Related Work
There are many great alternatives out there aiming at a similar set of problems.
General purpose binding generators
GlueGun's distinguishing characteristic is its focus on convention-over-configuration and covering the whole workflow. Our goal is that no annotations are needed for the common case and that custom plugins are available and feel natural to use.
Mozilla's UniFFI has a similar design. It uses either proc macros or an external IDL file ("UDL") to specify the interface. It is focused on supporting phone deployment but includes some other languages.
Diplomat was initially built for ICU. It has some support for other languages. External tools are possible but not integrated into the primary workflow.
Language specific bindings
cxx
duchess
pyo3
cbindgen
bindgen