Re: [Sbcl-devel] map-into problem...

[Christophe R. <cs...@ca...>]

Far=C3=A9 <fa...@gm...> writes:

> I think that SBCL is wrong to issue a warning here (and thus bork file
> compilation), but maybe you can explain me instead why I'm doing
> something wrong...

I don't think you're doing something wrong here.

> * (let ((val "foobar"))
>   (map-into (make-array (list (length val)) :element-type '(unsigned-byte=
 8))
>             #'char-code val))
>
> ; caught WARNING:
> ;   Asserted type ARRAY conflicts with derived type
> ;   (VALUES (SIMPLE-ARRAY (UNSIGNED-BYTE 8) (*)) &OPTIONAL).
> ;   See also:
> ;     The SBCL Manual, Node "Handling of Types"

This warning is even more cryptic than usual.  Although it /looks/
utterly nonsensical, the ARRAY it's complaining about is actually (AND
ARRAY (NOT SIMPLE-ARRAY)) -- or in other words, something with a fill
pointer.  I suspect that (DEBUG 2) is confusing the flow analysis of
the compiler, so that it fails to notice that one branch in the above
case is unreachable.

Cheers,

Christophe