Fix Qt::QueuedConnection when signal has a return value

For queued connections, the args[0] is set to null as it make no sens to
forward the return value to the signal.
So we need to check in the operator, that the pointer is not null.
(container.data is args[0])

Change-Id: I80bde66f1ec19de0f4962c80e5b2797d2819075c
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

2 files changed, 61 insertions, 2 deletions

diff --git a/src/corelib/kernel/qobject_impl.h b/src/corelib/kernel/qobject_impl.h
index 9918b1f1c2..d34b81ceaf 100644
--- a/src/corelib/kernel/qobject_impl.h
+++ b/src/corelib/kernel/qobject_impl.h
@@ -96,12 +96,14 @@ namespace QtPrivate {
     };
     template<typename T, typename U>
     void operator,(const T &value, const ApplyReturnValue<U> &container) {
-        *reinterpret_cast<U*>(container.data) = value;
+        if (container.data)
+            *reinterpret_cast<U*>(container.data) = value;
     }
 #ifdef Q_COMPILER_RVALUE_REFS
     template<typename T, typename U>
     void operator,(T &&value, const ApplyReturnValue<U> &container) {
-        *reinterpret_cast<U*>(container.data) = value;
+        if (container.data)
+            *reinterpret_cast<U*>(container.data) = value;
     }
 #endif
     template<typename T>
diff --git a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
index 5e69a14ba8..511eb73d9d 100644
--- a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
+++ b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
@@ -4978,6 +4978,29 @@ void tst_QObject::returnValue()
         QVERIFY(connect(&r, &ReturnValue::returnCustomType, &receiver, &ReturnValue::returnVoidSlot, type));
         QCOMPARE((emit r.returnCustomType(45)).value(), CustomType().value());
     }
+    if (!isBlockingQueued) {
+        // queued connection should not forward the return value
+        CheckInstanceCount checker;
+        ReturnValue r;
+        QVERIFY(connect(&r, &ReturnValue::returnVariant, &receiver, &ReturnValue::returnVariantSlot, Qt::QueuedConnection));
+        QCOMPARE(emit r.returnVariant(45), QVariant());
+        QVERIFY(connect(&r, &ReturnValue::returnString, &receiver, &ReturnValue::returnStringSlot, Qt::QueuedConnection));
+        QCOMPARE(emit r.returnString(45), QString());
+        QVERIFY(connect(&r, &ReturnValue::returnInt, &receiver, &ReturnValue::returnIntSlot, Qt::QueuedConnection));
+        QCOMPARE(emit r.returnInt(45), int());
+        QVERIFY(connect(&r, &ReturnValue::returnCustomType, &receiver, &ReturnValue::returnCustomTypeSlot, Qt::QueuedConnection));
+        QCOMPARE((emit r.returnCustomType(45)).value(), CustomType().value());
+        QCoreApplication::processEvents();
+
+        QVERIFY(connect(&r, &ReturnValue::returnVariant, &receiver, &ReturnValue::returnStringSlot, Qt::QueuedConnection));
+        QCOMPARE(emit r.returnVariant(48), QVariant());
+        QVERIFY(connect(&r, &ReturnValue::returnCustomType, &receiver, &ReturnValue::returnIntSlot, Qt::QueuedConnection));
+        QCOMPARE((emit r.returnCustomType(48)).value(), CustomType().value());
+        QVERIFY(connect(&r, &ReturnValue::returnVoid, &receiver, &ReturnValue::returnCustomTypeSlot, Qt::QueuedConnection));
+        emit r.returnVoid(48);
+        QCoreApplication::processEvents();
+    }
+
     { // connected to many slots
         ReturnValue::VoidFunctor voidFunctor;
         ReturnValue::IntFunctor intFunctor;
@@ -4994,6 +5017,8 @@ void tst_QObject::returnValue()
         QCOMPARE(emit r.returnVariant(45), QVariant(QStringLiteral("hello")));
         QVERIFY(connect(&r, &ReturnValue::returnVariant, intFunctor));
         QCOMPARE(emit r.returnVariant(45), QVariant(45));
+        QVERIFY(connect(&r, &ReturnValue::returnVariant, &receiver, &ReturnValue::return23, Qt::QueuedConnection));
+        QCOMPARE(emit r.returnVariant(45), QVariant(45));
 
