diff --git a/qse/include/qse/si/App.hpp b/qse/include/qse/si/App.hpp
index 8fc09a7f..aa2b0efe 100644
--- a/qse/include/qse/si/App.hpp
+++ b/qse/include/qse/si/App.hpp
@@ -40,17 +40,17 @@
 QSE_BEGIN_NAMESPACE(QSE)
 /////////////////////////////////
 
-#define QSE_APP_LOG_ENABLED(app, mask) (((app)->getLogMask() & mask) == mask)
-#define QSE_APP_LOG0(app, mask, fmt)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt); } while(0)
-#define QSE_APP_LOG1(app, mask, fmt, a1)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1); } while(0)
-#define QSE_APP_LOG2(app, mask, fmt, a1, a2)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2); } while(0)
-#define QSE_APP_LOG3(app, mask, fmt, a1, a2, a3)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3); } while(0)
-#define QSE_APP_LOG4(app, mask, fmt, a1, a2, a3, a4)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3, a4); } while(0)
-#define QSE_APP_LOG5(app, mask, fmt, a1, a2, a3, a4, a5)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3, a4, a5); } while(0)
-#define QSE_APP_LOG6(app, mask, fmt, a1, a2, a3, a4, a5, a6)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3, a4, a5, a6); } while(0)
-#define QSE_APP_LOG7(app, mask, fmt, a1, a2, a3, a4, a5, a6, a7)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3, a4, a5, a6, a7); } while(0)
-#define QSE_APP_LOG8(app, mask, fmt, a1, a2, a3, a4, a5, a6, a7, a8)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3, a4, a5, a6, a7, a8); } while(0)
-#define QSE_APP_LOG9(app, mask, fmt, a1, a2, a3, a4, a5, a6, a7, a8, a9)  do { if (QSE_APP_LOG_ENABLED(app, mask)) app->logfmt(mask, fmt, a1, a2, a3, a4, a5, a6, a7, a8, a9); } while(0)
+#define QSE_APP_LOG_ENABLED(app, mask) (((app)->getLogMask() & (mask)) == (mask))
+#define QSE_APP_LOG0(app, mask, fmt)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt); } while(0)
+#define QSE_APP_LOG1(app, mask, fmt, a1)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1); } while(0)
+#define QSE_APP_LOG2(app, mask, fmt, a1, a2)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2); } while(0)
+#define QSE_APP_LOG3(app, mask, fmt, a1, a2, a3)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3); } while(0)
+#define QSE_APP_LOG4(app, mask, fmt, a1, a2, a3, a4)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3, a4); } while(0)
+#define QSE_APP_LOG5(app, mask, fmt, a1, a2, a3, a4, a5)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3, a4, a5); } while(0)
+#define QSE_APP_LOG6(app, mask, fmt, a1, a2, a3, a4, a5, a6)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3, a4, a5, a6); } while(0)
+#define QSE_APP_LOG7(app, mask, fmt, a1, a2, a3, a4, a5, a6, a7)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3, a4, a5, a6, a7); } while(0)
+#define QSE_APP_LOG8(app, mask, fmt, a1, a2, a3, a4, a5, a6, a7, a8)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3, a4, a5, a6, a7, a8); } while(0)
+#define QSE_APP_LOG9(app, mask, fmt, a1, a2, a3, a4, a5, a6, a7, a8, a9)  do { if (QSE_APP_LOG_ENABLED(app, (mask))) app->logfmt((mask), fmt, a1, a2, a3, a4, a5, a6, a7, a8, a9); } while(0)
 
 class App: public Uncopyable, public Types, public Mmged
 {
@@ -193,11 +193,8 @@ public:
 	void logfmtv (int mask, const qse_char_t* fmt, va_list ap);
 
 protected:
-	virtual void log_write (int mask, const qse_char_t* msg, qse_size_t len)
-	{
-		// do nothing 
-		// subclasses should override this if needed.
-	}
+	// subclasses may override this if the defaulg logging output is not desired.
+	virtual void log_write (int mask, const qse_char_t* msg, qse_size_t len);
 
 private:
 	App* _prev_app;
diff --git a/qse/lib/si/App.cpp b/qse/lib/si/App.cpp
index c1754dd0..62a6a289 100644
--- a/qse/lib/si/App.cpp
+++ b/qse/lib/si/App.cpp
@@ -549,13 +549,13 @@ int App::put_char_to_log_buf (qse_char_t c, void* ctx)
 static int wcs_to_mbs (const qse_wchar_t* wcs, qse_size_t* wcslen, qse_mchar_t* mbs, qse_size_t* mbslen, void* ctx)
 {
 	App* app = (App*)ctx;
-	return qse_wcsntombsnwithcmgr (wcs, wcslen, mbs, mbslen, app->getCmgr());
+	return qse_wcsntombsnwithcmgr(wcs, wcslen, mbs, mbslen, app->getCmgr());
 }
 
 static int mbs_to_wcs (const qse_mchar_t* mbs, qse_size_t* mbslen, qse_wchar_t* wcs, qse_size_t* wcslen, void* ctx)
 {
 	App* app = (App*)ctx;
-	return qse_mbsntowcsnwithcmgr (mbs, mbslen, wcs, wcslen, app->getCmgr());
+	return qse_mbsntowcsnwithcmgr(mbs, mbslen, wcs, wcslen, app->getCmgr());
 }
 
 void App::logfmtv (int mask, const qse_char_t* fmt, va_list ap)
@@ -591,6 +591,12 @@ void App::logfmtv (int mask, const qse_char_t* fmt, va_list ap)
 	/*if (this->threaded)*/ this->_log.mtx.unlock ();
 }
 
+// default log message output implementation
+void App::log_write (int mask, const qse_char_t* msg, qse_size_t len)
+{
+}
+
+
 /////////////////////////////////
 QSE_END_NAMESPACE(QSE)
 /////////////////////////////////