Libmill runs in following environments:
Microarchitecture: x86_64, ARM
Compiler: gcc, clang
Operating system: Linux, OSX, FreeBSD, OpenBSD, NetBSD, DragonFlyBSD
Whether it works in different environments is not known - please, do report any successes or failures to the project mailing list.
It only works with gcc and clang now, no longer with windows, and is sprinkled with asm()s. That doesn't fly with the CPython is portable. I don't know how these go-like features could be created with ANSI C, but I'd love to be proven wrong.