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bug#39634: All keyowrds hash to the same value
From: |
Ludovic Courtès |
Subject: |
bug#39634: All keyowrds hash to the same value |
Date: |
Wed, 26 Feb 2020 22:02:29 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) |
Hi Andy!
Andy Wingo <address@hidden> skribis:
> On Thu 20 Feb 2020 17:19, Ludovic Courtès <address@hidden> writes:
>
>> Of all the scm_tc7_ values listed in ‘scm.h’, the following are not
>> explicitly listed (so they go to the default case that hashes the first
>> word):
>
> Reformatting your list so I can check one by one :)
>
>> variable,
>> hashtable,
>> fluid,
>> dynamic_state,
>> frame,
>> atomic_box,
>> program,
>> vm_cont,
>> weak_set,
>> weak_table,
>> port
>
> No equal? implementation, so should hashq() instead.
>
>> bytevector,
>> array,
>> bitvector,
>
> These have equal? implementations, and what's more, a bitvector can
> equal? an array... I think we have another bug!
>
> ;; Project 2d array as 1d array (scm_tc7_array)
> (define x
> (make-shared-array #2b((#t #t #t)) (lambda (i) (list 0 i)) '(0 2)))
> ;; scm_tc7_bitvector
> (define y #*111)
>
> (equal? x y) ;; => #t
> (equal? (hash x #xffffffff) (hash y #xffffffff)) ;; => #f
>
> Similarly for 1-d scm_tc7_array versus regular vectors, bytevectors,
> etc.
Oops.
> Fixing this will not be straightforward... I think basically 1d arrays
> need some special hashing logic so that e.g. vectors and 1d arrays hash
> to the same thing.
OK.
>> stringbuf,
>> values,
>
> These are never exposed to Scheme, and never compared using equal?
> AFAIU. No need for special cases.
Agreed.
> Basically I think the tc7 case should default to hashq, and include
> special cases for the ones that have equal? implementations or which
> have read syntax.
>
> Sound right to you?
It does, yes.
Thanks for looking into it,
Ludo’.