diff --git a/ChangeLog b/ChangeLog
index ee1c031..d70d354 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2007-02-09  Alexei Sheplyakov  <varg@theor.jinr.ru>
+            Richard B. Kreckel  <kreckel@ginac.de>
+
+	Avoid compiler warning about ignored 'flatten' attribute directive:
+	* m4/cc.m4 (CL_ATTRIBUTE_FLATTEN): New macro...
+	* configure.ac: ...used here...
+	* include/cln/config.h.in: ...defining CL_HAVE_ATTRIBUTE_FLATTEN,...
+	* src/base/cl_maybe_inline.h: ...used to prevent a warning here.
+
 2007-02-07  Richard B. Kreckel  <kreckel@ginac.de>
 
 	* include/cln/integer.h: Enable modifying operators by default.
diff --git a/configure.ac b/configure.ac
index 2c90a92..e5e06de 100644
--- a/configure.ac
+++ b/configure.ac
@@ -147,6 +147,8 @@ CL_RUSAGE
                       dnl DEFS HAVE_SYS_RESOURCE_H, HAVE_GETRUSAGE, HAVE_SYS_TIMES_H
 CL_PERROR
                       dnl DEFS HAVE_PERROR_DECL
+CL_ATTRIBUTE_FLATTEN
+                      dnl DEFS CL_HAVE_ATTRIBUTE_FLATTEN
 dnl
 dnl           checks for compiler characteristics
 dnl
diff --git a/include/cln/config.h.in b/include/cln/config.h.in
index ec00f5e..b1b1ebd 100644
--- a/include/cln/config.h.in
+++ b/include/cln/config.h.in
@@ -148,6 +148,10 @@
 #ifndef CL_GLOBAL_CONSTRUCTOR_SUFFIX_NOPIC
 #undef CL_GLOBAL_CONSTRUCTOR_SUFFIX_NOPIC
 #endif
+/* Define if the compiler knows about __attribute__((flatten)). */
+#ifndef CL_HAVE_ATTRIBUTE_FLATTEN
+#undef CL_HAVE_ATTRIBUTE_FLATTEN
+#endif
 
 /* CL_CHAR_UNSIGNED */
 #ifndef __CHAR_UNSIGNED__
diff --git a/m4/cc.m4 b/m4/cc.m4
index ec6c5e8..0925662 100644
--- a/m4/cc.m4
+++ b/m4/cc.m4
@@ -67,3 +67,24 @@ EOF
   fi
   AC_SUBST(ASMFLAGS)
 ])
+
+
+dnl Checks whether the compiler supports __attribute__((flatten)).
+AC_DEFUN([CL_ATTRIBUTE_FLATTEN],[
+AC_REQUIRE([AC_PROG_CXX])
+AC_CACHE_CHECK([whether the compiler supports __attribute__((flatten))], cl_cv_have_attr_flatten, [dnl
+  cat > conftest.cc <<EOF
+void f() __attribute__((flatten));
+EOF
+AC_TRY_COMMAND(${CXX-g++} $CXXFLAGS -c conftest.cc >/dev/null 2>conftest.out)
+if grep -i "warning" conftest.out > /dev/null; then
+  cl_cv_have_attr_flatten=no
+else
+  cl_cv_have_attr_flatten=yes
+fi
+rm -f conftest*
+])
+if test $cl_cv_have_attr_flatten = yes; then
+  AC_DEFINE(CL_HAVE_ATTRIBUTE_FLATTEN)
+fi
+])
diff --git a/src/base/cl_maybe_inline.h b/src/base/cl_maybe_inline.h
index 316cc5b..4f7a982 100644
--- a/src/base/cl_maybe_inline.h
+++ b/src/base/cl_maybe_inline.h
@@ -3,6 +3,8 @@
 #ifndef _CL_MAYBE_INLINE_H
 #define _CL_MAYBE_INLINE_H
 
+#include "cln/config.h"
+
 /*
  * Selectively inline a function in *some* translation units.
  *
@@ -100,7 +102,7 @@
  *    a function.
  * 2. It's ignored if the optimization is switched off.
  */
-#ifdef __GNUC__
+#if defined(__GNUC__) && defined(CL_ATTRIBUTE_FLATTEN)
 #define CL_FLATTEN __attribute__((flatten))
 #else
 #define CL_FLATTEN