De-duplicate vtables, part I: exported private classes

By making the destructor (usually the first non-inline, non-pure,
virtual function, and therefore the trigger for most compilers to
emit the vtable and type_info structures for the class in that TU)
out-of-line, vtables and, more importantly, type_info structures for
the class are pinned to a single TU. This prevents false negative
dynamic_cast and catch evaluation.

In this first batch, we de-inline destructors of exported private
classes.

Since they are already exported, users of these classes are unaffected
by the change, and since it's private API, we don't need to avoid
adding code to the out-of-line destructor until Qt 6.

Change-Id: I450707877d2cb6a77f79ae1dd355facb98d6c517
Reported-by: Volker Krause <volker.krause@kdab.com>
Task-number: QTBUG-45582
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/corelib/kernel/qobject_p.h b/src/corelib/kernel/qobject_p.h
index 1b64103e40..bd5ee006bf 100644
--- a/src/corelib/kernel/qobject_p.h
+++ b/src/corelib/kernel/qobject_p.h
@@ -406,7 +406,7 @@ void Q_CORE_EXPORT qDeleteInEventHandler(QObject *o);
 struct QAbstractDynamicMetaObject;
 struct Q_CORE_EXPORT QDynamicMetaObjectData
 {
-    virtual ~QDynamicMetaObjectData() {}
+    virtual ~QDynamicMetaObjectData();
     virtual void objectDestroyed(QObject *) { delete this; }
 
     virtual QAbstractDynamicMetaObject *toDynamicMetaObject(QObject *) = 0;
@@ -415,6 +415,8 @@ struct Q_CORE_EXPORT QDynamicMetaObjectData
 
 struct Q_CORE_EXPORT QAbstractDynamicMetaObject : public QDynamicMetaObjectData, public QMetaObject
 {
+    ~QAbstractDynamicMetaObject();
+
     virtual QAbstractDynamicMetaObject *toDynamicMetaObject(QObject *) Q_DECL_OVERRIDE { return this; }
     virtual int createProperty(const char *, const char *) { return -1; }
     virtual int metaCall(QObject *, QMetaObject::Call c, int _id, void **a) Q_DECL_OVERRIDE