Re: [pygccxml-development] Function adaptors‏‏

[Roman Y. <rom...@gm...>]

2009/8/19 Berserker <ber...@ho...>:
>> > the problem is related to protected_virtual
>> > method where Py++
>> > only generates Foo_wrapper::protected_virtual code (why?).
>>
>> I don't remember. I think there were serious problems in that area.
>> After all, it is impossible to access protected functions out side of
>> the class and this is the main problem.
>
> Not with wrapper class, right?
> This is the "problematic" code (actually) generated from Py++
>
>> ::boost::python::class_< Foo_wrapper, ::boost::noncopyable >( "Foo",
>> ::boost::python::init< >() )
>>         .def(
>>             "public_virtual"
>>             , (void ( ::Foo::* )(  ) )(&::Foo::public_virtual)
>>             , (void ( Foo_wrapper::* )(  )
>> )(&Foo_wrapper::default_public_virtual) )
>>         .def(
>>             "protected_virtual"
>>             , (void ( Foo_wrapper::* )(  )
>> )(&Foo_wrapper::protected_virtual) )    );
>
> I manually added the "Foo_wrapper::default_protected_virtual"
> like "Foo_wrapper::default_public_virtual":
>
>> void Foo_wrapper::default_protected_virtual(  )
>> {
>>    // my custom code...
>>    ::Foo::protected_virtual( );
>> }
>
> and I changed the previous code in this way:
>
>> ::boost::python::class_< Foo_wrapper, ::boost::noncopyable >( "Foo",
>> ::boost::python::init< >() )
>>         .def(
>>             "public_virtual"
>>             , (void ( ::Foo::* )(  ) )(&::Foo::public_virtual)
>>             , (void ( Foo_wrapper::* )(  )
>> )(&Foo_wrapper::default_public_virtual) )
>>         .def(
>>             "protected_virtual"
>>             , (void ( ::Foo::* )(  ) )(&::Foo_wrapper::protected_virtual)
>>             , (void ( Foo_wrapper::* )(  )
>> )(&Foo_wrapper::default_protected_virtual) )    );
>
> The only "hack" is the bad cast in the line "(void ( ::Foo::* )(  )
> )(&::Foo_wrapper::protected_virtual)"
> but I tested the code from Python to C++ and from C++ to Python and now it
> works as I expected!

I am pretty sure this is illegal. Today, Py++ generates valid code for
wide range of compilers and os. I think this change will break some of
them.

> I absolutely need to call a "base virtual protected method" in Python, what
> about this solution? Plz
> this is my "last" obstacle and I really don't know how to change the python
> scripts...

Sorry, I don't want such hacks in Py++. I believe that the generated
code quality should be very very high, otherwise people will not trust
the code and will not use Py++. I am not going to change this policy.

As an alternative I propose you to use other Py++ feature:

http://language-binding.net/pyplusplus/documentation/inserting_code.html

Replace code generated by Py++ with your own one.

>> > In the case of a C++ to Python calls, I would need, as usual, to restore
>> > the
>> > right PyThreadState
>> > before calling any CPython API (PyErr_SetString in the above's code),
>> > but I
>> > have no options here to customize
>> > "pure_virtual_called". Probably I'll ovverride in Py++ the identifier
>> > "::boost::python::pure_virtual" with a
>> > custom one, but I still need to think/work on this (I love the
>> > "override"
>> > feature in Py++ :) ).
>>
>> This one is fixed. I will commit the code soon.
>
> Sorry but I didn't understand well what was fixed here.

I attached the generated file - please take a look on it. I hope it
will clarify my answer.

> My idea (not yet tested) for this problem doesn't involve any change in
> Py++,

Please test your ideas :-)

> here is a short description of it:
> - Disable the ::boost::python::pure_virtual exposition overriding the
> identifier with ""
> - Create a custom class based on "::boost::python::override" which holds a
> reference to
>   PyThreadState and don't release it in the case of a pure virtual function
> call (which
>   raises an exception)

Without changing\replacing some internal code you will not be able to
do this :-(.


-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/