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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Nick Desaulniers <ndesaulniers@google.com>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        clang-built-linux@googlegroups.com, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org,
        Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH 1/3] powerpc: boot: include compiler_attributes.h
In-Reply-To: <20201116043532.4032932-2-ndesaulniers@google.com>
References: <20201116043532.4032932-1-ndesaulniers@google.com> <20201116043532.4032932-2-ndesaulniers@google.com>
Date:   Wed, 18 Nov 2020 10:46:06 +1100
Message-ID: <87o8jv35tt.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Nick Desaulniers <ndesaulniers@google.com> writes:
> The kernel uses `-include` to include include/linux/compiler_types.h
> into all translation units (see scripts/Makefile.lib), which #includes
> compiler_attributes.h.
>
> arch/powerpc/boot/ uses different compiler flags from the rest of the
> kernel. As such, it doesn't contain the definitions from these headers,
> and redefines a few that it needs.
>
> For the purpose of enabling -Wimplicit-fallthrough for ppc, include
> compiler_types.h via `-include`.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/236
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> We could just `#include "include/linux/compiler_types.h"` in the few .c
> sources used from lib/ (there are proper header guards in
> compiler_types.h).
>
> It was also noted in 6a9dc5fd6170 that we could -D__KERNEL__ and
> -include compiler_types.h like the main kernel does, though testing that
> produces a whole sea of warnings to cleanup. This approach is minimally
> invasive.
>
>  arch/powerpc/boot/Makefile     | 1 +
>  arch/powerpc/boot/decompress.c | 1 -
>  2 files changed, 1 insertion(+), 1 deletion(-)

Acked-by: Michael Ellerman <mpe@ellerman.id.au>

cheers