vendor/semver/build.rs

   1 use std::env;
   2 use std::process::Command;
   3 use std::str;
   4
   5 fn main() {
   6     let compiler = match rustc_minor_version() {
   7         Some(compiler) => compiler,
   8         None => return,
   9     };
  10
  11     if compiler < 33 {
  12         // Exhaustive integer patterns. On older compilers, a final `_` arm is
  13         // required even if every possible integer value is otherwise covered.
  14         // https://github.com/rust-lang/rust/issues/50907
  15         println!("cargo:rustc-cfg=no_exhaustive_int_match");
  16     }
  17
  18     if compiler < 36 {
  19         // extern crate alloc.
  20         // https://blog.rust-lang.org/2019/07/04/Rust-1.36.0.html#the-alloc-crate-is-stable
  21         println!("cargo:rustc-cfg=no_alloc_crate");
  22     }
  23
  24     if compiler < 39 {
  25         // const Vec::new.
  26         // https://doc.rust-lang.org/std/vec/struct.Vec.html#method.new
  27         println!("cargo:rustc-cfg=no_const_vec_new");
  28     }
  29
  30     if compiler < 40 {
  31         // #[non_exhaustive].
  32         // https://blog.rust-lang.org/2019/12/19/Rust-1.40.0.html#non_exhaustive-structs-enums-and-variants
  33         println!("cargo:rustc-cfg=no_non_exhaustive");
  34     }
  35
  36     if compiler < 45 {
  37         // String::strip_prefix.
  38         // https://doc.rust-lang.org/std/primitive.str.html#method.strip_prefix
  39         println!("cargo:rustc-cfg=no_str_strip_prefix");
  40     }
  41
  42     if compiler < 46 {
  43         // #[track_caller].
  44         // https://blog.rust-lang.org/2020/08/27/Rust-1.46.0.html#track_caller
  45         println!("cargo:rustc-cfg=no_track_caller");
  46     }
  47
  48     if compiler < 52 {
  49         // #![deny(unsafe_op_in_unsafe_fn)].
  50         // https://github.com/rust-lang/rust/issues/71668
  51         println!("cargo:rustc-cfg=no_unsafe_op_in_unsafe_fn_lint");
  52     }
  53
  54     if compiler < 53 {
  55         // Efficient intrinsics for count-leading-zeros and count-trailing-zeros
  56         // on NonZero integers stabilized in 1.53.0. On many architectures these
  57         // are more efficient than counting zeros on ordinary zeroable integers.
  58         // https://doc.rust-lang.org/std/num/struct.NonZeroU64.html#method.leading_zeros
  59         // https://doc.rust-lang.org/std/num/struct.NonZeroU64.html#method.trailing_zeros
  60         println!("cargo:rustc-cfg=no_nonzero_bitscan");
  61     }
  62 }
  63
  64 fn rustc_minor_version() -> Option<u32> {
  65     let rustc = env::var_os("RUSTC")?;
  66     let output = Command::new(rustc).arg("--version").output().ok()?;
  67     let version = str::from_utf8(&output.stdout).ok()?;
  68     let mut pieces = version.split('.');
  69     if pieces.next() != Some("rustc 1") {
  70         return None;
  71     }
  72     pieces.next()?.parse().ok()
  73 }