How does Rust do it?
For normal libraries, an and b could depend on different versions, so this could be a problem. The name mangling scheme allows for a “disambiguator” to differentiate the two, I believe that the version is used here but the documentation for it does not say if there’s more than that.
Also, Rust compiles the whole world at once, so any ABI breakage from mixing code from different compiler versions doesn't happen. (Editions are different thing from compiler versions, a single version of the compiler supports multiple editions.)