Make error checking in QSignalSpy consistent

QSignalSpy's constructor failed gracefully for some problems with the
parameters, but not for null parameters, for which there was only a
Q_ASSERT.  This commit makes the handling of null parameters consistent
with the handling of other errors -- output a meaningful error message
with qWarning() and return, so that isValid() will subsequently return
false.

Change-Id: I7f5677a4c10185e30403ce3e12a022de8c13bc1c
Task-number: QTBUG-14283
Reviewed-by: Rohan McGovern

1 files changed, 9 insertions, 2 deletions

diff --git a/src/testlib/qsignalspy.h b/src/testlib/qsignalspy.h
index b0b48c5025..fce5aad56a 100644
--- a/src/testlib/qsignalspy.h
+++ b/src/testlib/qsignalspy.h
@@ -68,8 +68,15 @@ public:
 #else
         static const int memberOffset = QObject::staticMetaObject.methodCount();
 #endif
-        Q_ASSERT(obj);
-        Q_ASSERT(aSignal);
+        if (!obj) {
+            qWarning("QSignalSpy: Cannot spy on a null object");
+            return;
+        }
+
+        if (!aSignal) {
+            qWarning("QSignalSpy: Null signal name is not valid");
+            return;
+        }
 
         if (((aSignal[0] - '0') & 0x03) != QSIGNAL_CODE) {
             qWarning("QSignalSpy: Not a valid signal, use the SIGNAL macro");