Fix UB in tst_QDialog::showExtension()

Don't cast a QDialog to a subclass it is not.

Fix by creating it as the required subclass in the
first place.

Found by UBSan:
  tests/auto/widgets/dialogs/qdialog/tst_qdialog.cpp:203:20: runtime error: downcast of address 0x2b5f5000ad40 which does not point to an object of type 'DummyDialog'
  tests/auto/widgets/dialogs/qdialog/tst_qdialog.cpp:203:46: runtime error: member call on address 0x2b5f5000ad40 which does not point to an object of type 'DummyDialog'

Change-Id: I63ae7e782bda6a78d11af5c2bc2f7d88aacd0ac0
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

1 files changed, 12 insertions, 11 deletions

diff --git a/tests/auto/widgets/dialogs/qdialog/tst_qdialog.cpp b/tests/auto/widgets/dialogs/qdialog/tst_qdialog.cpp
index e62ce3ceb5..a23938959b 100644
--- a/tests/auto/widgets/dialogs/qdialog/tst_qdialog.cpp
+++ b/tests/auto/widgets/dialogs/qdialog/tst_qdialog.cpp
@@ -49,6 +49,14 @@
 
 QT_FORWARD_DECLARE_CLASS(QDialog)
 
+// work around function being protected
+class DummyDialog : public QDialog
+{
+public:
+    DummyDialog(): QDialog(0, Qt::X11BypassWindowManagerHint) {}
+    using QDialog::showExtension;
+};
+
 class tst_QDialog : public QObject
 {
     Q_OBJECT
@@ -82,7 +90,7 @@ private slots:
     void transientParent();
 
 private:
-    QDialog *testWidget;
+    DummyDialog *testWidget;
 };
 
 // Testing get/set functions
@@ -108,13 +116,6 @@ void tst_QDialog::getSetCheck()
     QCOMPARE(INT_MAX, obj1.result());
 }
 
-// work around function being protected
-class DummyDialog : public QDialog {
-public:
-    DummyDialog(): QDialog(0) {}
-    void showExtension( bool b ) { QDialog::showExtension( b ); }
-};
-
 class ToolDialog : public QDialog
 {
 public:
@@ -148,7 +149,7 @@ tst_QDialog::tst_QDialog()
 void tst_QDialog::initTestCase()
 {
     // Create the test class
-    testWidget = new QDialog(0, Qt::X11BypassWindowManagerHint);
+    testWidget = new DummyDialog;
     testWidget->resize(200,200);
     testWidget->show();
     qApp->setActiveWindow(testWidget);
@@ -193,7 +194,7 @@ void tst_QDialog::showExtension()
     QPoint oldPosition = testWidget->pos();
 
     // show
-    ((DummyDialog*)testWidget)->showExtension( true );
+    testWidget->showExtension( true );
 //     while ( testWidget->size() == dlgSize )
 //         qApp->processEvents();
 
@@ -202,7 +203,7 @@ void tst_QDialog::showExtension()
     QCOMPARE(testWidget->pos(), oldPosition);
 
     // hide extension. back to old size ?
-    ((DummyDialog*)testWidget)->showExtension( false );
+    testWidget->showExtension( false );
     QCOMPARE( testWidget->size(), dlgSize );
 
     testWidget->setExtension( 0 );