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44 lines
983 B

use std::env;
use std::process::Command;
use std::str::{self, FromStr};
fn main(){
let minor = match rustc_minor_version() {
Some(minor) => minor,
None => return,
};
// const fn stabilized in Rust 1.31:
if minor >= 31 {
println!("cargo:rustc-cfg=bitflags_const_fn");
}
}
fn rustc_minor_version() -> Option<u32> {
let rustc = match env::var_os("RUSTC") {
Some(rustc) => rustc,
None => return None,
};
let output = match Command::new(rustc).arg("--version").output() {
Ok(output) => output,
Err(_) => return None,
};
let version = match str::from_utf8(&output.stdout) {
Ok(version) => version,
Err(_) => return None,
};
let mut pieces = version.split('.');
if pieces.next() != Some("rustc 1") {
return None;
}
let next = match pieces.next() {
Some(next) => next,
None => return None,
};
u32::from_str(next).ok()
}