QtCore: Use Q_NULLPTR instead of 0 in all public headers

This is in preparation of adding -Wzero-as-null-pointer-constant (or similar)
to the headers check.

Task-number: QTBUG-45291
Change-Id: I0cc388ef9faf45cbcf425ad0dc77db3060c104a8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

72 files changed, 291 insertions, 290 deletions

diff --git a/src/corelib/animation/qabstractanimation.h b/src/corelib/animation/qabstractanimation.h
index da78341d90..7085a9fc5e 100644
--- a/src/corelib/animation/qabstractanimation.h
+++ b/src/corelib/animation/qabstractanimation.h
@@ -76,7 +76,7 @@ public:
         DeleteWhenStopped
     };
 
-    QAbstractAnimation(QObject *parent = 0);
+    QAbstractAnimation(QObject *parent = Q_NULLPTR);
     virtual ~QAbstractAnimation();
 
     State state() const;
@@ -111,7 +111,7 @@ public Q_SLOTS:
     void setCurrentTime(int msecs);
 
 protected:
-    QAbstractAnimation(QAbstractAnimationPrivate &dd, QObject *parent = 0);
+    QAbstractAnimation(QAbstractAnimationPrivate &dd, QObject *parent = Q_NULLPTR);
     bool event(QEvent *event) Q_DECL_OVERRIDE;
 
     virtual void updateCurrentTime(int currentTime) = 0;
@@ -130,7 +130,7 @@ class Q_CORE_EXPORT QAnimationDriver : public QObject
     Q_DECLARE_PRIVATE(QAnimationDriver)
 
 public:
-    QAnimationDriver(QObject *parent = 0);
+    QAnimationDriver(QObject *parent = Q_NULLPTR);
     ~QAnimationDriver();
 
     virtual void advance();
@@ -156,7 +156,7 @@ protected:
     virtual void start();
     virtual void stop();
 
-    QAnimationDriver(QAnimationDriverPrivate &dd, QObject *parent = 0);
+    QAnimationDriver(QAnimationDriverPrivate &dd, QObject *parent = Q_NULLPTR);
 
 private:
     friend class QUnifiedTimer;
diff --git a/src/corelib/animation/qanimationgroup.h b/src/corelib/animation/qanimationgroup.h
index 9b180b1704..b668b503b4 100644
--- a/src/corelib/animation/qanimationgroup.h
+++ b/src/corelib/animation/qanimationgroup.h
@@ -47,7 +47,7 @@ class Q_CORE_EXPORT QAnimationGroup : public QAbstractAnimation
     Q_OBJECT
 
 public:
-    QAnimationGroup(QObject *parent = 0);
+    QAnimationGroup(QObject *parent = Q_NULLPTR);
     ~QAnimationGroup();
 
     QAbstractAnimation *animationAt(int index) const;
diff --git a/src/corelib/animation/qparallelanimationgroup.h b/src/corelib/animation/qparallelanimationgroup.h
index 52a61dafcd..7ce05d6344 100644
--- a/src/corelib/animation/qparallelanimationgroup.h
+++ b/src/corelib/animation/qparallelanimationgroup.h
@@ -47,7 +47,7 @@ class Q_CORE_EXPORT QParallelAnimationGroup : public QAnimationGroup
     Q_OBJECT
 
 public:
-    QParallelAnimationGroup(QObject *parent = 0);
+    QParallelAnimationGroup(QObject *parent = Q_NULLPTR);
     ~QParallelAnimationGroup();
 
     int duration() const Q_DECL_OVERRIDE;
diff --git a/src/corelib/animation/qpauseanimation.h b/src/corelib/animation/qpauseanimation.h
index 159d82f969..5207472623 100644
--- a/src/corelib/animation/qpauseanimation.h
+++ b/src/corelib/animation/qpauseanimation.h
@@ -48,8 +48,8 @@ class Q_CORE_EXPORT QPauseAnimation : public QAbstractAnimation
     Q_OBJECT
     Q_PROPERTY(int duration READ duration WRITE setDuration)
 public:
-    QPauseAnimation(QObject *parent = 0);
-    QPauseAnimation(int msecs, QObject *parent = 0);
+    QPauseAnimation(QObject *parent = Q_NULLPTR);
+    QPauseAnimation(int msecs, QObject *parent = Q_NULLPTR);
     ~QPauseAnimation();
 
     int duration() const Q_DECL_OVERRIDE;
diff --git a/src/corelib/animation/qpropertyanimation.h b/src/corelib/animation/qpropertyanimation.h
index 8d06a9f354..c0d30ba0fd 100644
--- a/src/corelib/animation/qpropertyanimation.h
+++ b/src/corelib/animation/qpropertyanimation.h
@@ -49,8 +49,8 @@ class Q_CORE_EXPORT QPropertyAnimation : public QVariantAnimation
     Q_PROPERTY(QObject* targetObject READ targetObject WRITE setTargetObject)
 
 public:
-    QPropertyAnimation(QObject *parent = 0);
-    QPropertyAnimation(QObject *target, const QByteArray &propertyName, QObject *parent = 0);
+    QPropertyAnimation(QObject *parent = Q_NULLPTR);
+    QPropertyAnimation(QObject *target, const QByteArray &propertyName, QObject *parent = Q_NULLPTR);
     ~QPropertyAnimation();
 
     QObject *targetObject() const;
diff --git a/src/corelib/animation/qsequentialanimationgroup.h b/src/corelib/animation/qsequentialanimationgroup.h
index 1a4ead90d4..c8a84a1220 100644
--- a/src/corelib/animation/qsequentialanimationgroup.h
+++ b/src/corelib/animation/qsequentialanimationgroup.h
@@ -50,7 +50,7 @@ class Q_CORE_EXPORT QSequentialAnimationGroup : public QAnimationGroup
     Q_PROPERTY(QAbstractAnimation* currentAnimation READ currentAnimation NOTIFY currentAnimationChanged)
 
 public:
-    QSequentialAnimationGroup(QObject *parent = 0);
+    QSequentialAnimationGroup(QObject *parent = Q_NULLPTR);
     ~QSequentialAnimationGroup();
 
     QPauseAnimation *addPause(int msecs);
diff --git a/src/corelib/animation/qvariantanimation.h b/src/corelib/animation/qvariantanimation.h
index 8a6524a594..4340a187a2 100644
--- a/src/corelib/animation/qvariantanimation.h
+++ b/src/corelib/animation/qvariantanimation.h
@@ -59,7 +59,7 @@ public:
     typedef QPair<qreal, QVariant> KeyValue;
     typedef QVector<KeyValue> KeyValues;
 
-    QVariantAnimation(QObject *parent = 0);
+    QVariantAnimation(QObject *parent = Q_NULLPTR);
     ~QVariantAnimation();
 
     QVariant startValue() const;
@@ -88,7 +88,7 @@ Q_SIGNALS:
     void valueChanged(const QVariant &value);
 
 protected:
-    QVariantAnimation(QVariantAnimationPrivate &dd, QObject *parent = 0);
+    QVariantAnimation(QVariantAnimationPrivate &dd, QObject *parent = Q_NULLPTR);
     bool event(QEvent *event) Q_DECL_OVERRIDE;
 
     void updateCurrentTime(int) Q_DECL_OVERRIDE;
diff --git a/src/corelib/codecs/qtextcodec.h b/src/corelib/codecs/qtextcodec.h
index 1d5e25efcc..3e73872d64 100644
--- a/src/corelib/codecs/qtextcodec.h
+++ b/src/corelib/codecs/qtextcodec.h
@@ -88,7 +88,7 @@ public:
 
     struct Q_CORE_EXPORT ConverterState {
         ConverterState(ConversionFlags f = DefaultConversion)
-            : flags(f), remainingChars(0), invalidChars(0), d(0) { state_data[0] = state_data[1] = state_data[2] = 0; }
+            : flags(f), remainingChars(0), invalidChars(0), d(Q_NULLPTR) { state_data[0] = state_data[1] = state_data[2] = 0; }
         ~ConverterState();
         ConversionFlags flags;
         int remainingChars;
@@ -99,9 +99,9 @@ public:
         Q_DISABLE_COPY(ConverterState)
     };
 
-    QString toUnicode(const char *in, int length, ConverterState *state = 0) const
+    QString toUnicode(const char *in, int length, ConverterState *state = Q_NULLPTR) const
         { return convertToUnicode(in, length, state); }
-    QByteArray fromUnicode(const QChar *in, int length, ConverterState *state = 0) const
+    QByteArray fromUnicode(const QChar *in, int length, ConverterState *state = Q_NULLPTR) const
         { return convertFromUnicode(in, length, state); }
 
     QTextDecoder* makeDecoder(ConversionFlags flags = DefaultConversion) const;
diff --git a/src/corelib/global/qflags.h b/src/corelib/global/qflags.h
index d3b9c3f5a7..f434e87c85 100644
--- a/src/corelib/global/qflags.h
+++ b/src/corelib/global/qflags.h
@@ -109,7 +109,7 @@ public:
     inline QFlags &operator=(const QFlags &other);
 #endif
     Q_DECL_CONSTEXPR inline QFlags(Enum f) Q_DECL_NOTHROW : i(Int(f)) {}
-    Q_DECL_CONSTEXPR inline QFlags(Zero = 0) Q_DECL_NOTHROW : i(0) {}
+    Q_DECL_CONSTEXPR inline QFlags(Zero = Q_NULLPTR) Q_DECL_NOTHROW : i(0) {}
     Q_DECL_CONSTEXPR inline QFlags(QFlag f) Q_DECL_NOTHROW : i(f) {}
 
 #ifdef Q_COMPILER_INITIALIZER_LISTS
diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index 7c32c0b0a2..51dd64c7cc 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -1079,7 +1079,7 @@ Q_CORE_EXPORT bool qunsetenv(const char *varName);
 
 Q_CORE_EXPORT bool qEnvironmentVariableIsEmpty(const char *varName) Q_DECL_NOEXCEPT;
 Q_CORE_EXPORT bool qEnvironmentVariableIsSet(const char *varName) Q_DECL_NOEXCEPT;
-Q_CORE_EXPORT int  qEnvironmentVariableIntValue(const char *varName, bool *ok=0) Q_DECL_NOEXCEPT;
+Q_CORE_EXPORT int  qEnvironmentVariableIntValue(const char *varName, bool *ok=Q_NULLPTR) Q_DECL_NOEXCEPT;
 
 inline int qIntCast(double f) { return int(f); }
 inline int qIntCast(float f) { return int(f); }
diff --git a/src/corelib/global/qlogging.h b/src/corelib/global/qlogging.h
index 679afddb20..c63346086a 100644
--- a/src/corelib/global/qlogging.h
+++ b/src/corelib/global/qlogging.h
@@ -57,7 +57,8 @@ class QMessageLogContext
 {
     Q_DISABLE_COPY(QMessageLogContext)
 public:
-    Q_DECL_CONSTEXPR QMessageLogContext() : version(2), line(0), file(0), function(0), category(0) {}
+    Q_DECL_CONSTEXPR QMessageLogContext()
+        : version(2), line(0), file(Q_NULLPTR), function(Q_NULLPTR), category(Q_NULLPTR) {}
     Q_DECL_CONSTEXPR QMessageLogContext(const char *fileName, int lineNumber, const char *functionName, const char *categoryName)
         : version(2), line(lineNumber), file(fileName), function(functionName), category(categoryName) {}
 
diff --git a/src/corelib/io/qbuffer.h b/src/corelib/io/qbuffer.h
index 1b2758d040..233c702213 100644
--- a/src/corelib/io/qbuffer.h
+++ b/src/corelib/io/qbuffer.h
@@ -51,8 +51,8 @@ class Q_CORE_EXPORT QBuffer : public QIODevice
 
 public:
 #ifndef QT_NO_QOBJECT
-     explicit QBuffer(QObject *parent = 0);
-     QBuffer(QByteArray *buf, QObject *parent = 0);
+     explicit QBuffer(QObject *parent = Q_NULLPTR);
+     QBuffer(QByteArray *buf, QObject *parent = Q_NULLPTR);
 #else
      QBuffer();
      explicit QBuffer(QByteArray *buf);
diff --git a/src/corelib/io/qfile.h b/src/corelib/io/qfile.h
index 35a73680af..4eac710d4c 100644
--- a/src/corelib/io/qfile.h
+++ b/src/corelib/io/qfile.h
@@ -134,7 +134,7 @@ protected:
 #ifdef QT_NO_QOBJECT
     QFile(QFilePrivate &dd);
 #else
-    QFile(QFilePrivate &dd, QObject *parent = 0);
+    QFile(QFilePrivate &dd, QObject *parent = Q_NULLPTR);
 #endif
 
 private:
diff --git a/src/corelib/io/qfiledevice.h b/src/corelib/io/qfiledevice.h
index e9320d8d31..afa42bd86b 100644
--- a/src/corelib/io/qfiledevice.h
+++ b/src/corelib/io/qfiledevice.h
@@ -119,7 +119,7 @@ protected:
     QFileDevice(QFileDevicePrivate &dd);
 #else
     explicit QFileDevice(QObject *parent);
-    QFileDevice(QFileDevicePrivate &dd, QObject *parent = 0);
+    QFileDevice(QFileDevicePrivate &dd, QObject *parent = Q_NULLPTR);
 #endif
 
     qint64 readData(char *data, qint64 maxlen) Q_DECL_OVERRIDE;
diff --git a/src/corelib/io/qfileselector.h b/src/corelib/io/qfileselector.h
index 967d5eee75..9ee3588780 100644
--- a/src/corelib/io/qfileselector.h
+++ b/src/corelib/io/qfileselector.h
@@ -44,7 +44,7 @@ class Q_CORE_EXPORT QFileSelector : public QObject
 {
     Q_OBJECT
 public:
-    explicit QFileSelector(QObject *parent = 0);
+    explicit QFileSelector(QObject *parent = Q_NULLPTR);
     ~QFileSelector();
 
