Re: Suggestions for smob usages in an extended smob space

[Jim Blandy <jimb@red-bean.com>]

>  > Without having thought through the details, this sounds like a good
>  > idea to me.  However, you'll have 2<<n repeated entries in the smob
>  > table.  Simply enlarging the smob range, but leaving the top eight
>  > bits or so for flags doesn't have this problem.
>  > 
>  > If people subtracted off the base smob number, and then masked off
>  > their bits, it wouldn't be necessary to align the smob numbers.
> 
> Would this cause inconsistencies for applications using independently deviced
> modules containing custom smob types each?

What I mean is, a module would say TAG = scm_newsmobs(funs, n), and
get a range of smob tags, from TAG to TAG + (1 << n) - 1.  Then, to
examine the n flag bits, that module would say (SCM_CAR (obj) - TAG) &
((1 << n) - 1).  To set them you'd have to, um, subtract TAG, frob,
and then add back TAG?  Kinda clumsy, I guess...