Remove the manual vtable from QQmlJavaScriptExpression

Now that the class got unified with QQmlAbstractExpression, it has a
vtable anyway, so we can just as well remove the old hack.

Change-Id: Ifa095297e3d75564c4305ce3655eaa57436ef4a8
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

8 files changed, 45 insertions, 78 deletions

diff --git a/src/qml/qml/qqmlbinding.cpp b/src/qml/qml/qqmlbinding.cpp
index 2a53365f69..9123825f65 100644
--- a/src/qml/qml/qqmlbinding.cpp
+++ b/src/qml/qml/qqmlbinding.cpp
@@ -62,13 +62,8 @@ QQmlAbstractBinding::VTable QQmlBinding_vtable = {
 
 QQmlBinding::Identifier QQmlBinding::Invalid = -1;
 
-static QQmlJavaScriptExpression::VTable QQmlBinding_jsvtable = {
-    QQmlBinding::expressionIdentifier,
-    QQmlBinding::expressionChanged
-};
-
 QQmlBinding::QQmlBinding(const QString &str, QObject *obj, QQmlContext *ctxt)
-: QQmlJavaScriptExpression(&QQmlBinding_jsvtable), QQmlAbstractBinding(Binding)
+: QQmlJavaScriptExpression(), QQmlAbstractBinding(Binding)
 {
     setNotifyOnValueChanged(true);
     QQmlJavaScriptExpression::setContext(QQmlContextData::get(ctxt));
@@ -79,7 +74,7 @@ QQmlBinding::QQmlBinding(const QString &str, QObject *obj, QQmlContext *ctxt)
 }
 
 QQmlBinding::QQmlBinding(const QQmlScriptString &script, QObject *obj, QQmlContext *ctxt)
-: QQmlJavaScriptExpression(&QQmlBinding_jsvtable), QQmlAbstractBinding(Binding)
+: QQmlJavaScriptExpression(), QQmlAbstractBinding(Binding)
 {
     if (ctxt && !ctxt->isValid())
         return;
@@ -113,7 +108,7 @@ QQmlBinding::QQmlBinding(const QQmlScriptString &script, QObject *obj, QQmlConte
 }
 
 QQmlBinding::QQmlBinding(const QString &str, QObject *obj, QQmlContextData *ctxt)
-: QQmlJavaScriptExpression(&QQmlBinding_jsvtable), QQmlAbstractBinding(Binding)
+: QQmlJavaScriptExpression(), QQmlAbstractBinding(Binding)
 {
     setNotifyOnValueChanged(true);
     QQmlJavaScriptExpression::setContext(ctxt);
@@ -126,7 +121,7 @@ QQmlBinding::QQmlBinding(const QString &str, QObject *obj, QQmlContextData *ctxt
 QQmlBinding::QQmlBinding(const QString &str, QObject *obj,
                          QQmlContextData *ctxt,
                          const QString &url, quint16 lineNumber, quint16 columnNumber)
-: QQmlJavaScriptExpression(&QQmlBinding_jsvtable), QQmlAbstractBinding(Binding)
+: QQmlJavaScriptExpression(), QQmlAbstractBinding(Binding)
 {
     Q_UNUSED(columnNumber);
     setNotifyOnValueChanged(true);
@@ -138,7 +133,7 @@ QQmlBinding::QQmlBinding(const QString &str, QObject *obj,
 }
 
 QQmlBinding::QQmlBinding(const QV4::Value &functionPtr, QObject *obj, QQmlContextData *ctxt)
-: QQmlJavaScriptExpression(&QQmlBinding_jsvtable), QQmlAbstractBinding(Binding)
+: QQmlJavaScriptExpression(), QQmlAbstractBinding(Binding)
 {
     setNotifyOnValueChanged(true);
     QQmlJavaScriptExpression::setContext(ctxt);
@@ -238,13 +233,11 @@ QVariant QQmlBinding::evaluate()
     return scope.engine->toVariant(result, qMetaTypeId<QList<QObject*> >());
 }
 
-QString QQmlBinding::expressionIdentifier(QQmlJavaScriptExpression *e)
+QString QQmlBinding::expressionIdentifier()
 {
-    QQmlBinding *This = static_cast<QQmlBinding *>(e);
-
-    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(This->context()->engine);
+    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context()->engine);
     QV4::Scope scope(ep->v4engine());
-    QV4::ScopedValue f(scope, This->v4function.value());
+    QV4::ScopedValue f(scope, v4function.value());
     QV4::Function *function = f->as<QV4::FunctionObject>()->function();
 
