Fix disconnect()ing from signals declared in a base class

Fix disconnection from pointer to member signal that belongs to the base
class, but whose type is a pointer to a member of the derived class.

Commit 9cc106d9d7d951fcf30f4b0f8606afa6b50892ec fixed connect, so apply
the same fix in disconnect

[ChangeLog][QtCore][QObject] Fixed disconnecting from pointer to member
signal that belongs in the base class but whose type is explicitly given
as a pointer to a member in the derived class

Task-number: QTBUG-40638
Change-Id: Ia546fc8f36e1ea0dd0645bdd820aea47f43677ac
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 5e8a97cdc0..e714168e16 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -4711,10 +4711,14 @@ bool QObject::disconnectImpl(const QObject *sender, void **signal, const QObject
     int signal_index = -1;
     if (signal) {
         void *args[] = { &signal_index, signal };
-        senderMetaObject->static_metacall(QMetaObject::IndexOfMethod, 0, args);
-        if (signal_index < 0 || signal_index >= QMetaObjectPrivate::get(senderMetaObject)->signalCount) {
-            qWarning("QObject::disconnect: signal not found in %s", senderMetaObject->className());
-            return false;
+        for (; senderMetaObject && signal_index < 0; senderMetaObject = senderMetaObject->superClass()) {
+            senderMetaObject->static_metacall(QMetaObject::IndexOfMethod, 0, args);
+            if (signal_index >= 0 && signal_index < QMetaObjectPrivate::get(senderMetaObject)->signalCount)
+                break;
+        }
+        if (!senderMetaObject) {
+            qWarning("QObject::disconnect: signal not found in %s", sender->metaObject()->className());
+            return QMetaObject::Connection(0);
         }
         signal_index += QMetaObjectPrivate::signalOffset(senderMetaObject);
     }