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

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(a)citrix.com&gt; >>> Cc: Maxim Perevedentsev <mperevedentsev(a)virtuozzo.com&gt; >>> Cc: Laine Stump <laine(a)laine.org&gt; >>> Cc: Dario Faggioli <dario.faggioli(a)citrix.com&gt; >>> Cc: Jim Fehlig <jfehlig(a)suse.com&gt; >>> --- >>> 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.