Re: Help interfacing Ada and C++

[rou271@prb.net]

In article <33A28715.1558@codenet.net>,
  Charlie Gage <cgage@codenet.net> wrote:
>
> Greetings,
> I have a need to interface Ada95 (specifically Gnat) with C++ (SPARC),
> and am having some difficulty with it.  I have read all the Gnat docs
> and everything seems to work OK, except when I #include <iostream.h>
> in the C++ code and try to use anything like "cout".  The Gnat linker
> complains about an undefined symbol.  If I #include <stdio.h> and use
> printf, everything works OK.  Now, however I need to use cout and
> other things in the iostream.h and fstream.h.  I have used the
> "with Interfaces.CPP" in the Ada code, but it does not seem to make
> a difference.  Are there any other libraries that I need to include
> when linking with Gnat?  Any help with this, or a pointer to more
> information would be greatly appreciated.
>
> Thanks,
> Charlie Gage
> Email: cgage@codenet.net  or  charles.gage@lmco.com

I'm not sure which way you are calling things - Ada from C++ or C++ from
Ada, but here is an example  of each using Visual C++ and ObjectAda: C++
calling Ada95 - test_int.ads : with interfaces.c;

package test_int is
    procedure get_day(day: in out interfaces.c.int);
    pragma export (cpp, get_day, "get_day", "_get_day");
end test_int;



test_int.adb:
package body test_int is
  procedure get_day(day: in out interfaces.c.int) is
    today_ada : interfaces.c.int:=interfaces.c.int(1);
  begin
    day := today_ada;
  end get_day;
end test_int;


test_int.cpp:
#include <iostream.h>
  extern "C" void get_day ( int *);
void main(){
  int today = 4;
  cout << "C sez today is " << today << endl;
  get_day(&today);

  // If "<< endl;" is put on the end of this statement, it prints
  // address of endl?!
  cout << "Ada sez today is " << today;
  cout << endl;
}



Ada95 calling C++ -
import_p.ads :  ( Here is the mangled name I got from the C object.)
with Interfaces.C; use Interfaces.C;

package import_pkg is
   procedure import(num : in Int);

  pragma Import (Cpp, import, external_name =>
"?imported_function@@YAXH@Z"); end import_pkg;


useimpor.adb :
with import_pkg;
with text_io; use text_io;
procedure Use_Of_Import is
begin
   import_pkg.import(5);
end Use_Of_Import;


imporfn.cpp
#include <iostream.h>
void imported_function (int n)
{
	cout << " I am now in the imported function " << n << endl;
}

I did not have to link with anything special to use cout. I don't know if
this helps since you are using different compilers.  I did use this with
gnat calling Visual C++ also.

      Betty

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