Re: [MIT-Scheme-devel] weak hash table data

[Taylor R Campbell]

   Date: Tue, 22 Dec 2009 02:04:03 -0800
   From: Chris Hanson <address@hidden>

   This is incorrect.  GC marks every table as needing rehash; the next
   access to that table forces a rehash, which cleans the table.

Right, although HASH-TABLE/DATUM-LIST and friends don't count as
`access'.  Still, weak hash tables that are not in frequent use will
not be cleaned, nor will weak hash tables that are not GC-sensitive.
For example, a weak hash table keyed by symbols with SYMBOL-HASH as
its hash function rather than EQ-HASH (or one keyed by URIs with
(COMPOSE STRING-HASH URI->STRING) as its hash function, since interned
symbols are now held strongly as keys).