On Sun, Aug 11, 2019 at 7:42 PM 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.
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/3be25e79477db2d31ac46493d97eca8c... Signed-off-by: Nathan Chancellor natechancellor@gmail.com
Thanks for the patch, Nathan. Reviewed-by: Nick Desaulniers ndesaulniers@google.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