> Reading the documentation of camlidl, it says that caml objects can
> be exported for use in C/C++ programs.  Looking at the source code,
> the support for this looks minimal.  I see the camlidldll script,
> which is just a shell script that links a caml program with some
> executable code.

This is just a convenience script.  The gist of CamlIDL is that it
generates stub code + a Caml interface from a C-like interface
expressed in IDL (basically, it's a C include file with annotations).
This provides Caml/C (and a little C++) interoperability in situations
where the C interface is fixed.  But that's not what you want:

> I want real C header files from just plain unannotated mli.
> Preferably a system with ability to map variants into C
> struct/unions coupled with utility functions.  I'm not sure which
> other advanced ocaml datatypes I need beyond variants and the basic
> ints, strings, arrays and etc.

What you need is Camouflage by Robbert van Renesse:
        ftp://ftp.cs.cornell.edu/pub/rvr/camou-1.1.tar.gz
>From the announcement:

  Camouflage 1.1 is a tool that supports interfacing between C and OCaml.
  Camouflage reads a .mli file and creates the necessary C interfaces to
  the given module.  This way the fact that a library is written in OCaml
  can be ``camouflaged.''  Camouflage also supports creating OCaml interfaces
  to C functions, and generates functions that convert between OCaml and C
  data structures.

  For example, let say "x.mli" contains the declaration "val add: int ->
  int -> int".  Then the command "camou x.mli" creates a file "x.c" that
  contains the C function "int X_add(int, int)" which does all the stuff
  necessary to invoke the ML function.  Vice versa, the declaration
  "external add: int -> int -> int" creates an ML function to invoke
  a corresponding C function.

> While I'm at it, I will probably try to export stubs at least these
> styles: COM, GTK-style C objects, and SWIG-ready header files for
> inclusion in Python or TCL or whatever some unenlightened person
> would want to use.

Sounds good.  I don't think Camouflage does any of this, and it hasn't
been updated in a while, but I think it could be a good starting
point.

- Xavier Leroy
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