linux-kernel - Re: [PATCH] cfg80211: Change an 'else if' into an 'else' in cfg80211_calculate_bitrate

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Date:   Wed, 20 Mar 2019 12:10:26 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     linux-wireless@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] cfg80211: Change an 'else if' into an 'else' in
 cfg80211_calculate_bitrate_he

On Thu, Mar 07, 2019 at 04:57:35PM -0700, Nathan Chancellor wrote:
> When building with -Wsometimes-uninitialized, Clang warns:
> 
> net/wireless/util.c:1223:11: warning: variable 'result' is used
> uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
> 
> Clang can't evaluate at this point that WARN(1, ...) always returns true
> because __ret_warn_on is defined as !!(condition), which isn't
> immediately evaluated as 1. Change this branch to else so that it's
> clear to Clang that we intend to bail out here.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/382
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  net/wireless/util.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/wireless/util.c b/net/wireless/util.c
> index e4b8db5e81ec..75899b62bdc9 100644
> --- a/net/wireless/util.c
> +++ b/net/wireless/util.c
> @@ -1220,9 +1220,11 @@ static u32 cfg80211_calculate_bitrate_he(struct rate_info *rate)
>  	else if (rate->bw == RATE_INFO_BW_HE_RU &&
>  		 rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_26)
>  		result = rates_26[rate->he_gi];
> -	else if (WARN(1, "invalid HE MCS: bw:%d, ru:%d\n",
> -		      rate->bw, rate->he_ru_alloc))
> +	else {
> +		WARN(1, "invalid HE MCS: bw:%d, ru:%d\n",
> +		     rate->bw, rate->he_ru_alloc);
>  		return 0;
> +	}
>  
>  	/* now scale to the appropriate MCS */
>  	tmp = result;
> -- 
> 2.21.0
> 

Gentle ping (if there was a response to this, I didn't receive it). I
know I sent it in the middle of a merge window so I get if it slipped
through the cracks.

Thanks,
Nathan