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
