linux-kernel - Re: [PATCH 1/2] ALSA: pcm: use "do {} while (0)" for empty macro

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Date:   Thu, 18 May 2017 16:39:33 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Arnd Bergmann" <arnd@...db.de>
Cc:     <alsa-devel@...a-project.org>, "Jaroslav Kysela" <perex@...ex.cz>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] ALSA: pcm: use "do {} while (0)" for empty macro

On Thu, 18 May 2017 15:35:54 +0200,
Arnd Bergmann wrote:
> 
> Recent compilers produce a harmless warning for the new pcm_call_notify()
> macro when CONFIG_SND_PCM_OSS is disabled:
> 
> sound/core/pcm.c: In function 'snd_pcm_free':
> sound/core/pcm.c:905:37: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
> 
> This turns the empty macro into a 'do {} while (0)' statement to avoid
> the warning.
> 
> Fixes: 58f30d650c7f ("ALSA: pcm: Build pcm notifier code conditionally")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks, applied both patches now.


Takashi

> ---
>  sound/core/pcm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/core/pcm.c b/sound/core/pcm.c
> index 24acbfb5c531..d30dba0ee688 100644
> --- a/sound/core/pcm.c
> +++ b/sound/core/pcm.c
> @@ -894,7 +894,7 @@ static void snd_pcm_free_stream(struct snd_pcm_str * pstr)
>  			_notify->call(pcm);				\
>  	} while (0)
>  #else
> -#define pcm_call_notify(pcm, call) /* NOP */
> +#define pcm_call_notify(pcm, call) do {} while (0)
>  #endif
>  
>  static int snd_pcm_free(struct snd_pcm *pcm)
> -- 
> 2.9.0
> 
>