
     QList<QSize> sorted = sizes;
     std::sort(sorted.begin(), sorted.end(), heightCompareFunction);
diff --git a/src/plugins/platforms/kms/qkmsintegration.cpp b/src/plugins/platforms/kms/qkmsintegration.cpp
index ff4dd59dbf..f48c868ae5 100644
--- a/src/plugins/platforms/kms/qkmsintegration.cpp
+++ b/src/plugins/platforms/kms/qkmsintegration.cpp
@@ -88,7 +88,7 @@ void QKmsIntegration::initialize()
     m_deviceDiscovery = QDeviceDiscovery::create(QDeviceDiscovery::Device_DRM | QDeviceDiscovery::Device_DRM_PrimaryGPU, 0);
     if (m_deviceDiscovery) {
         QStringList devices = m_deviceDiscovery->scanConnectedDevices();
-        foreach (QString device, devices)
+        foreach (const QString &device, devices)
             addDevice(device);
 
         connect(m_deviceDiscovery, SIGNAL(deviceDetected(QString)), this, SLOT(addDevice(QString)));
diff --git a/src/plugins/platforms/qnx/qqnxscreen.cpp b/src/plugins/platforms/qnx/qqnxscreen.cpp
index e0ef6a0b8f..7b7de01c82 100644
--- a/src/plugins/platforms/qnx/qqnxscreen.cpp
+++ b/src/plugins/platforms/qnx/qqnxscreen.cpp
@@ -112,7 +112,7 @@ static QSize determineScreenSize(screen_display_t display, bool primaryScreen) {
 #endif
 }
 
-static QQnxWindow *findMultimediaWindow(const QList<QQnxWindow*> windows,
+static QQnxWindow *findMultimediaWindow(const QList<QQnxWindow*> &windows,
                                                     const QByteArray &mmWindowId)
 {
     Q_FOREACH (QQnxWindow *sibling, windows) {
@@ -128,7 +128,7 @@ static QQnxWindow *findMultimediaWindow(const QList<QQnxWindow*> windows,
     return 0;
 }
 
-static QQnxWindow *findMultimediaWindow(const QList<QQnxWindow*> windows,
+static QQnxWindow *findMultimediaWindow(const QList<QQnxWindow*> &windows,
                                                     screen_window_t mmWindowId)
 {
     Q_FOREACH (QQnxWindow *sibling, windows) {
diff --git a/src/plugins/platforms/winrt/qwinrtfileengine.cpp b/src/plugins/platforms/winrt/qwinrtfileengine.cpp
index 38608d5e6c..664002a085 100644
--- a/src/plugins/platforms/winrt/qwinrtfileengine.cpp
+++ b/src/plugins/platforms/winrt/qwinrtfileengine.cpp
@@ -140,7 +140,7 @@ QAbstractFileEngine *QWinRTFileEngineHandler::create(const QString &fileName) co
     return Q_NULLPTR;
 }
 
-static HRESULT getDestinationFolder(const QString &fileName, const QString newFileName,
+static HRESULT getDestinationFolder(const QString &fileName, const QString &newFileName,
                                     IStorageItem *file, IStorageFolder **folder)
 {
     HRESULT hr;
diff --git a/src/plugins/platforms/xcb/qxcbcursor.cpp b/src/plugins/platforms/xcb/qxcbcursor.cpp
index 3df84fe767..e3a04c1d7b 100644
--- a/src/plugins/platforms/xcb/qxcbcursor.cpp
+++ b/src/plugins/platforms/xcb/qxcbcursor.cpp
@@ -484,7 +484,7 @@ xcb_cursor_t QXcbCursor::createNonStandardCursor(int cshape)
 }
 
