Re: [PATCH v2 01/33] rust: kbuild: remove `--remap-path-prefix` workarounds

[Nicolas Schier <nsc@kernel.org>]

On Mon, Apr 06, 2026 at 01:52:37AM +0200, Miguel Ojeda wrote:
> Commit 8cf5b3f83614 ("Revert "kbuild, rust: use -fremap-path-prefix
> to make paths relative"") removed `--remap-path-prefix` from the build
> system, so the workarounds are not needed anymore.
> 
> Thus remove them.
> 
> Note that the flag has landed again in parallel in this cycle in
> commit dda135077ecc ("rust: build: remap path to avoid absolute path"),
> together with `--remap-path-scope=macro` [1]. However, they are gated on
> `rustc-option-yn, --remap-path-scope=macro`, which means they are both
> only passed starting with Rust 1.95.0 [2]:
> 
>   `--remap-path-scope` is only stable in Rust 1.95, so use `rustc-option`
>   to detect its presence. This feature has been available as
>   `-Zremap-path-scope` for all versions that we support; however due to
>   bugs in the Rust compiler, it does not work reliably until 1.94. I opted
>   to not enable it for 1.94 as it's just a single version that we missed.
> 
> In turn, that means the workarounds removed here should not be needed
> again (even with the flag added again above), since:
> 
>   - `rustdoc` now recognizes the `--remap-path-prefix` flag since Rust
>     1.81.0 [3] (even if it is still an unstable feature [4]).
> 
>   - The Internal Compiler Error [5] that the comment mentions was fixed in
>     Rust 1.87.0 [6]. We tested that was the case in a previous version
>     of this series by making the workaround conditional [7][8].
> 
> ...which are both older versions than Rust 1.95.0.
> 
> We will still need to skip `--remap-path-scope` for `rustdoc` though,
> since `rustdoc` does not support that one yet [4].
> 
> Link: https://github.com/rust-lang/rust/issues/111540 [1]
> Link: https://github.com/rust-lang/rust/pull/147611 [2]
> Link: https://github.com/rust-lang/rust/pull/107099 [3]
> Link: https://doc.rust-lang.org/nightly/rustdoc/unstable-features.html#--remap-path-prefix-remap-source-code-paths-in-output [4]
> Link: https://github.com/rust-lang/rust/issues/138520 [5]
> Link: https://github.com/rust-lang/rust/pull/138556 [6]
> Link: https://lore.kernel.org/rust-for-linux/20260401114540.30108-9-ojeda@kernel.org/ [7]
> Link: https://lore.kernel.org/rust-for-linux/20260401114540.30108-10-ojeda@kernel.org/ [8]
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
>  rust/Makefile | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 

Acked-by: Nicolas Schier <nsc@kernel.org>

-- 
Nicolas