debugging Emacs LISP functions

[hector]

I have a problem with Emacs. Basically it doesn't do what I want it to do :-)
Or put it another way, it doesn't behave as I expect it to behave.

I tried debugging the offending function (dir-locals-find-file)
and then I found another problem.

Perhaps I just don't get acquainted to the LISP typing system.
This function can return a string or a list. Is this good coding style?
But that's another question. Perhaps this mail should go to the
emacs-devel mailing list. I don't know. With free software you just
loose the difference between a "user" and a "developer". Anyway I see
some developers read this list every now and then.

When I try to debug LISP code that is part of Emacs I see with some functions
I get the source code and with others I just get "byte-code". In the latter
case I can't debug it because the debugger just skips the whole function.

How can I know what functions appear as "byte-code" in the debugger?
And how can I debug them?