From: Nathan Chancellor <natechancellor@gmail.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com, Qian Cai <cai@lca.pw>,
will@kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64/cache: silence -Woverride-init warnings
Date: Thu, 8 Aug 2019 10:09:16 -0700 [thread overview]
Message-ID: <20190808170916.GA32668@archlinux-threadripper> (raw)
In-Reply-To: <20190808103808.GC46901@lakrids.cambridge.arm.com>
On Thu, Aug 08, 2019 at 11:38:08AM +0100, Mark Rutland wrote:
> On Wed, Aug 07, 2019 at 11:29:16PM -0400, Qian Cai wrote:
> > The commit 155433cb365e ("arm64: cache: Remove support for ASID-tagged
> > VIVT I-caches") introduced some compiation warnings from GCC (and
> > Clang) with -Winitializer-overrides),
> >
> > 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. Since
> > arm64 developers are keen to keep the style of initializing a static
> > array with a non-zero pattern first, just disable those warnings for
> > both GCC and Clang of this file.
> >
> > Fixes: 155433cb365e ("arm64: cache: Remove support for ASID-tagged VIVT I-caches")
> > Signed-off-by: Qian Cai <cai@lca.pw>
>
> This is _not_ a fix, and should not require backporting to stable trees.
>
> What about all the other instances that we have in mainline?
>
> I really don't think that we need to go down this road; we're just going
> to end up adding this to every file that happens to include a header
> using this scheme...
>
> Please just turn this off by default for clang.
>
> If we want to enable this, we need a mechanism to permit overridable
> assignments as we use range initializers for.
>
> Thanks,
> Mark.
>
For what it's worth, this is disabled by default for clang in the
kernel:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/Makefile.extrawarn?h=v5.3-rc3#n69
It only becomes visible with clang at W=1 because that section doesn't
get applied. It becomes visible with GCC at W=1 because of -Wextra.
Cheers,
Nathan
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linux-arm-kernel@lists.infradead.org
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WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <natechancellor@gmail.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Qian Cai <cai@lca.pw>,
will@kernel.org, catalin.marinas@arm.com,
linux-arm-kernel@lists.infradead.org,
clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64/cache: silence -Woverride-init warnings
Date: Thu, 8 Aug 2019 10:09:16 -0700 [thread overview]
Message-ID: <20190808170916.GA32668@archlinux-threadripper> (raw)
In-Reply-To: <20190808103808.GC46901@lakrids.cambridge.arm.com>
On Thu, Aug 08, 2019 at 11:38:08AM +0100, Mark Rutland wrote:
> On Wed, Aug 07, 2019 at 11:29:16PM -0400, Qian Cai wrote:
> > The commit 155433cb365e ("arm64: cache: Remove support for ASID-tagged
> > VIVT I-caches") introduced some compiation warnings from GCC (and
> > Clang) with -Winitializer-overrides),
> >
> > 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. Since
> > arm64 developers are keen to keep the style of initializing a static
> > array with a non-zero pattern first, just disable those warnings for
> > both GCC and Clang of this file.
> >
> > Fixes: 155433cb365e ("arm64: cache: Remove support for ASID-tagged VIVT I-caches")
> > Signed-off-by: Qian Cai <cai@lca.pw>
>
> This is _not_ a fix, and should not require backporting to stable trees.
>
> What about all the other instances that we have in mainline?
>
> I really don't think that we need to go down this road; we're just going
> to end up adding this to every file that happens to include a header
> using this scheme...
>
> Please just turn this off by default for clang.
>
> If we want to enable this, we need a mechanism to permit overridable
> assignments as we use range initializers for.
>
> Thanks,
> Mark.
>
For what it's worth, this is disabled by default for clang in the
kernel:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/Makefile.extrawarn?h=v5.3-rc3#n69
It only becomes visible with clang at W=1 because that section doesn't
get applied. It becomes visible with GCC at W=1 because of -Wextra.
Cheers,
Nathan
next prev parent reply other threads:[~2019-08-08 17:09 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 3:29 [PATCH] arm64/cache: silence -Woverride-init warnings Qian Cai
2019-08-08 3:29 ` Qian Cai
2019-08-08 4:50 ` Nathan Chancellor
2019-08-08 4:50 ` Nathan Chancellor
2019-08-08 10:38 ` Mark Rutland
2019-08-08 10:38 ` Mark Rutland
2019-08-08 17:09 ` Nathan Chancellor [this message]
2019-08-08 17:09 ` Nathan Chancellor
2019-08-09 8:32 ` Explicitly marking initializer overrides (was "Re: [PATCH] arm64/cache: silence -Woverride-init warnings") Mark Rutland
2019-08-09 8:32 ` Mark Rutland
2019-08-09 11:31 ` Robin Murphy
2019-08-09 11:31 ` Robin Murphy
2019-08-14 17:26 ` Nathan Chancellor
2019-08-14 17:26 ` Nathan Chancellor
2019-08-08 22:18 ` [PATCH] arm64/cache: silence -Woverride-init warnings Qian Cai
2019-08-08 22:18 ` Qian Cai
2019-08-09 8:53 ` Mark Rutland
2019-08-09 8:53 ` Mark Rutland
2019-08-09 22:14 ` Nick Desaulniers
2019-08-09 22:14 ` Nick Desaulniers
2019-08-09 9:04 ` Will Deacon
2019-08-09 9:04 ` Will Deacon
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