From: oleg@pobox.com

> Hmm, I have written code to test this interesting application. Alas,
> when I run it and was writing the captured continuation, I got a
> problem:
> 
> Fatal error: exception Invalid_argument("output_value: abstract value
> (Custom)")
> 
> I guess the marshalling function isn't happy about abstract values. I
> really don't know which particular value it is complaining about: the
> values used by the low-level C code are actually tuples and
> integers. But there are a lot of abstract values in the delimcc OCaml
> code, introduced to hide the representation.

The above message is a bit confusing. "abstract" here is unrelated to
typing and representation hiding, it just says that the marshaller
encountered a custom C value.  Note that, as it is custom, it might be
possible to define a custom marshaller for it.

Jacques Garrigue