[Bug fortran/71730] ICE when character length specification uses an undefined variable

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71730

--- Comment #1 from kargl at gcc dot gnu.org ---
Index: decl.c
===================================================================
@@ -905,6 +906,7 @@ char_len_param_value (gfc_expr **expr, b
     goto syntax;
   else if ((*expr)->expr_type == EXPR_VARIABLE)
     {
+      bool t;
       gfc_expr *e;

       e = gfc_copy_expr (*expr);
@@ -916,7 +918,15 @@ char_len_param_value (gfc_expr **expr, b
          && e->ref->u.ar.dimen_type[0] == DIMEN_RANGE)
        goto syntax;

-      gfc_reduce_init_expr (e);
+      t = gfc_reduce_init_expr (e);
+
+      if (!t && (e->ts.type == BT_UNKNOWN
+                && e->symtree->n.sym->attr.untyped == 1
+                && e->symtree->n.sym->ns->seen_implicit_none == 1))
+       {
+         gfc_free_expr (e);
+         goto syntax;
+       }

       if ((e->ref && e->ref->type == REF_ARRAY
           && e->ref->u.ar.type != AR_ELEMENT)