On Wed, May 24, 2017 at 11:32 PM, Ihar Hrachyshka <ihrac...@redhat.com> wrote: > On 05/23/2017 01:56 PM, Arnd Bergmann wrote: >> >> This seems to have caused a build warning: >> >> net/ipv4/arp.c:880:35: warning: 'addr_type' may be used uninitialized >> in this function [-Wmaybe-uninitialized] >> > Not sure. How do you reproduce it? I just did 'make net' in the latest tree > that includes the patch, and it doesn't trigger the failure. Also the code > logic prevents it to be uninitialized (it's always set to -1 or the actual > type value).
I saw it reported by the kernelci build bot: https://kernelci.org/build/id/5925b81859b514fb106b9590/logs/ It happened on arm64 with 'make allmodconfig', but none of the other architectures or the other configurations on that architecture. This kind of warning can be a real pain to shut up when the compiler gets it wrong. I haven't tested the latest kernel with your patch on my own build box yet, so I also haven't been able to reproduce it. Most likely, gcc gets confused when it needs to track the state of too many variables here (I certainly get confused when I read it too). My first attempt to resolve it would be: diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index ae96e6f3e0cb..39f26980a565 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -663,6 +663,8 @@ static bool arp_is_garp(struct net *net, struct net_device *dev, *addr_type = inet_addr_type_dev_table(net, dev, sip); if (*addr_type != RTN_UNICAST) is_garp = false; + } else { + *addr_type = -1; } return is_garp; } @@ -864,7 +866,6 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb) n = __neigh_lookup(&arp_tbl, &sip, dev, 0); if (n || IN_DEV_ARP_ACCEPT(in_dev)) { - addr_type = -1; is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op, sip, tip, sha, tha); } but this clearly needs a lot of build testing to see if it's sufficient. Moving the initialization of addr_type=1 to the start of the function would certainly avoid the warning, but I suspect this would be incorrect here. Arnd
