Re: [Libvir] PATCH: 5/10: public auth callback API
On Tue, Dec 04, 2007 at 10:46:50AM -0500, Daniel Veillard wrote:
On Tue, Dec 04, 2007 at 12:57:39PM +0000, Richard W.M. Jones wrote:
> Daniel P. Berrange wrote:
> > virConnectPtr virConnectOpenAuth (const char *name,
> > virConnectAuthPtr auth,
> > int flags);
>
> I'm a fan of callers passing in the size of the structure (as they see
> it). Allows the structure to be expanded in future, and if done right
> can allow both forwards and backwards compatibility.
>
> cf: http://www.libvirt.org/html/libvirt-libvirt.html#virDomainInterfaceStats
Hum, honnestly, that's not my preferred way. If you really think there
should be room for expansion, I would either:
- add a version number to the structure and allocator/destructor
functions as part of the API (prefered)
This adds more complexity and the single sizeof(*auth) param IMHO.
- add padding at tyhe end of the structure which could allow
a future growth
adding the size of the structure as the argument moves the complexity
away
from the library implementor to the library user,
It doesn't really - the user just has to add sizeof(*auth) as an arg and
all the rest of the complexity is in the library internals.
In fact it doesn't need to add any complexity, because we could make it a
compile time macro
#define virConnectOpenAuth(name,auth,flags)
virConnectOpenAuth(name,auth,sizeof(*auth),flags)
Dan
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