linux-kernel - Re: [PATCH -next] iwlwifi: dbg: work around clang bug by marking debug strings static

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Message-ID: <da053a97d771eff0ad8db37e644108ed2fad25a3.camel@coelho.fi>
Date:   Wed, 17 Jul 2019 00:14:49 +0300
From:   Luca Coelho <luca@...lho.fi>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Joe Perches <joe@...ches.com>,
        Kalle Valo <kvalo@...eaurora.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Shahar S Matityahu <shahar.s.matityahu@...el.com>,
        Sara Sharon <sara.sharon@...el.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH -next] iwlwifi: dbg: work around clang bug by marking
 debug strings static

On Tue, 2019-07-16 at 10:28 -0700, Nick Desaulniers wrote:
> On Thu, Jul 11, 2019 at 7:15 PM Joe Perches <joe@...ches.com> wrote:
> > On Thu, 2019-07-11 at 17:17 -0700, Nick Desaulniers wrote:
> > > Commit r353569 in prerelease Clang-9 is producing a linkage failure:
> > > 
> > > ld: drivers/net/wireless/intel/iwlwifi/fw/dbg.o:
> > > in function `_iwl_fw_dbg_apply_point':
> > > dbg.c:(.text+0x827a): undefined reference to `__compiletime_assert_2387'
> > > 
> > > when the following configs are enabled:
> > > - CONFIG_IWLWIFI
> > > - CONFIG_IWLMVM
> > > - CONFIG_KASAN
> > > 
> > > Work around the issue for now by marking the debug strings as `static`,
> > > which they probably should be any ways.
> > > 
> > > Link: https://bugs.llvm.org/show_bug.cgi?id=42580
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/580
> > > Reported-by: Arnd Bergmann <arnd@...db.de>
> > > Reported-by: Nathan Chancellor <natechancellor@...il.com>
> > > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > > ---
> > >  drivers/net/wireless/intel/iwlwifi/fw/dbg.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/net/wireless/intel/iwlwifi/fw/dbg.c b/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
> > > index e411ac98290d..f8c90ea4e9b4 100644
> > > --- a/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
> > > +++ b/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
> > > @@ -2438,7 +2438,7 @@ static void iwl_fw_dbg_info_apply(struct iwl_fw_runtime *fwrt,
> > >  {
> > >       u32 img_name_len = le32_to_cpu(dbg_info->img_name_len);
> > >       u32 dbg_cfg_name_len = le32_to_cpu(dbg_info->dbg_cfg_name_len);
> > > -     const char err_str[] =
> > > +     static const char err_str[] =
> > >               "WRT: ext=%d. Invalid %s name length %d, expected %d\n";
> > 
> > Better still would be to use the format string directly
> > in both locations instead of trying to deduplicate it
> > via storing it into a separate pointer.
> > 
> > Let the compiler/linker consolidate the format.
> > It's smaller object code, allows format/argument verification,
> > and is simpler for humans to understand.
> 
> Whichever Kalle prefers, I just want my CI green again.

We already changed this in a later internal patch, which will reach the
mainline (-next) soon.  So let's skip this for now.

--
Cheers,
Luca.