src/bootstrap/tool.rs

   1 use std::collections::HashSet;
   2 use std::env;
   3 use std::fs;
   4 use std::path::PathBuf;
   5 use std::process::{exit, Command};
   6
   7 use build_helper::t;
   8
   9 use crate::builder::{Builder, Cargo as CargoCommand, RunConfig, ShouldRun, Step};
  10 use crate::cache::Interned;
  11 use crate::channel;
  12 use crate::channel::GitInfo;
  13 use crate::compile;
  14 use crate::toolstate::ToolState;
  15 use crate::util::{add_lib_path, exe, CiEnv};
  16 use crate::Compiler;
  17 use crate::Mode;
  18
  19 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
  20 pub enum SourceType {
  21     InTree,
  22     Submodule,
  23 }
  24
  25 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
  26 struct ToolBuild {
  27     compiler: Compiler,
  28     target: Interned<String>,
  29     tool: &'static str,
  30     path: &'static str,
  31     mode: Mode,
  32     is_optional_tool: bool,
  33     source_type: SourceType,
  34     extra_features: Vec<String>,
  35 }
  36
  37 impl Step for ToolBuild {
  38     type Output = Option<PathBuf>;
  39
  40     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
  41         run.never()
  42     }
  43
  44     /// Builds a tool in `src/tools`
  45     ///
  46     /// This will build the specified tool with the specified `host` compiler in
  47     /// `stage` into the normal cargo output directory.
  48     fn run(self, builder: &Builder<'_>) -> Option<PathBuf> {
  49         let compiler = self.compiler;
  50         let target = self.target;
  51         let tool = self.tool;
  52         let path = self.path;
  53         let is_optional_tool = self.is_optional_tool;
  54
  55         match self.mode {
  56             Mode::ToolRustc => builder.ensure(compile::Rustc { compiler, target }),
  57             Mode::ToolStd => builder.ensure(compile::Std { compiler, target }),
  58             Mode::ToolBootstrap => {} // uses downloaded stage0 compiler libs
  59             _ => panic!("unexpected Mode for tool build"),
  60         }
  61
  62         let cargo = prepare_tool_cargo(
  63             builder,
  64             compiler,
  65             self.mode,
  66             target,
  67             "build",
  68             path,
  69             self.source_type,
  70             &self.extra_features,
  71         );
  72
  73         builder.info(&format!("Building stage{} tool {} ({})", compiler.stage, tool, target));
  74         let mut duplicates = Vec::new();
  75         let is_expected = compile::stream_cargo(builder, cargo, vec![], &mut |msg| {
  76             // Only care about big things like the RLS/Cargo for now
  77             match tool {
  78                 "rls" | "cargo" | "clippy-driver" | "miri" | "rustfmt" => {}
  79
  80                 _ => return,
  81             }
  82             let (id, features, filenames) = match msg {
  83                 compile::CargoMessage::CompilerArtifact {
  84                     package_id,
  85                     features,
  86                     filenames,
  87                     target: _,
  88                 } => (package_id, features, filenames),
  89                 _ => return,
  90             };
  91             let features = features.iter().map(|s| s.to_string()).collect::<Vec<_>>();
  92
  93             for path in filenames {
  94                 let val = (tool, PathBuf::from(&*path), features.clone());
  95                 // we're only interested in deduplicating rlibs for now
  96                 if val.1.extension().and_then(|s| s.to_str()) != Some("rlib") {
  97                     continue;
  98                 }
  99
 100                 // Don't worry about compiles that turn out to be host
 101                 // dependencies or build scripts. To skip these we look for
 102                 // anything that goes in `.../release/deps` but *doesn't* go in
 103                 // `$target/release/deps`. This ensure that outputs in
 104                 // `$target/release` are still considered candidates for
 105                 // deduplication.
 106                 if let Some(parent) = val.1.parent() {
 107                     if parent.ends_with("release/deps") {
 108                         let maybe_target = parent
 109                             .parent()
 110                             .and_then(|p| p.parent())
 111                             .and_then(|p| p.file_name())
 112                             .and_then(|p| p.to_str())
 113                             .unwrap();
 114                         if maybe_target != &*target {
 115                             continue;
 116                         }
 117                     }
 118                 }
 119
 120                 // Record that we've built an artifact for `id`, and if one was
 121                 // already listed then we need to see if we reused the same
 122                 // artifact or produced a duplicate.
