vendor/serde_derive/build.rs

   1 use std::env;
   2 use std::process::Command;
   3 use std::str;
   4
   5 // The rustc-cfg strings below are *not* public API. Please let us know by
   6 // opening a GitHub issue if your build environment requires some way to enable
   7 // these cfgs other than by executing our build script.
   8 fn main() {
   9     let minor = match rustc_minor_version() {
  10         Some(minor) => minor,
  11         None => return,
  12     };
  13
  14     // Underscore const names stabilized in Rust 1.37:
  15     // https://blog.rust-lang.org/2019/08/15/Rust-1.37.0.html#using-unnamed-const-items-for-macros
  16     if minor >= 37 {
  17         println!("cargo:rustc-cfg=underscore_consts");
  18     }
  19 }
  20
  21 fn rustc_minor_version() -> Option<u32> {
  22     let rustc = env::var_os("RUSTC")?;
  23     let output = Command::new(rustc).arg("--version").output().ok()?;
  24     let version = str::from_utf8(&output.stdout).ok()?;
  25     let mut pieces = version.split('.');
  26     if pieces.next() != Some("rustc 1") {
  27         return None;
  28     }
  29     pieces.next()?.parse().ok()
  30 }