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use std::env;
use std::process::Command;
use std::str::{self, FromStr};
// The rustc-cfg strings below are *not* public API. Please let us know by
// opening a GitHub issue if your build environment requires some way to enable
// these cfgs other than by executing our build script.
fn main() {
println!("cargo:rerun-if-changed=build.rs");
let minor = match rustc_minor_version() {
Some(minor) => minor,
None => return,
};
let target = env::var("TARGET").unwrap();
let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
// TryFrom, Atomic types, non-zero signed integers, and SystemTime::checked_add
// stabilized in Rust 1.34:
if minor < 34 {
println!("cargo:rustc-cfg=no_core_try_from");
println!("cargo:rustc-cfg=no_num_nonzero_signed");
println!("cargo:rustc-cfg=no_systemtime_checked_add");
println!("cargo:rustc-cfg=no_relaxed_trait_bounds");
}
// f32::copysign and f64::copysign stabilized in Rust 1.35.
if minor < 35 {
println!("cargo:rustc-cfg=no_float_copysign");
}
// Current minimum supported version of serde_derive crate is Rust 1.56.
if minor < 56 {
println!("cargo:rustc-cfg=no_serde_derive");
}
// Support for #[cfg(target_has_atomic = "...")] stabilized in Rust 1.60.
if minor < 60 {
println!("cargo:rustc-cfg=no_target_has_atomic");
// Allowlist of archs that support std::sync::atomic module. This is
// based on rustc's compiler/rustc_target/src/spec/*.rs.
let has_atomic64 = target.starts_with("x86_64")
|| target.starts_with("i686")
|| target.starts_with("aarch64")
|| target.starts_with("powerpc64")
|| target.starts_with("sparc64")
|| target.starts_with("mips64el")
|| target.starts_with("riscv64");
let has_atomic32 = has_atomic64 || emscripten;
if minor < 34 || !has_atomic64 {
println!("cargo:rustc-cfg=no_std_atomic64");
}
if minor < 34 || !has_atomic32 {
println!("cargo:rustc-cfg=no_std_atomic");
}
}
// Support for core::ffi::CStr and alloc::ffi::CString stabilized in Rust 1.64.
if minor < 64 {
println!("cargo:rustc-cfg=no_core_cstr");
}
// Support for core::num::Saturating and std::num::Saturating stabilized in Rust 1.74
if minor < 74 {
println!("cargo:rustc-cfg=no_core_num_saturating");
}
}
fn rustc_minor_version() -> Option<u32> {
let rustc = match env::var_os("RUSTC") {
Some(rustc) => rustc,
None => return None,
};
let output = match Command::new(rustc).arg("--version").output() {
Ok(output) => output,
Err(_) => return None,
};
let version = match str::from_utf8(&output.stdout) {
Ok(version) => version,
Err(_) => return None,
};
let mut pieces = version.split('.');
if pieces.next() != Some("rustc 1") {
return None;
}
let next = match pieces.next() {
Some(next) => next,
None => return None,
};
u32::from_str(next).ok()
}