[Cython] non-virtual methods

[Vitja Makarov]

2011/8/25 Vitja Makarov <vitja.makarov at gmail.com>:
> 2011/8/25 Vitja Makarov <vitja.makarov at gmail.com>:
>> 2011/8/25 Stefan Behnel <stefan_ml at behnel.de>:
>>> Vitja Makarov, 25.08.2011 20:32:
>>>>
>>>> 2011/8/25 Stefan Behnel<stefan_ml at behnel.de>:
>>>>>
>>>>> Vitja Makarov, 25.08.2011 18:11:
>>>>>>
>>>>>> 2011/8/24 Stefan Behnel:
>>>>>>>
>>>>>>> Vitja Makarov, 24.08.2011 21:17:
>>>>>>>>
>>>>>>>> I tried final classes:
>>>>>>>> 2. In this example foo call is done through virtual table
>>>>>>>>
>>>>>>>> cimport cython
>>>>>>>>
>>>>>>>> @cython.final
>>>>>>>> cdef class Foo:
>>>>>>>>     cdef foo(self):
>>>>>>>>         print 'haha'
>>>>>>>>
>>>>>>>> def test():
>>>>>>>>     cdef Foo a = Foo()
>>>>>>>>     a.foo()
>>>>>>>>
>>>>>>>>   __pyx_t_1 = ((struct __pyx_vtabstruct_3yyy_Foo
>>>>>>>> *)__pyx_v_a->__pyx_vtab)->foo(__pyx_v_a); if (unlikely(!__pyx_t_1))
>>>>>>>> {__pyx_filename = __pyx_f[0]; __pyx_lineno = 12; __pyx_clineno =
>>>>>>>> __LINE__; goto __pyx_L1_error;}
>>>>>>>
>>>>>>> Right, this is not implemented yet. Feel free to do so. Also see
>>>>>>>
>>>>>>> http://trac.cython.org/cython_trac/ticket/474
>>>>>>>
>>>>>>>
>>>>>>>> 3. I can't use final decorator for methods (error reported)
>>>>>>>
>>>>>>> http://trac.cython.org/cython_trac/ticket/586
>>>>>>
>>>>>> What is the prefered syntax keyword inline or final decorator?
>>>>>
>>>>> "final" is the right option here.
>>>>>
>>>>> They are orthogonal concepts. Only because you declare a method "final"
>>>>> does
>>>>> not mean you want to inline it, and just because you declare it "inline"
>>>>> does not (necessarily) mean that you cannot override it. Admittedly, the
>>>>> semantics of an overridable inline method may turn out to be somewhat
>>>>> obscure and error prone, so I think it's a good idea to let "inline"
>>>>> imply
>>>>> "final". But not the other way round.
>>>>
>>>> But both inline and final methods should bypass vtab, right?
>>>
>>> Yes. But in the "final" case, it's always clear which method implementation
>>> to use - it's not overridable, so there is only one choice. In the "inline"
>>> case, it could still be overridable and we may have a subtype of the
>>> declared type in our hands at runtime, thus choosing the wrong method at
>>> compile time. That's why only the "final" case is safe.
>>>
>>> Note that I'm only talking about the semantics of the qualifier themselves
>>> here. If we allow "inline" methods, I think we should force them to be
>>> "final" as well. But that's a practical choice, not a semantic implication.
>>>
>>>
>>>> Also I'm not sure about C inline qualifier here.
>>>
>>> That's what "inline" requests.
>>>
>>>
>>>> I see three options:
>>>>
>>>>  - non-virtual: bypass vtab
>>>>  - final: non-virtual, non-overridable
>>>
>>> How would you want to bypass the vtable in the "non-virtual" case if the
>>> method is overridable?
>>>
>>>
>>>>  - inline: non-virtual, C inline qualifier is used
>>>
>>> Correct.
>>>
>>
>> Ok.
>>
>> I think it's better to implement final method then user could choose
>> to use inline qualifier or not.
>>
>
> I tried it here:
> https://github.com/vitek/cython/commit/ddf80a80dc75aced2cd92dc32afa77a7bcf2de02
>
> There is one problem: vtab bypassing should be enabled if final method
> is defined in the same module.
> I don't know how to check that final method comes from cimport (it's
> okay with pxd, the problem is pyx)
>


https://github.com/vitek/cython/commit/6e91fc257a683018ba6be340d384f9a7c34ef425

Here is update version. I've add tree asserts and final method's prototypes.

-- 
vitja.