linking to C++

linking to C++

[Anthony Moss]

Is there any good documentation on calling C++ functions from a piece of ADA
code.
please repond
anthony.moss@baesystems.com

Thank you.

Re: linking to C++

[Larry Kilgallen]

In article <3eddb5dd$1@baen1673807.greenlnk.net>, "Anthony Moss" <a.m@baesystems.com> writes:

> Is there any good documentation on calling C++ functions from a piece of ADA
> code.

It is not part of the Ada standard, so the answer will be specific to
the operating system and compiler you are using.

If looking at your compiler documentation does not help, you could
reveal information about your environment here to get advice.

Re: linking to C++

[Matthew Heaney]

"Anthony Moss" <a.m@baesystems.com> wrote in message news:<3eddb5dd$1@baen1673807.greenlnk.net>...
> Is there any good documentation on calling C++ functions from a piece of ADA
> code.
> please repond
> anthony.moss@baesystems.com
> 
> Thank you.

I posted an answer to a similar question in the thread "Rational Apex
Ada - Pragma interface with C++", which occured in Oct 2002.

<http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&selm=uqbtbu6rtkk7b%40corp.supernews.com>

I got the idea from James Coplien's book Adanced C++ Programming
Styles and Idioms.  The basic idea is to bind to a factory function
written in C++, and then manipulate the object from the Ada side, e.g.

class X
{
public:
   void f();
};

extern "C" X* make_x()
{
   return new (std::nothrow) X();
}

extern "C" void free_x(X* p)
{
   delete p;
}

extern "C" void X_f(X* x)
{
   x->f();
}

You'll need to write a binding on the Ada side, e.g.

package X_Types is

   type X (<>) is limited private;

   type X_Access is access all X;
   pragma Convention (C, X_Access);
   for X_Access'Storage_Size use 0;

   function New_X return X_Access;

   procedure Free (X : in out X_Access);

   procedure F (X : X_Access);
   --or procedure F (X : access X);

private

   type X is limited null record;

end X_Types;

Implement New_X, Free, and F by calling the C++ functions, which have
been imported to the Ada program:

package body X_Types is

   function C_New_X return X_Access;
   pragma Convention (C, C_New_X);
   pragma Import (C_New_X, "new_x");  //something like that

   function New_X return X_Access is
   begin
      return C_New_X;
   end;

   ...
end X_Types;

Make sure that access types are passed by *value* to the C++ function.