Francois Ostiguy <ostiguy@[...].gov>  writes:

>  This is a follow-up question to a recent thread.
>  Dave Abrahams provided the following code to extract a c++ object from a
>  PyObject
> 
>  void f(PyObject* p) {
> 
>    handle<> ph(borrowed(p));
>    MyObj* op = extract<MyObj*>(object(ph));
> 
>  }
> 
>  this works beautifully, but appenrently fails in the case where MyObj
>  is a simple function. That is
> 
> 
>  typedef void (fcntptr*)();
> 
>  void f(PyObject* p) {
> 
>    handle<> ph(borrowed(p));
>    fcntptr op = extract<fcntptr>(object(ph));
> 
>  }
> 
>  results in the following compilation error message.
> 
>  /usr/local/include/boost/type_traits/add_cv.hpp:34: `const volatile'
>  qualifiers cannot be applied to `void ()()'
> 
>  As always, any help/insight is greatly appreciated.

The compilation error occurs because Boost.Python isn't set up to
convert Python objects to function pointers.  It's not a crazy
idea to do so if, for example, you have a Python object which actually
contains a C++ function pointer in the first place, but that's not
implemented.  If you're trying to convert arbitrary Python functions
to C++ function pointers...

Can you figure out how to turn an arbitrary Python object into a C++
function pointer at runtime, using just the Python 'C' API?  If the
C++ function pointed to always does the same thing regardless of the
source Python object, you can... but that's not a very interesting
case.  If you want the C++ function to do something different based on
the Python function passed (e.g. call the Python object), where would
the code for that C++ function come from?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com


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