Attempt to unwedge tst_QThread::wait3_slowDestructor()

When the test failed, it never released the blocking slot, so the
tested thread remained blocked indefinitely. Blacklisting doesn't
rescue that: the test run gets killed by Coin's watchdog.

Use a QScopeGuard() to release the clocked slot on failure.
replacing the release that was happening only on success.

As drive-by clean-up, smarten up the code a little and remove an
unused enum.

Pick-to: 6.2 6.1 5.15
Change-Id: Ie035dafe6e4b1d82aea5de38ceb31c0f7fcf81d7
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

1 files changed, 15 insertions, 13 deletions

diff --git a/tests/auto/corelib/thread/qthread/tst_qthread.cpp b/tests/auto/corelib/thread/qthread/tst_qthread.cpp
index 29c72b9bf9..0631070d22 100644
--- a/tests/auto/corelib/thread/qthread/tst_qthread.cpp
+++ b/tests/auto/corelib/thread/qthread/tst_qthread.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the test suite of the Qt Toolkit.
@@ -40,6 +40,7 @@
 #include <qwaitcondition.h>
 #include <qdebug.h>
 #include <qmetaobject.h>
+#include <qscopeguard.h>
 
 #ifdef Q_OS_UNIX
 #include <pthread.h>
@@ -1086,8 +1087,8 @@ void tst_QThread::wait2()
              qPrintable(msgElapsed(elapsed)));
 }
 
-
-class SlowSlotObject : public QObject {
+class SlowSlotObject : public QObject
+{
     Q_OBJECT
 public:
     QMutex mutex;
@@ -1103,22 +1104,23 @@ void tst_QThread::wait3_slowDestructor()
 {
     SlowSlotObject slow;
     QThread thread;
-    QObject::connect(&thread, SIGNAL(finished()), &slow, SLOT(slowSlot()), Qt::DirectConnection);
-
-    enum { WaitTime = 1800 };
+    QObject::connect(&thread, &QThread::finished,
+                     &slow, &SlowSlotObject::slowSlot, Qt::DirectConnection);
     QElapsedTimer timer;
 
     thread.start();
     thread.quit();
-    //the quit function will cause the thread to finish and enter the slowSlot that is blocking
+    // Calling quit() will cause the thread to finish and enter the blocking slowSlot().
 
     timer.start();
-    QVERIFY(!thread.wait(Waiting_Thread::WaitTime));
-    qint64 elapsed = timer.elapsed();
-    QVERIFY2(elapsed >= Waiting_Thread::WaitTime - 1, qPrintable(QString::fromLatin1("elapsed: %1").arg(elapsed)));
-
-    slow.cond.wakeOne();
-    //now the thread should finish quickly
+    {
+        // Ensure thread finishes quickly after the checks - regardless of success:
+        QScopeGuard wakeSlow([&slow]() -> void { slow.cond.wakeOne(); });
+        QVERIFY(!thread.wait(Waiting_Thread::WaitTime));
+        const qint64 elapsed = timer.elapsed();
+        QVERIFY2(elapsed >= Waiting_Thread::WaitTime - 1,
+                 qPrintable(QString::fromLatin1("elapsed: %1").arg(elapsed)));
+    }
     QVERIFY(thread.wait(one_minute));
 }