https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80135
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The glibc people should know (or you can try building glibc). That said, I think rejecting structs with flexible array members is unnecessary, e.g. the C FE doesn't reject them either, what we should reject is non-empty initializers of those inside arrays (because we can't grow the array element sizes to accomodate them).
