id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	difficulty
905	Unreliable behavior of hash tables with symbols as keys (regression wrt 4.7.4)	Ivan Raikov		"The nemo program relies heavily on performing transformations over hash tables with symbols as keys. It works fine with Chicken 4.7.4, but unfortunately there seems to have been a regression in 4.8.0rc1, which results in hash-table-exists? and hash-table-ref failing to find any of the existing keys in the table after a number of transformations have been performed. 
The following code reproduces the issue:

{{{

(use srfi-1 srfi-69)

(define t (make-hash-table hash: symbol-hash))

(hash-table-set! t 'k1 1)
(hash-table-ref t 'k1)

(for-each
  (lambda (k v)
    (printf ""hash-table-set! ~A ~A~%"" k v)
    (hash-table-set! t k v))
  (list-tabulate 10 (lambda (i) (gensym 'k)))
  (list-tabulate 10 (lambda (i) i))
  )

(print (hash-table-ref t 'k15))
}}}

Perhaps the hash tables stop working after some garbage collections have been performed. This issue is not entirely new; nemo previously used the environments egg, which was also exhibiting similar unreliable behavior, so I had resorted to using strings instead of symbols as keys. Any advice on how to debug this would be appreciated."	defect	new	critical	4.8.0	core libraries	4.8.x