use std::env; use std::process::Command; use std::str; fn main() { let compiler = match rustc_minor_version() { Some(compiler) => compiler, None => return, }; if compiler < 33 { // Exhaustive integer patterns. On older compilers, a final `_` arm is // required even if every possible integer value is otherwise covered. // https://github.com/rust-lang/rust/issues/50907 println!("cargo:rustc-cfg=no_exhaustive_int_match"); } if compiler < 36 { // extern crate alloc. // https://blog.rust-lang.org/2019/07/04/Rust-1.36.0.html#the-alloc-crate-is-stable println!("cargo:rustc-cfg=no_alloc_crate"); } if compiler < 39 { // const Vec::new. // https://doc.rust-lang.org/std/vec/struct.Vec.html#method.new println!("cargo:rustc-cfg=no_const_vec_new"); } if compiler < 40 { // #[non_exhaustive]. // https://blog.rust-lang.org/2019/12/19/Rust-1.40.0.html#non_exhaustive-structs-enums-and-variants println!("cargo:rustc-cfg=no_non_exhaustive"); } if compiler < 45 { // String::strip_prefix. // https://doc.rust-lang.org/std/primitive.str.html#method.strip_prefix println!("cargo:rustc-cfg=no_str_strip_prefix"); } if compiler < 46 { // #[track_caller]. // https://blog.rust-lang.org/2020/08/27/Rust-1.46.0.html#track_caller println!("cargo:rustc-cfg=no_track_caller"); } if compiler < 52 { // #![deny(unsafe_op_in_unsafe_fn)]. // https://github.com/rust-lang/rust/issues/71668 println!("cargo:rustc-cfg=no_unsafe_op_in_unsafe_fn_lint"); } if compiler < 53 { // Efficient intrinsics for count-leading-zeros and count-trailing-zeros // on NonZero integers stabilized in 1.53.0. On many architectures these // are more efficient than counting zeros on ordinary zeroable integers. // https://doc.rust-lang.org/std/num/struct.NonZeroU64.html#method.leading_zeros // https://doc.rust-lang.org/std/num/struct.NonZeroU64.html#method.trailing_zeros println!("cargo:rustc-cfg=no_nonzero_bitscan"); } } fn rustc_minor_version() -> Option { 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() }