Re: [libvirt] [Xen-devel] Fixing libvirt's libxl driver breakage -- where to define LIBXL_API_VERSION?

On Wed, Apr 13, 2016 at 10:09:16AM +0100, George Dunlap wrote: > On Tue, Apr 12, 2016 at 10:31 PM, Jim Fehlig <jfehlig(a)suse.com&gt; wrote: >> Wei Liu wrote: >>> Hi libvirt maintainers, >> Sorry for the delay. Slowly catching up on mail after vacation... >> >>> Xen's control library libxenlight (libxl) requires application >>> (libvirt in this case) to explictily define LIBXL_API_VERSION. >> Where is this requirement written? :-) >> >>> This is >>> lacking at the moment so libvirt's libxl driver always gets the latest >>> APIs. >> IMO, that is what we want for upstream libvirt. Downstreams can choose a >> specific version if they want. > I think one of us isn't understanding the situation properly. Is it > not the case that currently, all releases of libvirt *will not > compile* against Xen 4.7 once it's released? So people downloading > and building libvirt will have to either 1) root around and try to > figure out what version of Xen it will build against, 2) manually add > in a #define *with the correct API version* to a header somewhere to > make it build properly, or 3) update to a version of libvirt that > supports the new api (which at the moment hasn't even been released > yet)? > > All of those options are completely unacceptable. Older versions of > libvirt should Just Work when compiled against newer versions of Xen. > > I think it does make sense to have the libvirt development branch not > specify an API version; but when it branches for release, it should > set LIBXL_API_VERSION to whatever the current version is at the time > of the branch. FYI, libvirt doesn't do branching for releases - we always just cut the release straight from the master branch. We only actually create branches on demand, when we find we want to backport fixes to a previous release. Does libvirt master really need to always use the latest API version ? It feels like libvirt could just set LIBXL_API_VERSION to the lowest version it requires in order to get the functionality we know we are able to currently build against.