linux-kernel - Re: [PATCH] tools/bootconfig: Fix wrong __VA_ARGS_

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Message-ID: <87y2tazs7h.fsf@mpe.ellerman.id.au>
Date:   Mon, 10 Feb 2020 20:50:42 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] tools/bootconfig: Fix wrong __VA_ARGS__ usage

Masami Hiramatsu <mhiramat@...nel.org> writes:
> Since printk() wrapper macro uses __VA_ARGS__ without
> "##" prefix, it causes a build error if there is no
> variable arguments (e.g. only fmt is specified.)
> To fix this error, use ##__VA_ARGS__ instead of
> __VAR_ARGS__.
>
> Fixes: 950313ebf79c ("tools: bootconfig: Add bootconfig command")
> Reported-by: Michael Ellerman <mpe@...erman.id.au>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  tools/bootconfig/include/linux/printk.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/bootconfig/include/linux/printk.h b/tools/bootconfig/include/linux/printk.h
> index 017bcd6912a5..e978a63d3222 100644
> --- a/tools/bootconfig/include/linux/printk.h
> +++ b/tools/bootconfig/include/linux/printk.h
> @@ -7,7 +7,7 @@
>  /* controllable printf */
>  extern int pr_output;
>  #define printk(fmt, ...)	\
> -	(pr_output ? printf(fmt, __VA_ARGS__) : 0)
> +	(pr_output ? printf(fmt, ##__VA_ARGS__) : 0)
>  
>  #define pr_err printk
>  #define pr_warn	printk

Tested-by: Michael Ellerman <mpe@...erman.id.au>

cheers