Re: [PATCH] powerpc: Avoid clang warnings around setjmp and longjmp
From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2019-08-12 17:36:09
Also in:
lkml, stable
On Sun, Aug 11, 2019 at 7:42 PM Nathan Chancellor [off-list ref] 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.
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@vger.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 <redacted>Thanks for the patch, Nathan. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
quoted hunk ↗ jump to hunk
--- 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
-- Thanks, ~Nick Desaulniers