     QString url = function->sourceFile();
@@ -254,10 +247,9 @@ QString QQmlBinding::expressionIdentifier(QQmlJavaScriptExpression *e)
     return url + QLatin1Char(':') + QString::number(lineNumber) + QLatin1Char(':') + QString::number(columnNumber);
 }
 
-void QQmlBinding::expressionChanged(QQmlJavaScriptExpression *e)
+void QQmlBinding::expressionChanged()
 {
-    QQmlBinding *This = static_cast<QQmlBinding *>(e);
-    This->update();
+    update();
 }
 
 void QQmlBinding::refresh()
diff --git a/src/qml/qml/qqmlbinding_p.h b/src/qml/qml/qqmlbinding_p.h
index 79c61574a5..4f1c27c248 100644
--- a/src/qml/qml/qqmlbinding_p.h
+++ b/src/qml/qml/qqmlbinding_p.h
@@ -104,8 +104,8 @@ public:
 
     QVariant evaluate();
 
-    static QString expressionIdentifier(QQmlJavaScriptExpression *);
-    static void expressionChanged(QQmlJavaScriptExpression *);
+    virtual QString expressionIdentifier();
+    virtual void expressionChanged();
 
 protected:
     friend class QQmlAbstractBinding;
diff --git a/src/qml/qml/qqmlboundsignal.cpp b/src/qml/qml/qqmlboundsignal.cpp
index 387c162b82..c24cfed2ff 100644
--- a/src/qml/qml/qqmlboundsignal.cpp
+++ b/src/qml/qml/qqmlboundsignal.cpp
@@ -55,11 +55,6 @@
 
 QT_BEGIN_NAMESPACE
 
-static QQmlJavaScriptExpression::VTable QQmlBoundSignalExpression_jsvtable = {
-    QQmlBoundSignalExpression::expressionIdentifier,
-    QQmlBoundSignalExpression::expressionChanged
-};
-
 QQmlBoundSignalExpression::ExtraData::ExtraData(const QString &handlerName, const QString &parameterString,
                                                 const QString &expression, const QString &fileName,
                                                 quint16 line, quint16 column)
@@ -75,7 +70,7 @@ QQmlBoundSignalExpression::QQmlBoundSignalExpression(QObject *target, int index,
                                                      const QString &fileName, quint16 line, quint16 column,
                                                      const QString &handlerName,
                                                      const QString &parameterString)
-    : QQmlJavaScriptExpression(&QQmlBoundSignalExpression_jsvtable),
+    : QQmlJavaScriptExpression(),
       m_index(index),
       m_target(target),
       m_extra(new ExtraData(handlerName, parameterString, expression, fileName, line, column))
@@ -87,7 +82,7 @@ QQmlBoundSignalExpression::QQmlBoundSignalExpression(QObject *target, int index,
 }
 
 QQmlBoundSignalExpression::QQmlBoundSignalExpression(QObject *target, int index, QQmlContextData *ctxt, QObject *scope, const QV4::Value &function)
-    : QQmlJavaScriptExpression(&QQmlBoundSignalExpression_jsvtable),
+    : QQmlJavaScriptExpression(),
       m_index(index),
       m_function(function.as<QV4::Object>()->engine(), function),
       m_target(target),
@@ -100,7 +95,7 @@ QQmlBoundSignalExpression::QQmlBoundSignalExpression(QObject *target, int index,
 }
 
 QQmlBoundSignalExpression::QQmlBoundSignalExpression(QObject *target, int index, QQmlContextData *ctxt, QObject *scope, QV4::Function *runtimeFunction)
-    : QQmlJavaScriptExpression(&QQmlBoundSignalExpression_jsvtable),
+    : QQmlJavaScriptExpression(),
       m_index(index),
       m_target(target),
       m_extra(0)
@@ -137,14 +132,13 @@ QQmlBoundSignalExpression::~QQmlBoundSignalExpression()
     delete m_extra.data();
 }
 
-QString QQmlBoundSignalExpression::expressionIdentifier(QQmlJavaScriptExpression *e)
+QString QQmlBoundSignalExpression::expressionIdentifier()
 {
-    QQmlBoundSignalExpression *This = static_cast<QQmlBoundSignalExpression *>(e);
-    QQmlSourceLocation loc = This->sourceLocation();
+    QQmlSourceLocation loc = sourceLocation();
     return loc.sourceFile + QLatin1Char(':') + QString::number(loc.line);
 }
 
