extern crate autocfg; use std::env; fn main() { let ac = autocfg::new(); if ac.probe_type("i128") { println!("cargo:rustc-cfg=has_i128"); } else if env::var_os("CARGO_FEATURE_I128").is_some() { panic!("i128 support was not detected!"); } autocfg::rerun_path(file!()); }