[C++-sig] returning reference to enum

[Emmanuel Taurel]

Hello everybody,

 

I have a very simple example where I try to wrap a C++ class. In this class
there is a method which returns a reference to an internal variable which is
an enumeration. I try to wrap this method with the return_internal_reference
Call Policy but I have a compiler error.

 

First here is my little C++ file

 

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

 

#include <boost/python.hpp>

using namespace boost::python;

 

enum DispLevel

{

            OPERATOR = 0,

            EXPERT

};

 

class MyClass

{

public:

            MyClass() {}

            ~MyClass() {}

 

            void set_enum(DispLevel dl) {disp=dl;}

            DispLevel &get_enum() {return disp;}

 

protected:

            DispLevel disp;

};

 

BOOST_PYTHON_MODULE(PyTangoDs)

{

            enum_<DispLevel>("DispLevel")

            .value("OPERATOR",OPERATOR)

            .value("EXPERT",EXPERT)

            ;

                        

            class_<MyClass>("MyClass")

            .def("set_enum",&MyClass::set_enum)

 
.def("get_enum",&MyClass::get_enum,return_internal_reference<>())

            ;

}

 

The error I get from the compiler is : 

 

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

 

gcc-C++-action bin/enum/PyTangoDs.so/gcc/debug/shared-linkable-true/py_ds.o

/home/etaurel/src/boost_1_33_0/boost/python/object/make_instance.hpp: In
static

   member function `static PyObject*

   boost::python::objects::make_instance_impl<T, Holder,

   Derived>::execute(Arg&) [with Arg = DispLevel*, T = DispLevel, Holder =

   boost::python::objects::pointer_holder<DispLevel*, DispLevel>, Derived =

   boost::python::objects::make_ptr_instance<DispLevel,

   boost::python::objects::pointer_holder<DispLevel*, DispLevel> >]':

/home/etaurel/src/boost_1_33_0/boost/python/to_python_indirect.hpp:96:
instantiated from `static PyObject*
boost::python::detail::make_reference_holder::execute(T*) [with T =
DispLevel]'

/home/etaurel/src/boost_1_33_0/boost/python/to_python_indirect.hpp:60:
instantiated from `PyObject* boost::python::to_python_indirect<T,
MakeHolder>::execute(const U&, mpl_::bool_<false>) const [with U =
DispLevel, T = DispLevel&, MakeHolder =
boost::python::detail::make_reference_holder]'

/home/etaurel/src/boost_1_33_0/boost/python/to_python_indirect.hpp:37:
instantiated from `PyObject* boost::python::to_python_indirect<T,
MakeHolder>::operator()(const U&) const [with U = DispLevel, T = DispLevel&,
MakeHolder = boost::python::detail::make_reference_holder]'

/home/etaurel/src/boost_1_33_0/boost/python/detail/invoke.hpp:88:
instantiated from `PyObject*
boost::python::detail::invoke(boost::python::detail::invoke_tag_<false,
true>, const RC&, F&, TC&) [with RC =
boost::python::to_python_indirect<DispLevel&,
boost::python::detail::make_reference_holder>, F = DispLevel&(MyClass::*)(),
TC = boost::python::arg_from_python<MyClass&>]'

/home/etaurel/src/boost_1_33_0/boost/python/detail/caller.hpp:199:
instantiated from `PyObject* boost::python::detail::caller_arity<1>::impl<F,
Policies, Sig>::operator()(PyObject*, PyObject*) [with F =
DispLevel&(MyClass::*)(), Policies =
boost::python::return_internal_reference<1,
boost::python::default_call_policies>, Sig = boost::mpl::vector2<DispLevel&,
MyClass&>]'

/home/etaurel/src/boost_1_33_0/boost/python/object/py_function.hpp:38:
instantiated from `PyObject*
boost::python::objects::caller_py_function_impl<Caller>::operator()(PyObject
*, PyObject*) [with Caller =
boost::python::detail::caller<DispLevel&(MyClass::*)(),
boost::python::return_internal_reference<1,
boost::python::default_call_policies>, boost::mpl::vector2<DispLevel&,
MyClass&> >]'

/home/etaurel/src/boost_1_33_0/boost/detail/call_traits.hpp:83:
instantiated from here

/home/etaurel/src/boost_1_33_0/boost/python/object/make_instance.hpp:24:
error: incomplete

   type `boost::STATIC_ASSERTION_FAILURE<false>' does not have member
`value'

 

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

 

Any idea welcome. Thank's very much in advance

 

Emmanuel Taurel (etaurel at cells.es)

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