De-duplicate vtables, part II: exported public 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 second and last batch, we de-inline destructors of exported
public classes.

Since they are already exported, users of these classes are unaffected
by the change, but since it's public API, and the dtors may have been
de-virtualized and inlined into application code, we need to avoid
adding code to the out-of-line destructor until Qt 6.

Change-Id: Ieda9553cb4b0dae7217c37cc7cde321dd7302122
Reported-by: Volker Krause <volker.krause@kdab.com>
Task-number: QTBUG-45582
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/plugin/plugin.pri

@@ -13,6 +13,7 @@ HEADERS += \
         plugin/qmachparser_p.h
 
 SOURCES += \
+	plugin/qfactoryinterface.cpp \
 	plugin/qpluginloader.cpp \
 	plugin/qfactoryloader.cpp \
 	plugin/quuid.cpp \

src/corelib/plugin/qfactoryinterface.cpp

@@ -0,0 +1,43 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qfactoryinterface.h"
+
+QT_BEGIN_NAMESPACE
+
+QFactoryInterface::~QFactoryInterface()
+{
+    // must be empty until ### Qt 6
+}
+
+QT_END_NAMESPACE

src/corelib/plugin/qfactoryinterface.h

@@ -42,7 +42,7 @@ QT_BEGIN_NAMESPACE
 
 struct Q_CORE_EXPORT QFactoryInterface
 {
-    virtual ~QFactoryInterface() {}
+    virtual ~QFactoryInterface();
     virtual QStringList keys() const = 0;
 };
 

src/gui/kernel/qevent.cpp

@@ -1971,6 +1971,11 @@ QInputMethodEvent::QInputMethodEvent(const QInputMethodEvent &other)
 {
 }
 
+QInputMethodEvent::~QInputMethodEvent()
+{
+    // must be empty until ### Qt 6
+}
+
 /*!
     Sets the commit string to \a commitString.
 

src/gui/kernel/qevent.h

@@ -531,6 +531,8 @@ public:
     };
     QInputMethodEvent();
     QInputMethodEvent(const QString &preeditText, const QList<Attribute> &attributes);
+    ~QInputMethodEvent();
+
     void setCommitString(const QString &commitString, int replaceFrom = 0, int replaceLength = 0);
     inline const QList<Attribute> &attributes() const { return attrs; }
     inline const QString &preeditString() const { return preedit; }

src/gui/text/qabstracttextdocumentlayout.cpp

@@ -44,6 +44,11 @@ QAbstractTextDocumentLayoutPrivate::~QAbstractTextDocumentLayoutPrivate()
 {
 }
 
+QTextObjectInterface::~QTextObjectInterface()
+{
+    // must be empty until ### Qt 6
+}
+
 /*!
     \class QAbstractTextDocumentLayout
     \reentrant

src/gui/text/qabstracttextdocumentlayout.h

@@ -126,7 +126,7 @@ private:
 class Q_GUI_EXPORT QTextObjectInterface
 {
 public:
-    virtual ~QTextObjectInterface() {}
+    virtual ~QTextObjectInterface();
     virtual QSizeF intrinsicSize(QTextDocument *doc, int posInDocument, const QTextFormat &format) = 0;
     virtual void drawObject(QPainter *painter, const QRectF &rect, QTextDocument *doc, int posInDocument, const QTextFormat &format) = 0;
 };