     QString select(const QString &filePath) const;
diff --git a/src/corelib/io/qfilesystemwatcher.h b/src/corelib/io/qfilesystemwatcher.h
index 13d1782913..095b50d1e5 100644
--- a/src/corelib/io/qfilesystemwatcher.h
+++ b/src/corelib/io/qfilesystemwatcher.h
@@ -49,8 +49,8 @@ class Q_CORE_EXPORT QFileSystemWatcher : public QObject
     Q_DECLARE_PRIVATE(QFileSystemWatcher)
 
 public:
-    QFileSystemWatcher(QObject *parent = 0);
-    QFileSystemWatcher(const QStringList &paths, QObject *parent = 0);
+    QFileSystemWatcher(QObject *parent = Q_NULLPTR);
+    QFileSystemWatcher(const QStringList &paths, QObject *parent = Q_NULLPTR);
     ~QFileSystemWatcher();
 
     bool addPath(const QString &file);
diff --git a/src/corelib/io/qiodevice.h b/src/corelib/io/qiodevice.h
index 4f45805fca..b62c8d266c 100644
--- a/src/corelib/io/qiodevice.h
+++ b/src/corelib/io/qiodevice.h
@@ -140,7 +140,7 @@ protected:
 #ifdef QT_NO_QOBJECT
     QIODevice(QIODevicePrivate &dd);
 #else
-    QIODevice(QIODevicePrivate &dd, QObject *parent = 0);
+    QIODevice(QIODevicePrivate &dd, QObject *parent = Q_NULLPTR);
 #endif
     virtual qint64 readData(char *data, qint64 maxlen) = 0;
     virtual qint64 readLineData(char *data, qint64 maxlen);
diff --git a/src/corelib/io/qprocess.h b/src/corelib/io/qprocess.h
index df9fa886c1..81b3ac81d0 100644
--- a/src/corelib/io/qprocess.h
+++ b/src/corelib/io/qprocess.h
@@ -143,7 +143,7 @@ public:
     };
     Q_ENUM(ExitStatus)
 
-    explicit QProcess(QObject *parent = 0);
+    explicit QProcess(QObject *parent = Q_NULLPTR);
     virtual ~QProcess();
 
     void start(const QString &program, const QStringList &arguments, OpenMode mode = ReadWrite);
@@ -222,7 +222,7 @@ public:
 #if defined(Q_QDOC)
                               = QString()
 #endif
-                              , qint64 *pid = 0);
+                              , qint64 *pid = Q_NULLPTR);
 #if !defined(Q_QDOC)
     static bool startDetached(const QString &program, const QStringList &arguments); // ### Qt6: merge overloads
 #endif
diff --git a/src/corelib/io/qsavefile.h b/src/corelib/io/qsavefile.h
index 3f5f09bf5c..085378ed4e 100644
--- a/src/corelib/io/qsavefile.h
+++ b/src/corelib/io/qsavefile.h
@@ -58,7 +58,7 @@ class Q_CORE_EXPORT QSaveFile : public QFileDevice
 public:
 
     explicit QSaveFile(const QString &name);
-    explicit QSaveFile(QObject *parent = 0);
+    explicit QSaveFile(QObject *parent = Q_NULLPTR);
     explicit QSaveFile(const QString &name, QObject *parent);
     ~QSaveFile();
 
diff --git a/src/corelib/io/qsettings.h b/src/corelib/io/qsettings.h
index f7a7bdbb19..8f41273ffa 100644
--- a/src/corelib/io/qsettings.h
+++ b/src/corelib/io/qsettings.h
@@ -105,13 +105,13 @@ public:
 
 #ifndef QT_NO_QOBJECT
     explicit QSettings(const QString &organization,
-                       const QString &application = QString(), QObject *parent = 0);
+                       const QString &application = QString(), QObject *parent = Q_NULLPTR);
     QSettings(Scope scope, const QString &organization,
-              const QString &application = QString(), QObject *parent = 0);
+              const QString &application = QString(), QObject *parent = Q_NULLPTR);
     QSettings(Format format, Scope scope, const QString &organization,
-              const QString &application = QString(), QObject *parent = 0);
-    QSettings(const QString &fileName, Format format, QObject *parent = 0);
-    explicit QSettings(QObject *parent = 0);
+              const QString &application = QString(), QObject *parent = Q_NULLPTR);
+    QSettings(const QString &fileName, Format format, QObject *parent = Q_NULLPTR);
+    explicit QSettings(QObject *parent = Q_NULLPTR);
 #else
     explicit QSettings(const QString &organization,
                        const QString &application = QString());
diff --git a/src/corelib/itemmodels/qabstractitemmodel.h b/src/corelib/itemmodels/qabstractitemmodel.h
index dec290d9e3..096e67c513 100644
--- a/src/corelib/itemmodels/qabstractitemmodel.h
+++ b/src/corelib/itemmodels/qabstractitemmodel.h
@@ -49,7 +49,7 @@ class Q_CORE_EXPORT QModelIndex
 {
     friend class QAbstractItemModel;
 public:
-    Q_DECL_CONSTEXPR inline QModelIndex() Q_DECL_NOTHROW : r(-1), c(-1), i(0), m(0) {}
+    Q_DECL_CONSTEXPR inline QModelIndex() Q_DECL_NOTHROW : r(-1), c(-1), i(0), m(Q_NULLPTR) {}
     // compiler-generated copy/move ctors/assignment operators are fine!
     Q_DECL_CONSTEXPR inline int row() const Q_DECL_NOTHROW { return r; }
     Q_DECL_CONSTEXPR inline int column() const Q_DECL_NOTHROW { return c; }
@@ -61,7 +61,7 @@ public:
     inline QVariant data(int role = Qt::DisplayRole) const;
     inline Qt::ItemFlags flags() const;
     Q_DECL_CONSTEXPR inline const QAbstractItemModel *model() const Q_DECL_NOTHROW { return m; }
-    Q_DECL_CONSTEXPR inline bool isValid() const Q_DECL_NOTHROW { return (r >= 0) && (c >= 0) && (m != 0); }
+    Q_DECL_CONSTEXPR inline bool isValid() const Q_DECL_NOTHROW { return (r >= 0) && (c >= 0) && (m != Q_NULLPTR); }
     Q_DECL_CONSTEXPR inline bool operator==(const QModelIndex &other) const Q_DECL_NOTHROW
         { return (other.r == r) && (other.i == i) && (other.c == c) && (other.m == m); }
     Q_DECL_CONSTEXPR inline bool operator!=(const QModelIndex &other) const Q_DECL_NOTHROW
@@ -161,7 +161,7 @@ class Q_CORE_EXPORT QAbstractItemModel : public QObject
     friend class QIdentityProxyModel;
 public:
 
-    explicit QAbstractItemModel(QObject *parent = 0);
+    explicit QAbstractItemModel(QObject *parent = Q_NULLPTR);
     virtual ~QAbstractItemModel();
 
     Q_INVOKABLE bool hasIndex(int row, int column, const QModelIndex &parent = QModelIndex()) const;
@@ -276,9 +276,9 @@ protected Q_SLOTS:
     void resetInternalData();
 
 protected:
-    QAbstractItemModel(QAbstractItemModelPrivate &dd, QObject *parent = 0);
+    QAbstractItemModel(QAbstractItemModelPrivate &dd, QObject *parent = Q_NULLPTR);
 
-    inline QModelIndex createIndex(int row, int column, void *data = 0) const;
+    inline QModelIndex createIndex(int row, int column, void *data = Q_NULLPTR) const;
     inline QModelIndex createIndex(int row, int column, quintptr id) const;
 
     void encodeData(const QModelIndexList &indexes, QDataStream &stream) const;
@@ -357,7 +357,7 @@ class Q_CORE_EXPORT QAbstractTableModel : public QAbstractItemModel
     Q_OBJECT
 
 public:
-    explicit QAbstractTableModel(QObject *parent = 0);
+    explicit QAbstractTableModel(QObject *parent = Q_NULLPTR);
     ~QAbstractTableModel();
 
     QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
@@ -383,7 +383,7 @@ class Q_CORE_EXPORT QAbstractListModel : public QAbstractItemModel
     Q_OBJECT
 
 public:
-    explicit QAbstractListModel(QObject *parent = 0);
+    explicit QAbstractListModel(QObject *parent = Q_NULLPTR);
     ~QAbstractListModel();
 
     QModelIndex index(int row, int column = 0, const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
diff --git a/src/corelib/itemmodels/qabstractproxymodel.h b/src/corelib/itemmodels/qabstractproxymodel.h
index dc8d2d4dc8..a4cb74830b 100644
--- a/src/corelib/itemmodels/qabstractproxymodel.h
+++ b/src/corelib/itemmodels/qabstractproxymodel.h
@@ -50,7 +50,7 @@ class Q_CORE_EXPORT QAbstractProxyModel : public QAbstractItemModel
     Q_PROPERTY(QAbstractItemModel* sourceModel READ sourceModel WRITE setSourceModel NOTIFY sourceModelChanged)
 
 public:
-    explicit QAbstractProxyModel(QObject *parent = 0);
+    explicit QAbstractProxyModel(QObject *parent = Q_NULLPTR);
     ~QAbstractProxyModel();
 
     virtual void setSourceModel(QAbstractItemModel *sourceModel);
diff --git a/src/corelib/itemmodels/qidentityproxymodel.h b/src/corelib/itemmodels/qidentityproxymodel.h
index e4587cb386..7578f8d380 100644
--- a/src/corelib/itemmodels/qidentityproxymodel.h
+++ b/src/corelib/itemmodels/qidentityproxymodel.h
@@ -48,7 +48,7 @@ class Q_CORE_EXPORT QIdentityProxyModel : public QAbstractProxyModel
 {
     Q_OBJECT
 public:
-    explicit QIdentityProxyModel(QObject* parent = 0);
+    explicit QIdentityProxyModel(QObject* parent = Q_NULLPTR);
     ~QIdentityProxyModel();
 
     int columnCount(const QModelIndex& parent = QModelIndex()) const Q_DECL_OVERRIDE;
diff --git a/src/corelib/itemmodels/qitemselectionmodel.h b/src/corelib/itemmodels/qitemselectionmodel.h
index 4fe836c098..1d98110a4e 100644
--- a/src/corelib/itemmodels/qitemselectionmodel.h
+++ b/src/corelib/itemmodels/qitemselectionmodel.h
@@ -170,7 +170,7 @@ public:
     Q_DECLARE_FLAGS(SelectionFlags, SelectionFlag)
     Q_FLAG(SelectionFlags)
 
-    explicit QItemSelectionModel(QAbstractItemModel *model = 0);
+    explicit QItemSelectionModel(QAbstractItemModel *model = Q_NULLPTR);
     explicit QItemSelectionModel(QAbstractItemModel *model, QObject *parent);
     virtual ~QItemSelectionModel();
 
diff --git a/src/corelib/itemmodels/qsortfilterproxymodel.h b/src/corelib/itemmodels/qsortfilterproxymodel.h
index a08d7c6416..4be5aedd48 100644
--- a/src/corelib/itemmodels/qsortfilterproxymodel.h
+++ b/src/corelib/itemmodels/qsortfilterproxymodel.h
@@ -63,7 +63,7 @@ class Q_CORE_EXPORT QSortFilterProxyModel : public QAbstractProxyModel
     Q_PROPERTY(int filterRole READ filterRole WRITE setFilterRole)
 
 public:
-    explicit QSortFilterProxyModel(QObject *parent = 0);
+    explicit QSortFilterProxyModel(QObject *parent = Q_NULLPTR);
     ~QSortFilterProxyModel();
 
     void setSourceModel(QAbstractItemModel *sourceModel) Q_DECL_OVERRIDE;
diff --git a/src/corelib/itemmodels/qstringlistmodel.h b/src/corelib/itemmodels/qstringlistmodel.h
index 973007995b..a1cb923dbb 100644
--- a/src/corelib/itemmodels/qstringlistmodel.h
+++ b/src/corelib/itemmodels/qstringlistmodel.h
@@ -46,8 +46,8 @@ class Q_CORE_EXPORT QStringListModel : public QAbstractListModel
 {
     Q_OBJECT
 public:
-    explicit QStringListModel(QObject *parent = 0);
-    explicit QStringListModel(const QStringList &strings, QObject *parent = 0);
+    explicit QStringListModel(QObject *parent = Q_NULLPTR);
+    explicit QStringListModel(const QStringList &strings, QObject *parent = Q_NULLPTR);
 
     int rowCount(const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
     QModelIndex sibling(int row, int column, const QModelIndex &idx) const Q_DECL_OVERRIDE;
diff --git a/src/corelib/json/qjsonarray.h b/src/corelib/json/qjsonarray.h
index 6148642106..311753d977 100644
--- a/src/corelib/json/qjsonarray.h
+++ b/src/corelib/json/qjsonarray.h
@@ -107,7 +107,7 @@ public:
         typedef QJsonValueRef reference;
         typedef QJsonValueRefPtr pointer;
 
-        inline iterator() : a(0), i(0) { }
+        inline iterator() : a(Q_NULLPTR), i(0) { }
         explicit inline iterator(QJsonArray *array, int index) : a(array), i(index) { }
 
         inline QJsonValueRef operator*() const { return QJsonValueRef(a, i); }
@@ -152,7 +152,7 @@ public:
         typedef QJsonValue reference;
         typedef QJsonValuePtr pointer;
 
