1 #![warn(rust_2018_idioms, single_use_lifetimes)]
2
3 use autocfg::AutoCfg;
4 use std::env;
5
6 include!("no_atomic_cas.rs");
7
8 // The rustc-cfg listed below are considered public API, but it is *unstable*
9 // and outside of the normal semver guarantees:
10 //
11 // - `futures_no_atomic_cas`
12 // Assume the target does *not* support atomic CAS operations.
13 // This is usually detected automatically by the build script, but you may
14 // need to enable it manually when building for custom targets or using
15 // non-cargo build systems that don't run the build script.
16 //
17 // With the exceptions mentioned above, the rustc-cfg strings below are
18 // *not* public API. Please let us know by opening a GitHub issue if your build
19 // environment requires some way to enable these cfgs other than by executing
20 // our build script.
main()21 fn main() {
22 let target = match env::var("TARGET") {
23 Ok(target) => target,
24 Err(e) => {
25 println!(
26 "cargo:warning={}: unable to get TARGET environment variable: {}",
27 env!("CARGO_PKG_NAME"),
28 e
29 );
30 return;
31 }
32 };
33
34 // Note that this is `no_*`, not `has_*`. This allows treating
35 // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
36 // run. This is needed for compatibility with non-cargo build systems that
37 // don't run the build script.
38 if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
39 println!("cargo:rustc-cfg=futures_no_atomic_cas");
40 }
41
42 let cfg = match AutoCfg::new() {
43 Ok(cfg) => cfg,
44 Err(e) => {
45 println!(
46 "cargo:warning={}: unable to determine rustc version: {}",
47 env!("CARGO_PKG_NAME"),
48 e
49 );
50 return;
51 }
52 };
53
54 // Function like procedural macros in expressions patterns statements stabilized in Rust 1.45:
55 // https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#stabilizing-function-like-procedural-macros-in-expressions-patterns-and-statements
56 if cfg.probe_rustc_version(1, 45) {
57 println!("cargo:rustc-cfg=fn_like_proc_macro");
58 }
59
60 println!("cargo:rerun-if-changed=no_atomic_cas.rs");
61 }
62