[C++-sig] Re: Making copy of function derived from C++ pure virtual function

[Paul F. Kunz]

>>>>> On Fri, 10 Dec 2004 07:38:12 -0800, "Paul F. Kunz" <Paul_Kunz at slac.stanford.edu> said:

>>>>> On Thu, 09 Dec 2004 20:37:18 -0500, David Abrahams <dave at boost-consulting.com> said:
>> Sorry, this should be:

>> class_<FunctionWrap, std::auto_ptr<FunctionWrap> >( "FunctionBase",
>> init<FunctionBase const&>())

> Ok, that compiles.  Obvious no that I see it.

> But now at run time I get...

   Replying to my own item, I got pass the runtime error by doing the
following instead of the above...

      class_ < FunctionBase, std::auto_ptr< FunctionWrap> >
		( "FunctionBase" )

with the constructor of the class as ...

FunctionWrap::
FunctionWrap ( PyObject * self )
  : FunctionBase (),
    m_self ( self )
{
}

`m_self' is data member to hold the PyObject.

   Now at runtime I crash in the suggested FunctionWrap::clone()
method when trying to call get_ower().   With gdb I see ...

  <boost::python::wrapper<FunctionBase>> = {
    <boost::python::detail::wrapper_base> = {
      m_self = 0x0
    }, <No data fields>}, 
  members of FunctionWrap: 
  m_self = 0x4060911c, 
  invert_ownership = {
    <boost::python::api::object_base> = {
      <boost::python::api::object_operators<boost::python::api::object>> = {
        <boost::python::def_visitor<boost::python::api::object>> = {<No data fields>}, <No data fields>}, 
      members of boost::python::api::object_base: 
      m_ptr = 0x8125d60
    }, <No data fields>}
}
(gdb) 

Note that the wrapper_base data member `m_self' is a null pointer.
So I guess my FunctionWrap class ...

class FunctionWrap : public FunctionBase,
		     public boost::python::wrapper < FunctionBase >
{

didn't get initialized properly.   Looking at the wrapper.hpp and
detail/wrapper_base.hpp files, I don't see how to initialize it.

Do I really need it?   If get_owner had worked, would it have returned
FunctionWrap::m_self?