[gme-users] Question regarding BON extender interpreter and "getReferred()"

Matthew J. Emerson mjemerson at isis.vanderbilt.edu
Mon Sep 5 11:49:19 CDT 2005

I made a small example to test out Ace's exact problem. It doesn't
really have to do with the inheritance hierarchy he described -- it has
to do with the fact that the reference has multiple referent types.

In my example, Reference1 can refer to three different types: Model1,
Model2, or Model3. In this case, the BON Extender generates a single a
referent getter method which could return objects of any of the three
types. The offending generated code is:

//BON Extender-generated header file
class Reference1Impl :
        virtual public BON::ReferenceImpl

      // ref getters
      virtual BON::Model  getReferred();

      // add your own members here

//BON Extender-generated source file
BON::Model Reference1Impl::getReferred()
      BON::FCO r = getReferred(); //Infinite recursion
      return BON::Model(r);

To avoid infinite recursion, the generated source code should have been:

//BON Extender-generated source file
BON::Model Reference1Impl::getReferred()
      BON::FCO r = BON::ReferenceImpl::getReferred();
      return BON::Model(r);

I think this is a bug in the BON Extender. Zoli, if you want my example
let me know.


> -----Original Message-----
> From: gme-users-bounces at list.isis.vanderbilt.edu [mailto:gme-users-
> bounces at list.isis.vanderbilt.edu] On Behalf Of Thompson, Robert C
> Sent: Saturday, September 03, 2005 11:55 PM
> To: gme-users
> Subject: [gme-users] Question regarding BON extender interpreter and
> "getReferred()"
> Hi,
> I have a question regarding BON extender interpreter-generated code
> the method "getReferred()".  This is with GME 4.11.10.
> In my metamodel I have a class "A" and a class that references it
> RA also inherits from two other classes "B" and "C".  In the
> extender-interpreter generated code, I get something like the
> class RAImpl : virtual public BON::ReferenceImpl, public BImpl, public
> CImpl {
> ...
> public:
> 	virtual BON::Model getReferred();
> ...
> }
> Later, in a plugin, if I have an instance named "r" of RA (not
> I tried this:
> BON::Model m = r->getReferred();
> When I do this, I get an instant death to my GME sesssion, no warning
> message, just "poof".
> So, I tried this:
> BON::Model m = (dynamic_cast<BON::ReferenceImpl*>(r.operator->()))
> ->getReferred();
> This gives me the desired behavior.  So basically I have to cast "r"
> BON::ReferenceImpl so that I use BON::ReferenceImpl::getReferred
> of RAImpl's version.
> Am I missing something?  I had expected that the RAImpl::getReferred()
> (i.e. the one exposed on the extender-interpreter-generated interface)
> would give me what I wanted...  A wild guess makes me think it's
> something with the virtual inheritance of BON::ReferenceImpl and the
> virtual-ness of RAImpl::getReferred()... because the body of
> RA::getReferred() invokes "getReferred()". But I don't really know for
> sure that this is causing my problem.
> Any help or pointers would be much appreciated.  It can be worked
> but I'm confused as to what is the expected meaning/behavior of the
> method that seems to be causing me trouble.
> Thanks
> -ace
> Ace Thompson
> Systems and Software Engineer
> FCS LSI C4ISR Battle Command
> robert.c.thompson3 at boeing.com
> +1 480 891 2284
> The Boeing Company
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