bootstrap/core/build_steps/
synthetic_targets.rs

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
25    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
26        run.never()
27    }
28
29    fn run(self, builder: &Builder<'_>) -> Self::Output {
30        create_synthetic_target(builder, self.compiler, "miropt-abort", self.base, |spec| {
31            spec.insert("panic-strategy".into(), "abort".into());
32        })
33    }
34}
35
36fn create_synthetic_target(
37    builder: &Builder<'_>,
38    compiler: Compiler,
39    suffix: &str,
40    base: TargetSelection,
41    customize: impl FnOnce(&mut serde_json::Map<String, serde_json::Value>),
42) -> TargetSelection {
43    if base.contains("synthetic") {
44        // This check is not strictly needed, but nothing currently needs recursive synthetic
45        // targets. If the need arises, removing this in the future *SHOULD* be safe.
46        panic!("cannot create synthetic targets with other synthetic targets as their base");
47    }
48
49    let name = format!("{base}-synthetic-{suffix}");
50    let path = builder.out.join("synthetic-target-specs").join(format!("{name}.json"));
51    std::fs::create_dir_all(path.parent().unwrap()).unwrap();
52
53    if builder.config.dry_run() {
54        std::fs::write(&path, b"dry run\n").unwrap();
55        return TargetSelection::create_synthetic(&name, path.to_str().unwrap());
56    }
57
58    let mut cmd = command(builder.rustc(compiler));
59    cmd.arg("--target").arg(base.rustc_target_arg());
60    cmd.args(["-Zunstable-options", "--print", "target-spec-json"]);
61
62    // If `rust.channel` is set to either beta or stable, rustc will complain that
63    // we cannot use nightly features. So `RUSTC_BOOTSTRAP` is needed here.
64    cmd.env("RUSTC_BOOTSTRAP", "1");
65
66    let output = cmd.run_capture(builder).stdout();
67    let mut spec: serde_json::Value = serde_json::from_slice(output.as_bytes()).unwrap();
68    let spec_map = spec.as_object_mut().unwrap();
69
70    // The `is-builtin` attribute of a spec needs to be removed, otherwise rustc will complain.
71    spec_map.remove("is-builtin");
72
73    customize(spec_map);
74
75    std::fs::write(&path, serde_json::to_vec_pretty(&spec).unwrap()).unwrap();
76    TargetSelection::create_synthetic(&name, path.to_str().unwrap())
77}
bootstrap/core/build_steps/synthetic_targets.rs

bootstrap/core/build_steps/
synthetic_targets.rs
