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>

2 files changed, 13 insertions, 1 deletions

diff --git a/src/gui/painting/qtextureglyphcache.cpp b/src/gui/painting/qtextureglyphcache.cpp
index 4c879cf05d..056fd8b701 100644
--- a/src/gui/painting/qtextureglyphcache.cpp
+++ b/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);
diff --git a/src/gui/painting/qtextureglyphcache_p.h b/src/gui/painting/qtextureglyphcache_p.h
index c9e7060b0d..7dd8277a45 100644
--- a/src/gui/painting/qtextureglyphcache_p.h
+++ b/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;