Index: flang/include/flang/Common/idioms.h
===================================================================
--- flang/include/flang/Common/idioms.h
+++ flang/include/flang/Common/idioms.h
@@ -98,9 +98,7 @@
   } \
   template <typename A> constexpr bool T{class_trait_ns_##T::trait_value<A>()};
 
-#if !defined ATTRIBUTE_UNUSED && (__clang__ || __GNUC__)
-#define ATTRIBUTE_UNUSED __attribute__((unused))
-#endif
+#define ATTRIBUTE_UNUSED [[maybe_unused]]
 
 // Define enum class NAME with the given enumerators, a static
 // function EnumToString() that maps enumerators to std::string,