On Sat, Aug 9, 2014 at 3:14 PM, Pekka Paalanen <ppaala...@gmail.com> wrote:
> I see nothing wrong here, memset to zero is a usual pattern, and > wl_proxy is a complex enough type, that checking every member is > set is tedious. Therefore: > > Reviewed-by: Pekka Paalanen <ppaala...@gmail.com> > Thanks! > But I do wonder, if it ever makes sense to check user data for > NULL, and set if it is NULL. If user_data is NULL, how can you > ever be sure, that the wl_proxy was created by your code, and not > by some library you use? > > Even when user_data is not NULL, you should have some explicit way > of checking whether the pointer is yours or not. > If I would use any external libraries (like Qt or something), I agree that I could not possibly trust the value of user_data, since I don't know, what the library is doing there. But I'm not using any external libraries, just libwayland-client. I thought that all proxies that are created by marshal_constructor or come from events with new_id type arguments are created by either of these two functions and therefore would have a NULL user_data if they got initialised there. If this is wrong, please tell me. :) > An example: you use a library and you passed the wl_display to it. > This library goes and creates a wl_surface of its own. This > wl_surface gets targeted by input, so your client receives e.g. > wl_pointer.enter. In the wl_pointer.enter handler, you now suddenly > have a wl_proxy for a wl_surface that you did not create, and > therefore the user_data is nothing you would expect. If you are > lucky, your program crashes here. > > The problems emerges in all event handlers, where the event carries > an object as an argument. > > > Thanks, > pq >
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