vendor/crossbeam-epoch/build.rs

   1 // The rustc-cfg listed below are considered public API, but it is *unstable*
   2 // and outside of the normal semver guarantees:
   3 //
   4 // - `crossbeam_no_atomic_cas`
   5 //      Assume the target does *not* support atomic CAS operations.
   6 //      This is usually detected automatically by the build script, but you may
   7 //      need to enable it manually when building for custom targets or using
   8 //      non-cargo build systems that don't run the build script.
   9 //
  10 // With the exceptions mentioned above, the rustc-cfg emitted by the build
  11 // script are *not* public API.
  12
  13 #![warn(rust_2018_idioms)]
  14
  15 use std::env;
  16
  17 include!("no_atomic.rs");
  18
  19 fn main() {
  20     let target = match env::var("TARGET") {
  21         Ok(target) => target,
  22         Err(e) => {
  23             println!(
  24                 "cargo:warning={}: unable to get TARGET environment variable: {}",
  25                 env!("CARGO_PKG_NAME"),
  26                 e
  27             );
  28             return;
  29         }
  30     };
  31
  32     let cfg = match autocfg::AutoCfg::new() {
  33         Ok(cfg) => cfg,
  34         Err(e) => {
  35             println!(
  36                 "cargo:warning={}: unable to determine rustc version: {}",
  37                 env!("CARGO_PKG_NAME"),
  38                 e
  39             );
  40             return;
  41         }
  42     };
  43
  44     // Note that this is `no_*`, not `has_*`. This allows treating
  45     // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
  46     // run. This is needed for compatibility with non-cargo build systems that
  47     // don't run the build script.
  48     if NO_ATOMIC_CAS.contains(&&*target) {
  49         println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
  50     }
  51
  52     if cfg.probe_rustc_version(1, 61) {
  53         // TODO: invert cfg once Rust 1.61 became stable.
  54         println!("cargo:rustc-cfg=crossbeam_const_fn_trait_bound");
  55     }
  56
  57     println!("cargo:rerun-if-changed=no_atomic.rs");
  58 }