Re: [PATCH v5 1/5] bulk-checkin: extract abstract `bulk_checkin_source`

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> Alternatively, I think some of our other OO code just leaves room for
> a type-specific void pointer, like:
>
>   struct bulk_checkin_source {
> 	...the usual stuff...
>
> 	void *magic_type_data;
>   };
>
> and then the init_bulk_checkin_source_from_fd() function allocates its
> own heap struct for the magic_type_data field and sticks the int in
> there.

Yup.  All the pros-and-cons makes sense.  I earlier said I found
this a good place to stop, exactly because the full OO with 

    struct specific_subclass {
	struct vtbl *vtbl;
	struct base_class common_data_specific_to_instance;
	... other instance specific data members here ...;
    }

would require us to add too many supporting infrastructure struct
types; with only a few subclasses in use, it is a bit too much to
justify.