 #ifdef XCB_USE_XLIB
-bool updateCursorTheme(void *dpy, const QByteArray theme) {
+bool updateCursorTheme(void *dpy, const QByteArray &theme) {
     if (!ptrXcursorLibraryGetTheme
             || !ptrXcursorLibrarySetTheme)
         return false;
diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.cpp b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
index ad2b9023e7..376599578f 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
@@ -680,7 +680,7 @@ void QXcbKeyboard::updateKeymap()
         if (qEnvironmentVariableIsSet("QT_XKB_CONFIG_ROOT")) {
             xkb_context = xkb_context_new((xkb_context_flags)XKB_CONTEXT_NO_DEFAULT_INCLUDES);
             QList<QByteArray> xkbRootList = QByteArray(qgetenv("QT_XKB_CONFIG_ROOT")).split(':');
-            foreach (QByteArray xkbRoot, xkbRootList)
+            foreach (const QByteArray &xkbRoot, xkbRootList)
                 xkb_context_include_path_append(xkb_context, xkbRoot.constData());
         } else {
             xkb_context = xkb_context_new((xkb_context_flags)0);
@@ -1045,7 +1045,7 @@ int QXcbKeyboard::keysymToQtKey(xcb_keysym_t key) const
     return code;
 }
 
-int QXcbKeyboard::keysymToQtKey(xcb_keysym_t keysym, Qt::KeyboardModifiers &modifiers, QString text) const
+int QXcbKeyboard::keysymToQtKey(xcb_keysym_t keysym, Qt::KeyboardModifiers &modifiers, const QString &text) const
 {
     int code = 0;
 #ifndef QT_NO_TEXTCODEC
diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.h b/src/plugins/platforms/xcb/qxcbkeyboard.h
index 28c1c66433..2281674e2f 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.h
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.h
@@ -80,7 +80,7 @@ protected:
     void resolveMaskConflicts();
     QString lookupString(struct xkb_state *state, xcb_keycode_t code) const;
     int keysymToQtKey(xcb_keysym_t keysym) const;
-    int keysymToQtKey(xcb_keysym_t keysym, Qt::KeyboardModifiers &modifiers, QString text) const;
+    int keysymToQtKey(xcb_keysym_t keysym, Qt::KeyboardModifiers &modifiers, const QString &text) const;
     void printKeymapError(const char *error) const;
 
     void readXKBConfig();
diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index 09acbaa648..e43652ab37 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -48,7 +48,7 @@
 QT_BEGIN_NAMESPACE
 
 QXcbScreen::QXcbScreen(QXcbConnection *connection, xcb_screen_t *scr,
-                       xcb_randr_get_output_info_reply_t *output, QString outputName, int number)
+                       xcb_randr_get_output_info_reply_t *output, const QString &outputName, int number)
     : QXcbObject(connection)
     , m_screen(scr)
     , m_crtc(output ? output->crtc : 0)
diff --git a/src/plugins/platforms/xcb/qxcbscreen.h b/src/plugins/platforms/xcb/qxcbscreen.h
index efc16bf67c..f327eb31b0 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.h
+++ b/src/plugins/platforms/xcb/qxcbscreen.h
@@ -55,7 +55,7 @@ class Q_XCB_EXPORT QXcbScreen : public QXcbObject, public QPlatformScreen
 {
 public:
     QXcbScreen(QXcbConnection *connection, xcb_screen_t *screen,
-               xcb_randr_get_output_info_reply_t *output, QString outputName, int number);
+               xcb_randr_get_output_info_reply_t *output, const QString &outputName, int number);
     ~QXcbScreen();
 
     QPixmap grabWindow(WId window, int x, int y, int width, int height) const Q_DECL_OVERRIDE;
diff --git a/src/sql/drivers/psql/qsql_psql.cpp b/src/sql/drivers/psql/qsql_psql.cpp
index 2120ccc92b..c83c633fd0 100644
--- a/src/sql/drivers/psql/qsql_psql.cpp
+++ b/src/sql/drivers/psql/qsql_psql.cpp
@@ -565,7 +565,7 @@ void QPSQLResult::virtual_hook(int id, void *data)
     QSqlResult::virtual_hook(id, data);
 }
 
