1 use std::env; 2 use std::process::Command; 3 use std::str::{self, FromStr}; 4 main()5fn main() { 6 // Decide ideal limb width for arithmetic in the float parser. Refer to 7 // src/lexical/math.rs for where this has an effect. 8 let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap(); 9 match target_arch.as_str() { 10 "aarch64" | "mips64" | "powerpc64" | "x86_64" => { 11 println!("cargo:rustc-cfg=limb_width_64"); 12 } 13 _ => { 14 println!("cargo:rustc-cfg=limb_width_32"); 15 } 16 } 17 18 let minor = match rustc_minor_version() { 19 Some(minor) => minor, 20 None => return, 21 }; 22 23 // BTreeMap::get_key_value 24 // https://blog.rust-lang.org/2019/12/19/Rust-1.40.0.html#additions-to-the-standard-library 25 if minor < 40 { 26 println!("cargo:rustc-cfg=no_btreemap_get_key_value"); 27 } 28 29 // BTreeMap::remove_entry 30 // https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#library-changes 31 if minor < 45 { 32 println!("cargo:rustc-cfg=no_btreemap_remove_entry"); 33 } 34 35 // BTreeMap::retain 36 // https://blog.rust-lang.org/2021/06/17/Rust-1.53.0.html#stabilized-apis 37 if minor < 53 { 38 println!("cargo:rustc-cfg=no_btreemap_retain"); 39 } 40 } 41 rustc_minor_version() -> Option<u32>42fn rustc_minor_version() -> Option<u32> { 43 let rustc = env::var_os("RUSTC")?; 44 let output = Command::new(rustc).arg("--version").output().ok()?; 45 let version = str::from_utf8(&output.stdout).ok()?; 46 let mut pieces = version.split('.'); 47 if pieces.next() != Some("rustc 1") { 48 return None; 49 } 50 let next = pieces.next()?; 51 u32::from_str(next).ok() 52 } 53