Hello! Andy Wingo <wi...@pobox.com> writes:
> On Sun 27 Mar 2011 15:29, l...@gnu.org (Ludovic Courtès) writes: > >> Andy Wingo <wi...@pobox.com> writes: >> >>> On Sun 13 Mar 2011 16:25, l...@gnu.org (Ludovic Courtès) writes: >>> >>>> The problem is that ‘hash-create-handle!’ above created a weak-cdr >>>> pair—i.e., a pair whose cdr is /not/ scanned for pointers—but ‘set-cdr!’ >>>> did not register a disappearing link from O to K+V. Consequently, O >>>> eventually gets collected, but K+V remains; the storage of O then gets >>>> reused, and the cdr of K+V ends up containing either an unrelated or >an >>>> invalid Scheme object. >>> >>> Given that we don't expose weak-pair constructors or accessors to >>> Scheme, we should not expose weak pairs to Scheme. What do you think >>> about making it an error to hash-create-handle! on a weak table? That >>> way you never expose a weak pair to Scheme. It does appear possible to >>> discriminate in C between calls to create-handle! that occur due to ref >>> / set! and those that are called explicitly. >> >> Yes, sounds good. Would you like to work on it? :-) > > I have done this now. There were a few places within Guile that were > using the get-handle / create-handle! API with weak hash tables, which I > fixed. It's quite possible that user code also does this, but between > random failures to `(car x)' and preventative errors, I chose the > latter. We can back it down to a warning if that's the right thing to > do, though. Cool, thanks for working on it! I skimmed over the relevant patches and it looks good to me. Ludo’.
