1 files changed, 13 insertions, 0 deletions
diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index 21126cb..1f4abd0 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -2974,6 +2974,19 @@ resolve_unknown_f (gfc_expr *expr)
       return false;
     }
 
+  /* IMPLICIT NONE (external) procedures require an explicit EXTERNAL attr.  */
+  /* Intrinsics were handled above, only non-intrinsics left here.  */
+  if (sym->attr.flavor == FL_PROCEDURE
+      && sym->attr.implicit_type
+      && sym->ns
+      && sym->ns->has_implicit_none_export)
+    {
+	  gfc_error ("Missing explicit declaration with EXTERNAL attribute "
+	      "for symbol %qs at %L", sym->name, &sym->declared_at);
+	  sym->error = 1;
+	  return false;
+    }
+
   /* The reference is to an external name.  */
 
   sym->attr.proc = PROC_EXTERNAL;