pngload fails to load about clasp HOT 4 OPEN

One of the places in pngload which signals the error is the (UB8) call in (DEFINE-CHUNK PLTE ...): Replacing the call with NIL fixes the compilation error. Also, when repeatedly interactively evaluating the DEFINE-CHUNK form, sometimes the error is signaled, sometimes not.

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Here is a minimal reproducible example which causes the error:

(defun parse-chunk/plte ()
  (let ((v (make-array 0)))
    (labels ((ub8 ()
               (aref v 0))
             (read-bytes ()
               (map-into (make-array 0) #'ub8)))
      (ub8))))

(The naming is a relic of my having started from (DEFINE-CHUNK PLTE ...) and having progressively macroexpanded and removed unnecessary parts.)

from clasp.

The same error is still present on latest Clasp, but I cannot reproduce it with the above minimal reproducible example. It might be easier to debug starting from c4a56ca.

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Reproduced. As you said, it's intermittent, and that's due to the occasionally nondeterministic nature of Cleavir. The error is during flow order recomputation during meta evaluation, so I'm going to guess this is another instance of #1442, which I am working towards fixing comprehensively at the moment. Alternately it could be due to something going wrong while deleting the unused function.

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