Index: libcxx/include/__locale
===================================================================
--- libcxx/include/__locale
+++ libcxx/include/__locale
@@ -1183,6 +1183,8 @@
 _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS codecvt_byname<char16_t, char, mbstate_t>)
 _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS codecvt_byname<char32_t, char, mbstate_t>)
 
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void __throw_runtime_error(const char*);
+
 template <size_t _Np>
 struct __narrow_to_utf8
 {
Index: libcxx/include/system_error
===================================================================
--- libcxx/include/system_error
+++ libcxx/include/system_error
@@ -635,7 +635,8 @@
     static string __init(const error_code&, string);
 };
 
-_LIBCPP_FUNC_VIS void __throw_system_error(int ev, const char* what_arg);
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS
+void __throw_system_error(int ev, const char* what_arg);
 
 _LIBCPP_END_NAMESPACE_STD