diff --git a/configure.ac b/configure.ac
index 40b8d52..bdc92a3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3,3 +3,22 @@ AC_INIT([r2],[1.4],[yoanlin93@gmail.com],[r2],[http://github.com/c9s/r2])
 # AC_CONFIG_SRCDIR(Front/mona.cpp)
 # AM_INIT_AUTOMAKE()
 AC_CONFIG_HEADERS([config.h])
+
+CFLAGS=$CXXFLAGS
+AC_SUBST(CFLAGS)
+
+AC_HEADER_STDC
+
+AC_CHECK_HEADERS(stdlib.h string.h sys/time.h unistd.h
+                 ,,AC_MSG_ERROR(required header file not found))
+
+dnl ========== checks for typedefs, structures, and compiler characteristics ==========
+
+AC_C_CONST
+AC_C_INLINE
+AC_TYPE_SIZE_T
+
+AC_FUNC_MALLOC
+AC_FUNC_MEMCMP
+AC_FUNC_MMAP
+AC_OUTPUT