[PATCH RESEND] rust: doctest: trim function name for reproducbility

[Gary Guo]

From: Gary Guo <ga...@garyguo.net>

Currently rustdoc will generate function names like
"_doctest_main__home_gary_Projects_linux_rust_kernel_io_rs_824_0" for a
doctest located at rust/kernel/io.rs:824, when building with separate
outdir using `O=`. This creates overlong symbol names and is also not
reproducible.

Fix it by doing a custom remapping to trim it to something like
`_doctest_main_rust_kernel_io_rs_824_0`.

Signed-off-by: Gary Guo <ga...@garyguo.net>
---
scripts/rustdoc_test_builder.rs | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/scripts/rustdoc_test_builder.rs b/scripts/rustdoc_test_builder.rs
index df864437cef7..561f912c2000 100644
--- a/scripts/rustdoc_test_builder.rs
+++ b/scripts/rustdoc_test_builder.rs
@@ -72,6 +72,11 @@ fn main() {
// Figure out a smaller test name based on the generated function name.
let name = rustdoc_function_name.split_once("_rust_kernel_").unwrap().1;

+ // The rustdoc function name can include the absolute path when building with `O=` which is
+ // undesireable and create overlong symbol names. Remap it to use relative path.
+ let trimmed_function_name = format!("_doctest_main_rust_kernel_{name}");
+ let body = body.replace(&rustdoc_function_name, &trimmed_function_name);
+
let path = format!("rust/test/doctests/kernel/{name}");

std::fs::write(path, body.as_bytes()).unwrap();

base-commit: 93f51579e7df248780214094418f205253383cc5
--
2.54.0

[Miguel Ojeda]

On Thu, Sep 24, 2026 at 2:51 AM Gary Guo <ga...@kernel.org> wrote:
>
> Currently rustdoc will generate function names like

Just to clarify, this happens only for Rust < 1.95 since we use
`--remap` which already it in newer versions -- I will add a note to
the comment, since we can remove this on the next version bump.

But please shout if I am missing something.

Cheers,
Miguel

[Miguel Ojeda]

On Thu, Sep 24, 2026 at 2:51 AM Gary Guo <ga...@kernel.org> wrote:
>

> From: Gary Guo <ga...@garyguo.net>
>
> Currently rustdoc will generate function names like
> "_doctest_main__home_gary_Projects_linux_rust_kernel_io_rs_824_0" for a
> doctest located at rust/kernel/io.rs:824, when building with separate
> outdir using `O=`. This creates overlong symbol names and is also not
> reproducible.
>
> Fix it by doing a custom remapping to trim it to something like
> `_doctest_main_rust_kernel_io_rs_824_0`.
>
> Signed-off-by: Gary Guo <ga...@garyguo.net>

Applied to `rust-next` -- thanks!

[ `rustdoc` already remaps these paths when we use Rust >= 1.95, thus
this fix is needed for older toolchains. - Miguel ]

[ Added `TODO` comment about the minimum version bump. Reworded title
and comment for typos. - Miguel ]

Cheers,
Miguel