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
10 use crate::builder::{Builder, ShouldRun, Step};
11 use crate::config::TargetSelection;
12 use crate::Compiler;
13 use std::process::{Command, Stdio};
14
15 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
16 pub(crate) struct MirOptPanicAbortSyntheticTarget {
17 pub(crate) compiler: Compiler,
18 pub(crate) base: TargetSelection,
19 }
20
21 impl Step for MirOptPanicAbortSyntheticTarget {
22 type Output = TargetSelection;
23 const DEFAULT: bool = true;
24 const ONLY_HOSTS: bool = false;
25
should_run(run: ShouldRun<'_>) -> ShouldRun<'_>26 fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
27 run.never()
28 }
29
run(self, builder: &Builder<'_>) -> Self::Output30 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
create_synthetic_target( builder: &Builder<'_>, compiler: Compiler, suffix: &str, base: TargetSelection, customize: impl FnOnce(&mut serde_json::Map<String, serde_json::Value>), ) -> TargetSelection37 fn 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::new(builder.rustc(compiler));
60 cmd.arg("--target").arg(base.rustc_target_arg());
61 cmd.args(["-Zunstable-options", "--print", "target-spec-json"]);
62 cmd.stdout(Stdio::piped());
63
64 let output = cmd.spawn().unwrap().wait_with_output().unwrap();
65 if !output.status.success() {
66 panic!("failed to gather the target spec for {base}");
67 }
68
69 let mut spec: serde_json::Value = serde_json::from_slice(&output.stdout).unwrap();
70 let spec_map = spec.as_object_mut().unwrap();
71
72 // The `is-builtin` attribute of a spec needs to be removed, otherwise rustc will complain.
73 spec_map.remove("is-builtin");
74
75 customize(spec_map);
76
77 std::fs::write(&path, &serde_json::to_vec_pretty(&spec).unwrap()).unwrap();
78 let target = TargetSelection::create_synthetic(&name, path.to_str().unwrap());
79 crate::cc_detect::find_target(builder, target);
80
81 target
82 }
83