 123                 let mut artifacts = builder.tool_artifacts.borrow_mut();
 124                 let prev_artifacts = artifacts.entry(target).or_default();
 125                 let prev = match prev_artifacts.get(&*id) {
 126                     Some(prev) => prev,
 127                     None => {
 128                         prev_artifacts.insert(id.to_string(), val);
 129                         continue;
 130                     }
 131                 };
 132                 if prev.1 == val.1 {
 133                     return; // same path, same artifact
 134                 }
 135
 136                 // If the paths are different and one of them *isn't* inside of
 137                 // `release/deps`, then it means it's probably in
 138                 // `$target/release`, or it's some final artifact like
 139                 // `libcargo.rlib`. In these situations Cargo probably just
 140                 // copied it up from `$target/release/deps/libcargo-xxxx.rlib`,
 141                 // so if the features are equal we can just skip it.
 142                 let prev_no_hash = prev.1.parent().unwrap().ends_with("release/deps");
 143                 let val_no_hash = val.1.parent().unwrap().ends_with("release/deps");
 144                 if prev.2 == val.2 || !prev_no_hash || !val_no_hash {
 145                     return;
 146                 }
 147
 148                 // ... and otherwise this looks like we duplicated some sort of
 149                 // compilation, so record it to generate an error later.
 150                 duplicates.push((id.to_string(), val, prev.clone()));
 151             }
 152         });
 153
 154         if is_expected && !duplicates.is_empty() {
 155             println!(
 156                 "duplicate artifacts found when compiling a tool, this \
 157                       typically means that something was recompiled because \
 158                       a transitive dependency has different features activated \
 159                       than in a previous build:\n"
 160             );
 161             println!(
 162                 "the following dependencies are duplicated although they \
 163                       have the same features enabled:"
 164             );
 165             for (id, cur, prev) in duplicates.drain_filter(|(_, cur, prev)| cur.2 == prev.2) {
 166                 println!("  {}", id);
 167                 // same features
 168                 println!("    `{}` ({:?})\n    `{}` ({:?})", cur.0, cur.1, prev.0, prev.1);
 169             }
 170             println!("the following dependencies have different features:");
 171             for (id, cur, prev) in duplicates {
 172                 println!("  {}", id);
 173                 let cur_features: HashSet<_> = cur.2.into_iter().collect();
 174                 let prev_features: HashSet<_> = prev.2.into_iter().collect();
 175                 println!(
 176                     "    `{}` additionally enabled features {:?} at {:?}",
 177                     cur.0,
 178                     &cur_features - &prev_features,
 179                     cur.1
 180                 );
 181                 println!(
 182                     "    `{}` additionally enabled features {:?} at {:?}",
 183                     prev.0,
 184                     &prev_features - &cur_features,
 185                     prev.1
 186                 );
 187             }
 188             println!();
 189             println!(
 190                 "to fix this you will probably want to edit the local \
 191                       src/tools/rustc-workspace-hack/Cargo.toml crate, as \
 192                       that will update the dependency graph to ensure that \
 193                       these crates all share the same feature set"
 194             );
 195             panic!("tools should not compile multiple copies of the same crate");
 196         }
 197
 198         builder.save_toolstate(
 199             tool,
 200             if is_expected { ToolState::TestFail } else { ToolState::BuildFail },
 201         );
 202
 203         if !is_expected {
 204             if !is_optional_tool {
 205                 exit(1);
 206             } else {
 207                 None
 208             }
 209         } else {
 210             let cargo_out =
 211                 builder.cargo_out(compiler, self.mode, target).join(exe(tool, &compiler.host));
 212             let bin = builder.tools_dir(compiler).join(exe(tool, &compiler.host));
 213             builder.copy(&cargo_out, &bin);
 214             Some(bin)
 215         }
 216     }
 217 }
 218
 219 pub fn prepare_tool_cargo(
 220     builder: &Builder<'_>,
 221     compiler: Compiler,
 222     mode: Mode,
