With CONFIG_INIT_STACK_ALL_ZERO enabled, bindgen is passing
-ftrivial-auto-var-init=zero to clang, that triggers the following:
error: '-ftrivial-auto-var-init=zero' hasn't been enabled; enable it at your own peril for benchmarking purpose only with '-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'
This flag should be dropped in clang-17, but at the moment it seems more
reasonable to add it to the bindgen CFLAGS to prevent the error above.
In this way we can enable CONFIG_INIT_STACK_ALL_ZERO with CONFIG_RUST
without triggering any build error.
Link: https://reviews.llvm.org/D125142
Signed-off-by: Andrea Righi <[email protected]>
---
rust/Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/rust/Makefile b/rust/Makefile
index ff70c4c916f8..5e26db07a1dc 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -267,7 +267,8 @@ BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH))
# All warnings are inhibited since GCC builds are very experimental,
# many GCC warnings are not supported by Clang, they may only appear in
# some configurations, with new GCC versions, etc.
-bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
+bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET) \
+ -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
$(bindgen_extra_c_flags)
--
2.37.2
On Fri, Feb 10, 2023 at 06:22:03PM +0100, Andrea Righi wrote:
> With CONFIG_INIT_STACK_ALL_ZERO enabled, bindgen is passing
> -ftrivial-auto-var-init=zero to clang, that triggers the following:
>
> error: '-ftrivial-auto-var-init=zero' hasn't been enabled; enable it at your own peril for benchmarking purpose only with '-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'
>
> This flag should be dropped in clang-17, but at the moment it seems more
> reasonable to add it to the bindgen CFLAGS to prevent the error above.
>
> In this way we can enable CONFIG_INIT_STACK_ALL_ZERO with CONFIG_RUST
> without triggering any build error.
>
> Link: https://reviews.llvm.org/D125142
> Signed-off-by: Andrea Righi <[email protected]>
If this went via the kbuild tree, would we be able to use
$(CC_AUTO_VAR_INIT_ZERO_ENABLER)?
https://git.kernel.org/masahiroy/linux-kbuild/c/4e3feaad6ff8a7a57e3bf3308a93c93e3a2e17a6
Although, I suppose this could be a problem if the version of clang
being used to build the kernel does not support this flag while the
version of libclang in bindgen requires it?
> ---
> rust/Makefile | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index ff70c4c916f8..5e26db07a1dc 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -267,7 +267,8 @@ BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH))
> # All warnings are inhibited since GCC builds are very experimental,
> # many GCC warnings are not supported by Clang, they may only appear in
> # some configurations, with new GCC versions, etc.
> -bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
> +bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET) \
> + -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
>
> bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
> $(bindgen_extra_c_flags)
> --
> 2.37.2
>
On Fri, Feb 10, 2023 at 10:39:27AM -0700, Nathan Chancellor wrote:
> On Fri, Feb 10, 2023 at 06:22:03PM +0100, Andrea Righi wrote:
> > With CONFIG_INIT_STACK_ALL_ZERO enabled, bindgen is passing
> > -ftrivial-auto-var-init=zero to clang, that triggers the following:
> >
> > error: '-ftrivial-auto-var-init=zero' hasn't been enabled; enable it at your own peril for benchmarking purpose only with '-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'
> >
> > This flag should be dropped in clang-17, but at the moment it seems more
> > reasonable to add it to the bindgen CFLAGS to prevent the error above.
> >
> > In this way we can enable CONFIG_INIT_STACK_ALL_ZERO with CONFIG_RUST
> > without triggering any build error.
> >
> > Link: https://reviews.llvm.org/D125142
> > Signed-off-by: Andrea Righi <[email protected]>
>
> If this went via the kbuild tree, would we be able to use
> $(CC_AUTO_VAR_INIT_ZERO_ENABLER)?
>
> https://git.kernel.org/masahiroy/linux-kbuild/c/4e3feaad6ff8a7a57e3bf3308a93c93e3a2e17a6
>
> Although, I suppose this could be a problem if the version of clang
> being used to build the kernel does not support this flag while the
> version of libclang in bindgen requires it?
I didn't have much success with CC_AUTO_VAR_INIT_ZERO_ENABLER, but maybe
a better way is to check if the version of libclang used by bindgen is
less than 17, considering that is extra clang option is supposed to be
dropped in clang-17:
https://github.com/llvm/llvm-project/issues/44842
I'll send a v2, unless we find a better way to support this auto var
zero-init feature.
-Andrea