[C++-sig] ANNOUNCE: PyBindGen 0.8

[Gustavo Carneiro]

On 01/06/2008, Hans Meine <meine at informatik.uni-hamburg.de> wrote:
>
> Hi!
>
>
> On Dienstag 04 Dezember 2007, Gustavo Carneiro wrote:
> > The other day I released PyBindGen 0.8.  Main news is that it features a
> > new experimental header file scanner based on pygccxml (i.e., it's
> similar
> > to py++ in scope, if not in maturity, but does not use
> > boost.pythonunderneath).
>
>
> This all sounded very interesting, so I have just tried pybindgen out.
>
> First, I noticed, that void return type is handled with Py_BuildValue,
> which
> is slight overkill, isn't it (since one of PyBindGen's design goals is to
> write lean, nearly-handwritten style code)?


True.  But I think special-casing for when only None is returned makes sense
and should be relatively simple to implement.

  I have registered on launchpad
> to be able to submit a patch when I would have managed to make it return
> Py_None directly, but I have more serious problems when trying to wrap the
> following simple type declaration:
>
> union Word
> {
>         short word;
>         struct
>         {
>                 char low, high;
>         };
> };
>
> The gccxml module does not seem to recognize the "short" return value:
>
> .../word.h:6: Warning: Return value 'short int' error (used in Word::word
> [variable]): TypeLookupError('short int',)
>   short word;
>
> However, when looking at pybindgen/typehandlers/inttype.py, fixing this
> seems
> to be possible, but I wonder if a more general approach than adding one
> class
> for each combination of const/ptr/ref/unsigned/width integer type would be
> more sensible?


 I'm not sure.  Maybe it's possible to find a common base class for all
int-like types.

  Obviously, I'd better leave this decision & fix to the
> original authors.
>
> Finally, the anonymous struct inside the union is not yet
> supported.  AFAICS,
> PyBindGen would "simply" need to descend into the struct and export its
> members like direct members of the surrounding type.  Right now, it
> produces
> illegal code because it tries to wrap a data member with an empty string as
> name:
>
> static PyObject* _wrap_PyWord__get_(PyWord *self)
> {
>     PyObject *py_retval;
>     PyWord *py_Word;
>
>     py_Word = PyObject_New(PyWord, &PyWord_Type);
>     py_Word->obj = new Word(self->obj->);
>     py_retval = Py_BuildValue("N", py_Word);
>     return py_retval;
> }
> [...]
> static PyGetSetDef PyWord__getsets[] = {
>     {
>         "", /* attribute name */
>         (getter) _wrap_PyWord__get_, /* C function to get the attribute */
>         (setter) _wrap_PyWord__set_, /* C function to set the attribute */
>         NULL, /* optional doc string */
>         NULL /* optional additional data for getter and setter */
>     },
>     { NULL, NULL, NULL, NULL, NULL }
> };


Ugh.. right, I guess it's a bug.  But I am curious, how do you access
anonymous structures from C?  It does not seem possible, unless I am missing
something, and if so, what would be the point in wrapping them?  Maybe it's
better to just ignore it?

Thanks for your feedback.

Although I have not made any PyBindGen release in a very long time,
development is far from stagnated, in case anyone is wondering...

-- 
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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