diff --git a/m4/ac_have_attribute.m4 b/m4/ac_have_attribute.m4
new file mode 100644
index 0000000..19f4021
--- /dev/null
+++ b/m4/ac_have_attribute.m4
@@ -0,0 +1,16 @@
+AC_DEFUN([AX_C___ATTRIBUTE__], [
+  AC_MSG_CHECKING(for __attribute__)
+  AC_CACHE_VAL(ac_cv___attribute__, [
+    AC_TRY_COMPILE(
+      [#include <stdlib.h>
+       static void foo(void) __attribute__ ((unused));
+       void foo(void) { exit(1); }],
+      [],
+      ac_cv___attribute__=yes,
+      ac_cv___attribute__=no
+    )])
+  if test "$ac_cv___attribute__" = "yes"; then
+    AC_DEFINE(HAVE___ATTRIBUTE__, 1, [define if your compiler has __attribute__])
+  fi
+  AC_MSG_RESULT($ac_cv___attribute__)
+])