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67678b0)
Consider:
[link = SodClass] class MyClass: SodClass { }
[metaclass = MyClass] class Foo: SodObject { }
GCC reports:
/tmp/mdw/t.c:258:33: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]
/* _class = */ &Foo__classobj.obj.myclass,
^
/tmp/mdw/t.c:258:33: note: (near initialization for ‘Foo__vtable_obj.obj._class’)
What's going on here is that it's writing the wrong metaclass pointer
into the `_class' pointer on `Foo''s secondary `obj' chain.
Fix this by choosing, for each class pointer, the most specific
superclass of the overall metaclass that is (a) on the correct chain of
the metaclass, and (b) is a superclass of the metaclass of the most
specific class in the chain whose vtable we're writing. Whew!
((class sod-class) (chain-head sod-class)
(metaclass sod-class) (meta-chain-head sod-class))
((class sod-class) (chain-head sod-class)
(metaclass sod-class) (meta-chain-head sod-class))
- ;; Slightly tricky. We don't necessarily want a pointer to the metaclass,
- ;; but to its most specific subclass on the given chain. Fortunately, CL
- ;; is good at this game.
- (let* ((meta-chains (sod-class-chains metaclass))
- (meta-chain-tails (mapcar #'car meta-chains))
- (meta-chain-tail (find meta-chain-head meta-chain-tails
- :key #'sod-class-chain-head)))
+ ;; Rather tricky. This is a class pointer on a vtable for the CHAIN-HEAD
+ ;; chain, pointing into the META-CHAIN-HEAD chain of the metaclass. We
+ ;; need to produce a pointer to the most specific superclass of the
+ ;; metaclass on the right chain that is a superclass of the metaclass of
+ ;; the most specific class in the superclass chain headed by CHAIN-HEAD.
+ (flet ((chain-tail (class head)
+ (find head (mapcar #'car (sod-class-chains class))
+ :key #'sod-class-chain-head)))
(make-instance 'class-pointer
(make-instance 'class-pointer
- :class class
- :chain-head chain-head
- :metaclass meta-chain-tail
+ :class class :chain-head chain-head
+ :metaclass (chain-tail (sod-class-metaclass
+ (chain-tail class chain-head))
+ meta-chain-head)
:meta-chain-head meta-chain-head)))
;;; base-offset
:meta-chain-head meta-chain-head)))
;;; base-offset
;; If this class introduces new metaclass chains, then emit pointers to
;; them.
;; If this class introduces new metaclass chains, then emit pointers to
;; them.
- (let* ((metasuper (sod-class-metaclass super))
+ (let* ((metaclass (sod-class-metaclass class))
+ (metasuper (sod-class-metaclass super))
(metasuper-chains (sod-class-chains metasuper))
(metasuper-chain-heads (mapcar (lambda (chain)
(sod-class-chain-head (car chain)))
(metasuper-chains (sod-class-chains metasuper))
(metasuper-chain-heads (mapcar (lambda (chain)
(sod-class-chain-head (car chain)))
(unless (member metasuper-chain-head *done-metaclass-chains*)
(funcall emit (make-class-pointer class
chain-head
(unless (member metasuper-chain-head *done-metaclass-chains*)
(funcall emit (make-class-pointer class
chain-head
metasuper-chain-head))
(push metasuper-chain-head *done-metaclass-chains*))))
metasuper-chain-head))
(push metasuper-chain-head *done-metaclass-chains*))))