QDialogButtonBox: prevent crashes on deletions in slots

As usual, user code connected to signals emitted from Qt may destroy
an object's internal status while a signal is being emitted.

Guard a bit QDialogButtonBox signal emissions to prevent
crashes in case the button or a dialog get deleted from a slot
connected to clicked(). Also, be sure to emit the corresponding
accepted/rejected/etc. signal.

Change-Id: I7b1888070a8f2f56aa60923a17f90fb5efef145c
Task-number: QTBUG-45835
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/widgets/widgets/qdialogbuttonbox.cpp b/src/widgets/widgets/qdialogbuttonbox.cpp
index 237eb775b9..3e8c08f923 100644
--- a/src/widgets/widgets/qdialogbuttonbox.cpp
+++ b/src/widgets/widgets/qdialogbuttonbox.cpp
@@ -852,9 +852,19 @@ void QDialogButtonBoxPrivate::_q_handleButtonClicked()
 {
     Q_Q(QDialogButtonBox);
     if (QAbstractButton *button = qobject_cast<QAbstractButton *>(q->sender())) {
+        // Can't fetch this *after* emitting clicked, as clicked may destroy the button
+        // or change its role. Now changing the role is not possible yet, but arguably
+        // both clicked and accepted/rejected/etc. should be emitted "atomically"
+        // depending on whatever role the button had at the time of the click.
+        const QDialogButtonBox::ButtonRole buttonRole = q->buttonRole(button);
+        QPointer<QDialogButtonBox> guard(q);
+
         emit q->clicked(button);
 
-        switch (q->buttonRole(button)) {
+        if (!guard)
+            return;
+
+        switch (buttonRole) {
         case QPlatformDialogHelper::AcceptRole:
         case QPlatformDialogHelper::YesRole:
             emit q->accepted();