1 use std::env; 2 use std::process::Command; 3 use std::str; 4 main()5fn main() { 6 println!("cargo:rerun-if-changed=build.rs"); 7 8 let version = match rustc_version() { 9 Some(version) => version, 10 None => return, 11 }; 12 13 if version.minor >= 80 { 14 println!("cargo:rustc-check-cfg=cfg(no_literal_fromstr)"); 15 println!("cargo:rustc-check-cfg=cfg(feature, values(\"protocol_feature_paste\"))"); 16 } 17 18 if version.minor < 54 { 19 // https://github.com/rust-lang/rust/pull/84717 20 println!("cargo:rustc-cfg=no_literal_fromstr"); 21 } 22 } 23 24 struct RustcVersion { 25 minor: u32, 26 } 27 rustc_version() -> Option<RustcVersion>28fn rustc_version() -> Option<RustcVersion> { 29 let rustc = env::var_os("RUSTC")?; 30 let output = Command::new(rustc).arg("--version").output().ok()?; 31 let version = str::from_utf8(&output.stdout).ok()?; 32 let mut pieces = version.split('.'); 33 if pieces.next() != Some("rustc 1") { 34 return None; 35 } 36 let minor = pieces.next()?.parse().ok()?; 37 Some(RustcVersion { minor }) 38 } 39