Build Rules

The Android build system (Soong) supports Rust via a number of modules:

Module Type Description
rust_binary Produces a Rust binary.
rust_library Produces a Rust library, and provides both rlib and dylib variants.
rust_ffi Produces a Rust C library usable by cc modules, and provides both static and shared variants.
rust_proc_macro Produces a proc-macro Rust library. These are analogous to compiler plugins.
rust_test Produces a Rust test binary that uses the standard Rust test harness.
rust_fuzz Produces a Rust fuzz binary leveraging libfuzzer.
rust_protobuf Generates source and produces a Rust library that provides an interface for a particular protobuf.
rust_bindgen Generates source and produces a Rust library containing Rust bindings to C libraries.

We will look at rust_binary and rust_library next.

Additional items speaker may mention:

  • Cargo is not optimized for multi-language repos, and also downloads packages from the internet.
  • For compliance and performance, Android must have crates in-tree. It must also interop with C/C++/Java code. Soong fills that gap.
  • Soong has many similarities to Bazel, which is the open-source variant of Blaze (used in google3).
  • Fun fact: Data from Star Trek is a Soong-type Android.