[C++-sig] BPL and Py_Clear()

[David Abrahams]

"Niall Douglas" <s_sourceforge at nedprod.com> writes:

> On 12 Jun 2005 at 12:05, David Abrahams wrote:
>
>> >> The former is easy: make sure the object is held by auto_ptr<T>,
>> >> and pass the object to a function accepting an auto_ptr<T>.
>> >
>> > The latter could probably be made to work if given enough time, but
>> > it would require a substantial amount of alterations to pyste to
>> > achieve it - and even then, I still can see issues which may arise.
>> >
>> > Hence I must go the quick & dirty route. I was thinking of throwing
>> > a dummy exception, reading the traceback & stack frame info and
>> > recursing up through the globals() in each deleting any references
>> > to my object. This would surely do it for the current interpreter at
>> > least?
>> 
>> No, there may be references hiding in other pythong objects and, for
>> that matter, in extension modules.
>> 
>> I don't see what advantage you gain from it either.  A variable or
>> attribute in Python has to be bound to *something*, be it None or a
>> zombie (which will act almost like None) or whatever.  You'll reclaim
>> a small amount of memory, but that's about it.
>
> As it turned out, pyste already supported auto_ptr. And it also seems 
> that BPL treats auto_ptr quite sensibly, so it "just works". Wish I 
> had known as it would have saved me a day's work :(

You could have taken my word for it :)

> My current problem is when running through virtual function wrappers 
> in that call_method<> tries converting an unsigned int * to an 
> unsigned int which I don't want. I tried putting ptr() round it like 
> this:
>
>     void setData(FX::FXColor* p0, FX::FXuint p1) {
>         call_method< void >(py_self, "setData", ptr(p0), p1);
>     }
>
> (here FXColor is a typedef for unsigned int)
>
> ... but BPL won't take pointers to integral types in ptr(), and thus
> I can't see how to pass the pointer as-is.
>
>
> Why doesn't BPL's ptr() accept pointers to integral types?

Think about how you would implement such a thing.  What would a
an overriden virtual function written in Python see?

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