[PATCH v1 net-next 1/1] net: Mark possible unused variables on stack with __maybe_unused

[PATCH v1 net-next 1/1] net: Mark possible unused variables on stack with __maybe_unused

[Andy Shevchenko]

When compile with COMPILE_TEST=y the -Werror is implied.
If we run `make W=1` the first level warnings will become
the build errors. Some of them related to possible unused
variables. Hence, to allow clean build in such case, mark
them with __maybe_unused.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 net/ipv4/netfilter/nf_reject_ipv4.c | 2 +-
 net/ipv6/ip6_fib.c                  | 3 ++-
 net/ipv6/netfilter/nf_reject_ipv6.c | 2 +-
 net/socket.c                        | 2 +-
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index 4eed5afca392..52d943426705 100644
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -239,7 +239,7 @@ void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
 {
 	struct net_device *br_indev __maybe_unused;
 	struct sk_buff *nskb;
-	struct iphdr *niph;
+	struct iphdr __maybe_unused *niph;
 	const struct tcphdr *oth;
 	struct tcphdr _oth;
 
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 0371d2c14145..8783e49a5465 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1374,7 +1374,8 @@ int fib6_add(struct fib6_node *root, struct fib6_info *rt,
 	     struct nl_info *info, struct netlink_ext_ack *extack)
 {
 	struct fib6_table *table = rt->fib6_table;
-	struct fib6_node *fn, *pn = NULL;
+	struct fib6_node *fn;
+	struct fib6_node __maybe_unused *pn = NULL;
 	int err = -ENOMEM;
 	int allow_create = 1;
 	int replace_required = 0;
diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c
index dffeaaaadcde..69b98a6183b3 100644
--- a/net/ipv6/netfilter/nf_reject_ipv6.c
+++ b/net/ipv6/netfilter/nf_reject_ipv6.c
@@ -284,7 +284,7 @@ void nf_send_reset6(struct net *net, struct sock *sk, struct sk_buff *oldskb,
 	const struct tcphdr *otcph;
 	unsigned int otcplen, hh_len;
 	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
-	struct ipv6hdr *ip6h;
+	struct ipv6hdr __maybe_unused *ip6h;
 	struct dst_entry *dst = NULL;
 	struct flowi6 fl6;
 
diff --git a/net/socket.c b/net/socket.c
index 7f64a6eccf63..fbb442adf27f 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2199,7 +2199,7 @@ int __sys_getsockopt(int fd, int level, int optname, char __user *optval,
 {
 	int err, fput_needed;
 	struct socket *sock;
-	int max_optlen;
+	int __maybe_unused max_optlen;
 
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)
-- 
2.33.0

Re: [PATCH v1 net-next 1/1] net: Mark possible unused variables on stack with __maybe_unused

[Jakub Kicinski]

On Fri,  1 Oct 2021 17:50:56 +0300 Andy Shevchenko wrote:
> When compile with COMPILE_TEST=y the -Werror is implied.
> If we run `make W=1` the first level warnings will become
> the build errors. Some of them related to possible unused
> variables. Hence, to allow clean build in such case, mark
> them with __maybe_unused.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

You need to split the socket and fib change from the netfilter ones.
Those go via different sub-trees.