rust metacall-sys crate: enhance searching with RPATH handling for C Libs discovery across platforms (binary) and improve metacall-sys cargo (#576)

* feat(rs metacall-sys): enhance searching with RPATH handling for library discovery across platforms (binary)

* Update Cargo.toml

* Update Cargo.toml

* Update lib.rs

---------

Co-authored-by: Vicente Eduardo Ferrer Garcia <7854099+viferga@users.noreply.github.com>

Author: fahdfady

source/ports/rs_port/sys/Cargo.toml

@@ -1,7 +1,15 @@
 [package]
 name = "metacall-sys"
-version = "0.1.0"
-repository = "https://github.com/metacall/core/tree/develop/source/ports/rs_port"
+version = "0.1.1"
+repository = "https://github.com/metacall/core/tree/develop/source/ports/rs_port/sys"
+keywords = ["ffi", "bindings", "metacall"]
 edition = "2021"
 license = "Apache-2.0"
 description = "Crate for finding metacall library in the system."
+
+[lib]
+crate-type = ["lib"]
+doctest = false
+edition = "2021"
+name = "metacall_sys"
+path = "src/lib.rs"

source/ports/rs_port/sys/src/lib.rs

@@ -188,6 +188,45 @@ fn define_library_search_path(env_var: &str, separator: &str, path: &Path) -> St
     format!("{}={}", env_var, combined)
 }
 
+/// Set RPATH for runtime library discovery
+/// This binaries work outside cargo
+fn set_rpath(lib_path: &Path) {
+    let path_str = lib_path.to_str().unwrap();
+
+    #[cfg(target_os = "linux")]
+    {
+        // On Linux, use RPATH with $ORIGIN for relocatable binaries
+        println!("cargo:rustc-link-arg=-Wl,-rpath,{}", path_str);
+        // Also set a backup rpath relative to the executable location
+        println!("cargo:rustc-link-arg=-Wl,-rpath,$ORIGIN");
+        println!("cargo:rustc-link-arg=-Wl,-rpath,$ORIGIN/../lib");
+    }
+
+    #[cfg(target_os = "macos")]
+    {
+        // On macOS, use @rpath and @loader_path
+        println!("cargo:rustc-link-arg=-Wl,-rpath,{}", path_str);
+        // Also set loader-relative paths for relocatable binaries
+        println!("cargo:rustc-link-arg=-Wl,-rpath,@loader_path");
+        println!("cargo:rustc-link-arg=-Wl,-rpath,@loader_path/../lib");
+    }
+
+    #[cfg(target_os = "aix")]
+    {
+        // Add default system library paths to avoid breaking standard lookup
+        println!("cargo:rustc-link-arg=-Wl,-blibpath:{}:/usr/lib:/lib", path_str);
+    }
+
+    #[cfg(target_os = "windows")]
+    {
+        // Windows doesn't use RPATH, but we can inform the user
+        println!(
+            "cargo:warning=On Windows, make sure {} is in your PATH or next to your executable",
+            path_str
+        );
+    }
+}
+
 pub fn build() {
     // When running tests from CMake
     if let Ok(val) = env::var("PROJECT_OUTPUT_DIR") {
@@ -216,6 +255,9 @@ pub fn build() {
                 println!("cargo:rustc-link-search=native={}", lib_path.path.display());
                 println!("cargo:rustc-link-lib=dylib={}", lib_path.library);
 
+                // Set RPATH so the binary can find libraries at runtime
+                set_rpath(&lib_path.path);
+
                 // Set the runtime environment variable for finding the library during tests
                 #[cfg(target_os = "linux")]
                 const ENV_VAR: &str = "LD_LIBRARY_PATH";