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

On Wed, Nov 10, 2010 at 12:26:03PM +0000, Daniel P. Berrange wrote: > 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 Apparently "scope" there means something a bit different. Try this program to see it definitely works (and also swap the order of the include and the typedef): ---------------------------------------------------------------------- #include <stdio.h> #include <stdlib.h> #include <libvirt/libvirt.h> typedef struct _virDomain virDomain; typedef virDomain *virDomainPtr; int main () { printf ("hello\n"); exit (0); } ---------------------------------------------------------------------- gcc -Wall -o test test.c It doesn't need the #ifndef as suggested by that link.