bootstrap/core/build_steps/
synthetic_targets.rs

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1//! In some cases, parts of bootstrap need to change part of a target spec just for one or a few
2//! steps. Adding these targets to rustc proper would "leak" this implementation detail of
3//! bootstrap, and would make it more complex to apply additional changes if the need arises.
4//!
5//! To address that problem, this module implements support for "synthetic targets". Synthetic
6//! targets are custom target specs generated using builtin target specs as their base. You can use
7//! one of the target specs already defined in this module, or create new ones by adding a new step
8//! that calls create_synthetic_target.
9
10use crate::Compiler;
11use crate::core::builder::{Builder, ShouldRun, Step};
12use crate::core::config::TargetSelection;
13use crate::utils::exec::command;
14
15#[derive(Debug, Clone, PartialEq, Eq, Hash)]
16pub(crate) struct MirOptPanicAbortSyntheticTarget {
17    pub(crate) compiler: Compiler,
18    pub(crate) base: TargetSelection,
19}
20
21impl Step for MirOptPanicAbortSyntheticTarget {
22    type Output = TargetSelection;
23    const DEFAULT: bool = true;
24    const ONLY_HOSTS: bool = false;
25
26    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
27        run.never()
28    }
29
30    fn run(self, builder: &Builder<'_>) -> Self::Output {
31        create_synthetic_target(builder, self.compiler, "miropt-abort", self.base, |spec| {
32            spec.insert("panic-strategy".into(), "abort".into());
33        })
34    }
35}
36
37fn create_synthetic_target(
38    builder: &Builder<'_>,
39    compiler: Compiler,
40    suffix: &str,
41    base: TargetSelection,
42    customize: impl FnOnce(&mut serde_json::Map<String, serde_json::Value>),
43) -> TargetSelection {
44    if base.contains("synthetic") {
45        // This check is not strictly needed, but nothing currently needs recursive synthetic
46        // targets. If the need arises, removing this in the future *SHOULD* be safe.
47        panic!("cannot create synthetic targets with other synthetic targets as their base");
48    }
49
50    let name = format!("{base}-synthetic-{suffix}");
51    let path = builder.out.join("synthetic-target-specs").join(format!("{name}.json"));
52    std::fs::create_dir_all(path.parent().unwrap()).unwrap();
53
54    if builder.config.dry_run() {
55        std::fs::write(&path, b"dry run\n").unwrap();
56        return TargetSelection::create_synthetic(&name, path.to_str().unwrap());
57    }
58
59    let mut cmd = command(builder.rustc(compiler));
60    cmd.arg("--target").arg(base.rustc_target_arg());
61    cmd.args(["-Zunstable-options", "--print", "target-spec-json"]);
62
63    // If `rust.channel` is set to either beta or stable, rustc will complain that
64    // we cannot use nightly features. So `RUSTC_BOOTSTRAP` is needed here.
65    cmd.env("RUSTC_BOOTSTRAP", "1");
66
67    let output = cmd.run_capture(builder).stdout();
68    let mut spec: serde_json::Value = serde_json::from_slice(output.as_bytes()).unwrap();
69    let spec_map = spec.as_object_mut().unwrap();
70
71    // The `is-builtin` attribute of a spec needs to be removed, otherwise rustc will complain.
72    spec_map.remove("is-builtin");
73
74    customize(spec_map);
75
76    std::fs::write(&path, serde_json::to_vec_pretty(&spec).unwrap()).unwrap();
77    TargetSelection::create_synthetic(&name, path.to_str().unwrap())
78}
bootstrap/core/build_steps/synthetic_targets.rs

bootstrap/core/build_steps/
synthetic_targets.rs
