Accessibility: Fix leaking cached interfaces

When the application closes, we should clear the cache to not run into
memory sanitizers claiming that we leak.

Change-Id: Ibf9fcda107be6b7f3ed414d7651080aa1f61a3a5
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

src/gui/accessible/qaccessiblecache.cpp

@@ -57,6 +57,12 @@ static void cleanupAccessibleCache()
     accessibleCache = nullptr;
 }
 
+QAccessibleCache::~QAccessibleCache()
+{
+    for (QAccessibleInterface *iface: idToInterface.values())
+        delete iface;
+}
+
 QAccessibleCache *QAccessibleCache::instance()
 {
     if (!accessibleCache) {

src/gui/accessible/qaccessiblecache_p.h

@@ -68,6 +68,7 @@ class Q_GUI_EXPORT QAccessibleCache  :public QObject
     Q_OBJECT
 
 public:
+    ~QAccessibleCache() override;
     static QAccessibleCache *instance();
     QAccessibleInterface *interfaceForId(QAccessible::Id id) const;
     QAccessible::Id idForInterface(QAccessibleInterface *iface) const;

tests/auto/other/qaccessibility/tst_qaccessibility.cpp

@@ -876,6 +876,10 @@ void tst_QAccessibility::applicationTest()
     QCOMPARE(interface->child(1), static_cast<QAccessibleInterface*>(0));
     QCOMPARE(interface->childCount(), 0);
 
+    // Check that asking for the application interface twice returns the same object
+    QAccessibleInterface *app2 = QAccessible::queryAccessibleInterface(qApp);
+    QCOMPARE(interface, app2);
+
     QWidget widget;
     widget.show();
     qApp->setActiveWindow(&widget);