-void QQmlBoundSignalExpression::expressionChanged(QQmlJavaScriptExpression *)
+void QQmlBoundSignalExpression::expressionChanged()
 {
     // bound signals do not notify on change.
 }
diff --git a/src/qml/qml/qqmlboundsignal_p.h b/src/qml/qml/qqmlboundsignal_p.h
index c65742da8a..fb9c878fd2 100644
--- a/src/qml/qml/qqmlboundsignal_p.h
+++ b/src/qml/qml/qqmlboundsignal_p.h
@@ -72,9 +72,9 @@ public:
     QQmlBoundSignalExpression(QObject *target, int index,
                               QQmlContextData *ctxt, QObject *scope, QV4::Function *runtimeFunction);
 
-    // "inherited" from QQmlJavaScriptExpression.
-    static QString expressionIdentifier(QQmlJavaScriptExpression *);
-    static void expressionChanged(QQmlJavaScriptExpression *);
+    // inherited from QQmlJavaScriptExpression.
+    virtual QString expressionIdentifier();
+    virtual void expressionChanged();
 
     // evaluation of a bound signal expression doesn't return any value
     void evaluate(void **a);
diff --git a/src/qml/qml/qqmlexpression.cpp b/src/qml/qml/qqmlexpression.cpp
index 9617e430b8..f84a5c2e16 100644
--- a/src/qml/qml/qqmlexpression.cpp
+++ b/src/qml/qml/qqmlexpression.cpp
@@ -45,13 +45,8 @@
 
 QT_BEGIN_NAMESPACE
 
-static QQmlJavaScriptExpression::VTable QQmlExpressionPrivate_jsvtable = {
-    QQmlExpressionPrivate::expressionIdentifier,
-    QQmlExpressionPrivate::expressionChanged
-};
-
 QQmlExpressionPrivate::QQmlExpressionPrivate()
-: QQmlJavaScriptExpression(&QQmlExpressionPrivate_jsvtable),
+: QQmlJavaScriptExpression(),
   expressionFunctionValid(true),
   line(0), column(0)
 {
@@ -432,22 +427,15 @@ QQmlError QQmlExpression::error() const
     calling QQmlExpression::evaluate()) before this signal will be emitted.
 */
 
-void QQmlExpressionPrivate::expressionChanged(QQmlJavaScriptExpression *e)
-{
-    QQmlExpressionPrivate *This = static_cast<QQmlExpressionPrivate *>(e);
-    This->expressionChanged();
-}
-
 void QQmlExpressionPrivate::expressionChanged()
 {
     Q_Q(QQmlExpression);
     emit q->valueChanged();
 }
 
-QString QQmlExpressionPrivate::expressionIdentifier(QQmlJavaScriptExpression *e)
+QString QQmlExpressionPrivate::expressionIdentifier()
 {
-    QQmlExpressionPrivate *This = static_cast<QQmlExpressionPrivate *>(e);
-    return QLatin1Char('"') + This->expression + QLatin1Char('"');
+    return QLatin1Char('"') + expression + QLatin1Char('"');
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/qqmlexpression_p.h b/src/qml/qml/qqmlexpression_p.h
index f1c02c51b0..f7fb7cb7c3 100644
--- a/src/qml/qml/qqmlexpression_p.h
+++ b/src/qml/qml/qqmlexpression_p.h
@@ -80,9 +80,8 @@ public:
 
     bool expressionFunctionValid:1;
 
-    // "Inherited" from QQmlJavaScriptExpression
-    static QString expressionIdentifier(QQmlJavaScriptExpression *);
-    static void expressionChanged(QQmlJavaScriptExpression *);
+    // Inherited from QQmlJavaScriptExpression
+    virtual QString expressionIdentifier();
     virtual void expressionChanged();
 
     QString expression;
diff --git a/src/qml/qml/qqmljavascriptexpression.cpp b/src/qml/qml/qqmljavascriptexpression.cpp
index 41599a9f42..204f917e41 100644
--- a/src/qml/qml/qqmljavascriptexpression.cpp
+++ b/src/qml/qml/qqmljavascriptexpression.cpp
@@ -83,8 +83,8 @@ void QQmlDelayedError::catchJavaScriptException(QV4::ExecutionEngine *engine)
 }
 