-        inline const_iterator() : a(0), i(0) { }
+        inline const_iterator() : a(Q_NULLPTR), i(0) { }
         explicit inline const_iterator(const QJsonArray *array, int index) : a(array), i(index) { }
         inline const_iterator(const const_iterator &o) : a(o.a), i(o.i) {}
         inline const_iterator(const iterator &o) : a(o.a), i(o.i) {}
diff --git a/src/corelib/json/qjsondocument.h b/src/corelib/json/qjsondocument.h
index 285b42c6c8..d7a88b2f15 100644
--- a/src/corelib/json/qjsondocument.h
+++ b/src/corelib/json/qjsondocument.h
@@ -106,7 +106,7 @@ public:
         Compact
     };
 
-    static QJsonDocument fromJson(const QByteArray &json, QJsonParseError *error = 0);
+    static QJsonDocument fromJson(const QByteArray &json, QJsonParseError *error = Q_NULLPTR);
 
 #ifdef Q_QDOC
     QByteArray toJson(JsonFormat format = Indented) const;
diff --git a/src/corelib/json/qjsonobject.h b/src/corelib/json/qjsonobject.h
index 5f24ac3ac8..19c938fd83 100644
--- a/src/corelib/json/qjsonobject.h
+++ b/src/corelib/json/qjsonobject.h
@@ -105,7 +105,7 @@ public:
         typedef QJsonValue value_type;
         typedef QJsonValueRef reference;
 
-        Q_DECL_CONSTEXPR inline iterator() : o(0), i(0) {}
+        Q_DECL_CONSTEXPR inline iterator() : o(Q_NULLPTR), i(0) {}
         Q_DECL_CONSTEXPR inline iterator(QJsonObject *obj, int index) : o(obj), i(index) {}
 
         inline QString key() const { return o->keyAt(i); }
@@ -147,7 +147,7 @@ public:
         typedef QJsonValue value_type;
         typedef QJsonValue reference;
 
-        Q_DECL_CONSTEXPR inline const_iterator() : o(0), i(0) {}
+        Q_DECL_CONSTEXPR inline const_iterator() : o(Q_NULLPTR), i(0) {}
         Q_DECL_CONSTEXPR inline const_iterator(const QJsonObject *obj, int index)
             : o(obj), i(index) {}
         inline const_iterator(const iterator &other)
diff --git a/src/corelib/kernel/qabstracteventdispatcher.h b/src/corelib/kernel/qabstracteventdispatcher.h
index c80f7d3d08..eb357cefe5 100644
--- a/src/corelib/kernel/qabstracteventdispatcher.h
+++ b/src/corelib/kernel/qabstracteventdispatcher.h
@@ -64,10 +64,10 @@ public:
         { }
     };
 
-    explicit QAbstractEventDispatcher(QObject *parent = 0);
+    explicit QAbstractEventDispatcher(QObject *parent = Q_NULLPTR);
     ~QAbstractEventDispatcher();
 
-    static QAbstractEventDispatcher *instance(QThread *thread = 0);
+    static QAbstractEventDispatcher *instance(QThread *thread = Q_NULLPTR);
 
     virtual bool processEvents(QEventLoop::ProcessEventsFlags flags) = 0;
     virtual bool hasPendingEvents() = 0; // ### Qt6: remove, mark final or make protected
diff --git a/src/corelib/kernel/qcoreapplication.h b/src/corelib/kernel/qcoreapplication.h
index 1cd835daae..1009fe8439 100644
--- a/src/corelib/kernel/qcoreapplication.h
+++ b/src/corelib/kernel/qcoreapplication.h
@@ -117,7 +117,7 @@ public:
 
     static bool sendEvent(QObject *receiver, QEvent *event);
     static void postEvent(QObject *receiver, QEvent *event, int priority = Qt::NormalEventPriority);
-    static void sendPostedEvents(QObject *receiver = 0, int event_type = 0);
+    static void sendPostedEvents(QObject *receiver = Q_NULLPTR, int event_type = 0);
     static void removePostedEvents(QObject *receiver, int eventType = 0);
 #if QT_DEPRECATED_SINCE(5, 3)
     QT_DEPRECATED static bool hasPendingEvents();
@@ -149,7 +149,7 @@ public:
 
     static QString translate(const char * context,
                              const char * key,
-                             const char * disambiguation = 0,
+                             const char * disambiguation = Q_NULLPTR,
                              int n = -1);
 #if QT_DEPRECATED_SINCE(5, 0)
     enum Encoding { UnicodeUTF8, Latin1, DefaultCodec = UnicodeUTF8, CodecForTr = UnicodeUTF8 };
@@ -231,13 +231,13 @@ inline bool QCoreApplication::sendSpontaneousEvent(QObject *receiver, QEvent *ev
 #  define QT_DECLARE_DEPRECATED_TR_FUNCTIONS(context)
 #else
 #  define QT_DECLARE_DEPRECATED_TR_FUNCTIONS(context) \
-    QT_DEPRECATED static inline QString trUtf8(const char *sourceText, const char *disambiguation = 0, int n = -1) \
+    QT_DEPRECATED static inline QString trUtf8(const char *sourceText, const char *disambiguation = Q_NULLPTR, int n = -1) \
         { return QCoreApplication::translate(#context, sourceText, disambiguation, n); }
 #endif
 
 #define Q_DECLARE_TR_FUNCTIONS(context) \
 public: \
-    static inline QString tr(const char *sourceText, const char *disambiguation = 0, int n = -1) \
+    static inline QString tr(const char *sourceText, const char *disambiguation = Q_NULLPTR, int n = -1) \
         { return QCoreApplication::translate(#context, sourceText, disambiguation, n); } \
     QT_DECLARE_DEPRECATED_TR_FUNCTIONS(context) \
 private:
diff --git a/src/corelib/kernel/qeventloop.h b/src/corelib/kernel/qeventloop.h
index 99c0cd50ff..375a63abdd 100644
--- a/src/corelib/kernel/qeventloop.h
+++ b/src/corelib/kernel/qeventloop.h
@@ -47,7 +47,7 @@ class Q_CORE_EXPORT QEventLoop : public QObject
     Q_DECLARE_PRIVATE(QEventLoop)
 
 public:
-    explicit QEventLoop(QObject *parent = 0);
+    explicit QEventLoop(QObject *parent = Q_NULLPTR);
     ~QEventLoop();
 
     enum ProcessEventsFlag {
diff --git a/src/corelib/kernel/qmetaobject.h b/src/corelib/kernel/qmetaobject.h
index b522a211bb..1a282d3261 100644
--- a/src/corelib/kernel/qmetaobject.h
+++ b/src/corelib/kernel/qmetaobject.h
@@ -48,7 +48,7 @@ template <typename T> class QList;
 class Q_CORE_EXPORT QMetaMethod
 {
 public:
-    Q_DECL_CONSTEXPR inline QMetaMethod() : mobj(0),handle(0) {}
+    Q_DECL_CONSTEXPR inline QMetaMethod() : mobj(Q_NULLPTR), handle(0) {}
 
     QByteArray methodSignature() const;
     QByteArray name() const;
@@ -74,7 +74,7 @@ public:
     bool invoke(QObject *object,
                 Qt::ConnectionType connectionType,
                 QGenericReturnArgument returnValue,
-                QGenericArgument val0 = QGenericArgument(0),
+                QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                 QGenericArgument val1 = QGenericArgument(),
                 QGenericArgument val2 = QGenericArgument(),
                 QGenericArgument val3 = QGenericArgument(),
@@ -86,7 +86,7 @@ public:
                 QGenericArgument val9 = QGenericArgument()) const;
     inline bool invoke(QObject *object,
                        QGenericReturnArgument returnValue,
-                       QGenericArgument val0 = QGenericArgument(0),
+                       QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                        QGenericArgument val1 = QGenericArgument(),
                        QGenericArgument val2 = QGenericArgument(),
                        QGenericArgument val3 = QGenericArgument(),
@@ -102,7 +102,7 @@ public:
     }
     inline bool invoke(QObject *object,
                        Qt::ConnectionType connectionType,
-                       QGenericArgument val0 = QGenericArgument(0),
+                       QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                        QGenericArgument val1 = QGenericArgument(),
                        QGenericArgument val2 = QGenericArgument(),
                        QGenericArgument val3 = QGenericArgument(),
@@ -117,7 +117,7 @@ public:
                       val0, val1, val2, val3, val4, val5, val6, val7, val8, val9);
     }
     inline bool invoke(QObject *object,
-                       QGenericArgument val0 = QGenericArgument(0),
+                       QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                        QGenericArgument val1 = QGenericArgument(),
                        QGenericArgument val2 = QGenericArgument(),
                        QGenericArgument val3 = QGenericArgument(),
@@ -134,7 +134,7 @@ public:
 
     bool invokeOnGadget(void *gadget,
                 QGenericReturnArgument returnValue,
-                QGenericArgument val0 = QGenericArgument(0),
+                QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                 QGenericArgument val1 = QGenericArgument(),
                 QGenericArgument val2 = QGenericArgument(),
                 QGenericArgument val3 = QGenericArgument(),
@@ -145,7 +145,7 @@ public:
                 QGenericArgument val8 = QGenericArgument(),
                 QGenericArgument val9 = QGenericArgument()) const;
     inline bool invokeOnGadget(void *gadget,
-                       QGenericArgument val0 = QGenericArgument(0),
+                       QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                        QGenericArgument val1 = QGenericArgument(),
                        QGenericArgument val2 = QGenericArgument(),
                        QGenericArgument val3 = QGenericArgument(),
@@ -160,7 +160,7 @@ public:
                       val0, val1, val2, val3, val4, val5, val6, val7, val8, val9);
     }
 
-    inline bool isValid() const { return mobj != 0; }
+    inline bool isValid() const { return mobj != Q_NULLPTR; }
 
 #ifdef Q_QDOC
     static QMetaMethod fromSignal(PointerToMemberFunction signal);
@@ -204,7 +204,7 @@ inline bool operator!=(const QMetaMethod &m1, const QMetaMethod &m2)
 class Q_CORE_EXPORT QMetaEnum
 {
 public:
-    Q_DECL_CONSTEXPR inline QMetaEnum() : mobj(0),handle(0) {}
+    Q_DECL_CONSTEXPR inline QMetaEnum() : mobj(Q_NULLPTR), handle(0) {}
 
     const char *name() const;
     bool isFlag() const;
@@ -215,14 +215,14 @@ public:
 
     const char *scope() const;
 
-    int keyToValue(const char *key, bool *ok = 0) const;
+    int keyToValue(const char *key, bool *ok = Q_NULLPTR) const;
     const char* valueToKey(int value) const;
-    int keysToValue(const char * keys, bool *ok = 0) const;
+    int keysToValue(const char * keys, bool *ok = Q_NULLPTR) const;
     QByteArray valueToKeys(int value) const;
 
     inline const QMetaObject *enclosingMetaObject() const { return mobj; }
 
-    inline bool isValid() const { return name() != 0; }
+    inline bool isValid() const { return name() != Q_NULLPTR; }
 
     template<typename T> static QMetaEnum fromType() {
         Q_STATIC_ASSERT_X(QtPrivate::IsQEnumHelper<T>::Value,
@@ -253,11 +253,11 @@ public:
     bool isReadable() const;
     bool isWritable() const;
     bool isResettable() const;
-    bool isDesignable(const QObject *obj = 0) const;
-    bool isScriptable(const QObject *obj = 0) const;
-    bool isStored(const QObject *obj = 0) const;
-    bool isEditable(const QObject *obj = 0) const;
-    bool isUser(const QObject *obj = 0) const;
+    bool isDesignable(const QObject *obj = Q_NULLPTR) const;
+    bool isScriptable(const QObject *obj = Q_NULLPTR) const;
+    bool isStored(const QObject *obj = Q_NULLPTR) const;
+    bool isEditable(const QObject *obj = Q_NULLPTR) const;
+    bool isUser(const QObject *obj = Q_NULLPTR) const;
     bool isConstant() const;
     bool isFinal() const;
 
@@ -297,7 +297,7 @@ private:
 class Q_CORE_EXPORT QMetaClassInfo
 {
 public:
-    Q_DECL_CONSTEXPR inline QMetaClassInfo() : mobj(0),handle(0) {}
+    Q_DECL_CONSTEXPR inline QMetaClassInfo() : mobj(Q_NULLPTR), handle(0) {}
     const char *name() const;
     const char *value() const;
     inline const QMetaObject *enclosingMetaObject() const { return mobj; }
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index 1b214e9f74..988630d90f 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -229,7 +229,7 @@ struct AbstractDebugStreamFunction
 {
     typedef void (*Stream)(const AbstractDebugStreamFunction *, QDebug&, const void *);
     typedef void (*Destroy)(AbstractDebugStreamFunction *);
-    explicit AbstractDebugStreamFunction(Stream s = 0, Destroy d = 0)
+    explicit AbstractDebugStreamFunction(Stream s = Q_NULLPTR, Destroy d = Q_NULLPTR)
         : stream(s), destroy(d) {}
     Q_DISABLE_COPY(AbstractDebugStreamFunction)
     Stream stream;
@@ -259,7 +259,7 @@ struct AbstractComparatorFunction
     typedef bool (*LessThan)(const AbstractComparatorFunction *, const void *, const void *);
     typedef bool (*Equals)(const AbstractComparatorFunction *, const void *, const void *);
     typedef void (*Destroy)(AbstractComparatorFunction *);
-    explicit AbstractComparatorFunction(LessThan lt = 0, Equals e = 0, Destroy d = 0)
+    explicit AbstractComparatorFunction(LessThan lt = Q_NULLPTR, Equals e = Q_NULLPTR, Destroy d = Q_NULLPTR)
         : lessThan(lt), equals(e), destroy(d) {}
     Q_DISABLE_COPY(AbstractComparatorFunction)
     LessThan lessThan;
@@ -296,7 +296,7 @@ template<typename T>
 struct BuiltInEqualsComparatorFunction : public AbstractComparatorFunction
 {
     BuiltInEqualsComparatorFunction()
-        : AbstractComparatorFunction(0, equals, destroy) {}
+        : AbstractComparatorFunction(Q_NULLPTR, equals, destroy) {}
     static bool equals(const AbstractComparatorFunction *, const void *l, const void *r)
     {
         const T *lhs = static_cast<const T *>(l);
@@ -313,7 +313,7 @@ struct BuiltInEqualsComparatorFunction : public AbstractComparatorFunction
 struct AbstractConverterFunction
 {
     typedef bool (*Converter)(const AbstractConverterFunction *, const void *, void*);
-    explicit AbstractConverterFunction(Converter c = 0)
+    explicit AbstractConverterFunction(Converter c = Q_NULLPTR)
         : convert(c) {}
     Q_DISABLE_COPY(AbstractConverterFunction)
     Converter convert;
@@ -510,9 +510,9 @@ public:
     static TypeFlags typeFlags(int type);
     static const QMetaObject *metaObjectForType(int type);
     static bool isRegistered(int type);
-    static void *create(int type, const void *copy = 0);
+    static void *create(int type, const void *copy = Q_NULLPTR);
 #if QT_DEPRECATED_SINCE(5, 0)
-    QT_DEPRECATED static void *construct(int type, const void *copy = 0)
+    QT_DEPRECATED static void *construct(int type, const void *copy = Q_NULLPTR)
     { return create(type, copy); }
 #endif
     static void destroy(int type, void *data);
@@ -533,9 +533,9 @@ public:
     inline TypeFlags flags() const;
     inline const QMetaObject *metaObject() const;
 
