diff --git a/qse/include/qse/si/App.hpp b/qse/include/qse/si/App.hpp
index dbc385bd..ed254625 100644
--- a/qse/include/qse/si/App.hpp
+++ b/qse/include/qse/si/App.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_APP_H_
-#define _QSE_SI_APP_H_
+#ifndef _QSE_SI_APP_HPP_
+#define _QSE_SI_APP_HPP_
 
 #include <qse/Types.hpp>
 #include <qse/Uncopyable.hpp>
@@ -59,6 +59,7 @@ class App: public Uncopyable, public Types, public Mmged, public Named<32>
 {
 public:
 	typedef QSE::Bitset<QSE_NSIGS> SignalSet;
+	typedef long int child_pid_t;
 
 	enum SignalState
 	{
@@ -220,7 +221,7 @@ private:
 	};
 
 	_SigLink _sig[QSE_NSIGS]; 
-	long int _guarded_child_pid;
+	child_pid_t _guarded_child_pid;
 
 	qse_cmgr_t* _cmgr;
 	struct log_t
@@ -245,6 +246,15 @@ private:
 	static void handle_signal (int sig) QSE_CPP_NOEXCEPT;
 
 	static int put_char_to_log_buf (qse_char_t c, void* ctx) QSE_CPP_NOEXCEPT;
+
+protected:
+	enum guarded_child_state_t
+	{
+		GUARDED_CHILD_STARTED,
+		GUARDED_CHILD_EXITED
+	};
+
+	void on_guarded_child (child_pid_t pid, guarded_child_state_t state, int status) QSE_CPP_NOEXCEPT {};
 };
 
 /////////////////////////////////
diff --git a/qse/include/qse/si/Condition.hpp b/qse/include/qse/si/Condition.hpp
index 8cce78a4..1aa2b8a7 100644
--- a/qse/include/qse/si/Condition.hpp
+++ b/qse/include/qse/si/Condition.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_CONDITION_CLASS_
-#define _QSE_SI_CONDITION_CLASS_
+#ifndef _QSE_SI_CONDITION_HPP_
+#define _QSE_SI_CONDITION_HPP_
 
 #include <qse/si/cnd.h>
 #include <qse/si/Mutex.hpp>
diff --git a/qse/include/qse/si/Mutex.hpp b/qse/include/qse/si/Mutex.hpp
index 8602312a..808800b6 100644
--- a/qse/include/qse/si/Mutex.hpp
+++ b/qse/include/qse/si/Mutex.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_MUTEX_CLASS_
-#define _QSE_SI_MUTEX_CLASS_
+#ifndef _QSE_SI_MUTEX_HPP_
+#define _QSE_SI_MUTEX_HPP_
 
 #include <qse/Types.hpp>
 #include <qse/Uncopyable.hpp>
diff --git a/qse/include/qse/si/Path.hpp b/qse/include/qse/si/Path.hpp
index c56edfcd..1d0d0f4e 100644
--- a/qse/include/qse/si/Path.hpp
+++ b/qse/include/qse/si/Path.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_PATH_CLASS_
-#define _QSE_SI_PATH_CLASS_
+#ifndef _QSE_SI_PATH_HPP_
+#define _QSE_SI_PATH_HPP_
 
 #include <qse/Types.hpp>
 #include <qse/cmn/Mmged.hpp>
diff --git a/qse/include/qse/si/SpinLock.hpp b/qse/include/qse/si/SpinLock.hpp
index 0568e76b..53fc8838 100644
--- a/qse/include/qse/si/SpinLock.hpp
+++ b/qse/include/qse/si/SpinLock.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_SPINLOCK_CLASS_
-#define _QSE_SI_SPINLOCK_CLASS_
+#ifndef _QSE_SI_SPINLOCK_HPP_
+#define _QSE_SI_SPINLOCK_HPP_
 
 #include <qse/Types.hpp>
 #include <qse/Uncopyable.hpp>
diff --git a/qse/include/qse/si/TcpServer.hpp b/qse/include/qse/si/TcpServer.hpp
index 7b01c1eb..c247e340 100644
--- a/qse/include/qse/si/TcpServer.hpp
+++ b/qse/include/qse/si/TcpServer.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_TCPSERVER_CLASS_
-#define _QSE_SI_TCPSERVER_CLASS_
+#ifndef _QSE_SI_TCPSERVER_HPP_
+#define _QSE_SI_TCPSERVER_HPP_
 
 #include <qse/si/Socket.hpp>
 #include <qse/si/SocketAddress.hpp>
diff --git a/qse/include/qse/si/Thread.hpp b/qse/include/qse/si/Thread.hpp
index 4fa64816..76a742ac 100644
--- a/qse/include/qse/si/Thread.hpp
+++ b/qse/include/qse/si/Thread.hpp
@@ -24,8 +24,8 @@
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _QSE_SI_THREAD_CLASS_
-#define _QSE_SI_THREAD_CLASS_
+#ifndef _QSE_SI_THREAD_HPP_
+#define _QSE_SI_THREAD_HPP_
 
 #include <qse/si/thr.h>
 #include <qse/si/os.h>
diff --git a/qse/lib/si/App.cpp b/qse/lib/si/App.cpp
index 12d72ed3..7a0acf4b 100644
--- a/qse/lib/si/App.cpp
+++ b/qse/lib/si/App.cpp
@@ -543,6 +543,7 @@ int App::guardProcess (const SignalSet& signals, bool _guard, qse_mtime_t guard_
 		// the guardian(parent) process
 		// ===============================================
 		this->_guarded_child_pid = pid;
+		this->on_guarded_child (pid, GUARDED_CHILD_STARTED, 0);
 
 		int status;
 		while (::waitpid(pid, &status, 0) != pid) 
@@ -555,6 +556,7 @@ int App::guardProcess (const SignalSet& signals, bool _guard, qse_mtime_t guard_
 			// ------------------------------------------------------
 		}
 
+		this->on_guarded_child (pid, GUARDED_CHILD_EXITED, status);
 		if (WIFEXITED(status))
 		{
 			if (WEXITSTATUS(status) == 0)