Introduce cfg attribute for ROS distro

Author: nnmm

rclrs/build.rs

@@ -3,8 +3,23 @@ use std::fs::read_dir;
 use std::path::{Path, PathBuf};
 
 const AMENT_PREFIX_PATH: &str = "AMENT_PREFIX_PATH";
+const ROS_DISTRO: &str = "ROS_DISTRO";
+
+fn get_env_var_or_abort(env_var: &'static str) -> String {
+    if let Ok(value) = env::var(env_var) {
+        value
+    } else {
+        panic!(
+            "{} environment variable not set - please source ROS 2 installation first.",
+            env_var
+        );
+    }
+}
 
 fn main() {
+    let distro = get_env_var_or_abort(ROS_DISTRO);
+    println!("cargo:rustc-cfg=distro=\"{distro}\"");
+
     let mut builder = bindgen::Builder::default()
         .header("src/rcl_wrapper.h")
         .derive_copy(false)
@@ -39,47 +54,41 @@ fn main() {
     //
     // See REP 122 for more details: https://www.ros.org/reps/rep-0122.html#filesystem-layout
 
-    if let Ok(ament_prefix_paths) = env::var(AMENT_PREFIX_PATH) {
-        for ament_prefix_path in ament_prefix_paths.split(':').map(Path::new) {
-            // Locate the ament index
-            let ament_index = ament_prefix_path.join("share/ament_index/resource_index/packages");
-            if !ament_index.is_dir() {
-                continue;
-            }
+    let ament_prefix_paths = get_env_var_or_abort(AMENT_PREFIX_PATH);
+    for ament_prefix_path in ament_prefix_paths.split(':').map(Path::new) {
+        // Locate the ament index
+        let ament_index = ament_prefix_path.join("share/ament_index/resource_index/packages");
+        if !ament_index.is_dir() {
+            continue;
+        }
 
-            // Old-style include directory
-            let include_dir = ament_prefix_path.join("include");
+        // Old-style include directory
+        let include_dir = ament_prefix_path.join("include");
 
-            // Including the old-style packages
-            builder = builder.clang_arg(format!("-isystem{}", include_dir.display()));
+        // Including the old-style packages
+        builder = builder.clang_arg(format!("-isystem{}", include_dir.display()));
 
-            // Search for and include new-style-converted package paths
-            for dir_entry in read_dir(&ament_index).unwrap().filter_map(|p| p.ok()) {
-                let package = dir_entry.file_name();
-                let package_include_dir = include_dir.join(&package);
+        // Search for and include new-style-converted package paths
+        for dir_entry in read_dir(&ament_index).unwrap().filter_map(|p| p.ok()) {
+            let package = dir_entry.file_name();
+            let package_include_dir = include_dir.join(&package);
 
-                if package_include_dir.is_dir() {
-                    let new_style_include_dir = package_include_dir.join(&package);
+            if package_include_dir.is_dir() {
+                let new_style_include_dir = package_include_dir.join(&package);
 
-                    // CycloneDDS is a special case - it needs to be included as if it were a new-style path, but
-                    // doesn't actually have a secondary folder within it called "CycloneDDS"
-                    // TODO(jhdcs): if this changes in future, remove this check
-                    if package == "CycloneDDS" || new_style_include_dir.is_dir() {
-                        builder =
-                            builder.clang_arg(format!("-isystem{}", package_include_dir.display()));
-                    }
+                // CycloneDDS is a special case - it needs to be included as if it were a new-style path, but
+                // doesn't actually have a secondary folder within it called "CycloneDDS"
+                // TODO(jhdcs): if this changes in future, remove this check
+                if package == "CycloneDDS" || new_style_include_dir.is_dir() {
+                    builder =
+                        builder.clang_arg(format!("-isystem{}", package_include_dir.display()));
                 }
             }
-
-            // Link the native libraries
-            let library_path = ament_prefix_path.join("lib");
-            println!("cargo:rustc-link-search=native={}", library_path.display());
         }
-    } else {
-        panic!(
-            "{} environment variable not set - please source ROS 2 installation first.",
-            AMENT_PREFIX_PATH
-        );
+
+        // Link the native libraries
+        let library_path = ament_prefix_path.join("lib");
+        println!("cargo:rustc-link-search=native={}", library_path.display());
     }
 
     println!("cargo:rustc-link-lib=dylib=rcl");

rclrs/src/lib.rs

@@ -54,9 +54,15 @@ pub fn spin_once(node: &Node, timeout: Option<Duration>) -> Result<(), RclReturn
 ///
 /// This function additionally checks that the context is still valid.
 pub fn spin(node: &Node) -> Result<(), RclReturnCode> {
+    // The context_is_valid functions exists only to abstract away ROS distro differences
+    #[cfg(distro = "foxy")]
     // SAFETY: No preconditions for this function.
-    // The mutability of the argument has changed between ROS 2 versions, hence the extra `as _`
-    while unsafe { rcl_context_is_valid(&mut *node.context.lock() as _) } {
+    let context_is_valid = || unsafe { rcl_context_is_valid(&mut *node.context.lock()) };
+    #[cfg(not(distro = "foxy"))]
+    // SAFETY: No preconditions for this function.
+    let context_is_valid = || unsafe { rcl_context_is_valid(&*node.context.lock()) };
+
+    while context_is_valid() {
         if let Some(error) = spin_once(node, None).err() {
             match error {
                 RclReturnCode::Timeout => continue,