I think the worry was that there are zillions of such types (mode_t, dev_t, pid_t, etc.), too many to define a function for each. For valid gid_t and uid_t values one can use umaxtostr in practice, and there seemed to be little point to tuning for platforms where gid_t and uid_t are narrower than uintmax_t.
- [PATCH] inttostr: add gidtostr and uidtostr Bernhard Voelker
- Re: [PATCH] inttostr: add gidtostr and uidtostr Paul Eggert
- Re: [PATCH] inttostr: add gidtostr and uidtostr Bernhard Voelker
- Re: [PATCH] inttostr: add gidtostr and uidtostr Eric Blake