[orbitcpp-list] [ orbitcpp-Bugs-503269 ] generate skel code not legal C++

[<no...@so...>]

Bugs item #503269, was opened at 2002-01-14 03:01
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=100646&aid=503269&group_id=646

Category: None
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Richard Andrews (bbmaj7)
>Assigned to: Sam Couter (eddiesam)
Summary: generate skel code not legal C++

Initial Comment:

Let me present an example of what currently occurs.

This is a skel generated from the everything test

test_VariableLengthStruct * 
_skel_opVariable( ::PortableServer_Servant _servant,
const test_VariableLengthStruct * inArg,
test_VariableLengthStruct *inoutArg,
test_VariableLengthStruct **outArg, 
::CORBA_Environment *_ev) {
	::test::VariableLengthStruct *_retval = NULL;
	bool _results_valid = true;

	try {
		POA_test::StructServer * _self = ((_orbitcpp_Servant
*)_servant)->m_cppimpl;
		_retval = _self->opVariable( 
reinterpret_cast< const VariableLengthStruct&>(*inArg),
reinterpret_cast< VariableLengthStruct&>(*inoutArg),
reinterpret_cast< VariableLengthStruct*&>(*outArg) );
	}

I have removed namespace qualifications for clarity.

Now what happens here is that _self->opVariable expects
a Data_out<VariableLengthStruct> & (non-const ref) as
argument 3. Under C++ implied construction rules this
is no problem because Data_out<...> has a constructor
from VariableLengthStruct*&.

BUT... and here's the big problem.

This constructor creates a temporary object which is
passed as a reference through parameter 3, however only
const-references to temporaries may be passed in
standard C++ (as is now enforced in gcc3).

The only legal way to get around this problem is to
construct a wrapper object before the call, then pass
this as the non-const reference.

Eg.

try 
{ 
    POA_test::StructServer * _self =
((_orbitcpp_Servant *)_servant)->m_cppimpl; 

    Data_out< VariableLengthStruct> 
    wrapper3( reinterpret_cast<
VariableLengthStruct*&>(*outArg) );
    _retval = _self->opVariable( 
reinterpret_cast< const VariableLengthStruct&>(*inArg),
reinterpret_cast< VariableLengthStruct&>(*inoutArg), 
wrapper3); 

} 


In this case because wrapper3 is not a temporary it can
be passed through a non-const reference as is required
for argument 3 of opVariable().


In general the skeleton code for invoking operations
needs to be modified so that for each argument to the
servant implementation that is passed by non-const
reference, a temporary is constructed and passed.

I've been having a look at the code. The main areas of
interest are 

IDLPassSkels::doOperationSkel()

IDL_X_X_X_::getCPPSkelParameterTerm()

--

I put in a kludge in orbitcpp_smrtptr.hh about a year
ago using const_cast<>() to get around this problem but
it is no longer sufficient. The problem needs to be
fixed at the source which is the generated skel code.

I'm willing to put some time into fixing this if
someone familiar with this code can help me out.




----------------------------------------------------------------------

>Comment By: Sam Couter (eddiesam)
Date: 2002-01-21 03:43

Message:
Logged In: YES 
user_id=14486

Richard's supplied patch has been applied.

----------------------------------------------------------------------

You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=100646&aid=503269&group_id=646