Following warning is encountered when building selftests on powerpc/32.

  CC       csum
csum.c: In function 'recv_get_packet_csum_status':
csum.c:710:50: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  710 |                         error(1, 0, "cmsg: len=%lu expected=%lu",
      |                                                ~~^
      |                                                  |
      |                                                  long unsigned int
      |                                                %u
  711 |                               cm->cmsg_len, CMSG_LEN(sizeof(struct tpacket_auxdata)));
      |                               ~~~~~~~~~~~~
      |                                 |
      |                                 size_t {aka unsigned int}
csum.c:710:63: warning: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'unsigned int' [-Wformat=]
  710 |                         error(1, 0, "cmsg: len=%lu expected=%lu",
      |                                                             ~~^
      |                                                               |
      |                                                               long unsigned int
      |                                                             %u

cm->cmsg_len has type __kernel_size_t and CMSG() macro has the type
returned by sizeof() which is size_t.

size_t is 'unsigned int' on some platforms and 'unsigned long' on
other ones so use %zu instead of %lu.

This fixes commit 91a7de85600d ("selftests/net: add csum offload test").

Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
---
v2: Removed use %zu instead of %u and removed Fixes tag
---
 tools/testing/selftests/net/lib/csum.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/lib/csum.c b/tools/testing/selftests/net/lib/csum.c
index 27437590eeb53..e28884ce3ab39 100644
--- a/tools/testing/selftests/net/lib/csum.c
+++ b/tools/testing/selftests/net/lib/csum.c
@@ -707,7 +707,7 @@ static uint32_t recv_get_packet_csum_status(struct msghdr *msg)
 			      cm->cmsg_level, cm->cmsg_type);
 
 		if (cm->cmsg_len != CMSG_LEN(sizeof(struct tpacket_auxdata)))
-			error(1, 0, "cmsg: len=%lu expected=%lu",
+			error(1, 0, "cmsg: len=%zu expected=%zu",
 			      cm->cmsg_len, CMSG_LEN(sizeof(struct tpacket_auxdata)));
 
 		aux = (void *)CMSG_DATA(cm);
-- 
2.49.0

Hi Christophe

On 16/01/2026 10:48, Christophe Leroy (CS GROUP) wrote:
> Following warning is encountered when building selftests on powerpc/32.
> 
>   CC       csum
> csum.c: In function 'recv_get_packet_csum_status':
> csum.c:710:50: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
>   710 |                         error(1, 0, "cmsg: len=%lu expected=%lu",
>       |                                                ~~^
>       |                                                  |
>       |                                                  long unsigned int
>       |                                                %u
>   711 |                               cm->cmsg_len, CMSG_LEN(sizeof(struct tpacket_auxdata)));
>       |                               ~~~~~~~~~~~~
>       |                                 |
>       |                                 size_t {aka unsigned int}
> csum.c:710:63: warning: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'unsigned int' [-Wformat=]
>   710 |                         error(1, 0, "cmsg: len=%lu expected=%lu",
>       |                                                             ~~^
>       |                                                               |
>       |                                                               long unsigned int
>       |                                                             %u
> 
> cm->cmsg_len has type __kernel_size_t and CMSG() macro has the type
> returned by sizeof() which is size_t.
> 
> size_t is 'unsigned int' on some platforms and 'unsigned long' on
> other ones so use %zu instead of %lu.
> 
> This fixes commit 91a7de85600d ("selftests/net: add csum offload test").
> 
> Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime

> ---
> v2: Removed use %zu instead of %u and removed Fixes tag
> ---
>  tools/testing/selftests/net/lib/csum.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/net/lib/csum.c b/tools/testing/selftests/net/lib/csum.c
> index 27437590eeb53..e28884ce3ab39 100644
> --- a/tools/testing/selftests/net/lib/csum.c
> +++ b/tools/testing/selftests/net/lib/csum.c
> @@ -707,7 +707,7 @@ static uint32_t recv_get_packet_csum_status(struct msghdr *msg)
>  			      cm->cmsg_level, cm->cmsg_type);
>  
>  		if (cm->cmsg_len != CMSG_LEN(sizeof(struct tpacket_auxdata)))
> -			error(1, 0, "cmsg: len=%lu expected=%lu",
> +			error(1, 0, "cmsg: len=%zu expected=%zu",
>  			      cm->cmsg_len, CMSG_LEN(sizeof(struct tpacket_auxdata)));
>  
>  		aux = (void *)CMSG_DATA(cm);