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//! Runs `rustc --print target-spec-json` to get the target_data_layout.
use std::process::Command;
use anyhow::Result;
use rustc_hash::FxHashMap;
use crate::{utf8_stdout, ManifestPath};
pub fn get(
cargo_toml: Option<&ManifestPath>,
target: Option<&str>,
extra_env: &FxHashMap<String, String>,
) -> Result<String> {
let output = (|| {
if let Some(cargo_toml) = cargo_toml {
let mut cmd = Command::new(toolchain::rustc());
cmd.envs(extra_env);
cmd.current_dir(cargo_toml.parent())
.args(["-Z", "unstable-options", "rustc", "--print", "target-spec-json"])
.env("RUSTC_BOOTSTRAP", "1");
if let Some(target) = target {
cmd.args(["--target", target]);
}
match utf8_stdout(cmd) {
Ok(it) => return Ok(it),
Err(e) => tracing::debug!("{e:?}: falling back to querying rustc for cfgs"),
}
}
// using unstable cargo features failed, fall back to using plain rustc
let mut cmd = Command::new(toolchain::rustc());
cmd.envs(extra_env)
.args(["-Z", "unstable-options", "--print", "target-spec-json"])
.env("RUSTC_BOOTSTRAP", "1");
if let Some(target) = target {
cmd.args(["--target", target]);
}
utf8_stdout(cmd)
})()?;
(|| Some(output.split_once(r#""data-layout": ""#)?.1.split_once('"')?.0.to_owned()))()
.ok_or_else(|| anyhow::format_err!("could not fetch target-spec-json from command output"))
}
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