Message-ID: <0e9cbdd7-1875-35bd-4d1d-81b7dff9df7c@infradead.org>
Date:   Sun, 22 Jan 2023 13:10:48 -0800
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Subject: Re: [PATCH v3 1/1] arch/sh: avoid spurious sizeof-pointer-div warning
Content-Language: en-US
To:     Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>,
        linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org,
        Segher Boessenkool <segher@kernel.crashing.org>,
        Rich Felker <dalias@libc.org>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
References: <8dc791f9-3b44-e81d-6877-c21b9180c48a@mkarcher.dialup.fu-berlin.de>
From:   Randy Dunlap <rdunlap@infradead.org>
In-Reply-To: <8dc791f9-3b44-e81d-6877-c21b9180c48a@mkarcher.dialup.fu-berlin.de>
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Precedence: bulk


On 1/22/23 12:51, Michael Karcher wrote:
> Gcc warns about the pattern sizeof(void*)/sizeof(void), as it looks like
> the abuse of a pattern to calculate the array size. This pattern appears
> in the unevaluated part of the ternary operator in _INTC_ARRAY if the
> parameter is NULL.
> 
> The replacement uses an alternate approach to return 0 in case of NULL
> which does not generate the pattern sizeof(void*)/sizeof(void), but still
> emits the warning if _INTC_ARRAY is called with a nonarray parameter.
> 
> This patch is required for successful compilation with -Werror enabled.
> 
> The idea to use _Generic for type distinction is taken from Comment #7
> in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483 by Jakub Jelinek
> 
> Signed-off-by: Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>
> ---
> History:
> v3:
>   - I had a stern discussion with Thunderbird about not mangling the
>     space characters in my email, and I hope spaces get sent as standard
>     spaces now

Looks good now. Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested


> v2:
>   - improve title and remove mostly redundant first sentence of the
>     description
>   - adjust formatting of the _Generic construction
> 
> diff --git a/include/linux/sh_intc.h b/include/linux/sh_intc.h
> index c255273b0281..98d1da0d8e36 100644
> --- a/include/linux/sh_intc.h
> +++ b/include/linux/sh_intc.h
> @@ -97,7 +97,9 @@ struct intc_hw_desc {
>      unsigned int nr_subgroups;
>  };
> 
> -#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
> +#define _INTC_ARRAY(a) a, sizeof(a) / (_Generic(a, \
> +                                       typeof(NULL):  (size_t)-1, \
> +                                       default:       sizeof(*a)))
> 
>  #define INTC_HW_DESC(vectors, groups, mask_regs,    \
>               prio_regs,    sense_regs, ack_regs)    \
> 
> 

-- 
~Randy