Index: m4/ax_check_define.m4
===================================================================
--- m4/ax_check_define.m4	(revision 0)
+++ m4/ax_check_define.m4	(revision 0)
@@ -0,0 +1,55 @@
+dnl @synopsis AC_CHECK_DEFINE([symbol], [ACTION-IF-FOUND], [ACTION-IF-NOT])
+dnl @synopsis AX_CHECK_DEFINE([includes],[symbol], [ACTION-IF-FOUND], [ACTION-IF-NOT])
+dnl
+dnl complements AC_CHECK_FUNC but it does not check for a function but
+dnl for a define to exist. Consider a usage like
+dnl AC_CHECK_DEFINE(__STRICT_ANSI__, CFLAGS="$CFLAGS
+dnl -D_XOPEN_SOURCE=500")
+dnl
+dnl @category Misc
+dnl @author Guido U. Draheim <guidod@gmx.de>
+dnl @version 2006-10-13
+dnl @license GPLWithACException
+
+AC_DEFUN([AC_CHECK_DEFINED],[
+AS_VAR_PUSHDEF([ac_var],[ac_cv_defined_$1])dnl
+AC_CACHE_CHECK([for $1 defined], ac_var,
+AC_TRY_COMPILE(,[
+  #ifdef $1
+  int ok;
+  #else
+  choke me
+  #endif
+],AS_VAR_SET(ac_var, yes),AS_VAR_SET(ac_var, no)))
+AS_IF([test AS_VAR_GET(ac_var) != "no"], [$2], [$3])dnl
+AS_VAR_POPDEF([ac_var])dnl
+])
+
+AC_DEFUN([AX_CHECK_DEFINED],[
+AS_VAR_PUSHDEF([ac_var],[ac_cv_defined_$2])dnl
+AC_CACHE_CHECK([for $1 defined], ac_var,
+AC_TRY_COMPILE($1,[
+  #ifndef $2
+  int ok;
+  #else
+  choke me
+  #endif
+],AS_VAR_SET(ac_var, yes),AS_VAR_SET(ac_var, no)))
+AS_IF([test AS_VAR_GET(ac_var) != "no"], [$3], [$4])dnl
+AS_VAR_POPDEF([ac_var])dnl
+])
+
+AC_DEFUN([AX_CHECK_FUNC],
+[AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$2])dnl
+AC_CACHE_CHECK([for $2], ac_var,
+dnl AC_LANG_FUNC_LINK_TRY
+[AC_LINK_IFELSE([AC_LANG_PROGRAM([$1
+                #undef $2
+                char $2 ();],[
+                char (*f) () = $2;
+                return f != $2; ])],
+                [AS_VAR_SET(ac_var, yes)],
+                [AS_VAR_SET(ac_var, no)])])
+AS_IF([test AS_VAR_GET(ac_var) = yes], [$3], [$4])dnl
+AS_VAR_POPDEF([ac_var])dnl
+])# AC_CHECK_FUNC
Index: configure.ac
===================================================================
--- configure.ac	(revision 6723)
+++ configure.ac	(working copy)
@@ -273,6 +273,9 @@
 dnl ===========================================================
 dnl Checks processor type, for processor-specific stuff
 case $host in
+  i?86-apple-darwin*)
+    AC_CHECK_DEFINED(i386,
+      AC_DEFINE(SCM_TARGET_I386,1,[Define if uses i386 optimizations])) ;;
   i?86-*)
     AC_DEFINE(SCM_TARGET_I386,1,[Define if uses i386 optimizations]) ;;
   alpha*)
Index: acinclude.m4
===================================================================
--- acinclude.m4	(revision 6723)
+++ acinclude.m4	(working copy)
@@ -5,5 +5,6 @@
 dnl Gauche custom macros
 m4_include([m4/gauche.m4])
 m4_include([m4/type_socklen_t.m4])
+m4_include([m4/ax_check_define.m4])
 
 dnl