The requirements for stability being well known do not make them easy to follow. If you really want stability, you basically have to eschew all use of structs,

The requirements for stability being well known do not make them easy to follow. If you really want stability, you basically have to eschew all use of structs, or add struct versioning, to begin with. Then you can't add or remove parameters from functions, but instead must add new functions only. Those are of course just the first two things; in practice, most libraries do not even try to follow them, and just bump the SONAME version with anything besides a minor bugfix release.