netdev - Re: [PATCH v2] net: rxrpc: fix clang -Wformat warning

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Date:   Thu, 7 Jul 2022 11:24:03 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     davem@...emloft.net, dhowells@...hat.com, edumazet@...gle.com,
        kuba@...nel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        marc.dionne@...istor.com, ndesaulniers@...gle.com,
        netdev@...r.kernel.org, pabeni@...hat.com, trix@...hat.com
Subject: Re: [PATCH v2] net: rxrpc: fix clang -Wformat warning

On Thu, Jul 07, 2022 at 11:20:52AM -0700, Justin Stitt wrote:
> When building with Clang we encounter this warning:
> | net/rxrpc/rxkad.c:434:33: error: format specifies type 'unsigned short'
> | but the argument has type 'u32' (aka 'unsigned int') [-Werror,-Wformat]
> | _leave(" = %d [set %hx]", ret, y);
> 
> y is a u32 but the format specifier is `%hx`. Going from unsigned int to
> short int results in a loss of data. This is surely not intended
> behavior. If it is intended, the warning should be suppressed through
> other means.
> 
> This patch should get us closer to the goal of enabling the -Wformat
> flag for Clang builds.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/378
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
> diff from v1 -> v2: 
> * Change format specifier from %u to %x to properly represent hexadecimal.
> 
>  net/rxrpc/rxkad.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
> index 08aab5c01437..258917a714c8 100644
> --- a/net/rxrpc/rxkad.c
> +++ b/net/rxrpc/rxkad.c
> @@ -431,7 +431,7 @@ static int rxkad_secure_packet(struct rxrpc_call *call,
>  		break;
>  	}
>  
> -	_leave(" = %d [set %hx]", ret, y);
> +	_leave(" = %d [set %x]", ret, y);
>  	return ret;
>  }
>  
> -- 
> 2.37.0.rc0.161.g10f37bed90-goog
>