-    inline void *create(const void *copy = 0) const;
+    inline void *create(const void *copy = Q_NULLPTR) const;
     inline void destroy(void *data) const;
-    inline void *construct(void *where, const void *copy = 0) const;
+    inline void *construct(void *where, const void *copy = Q_NULLPTR) const;
     inline void destruct(void *data) const;
 
 public:
@@ -611,7 +611,7 @@ public:
         return registerConverterFunction(&f, fromTypeId, toTypeId);
     }
 
-    // member function as in "double QString::toDouble(bool *ok = 0) const"
+    // member function as in "double QString::toDouble(bool *ok = Q_NULLPTR) const"
     template<typename From, typename To>
     static bool registerConverter(To(From::*function)(bool*) const)
     {
@@ -674,9 +674,9 @@ private:
     uint sizeExtended() const;
     QMetaType::TypeFlags flagsExtended() const;
     const QMetaObject *metaObjectExtended() const;
-    void *createExtended(const void *copy = 0) const;
+    void *createExtended(const void *copy = Q_NULLPTR) const;
     void destroyExtended(void *data) const;
-    void *constructExtended(void *where, const void *copy = 0) const;
+    void *constructExtended(void *where, const void *copy = Q_NULLPTR) const;
     void destructExtended(void *data) const;
 
     static bool registerComparatorFunction(const QtPrivate::AbstractComparatorFunction *f, int type);
@@ -771,7 +771,7 @@ struct QMetaTypeFunctionHelper {
 template <typename T>
 struct QMetaTypeFunctionHelper<T, /* Accepted */ false> {
     static void Destruct(void *) {}
-    static void *Construct(void *, const void *) { return 0; }
+    static void *Construct(void *, const void *) { return Q_NULLPTR; }
 #ifndef QT_NO_DATASTREAM
     static void Save(QDataStream &, const void *) {}
     static void Load(QDataStream &, void *) {}
@@ -1009,7 +1009,7 @@ public:
 public:
     template<class T> QSequentialIterableImpl(const T*p)
       : _iterable(p)
-      , _iterator(0)
+      , _iterator(Q_NULLPTR)
       , _metaType_id(qMetaTypeId<typename T::value_type>())
       , _metaType_flags(QTypeInfo<typename T::value_type>::isPointer)
       , _iteratorCapabilities(ContainerAPI<T>::IteratorCapabilities)
@@ -1026,20 +1026,20 @@ public:
     }
 
     QSequentialIterableImpl()
-      : _iterable(0)
-      , _iterator(0)
+      : _iterable(Q_NULLPTR)
+      , _iterator(Q_NULLPTR)
       , _metaType_id(QMetaType::UnknownType)
       , _metaType_flags(0)
       , _iteratorCapabilities(0)
-      , _size(0)
-      , _at(0)
-      , _moveToBegin(0)
-      , _moveToEnd(0)
-      , _advance(0)
-      , _get(0)
-      , _destroyIter(0)
-      , _equalIter(0)
-      , _copyIter(0)
+      , _size(Q_NULLPTR)
+      , _at(Q_NULLPTR)
+      , _moveToBegin(Q_NULLPTR)
+      , _moveToEnd(Q_NULLPTR)
+      , _advance(Q_NULLPTR)
+      , _get(Q_NULLPTR)
+      , _destroyIter(Q_NULLPTR)
+      , _equalIter(Q_NULLPTR)
+      , _copyIter(Q_NULLPTR)
     {
     }
 
@@ -1195,21 +1195,21 @@ public:
     }
 
     QAssociativeIterableImpl()
-      : _iterable(0)
+      : _iterable(Q_NULLPTR)
       , _metaType_id_key(QMetaType::UnknownType)
       , _metaType_flags_key(0)
       , _metaType_id_value(QMetaType::UnknownType)
       , _metaType_flags_value(0)
-      , _size(0)
-      , _find(0)
-      , _begin(0)
-      , _end(0)
-      , _advance(0)
-      , _getKey(0)
-      , _getValue(0)
-      , _destroyIter(0)
-      , _equalIter(0)
-      , _copyIter(0)
+      , _size(Q_NULLPTR)
+      , _find(Q_NULLPTR)
+      , _begin(Q_NULLPTR)
+      , _end(Q_NULLPTR)
+      , _advance(Q_NULLPTR)
+      , _getKey(Q_NULLPTR)
+      , _getValue(Q_NULLPTR)
+      , _destroyIter(Q_NULLPTR)
+      , _equalIter(Q_NULLPTR)
+      , _copyIter(Q_NULLPTR)
     {
     }
 
@@ -1277,9 +1277,9 @@ public:
     }
 
     QPairVariantInterfaceImpl()
-      : _pair(0)
-      , _getFirst(0)
-      , _getSecond(0)
+      : _pair(Q_NULLPTR)
+      , _getFirst(Q_NULLPTR)
+      , _getSecond(Q_NULLPTR)
     {
     }
 
@@ -1354,7 +1354,7 @@ namespace QtPrivate
 #endif
         static no_type checkType(...);
         Q_STATIC_ASSERT_X(sizeof(T), "Type argument of Q_DECLARE_METATYPE(T*) must be fully defined");
-        enum { Value = sizeof(checkType(static_cast<T*>(0))) == sizeof(yes_type) };
+        enum { Value = sizeof(checkType(static_cast<T*>(Q_NULLPTR))) == sizeof(yes_type) };
     };
 
     template<typename T, typename Enable = void>
@@ -1391,7 +1391,7 @@ QT_WARNING_POP
     template<typename T, typename Enable = void>
     struct MetaObjectForType
     {
-        static inline const QMetaObject *value() { return 0; }
+        static inline const QMetaObject *value() { return Q_NULLPTR; }
     };
     template<>
     struct MetaObjectForType<void>
@@ -1692,7 +1692,7 @@ int qRegisterNormalizedMetaType(const QT_PREPEND_NAMESPACE(QByteArray) &normaliz
 template <typename T>
 int qRegisterMetaType(const char *typeName
 #ifndef Q_QDOC
-    , T * dummy = 0
+    , T * dummy = Q_NULLPTR
     , typename QtPrivate::MetaTypeDefinedHelper<T, QMetaTypeId2<T>::Defined && !QMetaTypeId2<T>::IsBuiltIn>::DefinedType defined = QtPrivate::MetaTypeDefinedHelper<T, QMetaTypeId2<T>::Defined && !QMetaTypeId2<T>::IsBuiltIn>::Defined
 #endif
 )
@@ -1709,7 +1709,7 @@ int qRegisterMetaType(const char *typeName
 template <typename T>
 void qRegisterMetaTypeStreamOperators(const char *typeName
 #ifndef Q_QDOC
-    , T * /* dummy */ = 0
+    , T * /* dummy */ = Q_NULLPTR
 #endif
 )
 {
@@ -2095,7 +2095,7 @@ inline QMetaType::QMetaType(const ExtensionFlag extensionFlags, const QMetaTypeI
     , m_loadOp(loadOp)
     , m_constructor(constructor)
     , m_destructor(destructor)
-    , m_extension(0)
+    , m_extension(Q_NULLPTR)
     , m_size(size)
     , m_typeFlags(theTypeFlags)
     , m_extensionFlags(extensionFlags)
diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index 5f61dd984f..64c5b58fd4 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -110,23 +110,23 @@ class Q_CORE_EXPORT QObject
     Q_DECLARE_PRIVATE(QObject)
 
 public:
-    Q_INVOKABLE explicit QObject(QObject *parent=0);
+    Q_INVOKABLE explicit QObject(QObject *parent=Q_NULLPTR);
     virtual ~QObject();
 
     virtual bool event(QEvent *);
     virtual bool eventFilter(QObject *, QEvent *);
 
 #ifdef Q_QDOC
-    static QString tr(const char *sourceText, const char *comment = 0, int n = -1);
-    static QString trUtf8(const char *sourceText, const char *comment = 0, int n = -1);
+    static QString tr(const char *sourceText, const char *comment = Q_NULLPTR, int n = -1);
+    static QString trUtf8(const char *sourceText, const char *comment = Q_NULLPTR, int n = -1);
     virtual const QMetaObject *metaObject() const;
     static const QMetaObject staticMetaObject;
 #endif
 #ifdef QT_NO_TRANSLATION
-    static QString tr(const char *sourceText, const char * = 0, int = -1)
+    static QString tr(const char *sourceText, const char * = Q_NULLPTR, int = -1)
         { return QString::fromUtf8(sourceText); }
 #if QT_DEPRECATED_SINCE(5, 0)
-    QT_DEPRECATED static QString trUtf8(const char *sourceText, const char * = 0, int = -1)
+    QT_DEPRECATED static QString trUtf8(const char *sourceText, const char * = Q_NULLPTR, int = -1)
         { return QString::fromUtf8(sourceText); }
 #endif
 #endif //QT_NO_TRANSLATION
@@ -228,7 +228,7 @@ public:
         Q_STATIC_ASSERT_X((QtPrivate::AreArgumentsCompatible<typename SlotType::ReturnType, typename SignalType::ReturnType>::value),
                           "Return type of the slot is not compatible with the return type of the signal.");
 
-        const int *types = 0;
+        const int *types = Q_NULLPTR;
         if (type == Qt::QueuedConnection || type == Qt::BlockingQueuedConnection)
             types = QtPrivate::ConnectionTypes<typename SignalType::Arguments>::types();
 
@@ -268,11 +268,11 @@ public:
         Q_STATIC_ASSERT_X((QtPrivate::AreArgumentsCompatible<typename SlotType::ReturnType, typename SignalType::ReturnType>::value),
                           "Return type of the slot is not compatible with the return type of the signal.");
 
-        const int *types = 0;
+        const int *types = Q_NULLPTR;
         if (type == Qt::QueuedConnection || type == Qt::BlockingQueuedConnection)
             types = QtPrivate::ConnectionTypes<typename SignalType::Arguments>::types();
 
-        return connectImpl(sender, reinterpret_cast<void **>(&signal), context, 0,
+        return connectImpl(sender, reinterpret_cast<void **>(&signal), context, Q_NULLPTR,
                            new QtPrivate::QStaticSlotObject<Func2,
                                                  typename QtPrivate::List_Left<typename SignalType::Arguments, SlotType::ArgumentCount>::Value,
                                                  typename SignalType::ReturnType>(slot),
@@ -338,11 +338,11 @@ public:
         Q_STATIC_ASSERT_X(QtPrivate::HasQ_OBJECT_Macro<typename SignalType::Object>::Value,
                           "No Q_OBJECT in the class with the signal");
 
-        const int *types = 0;
+        const int *types = Q_NULLPTR;
         if (type == Qt::QueuedConnection || type == Qt::BlockingQueuedConnection)
             types = QtPrivate::ConnectionTypes<typename SignalType::Arguments>::types();
 
-        return connectImpl(sender, reinterpret_cast<void **>(&signal), context, 0,
+        return connectImpl(sender, reinterpret_cast<void **>(&signal), context, Q_NULLPTR,
                            new QtPrivate::QFunctorSlotObject<Func2, SlotArgumentCount,
                                 typename QtPrivate::List_Left<typename SignalType::Arguments, SlotArgumentCount>::Value,
                                 typename SignalType::ReturnType>(slot),
@@ -354,11 +354,11 @@ public:
                            const QObject *receiver, const char *member);
     static bool disconnect(const QObject *sender, const QMetaMethod &signal,
                            const QObject *receiver, const QMetaMethod &member);
-    inline bool disconnect(const char *signal = 0,
-                           const QObject *receiver = 0, const char *member = 0) const
+    inline bool disconnect(const char *signal = Q_NULLPTR,
+                           const QObject *receiver = Q_NULLPTR, const char *member = Q_NULLPTR) const
         { return disconnect(this, signal, receiver, member); }
-    inline bool disconnect(const QObject *receiver, const char *member = 0) const
-        { return disconnect(this, 0, receiver, member); }
+    inline bool disconnect(const QObject *receiver, const char *member = Q_NULLPTR) const
+        { return disconnect(this, Q_NULLPTR, receiver, member); }
     static bool disconnect(const QMetaObject::Connection &);
 
