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Date:   Thu, 7 Jul 2022 10:58:45 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Justin Stitt <justinstitt@google.com>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        David Howells <dhowells@redhat.com>,
        Marc Dionne <marc.dionne@auristor.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, linux-afs@lists.infradead.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
Subject: Re: [PATCH] net: rxrpc: fix clang -Wformat warning
Message-ID: <Ysce1Xur72MYp0/d@dev-arch.thelio-3990X>
References: <20220706235648.594609-1-justinstitt@google.com>
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In-Reply-To: <20220706235648.594609-1-justinstitt@google.com>
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Hi Justin,

On Wed, Jul 06, 2022 at 04:56:48PM -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@google.com>
> ---
>  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..aa180464ec37 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 %u]", ret, y);

Should this just become %x to keep printing it as a hexidecimal number?

Cheers,
Nathan

>  	return ret;
>  }
>  
> -- 
> 2.37.0.rc0.161.g10f37bed90-goog
>