linux-kernel - Re: [PATCH] perf tools: Replace zero-length array with flexible-array member

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Message-ID: <Yg+YEfv5vvT3RIxy@kernel.org>
Date:   Fri, 18 Feb 2022 09:58:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     cgel.zte@...il.com
Cc:     mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, adrian.hunter@...el.com,
        atrajeev@...ux.vnet.ibm.com, ak@...ux.intel.com,
        kan.liang@...ux.intel.com, deng.changcheng@....com.cn,
        german.gomez@....com, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH] perf tools: Replace zero-length array with
 flexible-array member

Em Fri, Feb 18, 2022 at 03:13:52AM +0000, cgel.zte@...il.com escreveu:
> From: Changcheng Deng <deng.changcheng@....com.cn>
> 
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use "flexible array members" for these cases. The older
> style of one-element or zero-length arrays should no longer be used.
> Reference:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Reported-by: Zeal Robot <zealci@....com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@....com.cn>

You can't do that as this will break the build as explained in that
patch e-mail thread.

Adrian provided an alternative patch that I have to process.

Thanks for the patch anyway,

- Arnaldo

> ---
>  tools/perf/util/event.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
> index cdd72e05fd28..320cbcd5b902 100644
> --- a/tools/perf/util/event.h
> +++ b/tools/perf/util/event.h
> @@ -308,7 +308,7 @@ struct perf_synth_intel_evt {
>  		};
>  		u32	cfe;
>  	};
> -	struct perf_synth_intel_evd evd[0];
> +	struct perf_synth_intel_evd evd[];
>  };
>  
>  struct perf_synth_intel_iflag_chg {
> -- 
> 2.25.1

-- 

- Arnaldo