[netfilter-nf:testing 11/20] net/netfilter/ipset/ip_set_hash_gen.h:379:21: warning: result of comparison of constant -1 with expression of type 'u8' (aka 'unsigned char') is always false

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git testing
head:   c2fbcb9151957c3d921a7441cf080e49eb13b05d
commit: a900abcb974bae821a5d4ae79ad3442808915416 [11/20] netfilter: ipset: rework cidr bookkeeping
config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20260708/[email protected]/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260708/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All warnings (new ones prefixed by >>):

   In file included from net/netfilter/ipset/ip_set_hash_ipportnet.c:131:
>> net/netfilter/ipset/ip_set_hash_gen.h:379:21: warning: result of comparison of constant -1 with expression of type 'u8' (aka 'unsigned char') is always false [-Wtautological-constant-out-of-range-compare]
     379 |         if (unlikely(found == -1))
         |                      ~~~~~ ^  ~~
   include/linux/compiler.h:77:42: note: expanded from macro 'unlikely'
      77 | # define unlikely(x)    __builtin_expect(!!(x), 0)
         |                                             ^
   In file included from net/netfilter/ipset/ip_set_hash_ipportnet.c:391:
>> net/netfilter/ipset/ip_set_hash_gen.h:379:21: warning: result of comparison of constant -1 with expression of type 'u8' (aka 'unsigned char') is always false [-Wtautological-constant-out-of-range-compare]
     379 |         if (unlikely(found == -1))
         |                      ~~~~~ ^  ~~
   include/linux/compiler.h:77:42: note: expanded from macro 'unlikely'
      77 | # define unlikely(x)    __builtin_expect(!!(x), 0)
         |                                             ^
   2 warnings generated.


vim +379 net/netfilter/ipset/ip_set_hash_gen.h

   364	
   365	static void
   366	mtype_del_cidr(struct ip_set *set, struct htype *h, u8 cidr, u8 n)
   367	{
   368		struct net_prefixes *nets, *tmp;
   369		u8 i, j, found, len = 0;
   370	
   371		spin_lock_bh(&set->lock);
   372		nets = __ipset_dereference(h->rnets[n]);
   373		for (i = 0, found = -1; i < nets->len; i++) {
   374			if (nets->nets[i].count)
   375				len++;
   376			if (nets->nets[i].cidr == cidr)
   377				found = i;
   378		}
 > 379		if (unlikely(found == -1))
   380			return;
   381		nets->nets[found].count--;
   382		if (nets->nets[found].count)
   383			goto unlock;
   384		len--;
   385		tmp = kzalloc(sizeof(struct net_prefixes) +
   386			      len * sizeof(struct net_prefix), GFP_ATOMIC);
   387		if (!tmp)
   388			/* Leave a hole */
   389			return;
   390		tmp->len = len;
   391		for (i = 0, j = 0; i < nets->len; i++) {
   392			if (!nets->nets[i].count || i == found)
   393				continue;
   394			tmp->nets[j].cidr = nets->nets[i].cidr;
   395			tmp->nets[j++].count = nets->nets[i].count;
   396		}
   397		rcu_assign_pointer(h->rnets[n], tmp);
   398		kfree_rcu(nets, rcu);
   399	unlock:
   400		spin_unlock_bh(&set->lock);
   401	}
   402	#endif
   403	

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