linux-kernel - Re: [PATCH] arm64/cache: fix -Woverride-init compiler warnings

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Message-ID: <20190805095256.ocgdb2yfhnbdz6kw@willie-the-truck>
Date:   Mon, 5 Aug 2019 10:52:56 +0100
From:   Will Deacon <will@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     catalin.marinas@....com, mark.rutland@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/cache: fix -Woverride-init compiler warnings

On Fri, Aug 02, 2019 at 11:32:24AM -0400, Qian Cai wrote:
> The commit 155433cb365e ("arm64: cache: Remove support for ASID-tagged
> VIVT I-caches") introduced some compiation warnings from GCC,
> 
> arch/arm64/kernel/cpuinfo.c:38:26: warning: initialized field
> overwritten [-Woverride-init]
>   [ICACHE_POLICY_VIPT]  = "VIPT",
>                           ^~~~~~
> arch/arm64/kernel/cpuinfo.c:38:26: note: (near initialization for
> 'icache_policy_str[2]')
> arch/arm64/kernel/cpuinfo.c:39:26: warning: initialized field
> overwritten [-Woverride-init]
>   [ICACHE_POLICY_PIPT]  = "PIPT",
>                           ^~~~~~
> arch/arm64/kernel/cpuinfo.c:39:26: note: (near initialization for
> 'icache_policy_str[3]')
> arch/arm64/kernel/cpuinfo.c:40:27: warning: initialized field
> overwritten [-Woverride-init]
>   [ICACHE_POLICY_VPIPT]  = "VPIPT",
>                            ^~~~~~~
> arch/arm64/kernel/cpuinfo.c:40:27: note: (near initialization for
> 'icache_policy_str[0]')
> 
> because it initializes icache_policy_str[0 ... 3] twice.
> 
> Fixes: 155433cb365e ("arm64: cache: Remove support for ASID-tagged VIVT I-caches")
> Signed-off-by: Qian Cai <cai@....pw>
> ---
>  arch/arm64/kernel/cpuinfo.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 876055e37352..193b38da8d96 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -34,10 +34,10 @@
>  static struct cpuinfo_arm64 boot_cpu_data;
>  
>  static char *icache_policy_str[] = {
> -	[0 ... ICACHE_POLICY_PIPT]	= "RESERVED/UNKNOWN",
> +	[ICACHE_POLICY_VPIPT]		= "VPIPT",
> +	[ICACHE_POLICY_VPIPT + 1]	= "RESERVED/UNKNOWN",
>  	[ICACHE_POLICY_VIPT]		= "VIPT",
>  	[ICACHE_POLICY_PIPT]		= "PIPT",
> -	[ICACHE_POLICY_VPIPT]		= "VPIPT",

I really don't like this patch. Using "[0 ... MAXIDX] = <default>" is a
useful idiom and I think the code is more error-prone the way you have
restructured it.

Why are you passing -Woverride-init to the compiler anyway? There's only
one Makefile that references that option, and it's specific to a pinctrl
driver.

Will