I was more thinking of language features. threads.h would be nice, but, as you may know, despite it being a pretty simple API, neither glibc nor OS X libc has

I was more thinking of language features. threads.h would be nice, but, as you may know, despite it being a pretty simple API, neither glibc nor OS X libc has implemented it - there's only musl and then compatibility shims. Sigh. You could blame a lack of demand, but I'd call that chicken and egg: the whole advantage of it over pthreads in theory is portability due to standardization, but as long as the portability remains theory, so does the advantage.