;; foo.scm
(define (foo) (print "foo"))
(define-syntax foo-macro
  (ir-macro-transformer
   (lambda (e i c)
     (print "foo macro"))))

;; bar.scm
(foo)
(foo-macro)

;; Output
$ csc -compile-syntax -unit foo foo.scm -c
$ csc -uses foo bar.scm foo.o
$ ./bar
foo

Error: unbound variable: foo-macro