-static QString qCreateParamString(const QVector<QVariant> boundValues, const QSqlDriver *driver)
+static QString qCreateParamString(const QVector<QVariant> &boundValues, const QSqlDriver *driver)
 {
     if (boundValues.isEmpty())
         return QString();
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 4486d4c54e..a9e33da01d 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -818,7 +818,7 @@ static void findRequiredContainers(ClassDef *cdef, QSet<QByteArray> *requiredQtC
 
     for (int i = 0; i < cdef->propertyList.count(); ++i) {
         const PropertyDef &p = cdef->propertyList.at(i);
-        foreach (const QByteArray candidate, candidates) {
+        foreach (const QByteArray &candidate, candidates) {
             if (p.type.contains(candidate + "<"))
                 requiredQtContainers->insert(candidate);
         }
@@ -829,7 +829,7 @@ static void findRequiredContainers(ClassDef *cdef, QSet<QByteArray> *requiredQtC
     for (int i = 0; i < allFunctions.count(); ++i) {
         const FunctionDef &f = allFunctions.at(i);
         foreach (const ArgumentDef &arg, f.arguments) {
-            foreach (const QByteArray candidate, candidates) {
+            foreach (const QByteArray &candidate, candidates) {
                 if (arg.normalizedType.contains(candidate + "<"))
                     requiredQtContainers->insert(candidate);
             }
diff --git a/src/tools/qdoc/doc.h b/src/tools/qdoc/doc.h
index 2c007b9de9..80d47287bb 100644
--- a/src/tools/qdoc/doc.h
+++ b/src/tools/qdoc/doc.h
@@ -64,7 +64,7 @@ struct Topic
     QString topic;
     QString args;
     Topic() { }
-    Topic(QString& t, QString a) : topic(t), args(a) { }
+    Topic(QString& t, const QString &a) : topic(t), args(a) { }
     bool isEmpty() const { return topic.isEmpty(); }
     void clear() { topic.clear(); args.clear(); }
 };
diff --git a/src/tools/qdoc/doc/examples/mainwindow.cpp b/src/tools/qdoc/doc/examples/mainwindow.cpp
index 6a03a8e8f2..68b878c07e 100644
--- a/src/tools/qdoc/doc/examples/mainwindow.cpp
+++ b/src/tools/qdoc/doc/examples/mainwindow.cpp
@@ -136,7 +136,7 @@ void MainWindow::createActions()
     openAct->setShortcuts(QKeySequence::Open);
     connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
 
-    foreach (QByteArray format, QImageWriter::supportedImageFormats()) {
+    foreach (const QByteArray &format, QImageWriter::supportedImageFormats()) {
         QString text = tr("%1...").arg(QString(format).toUpper());
 
         QAction *action = new QAction(text, this);
diff --git a/src/tools/qdoc/htmlgenerator.cpp b/src/tools/qdoc/htmlgenerator.cpp
index d422356822..f4ada7132f 100644
--- a/src/tools/qdoc/htmlgenerator.cpp
+++ b/src/tools/qdoc/htmlgenerator.cpp
@@ -3190,7 +3190,7 @@ void HtmlGenerator::generateList(const Node* relative, CodeMarker* marker, const
 
 #if 0
     QStringList keys = groups.uniqueKeys();
-    foreach (QString key, keys) {
+    foreach (const QString &key, keys) {
         GroupNode* gn = static_cast<GroupNode*>(groups.value(key));
         if (gn) {
             out() << QString("<h3><a href=\"%1\">%2</a></h3>\n").arg(
@@ -3217,7 +3217,7 @@ void HtmlGenerator::generateList(const Node* relative, CodeMarker* marker, const
 
