QObject: Extend debug output of connect

Sometimes it is hard to find the line, when the warning
"QObject::connect: invalid null parameter" appears in the log.
This change adds the class names of the sender and receiver
to give a hint where to search for the wrong call to connect.

Change-Id: I00cead7d943f96d60f198cb3f0bed34ba10285c5
Reviewed-by: André Hartmann <aha_1980@gmx.de>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index dcc1bb5814..25d17ecd6b 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -4802,7 +4802,12 @@ QMetaObject::Connection QObjectPrivate::connectImpl(const QObject *sender, int s
                                              const int *types, const QMetaObject *senderMetaObject)
 {
     if (!sender || !receiver || !slotObj || !senderMetaObject) {
-        qWarning("QObject::connect: invalid null parameter");
+        const char *senderString = sender ? sender->metaObject()->className()
+                                          : senderMetaObject ? senderMetaObject->className()
+                                          : "Unknown";
+        const char *receiverString = receiver ? receiver->metaObject()->className()
+                                              : "Unknown";
+        qWarning("QObject::connect(%s, %s): invalid null parameter", senderString, receiverString);
         if (slotObj)
             slotObj->destroyIfLastRef();
         return QMetaObject::Connection();