Python's Pickle, java.io.Serializable, Ruby's marshal, plenty of examples of this, though pretty much all of them come with the caveat that they are _not_ for untrusted data sources, or even really data sources other than the application that produced them in the first place.

You can also turn on the `strict` feature for C compatibility, but without any way to get the type definitions into a C header it's kind of pointless.

I'm not interested in adding C compatibility because I don't want to write C, but I also won't go out of my way to impede others who might want to.