[clisp-list] hashtable breakage

[<don...@is...>]

I'm still trying to figure out how the test posted by Bruno works.
Can someone explain?  Below is a version that's improved for purposes
of adding an entry to the test suite.  See the comments therein.

;; no longer used
(defun hash-table-keys (ht)
  (loop :for kk :being :each :hash-key :of ht :collect kk))

;; no longer used - see next
(defun check-hash-unique (ht)
  (let ((hash-ok t))
    (do* ((keys (hash-table-keys ht) (cdr keys))
          (key (car keys) (car keys))
          (other-keys (cdr keys) (cdr keys)))
         ((null keys) hash-ok)
      (when (member key other-keys)
        (format t "ERROR! key ~s occurs multiple times!~%" key)
        (setf hash-ok nil)))))

;; if you really want to find the duplicate entries, this is much faster
;; if you just want to test it's not necessary
(defun check-hash-unique2 (ht)
  (let ((h2 (make-hash-table :test 'equal)))
    (loop :for kk :being :each :hash-key :of ht do
      (if (gethash kk h2)
	  (format t "ERROR! key ~s occurs multiple times!~%" kk)
	(setf (gethash kk h2) t)))))

(defun do-hash-test (ht)
  (clrhash ht)
  (loop for countval upfrom 1 upto 15000
    for key = (cons "HT" countval)
    ;; (format nil "HT-~D" countval)
    ;; same problem occurs with cons but a lot faster than format
    do
      ;;(gethash key ht)
      (setf (gethash key ht) t)
      (setf (gethash key ht) t) ;; was countval
      ;; The gethash seems unnecessary in the sense that the failure
      ;; occurs without it.  Similarly, it occurs whether the two
      ;; assignments use the same value or not.  
      ;; But two assignments are needed.
      ;; This part I don't understand.
      ;; Is the problem related to gc between the two?
      ;; I tried putting a gc between the two and the problem went away.
      ;; If there's no gc between the two then I'd expect the second
      ;; to be a noop.  If the problem is a gc during one then why do
      ;; we need two?
    finally
    (format t "~A entries~%"
	    (loop :for kk :being :each :hash-key :of ht :count t))
    ;; as a test it suffices to count the entries (above)    	    
    ;; (check-hash-unique2 ht) ;; only if you want to see the duplicates
    ))

(loop :repeat 2 :do
  (loop :with ht = (make-hash-table :size 1000)
    ;; the size doesn't seem to matter
    ;; I get the bug with no size or 20000 or 100000
    :for i :from 1 :to 10 :do
    (format t "~& --- ~d ---~%" i)
    (do-hash-test ht)))