| use std::env; |
| use std::process::Command; |
| use std::str; |
| |
| fn main() { |
| println!("cargo:rerun-if-changed=build.rs"); |
| |
| let target = env::var("TARGET").unwrap(); |
| |
| let minor = match rustc_minor_version() { |
| Some(n) => n, |
| None => return, |
| }; |
| |
| if minor >= 26 { |
| println!("cargo:rustc-cfg=u128"); |
| } |
| |
| if !enable_use_proc_macro(&target) { |
| return; |
| } |
| println!("cargo:rustc-cfg=use_proc_macro"); |
| |
| // Rust 1.29 stabilized the necessary APIs in the `proc_macro` crate |
| if (minor >= 29 && !cfg!(procmacro2_semver_exempt)) || cfg!(feature = "nightly") { |
| println!("cargo:rustc-cfg=wrap_proc_macro"); |
| |
| if cfg!(procmacro2_semver_exempt) { |
| println!("cargo:rustc-cfg=super_unstable"); |
| // https://github.com/alexcrichton/proc-macro2/issues/147 |
| println!("cargo:rustc-cfg=procmacro2_semver_exempt"); |
| } |
| } |
| |
| if minor == 29 { |
| println!("cargo:rustc-cfg=slow_extend"); |
| } |
| } |
| |
| fn enable_use_proc_macro(target: &str) -> bool { |
| // wasm targets don't have the `proc_macro` crate, disable this feature. |
| if target.contains("wasm32") { |
| return false; |
| } |
| |
| // Otherwise, only enable it if our feature is actually enabled. |
| cfg!(feature = "proc-macro") |
| } |
| |
| fn rustc_minor_version() -> Option<u32> { |
| macro_rules! otry { |
| ($e:expr) => { |
| match $e { |
| Some(e) => e, |
| None => return None, |
| } |
| }; |
| } |
| let rustc = otry!(env::var_os("RUSTC")); |
| let output = otry!(Command::new(rustc).arg("--version").output().ok()); |
| let version = otry!(str::from_utf8(&output.stdout).ok()); |
| let mut pieces = version.split('.'); |
| if pieces.next() != Some("rustc 1") { |
| return None; |
| } |
| otry!(pieces.next()).parse().ok() |
| } |