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. Also that would free up our implementation to use something other than weak pairs for weak hash tables. In particular, I think first-class weak references are not a bad idea, as Chez Scheme does. WDYT? Andy -- http://wingolog.org/
