Re: [Bug-kawa] Fwd: compiling swank-kawa.scm gives NullPointerException

[Per Bothner]

On 06/12/2012 08:56 PM, Tristan Straub wrote:
> I'm trying to compile swank-kawa.scm but get the following exception:

> $ kawa -C swank-kawa.scm
> ...
> swank-kawa.scm:2122: internal error while compiling swank-kawa.scm
> java.lang.NullPointerException

I've reproduced and simplified this to:

(module-export)
(define (list-env (env :: <gnu.mapping.Environment>))
  (let ((enum (invoke env 'enumerateAllLocations)))
    (let ((pack1 :: <list> '()))
      (let ((pack2 (lambda (v) (set! pack1 (cons v pack1)))))
         (do () (not (invoke enum 'hasMoreElements))
           (pack2 (invoke enum 'nextLocation))))
      (reverse! pack1))))

The key appears to be that list-env is unused and not exported,
which seems to be a semi-bug in swank-kawa.scm.

This confuses the compiler: It thinks pack1 is not needed,
because it is never seen during the validate (type-checking)
phase.  But then it tries to generate bytecode to access pack1.

I haven't figured out the best fix.  If list-env is unused,
then we don't need to generate anything for it.
--
        --Per Bothner
address@hidden   http://per.bothner.com/