[libvirt] [PATCH] network: selectively disable -Wcast-align in virNetDevParseDadStatus

[Daniel P. Berrange]

On Tue, Dec 01, 2015 at 05:49:10PM -0700, Jim Fehlig wrote:
> On 11/30/2015 09:18 PM, Jim Fehlig wrote:
> > On 11/26/2015 08:10 AM, Ian Campbell wrote:
> >> Commit 0f7436ca54c9 "network: wait for DAD to finish for bridge IPv6 addresses"
> >> results in:
> >>
> >>  CC     util/libvirt_util_la-virnetdevmacvlan.lo
> >> util/virnetdev.c: In function 'virNetDevParseDadStatus':
> >> util/virnetdev.c:1319:188: error: cast increases required alignment of target type [-Werror=cast-align]
> >> util/virnetdev.c:1332:41: error: cast increases required alignment of target type [-Werror=cast-align]
> >> util/virnetdev.c:1334:92: error: cast increases required alignment of target type [-Werror=cast-align]
> >> cc1: all warnings being treated as errors
> >>
> >> on at least ARM platforms.
> > Thanks for looking into this issue Ian.
> >
> >> The three macros involved (NLMSG_NEXT, IFA_RTA and RTA_NEXT) all appear to
> >> correctly take care of alignment, therefore suppress Wcast-align around their
> >> uses.
> > Indeed those macros seem to handle alignment, even on one of my older machines
> > with 2.6 kernel headers. IMO this falls under the "difficult or impossible to
> > address" scenarios that Daniel mentioned when introducing the VIR_WARNINGS_*
> > macros via commit e57aaa6f. Adding Daniel to cc for a sanity check of my weak ACK.
> 
> Looks like I forgot to actually add Daniel to the cc list. Doing so now...
> 
> >
> > Regards,
> > Jim
> >
> >> Signed-off-by: Ian Campbell <ian.campbell at citrix.com>
> >> Cc: Maxim Perevedentsev <mperevedentsev at virtuozzo.com>
> >> Cc: Laine Stump <laine at laine.org>
> >> Cc: Dario Faggioli <dario.faggioli at citrix.com>
> >> Cc: Jim Fehlig <jfehlig at suse.com>
> >> ---
> >>  src/util/virnetdev.c | 5 +++++
> >>  1 file changed, 5 insertions(+)
> >>
> >> diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
> >> index ade9afa..0bc809e 100644
> >> --- a/src/util/virnetdev.c
> >> +++ b/src/util/virnetdev.c
> >> @@ -1316,7 +1316,10 @@ virNetDevParseDadStatus(struct nlmsghdr *nlh, int len,
> >>      struct rtattr *rtattr_ptr;
> >>      size_t i;
> >>      struct in6_addr *addr;
> >> +
> >> +    VIR_WARNINGS_NO_CAST_ALIGN
> >>      for (; NLMSG_OK(nlh, len); nlh = NLMSG_NEXT(nlh, len)) {
> >> +    VIR_WARNINGS_RESET
> >>          if (NLMSG_PAYLOAD(nlh, 0) < sizeof(struct ifaddrmsg)) {
> >>              /* Message without payload is the last one. */
> >>              break;
> >> @@ -1329,9 +1332,11 @@ virNetDevParseDadStatus(struct nlmsghdr *nlh, int len,
> >>          }
> >>  
> >>          ifaddrmsg_len = IFA_PAYLOAD(nlh);
> >> +        VIR_WARNINGS_NO_CAST_ALIGN
> >>          rtattr_ptr = (struct rtattr *) IFA_RTA(ifaddrmsg_ptr);
> >>          for (; RTA_OK(rtattr_ptr, ifaddrmsg_len);
> >>              rtattr_ptr = RTA_NEXT(rtattr_ptr, ifaddrmsg_len)) {
> >> +            VIR_WARNINGS_RESET
> >>              if (RTA_PAYLOAD(rtattr_ptr) != sizeof(struct in6_addr)) {
> >>                  /* No address: ignore. */
> >>                  continue;


Yeah, that looks like about as good as we'll get to deal with this
so ACK to that change in absence of any better suggestion.


Regards,
Daniel
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