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Message-ID: <0e9cbdd7-1875-35bd-4d1d-81b7dff9df7c@infradead.org>
Date: Sun, 22 Jan 2023 13:10:48 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>,
linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
Segher Boessenkool <segher@...nel.crashing.org>,
Rich Felker <dalias@...c.org>,
Yoshinori Sato <ysato@...rs.sourceforge.jp>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Subject: Re: [PATCH v3 1/1] arch/sh: avoid spurious sizeof-pointer-div warning
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@...rcher.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@...radead.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
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