 #ifdef Q_QDOC
@@ -385,7 +385,7 @@ public:
     static inline bool disconnect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
                                   const QObject *receiver, void **zero)
     {
-        // This is the overload for when one wish to disconnect a signal from any slot. (slot=0)
+        // This is the overload for when one wish to disconnect a signal from any slot. (slot=Q_NULLPTR)
         // Since the function template parameter cannot be deduced from '0', we use a
         // dummy void ** parameter that must be equal to 0
         Q_ASSERT(!zero);
@@ -412,14 +412,14 @@ public:
 #endif // QT_NO_USERDATA
 
 Q_SIGNALS:
-    void destroyed(QObject * = 0);
+    void destroyed(QObject * = Q_NULLPTR);
     void objectNameChanged(const QString &objectName, QPrivateSignal);
 
 public:
     inline QObject *parent() const { return d_ptr->parent; }
 
     inline bool inherits(const char *classname) const
-        { return const_cast<QObject *>(this)->qt_metacast(classname) != 0; }
+        { return const_cast<QObject *>(this)->qt_metacast(classname) != Q_NULLPTR; }
 
 public Q_SLOTS:
     void deleteLater();
@@ -438,7 +438,7 @@ protected:
     virtual void disconnectNotify(const QMetaMethod &signal);
 
 protected:
-    QObject(QObjectPrivate &dd, QObject *parent = 0);
+    QObject(QObjectPrivate &dd, QObject *parent = Q_NULLPTR);
 
 protected:
     QScopedPointer<QObjectData> d_ptr;
@@ -529,16 +529,16 @@ inline T qobject_cast(const QObject *object)
 
 
 template <class T> inline const char * qobject_interface_iid()
-{ return 0; }
+{ return Q_NULLPTR; }
 
 #ifndef Q_MOC_RUN
 #  define Q_DECLARE_INTERFACE(IFace, IId) \
     template <> inline const char *qobject_interface_iid<IFace *>() \
     { return IId; } \
     template <> inline IFace *qobject_cast<IFace *>(QObject *object) \
-    { return reinterpret_cast<IFace *>((object ? object->qt_metacast(IId) : 0)); } \
+    { return reinterpret_cast<IFace *>((object ? object->qt_metacast(IId) : Q_NULLPTR)); } \
     template <> inline IFace *qobject_cast<IFace *>(const QObject *object) \
-    { return reinterpret_cast<IFace *>((object ? const_cast<QObject *>(object)->qt_metacast(IId) : 0)); }
+    { return reinterpret_cast<IFace *>((object ? const_cast<QObject *>(object)->qt_metacast(IId) : Q_NULLPTR)); }
 #endif // Q_MOC_RUN
 
 #ifndef QT_NO_DEBUG_STREAM
@@ -584,7 +584,7 @@ QSignalBlocker::QSignalBlocker(QSignalBlocker &&other) Q_DECL_NOTHROW
       m_blocked(other.m_blocked),
       m_inhibited(other.m_inhibited)
 {
-    other.m_o = 0;
+    other.m_o = Q_NULLPTR;
 }
 
 QSignalBlocker &QSignalBlocker::operator=(QSignalBlocker &&other) Q_DECL_NOTHROW
@@ -598,7 +598,7 @@ QSignalBlocker &QSignalBlocker::operator=(QSignalBlocker &&other) Q_DECL_NOTHROW
         m_blocked = other.m_blocked;
         m_inhibited = other.m_inhibited;
         // disable other:
-        other.m_o = 0;
+        other.m_o = Q_NULLPTR;
     }
     return *this;
 }
diff --git a/src/corelib/kernel/qobject_impl.h b/src/corelib/kernel/qobject_impl.h
index 4d9e42ba76..09d52584c4 100644
--- a/src/corelib/kernel/qobject_impl.h
+++ b/src/corelib/kernel/qobject_impl.h
@@ -90,9 +90,9 @@ namespace QtPrivate {
     { enum { Value = QMetaTypeId2<Arg>::Defined && TypesAreDeclaredMetaType<List<Tail...>>::Value }; };
 
     template <typename ArgList, bool Declared = TypesAreDeclaredMetaType<ArgList>::Value > struct ConnectionTypes
-    { static const int *types() { return 0; } };
+    { static const int *types() { return Q_NULLPTR; } };
     template <> struct ConnectionTypes<List<>, true>
-    { static const int *types() { return 0; } };
+    { static const int *types() { return Q_NULLPTR; } };
     template <typename... Args> struct ConnectionTypes<List<Args...>, true>
     { static const int *types() { static const int t[sizeof...(Args) + 1] = { (QtPrivate::QMetaTypeIdHelper<Args>::qt_metatype_id())..., 0 }; return t; } };
 #endif
@@ -118,10 +118,10 @@ namespace QtPrivate {
 
         inline int ref() Q_DECL_NOTHROW { return m_ref.ref(); }
         inline void destroyIfLastRef() Q_DECL_NOTHROW
-        { if (!m_ref.deref()) m_impl(Destroy, this, 0, 0, 0); }
+        { if (!m_ref.deref()) m_impl(Destroy, this, Q_NULLPTR, Q_NULLPTR, Q_NULLPTR); }
 
-        inline bool compare(void **a) { bool ret; m_impl(Compare, this, 0, a, &ret); return ret; }
-        inline void call(QObject *r, void **a)  { m_impl(Call,    this, r, a, 0); }
+        inline bool compare(void **a) { bool ret; m_impl(Compare, this, Q_NULLPTR, a, &ret); return ret; }
+        inline void call(QObject *r, void **a)  { m_impl(Call,    this, r, a, Q_NULLPTR); }
     protected:
         ~QSlotObjectBase() {}
     private:
diff --git a/src/corelib/kernel/qobjectdefs.h b/src/corelib/kernel/qobjectdefs.h
index a64f2fd2b1..837c5e4a1e 100644
--- a/src/corelib/kernel/qobjectdefs.h
+++ b/src/corelib/kernel/qobjectdefs.h
@@ -258,7 +258,7 @@ class QMetaClassInfo;
 class Q_CORE_EXPORT QGenericArgument
 {
 public:
-    inline QGenericArgument(const char *aName = 0, const void *aData = 0)
+    inline QGenericArgument(const char *aName = Q_NULLPTR, const void *aData = Q_NULLPTR)
         : _data(aData), _name(aName) {}
     inline void *data() const { return const_cast<void *>(_data); }
     inline const char *name() const { return _name; }
@@ -271,7 +271,7 @@ private:
 class Q_CORE_EXPORT QGenericReturnArgument: public QGenericArgument
 {
 public:
-    inline QGenericReturnArgument(const char *aName = 0, void *aData = 0)
+    inline QGenericReturnArgument(const char *aName = Q_NULLPTR, void *aData = Q_NULLPTR)
         : QGenericArgument(aName, aData)
         {}
 };
@@ -351,7 +351,7 @@ struct Q_CORE_EXPORT QMetaObject
     // internal index-based connect
     static Connection connect(const QObject *sender, int signal_index,
                         const QObject *receiver, int method_index,
-                        int type = 0, int *types = 0);
+                        int type = 0, int *types = Q_NULLPTR);
     // internal index-based disconnect
     static bool disconnect(const QObject *sender, int signal_index,
                            const QObject *receiver, int method_index);
@@ -368,7 +368,7 @@ struct Q_CORE_EXPORT QMetaObject
     static bool invokeMethod(QObject *obj, const char *member,
                              Qt::ConnectionType,
                              QGenericReturnArgument ret,
-                             QGenericArgument val0 = QGenericArgument(0),
+                             QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                              QGenericArgument val1 = QGenericArgument(),
                              QGenericArgument val2 = QGenericArgument(),
                              QGenericArgument val3 = QGenericArgument(),
@@ -381,7 +381,7 @@ struct Q_CORE_EXPORT QMetaObject
 
     static inline bool invokeMethod(QObject *obj, const char *member,
                              QGenericReturnArgument ret,
-                             QGenericArgument val0 = QGenericArgument(0),
+                             QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                              QGenericArgument val1 = QGenericArgument(),
                              QGenericArgument val2 = QGenericArgument(),
                              QGenericArgument val3 = QGenericArgument(),
@@ -398,7 +398,7 @@ struct Q_CORE_EXPORT QMetaObject
 
     static inline bool invokeMethod(QObject *obj, const char *member,
                              Qt::ConnectionType type,
-                             QGenericArgument val0 = QGenericArgument(0),
+                             QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                              QGenericArgument val1 = QGenericArgument(),
                              QGenericArgument val2 = QGenericArgument(),
                              QGenericArgument val3 = QGenericArgument(),
@@ -414,7 +414,7 @@ struct Q_CORE_EXPORT QMetaObject
     }
 
     static inline bool invokeMethod(QObject *obj, const char *member,
-                             QGenericArgument val0 = QGenericArgument(0),
+                             QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                              QGenericArgument val1 = QGenericArgument(),
                              QGenericArgument val2 = QGenericArgument(),
                              QGenericArgument val3 = QGenericArgument(),
@@ -429,7 +429,7 @@ struct Q_CORE_EXPORT QMetaObject
                 val1, val2, val3, val4, val5, val6, val7, val8, val9);
     }
 
-    QObject *newInstance(QGenericArgument val0 = QGenericArgument(0),
+    QObject *newInstance(QGenericArgument val0 = QGenericArgument(Q_NULLPTR),
                          QGenericArgument val1 = QGenericArgument(),
                          QGenericArgument val2 = QGenericArgument(),
                          QGenericArgument val3 = QGenericArgument(),
@@ -485,11 +485,11 @@ public:
     operator bool() const;
 #else
     typedef void *Connection::*RestrictedBool;
-    operator RestrictedBool() const { return d_ptr ? &Connection::d_ptr : 0; }
+    operator RestrictedBool() const { return d_ptr ? &Connection::d_ptr : Q_NULLPTR; }
 #endif
 
 #ifdef Q_COMPILER_RVALUE_REFS
-    inline Connection(Connection &&o) : d_ptr(o.d_ptr) { o.d_ptr = 0; }
+    inline Connection(Connection &&o) : d_ptr(o.d_ptr) { o.d_ptr = Q_NULLPTR; }
     inline Connection &operator=(Connection &&other)
     { qSwap(d_ptr, other.d_ptr); return *this; }
 #endif
diff --git a/src/corelib/kernel/qsharedmemory.h b/src/corelib/kernel/qsharedmemory.h
index c192910dc7..67558e3348 100644
--- a/src/corelib/kernel/qsharedmemory.h
+++ b/src/corelib/kernel/qsharedmemory.h
@@ -68,8 +68,8 @@ public:
         UnknownError
     };
 
-    QSharedMemory(QObject *parent = 0);
-    QSharedMemory(const QString &key, QObject *parent = 0);
+    QSharedMemory(QObject *parent = Q_NULLPTR);
+    QSharedMemory(const QString &key, QObject *parent = Q_NULLPTR);
     ~QSharedMemory();
 
     void setKey(const QString &key);
diff --git a/src/corelib/kernel/qsignalmapper.h b/src/corelib/kernel/qsignalmapper.h
index df2a0a52ea..7aaef6affc 100644
--- a/src/corelib/kernel/qsignalmapper.h
+++ b/src/corelib/kernel/qsignalmapper.h
@@ -45,7 +45,7 @@ class Q_CORE_EXPORT QSignalMapper : public QObject
     Q_OBJECT
     Q_DECLARE_PRIVATE(QSignalMapper)
 public:
-    explicit QSignalMapper(QObject *parent = 0);
+    explicit QSignalMapper(QObject *parent = Q_NULLPTR);
     ~QSignalMapper();
 
     void setMapping(QObject *sender, int id);
diff --git a/src/corelib/kernel/qsocketnotifier.h b/src/corelib/kernel/qsocketnotifier.h
index 4bafbfa69f..8a7af6ebbc 100644
--- a/src/corelib/kernel/qsocketnotifier.h
+++ b/src/corelib/kernel/qsocketnotifier.h
@@ -47,7 +47,7 @@ class Q_CORE_EXPORT QSocketNotifier : public QObject
 public:
     enum Type { Read, Write, Exception };
 
-    QSocketNotifier(qintptr socket, Type, QObject *parent = 0);
+    QSocketNotifier(qintptr socket, Type, QObject *parent = Q_NULLPTR);
     ~QSocketNotifier();
 
     qintptr socket() const;
diff --git a/src/corelib/kernel/qtimer.h b/src/corelib/kernel/qtimer.h
index 163ef75291..56f8a1a177 100644
--- a/src/corelib/kernel/qtimer.h
+++ b/src/corelib/kernel/qtimer.h
@@ -53,7 +53,7 @@ class Q_CORE_EXPORT QTimer : public QObject
     Q_PROPERTY(Qt::TimerType timerType READ timerType WRITE setTimerType)
     Q_PROPERTY(bool active READ isActive)
 public:
-    explicit QTimer(QObject *parent = 0);
+    explicit QTimer(QObject *parent = Q_NULLPTR);
     ~QTimer();
 
     inline bool isActive() const { return id >= 0; }
diff --git a/src/corelib/kernel/qtranslator.h b/src/corelib/kernel/qtranslator.h
index 1552bbde35..78f714c5c6 100644
--- a/src/corelib/kernel/qtranslator.h
+++ b/src/corelib/kernel/qtranslator.h
@@ -49,11 +49,11 @@ class Q_CORE_EXPORT QTranslator : public QObject
 {
     Q_OBJECT
 public:
-    explicit QTranslator(QObject *parent = 0);
+    explicit QTranslator(QObject *parent = Q_NULLPTR);
     ~QTranslator();
 
     virtual QString translate(const char *context, const char *sourceText,
-                              const char *disambiguation = 0, int n = -1) const;
+                              const char *disambiguation = Q_NULLPTR, int n = -1) const;
 
     virtual bool isEmpty() const;
 
diff --git a/src/corelib/kernel/qvariant.h b/src/corelib/kernel/qvariant.h
index 58dfc3aab0..bb996af121 100644
--- a/src/corelib/kernel/qvariant.h
+++ b/src/corelib/kernel/qvariant.h
@@ -278,14 +278,14 @@ class Q_CORE_EXPORT QVariant
     void detach();
     inline bool isDetached() const;
 
