Hey, Andy Wingo <wi...@pobox.com> writes:
> On Mon 25 Jan 2010 14:44, l...@gnu.org (Ludovic Courtès) writes: > >> Andy Wingo <wi...@pobox.com> writes: >> >>> - GC_REGISTER_DISPLACEMENT (2*sizeof(scm_t_bits)); /* for the self >>> data pointer */ >>> - GC_REGISTER_DISPLACEMENT (2*sizeof(scm_t_bits) >>> - + scm_tc3_struct); /* for the vtable data >>> pointer */ >>> + /* The first word of a struct is equal to `SCM_STRUCT_DATA (vtable) + >>> + scm_tc3_struct', and `SCM_STRUCT_DATA (vtable)' is 2 words after >>> VTABLE by >>> + default. */ >>> + GC_REGISTER_DISPLACEMENT (2 * sizeof (scm_t_bits) + scm_tc3_struct); >>> >>> I'm pretty sure the first case is still needed, for instance >>> reallocation. It is, as the comment indicates, "for the self data >>> pointer" -- the second word of the object, which normally points to the >>> third word of the object, but for reallocated instances points to the >>> third word of *another* object. >> >> As an excuse, the comment was a bit too terse for me to understand, but >> I get your point now. However, it’s still unclear to me how an ‘s’ >> field can point to something else than “self”. > > Hm, I think you're right; the wording was not only terse but misleading. > It is "for the data pointer, which might point to another object's > data", or something like that. Nothing to do with `s' fields. OK, done: http://git.sv.gnu.org/cgit/guile.git/commit/?id=227eff6a77dd58d64775fe91ae0f1596bfe3371b Thanks, Ludo'.
