[thenewwazoo]

It looks like bog-standard K&R style[0] to me. Exceedingly common, in my experience. What about it strikes you as odd?

[0] https://en.wikipedia.org/wiki/Indentation_style#K&R_style

[eqvinox]

It's not K&R; the function opening brace is off, there's no empty lines inside functions, and goto labels are indented. (And indent is 4 spaces, most K&R is Tabs.)

Combined with the absence of any comments, the source looks very "optically dense" in this style.