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

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Message-ID: <1840089.1657273144@warthog.procyon.org.uk>
Date:   Fri, 08 Jul 2022 10:39:04 +0100
From:   David Howells <dhowells@...hat.com>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     dhowells@...hat.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        marc.dionne@...istor.com, nathan@...nel.org,
        ndesaulniers@...gle.com, netdev@...r.kernel.org, pabeni@...hat.com,
        trix@...hat.com
Subject: Re: [PATCH v2] net: rxrpc: fix clang -Wformat warning

Justin Stitt <justinstitt@...gle.com> wrote:

> 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.

Yeah, y is reduced to a 16-bit number so that it can be used in the protocol,
but the type is still 32-bit because that's needed for the calculation.  An
alternative would be to print sp->hdr.cksum since that's the value that will
appear on the wire, but I've no objection to this change either.

> 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>

Acked-by: David Howells <dhowells@...hat.com>