2 use std::process::Command;
3 use std::str::{self, FromStr};
6 println!("cargo:rerun-if-changed=build.rs");
8 // Decide ideal limb width for arithmetic in the float parser. Refer to
9 // src/lexical/math.rs for where this has an effect.
10 let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
11 match target_arch.as_str() {
12 "aarch64" | "mips64" | "powerpc64" | "x86_64" => {
13 println!("cargo:rustc-cfg=limb_width_64");
16 println!("cargo:rustc-cfg=limb_width_32");
20 let minor = match rustc_minor_version() {
25 // BTreeMap::get_key_value
26 // https://blog.rust-lang.org/2019/12/19/Rust-1.40.0.html#additions-to-the-standard-library
28 println!("cargo:rustc-cfg=no_btreemap_get_key_value");
31 // BTreeMap::remove_entry
32 // https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#library-changes
34 println!("cargo:rustc-cfg=no_btreemap_remove_entry");
38 // https://blog.rust-lang.org/2021/06/17/Rust-1.53.0.html#stabilized-apis
40 println!("cargo:rustc-cfg=no_btreemap_retain");
44 fn rustc_minor_version() -> Option<u32> {
45 let rustc = env::var_os("RUSTC")?;
46 let output = Command::new(rustc).arg("--version").output().ok()?;
47 let version = str::from_utf8(&output.stdout).ok()?;
48 let mut pieces = version.split('.');
49 if pieces.next() != Some("rustc 1") {
52 let next = pieces.next()?;
53 u32::from_str(next).ok()