Re: [PATCH v2 19/20] rust: syn: enable support in kbuild

Tamir Duberstein
2026-01-04T23:17:39Z

On Mon, Nov 24, 2025 at 10:25 AM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> With all the new files in place and ready from the new crate, enable
> the support for it in the build system.
>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Reviewed-by: Gary Guo <gary@garyguo.net>
> Tested-by: Gary Guo <gary@garyguo.net>
> Tested-by: Jesung Yang <y.j3ms.n@gmail.com>
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
> Makefile | 1 +
> rust/Makefile | 37 ++++++++++++++++++++++++++++---
> scripts/generate_rust_analyzer.py | 7 ++++++
> 3 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 85da055e4f00..96ddbaae7e12 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1835,6 +1835,7 @@ rustfmt:
> \( \
> -path $(srctree)/rust/proc-macro2 \
> -o -path $(srctree)/rust/quote \
> + -o -path $(srctree)/rust/syn \
> \) -prune -o \
> -type f -a -name '*.rs' -a ! -name '*generated*' -print \
> | xargs $(RUSTFMT) $(rustfmt_flags)
> diff --git a/rust/Makefile b/rust/Makefile
> index 4f4a00594142..8988ecf32531 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -27,7 +27,7 @@ endif
>
> obj-$(CONFIG_RUST) += exports.o
>
> -always-$(CONFIG_RUST) += libproc_macro2.rlib libquote.rlib
> +always-$(CONFIG_RUST) += libproc_macro2.rlib libquote.rlib libsyn.rlib
>
> always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.rs
> always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.c
> @@ -101,6 +101,22 @@ quote-flags := \
> --extern proc_macro2 \
> $(call cfgs-to-flags,$(quote-cfgs))
>
> +# `extra-traits`, `fold` and `visit` may be enabled if needed.
> +syn-cfgs := \
> + feature="clone-impls" \
> + feature="derive" \
> + feature="full" \
> + feature="parsing" \
> + feature="printing" \
> + feature="proc-macro" \
> + feature="visit-mut"
> +
> +syn-flags := \
> + --cap-lints=allow \
> + --extern proc_macro2 \
> + --extern quote \
> + $(call cfgs-to-flags,$(syn-cfgs))
> +
> # `rustdoc` did not save the target modifiers, thus workaround for
> # the time being (https://github.com/rust-lang/rust/issues/144521).
> rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18)
> @@ -161,11 +177,16 @@ rustdoc-quote: private skip_flags = $(quote-skip_flags)
> rustdoc-quote: $(src)/quote/lib.rs rustdoc-clean rustdoc-proc_macro2 FORCE
> +$(call if_changed,rustdoc)
>
> +rustdoc-syn: private rustdoc_host = yes
> +rustdoc-syn: private rustc_target_flags = $(syn-flags)
> +rustdoc-syn: $(src)/syn/lib.rs rustdoc-clean rustdoc-quote FORCE
> + +$(call if_changed,rustdoc)
> +
> rustdoc-macros: private rustdoc_host = yes
> rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \
> --extern proc_macro
> rustdoc-macros: $(src)/macros/lib.rs rustdoc-clean rustdoc-proc_macro2 \
> - rustdoc-quote FORCE
> + rustdoc-quote rustdoc-syn FORCE
> +$(call if_changed,rustdoc)
>
> # Starting with Rust 1.82.0, skipping `-Wrustdoc::unescaped_backticks` should
> @@ -231,6 +252,10 @@ rusttestlib-quote: private rustc_target_flags = $(quote-flags)
> rusttestlib-quote: $(src)/quote/lib.rs rusttestlib-proc_macro2 FORCE
> +$(call if_changed,rustc_test_library)
>
> +rusttestlib-syn: private rustc_target_flags = $(syn-flags)
> +rusttestlib-syn: $(src)/syn/lib.rs rusttestlib-quote FORCE
> + +$(call if_changed,rustc_test_library)
> +
> rusttestlib-macros: private rustc_target_flags = --extern proc_macro
> rusttestlib-macros: private rustc_test_library_proc = yes
> rusttestlib-macros: $(src)/macros/lib.rs FORCE
> @@ -488,6 +513,11 @@ $(obj)/libquote.rlib: private rustc_target_flags = $(quote-flags)
> $(obj)/libquote.rlib: $(src)/quote/lib.rs $(obj)/libproc_macro2.rlib FORCE
> +$(call if_changed_dep,rustc_procmacrolibrary)
>
> +$(obj)/libsyn.rlib: private skip_clippy = 1
> +$(obj)/libsyn.rlib: private rustc_target_flags = $(syn-flags)
> +$(obj)/libsyn.rlib: $(src)/syn/lib.rs $(obj)/libquote.rlib FORCE
> + +$(call if_changed_dep,rustc_procmacrolibrary)
> +
> quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
> cmd_rustc_procmacro = \
> $(RUSTC_OR_CLIPPY) $(rust_common_flags) $(rustc_target_flags) \
> @@ -500,7 +530,7 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
>
> # Procedural macros can only be used with the `rustc` that compiled it.
> $(obj)/$(libmacros_name): $(src)/macros/lib.rs $(obj)/libproc_macro2.rlib \
> - $(obj)/libquote.rlib FORCE
> + $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE
> +$(call if_changed_dep,rustc_procmacro)
>
> $(obj)/$(libpin_init_internal_name): private rustc_target_flags = --cfg kernel
> @@ -525,6 +555,7 @@ rust-analyzer:
> --cfgs='core=$(core-cfgs)' $(core-edition) \
> --cfgs='proc_macro2=$(proc_macro2-cfgs)' \
> --cfgs='quote=$(quote-cfgs)' \
> + --cfgs='syn=$(syn-cfgs)' \
> $(realpath $(srctree)) $(realpath $(objtree)) \
> $(rustc_sysroot) $(RUST_LIB_SRC) $(if $(KBUILD_EXTMOD),$(srcroot)) \
> > rust-project.json
> diff --git a/scripts/generate_rust_analyzer.py b/scripts/generate_rust_analyzer.py
> index 4faf153ed2ee..5b6f7b8d6918 100755
> --- a/scripts/generate_rust_analyzer.py
> +++ b/scripts/generate_rust_analyzer.py
> @@ -100,6 +100,13 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs, core_edit
> cfg=crates_cfgs["quote"],
> )
>
> + append_crate(
> + "syn",
> + srctree / "rust" / "syn" / "lib.rs",
> + ["proc_macro", "proc_macro2", "quote"],
> + cfg=crates_cfgs["syn"],
> + )

I think we need to add "std" here -- without it, navigating to methods
on e.g. Vec items defined in syn doesn't work (it does work with "std"
added).

> +
> append_crate(
> "macros",
> srctree / "rust" / "macros" / "lib.rs",
> --
> 2.52.0
>
>