Making Emacs Lisp easier to debug

[Alan Mackenzie <acm@muc.de>]

Hello, Emacs.

Despite some recent improvements, and some which are currently being
worked on, there are still scenarios where Lisp is difficult to debug.
It is possible that we might be able to improve matters.  The two
scenarios I have in mind at the moment are:

(i) Edebugging macro expansions.  What happens at the moment is that the
arguments given to the macro, when given a suitable edebug spec, get
edebugged, but the code generated by the macro remains opaque.  I
envision an enhancement to Edebug such that the code generated by the
macro would get instrumented, and the appropriate bit in the macro
source would get displayed when stepping through the containing
function.

(ii) Edebugging font locking code.  It would be nice to be able to debug
font locking code which is being called from redisplay, as well as other
hooks which are also called from redisplay.  At the moment this isn't
possible.  To make it possible would require redisplay to become
reentrant, so that a frame or window in the inner redisplay call 
could be where debugging of the outer redisplay call happens.  I don't
know how practicable it would be to enhance redisplay for this (it is
certainly possible).  Has anybody ever looked into this before?

-- 
Alan Mackenzie (Nuremberg, Germany).