Hello, Neil Jerram <n...@ossau.uklinux.net> writes:
> l...@gnu.org (Ludovic Courtès) writes: [...] >> Instead what's really needed is a special pointer-to-reclaimed-object >> value that can be distinguished from valid Scheme values since that >> value ends up in the car or cdr of weak pairs in hash table buckets. As >> such, SCM_PACK (NULL) was a good choice until now. > > Here I'm confused again. I thought we now had no choice about the > pointer-to-reclaimed-object value, because BDW-GC always uses NULL. True. So, what I meant is that ((SCM) NULL) must be distinguishable from valid Scheme values. >> SCM_UNDEFINED == 0 would work fine because SCM_UNDEFINED is not a valid >> Scheme value, but it wouldn't change the implementation. > > I'm afraid I don't understand "but it wouldn't change the > implementation". Ugly stuff like ‘scm_fixup_weak_alist ()’ would still be needed. > SCM_UNDEFINED == 0 is sounding promising... Yeah. Sorry for the false hope about SCM_BOOL_F == 0. Thanks, Ludo’.
