449 lines
22 KiB
Rust
449 lines
22 KiB
Rust
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// SPDX-License-Identifier: Apache-2.0 OR MIT
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// The rustc-cfg emitted by the build script are *not* public API.
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#![allow(clippy::match_same_arms, clippy::needless_pass_by_value)]
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#[path = "version.rs"]
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mod version;
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use version::{rustc_version, Version};
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use std::{env, str};
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include!("no_atomic.rs");
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fn main() {
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println!("cargo:rerun-if-changed=build.rs");
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println!("cargo:rerun-if-changed=no_atomic.rs");
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println!("cargo:rerun-if-changed=version.rs");
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#[cfg(feature = "unsafe-assume-single-core")]
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println!("cargo:rustc-cfg=portable_atomic_unsafe_assume_single_core");
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#[cfg(feature = "s-mode")]
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println!("cargo:rustc-cfg=portable_atomic_s_mode");
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#[cfg(feature = "force-amo")]
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println!("cargo:rustc-cfg=portable_atomic_force_amo");
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#[cfg(feature = "disable-fiq")]
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println!("cargo:rustc-cfg=portable_atomic_disable_fiq");
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let target = &*env::var("TARGET").expect("TARGET not set");
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let target_arch = &*env::var("CARGO_CFG_TARGET_ARCH").expect("CARGO_CFG_TARGET_ARCH not set");
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let target_os = &*env::var("CARGO_CFG_TARGET_OS").expect("CARGO_CFG_TARGET_OS not set");
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// HACK: If --target is specified, rustflags is not applied to the build
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// script itself, so the build script will not be rerun when these are changed.
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//
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// Ideally, the build script should be rebuilt when CARGO_ENCODED_RUSTFLAGS
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// is changed, but since it is an environment variable set by cargo,
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// as of 1.62.0-nightly, specifying it as rerun-if-env-changed does not work.
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println!("cargo:rerun-if-env-changed=CARGO_ENCODED_RUSTFLAGS");
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println!("cargo:rerun-if-env-changed=RUSTFLAGS");
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println!("cargo:rerun-if-env-changed=CARGO_BUILD_RUSTFLAGS");
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let mut target_upper = target.replace(|c: char| c == '-' || c == '.', "_");
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target_upper.make_ascii_uppercase();
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println!("cargo:rerun-if-env-changed=CARGO_TARGET_{}_RUSTFLAGS", target_upper);
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let version = match rustc_version() {
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Some(version) => version,
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None => {
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println!(
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"cargo:warning={}: unable to determine rustc version; assuming latest stable rustc (1.{})",
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env!("CARGO_PKG_NAME"),
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Version::LATEST.minor
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);
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Version::LATEST
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}
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};
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// Note that this is `no_`*, not `has_*`. This allows treating as the latest
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// stable rustc is used when the build script doesn't run. This is useful
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// for non-cargo build systems that don't run the build script.
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// atomic_min_max stabilized in Rust 1.45 (nightly-2020-05-30): https://github.com/rust-lang/rust/pull/72324
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if !version.probe(45, 2020, 5, 29) {
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println!("cargo:rustc-cfg=portable_atomic_no_atomic_min_max");
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}
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// track_caller stabilized in Rust 1.46 (nightly-2020-07-02): https://github.com/rust-lang/rust/pull/72445
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if !version.probe(46, 2020, 7, 1) {
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println!("cargo:rustc-cfg=portable_atomic_no_track_caller");
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}
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// unsafe_op_in_unsafe_fn stabilized in Rust 1.52 (nightly-2021-03-11): https://github.com/rust-lang/rust/pull/79208
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if !version.probe(52, 2021, 3, 10) {
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println!("cargo:rustc-cfg=portable_atomic_no_unsafe_op_in_unsafe_fn");
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}
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// https://github.com/rust-lang/rust/pull/84662 merged in Rust 1.56 (nightly-2021-08-02).
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if !version.probe(56, 2021, 8, 1) {
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println!("cargo:rustc-cfg=portable_atomic_no_core_unwind_safe");
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}
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// const_raw_ptr_deref stabilized in Rust 1.58 (nightly-2021-11-15): https://github.com/rust-lang/rust/pull/89551
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if !version.probe(58, 2021, 11, 14) {
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println!("cargo:rustc-cfg=portable_atomic_no_const_raw_ptr_deref");
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}
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// https://github.com/rust-lang/rust/pull/98383 merged in Rust 1.64 (nightly-2022-07-19).
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if !version.probe(64, 2022, 7, 18) {
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println!("cargo:rustc-cfg=portable_atomic_no_stronger_failure_ordering");
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}
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// https://github.com/rust-lang/rust/pull/114790 merged in nightly-2023-08-24
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if !version.probe(74, 2023, 8, 23) {
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println!("cargo:rustc-cfg=portable_atomic_no_asm_maybe_uninit");
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}
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// asm stabilized in Rust 1.59 (nightly-2021-12-16): https://github.com/rust-lang/rust/pull/91728
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let no_asm = !version.probe(59, 2021, 12, 15);
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if no_asm {
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if version.nightly
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&& version.probe(46, 2020, 6, 20)
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&& ((target_arch != "x86" && target_arch != "x86_64") || version.llvm >= 10)
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&& is_allowed_feature("asm")
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{
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// This feature was added in Rust 1.45 (nightly-2020-05-20), but
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// concat! in asm! requires Rust 1.46 (nightly-2020-06-21).
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// x86 intel syntax requires LLVM 10 (since Rust 1.53, the minimum
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// external LLVM version is 10+: https://github.com/rust-lang/rust/pull/83387).
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// The part of this feature we use has not been changed since nightly-2020-06-21
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// until it was stabilized in nightly-2021-12-16, so it can be safely enabled in
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// nightly, which is older than nightly-2021-12-16.
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println!("cargo:rustc-cfg=portable_atomic_unstable_asm");
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}
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println!("cargo:rustc-cfg=portable_atomic_no_asm");
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}
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// feature(cfg_target_has_atomic) stabilized in Rust 1.60 (nightly-2022-02-11): https://github.com/rust-lang/rust/pull/93824
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if !version.probe(60, 2022, 2, 10) {
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if version.nightly
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&& version.probe(40, 2019, 10, 13)
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&& is_allowed_feature("cfg_target_has_atomic")
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{
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// This feature has not been changed since the change in Rust 1.40 (nightly-2019-10-14)
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// until it was stabilized in nightly-2022-02-11, so it can be safely enabled in
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// nightly, which is older than nightly-2022-02-11.
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println!("cargo:rustc-cfg=portable_atomic_unstable_cfg_target_has_atomic");
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} else {
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println!("cargo:rustc-cfg=portable_atomic_no_cfg_target_has_atomic");
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let target = &*convert_custom_linux_target(target);
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if NO_ATOMIC_CAS.contains(&target) {
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println!("cargo:rustc-cfg=portable_atomic_no_atomic_cas");
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}
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if NO_ATOMIC_64.contains(&target) {
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println!("cargo:rustc-cfg=portable_atomic_no_atomic_64");
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} else {
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// Otherwise, assuming `"max-atomic-width" == 64` or `"max-atomic-width" == 128`.
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}
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}
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}
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// We don't need to use convert_custom_linux_target here because all linux targets have atomics.
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if NO_ATOMIC.contains(&target) {
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println!("cargo:rustc-cfg=portable_atomic_no_atomic_load_store");
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}
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if version.llvm >= 16 {
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println!("cargo:rustc-cfg=portable_atomic_llvm_16");
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}
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if version.nightly {
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// `cfg(sanitize = "..")` is not stabilized.
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let sanitize = env::var("CARGO_CFG_SANITIZE").unwrap_or_default();
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if sanitize.contains("thread") {
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// Most kinds of sanitizers are not compatible with asm
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// (https://github.com/google/sanitizers/issues/192),
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// but it seems that ThreadSanitizer is the only one that can cause
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// false positives in our code.
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println!("cargo:rustc-cfg=portable_atomic_sanitize_thread");
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}
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// https://github.com/rust-lang/rust/pull/93868 merged in Rust 1.60 (nightly-2022-02-13).
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// https://github.com/rust-lang/rust/pull/111331 merged in Rust 1.71 (nightly-2023-05-09).
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if !no_asm
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&& (target_arch == "powerpc64" && version.probe(60, 2022, 2, 12)
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|| target_arch == "s390x" && version.probe(71, 2023, 5, 8))
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&& is_allowed_feature("asm_experimental_arch")
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{
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println!("cargo:rustc-cfg=portable_atomic_unstable_asm_experimental_arch");
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}
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}
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let is_macos = target_os == "macos";
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let is_apple = is_macos || target_os == "ios" || target_os == "tvos" || target_os == "watchos";
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match target_arch {
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"x86_64" => {
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// cmpxchg16b_target_feature stabilized in Rust 1.69 (nightly-2023-03-01): https://github.com/rust-lang/rust/pull/106774
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if !version.probe(69, 2023, 2, 28) {
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if version.nightly && is_allowed_feature("cmpxchg16b_target_feature") {
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// This feature has not been changed since 1.33
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// (https://github.com/rust-lang/rust/commit/fbb56bcf44d28e65a9495decf091b6d0386e540c)
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// until it was stabilized in nightly-2023-03-01, so it can be safely enabled in
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// nightly, which is older than nightly-2023-03-01.
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println!("cargo:rustc-cfg=portable_atomic_unstable_cmpxchg16b_target_feature");
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} else {
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println!("cargo:rustc-cfg=portable_atomic_no_cmpxchg16b_target_feature");
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}
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}
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// For Miri and ThreadSanitizer.
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// https://github.com/rust-lang/rust/pull/109359 (includes https://github.com/rust-lang/stdarch/pull/1358) merged in Rust 1.70 (nightly-2023-03-24).
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if version.nightly && !version.probe(70, 2023, 3, 23) {
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println!("cargo:rustc-cfg=portable_atomic_unstable_cmpxchg16b_intrinsic");
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}
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// x86_64 Apple targets always support CMPXCHG16B:
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// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_target/src/spec/x86_64_apple_darwin.rs#L8
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// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_target/src/spec/apple_base.rs#L69-L70
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// Script to get targets that support cmpxchg16b by default:
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// $ (for target in $(rustc --print target-list); do [[ "${target}" == "x86_64"* ]] && rustc --print cfg --target "${target}" | grep -q cmpxchg16b && echo "${target}"; done)
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let has_cmpxchg16b = is_apple;
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// LLVM recognizes this also as cx16 target feature: https://godbolt.org/z/r8zWGcMhd
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// However, it is unlikely that rustc will support that name, so we ignore it.
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// cmpxchg16b_target_feature stabilized in Rust 1.69.
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target_feature_if("cmpxchg16b", has_cmpxchg16b, &version, Stable(69));
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}
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"aarch64" => {
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// For Miri and ThreadSanitizer.
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// https://github.com/rust-lang/rust/pull/97423 merged in Rust 1.64 (nightly-2022-06-30).
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if version.nightly && version.probe(64, 2022, 6, 29) {
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println!("cargo:rustc-cfg=portable_atomic_new_atomic_intrinsics");
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}
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// aarch64 macOS always supports FEAT_LSE and FEAT_LSE2 because it is armv8.5-a:
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// https://github.com/llvm/llvm-project/blob/llvmorg-17.0.0-rc2/llvm/include/llvm/TargetParser/AArch64TargetParser.h#L494
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let mut has_lse = is_macos;
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// FEAT_LSE2 doesn't imply FEAT_LSE. FEAT_LSE128 implies FEAT_LSE but not FEAT_LSE2.
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// As of rustc 1.70, target_feature "lse2"/"lse128"/"rcpc3" is not available on rustc side:
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// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_codegen_ssa/src/target_features.rs#L58
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target_feature_if("lse2", is_macos, &version, Unavailable);
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// LLVM supports FEAT_LRCPC3 and FEAT_LSE128 on LLVM 16+:
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// https://github.com/llvm/llvm-project/commit/a6aaa969f7caec58a994142f8d855861cf3a1463
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// https://github.com/llvm/llvm-project/commit/7fea6f2e0e606e5339c3359568f680eaf64aa306
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has_lse |= target_feature_if("lse128", false, &version, Unavailable);
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target_feature_if("rcpc3", false, &version, Unavailable);
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// aarch64_target_feature stabilized in Rust 1.61.
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target_feature_if("lse", has_lse, &version, Stable(61));
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// As of Apple M1/M1 Pro, on Apple hardware, CAS loop-based RMW is much slower than LL/SC
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// loop-based RMW: https://github.com/taiki-e/portable-atomic/pull/89
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if is_apple || target_cpu().map_or(false, |cpu| cpu.starts_with("apple-")) {
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println!("cargo:rustc-cfg=portable_atomic_ll_sc_rmw");
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}
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}
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"arm" => {
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// For non-Linux/Android pre-v6 ARM (tier 3) with unsafe_assume_single_core enabled.
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// feature(isa_attribute) stabilized in Rust 1.67 (nightly-2022-11-06): https://github.com/rust-lang/rust/pull/102458
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if version.nightly && !version.probe(67, 2022, 11, 5) {
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println!("cargo:rustc-cfg=portable_atomic_unstable_isa_attribute");
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}
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// #[cfg(target_feature = "v7")] and others don't work on stable.
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// armv7-unknown-linux-gnueabihf
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// ^^
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let mut subarch =
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strip_prefix(target, "arm").or_else(|| strip_prefix(target, "thumb")).unwrap();
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subarch = strip_prefix(subarch, "eb").unwrap_or(subarch); // ignore endianness
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subarch = subarch.split('-').next().unwrap(); // ignore vender/os/env
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subarch = subarch.split('.').next().unwrap(); // ignore .base/.main suffix
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let mut known = true;
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// See https://github.com/taiki-e/atomic-maybe-uninit/blob/HEAD/build.rs for details
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let mut is_mclass = false;
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match subarch {
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"v7" | "v7a" | "v7neon" | "v7s" | "v7k" | "v8a" | "v9a" => {} // aclass
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"v6m" | "v7em" | "v7m" | "v8m" => is_mclass = true,
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"v7r" | "v8r" => {} // rclass
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// arm-linux-androideabi is v5te
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// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_target/src/spec/arm_linux_androideabi.rs#L11-L12
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_ if target == "arm-linux-androideabi" => subarch = "v5te",
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// armeb-unknown-linux-gnueabi is v8 & aclass
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// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_target/src/spec/armeb_unknown_linux_gnueabi.rs#L12
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_ if target == "armeb-unknown-linux-gnueabi" => subarch = "v8",
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// v6 targets other than v6m don't have *class target feature.
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"" | "v6" | "v6k" => subarch = "v6",
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// Other targets don't have *class target feature.
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"v4t" | "v5te" => {}
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_ => {
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known = false;
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println!(
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"cargo:warning={}: unrecognized arm subarch: {}",
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env!("CARGO_PKG_NAME"),
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target
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);
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}
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}
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target_feature_if("mclass", is_mclass, &version, Nightly);
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let v6 = known
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&& (subarch.starts_with("v6")
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|| subarch.starts_with("v7")
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|| subarch.starts_with("v8")
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|| subarch.starts_with("v9"));
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target_feature_if("v6", v6, &version, Nightly);
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}
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"powerpc64" => {
|
||
|
|
// For Miri and ThreadSanitizer.
|
||
|
|
if version.nightly && version.llvm >= 15 {
|
||
|
|
println!("cargo:rustc-cfg=portable_atomic_llvm_15");
|
||
|
|
}
|
||
|
|
|
||
|
|
let target_endian =
|
||
|
|
env::var("CARGO_CFG_TARGET_ENDIAN").expect("CARGO_CFG_TARGET_ENDIAN not set");
|
||
|
|
// powerpc64le is pwr8+ by default
|
||
|
|
// https://github.com/llvm/llvm-project/blob/llvmorg-17.0.0-rc2/llvm/lib/Target/PowerPC/PPC.td#L663
|
||
|
|
// See also https://github.com/rust-lang/rust/issues/59932
|
||
|
|
let mut has_pwr8_features = target_endian == "little";
|
||
|
|
// https://github.com/llvm/llvm-project/commit/549e118e93c666914a1045fde38a2cac33e1e445
|
||
|
|
if let Some(cpu) = &target_cpu() {
|
||
|
|
if let Some(mut cpu_version) = strip_prefix(cpu, "pwr") {
|
||
|
|
cpu_version = strip_suffix(cpu_version, "x").unwrap_or(cpu_version); // for pwr5x and pwr6x
|
||
|
|
if let Ok(cpu_version) = cpu_version.parse::<u32>() {
|
||
|
|
has_pwr8_features = cpu_version >= 8;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
// https://github.com/llvm/llvm-project/blob/llvmorg-17.0.0-rc2/llvm/lib/Target/PowerPC/PPC.td#L663
|
||
|
|
// https://github.com/llvm/llvm-project/blob/llvmorg-17.0.0-rc2/llvm/lib/Target/PowerPC/PPC.td#L445-L447
|
||
|
|
has_pwr8_features = cpu == "ppc64le" || cpu == "future";
|
||
|
|
}
|
||
|
|
}
|
||
|
|
// Note: As of rustc 1.70, target_feature "quadword-atomics" is not available on rustc side:
|
||
|
|
// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_codegen_ssa/src/target_features.rs#L226
|
||
|
|
// lqarx and stqcx.
|
||
|
|
target_feature_if("quadword-atomics", has_pwr8_features, &version, Unavailable);
|
||
|
|
}
|
||
|
|
"s390x" => {
|
||
|
|
// https://github.com/llvm/llvm-project/blob/llvmorg-17.0.0-rc2/llvm/lib/Target/SystemZ/SystemZFeatures.td
|
||
|
|
let mut arch9_features = false; // z196+
|
||
|
|
let mut arch13_features = false; // z15+
|
||
|
|
if let Some(cpu) = target_cpu() {
|
||
|
|
// https://github.com/llvm/llvm-project/blob/llvmorg-17.0.0-rc2/llvm/lib/Target/SystemZ/SystemZProcessors.td
|
||
|
|
match &*cpu {
|
||
|
|
"arch9" | "z196" | "arch10" | "zEC12" | "arch11" | "z13" | "arch12" | "z14" => {
|
||
|
|
arch9_features = true;
|
||
|
|
}
|
||
|
|
"arch13" | "z15" | "arch14" | "z16" => {
|
||
|
|
arch9_features = true;
|
||
|
|
arch13_features = true;
|
||
|
|
}
|
||
|
|
_ => {}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
// Note: As of rustc 1.70, target_feature "fast-serialization"/"load-store-on-cond"/"distinct-ops"/"miscellaneous-extensions-3" is not available on rustc side:
|
||
|
|
// https://github.com/rust-lang/rust/blob/1.70.0/compiler/rustc_codegen_ssa/src/target_features.rs
|
||
|
|
// bcr 14,0
|
||
|
|
target_feature_if("fast-serialization", arch9_features, &version, Unavailable);
|
||
|
|
// {l,st}oc{,g}{,r}
|
||
|
|
target_feature_if("load-store-on-cond", arch9_features, &version, Unavailable);
|
||
|
|
// {al,sl,n,o,x}{,g}rk
|
||
|
|
target_feature_if("distinct-ops", arch9_features, &version, Unavailable);
|
||
|
|
// nand (nnr{,g}k), select (sel{,g}r), etc.
|
||
|
|
target_feature_if("miscellaneous-extensions-3", arch13_features, &version, Unavailable);
|
||
|
|
}
|
||
|
|
_ => {}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
enum Availability {
|
||
|
|
Stable(u32),
|
||
|
|
Nightly,
|
||
|
|
Unavailable,
|
||
|
|
}
|
||
|
|
use Availability::{Nightly, Stable, Unavailable};
|
||
|
|
|
||
|
|
fn target_feature_if(
|
||
|
|
name: &str,
|
||
|
|
mut has_target_feature: bool,
|
||
|
|
version: &Version,
|
||
|
|
availability: Availability,
|
||
|
|
) -> bool {
|
||
|
|
// 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
|
||
|
|
match availability {
|
||
|
|
// In these cases, cfg(target_feature = "...") would work, so skip emitting our own target_feature cfg.
|
||
|
|
Availability::Stable(stabilized) if version.nightly || version.minor >= stabilized => {
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
Availability::Nightly if version.nightly => return false,
|
||
|
|
_ => {}
|
||
|
|
}
|
||
|
|
if let Some(rustflags) = env::var_os("CARGO_ENCODED_RUSTFLAGS") {
|
||
|
|
for mut flag in rustflags.to_string_lossy().split('\x1f') {
|
||
|
|
flag = strip_prefix(flag, "-C").unwrap_or(flag);
|
||
|
|
if let Some(flag) = strip_prefix(flag, "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=portable_atomic_target_feature=\"{}\"", name);
|
||
|
|
}
|
||
|
|
has_target_feature
|
||
|
|
}
|
||
|
|
|
||
|
|
fn target_cpu() -> Option<String> {
|
||
|
|
let rustflags = env::var_os("CARGO_ENCODED_RUSTFLAGS")?;
|
||
|
|
let rustflags = rustflags.to_string_lossy();
|
||
|
|
let mut cpu = None;
|
||
|
|
for mut flag in rustflags.split('\x1f') {
|
||
|
|
flag = strip_prefix(flag, "-C").unwrap_or(flag);
|
||
|
|
if let Some(flag) = strip_prefix(flag, "target-cpu=") {
|
||
|
|
cpu = Some(flag);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
cpu.map(str::to_owned)
|
||
|
|
}
|
||
|
|
|
||
|
|
fn is_allowed_feature(name: &str) -> bool {
|
||
|
|
// allowed by default
|
||
|
|
let mut allowed = true;
|
||
|
|
if let Some(rustflags) = env::var_os("CARGO_ENCODED_RUSTFLAGS") {
|
||
|
|
for mut flag in rustflags.to_string_lossy().split('\x1f') {
|
||
|
|
flag = strip_prefix(flag, "-Z").unwrap_or(flag);
|
||
|
|
if let Some(flag) = strip_prefix(flag, "allow-features=") {
|
||
|
|
// If it is specified multiple times, the last value will be preferred.
|
||
|
|
allowed = flag.split(',').any(|allowed| allowed == name);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
allowed
|
||
|
|
}
|
||
|
|
|
||
|
|
// Adapted from https://github.com/crossbeam-rs/crossbeam/blob/crossbeam-utils-0.8.14/build-common.rs.
|
||
|
|
//
|
||
|
|
// The target triplets have the form of 'arch-vendor-system'.
|
||
|
|
//
|
||
|
|
// When building for Linux (e.g. the 'system' part is
|
||
|
|
// 'linux-something'), replace the vendor with 'unknown'
|
||
|
|
// so that mapping to rust standard targets happens correctly.
|
||
|
|
fn convert_custom_linux_target(target: &str) -> String {
|
||
|
|
let mut parts: Vec<&str> = target.split('-').collect();
|
||
|
|
let system = parts.get(2);
|
||
|
|
if system == Some(&"linux") {
|
||
|
|
parts[1] = "unknown";
|
||
|
|
}
|
||
|
|
parts.join("-")
|
||
|
|
}
|
||
|
|
|
||
|
|
// str::strip_prefix requires Rust 1.45
|
||
|
|
#[must_use]
|
||
|
|
fn strip_prefix<'a>(s: &'a str, pat: &str) -> Option<&'a str> {
|
||
|
|
if s.starts_with(pat) {
|
||
|
|
Some(&s[pat.len()..])
|
||
|
|
} else {
|
||
|
|
None
|
||
|
|
}
|
||
|
|
}
|
||
|
|
// str::strip_suffix requires Rust 1.45
|
||
|
|
#[must_use]
|
||
|
|
fn strip_suffix<'a>(s: &'a str, pat: &str) -> Option<&'a str> {
|
||
|
|
if s.ends_with(pat) {
|
||
|
|
Some(&s[..s.len() - pat.len()])
|
||
|
|
} else {
|
||
|
|
None
|
||
|
|
}
|
||
|
|
}
|