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From: Nathan Chancellor <natechancellor@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	clang-built-linux@googlegroups.com,
	Nathan Chancellor <natechancellor@gmail.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v3 2/3] powerpc: Avoid clang warnings around setjmp and longjmp
Date: Wed, 11 Sep 2019 11:20:51 -0700
Message-ID: <20190911182049.77853-3-natechancellor@gmail.com> (raw)
In-Reply-To: <20190911182049.77853-1-natechancellor@gmail.com>

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.

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


  parent reply index

Thread overview: 16+ 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 ` Nathan Chancellor [this message]
2019-09-11 20:55   ` [PATCH v3 2/3] powerpc: Avoid clang warnings around setjmp and longjmp Nick Desaulniers
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
2019-10-14 16:03   ` [PATCH v4 0/3] LLVM/Clang fixes for pseries_defconfig Nick Desaulniers

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