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 ---
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) \ + $(call cc-disable-warning, incomplete-setjmp-declaration)
GCOV_PROFILE := n KCOV_INSTRUMENT := n
Le 12/08/2019 à 04:32, Nathan Chancellor a écrit :
Commit aea447141c7e ("powerpc: Disable -Wbuiltin-requires-header when setjmp is used") disabled -Wbuiltin-requires-header because of a warning about the setjmp and longjmp declarations.
r367387 in clang added another diagnostic around this, complaining that there is no jmp_buf declaration.
[...]
Cc: stable@vger.kernel.org # 4.19+ Link: https://github.com/ClangBuiltLinux/linux/issues/625 Link: https://github.com/llvm/llvm-project/commit/3be25e79477db2d31ac46493d97eca8c... Signed-off-by: Nathan Chancellor natechancellor@gmail.com
[...]
arch/powerpc/kernel/Makefile | 5 +++-- arch/powerpc/xmon/Makefile | 5 +++--
What about scripts/recordmcount.c and scripts/sortextable.c which contains calls to setjmp() and longjmp() ?
And arch/um/ ?
Christophe
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index ea0c69236789..44e340ed4722 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -5,8 +5,9 @@ CFLAGS_ptrace.o += -DUTS_MACHINE='"$(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
On Mon, Aug 12, 2019 at 07:37:51AM +0200, Christophe Leroy wrote:
Le 12/08/2019 à 04:32, Nathan Chancellor a écrit :
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.
[...]
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
[...]
arch/powerpc/kernel/Makefile | 5 +++-- arch/powerpc/xmon/Makefile | 5 +++--
What about scripts/recordmcount.c and scripts/sortextable.c which contains calls to setjmp() and longjmp() ?
And arch/um/ ?
Christophe
Hi Christophe,
It looks like all of those will be using the system's setjmp header, which won't cause these warnings.
Cheers, Nathan
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
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: 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
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
Nathan Chancellor natechancellor@gmail.com writes:
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
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
Couldn't we just add those flags to CFLAGS for the whole kernel? Rather than making them per-file.
I mean there's no kernel code that wants to use clang's builtin setjmp/longjmp implementation at all right?
cheers
On Wed, Aug 28, 2019 at 11:43:53PM +1000, Michael Ellerman wrote:
Nathan Chancellor natechancellor@gmail.com writes:
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
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
Couldn't we just add those flags to CFLAGS for the whole kernel? Rather than making them per-file.
Yes, I don't think this would be unreasonable. Are you referring to the cc-disable-warning flags or the -fno-builtin flags? I personally think the -fno-builtin flags convey to clang what the kernel is intending to do better than disabling the warnings outright.
I mean there's no kernel code that wants to use clang's builtin setjmp/longjmp implementation at all right?
cheers
I did a quick search of the tree and it looks like powerpc and x86/um are the only architectures that do anything with setjmp/longjmp. x86/um avoids this by using a define flag to change setjmp to kernel_setjmp:
arch/um/Makefile: -Dlongjmp=kernel_longjmp -Dsetjmp=kernel_setjmp \
Seems like adding those flags should be safe.
Cheers, Nathan
On Wed, Aug 28, 2019 at 10:53 AM Nathan Chancellor natechancellor@gmail.com wrote:
On Wed, Aug 28, 2019 at 11:43:53PM +1000, Michael Ellerman wrote:
Nathan Chancellor natechancellor@gmail.com writes:
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
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
Couldn't we just add those flags to CFLAGS for the whole kernel? Rather than making them per-file.
Yes, I don't think this would be unreasonable. Are you referring to the cc-disable-warning flags or the -fno-builtin flags? I personally think the -fno-builtin flags convey to clang what the kernel is intending to do better than disabling the warnings outright.
The `-f` family of flags have dire implications for codegen, I'd really prefer we think long and hard before adding/removing them to suppress warnings. I don't think it's a solution for this particular problem.
I mean there's no kernel code that wants to use clang's builtin setjmp/longjmp implementation at all right?
cheers
I did a quick search of the tree and it looks like powerpc and x86/um are the only architectures that do anything with setjmp/longjmp. x86/um avoids this by using a define flag to change setjmp to kernel_setjmp:
arch/um/Makefile: -Dlongjmp=kernel_longjmp -Dsetjmp=kernel_setjmp \
Seems like adding those flags should be safe.
Cheers, Nathan
On Wed, Aug 28, 2019 at 11:01:14AM -0700, Nick Desaulniers wrote:
On Wed, Aug 28, 2019 at 10:53 AM Nathan Chancellor natechancellor@gmail.com wrote:
On Wed, Aug 28, 2019 at 11:43:53PM +1000, Michael Ellerman wrote:
Nathan Chancellor natechancellor@gmail.com writes:
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
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
Couldn't we just add those flags to CFLAGS for the whole kernel? Rather than making them per-file.
Yes, I don't think this would be unreasonable. Are you referring to the cc-disable-warning flags or the -fno-builtin flags? I personally think the -fno-builtin flags convey to clang what the kernel is intending to do better than disabling the warnings outright.
The `-f` family of flags have dire implications for codegen, I'd really prefer we think long and hard before adding/removing them to suppress warnings. I don't think it's a solution for this particular problem.
I am fine with whatever approach gets this warning fixed to the maintainer's satisfaction...
However, I think that -fno-builtin-* would be appropriate here because we are providing our own setjmp implementation, meaning clang should not be trying to do anything with the builtin implementation like building a declaration for it.
Cheers, Nathan
On Wed, Aug 28, 2019 at 11:45 AM Nathan Chancellor natechancellor@gmail.com wrote:
On Wed, Aug 28, 2019 at 11:01:14AM -0700, Nick Desaulniers wrote:
On Wed, Aug 28, 2019 at 10:53 AM Nathan Chancellor natechancellor@gmail.com wrote:
Yes, I don't think this would be unreasonable. Are you referring to the cc-disable-warning flags or the -fno-builtin flags? I personally think the -fno-builtin flags convey to clang what the kernel is intending to do better than disabling the warnings outright.
The `-f` family of flags have dire implications for codegen, I'd really prefer we think long and hard before adding/removing them to suppress warnings. I don't think it's a solution for this particular problem.
I am fine with whatever approach gets this warning fixed to the maintainer's satisfaction...
However, I think that -fno-builtin-* would be appropriate here because we are providing our own setjmp implementation, meaning clang should not be trying to do anything with the builtin implementation like building a declaration for it.
That's a good reason IMO. IIRC, the -fno-builtin-* flags don't warn if * is some unrecognized value, so -fno-builtin-setjmp may not actually do anything, and you may need to scan the source (of clang or llvm).
On Wed, Aug 28, 2019 at 03:16:19PM -0700, Nick Desaulniers wrote:
That's a good reason IMO. IIRC, the -fno-builtin-* flags don't warn if * is some unrecognized value, so -fno-builtin-setjmp may not actually do anything, and you may need to scan the source (of clang or llvm).
-fno-builtin-foo makes the compiler not handle "foo" the same as it handles "__builtin_foo". If the compiler has no idea about "foo", well, that is exactly what it does then anyhow, so why would it warn :-)
Segher
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