With the minimum version bump in place, `rustdoc` now always recognizes
the `--remap-path-prefix` flag.

In addition, the Internal Compiler Error that the comment mentions [1]
was fixed in Rust 1.87.0 [2], so we still need to skip the flag for
the normal `rustdoc` case, but not for `--test` since the ICE does not
reproduce there -- please see commit 2c8725c1dca3 ("rust: kbuild: skip
`--remap-path-prefix` for `rustdoc`").

Thus update the comment and remove the skipping of the flag for the
`--test` case.

Note that commit dda135077ecc ("rust: build: remap path to avoid
absolute path") re-landed the `--remap-path-prefix` flag (together with
`--remap-path-scope`), so we keep the workaround, i.e. an alternative
could have been to simply delete the skip entirely, but since we still
have it and it will be needed when this gets merged, let's keep it.

Link: https://github.com/rust-lang/rust/issues/138520 [1]
Link: https://github.com/rust-lang/rust/pull/138556 [2]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/Makefile | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 193cf06eea64..708530ee3613 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -142,10 +142,9 @@ rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-a
 # Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
 doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)
 
-# `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`.
+# `rustdoc` ICEs on out-of-tree builds in Rust < 1.87.0
+# (https://github.com/rust-lang/rust/issues/138520). Thus workaround the
+# issue skipping the flag.
 quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
       cmd_rustdoc = \
 	OBJTREE=$(abspath $(objtree)) \
@@ -333,7 +332,7 @@ 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 $(filter-out --remap-path-prefix=%,$(rust_flags)) \
+	$(RUSTDOC) --test $(rust_flags) \
 		-L$(objtree)/$(obj) --extern ffi --extern pin_init \
 		--extern kernel --extern build_error --extern macros \
 		--extern bindings --extern uapi \
-- 
2.53.0

On Wed Apr 1, 2026 at 12:45 PM BST, Miguel Ojeda wrote:
> With the minimum version bump in place, `rustdoc` now always recognizes
> the `--remap-path-prefix` flag.
>
> In addition, the Internal Compiler Error that the comment mentions [1]
> was fixed in Rust 1.87.0 [2], so we still need to skip the flag for
> the normal `rustdoc` case, but not for `--test` since the ICE does not
> reproduce there -- please see commit 2c8725c1dca3 ("rust: kbuild: skip
> `--remap-path-prefix` for `rustdoc`").
>
> Thus update the comment and remove the skipping of the flag for the
> `--test` case.
>
> Note that commit dda135077ecc ("rust: build: remap path to avoid
> absolute path") re-landed the `--remap-path-prefix` flag (together with
> `--remap-path-scope`), so we keep the workaround, i.e. an alternative
> could have been to simply delete the skip entirely, but since we still
> have it and it will be needed when this gets merged, let's keep it.

I'm not sure that I parse this. You do remove the filter-out completely below?

>
> Link: https://github.com/rust-lang/rust/issues/138520 [1]
> Link: https://github.com/rust-lang/rust/pull/138556 [2]
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
>  rust/Makefile | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index 193cf06eea64..708530ee3613 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -142,10 +142,9 @@ rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-a
>  # Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
>  doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)
>  
> -# `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`.
> +# `rustdoc` ICEs on out-of-tree builds in Rust < 1.87.0
> +# (https://github.com/rust-lang/rust/issues/138520). Thus workaround the
> +# issue skipping the flag.
>  quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
>        cmd_rustdoc = \
>  	OBJTREE=$(abspath $(objtree)) \
> @@ -333,7 +332,7 @@ 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 $(filter-out --remap-path-prefix=%,$(rust_flags)) \

Looks like this is going to conflict with rust-fixes (which adds the
--remap-path-scope). Perhaps worth doing a back merge?

Best,
Gary


> +	$(RUSTDOC) --test $(rust_flags) \
>  		-L$(objtree)/$(obj) --extern ffi --extern pin_init \
>  		--extern kernel --extern build_error --extern macros \
>  		--extern bindings --extern uapi \

On Wed, Apr 1, 2026 at 3:59 PM Gary Guo <gary@garyguo.net> wrote:
>
> I'm not sure that I parse this. You do remove the filter-out completely below?

(I see you saw the other commit)

> Looks like this is going to conflict with rust-fixes (which adds the
> --remap-path-scope). Perhaps worth doing a back merge?

It would be only a couple lines conflicting, so it should be fine.

Having said that, when I was doing this, I wondered if we should even
consider keeping the workaround. In other words, locally for
`rust-next`, the "normal" commit would be to remove the workaround
entirely because there the flag doesn't exist to begin with (i.e. the
workaround should have been removed back when the revert landed).

Then, when conflict happens in linux-next, we can just keep the
addition of the flag from your commit -- the rest can say as-is, i.e.
no workaround needed, because you only enable both flags in a version
(1.95.0) where there is no need for the workaround (which was for <
1.87.0).

It is also why I added the second commit here, i.e. the "make it
conditional", because I was testing that indeed we didn't need the
workaround anymore.

So it may just simpler to do that. What I thought was that perhaps the
workaround is good even if we ourselves don't pass the flag, e.g.
someone else may be passing it. But the chances are very low,
restricted to a couple versions, and the error is obvious and at build
time anyway.

Cheers,
Miguel