             out() << "<ul>\n";
             QStringList titles = nm.keys();
-            foreach (QString t, titles) {
+            foreach (const QString &t, titles) {
                 Node* member = nm.value(t);
                 QString title = member->fullTitle();
                 if (title.startsWith("The "))
@@ -4484,7 +4484,7 @@ void HtmlGenerator::generateManifestFiles()
   for each manifest file to be generated. \a manifest is the
   type of manifest file.
  */
-void HtmlGenerator::generateManifestFile(QString manifest, QString element)
+void HtmlGenerator::generateManifestFile(const QString &manifest, const QString &element)
 {
     ExampleNodeMap& exampleNodeMap = qdb_->exampleNodeMap();
     if (exampleNodeMap.isEmpty())
diff --git a/src/tools/qdoc/htmlgenerator.h b/src/tools/qdoc/htmlgenerator.h
index 9645219933..44408c0eb2 100644
--- a/src/tools/qdoc/htmlgenerator.h
+++ b/src/tools/qdoc/htmlgenerator.h
@@ -104,7 +104,7 @@ protected:
     virtual QString refForNode(const Node *node);
     virtual QString linkForNode(const Node *node, const Node *relative);
 
-    void generateManifestFile(QString manifest, QString element);
+    void generateManifestFile(const QString &manifest, const QString &element);
     void readManifestMetaContent(const Config &config);
     void generateKeywordAnchors(const Node* node);
 
diff --git a/src/tools/qdoc/node.cpp b/src/tools/qdoc/node.cpp
index 2d38720a36..b00276a58c 100644
--- a/src/tools/qdoc/node.cpp
+++ b/src/tools/qdoc/node.cpp
@@ -2474,7 +2474,7 @@ QString Node::fullDocumentName() const
   be used as the value of an \e id attribute. Search for NCName
   on the internet for details of what can be an NCName.
  */
-QString Node::cleanId(QString str)
+QString Node::cleanId(const QString &str)
 {
     QString clean;
     QString name = str.simplified();
diff --git a/src/tools/qdoc/node.h b/src/tools/qdoc/node.h
index df41aa00ff..610ab0875e 100644
--- a/src/tools/qdoc/node.h
+++ b/src/tools/qdoc/node.h
@@ -305,7 +305,7 @@ public:
     const QString& outputSubdirectory() const { return outSubDir_; }
     void setOutputSubdirectory(const QString& t) { outSubDir_ = t; }
     QString fullDocumentName() const;
-    static QString cleanId(QString str);
+    static QString cleanId(const QString &str);
     QString idForNode() const;
 
     static FlagValue toFlagValue(bool b);
diff --git a/src/tools/qdoc/qdocdatabase.cpp b/src/tools/qdoc/qdocdatabase.cpp
index cad213df90..4f1a38d189 100644
--- a/src/tools/qdoc/qdocdatabase.cpp
+++ b/src/tools/qdoc/qdocdatabase.cpp
@@ -1549,7 +1549,7 @@ void QDocDatabase::mergeCollections(Node::Type nt, CNMap& cnm, const Node* relat
     if (cnmm.isEmpty())
         return;
     QStringList keys = cnmm.uniqueKeys();
-    foreach (QString key, keys) {
+    foreach (const QString &key, keys) {
         QList<CollectionNode*> values = cnmm.values(key);
         CollectionNode* n = 0;
         foreach (CollectionNode* v, values) {
diff --git a/src/tools/qdoc/qdocindexfiles.cpp b/src/tools/qdoc/qdocindexfiles.cpp
index 240704e1f9..efc0eb1e0f 100644
--- a/src/tools/qdoc/qdocindexfiles.cpp
+++ b/src/tools/qdoc/qdocindexfiles.cpp
@@ -542,7 +542,7 @@ void QDocIndexFiles::readIndexSection(const QDomElement& element,
     QString groupsAttr = element.attribute("groups");
     if (!groupsAttr.isEmpty()) {
         QStringList groupNames = groupsAttr.split(",");
-        foreach (QString name, groupNames) {
+        foreach (const QString &name, groupNames) {
             qdb_->addToGroup(name, node);
         }
     }
diff --git a/src/tools/qlalr/main.cpp b/src/tools/qlalr/main.cpp
index 56d69c012b..44523fc05f 100644
--- a/src/tools/qlalr/main.cpp
+++ b/src/tools/qlalr/main.cpp
@@ -75,8 +75,7 @@ int main (int argc, char *argv[])
   QStringList args = app.arguments ();
   args.removeFirst ();
 
