Hello Rust example

The following is an example of constructing a Rust binary that depends on a Rust library.

Rust modules are currently confined to specific directories defined in build/soong/rust/config/allowed_list.go. The following helloWorld module uses the external/rust directory to avoid modifying this list.

From the AOSP source root

mkdir -p external/rust/hello_rust/src/
mkdir -p external/rust/libsimple_printer/src/

Create external/rust/hello_rust/src/hello_rust.rs with the following contents:

use simple_printer;
fn main() {

Create external/rust/libsimple_printer/src/lib.rs file with the following contents:

pub fn print_hello_rust() {
  println!("Hello Rust!");

Create an external/rust/hello_rust/Android.bp file with the following contents:

rust_binary {
    name: "hello_rust",

    // srcs must contain a single source file, the entry point source.
    srcs: ["src/hello_rust.rs"],

    // rustlibs are Rust library dependencies. The type, rlib (static) or dylib
    // (dynamic), are chosen automatically based on module type and target
    // to avoid linkage issues.
    rustlibs: ["libsimple_printer"],

    // define any additional compilation flags
    flags: [
        "-C debug-assertions=yes",

    // cc libraries can be linked in to rust binaries and libraries through the
    // shared_libs and static_libs properties. These are not needed for this
    // simple example, so they are not included.

Create an external/rust/libsimple_printer/Android.bp file with the following contents:

// rust_library provides dylib and rlib variants.
rust_library {
    //name or stem properties must be of the form lib<crate_name><any_suffix>
    name: "libsimple_printer",

    //crate_name must match the name used in source (e.g. extern crate <name>)
    crate_name: "simple_printer",

    //srcs must contain a single source file, the entry point source
    srcs: ["src/lib.rs"],

Finally, build your hello_rust module:

source build/envsetup.sh
lunch aosp_arm64-eng
m hello_rust