 
-QQmlJavaScriptExpression::QQmlJavaScriptExpression(VTable *v)
-    : m_vtable(v),
+QQmlJavaScriptExpression::QQmlJavaScriptExpression()
+    : m_error(0),
       m_context(0),
       m_prevExpression(0),
       m_nextExpression(0)
@@ -257,7 +257,7 @@ void QQmlJavaScriptExpression::GuardCapture::captureProperty(QObject *o, int c,
         if (!errorString) {
             errorString = new QStringList;
             QString preamble = QLatin1String("QQmlExpression: Expression ") +
-                    expression->m_vtable->expressionIdentifier(expression) +
+                    expression->expressionIdentifier() +
                     QLatin1String(" depends on non-NOTIFYable properties:");
             errorString->append(preamble);
         }
@@ -292,25 +292,26 @@ void QQmlJavaScriptExpression::GuardCapture::captureProperty(QObject *o, int c,
 
 void QQmlJavaScriptExpression::clearError()
 {
-    if (m_vtable.hasValue()) {
-        m_vtable.value().clearError();
-        m_vtable.value().removeError();
-    }
+    if (m_error)
+        delete m_error;
+    m_error = 0;
 }
 
 QQmlError QQmlJavaScriptExpression::error(QQmlEngine *engine) const
 {
     Q_UNUSED(engine);
 
-    if (m_vtable.hasValue())
-        return m_vtable.constValue()->error();
+    if (m_error)
+        return m_error->error();
     else
         return QQmlError();
 }
 
 QQmlDelayedError *QQmlJavaScriptExpression::delayedError()
 {
-    return &m_vtable.value();
+    if (!m_error)
+        m_error = new QQmlDelayedError;
+    return m_error;
 }
 
 QV4::ReturnedValue
@@ -392,7 +393,7 @@ void QQmlJavaScriptExpressionGuard_callback(QQmlNotifierEndpoint *e, void **)
     QQmlJavaScriptExpression *expression =
         static_cast<QQmlJavaScriptExpressionGuard *>(e)->expression;
 
-    expression->m_vtable->expressionChanged(expression);
+    expression->expressionChanged();
 }
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/qqmljavascriptexpression_p.h b/src/qml/qml/qqmljavascriptexpression_p.h
index c8f54527a0..f9f304a524 100644
--- a/src/qml/qml/qqmljavascriptexpression_p.h
+++ b/src/qml/qml/qqmljavascriptexpression_p.h
@@ -92,19 +92,12 @@ private:
 class Q_QML_PRIVATE_EXPORT QQmlJavaScriptExpression
 {
 public:
-    // Although this looks crazy, we implement our own "vtable" here, rather than relying on
-    // C++ virtuals, to save memory.  By doing it ourselves, we can overload the storage
-    // location that is use for the vtable to also store the rarely used delayed error.
-    // If we use C++ virtuals, we can't do this and it consts us an extra sizeof(void *) in
-    // memory for every expression.
-    struct VTable {
-        QString (*expressionIdentifier)(QQmlJavaScriptExpression *);
-        void (*expressionChanged)(QQmlJavaScriptExpression *);
-    };
-
-    QQmlJavaScriptExpression(VTable *vtable);
+    QQmlJavaScriptExpression();
     virtual ~QQmlJavaScriptExpression();
 
+    virtual QString expressionIdentifier() = 0;
+    virtual void expressionChanged() = 0;
+
     QV4::ReturnedValue evaluate(QQmlContextData *, const QV4::Value &function, bool *isUndefined);
     QV4::ReturnedValue evaluate(QQmlContextData *, const QV4::Value &function, QV4::CallData *callData, bool *isUndefined);
 
@@ -176,7 +169,7 @@ private:
         QStringList *errorString;
     };
 
-    QPointerValuePair<VTable, QQmlDelayedError> m_vtable;
+    QQmlDelayedError *m_error;
 
     // We store some flag bits in the following flag pointers.
     //    activeGuards:flag1  - notifyOnValueChanged
@@ -234,12 +227,12 @@ void QQmlJavaScriptExpression::setScopeObject(QObject *v)
 
 bool QQmlJavaScriptExpression::hasError() const
 {
-    return m_vtable.hasValue() && m_vtable.constValue()->isValid();
+    return m_error && m_error->isValid();
 }
 
 bool QQmlJavaScriptExpression::hasDelayedError() const
 {
-    return m_vtable.hasValue();
+    return m_error;
 }
 
 QQmlJavaScriptExpressionGuard::QQmlJavaScriptExpressionGuard(QQmlJavaScriptExpression *e)