with-foreign-object allocation question

I am trying to fix a lethal memory bug in
 https://github.com/StjepanPoljak/musicli src/jack.c: (start-jack-callbacks)
where there is a call

  (cffi:with-foreign-object (args '(:pointer (:struct jack-cb-args)))
     ... clobber 24 bytes == (sizeof (:struct jack-cb-args))
        allocated at ARGS ...)

which should really read

  (cffi:with-foreign-object '(:struct jack-cb-args) ...)

this reliably crashes other lisps, but not lwl 64 personal.  what
could be the reason for this resiliance? macroexpansion on the
incorrect form shows

(fli:with-dynamic-foreign-objects nil
  (let* ((#:size6844 8)
         (args (fli:alloca :type :byte :nelems #:size6844)))

Which shows only 8 bytes being allocated. but are allocations aligned
at > 24byte offsets, so the memory corruption doesn't show up in
lispworks in this case?

-- Madhu

(project author bcc'd)

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