gistfile1.rkt

#lang racket
(require ffi/unsafe
         ffi/unsafe/custodian)

(define n 0)

(define (foo)
  (define 100bytes (malloc 100 'raw))
  (define uid n)
  (set! n (add1 n))
  (register-custodian-shutdown 100bytes
                               (lambda (x)
                                 (log-error "hello there ~a" uid)
                                 (free x)))
  100bytes)

(let ((x (foo))
      (y (foo)))
  0)

(define bar (foo))