Re: read crashes on shared structure

Unfortunately, the crash is back at the next level of nesting...

(define x (list 'x))

(set-car! x x)

(define y (list 'y 'x))

(set-car! y y)

(set-car! (cdr y) x)

(define z (list 'z 'y 'x))

(set-car! z z)

(set-car! (cdr z) y)

(set-car! (cddr z) x)

z = #0=(#0# #1=(#1# #2=(#2#)) #2#)

= *** ERROR:bigloo:

`segmentation violation' exception -- raised

This is indeed a bug in the reader, that I have hopefully fixed.