[Sbcl-devel] MAPCAN is dangerous

[Alexey D. <ade...@co...>]

Hello,

Thinking about bug 235b. I've found an inconsistency in SBCL. In CLHS
functions NCONC, MAPCAN and MAPCON are defined to return
LISTs. (Particularly, (NCONC 1) seems to be prohibited.) In SBCL NCONC
returns T, MAP* are declared to return LISTs, but it is not
checked. So

  (defun foo ()
    (declare (notinline mapcan))
    (car (mapcan #'car '((1)))))

  (foo) => SEGV

I'd suggest to allow all three functions to return anything. Your
opinions?

-- 
Regards,
Alexey Dejneka