[Caml-list] Link with C++ code

[Caml-list] Link with C++ code

[Christophe TROESTLER]

Hi all,

I am trying to use some C++ code from OCaml.  I am completely
inexperienced at this (and not knowing well C++ to make matters worse)
but in view of http://caml.inria.fr/Hump/msg778-782 that didn't seem
so difficult.  I will likely have more questions later but I am
already stuck at the beginning.  Indeed, the C++ code includes the
file "stl_alloc.h" which contains (gnu version, line 451)

typedef __default_alloc_template<__NODE_ALLOCATOR_THREADS, 0> alloc;

and so conflicts with the definition of "alloc" in
"/usr/include/caml/alloc.h".

What can I do ?

ChriS



---
P.S.  For those who wonder, this attempt arises from a need to do
symbolic computation on multi-variable polynomials (with symbolic
coefficients).  First I thought to implement this directly in Caml
but, when I saw http://www.ginac.de/ I realized it is more useful to
try to use it from OCaml since I will never have time to do 1/10th of
what they already accomplished...  BTW, if you know other good algebra
packages that fit my need, feel free to let me know...
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Re: [Caml-list] Link with C++ code

[Clemens Hintze]

On Tue, Nov 20, 2001 at 11:41:49PM +0100, Christophe TROESTLER wrote:
> Hi all,

Hi you,

> I am trying to use some C++ code from OCaml.  I am completely
> inexperienced at this (and not knowing well C++ to make matters worse)
> but in view of http://caml.inria.fr/Hump/msg778-782 that didn't seem
> so difficult.  I will likely have more questions later but I am
> already stuck at the beginning.  Indeed, the C++ code includes the
> file "stl_alloc.h" which contains (gnu version, line 451)

does this mean, *you* are including "stl_alloc.h" directly? This you
should not do. You should not include any "stl_XXX.h" file. If you did
not please forgive me.

What you can do depends a bit on the version of the compiler you use
right now. The closest-to-standard G++ should be the 3.x chain of GCC.
Here all symbols of the STL are located in namespace 'std'. If your
code do *not*

  using namespace std;

you should not have problems then. Only, your code has to write
std::whatever in front of every STL datatype you use.

Other versions of GCC are not that close to the standard. They will
simply obey and ignore the 'std' identifier the same time :-(

> What can I do ?

You could try to wrap the OCaml stuff into a namespace, propably.
Like this:

  namespace ocaml {
    extern "C" {
  #   include <caml/alloc.h>
    }
  }

  int main(int argc, char* argv[])
  {
    :
    m = ocaml::alloc(...);
    :
  }


HTH,
Clemens.

PS: Perhaps the OCaml headers could take sorrow on their own to wrap
    appropiate if included by an C++ compiler? Like this:

    #ifdef __cplusplus
    namespace OCaml {                /* (1) */
    extern "C" {
    #endif
    
    /* Normal header file contents goes here */

    #ifdef __cplusplus
    } /* end of extern "C" */
    } /* end of namespace OCaml */   /* (1) */
    #endif

    Perhaps a bit more adaption would necessary if using lines (1)?  
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