 223     target: Interned<String>,
 224     command: &'static str,
 225     path: &'static str,
 226     source_type: SourceType,
 227     extra_features: &[String],
 228 ) -> CargoCommand {
 229     let mut cargo = builder.cargo(compiler, mode, target, command);
 230     let dir = builder.src.join(path);
 231     cargo.arg("--manifest-path").arg(dir.join("Cargo.toml"));
 232
 233     if source_type == SourceType::Submodule {
 234         cargo.env("RUSTC_EXTERNAL_TOOL", "1");
 235     }
 236
 237     let mut features = extra_features.iter().cloned().collect::<Vec<_>>();
 238     if builder.build.config.cargo_native_static {
 239         if path.ends_with("cargo")
 240             || path.ends_with("rls")
 241             || path.ends_with("clippy")
 242             || path.ends_with("miri")
 243             || path.ends_with("rustbook")
 244             || path.ends_with("rustfmt")
 245         {
 246             cargo.env("LIBZ_SYS_STATIC", "1");
 247             features.push("rustc-workspace-hack/all-static".to_string());
 248         }
 249     }
 250
 251     // if tools are using lzma we want to force the build script to build its
 252     // own copy
 253     cargo.env("LZMA_API_STATIC", "1");
 254
 255     cargo.env("CFG_RELEASE_CHANNEL", &builder.config.channel);
 256     cargo.env("CFG_VERSION", builder.rust_version());
 257     cargo.env("CFG_RELEASE_NUM", channel::CFG_RELEASE_NUM);
 258
 259     let info = GitInfo::new(builder.config.ignore_git, &dir);
 260     if let Some(sha) = info.sha() {
 261         cargo.env("CFG_COMMIT_HASH", sha);
 262     }
 263     if let Some(sha_short) = info.sha_short() {
 264         cargo.env("CFG_SHORT_COMMIT_HASH", sha_short);
 265     }
 266     if let Some(date) = info.commit_date() {
 267         cargo.env("CFG_COMMIT_DATE", date);
 268     }
 269     if !features.is_empty() {
 270         cargo.arg("--features").arg(&features.join(", "));
 271     }
 272     cargo
 273 }
 274
 275 fn rustbook_features() -> Vec<String> {
 276     let mut features = Vec::new();
 277
 278     // Due to CI budged and risk of spurious failures we want to limit jobs running this check.
 279     // At same time local builds should run it regardless of the platform.
 280     // `CiEnv::None` means it's local build and `CHECK_LINKS` is defined in x86_64-gnu-tools to
 281     // explicitly enable it on single job
 282     if CiEnv::current() == CiEnv::None || env::var("CHECK_LINKS").is_ok() {
 283         features.push("linkcheck".to_string());
 284     }
 285
 286     features
 287 }
 288
 289 macro_rules! bootstrap_tool {
 290     ($(
 291         $name:ident, $path:expr, $tool_name:expr
 292         $(,is_external_tool = $external:expr)*
 293         $(,is_unstable_tool = $unstable:expr)*
 294         $(,features = $features:expr)*
 295         ;
 296     )+) => {
 297         #[derive(Copy, PartialEq, Eq, Clone)]
 298         pub enum Tool {
 299             $(
 300                 $name,
 301             )+
 302         }
 303
 304         impl<'a> Builder<'a> {
 305             pub fn tool_exe(&self, tool: Tool) -> PathBuf {
 306                 match tool {
 307                     $(Tool::$name =>
 308                         self.ensure($name {
 309                             compiler: self.compiler(0, self.config.build),
 310                             target: self.config.build,
 311                         }),
 312                     )+
 313                 }
 314             }
 315         }
 316
 317         $(
 318             #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 319         pub struct $name {
 320             pub compiler: Compiler,
 321             pub target: Interned<String>,
 322         }
 323
 324         impl Step for $name {
 325             type Output = PathBuf;
 326
 327             fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 328                 run.path($path)
 329             }
 330
 331             fn make_run(run: RunConfig<'_>) {
 332                 run.builder.ensure($name {
 333                     // snapshot compiler
 334                     compiler: run.builder.compiler(0, run.builder.config.build),
 335                     target: run.target,
 336                 });
 337             }
 338
 339             fn run(self, builder: &Builder<'_>) -> PathBuf {
 340                 builder.ensure(ToolBuild {
 341                     compiler: self.compiler,
 342                     target: self.target,
 343                     tool: $tool_name,
 344                     mode: if false $(|| $unstable)* {
 345                         // use in-tree libraries for unstable features
 346                         Mode::ToolStd
 347                     } else {
 348                         Mode::ToolBootstrap
