[PATCH wayland] Add "enum" attribute to "arg" elements

[Pekka Paalanen]

On Wed, 3 Sep 2014 10:28:30 +0300
Giulio Camuffo <giuliocamuffo at gmail.com> wrote:

> 2014-09-03 10:15 GMT+03:00 Pekka Paalanen <ppaalanen at gmail.com>:
> > On Mon, 1 Sep 2014 22:07:44 +0200
> > "Nils Chr. Brause" <nilschrbrause at gmail.com> wrote:
> >
> >> On Mon, Sep 1, 2014 at 10:45 AM, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> >
> >> > Another problem with this patch is that while it adds new syntax to the
> >> > protocol XML, it does not add anything that would either explain nor
> >> > validate/enforce it. (We do not actually use the DTD for anything
> >> > anymore.)
> >> >
> >> > Yes, we do not have a document describing the XML format, and that is a
> >> > problem. Would be nice to start one, if anyone can work with Publican.
> >> >
> >> > The very least, wayland-scanner should be reading the enum attribute
> >> > and check that the referenced enum exists. I'm not sure if it can
> >> > generate a nice doc snippet into the generated code, but if there is a
> >> > way to include that, it would be useful. We need *something* in the
> >> > Wayland repository actually using these new attributes, so that they do
> >> > not bit-rot immediately.
> >>
> >> I will look into the scanner code then. That is probably the easiest
> >> possibility
> >> to prevent bit-rot, since I never did anything with Publican.
> >>
> >> While I'm at that, I would also like to make use of the enum names in the
> >> generated C code. As far as I can see, this would not break any existing
> >> code, would it? Also, that would require the enum definitions to be at the
> >> top
> >> of the header files (just below the struct forward declarations), because
> >> enums cannot be forward declared. Would that be acceptable?
> >
> > Perhaps, if it does not cause problems on C++. I'm not sure, but I
> > recall C++ being more strict than C wrt. enums.
> 
> It is, in the sense that it doesn't automatically cast int to enums,
> so that could break the API. Also, wouldn't it possibily be an ABI
> break? Afaik enums don't have a very defined size, so what is now a
> int32 could become e.g. a 16 bits enum field.

Yeah, I think that is another valid concern.


Thanks,
pq