Fix a few different compiler errors that cause rustc-option to give wrong results. If KBUILD_RUSTFLAGS or the flags being tested contain any -Z flags, then the error below is generated. The RUSTC_BOOTSTRAP environment variable is added to fix this error. error: the option `Z` is only accepted on the nightly compiler help: consider switching to a nightly toolchain: `rustup default nightly` note: selecting a toolchain with `+toolchain` arguments require a rustup proxy; see <https://rust-lang.github.io/rustup/concepts/index.html> note: for more information about Rust's stability policy, see <https://doc.rust-lang.org/book/appendix-07-nightly-rust.html#unstable-features> error: 1 nightly option were parsed Note that RUSTC_BOOTSTRAP is also defined in the top-level Makefile, but its value is unfortunately *not* inherited from the environment. That said, this is changing as of commit 98da874c4303 ("[SV 10593] Export variables to $(shell ...) commands"), which is part of Make 4.4. The probe may also fail with the error message below. To fix it, the /dev/null argument is replaced with a file containing the crate attribute #![no_core]. The #![no_core] attribute ensures that rustc does not look for the standard library. It's not possible to instead supply a standard library to rustc, as we need `rustc-option` before the Rust standard library is compiled. error[E0463]: can't find crate for `std` | = note: the `aarch64-unknown-none` target may not be installed = help: consider downloading the target with `rustup target add aarch64-unknown-none` = help: consider building the standard library from source with `cargo build -Zbuild-std` The -o and --out-dir parameters are altered to fix this warning: warning: ignoring --out-dir flag due to -o flag The --sysroot flag is provided as we would otherwise require it to be present in KBUILD_RUSTFLAGS. The --emit=obj flag is used to write the resulting rlib to /dev/null instead of writing it to a file in $(TMPOUT). I verified that the Kconfig version of rustc-option doesn't have the same issues. Fixes: c42297438aee ("kbuild: rust: Define probing macros for rustc") Co-developed-by: Miguel Ojeda <ojeda@xxxxxxxxxx> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> --- Based on top of: https://lore.kernel.org/r/20241009102821.2675718-1-masahiroy@xxxxxxxxxx --- Changes in v3: - Use stdin instead of a rust/probe.rs file. - Fix --out-dir argument. - Move RUSTC_BOOTSTRAP to __rustc-option. - Add --sysroot and --emit=obj flags. - Rebase on top of [PATCH] kbuild: refactor cc-option-yn, cc-disable-warning, rust-option-yn macros - Link to v2: https://lore.kernel.org/r/20241008-rustc-option-bootstrap-v2-1-e6e155b8f9f3@xxxxxxxxxx Changes in v2: - Add `export` to RUSTC_BOOTSTRAP. - Fix error about core being missing. - Fix warning about -o flag. - Link to v1: https://lore.kernel.org/r/20241008-rustc-option-bootstrap-v1-1-9eb06261d4f7@xxxxxxxxxx --- scripts/Makefile.compiler | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler index 73d611d383b2..e0842496d26e 100644 --- a/scripts/Makefile.compiler +++ b/scripts/Makefile.compiler @@ -73,8 +73,11 @@ ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3)) # __rustc-option # Usage: MY_RUSTFLAGS += $(call __rustc-option,$(RUSTC),$(MY_RUSTFLAGS),-Cinstrument-coverage,-Zinstrument-coverage) +# TODO: remove RUSTC_BOOTSTRAP=1 when we raise the minimum GNU Make version to 4.4 __rustc-option = $(call try-run,\ - $(1) $(2) $(3) --crate-type=rlib /dev/null --out-dir=$$TMPOUT -o "$$TMP",$(3),$(4)) + echo '#![allow(missing_docs)]#![feature(no_core)]#![no_core]' | RUSTC_BOOTSTRAP=1\ + $(1) --sysroot=/dev/null $(filter-out --sysroot=/dev/null,$(2)) $(3)\ + --crate-type=rlib --out-dir=$(TMPOUT) --emit=obj=- - >/dev/null,$(3),$(4)) # rustc-option # Usage: rustflags-y += $(call rustc-option,-Cinstrument-coverage,-Zinstrument-coverage) --- base-commit: 1ba227507e8459788bf0e192700347c941e3e218 change-id: 20241008-rustc-option-bootstrap-607e5bf3114c Best regards, -- Alice Ryhl <aliceryhl@xxxxxxxxxx>
