From 3fd7bc8b1c5f7eaab9374674e7fc0a5798673b5b Mon Sep 17 00:00:00 2001
From: Matt Jolly <kangie@gentoo.org>
Date: Sat, 22 Aug 2026 15:54:04 +1000
Subject: [PATCH 1/2] build/rust: Use rust_sysroot for bindings and wrappers
 globally

Hardcoded `//third_party/rust-toolchain` paths were still lingering
in various places, causing build failures (e.g., ninja errors for missing
`rustc` and `rs_bindings_from_cc` rules) when utilizing a custom Rust
sysroot.

This patch updates `rustc_wrapper_inputs`, `cc_bindings_from_rs`,
`rs_bindings_from_cc`, `rustfmt`, and `clippy-driver` to use the
configured `rust_sysroot` GN argument instead of hardcoding the default
tree path. For Python scripts like `run_rs_bindings_from_cc.py`, paths
are now parsed via command line arguments rather than relying on
relative directory resolution.

Bug: 491242305
Signed-off-by: Matt Jolly <kangie@gentoo.org>


[bentoo: rebased onto 157. M157 deleted build/rust/rs_bindings_from_cc.gni
 and gni_impl/run_rs_bindings_from_cc.py: Crubit's tool paths now live in
 one place, gni_impl/crubit_shared_args.gni (`_toolchain_bin_path`), and
 the wrapper scripts receive them as arguments.  The two dropped hunks
 collapse into pointing `_toolchain_bin_path` at `$rust_sysroot/bin`;
 the file imports //build/config/rust.gni itself because a .gni import
 runs in a scope of its own.]
diff -ruN a/build/config/rust.gni b/build/config/rust.gni
--- a/build/config/rust.gni
+++ b/build/config/rust.gni
@@ -453,7 +453,7 @@
 ]
 
 if (host_os == "win") {
-  rustc_wrapper_inputs += [ "//third_party/rust-toolchain/bin/rustc.exe" ]
+  rustc_wrapper_inputs += [ "$rust_sysroot/bin/rustc.exe" ]
 } else {
-  rustc_wrapper_inputs += [ "//third_party/rust-toolchain/bin/rustc" ]
+  rustc_wrapper_inputs += [ "$rust_sysroot/bin/rustc" ]
 }
diff -ruN a/build/rust/gni_impl/crubit_shared_args.gni b/build/rust/gni_impl/crubit_shared_args.gni
--- a/build/rust/gni_impl/crubit_shared_args.gni
+++ b/build/rust/gni_impl/crubit_shared_args.gni
@@ -5,10 +5,12 @@
 # This `.gni` file defines constants that are shared / reused across
 # `cpp_api_from_rust.gni` and `rust_api_from_cpp.gni`.
 
+import("//build/config/rust.gni")
+
 crubit_support_path_format = "\"third_party/crubit/support/{header}\""
 rustfmt_config_path = "//.rustfmt.toml"
 
-_toolchain_bin_path = "//third_party/rust-toolchain/bin"
+_toolchain_bin_path = "$rust_sysroot/bin"
 cpp_api_from_rust_exe_path = "${_toolchain_bin_path}/cc_bindings_from_rs"
 rust_api_from_cpp_exe_path = "${_toolchain_bin_path}/rs_bindings_from_cc"
 rustfmt_exe_path = "${_toolchain_bin_path}/rustfmt"
diff -ruN a/build/rust/gni_impl/rust_target.gni b/build/rust/gni_impl/rust_target.gni
--- a/build/rust/gni_impl/rust_target.gni
+++ b/build/rust/gni_impl/rust_target.gni
@@ -733,9 +733,9 @@
           # `import`ed for `LoadRustEnvAndFlags`, etc.
           inputs = rustc_wrapper_inputs
           if (host_os == "win") {
-            inputs += [ "//third_party/rust-toolchain/bin/clippy-driver.exe" ]
+            inputs += [ "$rust_sysroot/bin/clippy-driver.exe" ]
           } else {
-            inputs += [ "//third_party/rust-toolchain/bin/clippy-driver" ]
+            inputs += [ "$rust_sysroot/bin/clippy-driver" ]
           }
           if (rust_clippy_conf_file != "") {
             inputs += [ rust_clippy_conf_file ]
@@ -743,7 +743,7 @@
 
           args = [
             "--clippy-driver",
-            rebase_path("//third_party/rust-toolchain/bin/clippy-driver",
+            rebase_path("$rust_sysroot/bin/clippy-driver",
                         root_build_dir),
             "--rustc-env-and-flags",
             rebase_path(_rustc_env_and_flags, root_build_dir),