linux-kernel - Re: [PATCH] Net: psock_tpacket: Fix null argument warning in walk

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Message-ID: <willemdebruijn.kernel.2b5618e3b2d34@gmail.com>
Date: Wed, 24 Sep 2025 16:21:07 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Wake Liu <wakel@...gle.com>, 
 "David S . Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Shuah Khan <shuah@...nel.org>, 
 netdev@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Cc: Simon Horman <horms@...nel.org>, 
 Wake Liu <wakel@...gle.com>
Subject: Re: [PATCH] Net: psock_tpacket: Fix null argument warning in walk_tx

[PATCH net-next]

Wake Liu wrote:
> The sendto() call in walk_tx() was passing NULL as the buffer argument,
> which can trigger a -Wnonnull warning with some compilers.
> 
> Although the size is 0 and no data is actually sent, passing a null
> pointer is technically incorrect.
> 
> This commit changes NULL to an empty string literal ("") to satisfy the
> non-null argument requirement and fix the compiler warning.

Which library defines this argument as nonnull?

I'm not aware of this restriction in the POSIX standard.
This pattern is quite common.

> 
> Signed-off-by: Wake Liu <wakel@...gle.com>
> ---
>  tools/testing/selftests/net/psock_tpacket.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/net/psock_tpacket.c b/tools/testing/selftests/net/psock_tpacket.c
> index 221270cee3ea..0c24adbb292e 100644
> --- a/tools/testing/selftests/net/psock_tpacket.c
> +++ b/tools/testing/selftests/net/psock_tpacket.c
> @@ -470,7 +470,7 @@ static void walk_tx(int sock, struct ring *ring)
>  
>  	bug_on(total_packets != 0);
>  
> -	ret = sendto(sock, NULL, 0, 0, NULL, 0);
> +	ret = sendto(sock, "", 0, 0, NULL, 0);
>  	if (ret == -1) {
>  		perror("sendto");
>  		exit(1);
> -- 
> 2.51.0.534.gc79095c0ca-goog
>