[PATCH v2 2/2] rust: doctest: trim function name for reproducbility

[Gary Guo <gary@kernel.org>]

From: Gary Guo <gary@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 <gary@garyguo.net>
---
Changes in v2:
- Do an unconditional replacement to cover all cases.
---
 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 5457679c12f9..79cef75f5af3 100644
--- a/scripts/rustdoc_test_builder.rs
+++ b/scripts/rustdoc_test_builder.rs
@@ -70,6 +70,11 @@ 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();
-- 
2.54.0