Native code stepper for lispworks?

Hi list!

When digging into lispworks compiled functions, I found that there is
vector attached to every function, which maps code offsets into source
"offsets". This vector seem to be used by debugger when finding a
source of a frame.

I wonder is there a way to implement native code stepper this way?
Lispworks instrumentation based stepper is fine, but it has some
disadvanteges. Consider the following example:

#.(defpackage :test3
  (:use :cl))

(in-package :test3)

(defun steppable (x)
  (+ x 1))

(defun nonsteppable (x)
  (+ (steppable x) (steppable x)))


if I put breakpoint in "steppable" and then call "nonsteppable", I'm
unable to continue stepping out of steppable function. When I write
just (break) somewhere, I unable continue stepping. And so on. Next, I
guess stepper uses an interpreter. If code contains compiler-macros,
its behaviour can differ in stepped code and in truly compiled one.
Combined, these disadvantages make stepper very inconvinient compared
e.g. to Delphi (and, likely, C#, Visual Basic etc...) source level
debuggers. Yes, I'm aware of trace, incremental development, logging,
restarting frames, but there is still some essential inconvinience.

I have made some experimens. I was able to alter compiled machine code
and put int 3 instruction into it (32bit Windows):

(in-package :cl-user)

(defun extract-address-from-function (function)
  "Stupid: extract function address from printed representation"
  (assert (functionp function))
  (let* ((text (format nil "~A" function))
         (length (length text))
         (offset (- length 9))
         (hex-address (subseq text offset (+ offset 8)))
         (*read-base* 16)
         (address (read-from-string hex-address)))
    address))

(defun poke (addr byte)
  (setf (fli:dereference (fli:make-pointer :address addr :type :byte)) byte))

(cl-user::poke (+ (cl-user::extract-address-from-function
#'TEST3::nonsteppable) 28) #xCC)

This seem to be the first step to implement true native code
breakpoints. On a stack I found win32::exception-reentry-function, and
was able to return something from it, but stack was smashed. I guess
one need to create corrent int 3 handler, but I do not know how to do
this.

If I was able just to continue execution from int 3, this would be the
core of native code breakpoints and stepper implmenetation.

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