From the website:
"the midipix system call layer (psxscl) is not tied to any particular libc, and may thus be used for porting several different implementations. The midipix libc of choice, however, is musl: a modern libc implementation that puts special emphasis on portability and correctness, and which provides complete, high-quality, and exceptionally robust pthread- and C11 support."
Sounds like there are some good design choices there, but it's still a young project. We'll have to keep an eye on it.
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Garrett