On 04/03/2013 09:06 AM, Daniel P. Berrange wrote:
From: "Daniel P. Berrange" <berrange@redhat.com>
The virNetlinkCommand() method takes an 'unsigned char **' parameter to be filled with the received netlink message. The callers then immediately cast this to 'struct nlmsghdr', triggering (bogus) warnings about increasing alignment requirements
Not bogus warnings unless all callers were really passing in something that was already aligned to struct nlmsghdr requirements. But your analysis was right - the pointer was properly aligned.
util/virnetdev.c: In function 'virNetDevLinkDump': util/virnetdev.c:1300:12: warning: cast increases required alignment of target type [-Wcast-align] resp = (struct nlmsghdr *)*recvbuf; ^
Since all callers cast to 'struct nlmsghdr' we can avoid the warning problem entirely by simply changing the signature of virNetlinkCommand to return a 'struct nlmsghdr **' instead of 'unsigned char **'. The way we do the cast inside virNetlinkCommand does not have any alignment issues.
Yeah, telling the compiler the correct type to begin with is better anyways. ACK. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org