-  foreach (QString arg, args)
-    {
+  foreach (const QString &arg, args) {
       if (arg == QLatin1String ("-h") || arg == QLatin1String ("--help"))
         help_me ();
 
diff --git a/src/tools/uic/cpp/cppwriteicondata.cpp b/src/tools/uic/cpp/cppwriteicondata.cpp
index 51b37b191f..ee80ee1643 100644
--- a/src/tools/uic/cpp/cppwriteicondata.cpp
+++ b/src/tools/uic/cpp/cppwriteicondata.cpp
@@ -42,7 +42,7 @@ QT_BEGIN_NAMESPACE
 
 namespace CPP {
 
-static QByteArray transformImageData(QString data)
+static QByteArray transformImageData(const QString &data)
 {
     int baSize = data.length() / 2;
     uchar *ba = new uchar[baSize];
@@ -66,7 +66,7 @@ static QByteArray transformImageData(QString data)
     return ret;
 }
 
-static QByteArray unzipXPM(QString data, ulong& length)
+static QByteArray unzipXPM(const QString &data, ulong &length)
 {
 #ifndef QT_NO_COMPRESS
     const int lengthOffset = 4;
diff --git a/src/widgets/dialogs/qfiledialog.cpp b/src/widgets/dialogs/qfiledialog.cpp
index 26ffc80f46..4616933bcf 100644
--- a/src/widgets/dialogs/qfiledialog.cpp
+++ b/src/widgets/dialogs/qfiledialog.cpp
@@ -1214,7 +1214,7 @@ QList<QUrl> QFileDialogPrivate::userSelectedFiles() const
     return files;
 }
 
-QStringList QFileDialogPrivate::addDefaultSuffixToFiles(const QStringList filesToFix) const
+QStringList QFileDialogPrivate::addDefaultSuffixToFiles(const QStringList &filesToFix) const
 {
     QStringList files;
     for (int i=0; i<filesToFix.size(); ++i) {
@@ -3590,7 +3590,7 @@ void QFileDialogPrivate::_q_rowsInserted(const QModelIndex &parent)
         return;
 }
 
-void QFileDialogPrivate::_q_fileRenamed(const QString &path, const QString oldName, const QString newName)
+void QFileDialogPrivate::_q_fileRenamed(const QString &path, const QString &oldName, const QString &newName)
 {
     const QFileDialog::FileMode fileMode = q_func()->fileMode();
     if (fileMode == QFileDialog::Directory || fileMode == QFileDialog::DirectoryOnly) {
diff --git a/src/widgets/dialogs/qfiledialog.h b/src/widgets/dialogs/qfiledialog.h
index 1318915c74..e921ae0d05 100644
--- a/src/widgets/dialogs/qfiledialog.h
+++ b/src/widgets/dialogs/qfiledialog.h
@@ -289,7 +289,8 @@ private:
     Q_PRIVATE_SLOT(d_func(), void _q_autoCompleteFileName(const QString &text))
     Q_PRIVATE_SLOT(d_func(), void _q_rowsInserted(const QModelIndex & parent))
     Q_PRIVATE_SLOT(d_func(), void _q_fileRenamed(const QString &path,
-                const QString oldName, const QString newName))
+                                                 const QString &oldName,
+                                                 const QString &newName))
     friend class QPlatformDialogHelper;
 };
 
