GNU bug report logs - #23404
Infinite recursion in GOOPS in Guile 2.2

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Christopher Allan Webber <cwebber <at> dustycloud.org>
Subject: bug#23404: closed (Re: bug#23404: Infinite recursion in GOOPS in
 Guile 2.2)
Date: Tue, 28 Feb 2017 15:13:02 +0000

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Your bug report

#23404: Infinite recursion in GOOPS in Guile 2.2

which was filed against the guile package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 23404 <at> debbugs.gnu.org.

-- 
23404: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23404
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Andy Wingo <wingo <at> pobox.com>
To: Christopher Allan Webber <cwebber <at> dustycloud.org>
Cc: 23404-done <at> debbugs.gnu.org
Subject: Re: bug#23404: Infinite recursion in GOOPS in Guile 2.2
Date: Tue, 28 Feb 2017 16:12:46 +0100

On Sat 30 Apr 2016 04:27, Christopher Allan Webber <cwebber <at> dustycloud.org> writes:

> It looks like my example was incomplete.  It turns out loading and
> passing in an srfi-9 record is critical to instantiating the bug.
>
> Why?  I'm not sure...
>
>   (use-modules (oop goops)
>                (srfi srfi-9))
>   (define-class <some-class> ())
>   (define-record-type <some-record>
>     (make-some-record foo)
>     some-record?
>     (foo some-record-foo))
>   
>   (define-method (time-to-break (some-class <some-class>) not-a-class)
>     (display "We're never going home are we?\n"))
>   
>   ;; Now it'll break
>   (time-to-break (make <some-class>) (make-some-record 1))

This appears to be fixed, somehow (?).  Please reopen if you can still
produce the bug.

Andy

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From: Christopher Allan Webber <cwebber <at> dustycloud.org>
To: bug-guile <at> gnu.org
Subject: Infinite recursion in GOOPS in Guile 2.2
Date: Fri, 29 Apr 2016 19:27:56 -0500

Heya all,

So I've been building something with GOOPS, and I decided to try it out
with Guile 2.2.  Unfortunately, I hit a pretty nasty bug.  You can try
it yourself... the code is pretty short:

  (use-modules (oop goops)
               (srfi srfi-9))
  (define-class <some-class> ())
  (define-method (time-to-break (some-class <some-class>) not-a-class)
    (display "We're never going home are we?\n"))

  ;; And now, call it
  (time-to-break (make <some-class>) 1)

This will loop forever and *never* complete.  Why?

Turns out this is why, from goops.scm:

  (define (single-arity-cache-dispatch cache nargs cache-miss)
    (match cache
      (() cache-miss)
      (((typev . cmethod) . cache)
       (cond
        ((eqv? nargs (vector-length typev))
         (let ((cache-miss (single-arity-cache-dispatch cache nargs cache-miss)))

I'm not sure what was supposed to happen (presumably the cache was
supposed to be narrowed down somehow), but what happens here is that
single-arity-cache-dispatch keeps calling single-arity-cache-dispatch
forever.

scheme@(guile-user) [1]> ,bt
In oop/goops.scm:
   1437:41939 (cache-miss #<<hive> e8a1e0> #<<message> id: "5c787e65bbeb34b27ffd16eead286fc6:1" to: ("8394701db8…>)
   1486:41938 (memoize-effective-method! _ _ _)
  1466:131937 (recompute-generic-function-dispatch-procedure! #<<generic> hive-process-message (1)>)
  1452:161936 (compute-generic-function-dispatch-procedure _)
  1378:251935 (single-arity-cache-dispatch _ 2 _)
  1378:251934 (single-arity-cache-dispatch _ 2 _)
  1378:251933 (single-arity-cache-dispatch _ 2 _)
  1378:251932 (single-arity-cache-dispatch _ 2 _)
  1378:251931 (single-arity-cache-dispatch _ 2 _)
  1378:251930 (single-arity-cache-dispatch _ 2 _)
  1378:251929 (single-arity-cache-dispatch _ 2 _)
  1378:251928 (single-arity-cache-dispatch _ 2 _)
  1378:251927 (single-arity-cache-dispatch _ 2 _)
  1378:251926 (single-arity-cache-dispatch _ 2 _)
  1378:251925 (single-arity-cache-dispatch _ 2 _)
  1378:251924 (single-arity-cache-dispatch _ 2 _)
  ... etc ...

(g?)Oops!

 - Chris

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