the only known metric for code complexity is as number of lines grows complexity grows
I'll just leave this here:
And that's... bad? Culture shock, sure, but this looks like fairly clean APL-style C to me. I would have wrapped some of those lines though.
Of course it's bad. Is that a serious question?
No, it was rhetorical, because it's obviously (to an APL-family programmer), not bad!
Your cultural prejudice is showing. There are good reasons APL is written the way it is, and this example is simply bringing those benefits to C by writing it in the dense APL style. There are other APL derivatives, like J[1] that are written in C the same way. These projects are well-maintained. They aren't collapsing under a load of technical debt. The style works. To them, it's clean code.