#6: GCed items in weak hash tables are still accessible (with random junk) --------------------+------------------------------------------------------- Reporter: rtoy | Owner: somebody Type: defect | Status: new Priority: major | Milestone: Component: Core | Version: 19c Keywords: | --------------------+------------------------------------------------------- Consider this simple transcript:

{{{ * (defvar *ht* (make-hash-table :weak-p t)) *HT* * (setf (gethash (list 1) *ht*) (list 2)) (2) * *ht* #<EQL hash table, 1 entry> * (prog1 t (make-list 1000000)) T * (gc :full t) NIL * *ht* #<EQL hash table, 0 entries> * (maphash #'(lambda (k v) (format t "~S -> ~S~%") k v) *ht*) (7 . :INSTANCE) -> (#<Function "DEF-STREAM-CLASS SIMPLE-STREAM">) }}}

This is totally bogus. I think the problem is that when GC cleans up the weak entry, it doesn't fill in the entry in the table with the empty value. Instead it remains, and ends up pointing to random objects in memory.