Re: [libvirt] [PATCH 2/7] Avoid casts between unsigned char * and struct nlmsghdr
On 04/03/2013 09:06 AM, Daniel P. Berrange wrote:
From: "Daniel P. Berrange" <berrange(a)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
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