-    int toInt(bool *ok = 0) const;
-    uint toUInt(bool *ok = 0) const;
-    qlonglong toLongLong(bool *ok = 0) const;
-    qulonglong toULongLong(bool *ok = 0) const;
+    int toInt(bool *ok = Q_NULLPTR) const;
+    uint toUInt(bool *ok = Q_NULLPTR) const;
+    qlonglong toLongLong(bool *ok = Q_NULLPTR) const;
+    qulonglong toULongLong(bool *ok = Q_NULLPTR) const;
     bool toBool() const;
-    double toDouble(bool *ok = 0) const;
-    float toFloat(bool *ok = 0) const;
-    qreal toReal(bool *ok = 0) const;
+    double toDouble(bool *ok = Q_NULLPTR) const;
+    float toFloat(bool *ok = Q_NULLPTR) const;
+    qreal toReal(bool *ok = Q_NULLPTR) const;
     QByteArray toByteArray() const;
     QBitArray toBitArray() const;
     QString toString() const;
@@ -364,7 +364,7 @@ class Q_CORE_EXPORT QVariant
     struct Private
     {
         inline Private() Q_DECL_NOTHROW : type(Invalid), is_shared(false), is_null(true)
-        { data.ptr = 0; }
+        { data.ptr = Q_NULLPTR; }
 
         // Internal constructor for initialized variants.
         explicit inline Private(uint variantType) Q_DECL_NOTHROW
diff --git a/src/corelib/plugin/qlibrary.h b/src/corelib/plugin/qlibrary.h
index 16bdf79206..77ad107c6f 100644
--- a/src/corelib/plugin/qlibrary.h
+++ b/src/corelib/plugin/qlibrary.h
@@ -59,10 +59,10 @@ public:
     Q_FLAG(LoadHint)
     Q_FLAG(LoadHints)
 
-    explicit QLibrary(QObject *parent = 0);
-    explicit QLibrary(const QString& fileName, QObject *parent = 0);
-    explicit QLibrary(const QString& fileName, int verNum, QObject *parent = 0);
-    explicit QLibrary(const QString& fileName, const QString &version, QObject *parent = 0);
+    explicit QLibrary(QObject *parent = Q_NULLPTR);
+    explicit QLibrary(const QString& fileName, QObject *parent = Q_NULLPTR);
+    explicit QLibrary(const QString& fileName, int verNum, QObject *parent = Q_NULLPTR);
+    explicit QLibrary(const QString& fileName, const QString &version, QObject *parent = Q_NULLPTR);
     ~QLibrary();
 
     QFunctionPointer resolve(const char *symbol);
diff --git a/src/corelib/plugin/qpluginloader.h b/src/corelib/plugin/qpluginloader.h
index b947e6ed9e..0ab25bbb07 100644
--- a/src/corelib/plugin/qpluginloader.h
+++ b/src/corelib/plugin/qpluginloader.h
@@ -50,8 +50,8 @@ class Q_CORE_EXPORT QPluginLoader : public QObject
     Q_PROPERTY(QString fileName READ fileName WRITE setFileName)
     Q_PROPERTY(QLibrary::LoadHints loadHints READ loadHints WRITE setLoadHints)
 public:
-    explicit QPluginLoader(QObject *parent = 0);
-    explicit QPluginLoader(const QString &fileName, QObject *parent = 0);
+    explicit QPluginLoader(QObject *parent = Q_NULLPTR);
+    explicit QPluginLoader(const QString &fileName, QObject *parent = Q_NULLPTR);
     ~QPluginLoader();
 
     QObject *instance();
diff --git a/src/corelib/statemachine/qabstractstate.h b/src/corelib/statemachine/qabstractstate.h
index 592c841c18..3aa4b2fabb 100644
--- a/src/corelib/statemachine/qabstractstate.h
+++ b/src/corelib/statemachine/qabstractstate.h
@@ -63,7 +63,7 @@ Q_SIGNALS:
     void activeChanged(bool active);
 
 protected:
-    QAbstractState(QState *parent = 0);
+    QAbstractState(QState *parent = Q_NULLPTR);
 
     virtual void onEntry(QEvent *event) = 0;
     virtual void onExit(QEvent *event) = 0;
diff --git a/src/corelib/statemachine/qabstracttransition.h b/src/corelib/statemachine/qabstracttransition.h
index bf32b3e825..0d61ae3f5c 100644
--- a/src/corelib/statemachine/qabstracttransition.h
+++ b/src/corelib/statemachine/qabstracttransition.h
@@ -67,7 +67,7 @@ public:
     };
     Q_ENUM(TransitionType)
 
-    QAbstractTransition(QState *sourceState = 0);
+    QAbstractTransition(QState *sourceState = Q_NULLPTR);
     virtual ~QAbstractTransition();
 
     QState *sourceState() const;
diff --git a/src/corelib/statemachine/qeventtransition.h b/src/corelib/statemachine/qeventtransition.h
index 6909e855b1..5ec3b7bb26 100644
--- a/src/corelib/statemachine/qeventtransition.h
+++ b/src/corelib/statemachine/qeventtransition.h
@@ -49,8 +49,8 @@ class Q_CORE_EXPORT QEventTransition : public QAbstractTransition
     Q_PROPERTY(QObject* eventSource READ eventSource WRITE setEventSource)
     Q_PROPERTY(QEvent::Type eventType READ eventType WRITE setEventType)
 public:
-    QEventTransition(QState *sourceState = 0);
-    QEventTransition(QObject *object, QEvent::Type type, QState *sourceState = 0);
+    QEventTransition(QState *sourceState = Q_NULLPTR);
+    QEventTransition(QObject *object, QEvent::Type type, QState *sourceState = Q_NULLPTR);
     ~QEventTransition();
 
     QObject *eventSource() const;
diff --git a/src/corelib/statemachine/qfinalstate.h b/src/corelib/statemachine/qfinalstate.h
index 51c97b1545..2c76e7b6e6 100644
--- a/src/corelib/statemachine/qfinalstate.h
+++ b/src/corelib/statemachine/qfinalstate.h
@@ -46,7 +46,7 @@ class Q_CORE_EXPORT QFinalState : public QAbstractState
 {
     Q_OBJECT
 public:
-    QFinalState(QState *parent = 0);
+    QFinalState(QState *parent = Q_NULLPTR);
     ~QFinalState();
 
 protected:
diff --git a/src/corelib/statemachine/qhistorystate.h b/src/corelib/statemachine/qhistorystate.h
index 549be15ab0..97ac376688 100644
--- a/src/corelib/statemachine/qhistorystate.h
+++ b/src/corelib/statemachine/qhistorystate.h
@@ -54,8 +54,8 @@ public:
     };
     Q_ENUM(HistoryType)
 
-    QHistoryState(QState *parent = 0);
-    QHistoryState(HistoryType type, QState *parent = 0);
+    QHistoryState(QState *parent = Q_NULLPTR);
+    QHistoryState(HistoryType type, QState *parent = Q_NULLPTR);
     ~QHistoryState();
 
     QAbstractState *defaultState() const;
diff --git a/src/corelib/statemachine/qsignaltransition.h b/src/corelib/statemachine/qsignaltransition.h
index bc56f4e9b7..c388323ec4 100644
--- a/src/corelib/statemachine/qsignaltransition.h
+++ b/src/corelib/statemachine/qsignaltransition.h
@@ -49,9 +49,9 @@ class Q_CORE_EXPORT QSignalTransition : public QAbstractTransition
     Q_PROPERTY(QByteArray signal READ signal WRITE setSignal NOTIFY signalChanged)
 
 public:
-    QSignalTransition(QState *sourceState = 0);
+    QSignalTransition(QState *sourceState = Q_NULLPTR);
     QSignalTransition(const QObject *sender, const char *signal,
-                      QState *sourceState = 0);
+                      QState *sourceState = Q_NULLPTR);
     ~QSignalTransition();
 
     QObject *senderObject() const;
diff --git a/src/corelib/statemachine/qstate.h b/src/corelib/statemachine/qstate.h
index a74c782027..0300a9ef2d 100644
--- a/src/corelib/statemachine/qstate.h
+++ b/src/corelib/statemachine/qstate.h
@@ -66,8 +66,8 @@ public:
     };
     Q_ENUM(RestorePolicy)
 
-    QState(QState *parent = 0);
-    QState(ChildMode childMode, QState *parent = 0);
+    QState(QState *parent = Q_NULLPTR);
+    QState(ChildMode childMode, QState *parent = Q_NULLPTR);
     ~QState();
 
     QAbstractState *errorState() const;
diff --git a/src/corelib/statemachine/qstatemachine.h b/src/corelib/statemachine/qstatemachine.h
index d6c3b7bfa7..5fca034386 100644
--- a/src/corelib/statemachine/qstatemachine.h
+++ b/src/corelib/statemachine/qstatemachine.h
@@ -104,8 +104,8 @@ public:
         NoCommonAncestorForTransitionError
     };
 
-    explicit QStateMachine(QObject *parent = 0);
-    explicit QStateMachine(QState::ChildMode childMode, QObject *parent = 0);
+    explicit QStateMachine(QObject *parent = Q_NULLPTR);
+    explicit QStateMachine(QState::ChildMode childMode, QObject *parent = Q_NULLPTR);
     ~QStateMachine();
 
     void addState(QAbstractState *state);
diff --git a/src/corelib/thread/qexception.h b/src/corelib/thread/qexception.h
index 7fb798fdad..b15ae5095a 100644
--- a/src/corelib/thread/qexception.h
+++ b/src/corelib/thread/qexception.h
@@ -84,7 +84,7 @@ class Base;
 class Q_CORE_EXPORT ExceptionHolder
 {
 public:
-    ExceptionHolder(QException *exception = 0);
+    ExceptionHolder(QException *exception = Q_NULLPTR);
     ExceptionHolder(const ExceptionHolder &other);
     void operator=(const ExceptionHolder &other);
     ~ExceptionHolder();
diff --git a/src/corelib/thread/qfutureinterface.h b/src/corelib/thread/qfutureinterface.h
index 01eb043a5e..8c1f7e7d82 100644
--- a/src/corelib/thread/qfutureinterface.h
+++ b/src/corelib/thread/qfutureinterface.h
@@ -299,7 +299,7 @@ public:
 
     void reportResult(const void *, int) { }
     void reportResults(const QVector<void> &, int) { }
-    void reportFinished(const void * = 0) { QFutureInterfaceBase::reportFinished(); }
+    void reportFinished(const void * = Q_NULLPTR) { QFutureInterfaceBase::reportFinished(); }
 };
 
 QT_END_NAMESPACE
diff --git a/src/corelib/thread/qfuturewatcher.h b/src/corelib/thread/qfuturewatcher.h
index 63558d4a0f..42a22d9063 100644
--- a/src/corelib/thread/qfuturewatcher.h
+++ b/src/corelib/thread/qfuturewatcher.h
@@ -52,7 +52,7 @@ class Q_CORE_EXPORT QFutureWatcherBase : public QObject
     Q_DECLARE_PRIVATE(QFutureWatcherBase)
 
 public:
-    explicit QFutureWatcherBase(QObject *parent = 0);
+    explicit QFutureWatcherBase(QObject *parent = Q_NULLPTR);
     // de-inline dtor
 
     int progressValue() const;
@@ -179,7 +179,7 @@ template <>
 class QFutureWatcher<void> : public QFutureWatcherBase
 {
 public:
-    explicit QFutureWatcher(QObject *_parent = 0)
+    explicit QFutureWatcher(QObject *_parent = Q_NULLPTR)
         : QFutureWatcherBase(_parent)
     { }
     ~QFutureWatcher()
diff --git a/src/corelib/thread/qmutex.h b/src/corelib/thread/qmutex.h
index 63c488747f..0c5a73b4df 100644
--- a/src/corelib/thread/qmutex.h
+++ b/src/corelib/thread/qmutex.h
@@ -73,16 +73,16 @@ public:
 
 private:
     inline bool fastTryLock() Q_DECL_NOTHROW {
-        return d_ptr.testAndSetAcquire(0, dummyLocked());
+        return d_ptr.testAndSetAcquire(Q_NULLPTR, dummyLocked());
     }
     inline bool fastTryUnlock() Q_DECL_NOTHROW {
-        return d_ptr.testAndSetRelease(dummyLocked(), 0);
+        return d_ptr.testAndSetRelease(dummyLocked(), Q_NULLPTR);
     }
     inline bool fastTryLock(QMutexData *&current) Q_DECL_NOTHROW {
-        return d_ptr.testAndSetAcquire(0, dummyLocked(), current);
+        return d_ptr.testAndSetAcquire(Q_NULLPTR, dummyLocked(), current);
     }
     inline bool fastTryUnlock(QMutexData *&current) Q_DECL_NOTHROW {
-        return d_ptr.testAndSetRelease(dummyLocked(), 0, current);
+        return d_ptr.testAndSetRelease(dummyLocked(), Q_NULLPTR, current);
     }
 
     void lockInternal() QT_MUTEX_LOCK_NOEXCEPT;
diff --git a/src/corelib/thread/qresultstore.h b/src/corelib/thread/qresultstore.h
index fbcb8ad3cd..7ecaa231b2 100644
--- a/src/corelib/thread/qresultstore.h
+++ b/src/corelib/thread/qresultstore.h
@@ -61,8 +61,8 @@ class ResultItem
 public:
     ResultItem(const void *_result, int _count) : m_count(_count), result(_result) { } // contruct with vector of results
     ResultItem(const void *_result) : m_count(0), result(_result) { } // construct with result
-    ResultItem() : m_count(0), result(0) { }
-    bool isValid() const { return result != 0; }
+    ResultItem() : m_count(0), result(Q_NULLPTR) { }
+    bool isValid() const { return result != Q_NULLPTR; }
     bool isVector() const { return m_count != 0; }
     int count() const { return (m_count == 0) ?  1 : m_count; }
     int m_count;          // result is either a pointer to a result or to a vector of results,
diff --git a/src/corelib/thread/qthread.h b/src/corelib/thread/qthread.h
index bfc469583d..d333980bf4 100644
--- a/src/corelib/thread/qthread.h
+++ b/src/corelib/thread/qthread.h
@@ -55,7 +55,7 @@ public:
     static int idealThreadCount() Q_DECL_NOTHROW;
     static void yieldCurrentThread();
 
