Last I checked Rust itself does not have a stable ABI, so there are effectively no "shared Rust libraries" outside of static linking / compiling from source. B

Last I checked Rust itself does not have a stable ABI, so there are effectively no "shared Rust libraries" outside of static linking / compiling from source. But they can and do simply use C's ABI when dynamic linking, because that is stable. Rust-to-Rust libraries generally don't bother with this because Cargo exists and that trivializes "build from source" and is far more configurable and optimizable and compile-time-provable, but it's used any time Rust uses C-compatible stuff or vise versa and that's quite common.