(define-library (foo)

(export bar)

(import (except scheme
                string-length string-ref string-set! make-string string substring
                string->list list->string string-fill! write-char read-char display)
        utf8)

(begin
  (define (bar x)
    (string-length x))))

$ csc -verbose -c foo.scm 
'/usr/local/bin/chicken' 'foo.scm' -output-file 'foo.c' -verbose

Note: re-importing already imported identifier: string-length

Note: re-importing already imported identifier: string-ref

Note: re-importing already imported identifier: string-set!

Note: re-importing already imported identifier: make-string

Note: re-importing already imported identifier: string

Note: re-importing already imported identifier: substring

Note: re-importing already imported identifier: string->list

Note: re-importing already imported identifier: list->string

Note: re-importing already imported identifier: string-fill!

Note: re-importing already imported identifier: write-char

Note: re-importing already imported identifier: read-char

Note: re-importing already imported identifier: display

Note: re-importing already imported identifier: print

Note: re-importing already imported identifier: print*
'gcc' 'foo.c' -o 'foo.o' -c  -fno-strict-aliasing -fwrapv -DHAVE_CHICKEN_CONFIG_H -DC_ENABLE_PTABLES -Os -fomit-frame-pointer -I/usr/local/include/chicken
rm foo.c