Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 22 May 2023 17:52:32 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Ricardo =?iso-8859-1?Q?Ca=F1uelo?= <ricardo.canuelo@collabora.com>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Shreeya Patel <shreeya.patel@collabora.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        clang-built-linux <llvm@lists.linux.dev>,
        Bill Wendling <morbo@google.com>,
        Nathan Chancellor <nathan@kernel.org>,
        regressions@lists.linux.dev,
        "gustavo.padovan@collabora.com" <gustavo.padovan@collabora.com>,
        Guillaume Charles Tucker <guillaume.tucker@collabora.com>,
        denys.f@collabora.com, kernelci@lists.linux.dev
Subject: Re: [PATCH v4] Makefile.compiler: replace cc-ifversion with
 compiler-specific macros
Message-ID: <2023052247-bobtail-factsheet-d104@gregkh>
References: <CAKwvOd=4hBcU4fAkddU0b-GOZc9FzTZoj3PFW6ZZrX0jS8x+bg@mail.gmail.com>
 <17c91d37-7d9c-0df4-2438-2b30ca0b5777@collabora.com>
 <CAKwvOdk4QO8x_bs64fFRCsMu__AjhXd4Ew2KfgzQOb9Q3FMqSA@mail.gmail.com>
 <b5d0cf82-0e42-f6a1-c9f5-c145fdc4c622@collabora.com>
 <CAKwvOdkFxu9hYSL_RCXadpR0dQd1+dZmAUVXdfFiLUfxg4D_Xw@mail.gmail.com>
 <878rdlk9bi.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me>
 <CAKwvOd=8LVU+iANkFx18Wm1jg7gYiAXovAmo9t5ZZaVdMULn-Q@mail.gmail.com>
 <875y8ok9b5.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me>
 <CAKwvOdmJJibt6sHSp91v2s7BxUWBC6xG7F7+3C6gUxNMzZ2xRA@mail.gmail.com>
 <87353ok78h.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <87353ok78h.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me>
Precedence: bulk

On Mon, May 22, 2023 at 12:09:34PM +0200, Ricardo Ca?uelo wrote:
> On vie, may 19 2023 at 08:57:24, Nick Desaulniers <ndesaulniers@google.com> wrote:
> > It could be; if the link order was changed, it's possible that this
> > target may be hitting something along the lines of:
> > https://isocpp.org/wiki/faq/ctors#static-init-order i.e. the "static
> > initialization order fiasco"
> >
> > I'm struggling to think of how this appears in C codebases, but I
> > swear years ago I had a discussion with GKH (maybe?) about this. I
> > think I was playing with converting Kbuild to use Ninja rather than
> > Make; the resulting kernel image wouldn't boot because I had modified
> > the order the object files were linked in.  If you were to randomly
> > shuffle the object files in the kernel, I recall some hazard that may
> > prevent boot.
> 
> I thought that was specifically a C++ problem? But then again, the
> kernel docs explicitly say that the ordering of obj-y goals in kbuild is
> significant in some instances [1]:

Yes, it matters, you can not change it.  If you do, systems will break.
It is the only way we have of properly ordering our init calls within
the same "level".

thanks,

greg k-h