linux-kernel - Re: [PATCH] powerpc: Avoid clang warnings around setjmp and longjmp

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Message-ID: <20190903055553.GC60296@archlinux-threadripper>
Date:   Mon, 2 Sep 2019 22:55:53 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH] powerpc: Avoid clang warnings around setjmp and longjmp

On Thu, Aug 29, 2019 at 09:59:48AM +0000, David Laight wrote:
> From: Nathan Chancellor
> > Sent: 28 August 2019 19:45
> ...
> > However, I think that -fno-builtin-* would be appropriate here because
> > we are providing our own setjmp implementation, meaning clang should not
> > be trying to do anything with the builtin implementation like building a
> > declaration for it.
> 
> Isn't implementing setjmp impossible unless you tell the compiler that
> you function is 'setjmp-like' ?

No idea, PowerPC is the only architecture that does such a thing.

https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/tree/arch/powerpc/kernel/misc.S#n43

Goes back all the way to before git history (all the way to ppc64's
addition actually):

https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=61542216fa90397a2e70c46583edf26bc81994df

https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/arch/ppc64/xmon/setjmp.c?id=5f12b0bff93831620218e8ed3970903ecb7861ce

I would just like this warning fixed given that PowerPC builds with
-Werror by default so it is causing a build failure in our CI.

Cheers,
Nathan