diff --git a/qse/include/qse/cmn/Bitset.hpp b/qse/include/qse/cmn/Bitset.hpp
index 6cf4ac13..4cb656c6 100644
--- a/qse/include/qse/cmn/Bitset.hpp
+++ b/qse/include/qse/cmn/Bitset.hpp
@@ -32,15 +32,97 @@
 QSE_BEGIN_NAMESPACE(QSE)
 /////////////////////////////////
 
-template <qse_size_t NB>
+template <int NB>
 class Bitset
 {
 public:
-	static const int NW = (NB - 1) / (QSE_SIZEOF(qse_size_t) * 8) + 1;
+	typedef qse_size_t word_type_t;
+
+	static const int NW = (NB - 1) / (QSE_SIZEOF(word_type_t) * 8) + 1;
+
+	Bitset() { this->empty (); }
+
+	bool operator== (const Bitset<NB>& bs) const
+	{
+		// [NOTE] 
+		//   if you happen to have different garbage at the unused part
+		//   of the last word, this equality check may return a wrong result.
+		for (int i = 0; i < NW; i++)
+		{
+			if (this->_w[i] != bs._w[i]) return false;
+		}
+		return true;
+	}
+
+	bool operator!= (const Bitset<NB>& bs) const
+	{
+		return !this->operator==(bs);
+	}
+
+	int get_word_index (int bit) const
+	{
+		return bit / (QSE_SIZEOF(word_type_t) * 8);
+	}
+
+	word_type_t get_word_mask (int bit) const
+	{
+		return ((word_type_t)1) << (bit % (QSE_SIZEOF(word_type_t) * 8));
+	}
+
+	void set (int bit)
+	{
+		this->_w[this->get_word_index(bit)] |= this->get_word_mask(bit);
+	}
+
+	void unset (int bit)
+	{
+		this->_w[this->get_word_index(bit)] &= ~this->get_word_mask(bit);
+	}
+
+	void set (const Bitset<NB>& bs)
+	{
+		// mask on all bits set in bs.
+		for (int i = 0; i < NW; i++)
+		{
+			this->_w[i] |= bs._w[i];
+		}
+	}
+
+	void unset (const Bitset<NB>& bs)
+	{
+		// mask off all bits set in bs.
+		for (int i = 0; i < NW; i++)
+		{
+			this->_w[i] &= ~bs._w[i];
+		}
+	}
+
+	bool isSet (int bit) const
+	{
+		return (this->_w[this->get_word_index(bit)] & this->get_word_mask(bit));
+	}
+
+	bool isEmpty () const
+	{
+		for (int i = 0; i < NW; i++) 
+		{
+			if (this->_w[i]) return false;
+		}
+		return true;
+	}
+
+	void empty ()
+	{
+		for (int i = 0; i < NW; i++) this->_w[i] = 0;
+	}
+
+	void fill ()
+	{
+		for (int i = 0; i < NW; i++) this->_w[i] = ~(word_type_t)0;
+	}
 
-	
 protected:
-	qse_size_t _w[NW];
+	word_type_t _w[NW];
 };
 
 /////////////////////////////////
diff --git a/qse/include/qse/si/App.hpp b/qse/include/qse/si/App.hpp
index cda3be54..f041b4a4 100644
--- a/qse/include/qse/si/App.hpp
+++ b/qse/include/qse/si/App.hpp
@@ -30,6 +30,7 @@
 #include <qse/Types.hpp>
 #include <qse/Uncopyable.hpp>
 #include <qse/cmn/Mmged.hpp>
+#include <qse/cmn/Bitset.hpp>
 
 /////////////////////////////////
 QSE_BEGIN_NAMESPACE(QSE)
@@ -38,6 +39,8 @@ QSE_BEGIN_NAMESPACE(QSE)
 class App: public Uncopyable, public Types, public Mmged
 {
 public:
+	typedef QSE::Bitset<QSE_NSIGS> Sigset;
+
 	App (Mmgr* mmgr) QSE_CPP_NOEXCEPT;
 	virtual ~App () QSE_CPP_NOEXCEPT;
 
@@ -70,7 +73,7 @@ public:
 	static int setSignalHandler (int sig, SignalHandler sighr);
 	static int unsetSignalHandler (int sig);
 
-	int guardProcess (const qse_mchar_t* proc_name);
+	int guardProcess (const qse_mchar_t* proc_name, const Sigset& signals);
 
 private:
 	App* _prev_app;
diff --git a/qse/lib/si/App.cpp b/qse/lib/si/App.cpp
index ab764657..61a7301e 100644
--- a/qse/lib/si/App.cpp
+++ b/qse/lib/si/App.cpp
@@ -293,7 +293,7 @@ int App::unset_signal_handler_no_mutex(int sig)
 
 void App::on_guard_signal (int sig)
 {
-printf ("relaying %d to %d\n", sig, this->_guarded_child_pid);
+printf ("relaying %d to %d\n", sig, (int)this->_guarded_child_pid);
 	::kill (this->_guarded_child_pid, sig);
 }
 
@@ -437,7 +437,7 @@ void App::unsubscribe_from_all_signals_no_mutex()
 	}
 }
 
-int App::guardProcess (const qse_mchar_t* proc_name, /* TODO: get the list of signals to relay??? */)
+int App::guardProcess (const qse_mchar_t* proc_name, const Sigset& signals)
 {
 	while (1)
 	{
@@ -445,8 +445,8 @@ int App::guardProcess (const qse_mchar_t* proc_name, /* TODO: get the list of si
 		if (pid == -1) return -1;
 		if (pid == 0) break; // child
 
-int _SigLink::State old_sig_states[QSE_NSIGS];
-this->subscribeToAllSignals(true);
+//int _SigLink::State old_sig_states[QSE_NSIGS];
+//this->subscribeToAllSignals(true);
 
 		this->_guarded_child_pid = pid;
 
diff --git a/qse/samples/si/tcpsvr01.cpp b/qse/samples/si/tcpsvr01.cpp
index 1802c2b3..beb34859 100644
--- a/qse/samples/si/tcpsvr01.cpp
+++ b/qse/samples/si/tcpsvr01.cpp
@@ -75,7 +75,13 @@ public:
 
 	int run ()
 	{
-		if (this->guardProcess("myapp") > 0)
+		QSE::App::Sigset signals;
+		signals.set (SIGINT);
+		signals.set (SIGHUP);
+		signals.set (SIGTERM);
+		signals.set (SIGUSR1);
+		signals.set (SIGUSR2);
+		if (this->guardProcess("myapp", signals) > 0)
 		{
 qse_printf (QSE_T("Stareting workd\n"));
 			this->server.setThreadStackSize (256000);