Q*GlyphCache: de-inline dtor and export vtable

The destructor is the first virtual method. By not defining it
out-of-line, we provoke multiple copies of vtables, not all of
which can be merged by the linker. If the linker fails, RTTI
such as dynamic_cast and catch-blocks involving the type will
not work.

Additionally, QFontEngineGlyphCache was not exported, and
therefore also not its vtable, making it impossible for
users outside of QtGui to get a unique RTTI for the class.

Change-Id: Ib265945934216bb609629431eb4c71996d4fd39d
Reported-by: Volker Krause <volker.krause@kdab.com>
Task-number: QTBUG-45582
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

src/gui/painting/qtextureglyphcache.cpp

@@ -42,6 +42,11 @@ QT_BEGIN_NAMESPACE
 
 // #define CACHE_DEBUG
 
+// out-of-line to avoid vtable duplication, breaking e.g. RTTI
+QTextureGlyphCache::~QTextureGlyphCache()
+{
+}
+
 int QTextureGlyphCache::calculateSubPixelPositionCount(glyph_t glyph) const
 {
     // Test 12 different subpixel positions since it factors into 3*4 so it gives
@@ -262,6 +267,11 @@ QImage QTextureGlyphCache::textureMapForGlyph(glyph_t g, QFixed subPixelPosition
  * QImageTextureGlyphCache
  */
 
+// out-of-line to avoid vtable duplication, breaking e.g. RTTI
+QImageTextureGlyphCache::~QImageTextureGlyphCache()
+{
+}
+
 void QImageTextureGlyphCache::resizeTextureData(int width, int height)
 {
     m_image = m_image.copy(0, 0, width, height);

src/gui/painting/qtextureglyphcache_p.h

@@ -72,7 +72,7 @@ public:
                                                m_w(0), m_h(0), m_cx(0), m_cy(0), m_currentRowHeight(0)
         { }
 
-    virtual ~QTextureGlyphCache() { }
+    ~QTextureGlyphCache();
 
     struct GlyphAndSubPixelPosition
     {
@@ -158,6 +158,8 @@ class Q_GUI_EXPORT QImageTextureGlyphCache : public QTextureGlyphCache
 public:
     QImageTextureGlyphCache(QFontEngine::GlyphFormat format, const QTransform &matrix)
         : QTextureGlyphCache(format, matrix) { }
+    ~QImageTextureGlyphCache();
+
     virtual void createTextureData(int width, int height) Q_DECL_OVERRIDE;
     virtual void resizeTextureData(int width, int height) Q_DECL_OVERRIDE;
     virtual void fillTexture(const Coord &c, glyph_t glyph, QFixed subPixelPosition) Q_DECL_OVERRIDE;

src/gui/text/qfontengineglyphcache.cpp

@@ -0,0 +1,43 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtGui 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 <private/qfontengineglyphcache_p.h>
+
+QT_BEGIN_NAMESPACE
+
+// out-of-line to avoid vtable duplication, breaking e.g. RTTI
+QFontEngineGlyphCache::~QFontEngineGlyphCache()
+{
+}
+
+QT_END_NAMESPACE

src/gui/text/qfontengineglyphcache_p.h

@@ -56,7 +56,7 @@
 
 QT_BEGIN_NAMESPACE
 
-class QFontEngineGlyphCache: public QSharedData
+class Q_GUI_EXPORT QFontEngineGlyphCache: public QSharedData
 {
 public:
     QFontEngineGlyphCache(QFontEngine::GlyphFormat format, const QTransform &matrix) : m_format(format), m_transform(matrix)
@@ -64,7 +64,7 @@ public:
         Q_ASSERT(m_format != QFontEngine::Format_None);
     }
 
-    virtual ~QFontEngineGlyphCache() { }
+    virtual ~QFontEngineGlyphCache();
 
     QFontEngine::GlyphFormat glyphFormat() const { return m_format; }
     const QTransform &transform() const { return m_transform; }

src/gui/text/text.pri

@@ -47,6 +47,7 @@ HEADERS += \
 SOURCES += \
     text/qfont.cpp \
     text/qfontengine.cpp \
+    text/qfontengineglyphcache.cpp \
     text/qfontsubset.cpp \
     text/qfontmetrics.cpp \
     text/qfontdatabase.cpp \