QTestLib: fix crashes when using qDebug()s from threads with -junitxml

Other test loggers just output things immediately, but the junit test
logger appends messages to a vector, so this needs to be
mutex-protected.

In case of qDebug()s from long-running threads, we also need
to protect creation/destruction of systemOutputElement and
systemErrorElement -- and in case of qFatal(), currentTestCase.

Pick-to: 6.5
Change-Id: If35055fc232276a778951ebbfeaccd185b04f46b
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Jason McDonald <macadder1@gmail.com>
(cherry picked from commit b4d6892ba5a745c1836daf34c850d13ef61e7ae0)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 120a987544dc4d3824b02016dc837850b1fc8aef)

src/testlib/qjunittestlogger.cpp

@@ -130,6 +130,8 @@ void QJUnitTestLogger::enterTestFunction(const char *function)
 
 void QJUnitTestLogger::enterTestCase(const char *name)
 {
+    {
+        QMutexLocker locker(&mutex);
         currentTestCase = new QTestElement(QTest::LET_TestCase);
         currentTestCase->addAttribute(QTest::AI_Name, name);
         currentTestCase->addAttribute(QTest::AI_Classname, QTestResult::currentTestObjectName());
@@ -138,6 +140,7 @@ void QJUnitTestLogger::enterTestCase(const char *name)
         Q_ASSERT(!systemOutputElement && !systemErrorElement);
         systemOutputElement = new QTestElement(QTest::LET_SystemOutput);
         systemErrorElement = new QTestElement(QTest::LET_SystemError);
+    }
 
     // The element will be deleted when the suite is deleted
 
@@ -174,6 +177,7 @@ void QJUnitTestLogger::leaveTestFunction()
 
 void QJUnitTestLogger::leaveTestCase()
 {
+    QMutexLocker locker(&mutex);
     currentTestCase->addAttribute(QTest::AI_Time,
         toSecondsFormat(elapsedTestCaseSeconds() * 1000).constData());
 
@@ -257,6 +261,7 @@ void QJUnitTestLogger::addMessage(MessageTypes type, const QString &message, con
     Q_UNUSED(file);
     Q_UNUSED(line);
 
+    QMutexLocker locker(&mutex);
     if (type == QFatal) {
         addFailure(QTest::LET_Error, "qfatal", message);
         return;

src/testlib/qjunittestlogger_p.h

@@ -19,6 +19,7 @@
 
 #include <QtTest/private/qabstracttestlogger_p.h>
 #include <QtTest/private/qtestelementattribute_p.h>
+#include <QtCore/qmutex.h>
 
 #include <vector>
 
@@ -61,6 +62,9 @@ class QJUnitTestLogger : public QAbstractTestLogger
         QTestElement *systemOutputElement = nullptr;
         QTestElement *systemErrorElement = nullptr;
         QTestJUnitStreamer *logFormatter = nullptr;
+        // protects currentTestCase, systemOutputElement and systemErrorElement
+        // in case of qDebug()/qWarning() etc. from threads
+        QMutex mutex;
 
         int testCounter = 0;
         int failureCounter = 0;