On Sun, Aug 11, 2019 at 07:32:15PM -0700, Nathan Chancellor 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: sta...@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 <natechancel...@gmail.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
>
Did any of the maintainers have any comment on this patch?
Cheers,
Nathan
