Re: [Chicken-janitors] #905: Unreliable behavior of hash tables with symbols as keys (regression wrt 4.7.4)

[Chicken Trac]

#905: Unreliable behavior of hash tables with symbols as keys (regression wrt
4.7.4)
-----------------------------+----------------------------------------------
  Reporter:  iraikov         |       Owner:       
      Type:  defect          |      Status:  new  
  Priority:  critical        |   Milestone:  4.8.0
 Component:  core libraries  |     Version:  4.8.x
Resolution:                  |    Keywords:       
-----------------------------+----------------------------------------------

Comment(by sjamaan):

 Hi Ivan,

 Perhaps I'm missing something, but you're using gensyms here.  Those are
 uninterned, which means that any gensym'ed symbol is not {{eq?}} to a
 user-inserted symbol with the same printed representation. See this
 slightly modified version of your code:

 {{{
 (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)
     (when (= v 9) ;; modification starts here
       (printf "Referencing ~A => ~A~%" k (hash-table-ref t k))
       (printf "Referencing ~A => ~A~%" 'k15 (hash-table-ref t 'k15))))
   (list-tabulate 10 (lambda (i) (gensym 'k)))
   (list-tabulate 10 (lambda (i) i)))

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


 For me, this prints:

 {{{
 hash-table-set! k24 0
 hash-table-set! k23 1
 hash-table-set! k22 2
 hash-table-set! k21 3
 hash-table-set! k20 4
 hash-table-set! k19 5
 hash-table-set! k18 6
 hash-table-set! k17 7
 hash-table-set! k16 8
 hash-table-set! k15 9
 Referencing k15 => 9

 Error: (hash-table-ref) hash-table does not contain key
 k15
 #<hash-table (11)>
 }}}

 This is exactly as expected.  Are you using gensyms in your actual
 program?

-- 
Ticket URL: <http://bugs.call-cc.org/ticket/905#comment:3>
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