QSignalSpy: fix data race between wait() and emit from another thread

Detected by TSAN in tst_QThread::terminateAndPrematureDestruction()
but better have a dedicated unittest, with values emitted by the signal
and recorded in the spy.

Pick-to: 6.7 6.6 6.5
Change-Id: I141d47b0ea0b63188f8a4f9d056f72df3457bda5
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 31 insertions, 1 deletions

diff --git a/tests/auto/testlib/qsignalspy/tst_qsignalspy.cpp b/tests/auto/testlib/qsignalspy/tst_qsignalspy.cpp
index 40dd9b94de..847986a673 100644
--- a/tests/auto/testlib/qsignalspy/tst_qsignalspy.cpp
+++ b/tests/auto/testlib/qsignalspy/tst_qsignalspy.cpp
@@ -6,9 +6,11 @@
 #include <QSignalSpy>
 #include <QTimer>
 
-
 #include <qdatetime.h>
 
+using namespace std::chrono_literals;
+using namespace Qt::StringLiterals;
+
 class tst_QSignalSpy : public QObject
 {
     Q_OBJECT
@@ -48,6 +50,8 @@ private slots:
 
     void spyOnMetaMethod_invalid();
     void spyOnMetaMethod_invalid_data();
+
+    void signalSpyDoesNotRaceOnCrossThreadSignal();
 };
 
 struct CustomType {};
@@ -485,5 +489,31 @@ void tst_QSignalSpy::spyOnMetaMethod_invalid_data()
         << QObject::staticMetaObject.method(QObject::staticMetaObject.indexOfMethod("deleteLater()"));
 }
 
+class EmitSignal_Thread : public QThread
+{
+    Q_OBJECT
+public:
+    void run() override
+    {
+        emit valueChanged(42, u"is the answer"_s);
+    }
+
+Q_SIGNALS:
+    void valueChanged(int value, const QString &str);
+};
+
+void tst_QSignalSpy::signalSpyDoesNotRaceOnCrossThreadSignal()
+{
+    EmitSignal_Thread thread;
+    QSignalSpy valueChangedSpy(&thread, &EmitSignal_Thread::valueChanged);
+    QVERIFY(valueChangedSpy.isValid());
+
+    thread.start();
+    QVERIFY(valueChangedSpy.wait(5s));
+    QCOMPARE(valueChangedSpy[0][0].toInt(), 42);
+    QCOMPARE(valueChangedSpy[0][1].toString(), u"is the answer"_s);
+    QVERIFY(thread.wait(5s));
+}
+
 QTEST_MAIN(tst_QSignalSpy)
 #include "tst_qsignalspy.moc"