fn main() {
let rustc = std::env::var_os("RUSTC");
let rustc = rustc.as_ref().map(std::path::Path::new).unwrap_or_else(|| "rustc".as_ref());
let output = std::process::Command::new(rustc)
.arg("--version")
.output()
.unwrap_or_else(|error| panic!("Failed to run `{:?} --version`: {:?}", rustc, error));
assert!(output.status.success(), "{:?} -- version returned non-zero exit code", rustc);
let stdout = String::from_utf8(output.stdout).expect("rustc produced non-UTF-8 output");
let version_prefix = "rustc ";
if !stdout.starts_with(version_prefix) {
panic!("unexpected rustc output: {}", stdout);
}
let version = &stdout[version_prefix.len()..];
let end = version.find(&[' ', '-'] as &[_]).unwrap_or(version.len());
let version = &version[..end];
let mut version_components = version.split('.');
let major = version_components.next().unwrap();
assert_eq!(major, "1", "Unexpected Rust major version");
let minor = version_components
.next()
.unwrap_or("0")
.parse::<u64>()
.expect("invalid Rust minor version");
for version in &[46] {
if *version <= minor {
println!("cargo:rustc-cfg=rust_v_1_{}", version);
}
}
}