Attempt to unread too many characters ...

Luís Oliveira luismbo at
Thu Oct 17 10:25:48 UTC 2013

Andrew Myers <asm198 at> writes:

>> attempt to unread too many characters on
>> #<TWO-WAY-STREAM "" @ #x100010c8c22>
> Is this a problem with Franz Lisp?  Slime, Swank?  I'm not really sure
> where I should start looking at this point.  Any help is appreciated.

I believe this is an ACL bug. You can reproduce it independently of
slime-repl as follows:

      ((error (lambda (e)
                (let ((*query-io* (make-two-way-stream
                                    (lambda () (format nil "10~%")))
                  (invoke-restart-interactively 'store-value)))))
    (eval 'a))

It seems that INVOKE-RESTART-INTERACTIVELY or something else more
specific to the STORE-VALUE restart is doing too many UNREAD-CHARs which
is not supported by the gray stream that SWANK has setup for
*QUERY-IO*. (I don't remember enough details about gray streams to know
whether this a general gray stream thing or something else.)

Also, this happens in ACL 9.0 but not ACL 8.1.

Can you report it to Franz?


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