fun run (f: unit -> unit) =
   case Posix.Process.fork () of
      SOME pid =>
         let
            open Posix.Process
            val (pid', status) = waitpid (W_CHILD pid, [])
         in if pid = pid' andalso status = W_EXITED
               then ()
            else raise Fail "child failed"
         end
    | NONE => let open OS.Process
              in exit ((f (); success) handle _ => failure)
              end

fun succeed () =
   let open OS.Process
   in exit success
   end

open MLton.World MLton.Signal Posix.Signal Posix.Process Posix.ProcEnv

val (w, out) = MLton.TextIO.mkstemp "/tmp/world"
val _ = TextIO.closeOut out

val childReady = ref false

fun print s = TextIO.output (TextIO.stdErr, s)

val _ = setHandler (usr1, Handler.simple (fn () => childReady := true))
   
val parent = getpid ()

val _ =
   case fork () of
      NONE =>
         let
            val canExit = ref false
         in
            setHandler (usr1, Handler.handler (fn t => (canExit := true
                                                        ; saveThread (w, t)
                                                        ; t)))
            ; kill (K_PROC parent, usr1)
            ; let
                 fun loop () = if !canExit then print "success\n" else loop ()
              in
                 loop ()
              end
            ; let open OS.Process
              in exit success
              end
         end
    | SOME child =>
         let
            fun loop () = if !childReady then () else loop ()
         in
            loop ()
            ; kill (K_PROC child, usr1)
            ; wait ()
            ; run (fn () => load w)
            ; OS.FileSys.remove w
         end