linux-kernel - Re: [PATCH v2 2/2] powerpc/math-emu: Remove -w build flag and fix warnings

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Message-ID: <20220902162728.GS25951@gate.crashing.org>
Date:   Fri, 2 Sep 2022 11:27:28 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH v2 2/2] powerpc/math-emu: Remove -w build flag and fix warnings

Hi!

On Fri, Sep 02, 2022 at 09:11:48AM -0700, Nathan Chancellor wrote:
> On Fri, Sep 02, 2022 at 10:59:54AM -0500, Segher Boessenkool wrote:
> > Maybe add -Wno-implicit-fallthrough?  This code is a copy from outside
> > the kernel, no one has ever wanted to maintain it, if nothing else (the
> > more politically correct formulation is "we cannot as easily pick up
> > improvements from upstream if we modify stuff").
> 
> Sure, we could do something like this if you preferred:
> 
> diff --git a/arch/powerpc/math-emu/Makefile b/arch/powerpc/math-emu/Makefile
> index 26fef2e5672e..ed775747a2a5 100644
> --- a/arch/powerpc/math-emu/Makefile
> +++ b/arch/powerpc/math-emu/Makefile
> @@ -16,3 +16,7 @@ obj-$(CONFIG_SPE)		+= math_efp.o
>  
>  CFLAGS_fabs.o = -fno-builtin-fabs
>  CFLAGS_math.o = -fno-builtin-fabs
> +
> +ifdef CONFIG_CC_IS_CLANG
> +ccflags-remove-y := $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
> +endif

That is a GCC warning as well.  It needs some $(call cc-option ...)
thing then, though (GCC versions of more than two or so years ago are
supported as well).

> At the same time, I see other modifications to these files that appear
> to be for the kernel only so I suspect that this is already in the "we
> cannot as easily pick up improvements from upstream" category,
> regardless of that diff.

So maybe someone should really maintain this stuff, bring it up to some
reasonably modern state?  :-)


Segher