 349                     },
 350                     path: $path,
 351                     is_optional_tool: false,
 352                     source_type: if false $(|| $external)* {
 353                         SourceType::Submodule
 354                     } else {
 355                         SourceType::InTree
 356                     },
 357                     extra_features: {
 358                         // FIXME(#60643): avoid this lint by using `_`
 359                         let mut _tmp = Vec::new();
 360                         $(_tmp.extend($features);)*
 361                         _tmp
 362                     },
 363                 }).expect("expected to build -- essential tool")
 364             }
 365         }
 366         )+
 367     }
 368 }
 369
 370 bootstrap_tool!(
 371     Rustbook, "src/tools/rustbook", "rustbook", features = rustbook_features();
 372     UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen";
 373     Tidy, "src/tools/tidy", "tidy";
 374     Linkchecker, "src/tools/linkchecker", "linkchecker";
 375     CargoTest, "src/tools/cargotest", "cargotest";
 376     Compiletest, "src/tools/compiletest", "compiletest", is_unstable_tool = true;
 377     BuildManifest, "src/tools/build-manifest", "build-manifest";
 378     RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
 379     RustInstaller, "src/tools/rust-installer", "fabricate", is_external_tool = true;
 380     RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes";
 381 );
 382
 383 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 384 pub struct ErrorIndex {
 385     pub compiler: Compiler,
 386 }
 387
 388 impl ErrorIndex {
 389     pub fn command(builder: &Builder<'_>, compiler: Compiler) -> Command {
 390         let mut cmd = Command::new(builder.ensure(ErrorIndex { compiler }));
 391         add_lib_path(
 392             vec![PathBuf::from(&builder.sysroot_libdir(compiler, compiler.host))],
 393             &mut cmd,
 394         );
 395         cmd
 396     }
 397 }
 398
 399 impl Step for ErrorIndex {
 400     type Output = PathBuf;
 401
 402     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 403         run.path("src/tools/error_index_generator")
 404     }
 405
 406     fn make_run(run: RunConfig<'_>) {
 407         // Compile the error-index in the same stage as rustdoc to avoid
 408         // recompiling rustdoc twice if we can.
 409         let stage = if run.builder.top_stage >= 2 { run.builder.top_stage } else { 0 };
 410         run.builder
 411             .ensure(ErrorIndex { compiler: run.builder.compiler(stage, run.builder.config.build) });
 412     }
 413
 414     fn run(self, builder: &Builder<'_>) -> PathBuf {
 415         builder
 416             .ensure(ToolBuild {
 417                 compiler: self.compiler,
 418                 target: self.compiler.host,
 419                 tool: "error_index_generator",
 420                 mode: Mode::ToolRustc,
 421                 path: "src/tools/error_index_generator",
 422                 is_optional_tool: false,
 423                 source_type: SourceType::InTree,
 424                 extra_features: Vec::new(),
 425             })
 426             .expect("expected to build -- essential tool")
 427     }
 428 }
 429
 430 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 431 pub struct RemoteTestServer {
 432     pub compiler: Compiler,
 433     pub target: Interned<String>,
 434 }
 435
 436 impl Step for RemoteTestServer {
 437     type Output = PathBuf;
 438
 439     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 440         run.path("src/tools/remote-test-server")
 441     }
 442
 443     fn make_run(run: RunConfig<'_>) {
 444         run.builder.ensure(RemoteTestServer {
 445             compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
 446             target: run.target,
 447         });
 448     }
 449
 450     fn run(self, builder: &Builder<'_>) -> PathBuf {
 451         builder
 452             .ensure(ToolBuild {
 453                 compiler: self.compiler,
 454                 target: self.target,
 455                 tool: "remote-test-server",
 456                 mode: Mode::ToolStd,
 457                 path: "src/tools/remote-test-server",
 458                 is_optional_tool: false,
 459                 source_type: SourceType::InTree,
 460                 extra_features: Vec::new(),
 461             })
 462             .expect("expected to build -- essential tool")
 463     }
 464 }
 465
 466 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 467 pub struct Rustdoc {
 468     /// This should only ever be 0 or 2.
 469     /// We sometimes want to reference the "bootstrap" rustdoc, which is why this option is here.
