Re: [PATCH v2] rust: kbuild: skip `--remap-path-prefix` for `rustdoc`

[Tamir Duberstein]

On Sat, Mar 15, 2025 at 3:41 PM Miguel Ojeda <ojeda@xxxxxxxxxx> wrote:
>
> `rustdoc` only recognizes `--remap-path-prefix` starting with
> Rust 1.81.0, which is later than on minimum, so we cannot pass it
> unconditionally. Otherwise, we get:
>
>     error: Unrecognized option: 'remap-path-prefix'
>
> Note that `rustc` (the compiler) does recognize the flag since a long
> time ago (1.26.0).
>
> Moreover, `rustdoc` since Rust 1.82.0 ICEs in out-of-tree builds when
> using `--remap-path-prefix`. The issue has been reduced and reported
> upstream [1].
>
> Thus workaround both issues by simply skipping the flag when generating
> the docs -- it is not critical there anyway.
>
> The ICE does not reproduce under `--test`, but we still need to skip
> the flag as well for `RUSTDOC TK` since it is not recognized.
>
> Fixes: 6b5747d07138 ("kbuild, rust: use -fremap-path-prefix to make paths relative")
> Link: https://github.com/rust-lang/rust/issues/138520 [1]
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> ---
> v2:
>   - Skip the flag also in `RUSTDOC TK`. The ICE does not apply there,
>     but we still need to skip the flag.
>
>  rust/Makefile | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index ea3849eb78f6..089473a89d46 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -57,10 +57,14 @@ endif
>  core-cfgs = \
>      --cfg no_fp_fmt_parse
>
> +# `rustc` recognizes `--remap-path-prefix` since 1.26.0, but `rustdoc` only
> +# since Rust 1.81.0. Moreover, `rustdoc` ICEs on out-of-tree builds since Rust
> +# 1.82.0 (https://github.com/rust-lang/rust/issues/138520). Thus workaround both
> +# issues skipping the flag. The former also applies to `RUSTDOC TK`.
>  quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
>        cmd_rustdoc = \
>         OBJTREE=$(abspath $(objtree)) \
> -       $(RUSTDOC) $(filter-out $(skip_flags),$(if $(rustdoc_host),$(rust_common_flags),$(rust_flags))) \
> +       $(RUSTDOC) $(filter-out $(skip_flags) --remap-path-prefix=%,$(if $(rustdoc_host),$(rust_common_flags),$(rust_flags))) \
>                 $(rustc_target_flags) -L$(objtree)/$(obj) \
>                 -Zunstable-options --generate-link-to-definition \
>                 --output $(rustdoc_output) \
> @@ -171,7 +175,7 @@ quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $<
>         rm -rf $(objtree)/$(obj)/test/doctests/kernel; \
>         mkdir -p $(objtree)/$(obj)/test/doctests/kernel; \
>         OBJTREE=$(abspath $(objtree)) \
> -       $(RUSTDOC) --test $(rust_flags) \
> +       $(RUSTDOC) --test $(filter-out --remap-path-prefix=%,$(rust_flags)) \
>                 -L$(objtree)/$(obj) --extern ffi --extern kernel \
>                 --extern build_error --extern macros \
>                 --extern bindings --extern uapi \
>
> base-commit: bc5431693696b3f928b0b7acf8d7a120127db7a4
> --
> 2.49.0
>

Reviewed-by: Tamir Duberstein <tamird@xxxxxxxxx>