-    explicit QThread(QObject *parent = 0);
+    explicit QThread(QObject *parent = Q_NULLPTR);
     ~QThread();
 
     enum Priority {
@@ -116,7 +116,7 @@ protected:
     static void setTerminationEnabled(bool enabled = true);
 
 protected:
-    QThread(QThreadPrivate &dd, QObject *parent = 0);
+    QThread(QThreadPrivate &dd, QObject *parent = Q_NULLPTR);
 
 private:
     Q_DECLARE_PRIVATE(QThread)
diff --git a/src/corelib/thread/qthreadpool.h b/src/corelib/thread/qthreadpool.h
index b1ca808a99..95b41a0417 100644
--- a/src/corelib/thread/qthreadpool.h
+++ b/src/corelib/thread/qthreadpool.h
@@ -55,7 +55,7 @@ class Q_CORE_EXPORT QThreadPool : public QObject
     friend class QFutureInterfaceBase;
 
 public:
-    QThreadPool(QObject *parent = 0);
+    QThreadPool(QObject *parent = Q_NULLPTR);
     ~QThreadPool();
 
     static QThreadPool *globalInstance();
diff --git a/src/corelib/tools/qarraydata.h b/src/corelib/tools/qarraydata.h
index df35a1cb62..95c1d5f22e 100644
--- a/src/corelib/tools/qarraydata.h
+++ b/src/corelib/tools/qarraydata.h
@@ -132,7 +132,7 @@ struct QTypedArrayData
         typedef T *pointer;
         typedef T &reference;
 
-        inline iterator() : i(0) {}
+        inline iterator() : i(Q_NULLPTR) {}
         inline iterator(T *n) : i(n) {}
         inline iterator(const iterator &o): i(o.i){} // #### Qt 6: remove, the implicit version is fine
         inline T &operator*() const { return *i; }
@@ -166,7 +166,7 @@ struct QTypedArrayData
         typedef const T *pointer;
         typedef const T &reference;
 
-        inline const_iterator() : i(0) {}
+        inline const_iterator() : i(Q_NULLPTR) {}
         inline const_iterator(const T *n) : i(n) {}
         inline const_iterator(const const_iterator &o): i(o.i) {} // #### Qt 6: remove, the default version is fine
         inline explicit const_iterator(const iterator &o): i(o.i) {}
diff --git a/src/corelib/tools/qbytearray.h b/src/corelib/tools/qbytearray.h
index 38f277533b..7388c4eee5 100644
--- a/src/corelib/tools/qbytearray.h
+++ b/src/corelib/tools/qbytearray.h
@@ -335,16 +335,16 @@ public:
     inline QT_ASCII_CAST_WARN bool operator>=(const QString &s2) const;
 #endif
 
-    short toShort(bool *ok = 0, int base = 10) const;
-    ushort toUShort(bool *ok = 0, int base = 10) const;
-    int toInt(bool *ok = 0, int base = 10) const;
-    uint toUInt(bool *ok = 0, int base = 10) const;
-    long toLong(bool *ok = 0, int base = 10) const;
-    ulong toULong(bool *ok = 0, int base = 10) const;
-    qlonglong toLongLong(bool *ok = 0, int base = 10) const;
-    qulonglong toULongLong(bool *ok = 0, int base = 10) const;
-    float toFloat(bool *ok = 0) const;
-    double toDouble(bool *ok = 0) const;
+    short toShort(bool *ok = Q_NULLPTR, int base = 10) const;
+    ushort toUShort(bool *ok = Q_NULLPTR, int base = 10) const;
+    int toInt(bool *ok = Q_NULLPTR, int base = 10) const;
+    uint toUInt(bool *ok = Q_NULLPTR, int base = 10) const;
+    long toLong(bool *ok = Q_NULLPTR, int base = 10) const;
+    ulong toULong(bool *ok = Q_NULLPTR, int base = 10) const;
+    qlonglong toLongLong(bool *ok = Q_NULLPTR, int base = 10) const;
+    qulonglong toULongLong(bool *ok = Q_NULLPTR, int base = 10) const;
+    float toFloat(bool *ok = Q_NULLPTR) const;
+    double toDouble(bool *ok = Q_NULLPTR) const;
     QByteArray toBase64(Base64Options options) const;
     QByteArray toBase64() const; // ### Qt6 merge with previous
     QByteArray toHex() const;
diff --git a/src/corelib/tools/qbytearraylist.h b/src/corelib/tools/qbytearraylist.h
index f8539ca07a..8b832b7760 100644
--- a/src/corelib/tools/qbytearraylist.h
+++ b/src/corelib/tools/qbytearraylist.h
@@ -61,7 +61,7 @@ protected:
 #endif
 public:
     inline QByteArray join() const
-    { return QtPrivate::QByteArrayList_join(self(), 0, 0); }
+    { return QtPrivate::QByteArrayList_join(self(), Q_NULLPTR, 0); }
     inline QByteArray join(const QByteArray &sep) const
     { return QtPrivate::QByteArrayList_join(self(), sep.constData(), sep.size()); }
     inline QByteArray join(char sep) const
diff --git a/src/corelib/tools/qcollator.h b/src/corelib/tools/qcollator.h
index e1fa161257..57133165c4 100644
--- a/src/corelib/tools/qcollator.h
+++ b/src/corelib/tools/qcollator.h
@@ -83,7 +83,7 @@ public:
     QCollator &operator=(const QCollator &);
 #ifdef Q_COMPILER_RVALUE_REFS
     QCollator(QCollator &&other) Q_DECL_NOTHROW
-        : d(other.d) { other.d = 0; }
+        : d(other.d) { other.d = Q_NULLPTR; }
     QCollator &operator=(QCollator &&other) Q_DECL_NOTHROW
     { swap(other); return *this; }
 #endif
diff --git a/src/corelib/tools/qdatetime.h b/src/corelib/tools/qdatetime.h
index 273778f48c..a8372c1d57 100644
--- a/src/corelib/tools/qdatetime.h
+++ b/src/corelib/tools/qdatetime.h
@@ -74,7 +74,7 @@ public:
     int dayOfYear() const;
     int daysInMonth() const;
     int daysInYear() const;
-    int weekNumber(int *yearNum = 0) const;
+    int weekNumber(int *yearNum = Q_NULLPTR) const;
 
 #ifndef QT_NO_TEXTDATE
     static QString shortMonthName(int month, MonthNameType type = DateFormat);
diff --git a/src/corelib/tools/qeasingcurve.h b/src/corelib/tools/qeasingcurve.h
index 4065de1366..d04d5ef30a 100644
--- a/src/corelib/tools/qeasingcurve.h
+++ b/src/corelib/tools/qeasingcurve.h
@@ -75,7 +75,7 @@ public:
     QEasingCurve &operator=(const QEasingCurve &other)
     { if ( this != &other ) { QEasingCurve copy(other); swap(copy); } return *this; }
 #ifdef Q_COMPILER_RVALUE_REFS
-    QEasingCurve(QEasingCurve &&other) : d_ptr(other.d_ptr) { other.d_ptr = 0; }
+    QEasingCurve(QEasingCurve &&other) : d_ptr(other.d_ptr) { other.d_ptr = Q_NULLPTR; }
     QEasingCurve &operator=(QEasingCurve &&other)
     { qSwap(d_ptr, other.d_ptr); return *this; }
 #endif
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index 2080a22e23..c83dcaabe1 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -306,7 +306,7 @@ public:
         typedef T *pointer;
         typedef T &reference;
 
-        inline iterator() : i(0) { }
+        inline iterator() : i(Q_NULLPTR) { }
         explicit inline iterator(void *node) : i(reinterpret_cast<QHashData::Node *>(node)) { }
 
         inline const Key &key() const { return concrete(i)->key; }
@@ -363,7 +363,7 @@ public:
         typedef const T *pointer;
         typedef const T &reference;
 
-        inline const_iterator() : i(0) { }
+        inline const_iterator() : i(Q_NULLPTR) { }
         explicit inline const_iterator(void *node)
             : i(reinterpret_cast<QHashData::Node *>(node)) { }
 #ifdef QT_STRICT_ITERATORS
@@ -451,7 +451,7 @@ public:
 private:
     void detach_helper();
     void freeData(QHashData *d);
-    Node **findNode(const Key &key, uint *hp = 0) const;
+    Node **findNode(const Key &key, uint *hp = Q_NULLPTR) const;
     Node **findNode(const Key &key, uint h) const;
     Node *createNode(uint h, const Key &key, const T &value, Node **nextNode);
     void deleteNode(Node *node);
@@ -496,7 +496,7 @@ template <class Key, class T>
 Q_INLINE_TEMPLATE void QHash<Key, T>::duplicateNode(QHashData::Node *node, void *newNode)
 {
     Node *concreteNode = concrete(node);
-    new (newNode) Node(concreteNode->key, concreteNode->value, concreteNode->h, 0);
+    new (newNode) Node(concreteNode->key, concreteNode->value, concreteNode->h, Q_NULLPTR);
 }
 
 template <class Key, class T>
diff --git a/src/corelib/tools/qlocale.h b/src/corelib/tools/qlocale.h
index a622bbafeb..0cbfa6710c 100644
--- a/src/corelib/tools/qlocale.h
+++ b/src/corelib/tools/qlocale.h
@@ -871,23 +871,23 @@ public:
     QString nativeLanguageName() const;
     QString nativeCountryName() const;
 
-    short toShort(const QString &s, bool *ok = 0) const;
-    ushort toUShort(const QString &s, bool *ok = 0) const;
-    int toInt(const QString &s, bool *ok = 0) const;
-    uint toUInt(const QString &s, bool *ok = 0) const;
-    qlonglong toLongLong(const QString &s, bool *ok = 0) const;
-    qulonglong toULongLong(const QString &s, bool *ok = 0) const;
-    float toFloat(const QString &s, bool *ok = 0) const;
-    double toDouble(const QString &s, bool *ok = 0) const;
+    short toShort(const QString &s, bool *ok = Q_NULLPTR) const;
+    ushort toUShort(const QString &s, bool *ok = Q_NULLPTR) const;
+    int toInt(const QString &s, bool *ok = Q_NULLPTR) const;
+    uint toUInt(const QString &s, bool *ok = Q_NULLPTR) const;
+    qlonglong toLongLong(const QString &s, bool *ok = Q_NULLPTR) const;
+    qulonglong toULongLong(const QString &s, bool *ok = Q_NULLPTR) const;
+    float toFloat(const QString &s, bool *ok = Q_NULLPTR) const;
+    double toDouble(const QString &s, bool *ok = Q_NULLPTR) const;
 
-    short toShort(const QStringRef &s, bool *ok = 0) const;
-    ushort toUShort(const QStringRef &s, bool *ok = 0) const;
-    int toInt(const QStringRef &s, bool *ok = 0) const;
-    uint toUInt(const QStringRef &s, bool *ok = 0) const;
-    qlonglong toLongLong(const QStringRef &s, bool *ok = 0) const;
-    qulonglong toULongLong(const QStringRef &s, bool *ok = 0) const;
-    float toFloat(const QStringRef &s, bool *ok = 0) const;
-    double toDouble(const QStringRef &s, bool *ok = 0) const;
+    short toShort(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    ushort toUShort(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    int toInt(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    uint toUInt(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    qlonglong toLongLong(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    qulonglong toULongLong(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    float toFloat(const QStringRef &s, bool *ok = Q_NULLPTR) const;
+    double toDouble(const QStringRef &s, bool *ok = Q_NULLPTR) const;
 
     QString toString(qlonglong i) const;
     QString toString(qulonglong i) const;
diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index f4678e4b2f..bf0a36aa88 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -148,7 +148,7 @@ template <class Key, class T>
 inline QMapNode<Key, T> *QMapNode<Key, T>::lowerBound(const Key &akey)
 {
     QMapNode<Key, T> *n = this;
-    QMapNode<Key, T> *lastNode = 0;
+    QMapNode<Key, T> *lastNode = Q_NULLPTR;
     while (n) {
         if (!qMapLessThanKey(n->key, akey)) {
             lastNode = n;
@@ -164,7 +164,7 @@ template <class Key, class T>
 inline QMapNode<Key, T> *QMapNode<Key, T>::upperBound(const Key &akey)
 {
     QMapNode<Key, T> *n = this;
-    QMapNode<Key, T> *lastNode = 0;
+    QMapNode<Key, T> *lastNode = Q_NULLPTR;
     while (n) {
         if (qMapLessThanKey(akey, n->key)) {
             lastNode = n;
@@ -216,7 +216,7 @@ struct QMapData : public QMapDataBase
     Node *findNode(const Key &akey) const;
     void nodeRange(const Key &akey, Node **firstNode, Node **lastNode);
 
