Re: [pygccxml-development] class registration function names

[Roman Y. <rom...@gm...>]

Hello

On Mon, Jun 13, 2011 at 9:39 PM, Babak Khataee <bab...@gm...> wrote:

> Hi There,
>
> I've come across what might be an unusual problem involving py++ generated
> boost python code that I was hoping someone might be able to help me with.
>
> We're using py++ to create python bindings for two libraries, one third
> party (libA)  and the other in house (libB - which has a dependency on
> libA). The two libraries both define a class called 'Box2f' which is being
> exposed in both bindings. Before importing the bindings into python we set
> the dlopen flags to be 'RTLD_GLOBAL | RTLD_NOW' to avoid cross module
> problems. Due to the dependency between the two libA needs to be imported
> first. Doing so defines and calls the registration function for the Box2f
> class, now when libB is imported it calls the same Box2f registration
> function rather its own one.


Are you sure?


> This means that libAbinding.Box2f is the same as libBbinding.Box2f :(
>
> It seems that the binding code for both libraries defines a
> 'register_Box2f_class' function and that renaming this in either library
> binding code fixes the problem. However, I was wondering if there is a way
> change the name of the function that gets generated through  py++ ? I've had
> a peek around the code and got the impression that by creating a custom
> 'multiple_files_t' class I could control this behaviour, but I wasn't sure
> whether this would be a good approach or not ?
>
> An alternative would be to just change the name of the classes in the
> binding so they're not the same, but if possible we'd rather avoid
> introducing differences between the binding and library code.
>

I think your analysis has a mistake.  'RTLD_GLOBAL | RTLD_NOW' causes
Boost.Python registry (the component, which keeps the registered classes,
functions, conversions and etc) to be defined only once and shared between
all extension modules. In my opinion, what happens is that you are trying to
register class with the same name and Boost.Python skips the second
definition. (You should get the warning, during your extension import).

I think, what you can do is to change the classes aliased, import them into
Python and then to provide a new alias, which is the original name,


mb = module_builder_t(...)
mb.class_('Box2f').alias = "LibBBox2f"


libB/
    __init__.py
    libbbinding.so


where __init__.py content is something like:

import * from libbbinding
Box2f = LibBox2f


> Hopefully that makes sense, any advice/help with this would be greatly
> appreciated.
> Thank you very much.
>
> HTH