https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97105
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> --- >From what I can see, when doing pushdecl of the extern a declaration the VAR_DECL is pushed into incomplete_vars, then when seeing the definition pushdecl is called again and during duplicate_decls it is turned into no longer DECL_EXTERNAL, but the type hasn't been instantiated yet. Then start_decl calls start_decl_1 which calls complete_decl and that sees an incomplete type that can't be completed and errors. One way out of this might be not call layout_var_decl if !COMPLETE_TYPE_P (type). Another one might be to let start_decl_1 record in some global variable that it is processing (if it is) a variable with [] array and let complete_vars skip that var.
