Fixed crashes relating to SVG icons.

Creating a second QFactoryLoader for the same plugins seems to trigger
an unload of the plugins loaded by the first factory loader. The
QIconEngine created by the SVG icon plugin thus gets an invalid virtual
table pointer, which causes a crash when attempting to call any virtual
function in the QIconEngine (pixmap(), the virtual destructor, etc).

Reusing a single QFactoryLoader instead fixes the crash.

Task-number: QTBUG-30496
Change-Id: I80c5fa8b52ab9b0db68499f8c37fad14a1ac4f3c
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/gui/image/qicon.cpp

@@ -483,6 +483,11 @@ void QPixmapIconEngine::virtual_hook(int id, void *data)
 #ifndef QT_NO_LIBRARY
 Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loader,
     (QIconEngineFactoryInterface_iid, QLatin1String("/iconengines"), Qt::CaseInsensitive))
+
+QFactoryLoader *qt_iconEngineFactoryLoader()
+{
+    return loader();
+}
 #endif
 
 

src/gui/image/qiconloader.cpp

@@ -104,6 +104,10 @@ static inline QStringList systemIconSearchPaths()
     return QStringList();
 }
 
+#ifndef QT_NO_LIBRARY
+extern QFactoryLoader *qt_iconEngineFactoryLoader(); // qicon.cpp
+#endif
+
 void QIconLoader::ensureInitialized()
 {
     if (!m_initialized) {
@@ -116,10 +120,7 @@ void QIconLoader::ensureInitialized()
         if (m_systemTheme.isEmpty())
             m_systemTheme = fallbackTheme();
 #ifndef QT_NO_LIBRARY
-        QFactoryLoader iconFactoryLoader(QIconEngineFactoryInterface_iid,
-                                         QLatin1String("/iconengines"),
-                                         Qt::CaseInsensitive);
-        if (iconFactoryLoader.keyMap().key(QLatin1String("svg"), -1) != -1)
+        if (qt_iconEngineFactoryLoader()->keyMap().key(QLatin1String("svg"), -1) != -1)
             m_supportsSvg = true;
 #endif //QT_NO_LIBRARY
     }