Re: [Xen-devel] [PATCH v2-resend 02/30] libxl: idl: allow KeyedUnion members to be empty

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-08-27 at 15:53 +0100, Ian Jackson wrote:
> Rob Hoes writes ("[Xen-devel] [PATCH v2-resend 02/30] libxl: idl: allow 
> KeyedUnion members to be empty"):
> > This is useful when the key enum has an "invalid" option and avoids
> > the need to declare a dummy struct. Use this for domain_build_info
> > resulting in the generated API changing like so:
> >     --- tools/libxl/_libxl_BACKUP_types.h
> >     +++ tools/libxl/_libxl_types.h
> >     @@ -377,8 +377,6 @@ typedef struct libxl_domain_build_info {
> >                  const char * features;
> >                  libxl_defbool e820_host;
> >              } pv;
> >     -        struct {
> >     -        } invalid;
> >          } u;
> 
> I assume that the problem here is that the compiler rejects the empty
> struct.

I don't recall exactly, but I think so.

> 
> > -                 ("invalid", Struct(None, [])),
> > +                 ("invalid", None),
> 
> Is it really necessary to do this with a special-cased new "None" type
> rather than just fixing the empty structs by putting a dummy member in
> them ?

I'd rather a bit of skaniness in the idl compiler than in the end user
facing eventual API.

Ian.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel