log!.lisp

(defvar *logs* (make-hash-table :test #'equal))
(defmacro log! (&rest names)
  (if (null names)
    `(progn (maphash (lambda (name function)
                       (setf (fdefinition name) function))
                     *logs*)
            (clrhash *logs*))
    `(map nil (lambda (name)
                (if (gethash name *logs*)
                  (warn "Already logging: ~S" name)
                  (let ((function (fdefinition name)))
                    (setf (gethash name *logs*) function
                          (fdefinition name)
                          (lambda (&rest args)
                            (format *trace-output* "~%Start: ~S" name)
                            (unwind-protect (apply function args)
                              (format *trace-output* "~%End: ~S" name)))))))
          ',names)))