class.c (prepare_singleton_class): remove unnecessary write barrier
Since sc (singleton class) is a newly created object so it's not needed
to call write barrier.
MODIFY
src/class.c
src/class.c
@@ -392,7 +392,6 @@ prepare_singleton_class(mrb_state *mrb, struct RBasic *o)
}
o->c = sc;
mrb_field_write_barrier(mrb, (struct RBasic*)o, (struct RBasic*)sc);
- mrb_field_write_barrier(mrb, (struct RBasic*)sc, (struct RBasic*)o);
mrb_obj_iv_set(mrb, (struct RObject*)sc, MRB_SYM(__attached__), mrb_obj_value(o));
sc->flags |= o->flags & MRB_FL_OBJ_IS_FROZEN;
}

class.c (prepare_singleton_class): remove unnecessary write barrier

Since sc (singleton class) is a newly created object so it's not needed
to call write barrier.