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From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"# 3.4.x" <stable@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Paul Mackerras <paulus@samba.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v3 2/3] powerpc: Avoid clang warnings around setjmp and longjmp
Date: Wed, 11 Sep 2019 13:55:52 -0700
Message-ID: <CAKwvOdn2vz0XGDQrbBiGFAp6vvBzmOgUH3GLkgGY4UAWLhhZUQ@mail.gmail.com> (raw)
In-Reply-To: <20190911182049.77853-3-natechancellor@gmail.com>

On Wed, Sep 11, 2019 at 11:21 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> Commit aea447141c7e ("powerpc: Disable -Wbuiltin-requires-header when
> setjmp is used") disabled -Wbuiltin-requires-header because of a warning
> about the setjmp and longjmp declarations.
>
> r367387 in clang added another diagnostic around this, complaining that
> there is no jmp_buf declaration.
>
> In file included from ../arch/powerpc/xmon/xmon.c:47:
> ../arch/powerpc/include/asm/setjmp.h:10:13: error: declaration of
> built-in function 'setjmp' requires the declaration of the 'jmp_buf'
> type, commonly provided in the header <setjmp.h>.
> [-Werror,-Wincomplete-setjmp-declaration]
> extern long setjmp(long *);
>             ^
> ../arch/powerpc/include/asm/setjmp.h:11:13: error: declaration of
> built-in function 'longjmp' requires the declaration of the 'jmp_buf'
> type, commonly provided in the header <setjmp.h>.
> [-Werror,-Wincomplete-setjmp-declaration]
> extern void longjmp(long *, long);
>             ^
> 2 errors generated.
>
> We are not using the standard library's longjmp/setjmp implementations
> for obvious reasons; make this clear to clang by using -ffreestanding
> on these files.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
https://godbolt.org/z/B2oQnl

>
> Cc: stable@vger.kernel.org # 4.14+
> Link: https://github.com/ClangBuiltLinux/linux/issues/625
> Link: https://github.com/llvm/llvm-project/commit/3be25e79477db2d31ac46493d97eca8c20592b07
> Suggested-by: Segher Boessenkool <segher@kernel.crashing.org>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>
> v1 -> v3:
>
> * Use -ffreestanding instead of outright disabling the warning because
>   it is legitimate.
>
> I skipped v2 because the first patch in the series already had a v2.
>
>  arch/powerpc/kernel/Makefile | 4 ++--
>  arch/powerpc/xmon/Makefile   | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index c9cc4b689e60..19f19c8c874b 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -5,8 +5,8 @@
>
>  CFLAGS_ptrace.o                += -DUTS_MACHINE='"$(UTS_MACHINE)"'
>
> -# Disable clang warning for using setjmp without setjmp.h header
> -CFLAGS_crash.o         += $(call cc-disable-warning, builtin-requires-header)
> +# Avoid clang warnings around longjmp/setjmp declarations
> +CFLAGS_crash.o         += -ffreestanding
>
>  ifdef CONFIG_PPC64
>  CFLAGS_prom_init.o     += $(NO_MINIMAL_TOC)
> diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
> index f142570ad860..c3842dbeb1b7 100644
> --- a/arch/powerpc/xmon/Makefile
> +++ b/arch/powerpc/xmon/Makefile
> @@ -1,8 +1,8 @@
>  # SPDX-License-Identifier: GPL-2.0
>  # Makefile for xmon
>
> -# Disable clang warning for using setjmp without setjmp.h header
> -subdir-ccflags-y := $(call cc-disable-warning, builtin-requires-header)
> +# Avoid clang warnings around longjmp/setjmp declarations
> +subdir-ccflags-y := -ffreestanding
>
>  GCOV_PROFILE := n
>  KCOV_INSTRUMENT := n
> --
> 2.23.0
>


-- 
Thanks,
~Nick Desaulniers

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11 18:20 [PATCH v3 0/3] LLVM/Clang fixes for pseries_defconfig Nathan Chancellor
2019-09-11 18:20 ` [PATCH v3 1/3] powerpc: Don't add -mabi= flags when building with Clang Nathan Chancellor
2019-09-11 18:20 ` [PATCH v3 2/3] powerpc: Avoid clang warnings around setjmp and longjmp Nathan Chancellor
2019-09-11 20:55   ` Nick Desaulniers [this message]
2019-09-11 18:20 ` [PATCH v3 3/3] powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp Nathan Chancellor
2019-09-11 21:01   ` Nick Desaulniers
2019-09-12  5:43     ` Nathan Chancellor
2019-09-12 17:30       ` Nick Desaulniers
2019-10-14  2:50 ` [PATCH v4 0/3] LLVM/Clang fixes for pseries_defconfig Nathan Chancellor
2019-10-14  2:50   ` [PATCH v4 1/3] powerpc: Don't add -mabi= flags when building with Clang Nathan Chancellor
2019-10-14  2:51   ` [PATCH v4 2/3] powerpc: Avoid clang warnings around setjmp and longjmp Nathan Chancellor
2019-10-14  2:51   ` [PATCH v4 3/3] powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp Nathan Chancellor
2019-10-14  9:35     ` Segher Boessenkool
2019-10-14 15:56       ` Nick Desaulniers
2019-10-14 19:11         ` Segher Boessenkool
2019-10-18 19:00           ` Nathan Chancellor
2019-10-18 20:02             ` Segher Boessenkool
2019-10-14 16:03   ` [PATCH v4 0/3] LLVM/Clang fixes for pseries_defconfig Nick Desaulniers

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