[Caml-list] interfacing C++ with OCaml

[Caml-list] interfacing C++ with OCaml

[Thierry SALSET]

Hello list,

I used Camlidl to help me interface C functions and datatypes with OCaml
under Unix but now I would like to interface some existing (written by
others) C++ classes and methods with OCaml. I am not a C++ programmer
and I'm a little bit lost. Can Camlidl be of some help ? Should I write
a C layer between C++ and OCaml ?

Thanks in advance for your responses.


       Thierry Salset
       ENPC / CERMICS
       ts@cermics.enpc.fr
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Re: [Caml-list] interfacing C++ with OCaml

[Xavier Leroy]

> I used Camlidl to help me interface C functions and datatypes with OCaml
> under Unix but now I would like to interface some existing (written by
> others) C++ classes and methods with OCaml. I am not a C++ programmer
> and I'm a little bit lost. Can Camlidl be of some help ? Should I write
> a C layer between C++ and OCaml ?

This is a reasonable option.  Once you have a pure C API for the
C++ code, you can use CamlIDL as usual.  

CamlIDL itself doesn't have any kind of direct support for C++.  Well,
it supports COM interfaces, which correspond to a very small subset of
C++ classes, but I doubt this can help you, unless the C++ code of
interest is already structured as COM interfaces.

The other alternative is to hand-write Caml wrappers that call
directly the C++ code, without going through C.  I believe you can
write those wrappers in C++ if you're careful to declare the entry points
(the functions that Caml will call) "extern "C"".

Some of the features of C++ might be used to wrap the Caml runtime API (the
functions and macros provided by <caml/mlvalues.h>, etc) in a more
C++-friendly style, see e.g.
         http://caml.inria.fr/archives/199704/msg00029.html 

Bon courage...

- Xavier Leroy
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[Caml-list] Interfacing C with Ocaml

[Julius]

Hello,

I'am using ocamlidl to build an interface from custom C header but I have some 
problems (sorry if they are trivial)...

First, the following opaque structure definition doesn't pass the compilation 
stage (dereferencing pointer to incomplete type) :
typedef struct foo toto;
I thought this appens because C compiler doesn't know the size of foo 
structure. I tryed to define my own ml2c and c2ml functions (avoiding the 
problem by using pointers toto*) but I don't see how i can convert C pointer 
to Caml value...

Second, I have to give an IDL description of this awful thing...
typedef int (*foo_fun)(void*, int, char**, char**);
... and I really don't see how to do that.

Is anyone can help me? Thanks a lot :)

Julien Blond

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