Re: [orbitcpp-list] Re: cpp branch: CORBA_Object struct hidden?

[Richard Andrews <bbmaj7 yahoo com au>]

> I can't think of any way of retaining this C <-> C++ compatibility
> if
> the CORBA_Object struct definition remains private and subject to
> change. But I'm certainly not a C++ expert by any stretch of the
> imagination.
> 
> So... thoughts, anyone?


More thinking aloud, if anyone still want to pursue this course...

If you did inherit CORBA::Object privately from CORBA_Object, then
the same piece of memory could be used for C and C++ objects.
You would have to have an overloaded operator new and delete for the
CORBA::Object which used the C allocator and deallocator for
CORBA_Object. 
It doesn't seem possible that a CORBA::Object could ever exist as a
concrete object on the stack since its size cannot be determined but
only pointers should ever exist to this type anyway. Allocation on
the heap through new should be sufficient and possible. 
The concrete types are X_var and X_ptr which hold pointers, so this
seems OK.

A narrow operation might operate like

CORBA::XXX_ptr 
CORBA::XXX_ptr::narrow( const CORBA::Object_ptr & rhs )
{
    // Note: rhs.internalPtr_ is a CORBA::Object *

    // a CORBA_Object * is the same as a CORBA::Object *
    CORBA_Object * rhsPtr 
        = reinterpret_cast<CORBA_Object *>( rhs.internalPtr_ );

    // do ORBit narrow on internal pointer
    CORBA_XXX * newObj = CORBA_XXX_narrow( rhsPtr, env );
     
    // check for exceptions and throw if a bad narrow

    // this should be OK since CORBA::XXX inherits from CORBA_XXX
    CORBA::XXX * internalPtr = static_cast<CORBA::XXX *>(newObj);

    // create new XXX_ptr which is now responsible for newObj
    return CORBA::XXX_ptr(internalPtr);
}

When the XXX_ptr deletes its internal pointer, the operator delete
for the XXX * will actually call the ORBit routine to deallocate
itself (because it is also a CORBA_XXX pointer).

(Disclaimer: I've come in half way through this discussion so I may
be missing some important point. Also I don't know the C binding.)

Or is this all just wrong?




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