> The second case is far more interesting in my experience, and since it cannot be solved by off-the-shelf solutions tends to crop up more often: integration with (or implementation of) programming languages that do use a garbage collector. Servo needs to do this for integrating with the Spidermonkey JS engine and luster needed to do this for implementing the GC of its Lua VM. boa, a pure Rust JS runtime, uses the gc crate to back its garbage collector.