[armedbear-devel] Forward referenced classes woes

[Rudolf Schlatte]

Hi,

Thanks for the nice report and diagnosis!  Should be fixed in r14092, which also fixes two ansi-test failures and gets us one component further in compiling McCLIM.

Rudi

On Aug 11, 2012, at 16:20, Stas Boukarev <stassats at gmail.com> wrote:

> Consider the following code:
> 
> (defclass whitespace-normalizer (sax-proxy))
> 
> (defclass sax-proxy (broadcast-handler)
>  ())
> 
> (defclass broadcast-handler ()
>  ((handlers :initform nil
> 	     :initarg :handlers
> 	     :accessor broadcast-handler-handlers)))
> 
> Doing the followoing results in errors:
> 
> (setf (broadcast-handler-handlers (make-instance 'whitespace-normalizer)) 10)
> 
> There is no applicable method for the generic function
> #<STANDARD-GENERIC-FUNCTION (SETF BROADCAST-HANDLER-HANDLERS)
> {6621477C}> when called with arguments (10 #<WHITESPACE-NORMALIZER
> {14BAAEA8}>).
> 
> (setf (broadcast-handler-handlers (make-instance 'sax-proxy)) 10) 
> 
> The slot HANDLERS is missing from the class #<STANDARD-CLASS SAX-PROXY
> {1700FFDB}>.
> 
> The problem is that whitespace-normalizer and sax-proxy are
> finalized too early.
> 
> Finalization happens in std-after-initialization-for-classes
> http://trac.common-lisp.net/armedbear/browser/trunk/abcl/src/org/armedbear/lisp/clos.lisp#L857
> 
> by calling maybe-finalize-class-subtree, which in its turn finalizes the
> class and its subclasses in case the class has all its superclasses
> finalized.
> 
> When (defclass whitespace-normalizer (sax-proxy)) is executed it creates
> a forward-referenced-class for sax-proxy, and when sax-proxy is defined
> it calls a method for ensure-class-using-class
> http://trac.common-lisp.net/armedbear/browser/trunk/abcl/src/org/armedbear/lisp/clos.lisp#L3121
> for forward-referenced-classes. Before calling reinitialize-instance it
> does (change-class class metaclass) to change from forward-referenced to
> normal class. change-class in its turn calls shared-initialize method,
> which calls the aforementioned std-after-initialization-for-classes, but
> it doesn't supply any direct-superclass arguments. So, when
> maybe-finalize-class-subtree is called it thinks that sax-proxy's sole
> superclass is standard-object, so it goes ahead finalizing sax-proxy and
> whitespace-normalizer at the wrong time with wrong information. And
> ensure-class-using-class later call with the right direct-superclass
> information doesn't matter anymore, since the classes were already badly
> finalized 
> 
> -- 
> With best regards, Stas.
> 
> _______________________________________________
> armedbear-devel mailing list
> armedbear-devel at common-lisp.net
> http://lists.common-lisp.net/cgi-bin/mailman/listinfo/armedbear-devel