diff --git a/src/widgets/dialogs/qfiledialog_p.h b/src/widgets/dialogs/qfiledialog_p.h
index eb5f49cb55..9eb08f7a3a 100644
--- a/src/widgets/dialogs/qfiledialog_p.h
+++ b/src/widgets/dialogs/qfiledialog_p.h
@@ -123,7 +123,7 @@ public:
     static QString initialSelection(const QUrl &path);
     QStringList typedFiles() const;
     QList<QUrl> userSelectedFiles() const;
-    QStringList addDefaultSuffixToFiles(const QStringList filesToFix) const;
+    QStringList addDefaultSuffixToFiles(const QStringList &filesToFix) const;
     QList<QUrl> addDefaultSuffixToUrls(const QList<QUrl> &urlsToFix) const;
     bool removeDirectory(const QString &path);
     void setLabelTextControl(QFileDialog::DialogLabel label, const QString &text);
@@ -212,7 +212,7 @@ public:
     void _q_goToUrl(const QUrl &url);
     void _q_autoCompleteFileName(const QString &);
     void _q_rowsInserted(const QModelIndex & parent);
-    void _q_fileRenamed(const QString &path, const QString oldName, const QString newName);
+    void _q_fileRenamed(const QString &path, const QString &oldName, const QString &newName);
 
     // layout
 #ifndef QT_NO_PROXYMODEL
diff --git a/src/widgets/dialogs/qfilesystemmodel_p.h b/src/widgets/dialogs/qfilesystemmodel_p.h
index a0551b34cc..dd4b25d59c 100644
--- a/src/widgets/dialogs/qfilesystemmodel_p.h
+++ b/src/widgets/dialogs/qfilesystemmodel_p.h
@@ -148,7 +148,7 @@ public:
         }
 
         // children shouldn't normally be accessed directly, use node()
-        inline int visibleLocation(QString childName) {
+        inline int visibleLocation(const QString &childName) {
             return visibleChildren.indexOf(childName);
         }
         void updateIcon(QFileIconProvider *iconProvider, const QString &path) {
diff --git a/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp b/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp
index 3462b6da9e..8327777217 100644
--- a/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -2049,7 +2049,7 @@ void QGraphicsAnchorLayoutPrivate::calculateGraphs()
 
 // ### Maybe getGraphParts could return the variables when traversing, at least
 // for trunk...
-QList<AnchorData *> getVariables(QList<QSimplexConstraint *> constraints)
+QList<AnchorData *> getVariables(const QList<QSimplexConstraint *> &constraints)
 {
     QSet<AnchorData *> variableSet;
     for (int i = 0; i < constraints.count(); ++i) {
diff --git a/src/widgets/graphicsview/qsimplex_p.cpp b/src/widgets/graphicsview/qsimplex_p.cpp
index ed63ee508d..1aeade6640 100644
--- a/src/widgets/graphicsview/qsimplex_p.cpp
+++ b/src/widgets/graphicsview/qsimplex_p.cpp
@@ -118,7 +118,7 @@ void QSimplex::clearDataStructures()
   This method sets the new constraints, normalizes them, creates the simplex matrix
   and runs the first simplex phase.
 */
-bool QSimplex::setConstraints(const QList<QSimplexConstraint *> newConstraints)
+bool QSimplex::setConstraints(const QList<QSimplexConstraint *> &newConstraints)
 {
     ////////////////////////////
     // Reset to initial state //
diff --git a/src/widgets/graphicsview/qsimplex_p.h b/src/widgets/graphicsview/qsimplex_p.h
index c731944ebb..2e98ca068b 100644
--- a/src/widgets/graphicsview/qsimplex_p.h
+++ b/src/widgets/graphicsview/qsimplex_p.h
@@ -149,7 +149,7 @@ public:
     qreal solveMin();
     qreal solveMax();
 
