| use std::env; |
| use std::process::Command; |
| use std::str; |
| |
| // 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, |
| }; |
| |
| // Underscore const names stabilized in Rust 1.37: |
| // https://blog.rust-lang.org/2019/08/15/Rust-1.37.0.html#using-unnamed-const-items-for-macros |
| if minor >= 37 { |
| println!("cargo:rustc-cfg=underscore_consts"); |
| } |
| } |
| |
| fn rustc_minor_version() -> Option<u32> { |
| let rustc = env::var_os("RUSTC")?; |
| let output = Command::new(rustc).arg("--version").output().ok()?; |
| let version = str::from_utf8(&output.stdout).ok()?; |
| let mut pieces = version.split('.'); |
| if pieces.next() != Some("rustc 1") { |
| return None; |
| } |
| pieces.next()?.parse().ok() |
| } |
