QML: Make Heap::Object and all subclasses trivial

GCC6 might dead-store-eliminate out our secret write to Base::mmdata,
because it expects all memory content to be "undefined" before
constructor calls. Clang might take the same approach if the constructor
of Heap::Object is removed.

By making these structs trivial, it also makes them memcpy-able.

Change-Id: I055b2ad28311b997fbe059849ebda4d5894eaa9b
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 27 insertions, 20 deletions

diff --git a/src/qml/types/qqmldelegatemodel.cpp b/src/qml/types/qqmldelegatemodel.cpp
index 02a5514275..395a3e5641 100644
--- a/src/qml/types/qqmldelegatemodel.cpp
+++ b/src/qml/types/qqmldelegatemodel.cpp
@@ -62,21 +62,24 @@ namespace QV4 {
 namespace Heap {
 
 struct DelegateModelGroupFunction : FunctionObject {
-    DelegateModelGroupFunction(QV4::ExecutionContext *scope, uint flag, QV4::ReturnedValue (*code)(QQmlDelegateModelItem *item, uint flag, const QV4::Value &arg));
+    void init(QV4::ExecutionContext *scope, uint flag, QV4::ReturnedValue (*code)(QQmlDelegateModelItem *item, uint flag, const QV4::Value &arg));
 
-    uint flag;
     QV4::ReturnedValue (*code)(QQmlDelegateModelItem *item, uint flag, const QV4::Value &arg);
+    uint flag;
 };
 
 struct QQmlDelegateModelGroupChange : Object {
-    QQmlDelegateModelGroupChange() {}
+    void init() { Object::init(); }
 
-    QQmlChangeSet::Change change;
+    QQmlChangeSet::ChangeData change;
 };
 
 struct QQmlDelegateModelGroupChangeArray : Object {
-    QQmlDelegateModelGroupChangeArray(const QVector<QQmlChangeSet::Change> &changes);
-    void destroy() { delete changes; }
+    void init(const QVector<QQmlChangeSet::Change> &changes);
+    void destroy() {
+        delete changes;
+    }
+
     QVector<QQmlChangeSet::Change> *changes;
 };
 
@@ -106,11 +109,11 @@ struct DelegateModelGroupFunction : QV4::FunctionObject
     }
 };
 
-Heap::DelegateModelGroupFunction::DelegateModelGroupFunction(QV4::ExecutionContext *scope, uint flag, QV4::ReturnedValue (*code)(QQmlDelegateModelItem *item, uint flag, const QV4::Value &arg))
-    : QV4::Heap::FunctionObject(scope, QStringLiteral("DelegateModelGroupFunction"))
-    , flag(flag)
-    , code(code)
+void Heap::DelegateModelGroupFunction::init(QV4::ExecutionContext *scope, uint flag, QV4::ReturnedValue (*code)(QQmlDelegateModelItem *item, uint flag, const QV4::Value &arg))
 {
+    QV4::Heap::FunctionObject::init(scope, QStringLiteral("DelegateModelGroupFunction"));
+    this->flag = flag;
+    this->code = code;
 }
 
 }
@@ -3300,9 +3303,10 @@ public:
     }
 };
 
-QV4::Heap::QQmlDelegateModelGroupChangeArray::QQmlDelegateModelGroupChangeArray(const QVector<QQmlChangeSet::Change> &changes)
-    : changes(new QVector<QQmlChangeSet::Change>(changes))
+void QV4::Heap::QQmlDelegateModelGroupChangeArray::init(const QVector<QQmlChangeSet::Change> &changes)
 {
+    Object::init();
+    this->changes = new QVector<QQmlChangeSet::Change>(changes);
     QV4::Scope scope(internalClass->engine);
     QV4::ScopedObject o(scope, this);
     o->setArrayType(QV4::Heap::ArrayData::Custom);
diff --git a/src/qml/types/qqmldelegatemodel_p_p.h b/src/qml/types/qqmldelegatemodel_p_p.h
index a34450ebd6..6cb82fddfc 100644
--- a/src/qml/types/qqmldelegatemodel_p_p.h
+++ b/src/qml/types/qqmldelegatemodel_p_p.h
@@ -160,7 +160,7 @@ protected:
 namespace QV4 {
 namespace Heap {
 struct QQmlDelegateModelItemObject : Object {
-    inline QQmlDelegateModelItemObject(QQmlDelegateModelItem *item);
+    inline void init(QQmlDelegateModelItem *item);
     void destroy();
     QQmlDelegateModelItem *item;
 };
@@ -174,9 +174,10 @@ struct QQmlDelegateModelItemObject : QV4::Object
     V4_NEEDS_DESTROY
 };
 
-QV4::Heap::QQmlDelegateModelItemObject::QQmlDelegateModelItemObject(QQmlDelegateModelItem *item)
-    : item(item)
+void QV4::Heap::QQmlDelegateModelItemObject::init(QQmlDelegateModelItem *item)
 {
+    Object::init();
+    this->item = item;
 }
 
 
diff --git a/src/qml/types/qqmllistmodel_p_p.h b/src/qml/types/qqmllistmodel_p_p.h
index d3ff032ae9..bd2102679b 100644
--- a/src/qml/types/qqmllistmodel_p_p.h
+++ b/src/qml/types/qqmllistmodel_p_p.h
@@ -162,11 +162,12 @@ namespace QV4 {
 namespace Heap {
 
 struct ModelObject : public QObjectWrapper {
-    ModelObject(QObject *object, QQmlListModel *model, int elementIndex)
-        : QObjectWrapper(object)
-        , m_model(model)
-        , m_elementIndex(elementIndex)
-    {}
+    void init(QObject *object, QQmlListModel *model, int elementIndex)
+    {
+        QObjectWrapper::init(object);
+        m_model = model;
+        m_elementIndex = elementIndex;
+    }
     QQmlListModel *m_model;
     int m_elementIndex;
 };
@@ -180,6 +181,7 @@ struct ModelObject : public QObjectWrapper
     static void advanceIterator(Managed *m, ObjectIterator *it, Value *name, uint *index, Property *p, PropertyAttributes *attributes);
 
     V4_OBJECT2(ModelObject, QObjectWrapper)
+    V4_NEEDS_DESTROY
 };
 
 } // namespace QV4