https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109512
--- Comment #2 from kargl at gcc dot gnu.org ---
This patch catches the need for an external attribute.
diff --git a/gcc/fortran/resolve.cc b/gcc/fortran/resolve.cc
index 6e42397c2ea..1e19712b413 100644
--- a/gcc/fortran/resolve.cc
+++ b/gcc/fortran/resolve.cc
@@ -3818,6 +3818,16 @@ resolve_call (gfc_code *c)
/* Resume assumed_size checking. */
need_full_assumed_size--;
+ /* If 'implicit none (external)' and the symbol is a dummy argument,
+ check for an 'external' attribute. */
+ if (csym->ns->has_implicit_none_export
+ && csym->attr.external == 0 && csym->attr.dummy == 1)
+ {
+ gfc_error ("Dummy procedure %qs at %C requires an EXTERNAL attribute",
+ csym->name);
+ return false;
+ }
+
/* If external, check for usage. */
if (csym && is_external_proc (csym))
resolve_global_procedure (csym, &c->loc, 1);
A dejagnu-ified testcase.
! { dg-do compile }
subroutine foo(bar)
implicit none (external)
call bar(1) ! { dg-error "requires an EXTERNAL attribute" }
end subroutine foo
