From a95a9c97813b3a3a68b73a030c2f0101e32cb762 Mon Sep 17 00:00:00 2001
From: Homalozoa X <21300069+homalozoa@users.noreply.github.com>
Date: Fri, 1 Sep 2023 20:53:57 +0800
Subject: [PATCH] feat: add arg `CROSS_ARCH` for cross-compilation (#147)

Signed-off-by: homalozoa <nx.tardis@gmail.com>
---
 CMakeLists.txt | 17 ++++++++++++-----
 README.md      |  9 +++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f7a14002..c52c2276 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,6 +27,13 @@ find_package(ament_cmake REQUIRED)
 # find_package(<dependency> REQUIRED)
 
 set(RUST_TARGET_DIR ${CMAKE_BINARY_DIR}/target)
+if(DEFINED CROSS_ARCH)
+  set(RUST_INSTALL_DIR ${RUST_TARGET_DIR}/${CROSS_ARCH})
+  set(BUILD_CMD cargo zigbuild --release --manifest-path "${CMAKE_SOURCE_DIR}/zenoh-bridge-dds/Cargo.toml" --target-dir "${RUST_TARGET_DIR}" --target ${CROSS_ARCH})
+else()
+  set(RUST_INSTALL_DIR ${RUST_TARGET_DIR})
+  set(BUILD_CMD cargo build --release --manifest-path "${CMAKE_SOURCE_DIR}/zenoh-bridge-dds/Cargo.toml" --target-dir "${RUST_TARGET_DIR}")
+endif()
 
 FILE(GLOB RUST_SRC_FILES
   ${CMAKE_SOURCE_DIR}/zenoh-bridge-dds/src/*.rs
@@ -35,8 +42,8 @@ FILE(GLOB RUST_SRC_FILES
 
 add_custom_command(
     OUTPUT
-        ${RUST_TARGET_DIR}/release/zenoh-bridge-dds
-    COMMAND cargo build --release --manifest-path "${CMAKE_SOURCE_DIR}/zenoh-bridge-dds/Cargo.toml" --target-dir "${RUST_TARGET_DIR}"
+        ${RUST_INSTALL_DIR}/release/zenoh-bridge-dds
+    COMMAND ${BUILD_CMD}
     DEPENDS
         ${RUST_SRC_FILES}
 )
@@ -44,7 +51,7 @@ add_custom_command(
 add_custom_target(
     build_crate ALL
     DEPENDS
-        ${RUST_TARGET_DIR}/release/zenoh-bridge-dds
+        ${RUST_INSTALL_DIR}/release/zenoh-bridge-dds
 )
 
 macro(INSTALL_ZENOH src_path dst_path)
@@ -56,8 +63,8 @@ macro(INSTALL_ZENOH src_path dst_path)
   )
 endmacro(INSTALL_ZENOH)
 
-INSTALL_ZENOH(${RUST_TARGET_DIR}/release/zenoh-bridge-dds lib/${PROJECT_NAME})
+INSTALL_ZENOH(${RUST_INSTALL_DIR}/release/zenoh-bridge-dds lib/${PROJECT_NAME})
 
-INSTALL_ZENOH(${RUST_TARGET_DIR}/release/zenoh-bridge-dds bin)
+INSTALL_ZENOH(${RUST_INSTALL_DIR}/release/zenoh-bridge-dds bin)
 
 ament_package()
diff --git a/README.md b/README.md
index e2a5a112..79b4f2bc 100644
--- a/README.md
+++ b/README.md
@@ -146,6 +146,15 @@ colcon build --packages-select zenoh_bridge_dds --cmake-args -DCMAKE_BUILD_TYPE=
 ```
 The `rosdep` command will automatically install *Rust* and *clang* as build dependencies.
 
+If you want to cross-compile the package on x86 device for any target, you can use the following command:
+```bash
+rosdep install --from-paths . --ignore-src -r -y
+colcon build --packages-select zenoh_bridge_dds --cmake-args -DCMAKE_BUILD_TYPE=Release  --cmake-args -DCROSS_ARCH=<target>
+```
+where `<target>` is the target architecture (e.g. `aarch64-unknown-linux-gnu`). The architechture list can be found [here](https://doc.rust-lang.org/nightly/rustc/platform-support.html).
+
+The cross-compilation uses `zig` as a linker. You can install it with instructions in [here](https://ziglang.org/download/). Also, the `zigbuild` package is required to be installed on the target device. You can install it with instructions in [here](https://github.com/rust-cross/cargo-zigbuild#installation).
+
 ## Docker image
 The **`zenoh-bridge-dds`** standalone executable is also available as a [Docker images](https://hub.docker.com/r/eclipse/zenoh-bridge-dds/tags?page=1&ordering=last_updated) for both amd64 and arm64. To get it, do:
   - `docker pull eclipse/zenoh-bridge-dds:latest` for the latest release