-    Node *createNode(const Key &k, const T &v, Node *parent = 0, bool left = false)
+    Node *createNode(const Key &k, const T &v, Node *parent = Q_NULLPTR, bool left = false)
     {
         Node *n = static_cast<Node *>(QMapDataBase::createNode(sizeof(Node), Q_ALIGNOF(Node),
                                       parent, left));
@@ -257,13 +257,13 @@ QMapNode<Key, T> *QMapNode<Key, T>::copy(QMapData<Key, T> *d) const
         n->left = leftNode()->copy(d);
         n->left->setParent(n);
     } else {
-        n->left = 0;
+        n->left = Q_NULLPTR;
     }
     if (right) {
         n->right = rightNode()->copy(d);
         n->right->setParent(n);
     } else {
-        n->right = 0;
+        n->right = Q_NULLPTR;
     }
     return n;
 }
@@ -284,7 +284,7 @@ QMapNode<Key, T> *QMapData<Key, T>::findNode(const Key &akey) const
         if (lb && !qMapLessThanKey(akey, lb->key))
             return lb;
     }
-    return 0;
+    return Q_NULLPTR;
 }
 
 
@@ -300,10 +300,10 @@ void QMapData<Key, T>::nodeRange(const Key &akey, QMapNode<Key, T> **firstNode,
         } else if (qMapLessThanKey(n->key, akey)) {
             n = n->rightNode();
         } else {
-            *firstNode = n->leftNode() ? n->leftNode()->lowerBound(akey) : 0;
+            *firstNode = n->leftNode() ? n->leftNode()->lowerBound(akey) : Q_NULLPTR;
             if (!*firstNode)
                 *firstNode = n;
-            *lastNode = n->rightNode() ? n->rightNode()->upperBound(akey) : 0;
+            *lastNode = n->rightNode() ? n->rightNode()->upperBound(akey) : Q_NULLPTR;
             if (!*lastNode)
                 *lastNode = l;
             return;
@@ -412,7 +412,7 @@ public:
         typedef T *pointer;
         typedef T &reference;
 
-        inline iterator() : i(0) { }
+        inline iterator() : i(Q_NULLPTR) { }
         inline iterator(Node *node) : i(node) { }
 
         inline const Key &key() const { return i->key; }
@@ -469,7 +469,7 @@ public:
         typedef const T *pointer;
         typedef const T &reference;
 
-        inline const_iterator() : i(0) { }
+        inline const_iterator() : i(Q_NULLPTR) { }
         inline const_iterator(const Node *node) : i(node) { }
 #ifdef QT_STRICT_ITERATORS
         explicit inline const_iterator(const iterator &o)
@@ -650,7 +650,7 @@ Q_INLINE_TEMPLATE int QMap<Key, T>::count(const Key &akey) const
 template <class Key, class T>
 Q_INLINE_TEMPLATE bool QMap<Key, T>::contains(const Key &akey) const
 {
-    return d->findNode(akey) != 0;
+    return d->findNode(akey) != Q_NULLPTR;
 }
 
 template <class Key, class T>
@@ -659,7 +659,7 @@ Q_INLINE_TEMPLATE typename QMap<Key, T>::iterator QMap<Key, T>::insert(const Key
     detach();
     Node *n = d->root();
     Node *y = d->end();
-    Node *lastNode = 0;
+    Node *lastNode = Q_NULLPTR;
     bool  left = true;
     while (n) {
         y = n;
@@ -734,15 +734,15 @@ typename QMap<Key, T>::iterator QMap<Key, T>::insert(const_iterator pos, const K
             }
 
             // we need to insert (not overwrite)
-            if (prev->right == 0) {
+            if (prev->right == Q_NULLPTR) {
                 Node *z = d->createNode(akey, avalue, prev, false);
                 return iterator(z);
             }
-            if (next->left == 0) {
+            if (next->left == Q_NULLPTR) {
                 Node *z = d->createNode(akey, avalue, next, true);
                 return iterator(z);
             }
-            Q_ASSERT(false); // We should have prev->right == 0 or next->left == 0.
+            Q_ASSERT(false); // We should have prev->right == Q_NULLPTR or next->left == Q_NULLPTR.
             return this->insert(akey, avalue);
         }
     }
@@ -756,7 +756,7 @@ Q_INLINE_TEMPLATE typename QMap<Key, T>::iterator QMap<Key, T>::insertMulti(cons
     Node* y = d->end();
     Node* x = static_cast<Node *>(d->root());
     bool left = true;
-    while (x != 0) {
+    while (x != Q_NULLPTR) {
         left = !qMapLessThanKey(x->key, akey);
         y = x;
         x = left ? x->leftNode() : x->rightNode();
@@ -803,15 +803,15 @@ typename QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const_iterator pos, co
                 return this->insertMulti(akey, avalue); // ignore hint
 
             // Hint is ok - do insert
-            if (prev->right == 0) {
+            if (prev->right == Q_NULLPTR) {
                 Node *z = d->createNode(akey, avalue, prev, false);
                 return iterator(z);
             }
-            if (next->left == 0) {
+            if (next->left == Q_NULLPTR) {
                 Node *z = d->createNode(akey, avalue, next, true);
                 return iterator(z);
             }
-            Q_ASSERT(false); // We should have prev->right == 0 or next->left == 0.
+            Q_ASSERT(false); // We should have prev->right == Q_NULLPTR or next->left == Q_NULLPTR.
             return this->insertMulti(akey, avalue);
         }
     }
@@ -1057,7 +1057,7 @@ Q_OUTOFLINE_TEMPLATE QList<T> QMap<Key, T>::values(const Key &akey) const
 template <class Key, class T>
 Q_INLINE_TEMPLATE typename QMap<Key, T>::const_iterator QMap<Key, T>::lowerBound(const Key &akey) const
 {
-    Node *lb = d->root() ? d->root()->lowerBound(akey) : 0;
+    Node *lb = d->root() ? d->root()->lowerBound(akey) : Q_NULLPTR;
     if (!lb)
         lb = d->end();
     return const_iterator(lb);
@@ -1067,7 +1067,7 @@ template <class Key, class T>
 Q_INLINE_TEMPLATE typename QMap<Key, T>::iterator QMap<Key, T>::lowerBound(const Key &akey)
 {
     detach();
-    Node *lb = d->root() ? d->root()->lowerBound(akey) : 0;
+    Node *lb = d->root() ? d->root()->lowerBound(akey) : Q_NULLPTR;
     if (!lb)
         lb = d->end();
     return iterator(lb);
@@ -1077,7 +1077,7 @@ template <class Key, class T>
 Q_INLINE_TEMPLATE typename QMap<Key, T>::const_iterator
 QMap<Key, T>::upperBound(const Key &akey) const
 {
-    Node *ub = d->root() ? d->root()->upperBound(akey) : 0;
+    Node *ub = d->root() ? d->root()->upperBound(akey) : Q_NULLPTR;
     if (!ub)
         ub = d->end();
     return const_iterator(ub);
@@ -1087,7 +1087,7 @@ template <class Key, class T>
 Q_INLINE_TEMPLATE typename QMap<Key, T>::iterator QMap<Key, T>::upperBound(const Key &akey)
 {
     detach();
-    Node *ub = d->root() ? d->root()->upperBound(akey) : 0;
+    Node *ub = d->root() ? d->root()->upperBound(akey) : Q_NULLPTR;
     if (!ub)
         ub = d->end();
     return iterator(ub);
diff --git a/src/corelib/tools/qstring.h b/src/corelib/tools/qstring.h
index af5d22a53b..c084433d51 100644
--- a/src/corelib/tools/qstring.h
+++ b/src/corelib/tools/qstring.h
@@ -594,16 +594,16 @@ public:
     static int localeAwareCompare(const QString& s1, const QStringRef& s2);
 
     // ### Qt6: make inline except for the long long versions
-    short  toShort(bool *ok=0, int base=10) const;
-    ushort toUShort(bool *ok=0, int base=10) const;
-    int toInt(bool *ok=0, int base=10) const;
-    uint toUInt(bool *ok=0, int base=10) const;
-    long toLong(bool *ok=0, int base=10) const;
-    ulong toULong(bool *ok=0, int base=10) const;
-    qlonglong toLongLong(bool *ok=0, int base=10) const;
-    qulonglong toULongLong(bool *ok=0, int base=10) const;
-    float toFloat(bool *ok=0) const;
-    double toDouble(bool *ok=0) const;
+    short  toShort(bool *ok=Q_NULLPTR, int base=10) const;
+    ushort toUShort(bool *ok=Q_NULLPTR, int base=10) const;
+    int toInt(bool *ok=Q_NULLPTR, int base=10) const;
+    uint toUInt(bool *ok=Q_NULLPTR, int base=10) const;
+    long toLong(bool *ok=Q_NULLPTR, int base=10) const;
+    ulong toULong(bool *ok=Q_NULLPTR, int base=10) const;
+    qlonglong toLongLong(bool *ok=Q_NULLPTR, int base=10) const;
+    qulonglong toULongLong(bool *ok=Q_NULLPTR, int base=10) const;
+    float toFloat(bool *ok=Q_NULLPTR) const;
+    double toDouble(bool *ok=Q_NULLPTR) const;
 
     QString &setNum(short, int base=10);
     QString &setNum(ushort, int base=10);
@@ -1350,7 +1350,7 @@ public:
     typedef QString::const_reference const_reference;
 
     // ### Qt 6: make this constructor constexpr, after the destructor is made trivial
-    inline QStringRef():m_string(0), m_position(0), m_size(0){}
+    inline QStringRef() : m_string(Q_NULLPTR), m_position(0), m_size(0) {}
     inline QStringRef(const QString *string, int position, int size);
     inline QStringRef(const QString *string);
 
@@ -1434,10 +1434,10 @@ public:
     QByteArray toLocal8Bit() const Q_REQUIRED_RESULT;
     QVector<uint> toUcs4() const Q_REQUIRED_RESULT;
 
-    inline void clear() { m_string = 0; m_position = m_size = 0; }
+    inline void clear() { m_string = Q_NULLPTR; m_position = m_size = 0; }
     QString toString() const;
     inline bool isEmpty() const { return m_size == 0; }
-    inline bool isNull() const { return m_string == 0 || m_string->isNull(); }
+    inline bool isNull() const { return m_string == Q_NULLPTR || m_string->isNull(); }
 
     QStringRef appendTo(QString *string) const;
 
@@ -1470,16 +1470,16 @@ public:
     static int localeAwareCompare(const QStringRef &s1, const QStringRef &s2);
 
     QStringRef trimmed() const Q_REQUIRED_RESULT;
-    short  toShort(bool *ok = 0, int base = 10) const;
-    ushort toUShort(bool *ok = 0, int base = 10) const;
-    int toInt(bool *ok = 0, int base = 10) const;
-    uint toUInt(bool *ok = 0, int base = 10) const;
-    long toLong(bool *ok = 0, int base = 10) const;
-    ulong toULong(bool *ok = 0, int base = 10) const;
-    qlonglong toLongLong(bool *ok = 0, int base = 10) const;
-    qulonglong toULongLong(bool *ok = 0, int base = 10) const;
-    float toFloat(bool *ok = 0) const;
-    double toDouble(bool *ok = 0) const;
+    short  toShort(bool *ok = Q_NULLPTR, int base = 10) const;
+    ushort toUShort(bool *ok = Q_NULLPTR, int base = 10) const;
+    int toInt(bool *ok = Q_NULLPTR, int base = 10) const;
+    uint toUInt(bool *ok = Q_NULLPTR, int base = 10) const;
+    long toLong(bool *ok = Q_NULLPTR, int base = 10) const;
+    ulong toULong(bool *ok = Q_NULLPTR, int base = 10) const;
+    qlonglong toLongLong(bool *ok = Q_NULLPTR, int base = 10) const;
+    qulonglong toULongLong(bool *ok = Q_NULLPTR, int base = 10) const;
+    float toFloat(bool *ok = Q_NULLPTR) const;
+    double toDouble(bool *ok = Q_NULLPTR) const;
 };
 Q_DECLARE_TYPEINFO(QStringRef, Q_PRIMITIVE_TYPE);
 
diff --git a/src/corelib/tools/qtextboundaryfinder.h b/src/corelib/tools/qtextboundaryfinder.h
index beec5de607..a79fb50dad 100644
--- a/src/corelib/tools/qtextboundaryfinder.h
+++ b/src/corelib/tools/qtextboundaryfinder.h
@@ -68,7 +68,7 @@ public:
     Q_DECLARE_FLAGS( BoundaryReasons, BoundaryReason )
 
     QTextBoundaryFinder(BoundaryType type, const QString &string);
-    QTextBoundaryFinder(BoundaryType type, const QChar *chars, int length, unsigned char *buffer = 0, int bufferSize = 0);
+    QTextBoundaryFinder(BoundaryType type, const QChar *chars, int length, unsigned char *buffer = Q_NULLPTR, int bufferSize = 0);
 
     inline bool isValid() const { return d; }
 
diff --git a/src/corelib/tools/qtimeline.h b/src/corelib/tools/qtimeline.h
index 21139b37a8..94e60dce45 100644
--- a/src/corelib/tools/qtimeline.h
+++ b/src/corelib/tools/qtimeline.h
@@ -70,7 +70,7 @@ public:
         CosineCurve
     };
 
-    explicit QTimeLine(int duration = 1000, QObject *parent = 0);
+    explicit QTimeLine(int duration = 1000, QObject *parent = Q_NULLPTR);
     virtual ~QTimeLine();
 
     State state() const;