linux-kernel - Re: [PATCH] [v2] iwlwifi: pcie: fix constant-conversion warning

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Message-ID: <CAK8P3a2hdrxz0rsDxWRu7B2Hfv-+Oo3yPndoLNH5KZw9Y2Knzg@mail.gmail.com>
Date:   Thu, 18 Nov 2021 13:28:24 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Luca Coelho <luciano.coelho@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Johannes Berg <johannes.berg@...el.com>
Cc:     Arnd Bergmann <arnd@...db.de>, kernel test robot <lkp@...el.com>,
        Yaara Baruch <yaara.baruch@...el.com>,
        Matti Gottlieb <matti.gottlieb@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] [v2] iwlwifi: pcie: fix constant-conversion warning

On Thu, Nov 11, 2021 at 8:31 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> clang points out a potential issue with integer overflow when
> the iwl_dev_info_table[] array is empty:
>
> drivers/net/wireless/intel/iwlwifi/pcie/drv.c:1344:42: error: implicit conversion from 'unsigned long' to 'int' changes value from 18446744073709551615 to -1 [-Werror,-Wconstant-conversion]
>         for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
>                ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
>
> This is still harmless, as the loop correctly terminates, but adding
> an extra range check makes that obvious to both readers and to the
> compiler.
>
> Fixes: 3f7320428fa4 ("iwlwifi: pcie: simplify iwl_pci_find_dev_info()")
> Reported-by: kernel test robot <lkp@...el.com>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Something went wrong on my end: I thought this was a clang warning and
that I had
fixed it because it didn't come back with my v2 patch. However I now see it in
my gcc-11 test builds, so I assume this was a gcc warning all along, and that
my patch does nothing. Please disregard it if you have not already applied it.

       Arnd