From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id D4F7813AE5;
	Mon, 22 May 2023 16:52:50 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28B6CC433D2;
	Mon, 22 May 2023 16:52:50 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org;
	s=korg; t=1684774370;
	bh=vOQbWWEEqd8EQVksWSFEy4waMaZII1vIhTX3SzTbbko=;
	h=Date:From:To:Cc:Subject:References:In-Reply-To:From;
	b=e3MLFpG2OoR6zPuYXlOFRm68JelSBH0QDndXPwKeHRgL9+reSIMdQe6CNgI/cfc9f
	 miDxNritVnfcvqwuHDuMk5Rn/GbaQD+om4+8MowbFMZnHWSN9ZE0shhe5sjt+9/A0J
	 BNSZ2iolJWZw8v1cc/eom6LTzfCJ1k1NevOLgfiI=
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>
Precedence: bulk
X-Mailing-List: llvm@lists.linux.dev
List-Id: <llvm.lists.linux.dev>
List-Subscribe: <mailto:llvm+subscribe@lists.linux.dev>
List-Unsubscribe: <mailto:llvm+unsubscribe@lists.linux.dev>
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>

On Mon, May 22, 2023 at 12:09:34PM +0200, Ricardo Cañuelo 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