linux-kernel - Re: [PATCH] asm-generic: percpu: avoid Wshadow warning

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Date:   Tue, 27 Oct 2020 00:02:21 +0000
From:   Dennis Zhou <dennis@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Christoph Lameter <cl@...ux.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] asm-generic: percpu: avoid Wshadow warning

Hello,

On Mon, Oct 26, 2020 at 04:53:48PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Nesting macros that use the same local variable names causes
> warnings when building with "make W=2":
> 
> include/asm-generic/percpu.h:117:14: warning: declaration of '__ret' shadows a previous local [-Wshadow]
> include/asm-generic/percpu.h:126:14: warning: declaration of '__ret' shadows a previous local [-Wshadow]
> 
> These are fairly harmless, but since the warning comes from
> a global header, the warning happens every time the headers
> are included, which is fairly annoying.
> 
> Rename the variables to avoid shadowing and shut up the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  include/asm-generic/percpu.h | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
> index 35e4a53b83e6..6432a7fade91 100644
> --- a/include/asm-generic/percpu.h
> +++ b/include/asm-generic/percpu.h
> @@ -114,21 +114,21 @@ do {									\
>  
>  #define __this_cpu_generic_read_nopreempt(pcp)				\
>  ({									\
> -	typeof(pcp) __ret;						\
> +	typeof(pcp) ___ret;						\
>  	preempt_disable_notrace();					\
> -	__ret = READ_ONCE(*raw_cpu_ptr(&(pcp)));			\
> +	___ret = READ_ONCE(*raw_cpu_ptr(&(pcp)));			\
>  	preempt_enable_notrace();					\
> -	__ret;								\
> +	___ret;								\
>  })
>  
>  #define __this_cpu_generic_read_noirq(pcp)				\
>  ({									\
> -	typeof(pcp) __ret;						\
> -	unsigned long __flags;						\
> -	raw_local_irq_save(__flags);					\
> -	__ret = raw_cpu_generic_read(pcp);				\
> -	raw_local_irq_restore(__flags);					\
> -	__ret;								\
> +	typeof(pcp) ___ret;						\
> +	unsigned long ___flags;						\
> +	raw_local_irq_save(___flags);					\
> +	___ret = raw_cpu_generic_read(pcp);				\
> +	raw_local_irq_restore(___flags);				\
> +	___ret;								\
>  })
>  
>  #define this_cpu_generic_read(pcp)					\
> -- 
> 2.27.0
> 

I've applied this to percpu#for-5.10-fixes.

Thanks,
Dennis