linux-kernel - [PATCH] rust: kbuild: skip `--remap-path-prefix` for `rustdoc`

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Message-ID: <20250314213333.2230670-1-ojeda@kernel.org>
Date: Fri, 14 Mar 2025 22:33:33 +0100
From: Miguel Ojeda <ojeda@...nel.org>
To: Masahiro Yamada <masahiroy@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	linux-kbuild@...r.kernel.org,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev
Subject: [PATCH] rust: kbuild: skip `--remap-path-prefix` for `rustdoc`

`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.

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@...nel.org>
---
 rust/Makefile | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/rust/Makefile b/rust/Makefile
index ea3849eb78f6..6586a7aa007e 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.
 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) \

base-commit: bc5431693696b3f928b0b7acf8d7a120127db7a4
-- 
2.49.0