https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71611
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- This has nothing to do with enums based on long, but about anonymous enums. <unknown> is what is used for all types that don't have a name. Would you prefer <anonymous enum> instead or <anonymous enum at file:line>?
