[clpython-devel] Re: CLPython on SBCL

[Willem Broekema]

Hello Bob,

On Thu, May 1, 2008 at 5:52 PM, Robert Brown <brown at google.com> wrote:

> I tried to get CLPython up and running on the latest SBCL.  The diff below
> contains a couple of easy fixes.  SBCL wants BREAK's argument to be a
> string
> and SBCL's LOOP does not like a negative loop increment.


Thanks for the patches!


> The real porting problem right now is CLOS related.  SBCL does not like
> the
> following code in core/classes.lisp:
>
>    ;; Fix superclass and metaclass of PY-DICT.
>    (ensure-class 'py-dict
>                  :direct-superclasses (list 'py-core-object)
>                  :metaclass 'py-core-type)
>
> I get the following error:
>
>    debugger invoked on a SB-PCL::METAOBJECT-INITIALIZATION-VIOLATION in
> thread
>    #<THREAD "initial thread" {11701A79}>:
>      Cannot CHANGE-CLASS objects into CLASS metaobjects.
>    See also:
>      AMOP, Initialization of Class Metaobjects
>
> I think the problem is that PY-DICT is a normal class and the ENSURE-CLASS
> call tries to turn it into a metaclass.  Anyway, I'm far from a CLOS
> expert.


Well, class py-dict is not turned into a metaclass here, at least that's not
the intention. :) The superclass and metaclass of it are changed but py-dict
remains a non-metaclass class. So I think the actual error message is
incorrect, but something else is wrong.

The problem might be that you can not change the metaclasses of a class
using ensure-class. Could you please check if the call to ensure-class
without the metaclass change is accepted?

(ensure-class 'py-dict
                    :direct-superclasses (list 'py-core-object))

Thanks,
- Willem
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