         QCOMPARE(emit r.returnInt(45), int());
         QVERIFY(connect(&r, &ReturnValue::returnInt, &receiver, &ReturnValue::returnVoidSlot, type));
@@ -5006,7 +5031,12 @@ void tst_QObject::returnValue()
         QCOMPARE(emit r.returnInt(45), int(23));
         QVERIFY(connect(&r, &ReturnValue::returnInt, intFunctor));
         QCOMPARE(emit r.returnInt(45), int(45));
+        QVERIFY(connect(&r, &ReturnValue::returnInt, &receiver, &ReturnValue::return23, Qt::QueuedConnection));
+        QCOMPARE(emit r.returnInt(45), int(45));
+
+        QCoreApplication::processEvents();
     }
+
     if (isBlockingQueued) {
         thread.quit();
         thread.wait();
@@ -5055,6 +5085,29 @@ void tst_QObject::returnValue2()
         QVERIFY(connect(&r, SIGNAL(returnCustomType(int)), &receiver, SLOT(returnVoidSlot()), type));
         QCOMPARE((emit r.returnCustomType(45)).value(), CustomType().value());
     }
+    if (!isBlockingQueued) {
+        // queued connection should not forward the return value
+        CheckInstanceCount checker;
+        ReturnValue r;
+        QVERIFY(connect(&r, SIGNAL(returnVariant(int)), &receiver, SLOT(returnVariantSlot(int)), Qt::QueuedConnection));
+        QCOMPARE(emit r.returnVariant(45), QVariant());
+        QVERIFY(connect(&r, SIGNAL(returnString(int)), &receiver, SLOT(returnStringSlot(int)), Qt::QueuedConnection));
+        QCOMPARE(emit r.returnString(45), QString());
+        QVERIFY(connect(&r, SIGNAL(returnInt(int)), &receiver, SLOT(returnIntSlot(int)), Qt::QueuedConnection));
+        QCOMPARE(emit r.returnInt(45), int());
+        QVERIFY(connect(&r, SIGNAL(returnCustomType(int)), &receiver, SLOT(returnCustomTypeSlot(int)), Qt::QueuedConnection));
+        QCOMPARE((emit r.returnCustomType(45)).value(), CustomType().value());
+        QCoreApplication::processEvents();
+
+        //Queued conneciton with different return type should be safe
+        QVERIFY(connect(&r, SIGNAL(returnVariant(int)), &receiver, SLOT(returnStringSlot(int)), Qt::QueuedConnection));
+        QCOMPARE(emit r.returnVariant(48), QVariant());
+        QVERIFY(connect(&r, SIGNAL(returnCustomType(int)), &receiver, SLOT(returnIntSlot(int)), Qt::QueuedConnection));
+        QCOMPARE((emit r.returnCustomType(48)).value(), CustomType().value());
+        QVERIFY(connect(&r, SIGNAL(returnVoid(int)), &receiver, SLOT(returnCustomTypeSlot(int)), Qt::QueuedConnection));
+        emit r.returnVoid(48);
+        QCoreApplication::processEvents();
+    }
     { // connected to many slots
         ReturnValue r;
         QVERIFY(connect(&r, SIGNAL(returnInt(int)), &receiver, SLOT(returnIntSlot(int)), type));
@@ -5063,6 +5116,8 @@ void tst_QObject::returnValue2()
         QCOMPARE(emit r.returnInt(45), int(45));
         QVERIFY(connect(&r, SIGNAL(returnInt(int)), &receiver, SLOT(return23()), type));
         QCOMPARE(emit r.returnInt(45), int(23));
+        QVERIFY(connect(&r, SIGNAL(returnInt(int)), &receiver, SLOT(returnIntSlot(int)), Qt::QueuedConnection));
+        QCOMPARE(emit r.returnInt(45), int(23));
 
         QVERIFY(connect(&r, SIGNAL(returnString(int)), &receiver, SLOT(returnStringSlot(int)), type));
         QCOMPARE(emit r.returnString(45), QString(QStringLiteral("45")));
@@ -5070,6 +5125,8 @@ void tst_QObject::returnValue2()
         QCOMPARE(emit r.returnString(45), QString(QStringLiteral("45")));
         QVERIFY(connect(&r, SIGNAL(returnString(int)), &receiver, SLOT(returnHello()), type));
         QCOMPARE(emit r.returnString(45), QString(QStringLiteral("hello")));
+        QVERIFY(connect(&r, SIGNAL(returnString(int)), &receiver, SLOT(returnStringSlot(int)), Qt::QueuedConnection));
+        QCOMPARE(emit r.returnString(45), QString(QStringLiteral("hello")));
     }
     if (isBlockingQueued) {
         thread.quit();