diff --git a/src/core/kernel/qabstractitemmodel.cpp b/src/core/kernel/qabstractitemmodel.cpp
index 19ede5016..f432f65b2 100644
--- a/src/core/kernel/qabstractitemmodel.cpp
+++ b/src/core/kernel/qabstractitemmodel.cpp
@@ -664,7 +664,7 @@ 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/core/kernel/qabstractitemmodel_p.h b/src/core/kernel/qabstractitemmodel_p.h
index bffd94960..f95bf13a4 100644
--- a/src/core/kernel/qabstractitemmodel_p.h
+++ b/src/core/kernel/qabstractitemmodel_p.h
@@ -79,7 +79,7 @@ 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/gui/dialogs/qfiledialog.cpp b/src/gui/dialogs/qfiledialog.cpp
index 84cc36955..a2ea692a7 100644
--- a/src/gui/dialogs/qfiledialog.cpp
+++ b/src/gui/dialogs/qfiledialog.cpp
@@ -910,7 +910,7 @@ QStringList QFileDialogPrivate::typedFiles() const
     return addDefaultSuffixToFiles(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) {
@@ -2918,7 +2918,7 @@ 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)
 {
     if (fileMode == QFileDialog::Directory || fileMode == QFileDialog::DirectoryOnly) {
         if (path == rootPath() && lineEdit()->text() == oldName)
diff --git a/src/gui/dialogs/qfiledialog_p.h b/src/gui/dialogs/qfiledialog_p.h
index 100e92043..c2e0876b4 100644
--- a/src/gui/dialogs/qfiledialog_p.h
+++ b/src/gui/dialogs/qfiledialog_p.h
@@ -125,7 +125,7 @@ public:
     static QString workingDirectory(const QString &path);
     static QString initialSelection(const QString &path);
     QStringList typedFiles() const;
-    QStringList addDefaultSuffixToFiles(const QStringList filesToFix) const;
+    QStringList addDefaultSuffixToFiles(const QStringList &filesToFix) const;
     bool removeDirectory(const QString &path);
 
     inline QModelIndex mapToSource(const QModelIndex &index) const;
@@ -188,8 +188,8 @@ public:
     void _q_selectionChanged();
     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_rowsInserted(const QModelIndex &parent);
+    void _q_fileRenamed(const QString &path, const QString &oldName, const QString &newName);
 
     // layout
 #ifndef QT_NO_PROXYMODEL
diff --git a/src/gui/dialogs/qfilesystemmodel_p.h b/src/gui/dialogs/qfilesystemmodel_p.h
index e46592065..64bd1c9bd 100644
--- a/src/gui/dialogs/qfilesystemmodel_p.h
+++ b/src/gui/dialogs/qfilesystemmodel_p.h
@@ -155,7 +155,7 @@ 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/gui/graphicsview/qgraphicsanchorlayout_p.cpp b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
index 6011b9275..388b9d3cf 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -2034,7 +2034,7 @@ 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/gui/graphicsview/qsimplex_p.cpp b/src/gui/graphicsview/qsimplex_p.cpp
index 61facbce0..bf257f25f 100644
--- a/src/gui/graphicsview/qsimplex_p.cpp
+++ b/src/gui/graphicsview/qsimplex_p.cpp
@@ -126,7 +126,7 @@ 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/gui/graphicsview/qsimplex_p.h b/src/gui/graphicsview/qsimplex_p.h
index 78e15a581..90a203a77 100644
--- a/src/gui/graphicsview/qsimplex_p.h
+++ b/src/gui/graphicsview/qsimplex_p.h
@@ -155,7 +155,7 @@ 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/gui/util/qcompleter_p.h b/src/gui/util/qcompleter_p.h
index 263bd67e7..bef026289 100644
--- a/src/gui/util/qcompleter_p.h
+++ b/src/gui/util/qcompleter_p.h
@@ -108,7 +108,7 @@ 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/gui/widgets/qlineedit.h b/src/gui/widgets/qlineedit.h
index cbd23b79c..225a47876 100644
--- a/src/gui/widgets/qlineedit.h
+++ b/src/gui/widgets/qlineedit.h
@@ -233,7 +233,7 @@ 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/gui/widgets/qlineedit_p.cpp b/src/gui/widgets/qlineedit_p.cpp
index 803f8c6cc..8ccfdd1ba 100644
--- a/src/gui/widgets/qlineedit_p.cpp
+++ b/src/gui/widgets/qlineedit_p.cpp
@@ -76,8 +76,7 @@ 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) {
@@ -90,7 +89,6 @@ void QLineEditPrivate::_q_completionHighlighted(QString newText)
         control->moveCursor(c, true);
     }
 }
-
 #endif // QT_NO_COMPLETER
 
 void QLineEditPrivate::_q_handleWindowActivate()
diff --git a/src/gui/widgets/qlineedit_p.h b/src/gui/widgets/qlineedit_p.h
index 046bcbf4a..a7d361eeb 100644
--- a/src/gui/widgets/qlineedit_p.h
+++ b/src/gui/widgets/qlineedit_p.h
@@ -125,7 +125,7 @@ public:
     void _q_selectionChanged();
     void _q_updateNeeded(const QRect &);
 #ifndef QT_NO_COMPLETER
-    void _q_completionHighlighted(QString);
+    void _q_completionHighlighted(const QString&);
 #endif
 #ifndef QT_NO_DRAGANDDROP
     QPoint dndPos;
diff --git a/src/plugins/sqldrivers/psql/qsql_psql.cpp b/src/plugins/sqldrivers/psql/qsql_psql.cpp
index b783f77e7..0cc8e52db 100644
--- a/src/plugins/sqldrivers/psql/qsql_psql.cpp
+++ b/src/plugins/sqldrivers/psql/qsql_psql.cpp
@@ -549,7 +549,7 @@ static QString qReplacePlaceholderMarkers(const QString &query)
     return result;
 }
 
-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/uic/cpp/cppwriteicondata.cpp b/src/tools/uic/cpp/cppwriteicondata.cpp
index b0b7bf530..9450d3686 100644
--- a/src/tools/uic/cpp/cppwriteicondata.cpp
+++ b/src/tools/uic/cpp/cppwriteicondata.cpp
@@ -50,7 +50,7 @@ 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];
@@ -74,7 +74,7 @@ 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/util/qlalr/main.cpp b/util/qlalr/main.cpp
index df5db73f7..a045f3b78 100644
--- a/util/qlalr/main.cpp
+++ b/util/qlalr/main.cpp
@@ -83,7 +83,7 @@ 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 ();