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use std::env;
use std::ffi::OsString;
use std::iter;
use std::path::Path;
use std::process::{self, Command, Stdio};
fn main() {
println!("cargo:rerun-if-changed=build/probe.rs");
let error_generic_member_access;
let consider_rustc_bootstrap;
if compile_probe(false) {
// This is a nightly or dev compiler, so it supports unstable features
// regardless of RUSTC_BOOTSTRAP. No need to rerun build script if
// RUSTC_BOOTSTRAP is changed.
error_generic_member_access = true;
consider_rustc_bootstrap = false;
} else if let Some(rustc_bootstrap) = env::var_os("RUSTC_BOOTSTRAP") {
if compile_probe(true) {
// This is a stable or beta compiler for which the user has set
// RUSTC_BOOTSTRAP to turn on unstable features. Rerun build script
// if they change it.
error_generic_member_access = true;
consider_rustc_bootstrap = true;
} else if rustc_bootstrap == "1" {
// This compiler does not support the generic member access API in
// the form that thiserror expects. No need to pay attention to
// RUSTC_BOOTSTRAP.
error_generic_member_access = false;
consider_rustc_bootstrap = false;
} else {
// This is a stable or beta compiler for which RUSTC_BOOTSTRAP is
// set to restrict the use of unstable features by this crate.
error_generic_member_access = false;
consider_rustc_bootstrap = true;
}
} else {
// Without RUSTC_BOOTSTRAP, this compiler does not support the generic
// member access API in the form that thiserror expects, but try again
// if the user turns on unstable features.
error_generic_member_access = false;
consider_rustc_bootstrap = true;
}
if error_generic_member_access {
println!("cargo:rustc-cfg=error_generic_member_access");
}
if consider_rustc_bootstrap {
println!("cargo:rerun-if-env-changed=RUSTC_BOOTSTRAP");
}
}
fn compile_probe(rustc_bootstrap: bool) -> bool {
if env::var_os("RUSTC_STAGE").is_some() {
// We are running inside rustc bootstrap. This is a highly non-standard
// environment with issues such as:
//
//
// Let's just not use nightly features here.
return false;
}
let rustc = cargo_env_var("RUSTC");
let out_dir = cargo_env_var("OUT_DIR");
let probefile = Path::new("build").join("probe.rs");
let rustc_wrapper = env::var_os("RUSTC_WRAPPER").filter(|wrapper| !wrapper.is_empty());
let rustc_workspace_wrapper =
env::var_os("RUSTC_WORKSPACE_WRAPPER").filter(|wrapper| !wrapper.is_empty());
let mut rustc = rustc_wrapper
.into_iter()
.chain(rustc_workspace_wrapper)
.chain(iter::once(rustc));
let mut cmd = Command::new(rustc.next().unwrap());
cmd.args(rustc);
if !rustc_bootstrap {
cmd.env_remove("RUSTC_BOOTSTRAP");
}
cmd.stderr(Stdio::null())
.arg("--edition=2018")
.arg("--crate-name=thiserror")
.arg("--crate-type=lib")
.arg("--cap-lints=allow")
.arg("--emit=dep-info,metadata")
.arg("--out-dir")
.arg(out_dir)
.arg(probefile);
if let Some(target) = env::var_os("TARGET") {
cmd.arg("--target").arg(target);
}
// If Cargo wants to set RUSTFLAGS, use that.
if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
if !rustflags.is_empty() {
for arg in rustflags.split('\x1f') {
cmd.arg(arg);
}
}
}
match cmd.status() {
Ok(status) => status.success(),
Err(_) => false,
}
}
fn cargo_env_var(key: &str) -> OsString {
env::var_os(key).unwrap_or_else(|| {
eprintln!(
"Environment variable ${} is not set during execution of build script",
key,
);
process::exit(1);
})
}