[pjmlp]

That is news to me, where is the ABI specified, given that cargo is yet to support binary crates?

> you can't link a library compiled with clang to one compiled with MSVC

You surely can, provided it is made available as DLL or COM.

[fluffything]

Rust actually supports multiple ABIs and you can pick which one to use.

The one I use for maximum portability is the C ABI defined in the ISO C standard and on the platform docs (eg the Itanium ABI specified eg in the x86psABI document on Linux).