Re: Rational Apex Ada - Pragma interface with C++

["Jeffrey Creem" <jeff@thecreems.com>]

Look for the view switch "NON_ADA_LINKAGE:"
Add the .o files from the c compile to this switch.
"John Smith" <someone@microsoft.com> wrote in message
news:H3zuq4.G8y@news.boeing.com...
> Hello Matthew,
>
> I just tried your suggestion, but I don't quite know how to link it.  I
> compiled the C++ module that contains the externs with the CC compiler
from
> Sun OS and compiled the C code that interfaces with the C++ module with
cc.
> Now my problem is how do I link both together?  I've generated two object
> files, but then I'm stuck.  Help please.
>
> John
>
>
> "Matthew Heaney" <mheaney@on2.com> wrote in message
> news:uqbtbu6rtkk7b@corp.supernews.com...
> >
> > "John Smith" <someone@microsoft.com> wrote in message
> > news:H3s05H.LMt@news.boeing.com...
> > > Does anyone know how to use pragma interface for interfacing C++
> functions
> > > to an Ada program.  I know how to do it with C, but can't seem to get
it
> > to
> > > work with C++.
> >
> > Interfacing with C++ requires care, especially if you have static
> variables
> > the require elaboration-time initialization.
> >
> > When a C++ program loads, all the statics get initialized.  There will
be
> > some code inserted by the compiler to go this, just prior to call the
C++
> > main.
> >
> > The same is true of an Ada program.
> >
> > In general, a C++ program will need a C++ main, and an Ada program will
> need
> > an Ada main.
> >
> > If you don't have any statics, you may OK.
> >
> > There's no official function you can call from an Ada program to perform
> the
> > C++ initialization -- you'll have to check your compiler docs.
> >
> > There are official functions to perform Ada initialization -- there are
> two
> > linker symbols called "adainit" and "adafinal".  If you have a C++ main,
> and
> > you're calling code written in Ada, then you'll need to call these.
> >
> > In any event, there's no pragma to interface with C++ directly.  I know
> GNAT
> > has compiler-specific pragmas to do this.
> >
> > However, I wouldn't bother.  Just create a C wrapper, and link to those.
> > For example, if you have a C++ class you want to use from Ada, like
this:
> >
> > class C
> > {
> > public:
> >    void f();
> > //...
> > };
> >
> > Assuming you don't mind manipulating a pointer, you can do this:
> >
> > extern "C" C* makeC()
> > {
> >    return new C;
> > }
> >
> > extern "C" void freeC(C* p)
> > {
> >    delete p;
> > }
> >
> > extern "C" void c_f(C* p)
> > {
> >    p->f();
> > }
> >
> > On the Ada side, create a set of bindings for each of the external
> functions
> > above, e.g.
> >
> > function Make_C return System.Address;
> > pragma Interface (C, Make_C);
> >
> > procedure Free_C (Object : System.Address);
> > pragma Interface (C, Free_C);
> >
> > procedure C_F (Object : System.Address);
> > pragma Interface (C, C_F);
> >
> > You could add more type safety than I've shown above, e.g.
> >
> > package C_Types is
> >
> >    type C_Type (<>) is limited private;
> >
> >    type C_Access is access all C_Type;
> >    pragma Convention (C, C_Access);
> >
> >    function New_C return C_Access;
> >
> >    procedure Free (C : in out C_Access);
> >
> >    procedure Do_F (C : access C_Type);
> >
> > private
> >
> >    type C_Type is null record;
> >
> >    function Make_C return C_Access;
> >    pragma Interface (C, Make_C);
> >
> >   --etc
> > end C_Types;
> >
> >
> >
> >
>
>