| use std::env; |
| use std::process::Command; |
| use std::str::{self, FromStr}; |
| |
| // The rustc-cfg strings below are *not* public API. Please let us know by |
| // opening a GitHub issue if your build environment requires some way to enable |
| // these cfgs other than by executing our build script. |
| fn main() { |
| let minor = match rustc_minor_version() { |
| Some(minor) => minor, |
| None => return, |
| }; |
| |
| let target = env::var("TARGET").unwrap(); |
| let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten"; |
| |
| // 128-bit integers stabilized in Rust 1.26: |
| // https://blog.rust-lang.org/2018/05/10/Rust-1.26.html |
| // |
| // Disabled on Emscripten targets as Emscripten doesn't |
| // currently support integers larger than 64 bits. |
| if minor >= 26 && !emscripten { |
| println!("cargo:rustc-cfg=integer128"); |
| } |
| |
| // #[must_use] on functions stabilized in Rust 1.27: |
| // https://blog.rust-lang.org/2018/06/21/Rust-1.27.html |
| if minor >= 27 { |
| println!("cargo:rustc-cfg=must_use_return"); |
| } |
| |
| // MaybeUninit<T> stabilized in Rust 1.36: |
| // https://blog.rust-lang.org/2019/07/04/Rust-1.36.0.html |
| if minor >= 36 { |
| println!("cargo:rustc-cfg=maybe_uninit"); |
| } |
| } |
| |
| 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() |
| } |