QQmlRefCount: de-virtualize dtor

Now that QQmlRefCounted ensures no-one uses ~QQmlRefCount() directly
anymore, we can make it non-virtual, shrinking the
sizeof(QQmlRefCount) from 8/16 to 4/4 bytes (32/64 bit platforms).

This requires moving the release() function from QQmlRefCount down
into QQmlRefCounted<T>, and static_cast'ing *this to T before calling
delete.

We need to be careful, of course, that no derived class relied on the
implied virtualness of ~QQmlRefCount() making their dtors virtual, so
require that all classes that use QQmlRefCounted are either final or
have a virtual destructor.

Update the toolsupport test and the TypeInformationVersion, as
sizeof(QQmlRefCount) was one the items checked.

Fixes: QTBUG-114817
Change-Id: I69afd36ec5b63313842c1438e0244503603ed96f
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/qml/qml/qqmlopenmetaobject_p.h b/src/qml/qml/qqmlopenmetaobject_p.h
index eb2532b5d3..5dcb8e9a86 100644
--- a/src/qml/qml/qqmlopenmetaobject_p.h
+++ b/src/qml/qml/qqmlopenmetaobject_p.h
@@ -28,12 +28,12 @@ QT_BEGIN_NAMESPACE
 class QQmlEngine;
 class QMetaPropertyBuilder;
 class QQmlOpenMetaObjectTypePrivate;
-class Q_QML_PRIVATE_EXPORT QQmlOpenMetaObjectType
+class Q_QML_PRIVATE_EXPORT QQmlOpenMetaObjectType final
     : public QQmlRefCounted<QQmlOpenMetaObjectType>
 {
 public:
     QQmlOpenMetaObjectType(const QMetaObject *base);
-    ~QQmlOpenMetaObjectType() override;
+    ~QQmlOpenMetaObjectType();
 
     void createProperties(const QVector<QByteArray> &names);
     int createProperty(const QByteArray &name);