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; Copyright (c) 1993-2008 by Richard Kelsey and Jonathan Rees. See file COPYING.
; Deal with shadowed variables.
; When a variable is shadowed by a variable, split the existing shared
; location into two replacement locations.
; name (structure-ref p name) (define name ...) within a single template
; will lose big.
;(define *replaced-locations* '()) ;alist of (old rep ((uid ...) . new))
(define (shadow-location! old p-uids new replacement)
(if (location-defined? old)
(set-contents! replacement (contents old)))
(set-location-id! old
(vector replacement p-uids new))
(set-location-defined?! old #f)) ;so that exceptions will be raised
(define maybe-replace-location
(let ((memv memv))
(lambda (loc p-uid) ;Package's unique id
(let ((foo (location-id loc)))
(if (vector? foo)
(maybe-replace-location
(if (memv p-uid (vector-ref foo 1))
(vector-ref foo 2)
(vector-ref foo 0))
p-uid)
loc)))))
; Exception handler:
(define (deal-with-replaced-variables succeed)
(lambda (opcode reason loc template index . rest)
(if (= reason (enum exception undefined-global))
(deal-with-replaced-variable opcode reason loc template index rest
succeed)
(apply signal-vm-exception opcode reason loc rest))))
(define (deal-with-replaced-variable opcode reason loc template index rest
succeed)
(primitive-catch
(lambda (cont)
(if (eq? (template-ref template index) loc)
(let* ((p-uid (template-package-id template))
(new (maybe-replace-location loc p-uid)))
(if (eq? new loc)
(apply signal-vm-exception opcode reason loc rest)
(begin (template-set! template index new)
;(signal 'note "Replaced location" loc new p-uid)
(if (location-defined? new)
(succeed new rest)
(apply signal-vm-exception opcode reason new rest)))))
(error "lossage in deal-with-replaced-variables"
loc index)))))
(define-vm-exception-handler (enum op global)
(deal-with-replaced-variables
(lambda (loc more-args)
(contents loc))))
(define-vm-exception-handler (enum op set-global!)
(deal-with-replaced-variables
(lambda (loc more-args)
(set-contents! loc (car more-args)))))
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