# Module Callback

    module Callback: sig .. end

Registering OCaml values with the C runtime.

This module allows OCaml values to be registered with the C runtime under a symbolic name, so that C code can later call back registered OCaml functions, or raise registered OCaml exceptions.

    val register : string -> 'a -> unit

`Callback.register n v` registers the value `v` under the name `n`. C code can later retrieve a handle to `v` by calling `caml_named_value(n)`.

    val register_exception : string -> exn -> unit

`Callback.register_exception n exn` registers the exception contained in the exception value `exn` under the name `n`. C code can later retrieve a handle to the exception by calling `caml_named_value(n)`. The exception value thus obtained is suitable for passing as first argument to `raise_constant` or `raise_with_arg`.