diff --git a/ChangeLog b/ChangeLog
index 53ece3ab0d..b445948038 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Oct 26 09:13:34 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (rb_cv_gcc_atomic_builtins): check for atomic
+	  builtins, all are not available in Apple derivative gcc.
+
 Tue Oct 26 00:29:26 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* Makefile.in (pkgconfig-data): create pkg-config metadata file.
diff --git a/configure.in b/configure.in
index 073da9355b..5dc59396a2 100644
--- a/configure.in
+++ b/configure.in
@@ -775,6 +775,19 @@ if test "$GCC" = yes; then
 	AC_DEFINE_UNQUOTED([RUBY_ALIAS_FUNCTION_VOID(prot, name, args)],
 			   [RUBY_ALIAS_FUNCTION_TYPE(void, prot, name, args)])
     fi
+    AC_CACHE_CHECK([for atomic builtins], [rb_cv_gcc_atomic_builtins], [
+	AC_TRY_LINK([unsigned char atomic_var;],
+		    [
+			__sync_lock_test_and_set(&atomic_var, 0);
+			__sync_lock_test_and_set(&atomic_var, 1);
+			__sync_fetch_and_add(&atomic_var, 1);
+			__sync_fetch_and_sub(&atomic_var, 1);
+		    ],
+		    [rb_cv_gcc_atomic_builtins=yes],
+		    [rb_cv_gcc_atomic_builtins=no])])
+    if test "$rb_cv_gcc_atomic_builtins" = yes; then
+	AC_DEFINE(HAVE_GCC_ATOMIC_BUILTINS)
+    fi
 fi
 
 AC_CACHE_CHECK(for exported function attribute, rb_cv_func_exported, [
diff --git a/signal.c b/signal.c
index 0c0675e839..9b63046ec0 100644
--- a/signal.c
+++ b/signal.c
@@ -25,7 +25,7 @@ typedef LONG rb_atomic_t;
 # define ATOMIC_INC(var) InterlockedIncrement(&(var))
 # define ATOMIC_DEC(var) InterlockedDecrement(&(var))
 
-#elif __GNUC__ >= 4
+#elif defined HAVE_GCC_ATOMIC_BUILTINS
 /* @shyouhei hack to support atomic operations in case of gcc. Gcc
  * has its own pseudo-insns to support them.  See info, or
  * http://gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html */