netdev - Re: [PATCH] iwlwifi: mvm: fix clang -Wformat warnings

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Date:   Mon, 18 Jul 2022 13:58:05 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Gregory Greenman <gregory.greenman@...el.com>,
        Kalle Valo <kvalo@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Avraham Stern <avraham.stern@...el.com>,
        Miri Korenblit <miriam.rachel.korenblit@...el.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] iwlwifi: mvm: fix clang -Wformat warnings

On Mon, Jul 11, 2022 at 3:29 PM Justin Stitt <justinstitt@...gle.com> wrote:
>
> When building with Clang we encounter these warnings:
> | drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c:1108:47: error:
> | format specifies type 'unsigned char' but the argument has type 's16'
> | (aka 'short') [-Werror,-Wformat] IWL_DEBUG_INFO(mvm, "\tburst index:
> | %hhu\n", res->ftm.burst_index);
> -
> | drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c:1111:47: error:
> | format specifies type 'unsigned char' but the argument has type 's32'
> | (aka 'int') [-Werror,-Wformat] IWL_DEBUG_INFO(mvm, "\trssi spread:
> | %hhu\n", res->ftm.rssi_spread);
>
> The previous format specifier `%hhu` describes a u8 but our arguments
> are wider than this which means bits are potentially being lost.
>
> Variadic functions (printf-like) undergo default argument promotion.
> Documentation/core-api/printk-formats.rst specifically recommends using
> the promoted-to-type's format flag.
>
> As per C11 6.3.1.1:
> (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int
> can represent all values of the original type ..., the value is
> converted to an int; otherwise, it is converted to an unsigned int.
> These are called the integer promotions.` Thus it makes sense to change
> `%hhu` to `%d` for both instances of the warning.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/378
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c b/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c
> index 430044bc4755..e8702184c950 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c
> @@ -1105,10 +1105,10 @@ static void iwl_mvm_debug_range_resp(struct iwl_mvm *mvm, u8 index,
>         IWL_DEBUG_INFO(mvm, "\tstatus: %d\n", res->status);
>         IWL_DEBUG_INFO(mvm, "\tBSSID: %pM\n", res->addr);
>         IWL_DEBUG_INFO(mvm, "\thost time: %llu\n", res->host_time);
> -       IWL_DEBUG_INFO(mvm, "\tburst index: %hhu\n", res->ftm.burst_index);
> +       IWL_DEBUG_INFO(mvm, "\tburst index: %d\n", res->ftm.burst_index);
>         IWL_DEBUG_INFO(mvm, "\tsuccess num: %u\n", res->ftm.num_ftmr_successes);
>         IWL_DEBUG_INFO(mvm, "\trssi: %d\n", res->ftm.rssi_avg);
> -       IWL_DEBUG_INFO(mvm, "\trssi spread: %hhu\n", res->ftm.rssi_spread);
> +       IWL_DEBUG_INFO(mvm, "\trssi spread: %d\n", res->ftm.rssi_spread);
>         IWL_DEBUG_INFO(mvm, "\trtt: %lld\n", res->ftm.rtt_avg);
>         IWL_DEBUG_INFO(mvm, "\trtt var: %llu\n", res->ftm.rtt_variance);
>         IWL_DEBUG_INFO(mvm, "\trtt spread: %llu\n", res->ftm.rtt_spread);
> --
> 2.37.0.144.g8ac04bfd2-goog
>


-- 
Thanks,
~Nick Desaulniers