(foreign-declare #<<EOF
#include <unistd.h>
#ifndef _XOPEN_CRYPT
#include <crypt.h>
#endif
EOF
)

;; There's no such thing as a native gensalt, by the way.
;; There is pw_gensalt() and such, but those are nonstandard and often not
;; properly documented, and have an awkward "API".  Yay for POSIX -_-
(define (crypt-native password setting)
  ((foreign-lambda c-string "crypt" c-string c-string) password setting))