This is now available for use.
it's basically a proof of concept, showing how gdb.egg (which is
intentionally built for versatility rather than usability) can be used
to construct a mapping from Scheme to C which enables an end user to
debug a Chicken scheme program.
This egg is capable of identifying Scheme source lines known to the
debugger at the level of the C program, and enables the user to set
breakpoints in the corresponding loaded binary image file and then
running the program until execution is interrupted by a breakpoint or
termination of execution.
https://galinha.ucpel.tche.br/svn/chicken-eggs/mayo/
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In due course an installable egg will probably show up here: