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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 version = match rustc_version() {
Some(version) => version,
None => {
if env::var_os("SEMIHOSTING_DENY_WARNINGS").unwrap_or_default() == "1" {
panic!("unable to determine rustc version")
}
println!(
"cargo:warning={}: unable to determine rustc version; assuming latest stable rustc",
env!("CARGO_PKG_NAME"),
);
Version::LATEST
}
};
if version.minor >= 80 {
println!(r#"cargo:rustc-check-cfg=cfg(target_arch,values("xtensa"))"#);
// Custom cfgs set by build script. Not public API.
// TODO: handle multi-line target_feature_fallback
// grep -E 'target_feature_fallback\("' build.rs | sed -E 's/^.*target_feature_fallback\(//; s/",.*$/"/' | LC_ALL=C sort -u | tr '\n' ','
println!(
r#"cargo:rustc-check-cfg=cfg(semihosting_target_feature,values("mclass","thumb-mode"))"#
);
}
let target_arch = &*env::var("CARGO_CFG_TARGET_ARCH").expect("CARGO_CFG_TARGET_ARCH not set");
if target_arch == "arm" {
let target = &*env::var("TARGET").expect("TARGET not set");
// https://github.com/rust-lang/rust/pull/123745 (includes https://github.com/rust-lang/cargo/pull/13560) merged in Rust 1.79 (nightly-2024-04-11).
if !version.probe(79, 2024, 4, 10) {
// HACK: If --target is specified, rustflags is not applied to the build
// script itself, so the build script will not be recompiled when rustflags
// is changed. That in itself is not a problem, but the old Cargo does
// not rerun the build script as well, which can be problematic.
// https://github.com/rust-lang/cargo/issues/13003
// This problem has been fixed in 1.79 so only older versions need a workaround.
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");
}
if needs_target_feature_fallback(&version) {
// See https://github.com/taiki-e/atomic-maybe-uninit/blob/HEAD/build.rs for details
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 mclass = false;
match subarch {
"v6m" | "v7em" | "v7m" | "v8m" => mclass = true,
_ => {}
}
target_feature_fallback("mclass", mclass);
// armv7-linux-androideabi and armv7-sony-vita-newlibeabihf are also enable +thumb-mode.
// https://github.com/rust-lang/rust/blob/1.78.0/compiler/rustc_target/src/spec/targets/armv7_linux_androideabi.rs#L27
// https://github.com/rust-lang/rust/blob/1.78.0/compiler/rustc_target/src/spec/targets/armv7_sony_vita_newlibeabihf.rs#L39
let thumb_mode = target.starts_with("thumb")
|| target == "armv7-linux-androideabi"
|| target == "armv7-sony-vita-newlibeabihf";
target_feature_fallback("thumb-mode", thumb_mode);
}
}
}
// 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/4rr7rMcfG), so this hack works properly on stable.
//
// [RFC2045]: https://rust-lang.github.io/rfcs/2045-target-feature.html#backend-compilation-options
fn needs_target_feature_fallback(version: &Version) -> bool {
if version.nightly {
// In this case, cfg(target_feature = "...") would work, so skip emitting our own fallback target_feature cfg.
false
} else {
true
}
}
fn target_feature_fallback(name: &str, mut has_target_feature: bool) {
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, iter, process::Command, str};
pub(crate) fn rustc_version() -> Option<Version> {
let rustc = env::var_os("RUSTC")?;
let rustc_wrapper = env::var_os("RUSTC_WRAPPER").filter(|v| !v.is_empty());
// Do not apply RUSTC_WORKSPACE_WRAPPER: https://github.com/cuviper/autocfg/issues/58#issuecomment-2067625980
let mut rustc = rustc_wrapper.into_iter().chain(iter::once(rustc));
let mut cmd = Command::new(rustc.next().unwrap());
cmd.args(rustc);
// Use verbose version output because the packagers add extra strings to the normal version output.
// Do not use long flags (--version --verbose) because clippy-deriver doesn't handle them properly.
// -vV is also matched with that cargo internally uses: https://github.com/rust-lang/cargo/blob/14b46ecc62aa671d7477beba237ad9c6a209cf5d/src/cargo/util/rustc.rs#L65
let output = cmd.arg("-vV").output().ok()?;
let verbose_version = str::from_utf8(&output.stdout).ok()?;
Version::parse(verbose_version)
}
pub(crate) struct Version {
pub(crate) minor: u32,
pub(crate) nightly: bool,
commit_date: Date,
}
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(78);
const fn stable(minor: u32) -> Self {
Self { minor, nightly: false, commit_date: Date::UNKNOWN }
}
pub(crate) fn probe(&self, minor: u32, year: u16, month: u8, day: u8) -> bool {
if self.nightly {
self.minor > minor || self.commit_date >= Date::new(year, month, day)
} else {
self.minor >= minor
}
}
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 mut digits = version.splitn(3, '.');
let major = digits.next()?;
if major != "1" {
return None;
}
let minor = digits.next()?.parse::<u32>().ok()?;
let _patch = digits.next().unwrap_or("0").parse::<u32>().ok()?;
let nightly = channel == "nightly" || channel == "dev";
// we don't refer commit date on stable/beta.
if nightly {
let commit_date = (|| {
let mut commit_date = verbose_version
.lines()
.find(|line| line.starts_with("commit-date: "))
.map(|line| &line["commit-date: ".len()..])?
.splitn(3, '-');
let year = commit_date.next()?.parse::<u16>().ok()?;
let month = commit_date.next()?.parse::<u8>().ok()?;
let day = commit_date.next()?.parse::<u8>().ok()?;
if month > 12 || day > 31 {
return None;
}
Some(Date::new(year, month, day))
})();
Some(Self { minor, nightly, commit_date: commit_date.unwrap_or(Date::UNKNOWN) })
} else {
Some(Self::stable(minor))
}
}
}
#[derive(PartialEq, PartialOrd)]
struct Date {
year: u16,
month: u8,
day: u8,
}
impl Date {
const UNKNOWN: Self = Self::new(0, 0, 0);
const fn new(year: u16, month: u8, day: u8) -> Self {
Self { year, month, day }
}
}
}
use version::{rustc_version, Version};