This implementation uses async/await, data structures from Rust's standard library (alloc crate), plus streams and channels (30 dependencies in total), so it's pretty fancy for a "no_std" project.

Bare-bones Rust executables can start at about 3.5KB, and code size increase on top of that is comparable to C or C++. Rust can be a "portable assembler" if you write code in such style. It can also generate lots of code if you lean into generics (same issue as with C++ templates).