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From:   Peter Maydell <peter.maydell@linaro.org>
Date:   Mon, 26 Oct 2020 17:13:30 +0000
Message-ID: <CAFEAcA_sA+sAneWwi8ZtN1WmHhcHte0k_3_JcDybYWviW_18qg@mail.gmail.com>
Subject: Re: [PATCH 4/4] arm64: traps: fix -Woverride-init warnings
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Arnd Bergmann <arnd@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
        Christoffer Dall <christoffer.dall@linaro.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Mark Brown <broonie@kernel.org>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        James Morse <james.morse@arm.com>,
        Amit Daniel Kachhap <amit.kachhap@arm.com>,
        Gavin Shan <gshan@redhat.com>,
        arm-mail-list <linux-arm-kernel@lists.infradead.org>,
        lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, 26 Oct 2020 at 16:23, Mark Rutland <mark.rutland@arm.com> wrote:
>
> Hi Arnd,
>
> On Mon, Oct 26, 2020 at 05:03:31PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > There are many warnings in this file when we re-enable the
> > Woverride-init flag:
> >
> > arch/arm64/kernel/traps.c:704:26: warning: initialized field overwritten [-Woverride-init]
> >   704 |  [ESR_ELx_EC_UNKNOWN]  = "Unknown/Uncategorized",
> >       |                          ^~~~~~~~~~~~~~~~~~~~~~~
> > arch/arm64/kernel/traps.c:704:26: note: (near initialization for 'esr_class_str[0]')
> > arch/arm64/kernel/traps.c:705:22: warning: initialized field overwritten [-Woverride-init]
> >   705 |  [ESR_ELx_EC_WFx]  = "WFI/WFE",
> >       |                      ^~~~~~~~~
> >
> > This is harmless since they are only informational strings,
> > but it's easy to change the code to ignore missing initialization
> > and instead warn about possible duplicate initializers.
>
> This has come up before, and IMO the warning is more hindrance than
> helpful, given the prevalance of spurious warnings, and the (again IMO)
> the rework needed to avoid those making the code harder to reason about

FWIW in QEMU we turn the clang version of this off with
-Wno-initializer-overrides because we agree that the code is
fine and the compiler is being unhelpful in this case. (There's
a reason gcc doesn't put it in -Wall.)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91688 is a request
for something that would catch bugs without breaking ranged-array
initializer syntax usage, but the gcc devs don't seem to have
responded.

thanks
-- PMM