CTF: Fix plugin cleanup

Handle cleanup of the CTF plugin correctly. The cleanup causes recursive
trace event so the plugin needs to handle this.

Change-Id: Id6f4c6efe95e51332a8be97fecdf7886ba173e43
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
Reviewed-by: Hatem ElKharashy <hatem.elkharashy@qt.io>
(cherry picked from commit b652d9753bb474b3bc6c881dcb4b40a5a01ddcff)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tracing/qctflib.cpp

@@ -42,6 +42,12 @@ QCtfLib *QCtfLibImpl::instance()
     return s_instance;
 }
 
+void QCtfLibImpl::cleanup()
+{
+    if (s_instance)
+        delete s_instance;
+}
+
 QCtfLibImpl::QCtfLibImpl()
 {
     QString location = QString::fromUtf8(qgetenv("QTRACE_LOCATION"));

src/corelib/tracing/qctflib_p.h

@@ -80,6 +80,7 @@ public:
     int eventId();
 
     static QCtfLib *instance();
+    static void cleanup();
 private:
     static QCtfLibImpl *s_instance;
     QHash<QString, QCtfTracePointPrivate *> m_eventPrivs;

src/corelib/tracing/qctfplugin.cpp

@@ -19,24 +19,38 @@ public:
     {
 
     }
-    ~QCtfTracePlugin() = default;
+    ~QCtfTracePlugin()
+    {
+        m_cleanup = true;
+        QCtfLibImpl::cleanup();
+    }
 
     bool tracepointEnabled(const QCtfTracePointEvent &point) override
     {
+        if (m_cleanup)
+            return false;
         return QCtfLibImpl::instance()->tracepointEnabled(point);
     }
     void doTracepoint(const QCtfTracePointEvent &point, const QByteArray &arr) override
     {
+        if (m_cleanup)
+            return;
         QCtfLibImpl::instance()->doTracepoint(point, arr);
     }
     bool sessionEnabled() override
     {
+        if (m_cleanup)
+            return false;
         return QCtfLibImpl::instance()->sessionEnabled();
     }
     QCtfTracePointPrivate *initializeTracepoint(const QCtfTracePointEvent &point) override
     {
+        if (m_cleanup)
+            return nullptr;
         return QCtfLibImpl::instance()->initializeTracepoint(point);
     }
+private:
+    bool m_cleanup = false;
 };
 
 #include "qctfplugin.moc"