 470     pub compiler: Compiler,
 471 }
 472
 473 impl Step for Rustdoc {
 474     type Output = PathBuf;
 475     const DEFAULT: bool = true;
 476     const ONLY_HOSTS: bool = true;
 477
 478     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 479         run.path("src/tools/rustdoc")
 480     }
 481
 482     fn make_run(run: RunConfig<'_>) {
 483         run.builder
 484             .ensure(Rustdoc { compiler: run.builder.compiler(run.builder.top_stage, run.host) });
 485     }
 486
 487     fn run(self, builder: &Builder<'_>) -> PathBuf {
 488         let target_compiler = self.compiler;
 489         if target_compiler.stage == 0 {
 490             if !target_compiler.is_snapshot(builder) {
 491                 panic!("rustdoc in stage 0 must be snapshot rustdoc");
 492             }
 493             return builder.initial_rustc.with_file_name(exe("rustdoc", &target_compiler.host));
 494         }
 495         let target = target_compiler.host;
 496         // Similar to `compile::Assemble`, build with the previous stage's compiler. Otherwise
 497         // we'd have stageN/bin/rustc and stageN/bin/rustdoc be effectively different stage
 498         // compilers, which isn't what we want. Rustdoc should be linked in the same way as the
 499         // rustc compiler it's paired with, so it must be built with the previous stage compiler.
 500         let build_compiler = builder.compiler(target_compiler.stage - 1, builder.config.build);
 501
 502         // The presence of `target_compiler` ensures that the necessary libraries (codegen backends,
 503         // compiler libraries, ...) are built. Rustdoc does not require the presence of any
 504         // libraries within sysroot_libdir (i.e., rustlib), though doctests may want it (since
 505         // they'll be linked to those libraries). As such, don't explicitly `ensure` any additional
 506         // libraries here. The intuition here is that If we've built a compiler, we should be able
 507         // to build rustdoc.
 508
 509         let cargo = prepare_tool_cargo(
 510             builder,
 511             build_compiler,
 512             Mode::ToolRustc,
 513             target,
 514             "build",
 515             "src/tools/rustdoc",
 516             SourceType::InTree,
 517             &[],
 518         );
 519
 520         builder.info(&format!(
 521             "Building rustdoc for stage{} ({})",
 522             target_compiler.stage, target_compiler.host
 523         ));
 524         builder.run(&mut cargo.into());
 525
 526         // Cargo adds a number of paths to the dylib search path on windows, which results in
 527         // the wrong rustdoc being executed. To avoid the conflicting rustdocs, we name the "tool"
 528         // rustdoc a different name.
 529         let tool_rustdoc = builder
 530             .cargo_out(build_compiler, Mode::ToolRustc, target)
 531             .join(exe("rustdoc_tool_binary", &target_compiler.host));
 532
 533         // don't create a stage0-sysroot/bin directory.
 534         if target_compiler.stage > 0 {
 535             let sysroot = builder.sysroot(target_compiler);
 536             let bindir = sysroot.join("bin");
 537             t!(fs::create_dir_all(&bindir));
 538             let bin_rustdoc = bindir.join(exe("rustdoc", &*target_compiler.host));
 539             let _ = fs::remove_file(&bin_rustdoc);
 540             builder.copy(&tool_rustdoc, &bin_rustdoc);
 541             bin_rustdoc
 542         } else {
 543             tool_rustdoc
 544         }
 545     }
 546 }
 547
 548 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 549 pub struct Cargo {
 550     pub compiler: Compiler,
 551     pub target: Interned<String>,
 552 }
 553
 554 impl Step for Cargo {
 555     type Output = PathBuf;
 556     const DEFAULT: bool = true;
 557     const ONLY_HOSTS: bool = true;
 558
 559     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 560         let builder = run.builder;
 561         run.path("src/tools/cargo").default_condition(builder.config.extended)
 562     }
 563
 564     fn make_run(run: RunConfig<'_>) {
 565         run.builder.ensure(Cargo {
 566             compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
 567             target: run.target,
 568         });
 569     }
 570
 571     fn run(self, builder: &Builder<'_>) -> PathBuf {
 572         builder
 573             .ensure(ToolBuild {
 574                 compiler: self.compiler,
 575                 target: self.target,
 576                 tool: "cargo",
 577                 mode: Mode::ToolRustc,
 578                 path: "src/tools/cargo",
