Working with the Reorder

[CodeCrafter18]

Hello!
I have a question regarding the usage of reorders.
For example, let's consider ref_sum.hpp.

if (need_output_reorder()) {
    CHECK(reorder_primitive_desc_create(
		reorder_pds_[n_], engine, dst_acc_md(), dst_md()));
}

In this case, the following function will be called:

status_t reorder_primitive_desc_create(std::shared_ptr<primitive_desc_t> &pd,
        engine_t *engine, const memory_desc_t *src_md,
        const memory_desc_t *dst_md, const primitive_attr_t *attr) {
    return reorder_primitive_desc_create(
            pd, engine, src_md, engine, dst_md, engine, attr);
}

However, in this scenario, create_resource(...) is never called.
If I want to write my own Reorder that overrides the create_resource(...) function,
as it's done in ACL, then I'll get a runtime error when I call ctx.get_resource_mapper()...

How can I work around this problem if my implementation uses resource_mapper?

Also, I have a question about why the Sum, Reorder, and Concat operations have separate logic, for example, for obtaining the list of implementations?​​​​​​​​​​​​​​​​

Thanks.