/usr/share/racket/collects/ffi/winapi.rkt is in racket-common 6.3-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 | #lang racket/base
(provide win64? winapi)
(define win64? 
  (and (eq? 'windows (system-type))
       (equal? "win32\\x86_64" (path->string (system-library-subpath #f)))))
(define winapi (if (or win64?
                       (not (eq? 'windows (system-type))))
                   'default
                   'stdcall))
 |