[omniORB] Reference passing

Thu Aug 8 13:57:01 2002

You do need to duplicate the reference.  A _ptr type does not have
ownership semantics, as it is likely just a raw pointer.  Some reference
counting schemes start an object with a zero count and any time a new
handle attaches, the ref-count is incremented (in the assignment operator).
The CORBA scheme starts a reference count at one and the application is
responsible for incrementing it (via a _duplicate() call).  The _var types
do not increment the count when they are assigned a _ptr instance.  However
if one _var is assigned another _var, then the ref count does get
incremented for you.

So when starting with a _ptr, do the duplicate yourself, but if you copy a
_var, then don't.  I think your code should read

void BarrierSrv_i::registerInBarrierServer( OrbiMan_ptr newManager){

  orbiMan_var = OrbiMan::_duplicate(newManager);

}

The call of _duplicate through the _var instance probably works, but the
above is the correct way, since _duplicate is a static method.

Kendall

                    Jacek Nowak                                                                                          
                    <jnowak@ernie.icslab.a       To:     <omniorb-list@realvnc.com>                                      
                    gh.edu.pl>                   cc:                                                                     
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                    omniorb-list-admin@rea       Subject:     [omniORB] Reference passing                                
                    lvnc.com                                                                                             

                    08/08/2002 05:22 AM                                                                                  

I have the following problem:

I pass a _ptr reference to an object as an 'in' parameter of a function
and try keep a copy of it in a _var. Something like this:

void BarrierSrv_i::registerInBarrierServer( OrbiMan_ptr newManager){

  orbiMan_var = newManager_ptr;
  //orbiMan_var->_duplicate( orbiMan_var );

}

If I don't call _duplicate explicitly the reference gets deleted when
leaving the function, and the next attemp to use the _var reference causes
segmentation fault.

void BarrierSrv_i::test( ){
  orbiMan_var->ping(); // <- Segmentation fault
}

Is this correct behavior? I mean, do I have to call _duplicate explicitly?
I always thought _duplicate is called when the _var takes over ownership
from the _ptr.

Thanks,
Jacek

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