Re: [pygccxml-development] Fwd: instance attribute with anonymous enum type

[Gustavo C. <gjc...@gm...>]

2008/10/15 Roman Yakovenko <rom...@gm...>

> On Wed, Oct 15, 2008 at 7:06 PM, Gustavo Carneiro <gjc...@gm...>
> wrote:
> > Sorry, Roman, I really meant to send to the mailing list! :-)
>
> Hi. That's okey.
>
> > From: Gustavo Carneiro <gjc...@gm...>
> >
> > Hello, I am hitting a problem in pygccxml regarding anonymous enums used
> as
> > class member variables.
> >
> > Something like this:
> >
> > class SomeObject
> > {
> > public:
> >
> >     enum {
> >         TYPE_FOO,
> >         TYPE_BAR,
> >     } type;
> > };
> >
> > When I scan this, pygccxml tells me the attribute 'type' of 'SomeObject'
> is
> > of type 'SomeObject'.  I happily try to generate code for this, and of
> > course the generated code does not even compile:
> >
> > [14/25] cxx: build/default/tests/foomodule2.cc ->
> > build/default/tests/foomodule2_9.o
> > default/tests/foomodule2.cc: In function 'int
> > _wrap_PySomeObject__set_type(PySomeObject*, PyObject*)':
> > default/tests/foomodule2.cc:6211: error: cannot convert 'SomeObject' to
> > 'SomeObject::<anonymous enum>' in assignment
> > Build failed
>
> Indeed, pygccxml has a problem to create full type name for unnamed
> types, and the solution I choose, is to report named parts only.
>
> > It would be better if pygccxml reported the type as
>  "SomeObject::<anonymous
> > enum>", like GCC does.  This way at least I will not be lead me to
> generate
> > invalid code (I prefer no code at all than erroneous code).
>
> How? You still will have to check whether the type has name or not and
> avoid the generation.


If the type string returned by pygccxml was simply "SomeObject::<anonymous
enum>", I would not have to do anything in my case (pybindgen).  That type
is not registered, and so an exception like
TypeLookupError("SomeObject::<anonymous enum>") would be raised and printed
to the user as warning, but no code would be generated for that definition.


>
>
> More over in this concrete example, you can do better. You can expose
> all enum values as int within the class scope. Member variable "type"
> could also be exposed as int.
>
> Yes, this is a special case, but it could be completely handled by
> code generator.


Yes. I know it is possible wrap it.  Maybe some day I will wrap it, but I
don't have time for everything, and I don't need that feature right now ;-)


>
>
> > This with pygccxml 0.9.5, gccxml 2008-04-20.
> >
> > My work around for the moment is:
> >
> >                 real_type = type_traits.remove_declarated(member.type)
> >                 if hasattr(real_type, 'name') and not real_type.name:
> >                     print >> sys.stderr, ">>>>>>>>>>>>>> skip anonymous
> > type"
> >                     continue
>
> As I said unnamed types is a special case.


Personally I think it is deceptive to return a type expression that does not
correspond to the real type.  I mean, it's worse, it is returning a type
string that corresponds to _another_ type, one which is perfectly valid.
This induces the code generator to generate incorrect code...


>
>
> Py++ has solution for this and other issues. It extends every
> declaration class, defined in pygccxml. One of the functions, it adds
> is the ability of declarations to analyze "itself" and report
> problems, and whether it could be exported or not.
>
> For example:
>
> http://pygccxml.svn.sourceforge.net/viewvc/pygccxml/pyplusplus_dev/pyplusplus/decl_wrappers/enumeration_wrapper.py?view=markup
>
>
> http://pygccxml.svn.sourceforge.net/viewvc/pygccxml/pyplusplus_dev/pyplusplus/decl_wrappers/calldef_wrapper.py?revision=1428&view=markup
>
> take a look on _exportable_impl method.
>
> Thus the actual "code generator" code is clear, because it doesn't
> need to deal with such cases. It just asks the declaration.


Hm.. OK.  I am more of a down to earth guy and prefer more simple and direct
solutions...  at least to begin with  :-)

But thanks for the tip.

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