Swift standard library on platforms without threading support?

[Joe_Groff]

@carlos4242 has been working on an alternative standard library implementation for AVR:

Hacking uSwift, a minimal stdlib... where is getOptionalDecl() defined?

OK, I'm going mad here I think. I'm putting together a minimal stdlib, partly for fun, partly for profit, who knows? Anyway, my latest stumbling block is why my code for public enum Optional<Wrapped> isn't being recognised. Looking through compiler source, the error generated (error: broken standard library: cannot find Optional type) seems to be coming from calling getOptionalDecl() and getting back a nil. The thing is, I cannot find where this function exists! There are lots of calls to i…

It would be interesting to add a configuration flag to disable threading support in the "normal" runtime and standard library. Nobody's done that yet to my knowledge. For that specific issue, though, it is incorrect to avoid using <atomic> in a single-threaded system; I'm not sure why that #if is there. <atomic> is still meaningful for a single-threaded system for atomicity relative to signals and other preemption mechanisms.