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// SPDX-License-Identifier: Apache-2.0 OR MIT
// The rustc-cfg emitted by the build script are *not* public API.
use std::env;
fn main() {
println!("cargo:rerun-if-changed=build.rs");
let target = &*env::var("TARGET").expect("TARGET not set");
let target_arch = &*env::var("CARGO_CFG_TARGET_ARCH").expect("CARGO_CFG_TARGET_ARCH not set");
if target_arch == "arm" {
// HACK: If --target is specified, rustflags is not applied to the build
// script itself, so the build script will not be rerun when these are changed.
//
// Ideally, the build script should be rebuilt when CARGO_ENCODED_RUSTFLAGS
// is changed, but since it is an environment variable set by cargo,
// as of 1.62.0-nightly, specifying it as rerun-if-env-changed does not work.
println!("cargo:rerun-if-env-changed=CARGO_ENCODED_RUSTFLAGS");
println!("cargo:rerun-if-env-changed=RUSTFLAGS");
println!("cargo:rerun-if-env-changed=CARGO_BUILD_RUSTFLAGS");
let mut target_upper = target.replace(['-', '.'], "_");
target_upper.make_ascii_uppercase();
println!("cargo:rerun-if-env-changed=CARGO_TARGET_{target_upper}_RUSTFLAGS");
let version = match rustc_version() {
Some(version) => version,
None => {
println!(
"cargo:warning={}: unable to determine rustc version; assuming latest stable rustc",
env!("CARGO_PKG_NAME"),
);
Version::LATEST
}
};
if target.starts_with("thumb") {
target_feature_if("thumb-mode", true, &version);
}
// See portable-atomic and atomic-maybe-uninit's build.rs for more
let mut subarch =
target.strip_prefix("arm").or_else(|| target.strip_prefix("thumb")).unwrap();
subarch = subarch.strip_prefix("eb").unwrap_or(subarch); // ignore endianness
subarch = subarch.split('-').next().unwrap(); // ignore vender/os/env
subarch = subarch.split('.').next().unwrap(); // ignore .base/.main suffix
let mut is_mclass = false;
match subarch {
"v6m" | "v7em" | "v7m" | "v8m" => is_mclass = true,
_ => {}
}
target_feature_if("mclass", is_mclass, &version);
}
}
fn target_feature_if(name: &str, mut has_target_feature: bool, version: &Version) {
// HACK: Currently, it seems that the only way to handle unstable target
// features on the stable is to parse the `-C target-feature` in RUSTFLAGS.
//
// - #[cfg(target_feature = "unstable_target_feature")] doesn't work on stable.
// - CARGO_CFG_TARGET_FEATURE excludes unstable target features on stable.
//
// As mentioned in the [RFC2045], unstable target features are also passed to LLVM
// (e.g., https://godbolt.org/z/TfaEx95jc), so this hack works properly on stable.
//
// [RFC2045]: https://rust-lang.github.io/rfcs/2045-target-feature.html#backend-compilation-options
if version.nightly {
// In this case, cfg(target_feature = "...") would work, so skip emitting our own target_feature cfg.
return;
}
if let Some(rustflags) = env::var_os("CARGO_ENCODED_RUSTFLAGS") {
for mut flag in rustflags.to_string_lossy().split('\x1f') {
flag = flag.strip_prefix("-C").unwrap_or(flag);
if let Some(flag) = flag.strip_prefix("target-feature=") {
for s in flag.split(',') {
// TODO: Handles cases where a specific target feature
// implicitly enables another target feature.
match (s.as_bytes().first(), s.as_bytes().get(1..)) {
(Some(b'+'), Some(f)) if f == name.as_bytes() => has_target_feature = true,
(Some(b'-'), Some(f)) if f == name.as_bytes() => has_target_feature = false,
_ => {}
}
}
}
}
}
if has_target_feature {
println!("cargo:rustc-cfg=semihosting_target_feature=\"{name}\"");
}
}
mod version {
use std::{env, process::Command, str};
pub(crate) fn rustc_version() -> Option<Version> {
let rustc = env::var_os("RUSTC")?;
// Use verbose version output because the packagers add extra strings to the normal version output.
let output = Command::new(rustc).args(["--version", "--verbose"]).output().ok()?;
let verbose_version = str::from_utf8(&output.stdout).ok()?;
Version::parse(verbose_version)
}
pub(crate) struct Version {
pub(crate) nightly: bool,
}
impl Version {
// The known latest stable version. If we unable to determine
// the rustc version, we assume this is the current version.
// It is no problem if this is older than the actual latest stable.
pub(crate) const LATEST: Self = Self::stable();
const fn stable() -> Self {
Self { nightly: false }
}
pub(crate) fn parse(verbose_version: &str) -> Option<Self> {
let mut release = verbose_version
.lines()
.find(|line| line.starts_with("release: "))
.map(|line| &line["release: ".len()..])?
.splitn(2, '-');
let _version = release.next().unwrap();
let channel = release.next().unwrap_or_default();
let nightly = channel == "nightly" || channel == "dev";
Some(Self { nightly })
}
}
}
use version::{rustc_version, Version};