[QUESTION] How to expose pointer member with boost::python behavior

Hello!
I am migrating from boost::python to pybind11 and have just faced some pointer member behavior issue:

class SomeClass
{
};
struct SomeStruct
{
public:
    SomeClass* scPtr;
};

void foo( SomeStruct& str )
{
    if ( str.scPtr )
        *str.scPtr;
}

// pybind11 version
PYBIND11_MODULE( mod, m )
{
    pybind11::class_<SomeClass>( m, "SomeClass" ).def( pybind11::init<>() );
    pybind11::class_<SomeStruct>( m, "SomeStruct" ).def( pybind11::init<>() ).
        def_readwrite( "scPtr", &SomeStruct::scPtr);
    m.def( "foo", &foo );
}

// boost python version
BOOST_PYTHON_MODULE( mod )
{
    boost::python::class_<SomeClass>( "SomeClass" );
    boost::python::class_<SomeStruct>( "SomeStruct" ).
        add_property( "scPtr", 
            boost::python::make_getter( &SomeStruct::scPtr, boost::python::return_value_policy<boost::python::reference_existing_object>() ),
            boost::python::make_setter( &SomeStruct::scPtr, boost::python::return_value_policy<boost::python::reference_existing_object>() ) );
    boost::python::def( "foo", &foo );
}

Python behavior

import mod
#boost version
stru = mod.SomeStruct()
stru.scPtr = mod.SomeClass()
mod.foo(stru) #works ok, but in pybind this will cause access violation (as far as scPtr will be spoiled)

#pybind version
stru = mod.SomeStruct()
sc = mod.SomeClass()
stru.scPtr = sc
mod.foo(stru) #works ok

So can I make pybind11 work as boost python?

Start by reproducing the access violation using the shown pybind11 module with SomeClass, SomeStruct::scPtr, and foo, then compare it with the Boost.Python add_property binding. Check the pybind11 class_ and def_readwrite behavior for pointer members; done means establishing whether equivalent lifetime behavior is supported and documenting the required binding approach.