GNU bug report logs - #46175
Redefinable classes clobber custom slot options

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Andy Wingo <wingo <at> pobox.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#46175: closed (Redefinable classes clobber custom slot options)
Date: Sat, 20 Mar 2021 19:03:02 +0000

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Your message dated Sat, 20 Mar 2021 20:02:29 +0100
with message-id <87lfahwsvu.fsf <at> pobox.com>
and subject line Re: bug#46175: Redefinable classes clobber custom slot options
has caused the debbugs.gnu.org bug report #46175,
regarding Redefinable classes clobber custom slot options
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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46175: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=46175
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From: "Thompson, David" <dthompson2 <at> worcester.edu>
To: bug-guile <at> gnu.org
Subject: Redefinable classes clobber custom slot options
Date: Fri, 29 Jan 2021 11:43:35 -0500

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The compute-slots method for <redefinable-class> does a transformation
of #:allocation #:instance slots to #:allocation #:virtual slots, but
in doing so it discards all slot options besides the standard ones.
This means that a metaclass that inherits from <redefinable-class>
won't work as expected if it relies upon custom slot options.

Test case:

    (use-modules (oop goops)
                 (srfi srfi-111))

    (define-class <meta> (<class>))

    (define (boxed-slot? slot)
      (get-keyword #:box? (slot-definition-options slot)))

    (define-method (compute-getter-method (class <meta>) slot)
      (if (boxed-slot? slot)
          (make <method>
            #:specializers (list class)
            #:procedure (let ((slot-name (slot-definition-name slot)))
                          (lambda (obj)
                            (unbox (slot-ref obj slot-name)))))
          (next-method)))

    (define-method (compute-setter-method (class <meta>) slot)
      (if (boxed-slot? slot)
          (make <method>
            #:specializers (list class <top>)
            #:procedure (let ((slot-name (slot-definition-name slot)))
                          (lambda (obj value)
                            (set-box! (slot-ref obj slot-name) value))))
          (next-method)))

    (define-class <redefinable-meta> (<meta> <redefinable-class>))

    (define-class <foo> ()
      (bar #:accessor bar #:box? #t #:init-form (box 123))
      #:metaclass <meta>)

    (define-class <redefinable-foo> ()
      (bar #:accessor bar #:box? #t #:init-form (box 123))
      #:metaclass <redefinable-meta>)

    ;; This works:
    (pk (+ (bar (make <foo>)) 456))

    ;; This throws an error:
    (pk (+ (bar (make <redefinable-foo>)) 456))

Attached is a patch that preserves all slot options that redefinable
classes do not need to alter, including custom ones.  How does it
look?

- Dave

[0001-goops-Preserve-all-slot-options-in-redefinable-class.patch (text/x-patch, attachment)]

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From: Andy Wingo <wingo <at> pobox.com>
To: "Thompson, David" <dthompson2 <at> worcester.edu>
Cc: 46175-done <at> debbugs.gnu.org
Subject: Re: bug#46175: Redefinable classes clobber custom slot options
Date: Sat, 20 Mar 2021 20:02:29 +0100

On Fri 29 Jan 2021 17:43, "Thompson, David" <dthompson2 <at> worcester.edu> writes:

> The compute-slots method for <redefinable-class> does a transformation
> of #:allocation #:instance slots to #:allocation #:virtual slots, but
> in doing so it discards all slot options besides the standard ones.
> This means that a metaclass that inherits from <redefinable-class>
> won't work as expected if it relies upon custom slot options.

Thanks for the report; patch applied!

Andy

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