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>

4 files changed, 11 insertions, 4 deletions

diff --git a/src/gui/painting/qpagedpaintdevice.cpp b/src/gui/painting/qpagedpaintdevice.cpp
index 3adc5e9411..547cedf51f 100644
--- a/src/gui/painting/qpagedpaintdevice.cpp
+++ b/src/gui/painting/qpagedpaintdevice.cpp
@@ -36,6 +36,10 @@
 
 QT_BEGIN_NAMESPACE
 
+QPagedPaintDevicePrivate::~QPagedPaintDevicePrivate()
+{
+}
+
 /*!
     \class QPagedPaintDevice
     \inmodule QtGui
diff --git a/src/gui/painting/qpagedpaintdevice_p.h b/src/gui/painting/qpagedpaintdevice_p.h
index 62f69747db..30b1c0a1e6 100644
--- a/src/gui/painting/qpagedpaintdevice_p.h
+++ b/src/gui/painting/qpagedpaintdevice_p.h
@@ -61,9 +61,7 @@ public:
     {
     }
 
-    virtual ~QPagedPaintDevicePrivate()
-    {
-    }
+    virtual ~QPagedPaintDevicePrivate();
 
     // ### Qt6 Remove these and make public class methods virtual
     virtual bool setPageLayout(const QPageLayout &newPageLayout)
diff --git a/src/gui/painting/qpaintengine.cpp b/src/gui/painting/qpaintengine.cpp
index 6271c8f9e6..bf1f31a85b 100644
--- a/src/gui/painting/qpaintengine.cpp
+++ b/src/gui/painting/qpaintengine.cpp
@@ -968,6 +968,10 @@ QRect QPaintEngine::systemRect() const
     return d_func()->systemRect;
 }
 
+QPaintEnginePrivate::~QPaintEnginePrivate()
+{
+}
+
 void QPaintEnginePrivate::drawBoxTextItem(const QPointF &p, const QTextItemInt &ti)
 {
     if (!ti.glyphs.numGlyphs)
diff --git a/src/gui/painting/qpaintengine_p.h b/src/gui/painting/qpaintengine_p.h
index c58662ede4..918c98997b 100644
--- a/src/gui/painting/qpaintengine_p.h
+++ b/src/gui/painting/qpaintengine_p.h
@@ -60,7 +60,8 @@ class Q_GUI_EXPORT QPaintEnginePrivate
 public:
     QPaintEnginePrivate() : pdev(0), q_ptr(0), currentClipDevice(0), hasSystemTransform(0),
                             hasSystemViewport(0) {}
-    virtual ~QPaintEnginePrivate() { }
+    virtual ~QPaintEnginePrivate();
+
     QPaintDevice *pdev;
     QPaintEngine *q_ptr;
     QRegion systemClip;