// Opaque stand-in: the tutorial does not provide the actual Stats fields.
#[repr(C)] struct Stats { _opaque: [u8;0] }
use std::ffi::c_void;
#[repr(C, packed)]
struct ByteSlice { data: *const u8, len: i64 }
#[repr(C, packed)]
struct I32Slice { data: *mut i32, len: i64 }
#[repr(C, packed)]
struct GooseBuilder { header: *mut c_void, stack: *mut c_void }
unsafe extern "C" {
    #[link_name = "cbrt"] fn cube_root(x: f64) -> f64;
    fn hypot(x: f64, y: f64) -> f64;
    fn crc32_bytes(s: ByteSlice) -> u32;
    fn stats_of(xs: I32Slice, out: *mut Stats);
    fn c_version(out: GooseBuilder);
}