 579                 is_optional_tool: false,
 580                 source_type: SourceType::Submodule,
 581                 extra_features: Vec::new(),
 582             })
 583             .expect("expected to build -- essential tool")
 584     }
 585 }
 586
 587 macro_rules! tool_extended {
 588     (($sel:ident, $builder:ident),
 589        $($name:ident,
 590        $toolstate:ident,
 591        $path:expr,
 592        $tool_name:expr,
 593        $extra_deps:block;)+) => {
 594         $(
 595             #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 596         pub struct $name {
 597             pub compiler: Compiler,
 598             pub target: Interned<String>,
 599             pub extra_features: Vec<String>,
 600         }
 601
 602         impl Step for $name {
 603             type Output = Option<PathBuf>;
 604             const DEFAULT: bool = true;
 605             const ONLY_HOSTS: bool = true;
 606
 607             fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 608                 let builder = run.builder;
 609                 run.path($path).default_condition(builder.config.extended)
 610             }
 611
 612             fn make_run(run: RunConfig<'_>) {
 613                 run.builder.ensure($name {
 614                     compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
 615                     target: run.target,
 616                     extra_features: Vec::new(),
 617                 });
 618             }
 619
 620             #[allow(unused_mut)]
 621             fn run(mut $sel, $builder: &Builder<'_>) -> Option<PathBuf> {
 622                 $extra_deps
 623                 $builder.ensure(ToolBuild {
 624                     compiler: $sel.compiler,
 625                     target: $sel.target,
 626                     tool: $tool_name,
 627                     mode: Mode::ToolRustc,
 628                     path: $path,
 629                     extra_features: $sel.extra_features,
 630                     is_optional_tool: true,
 631                     source_type: SourceType::Submodule,
 632                 })
 633             }
 634         }
 635         )+
 636     }
 637 }
 638
 639 tool_extended!((self, builder),
 640     Cargofmt, rustfmt, "src/tools/rustfmt", "cargo-fmt", {};
 641     CargoClippy, clippy, "src/tools/clippy", "cargo-clippy", {};
 642     Clippy, clippy, "src/tools/clippy", "clippy-driver", {};
 643     Miri, miri, "src/tools/miri", "miri", {};
 644     CargoMiri, miri, "src/tools/miri", "cargo-miri", {};
 645     Rls, rls, "src/tools/rls", "rls", {
 646         let clippy = builder.ensure(Clippy {
 647             compiler: self.compiler,
 648             target: self.target,
 649             extra_features: Vec::new(),
 650         });
 651         if clippy.is_some() {
 652             self.extra_features.push("clippy".to_owned());
 653         }
 654     };
 655     Rustfmt, rustfmt, "src/tools/rustfmt", "rustfmt", {};
 656 );
 657
 658 impl<'a> Builder<'a> {
 659     /// Gets a `Command` which is ready to run `tool` in `stage` built for
 660     /// `host`.
 661     pub fn tool_cmd(&self, tool: Tool) -> Command {
 662         let mut cmd = Command::new(self.tool_exe(tool));
 663         let compiler = self.compiler(0, self.config.build);
 664         let host = &compiler.host;
 665         // Prepares the `cmd` provided to be able to run the `compiler` provided.
 666         //
 667         // Notably this munges the dynamic library lookup path to point to the
 668         // right location to run `compiler`.
 669         let mut lib_paths: Vec<PathBuf> = vec![
 670             self.build.rustc_snapshot_libdir(),
 671             self.cargo_out(compiler, Mode::ToolBootstrap, *host).join("deps"),
 672         ];
 673
 674         // On MSVC a tool may invoke a C compiler (e.g., compiletest in run-make
 675         // mode) and that C compiler may need some extra PATH modification. Do
 676         // so here.
 677         if compiler.host.contains("msvc") {
 678             let curpaths = env::var_os("PATH").unwrap_or_default();
 679             let curpaths = env::split_paths(&curpaths).collect::<Vec<_>>();
 680             for &(ref k, ref v) in self.cc[&compiler.host].env() {
 681                 if k != "PATH" {
 682                     continue;
 683                 }
 684                 for path in env::split_paths(v) {
 685                     if !curpaths.contains(&path) {
 686                         lib_paths.push(path);
 687                     }
 688                 }
 689             }
 690         }
 691
 692         add_lib_path(lib_paths, &mut cmd);
 693         cmd
 694     }
 695 }