Check call depth when mrb_yield_class() is called; ref #3521

src/vm.c

@@ -668,6 +668,9 @@ mrb_yield_with_class(mrb_state *mrb, mrb_value b, mrb_int argc, const mrb_value
   if (mrb_nil_p(b)) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "no block given");
   }
+  if (mrb->c->ci - mrb->c->cibase > MRB_FUNCALL_DEPTH_MAX) {
+    mrb_exc_raise(mrb, mrb_obj_value(mrb->stack_err));
+  }
   p = mrb_proc_ptr(b);
   ci = cipush(mrb);
   ci->mid = mid;