Re: [Libguestfs] [PATCH 5/7] New APIs: add-domain and add-libvirt-dom.

On Wed, Nov 10, 2010 at 12:11:22PM +0000, Richard W.M. Jones wrote: > On Wed, Nov 10, 2010 at 11:58:40AM +0000, Daniel P. Berrange wrote: > > On Wed, Nov 10, 2010 at 11:46:31AM +0000, Richard W.M. Jones wrote: > > > diff --git a/src/guestfs.h b/src/guestfs.h > > > index 0f4f9fd..be7398a 100644 > > > --- a/src/guestfs.h > > > +++ b/src/guestfs.h > > > @@ -79,6 +79,11 @@ extern void guestfs_set_private (guestfs_h *g, const char *key, void *data); > > > extern void *guestfs_get_private (guestfs_h *g, const char *key); > > > > > > /*--- Structures and actions ---*/ > > > + > > > +/* Hack to avoid needing to include <libvirt.h> */ > > > +typedef struct _virDomain virDomain; > > > +typedef virDomain *virDomainPtr; > > > + > > > #include <rpc/types.h> > > > #include <rpc/xdr.h> > > > #include <guestfs-structs.h> > > > > Surely this will break any application whose code does > > > > #include <libvirt/libvirt.h> > > #include <guestfs.h> > > > > because they'll get a duplicated definition of virDomain from > > both headers. > > I checked and it works fine both ways round. It would break if > libvirt changed the definition, but you've boxed yourself into a > corner there by documenting the current definition: Surely the compiler should complain about duplicated typedefs, even if they are identical, because C doesn't allow duplicate typedefs within the same scope. http://david.tribble.com/text/cdiffs.htm#C99-typedefs eg $ cat st.c typedef struct foo foo; typedef struct foo foo; $ gcc -Wall -o st st.c st.c:3:20: error: redefinition of typedef ‘foo’ st.c:2:20: note: previous declaration of ‘foo’ was here

Then perhaps the integration glue should be a separate library, so libguestfs.so provides the core infrastructure, and then a libguest-libvirt.so provides higher level libvirt integration. This way people who don't want it can avoid any dep, but apps that do want libvirt can use the extra library and guarentee they'll have the functionality there, avoiding any nasty runtime surprises from libvirt being missing.