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Message-Id: <20190812023214.107817-1-natechancellor@gmail.com>
Date: Sun, 11 Aug 2019 19:32:15 -0700
From: Nathan Chancellor <natechancellor@...il.com>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Nick Desaulniers <ndesaulniers@...gle.com>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
clang-built-linux@...glegroups.com,
Nathan Chancellor <natechancellor@...il.com>,
stable@...r.kernel.org
Subject: [PATCH] powerpc: Avoid clang warnings around setjmp and longjmp
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.
Take the same approach as the above commit by disabling the warning for
the same reason, we provide our own longjmp/setjmp function.
Cc: stable@...r.kernel.org # 4.19+
Link: https://github.com/ClangBuiltLinux/linux/issues/625
Link: https://github.com/llvm/llvm-project/commit/3be25e79477db2d31ac46493d97eca8c20592b07
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
It may be worth using -fno-builtin-setjmp and -fno-builtin-longjmp
instead as it makes it clear to clang that we are not using the builtin
longjmp and setjmp functions, which I think is why these warnings are
appearing (at least according to the commit that introduced this waring).
Sample patch:
https://github.com/ClangBuiltLinux/linux/issues/625#issuecomment-519251372
However, this is the most conservative approach, as I have already had
someone notice this error when building LLVM with PGO on tip of tree
LLVM.
arch/powerpc/kernel/Makefile | 5 +++--
arch/powerpc/xmon/Makefile | 5 +++--
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index ea0c69236789..44e340ed4722 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -5,8 +5,9 @@
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 about longjmp and setjmp built-ins (inclusion of setjmp.h and declaration of jmp_buf type)
+CFLAGS_crash.o += $(call cc-disable-warning, builtin-requires-header) \
+ $(call cc-disable-warning, incomplete-setjmp-declaration)
ifdef CONFIG_PPC64
CFLAGS_prom_init.o += $(NO_MINIMAL_TOC)
diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index f142570ad860..53f341391210 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -1,8 +1,9 @@
# 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 about longjmp and setjmp built-ins (inclusion of setjmp.h and declaration of jmp_buf type)
+subdir-ccflags-y := $(call cc-disable-warning, builtin-requires-header) \
+ $(call cc-disable-warning, incomplete-setjmp-declaration)
GCOV_PROFILE := n
KCOV_INSTRUMENT := n
--
2.23.0.rc2
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