-    bool setConstraints(const QList<QSimplexConstraint *> constraints);
+    bool setConstraints(const QList<QSimplexConstraint *> &constraints);
     void setObjective(QSimplexConstraint *objective);
 
     void dumpMatrix();
diff --git a/src/widgets/styles/qandroidstyle.cpp b/src/widgets/styles/qandroidstyle.cpp
index b570edaf68..f1d5eca90b 100644
--- a/src/widgets/styles/qandroidstyle.cpp
+++ b/src/widgets/styles/qandroidstyle.cpp
@@ -1229,7 +1229,7 @@ const QAndroidStyle::AndroidDrawable * QAndroidStyle::AndroidStateDrawable::best
 int QAndroidStyle::AndroidStateDrawable::extractState(const QVariantMap &value)
 {
     int state = QStyle::State_Enabled | QStyle::State_Active;;
-    foreach (const QString key, value.keys()) {
+    foreach (const QString &key, value.keys()) {
         bool val = value.value(key).toString() == QLatin1String("true");
         if (key == QLatin1String("enabled")) {
             if (val)
diff --git a/src/widgets/util/qcompleter_p.h b/src/widgets/util/qcompleter_p.h
index 1ed79f94bc..b100f24f9b 100644
--- a/src/widgets/util/qcompleter_p.h
+++ b/src/widgets/util/qcompleter_p.h
@@ -101,7 +101,7 @@ class QIndexMapper
 public:
     QIndexMapper() : v(false), f(0), t(-1) { }
     QIndexMapper(int f, int t) : v(false), f(f), t(t) { }
-    QIndexMapper(QVector<int> vec) : v(true), vector(vec), f(-1), t(-1) { }
+    QIndexMapper(const QVector<int> &vec) : v(true), vector(vec), f(-1), t(-1) { }
 
     inline int count() const { return v ? vector.count() : t - f + 1; }
     inline int operator[] (int index) const { return v ? vector[index] : f + index; }
diff --git a/src/widgets/widgets/qlineedit.h b/src/widgets/widgets/qlineedit.h
index 3daecbcb56..e006f1c0d8 100644
--- a/src/widgets/widgets/qlineedit.h
+++ b/src/widgets/widgets/qlineedit.h
@@ -240,7 +240,7 @@ private:
     Q_PRIVATE_SLOT(d_func(), void _q_textEdited(const QString &))
     Q_PRIVATE_SLOT(d_func(), void _q_cursorPositionChanged(int, int))
 #ifndef QT_NO_COMPLETER
-    Q_PRIVATE_SLOT(d_func(), void _q_completionHighlighted(QString))
+    Q_PRIVATE_SLOT(d_func(), void _q_completionHighlighted(const QString &))
 #endif
 #ifdef QT_KEYPAD_NAVIGATION
     Q_PRIVATE_SLOT(d_func(), void _q_editFocusChange(bool))
diff --git a/src/widgets/widgets/qlineedit_p.cpp b/src/widgets/widgets/qlineedit_p.cpp
index e913c81a36..b7d2ab4059 100644
--- a/src/widgets/widgets/qlineedit_p.cpp
+++ b/src/widgets/widgets/qlineedit_p.cpp
@@ -77,7 +77,7 @@ QRect QLineEditPrivate::cursorRect() const
 
 #ifndef QT_NO_COMPLETER
 
-void QLineEditPrivate::_q_completionHighlighted(QString newText)
+void QLineEditPrivate::_q_completionHighlighted(const QString &newText)
 {
     Q_Q(QLineEdit);
     if (control->completer()->completionMode() != QCompleter::InlineCompletion) {
diff --git a/src/widgets/widgets/qlineedit_p.h b/src/widgets/widgets/qlineedit_p.h
index 4870cc761d..1ede07e4cb 100644
--- a/src/widgets/widgets/qlineedit_p.h
+++ b/src/widgets/widgets/qlineedit_p.h
@@ -183,7 +183,7 @@ public:
     void _q_selectionChanged();
     void _q_updateNeeded(const QRect &);
 #ifndef QT_NO_COMPLETER
-    void _q_completionHighlighted(QString);
+    void _q_completionHighlighted(const QString &);
 #endif
     QPoint mousePressPos;
 #ifndef QT_NO_DRAGANDDROP