[C++-sig] Boost-python/pybindgen and wrapping member variables

[Gustavo Carneiro]

On Wed, Jan 20, 2010 at 7:26 PM, Ben Fitzpatrick <
bfitzpatrick at vtiinstruments.com> wrote:

>  Gustavo,
>
>
>
> I think you win some sort of prize for not only fastest mailing list
> responses, but also fastest implementation of features. I reviewed the diff,
> and changed what I was adding to the global annotations table for these
> pointers to “{‘return_internal_reference’:’true’}” – this seems to be what
> the new code in foo.h was doing.  I am still getting the errors, though – is
> this the right way of using it?
>
I am not sure what is wrong.  Assuming you are using a "pre_scan_hook", and
that you are doing something like
global_annotations[‘return_internal_reference’]
= True, in the proper attribute definition, then it should work.  Is it the
same error message, or a different error?


>
> And just to make sure, I grabbed a new checkout of pybindgen and
> re-installed it.
>
>
>
> *From:* cplusplus-sig-bounces+bfitzpatrick=vtiinstruments.com at python.org[mailto:
> cplusplus-sig-bounces+bfitzpatrick <cplusplus-sig-bounces%2Bbfitzpatrick>=
> vtiinstruments.com at python.org] *On Behalf Of *Gustavo Carneiro
> *Sent:* Wednesday, January 20, 2010 1:18 PM
> *To:* Development of Python/C++ integration
> *Subject:* Re: [C++-sig] Boost-python/pybindgen and wrapping member
> variables
>
>
>
>
>
> On Wed, Jan 20, 2010 at 5:43 PM, Ben Fitzpatrick <
> bfitzpatrick at vtiinstruments.com> wrote:
>
> Hi everyone,
>
>
>
> I think I’m finally getting the hang of this, I seem to have gotten almost
> everything in my project working thanks to Gustavo’s latest pybindgen patch.
> One of the remaining things I am having difficulty with is putting
> annotations on member variables of a class. I have something of the form:
>
>
>
> class foo{
>
>  <stuff>
>
> };
>
>
>
> class baz {
>
>   public:
>
>   foo* var;
>
> }
>
>
>
> The error I am getting from pybindgen is “WrapperWarning: Return value
> ‘::foo *’ error (used in baz::var [variable]):
> TypeConfigurationError(‘Either caller_owns_return or
> self.reference_existing_object must be given’)
>
>
>
>  I know that the issue is that I need to stick an annotation on there.
> Since the pointer is allocated and tracked by the underlying C++ code, I’m
> pretty sure that I need to put reference_existing_object on it. I’ve tried
> inserting “{‘reference_existing_object’ : ‘true’}” into the
> global_annotations table, and also inserting it into the
> parameter_annotations[“return”] dictionary. For kicks, I even tried both at
> once. No matter what I do I can’t get rid of the error, or see it show up in
> my final build, which leads me to believe there’s something I’m missing. I
> went and looked up the documentation for reference_existing_object, but of
> course none of their examples show how you could use it on a member
> variable. What am I missing?
>
> You are not missing anything.  Annotations for member variables (pybindgen
> calls them "instance attributes") were not implemented.
>
>
>
> An oversight easily fixed:
>
>
>
> http://bazaar.launchpad.net/~gjc/pybindgen/trunk/revision/742
>
>
>
>
>
> Thanks,
>
> Ben Fitzpatrick
>
>
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>
>
>
> --
> Gustavo J. A. M. Carneiro
> INESC Porto, Telecommunications and Multimedia Unit
> "The universe is always one step beyond logic." -- Frank Herbert
>
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>



-- 
Gustavo J. A. M. Carneiro
INESC Porto, Telecommunications and Multimedia Unit
"The universe is always one step beyond logic." -- Frank Herbert
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