src/bootstrap/tool.rs

   1 use std::fs;
   2 use std::env;
   3 use std::path::PathBuf;
   4 use std::process::{Command, exit};
   5 use std::collections::HashSet;
   6
   7 use crate::Mode;
   8 use crate::Compiler;
   9 use crate::builder::{Step, RunConfig, ShouldRun, Builder};
  10 use crate::util::{exe, add_lib_path};
  11 use crate::compile;
  12 use crate::channel::GitInfo;
  13 use crate::channel;
  14 use crate::cache::Interned;
  15 use crate::toolstate::ToolState;
  16
  17 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
  18 pub enum SourceType {
  19     InTree,
  20     Submodule,
  21 }
  22
  23 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
  24 struct ToolBuild {
  25     compiler: Compiler,
  26     target: Interned<String>,
  27     tool: &'static str,
  28     path: &'static str,
  29     mode: Mode,
  30     is_optional_tool: bool,
  31     source_type: SourceType,
  32     extra_features: Vec<String>,
  33 }
  34
  35 impl Step for ToolBuild {
  36     type Output = Option<PathBuf>;
  37
  38     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
  39         run.never()
  40     }
  41
  42     /// Builds a tool in `src/tools`
  43     ///
  44     /// This will build the specified tool with the specified `host` compiler in
  45     /// `stage` into the normal cargo output directory.
  46     fn run(self, builder: &Builder<'_>) -> Option<PathBuf> {
  47         let compiler = self.compiler;
  48         let target = self.target;
  49         let tool = self.tool;
  50         let path = self.path;
  51         let is_optional_tool = self.is_optional_tool;
  52
  53         match self.mode {
  54             Mode::ToolRustc => {
  55                 builder.ensure(compile::Rustc { compiler, target })
  56             }
  57             Mode::ToolStd => {
  58                 builder.ensure(compile::Std { compiler, target })
  59             }
  60             Mode::ToolBootstrap => {} // uses downloaded stage0 compiler libs
  61             _ => panic!("unexpected Mode for tool build")
  62         }
  63
  64         let mut cargo = prepare_tool_cargo(
  65             builder,
  66             compiler,
  67             self.mode,
  68             target,
  69             "build",
  70             path,
  71             self.source_type,
  72             &self.extra_features,
  73         );
  74
  75         let _folder = builder.fold_output(|| format!("stage{}-{}", compiler.stage, tool));
  76         builder.info(&format!("Building stage{} tool {} ({})", compiler.stage, tool, target));
  77         let mut duplicates = Vec::new();
  78         let is_expected = compile::stream_cargo(builder, &mut cargo, &mut |msg| {
  79             // Only care about big things like the RLS/Cargo for now
  80             match tool {
  81                 | "rls"
  82                 | "cargo"
  83                 | "clippy-driver"
  84                 | "miri"
  85                 => {}
  86
  87                 _ => return,
  88             }
  89             let (id, features, filenames) = match msg {
  90                 compile::CargoMessage::CompilerArtifact {
  91                     package_id,
  92                     features,
  93                     filenames,
  94                     target: _,
  95                 } => {
  96                     (package_id, features, filenames)
  97                 }
  98                 _ => return,
  99             };
 100             let features = features.iter().map(|s| s.to_string()).collect::<Vec<_>>();
 101
 102             for path in filenames {
 103                 let val = (tool, PathBuf::from(&*path), features.clone());
 104                 // we're only interested in deduplicating rlibs for now
 105                 if val.1.extension().and_then(|s| s.to_str()) != Some("rlib") {
 106                     continue
 107                 }
 108
 109                 // Don't worry about libs that turn out to be host dependencies
 110                 // or build scripts, we only care about target dependencies that
 111                 // are in `deps`.
 112                 if let Some(maybe_target) = val.1
 113                     .parent()                   // chop off file name
 114                     .and_then(|p| p.parent())   // chop off `deps`
 115                     .and_then(|p| p.parent())   // chop off `release`
 116                     .and_then(|p| p.file_name())
 117                     .and_then(|p| p.to_str())
 118                 {
 119                     if maybe_target != &*target {
 120                         continue
 121                     }
 122                 }
 123
 124                 let mut artifacts = builder.tool_artifacts.borrow_mut();
 125                 let prev_artifacts = artifacts
 126                     .entry(target)
 127                     .or_default();
 128                 if let Some(prev) = prev_artifacts.get(&*id) {
 129                     if prev.1 != val.1 {
 130                         duplicates.push((
 131                             id.to_string(),
 132                             val,
 133                             prev.clone(),
 134                         ));
 135                     }
 136                     return
 137                 }
 138                 prev_artifacts.insert(id.to_string(), val);
 139             }
 140         });
 141
 142         if is_expected && !duplicates.is_empty() {
 143             println!("duplicate artifacts found when compiling a tool, this \
 144                       typically means that something was recompiled because \
 145                       a transitive dependency has different features activated \
 146                       than in a previous build:\n");
 147             println!("the following dependencies are duplicated although they \
 148                       have the same features enabled:");
 149             for (id, cur, prev) in duplicates.drain_filter(|(_, cur, prev)| cur.2 == prev.2) {
 150                 println!("  {}", id);
 151                 // same features
 152                 println!("    `{}` ({:?})\n    `{}` ({:?})", cur.0, cur.1, prev.0, prev.1);
 153             }
 154             println!("the following dependencies have different features:");
 155             for (id, cur, prev) in duplicates {
 156                 println!("  {}", id);
 157                 let cur_features: HashSet<_> = cur.2.into_iter().collect();
 158                 let prev_features: HashSet<_> = prev.2.into_iter().collect();
 159                 println!("    `{}` additionally enabled features {:?} at {:?}",
 160                          cur.0, &cur_features - &prev_features, cur.1);
 161                 println!("    `{}` additionally enabled features {:?} at {:?}",
 162                          prev.0, &prev_features - &cur_features, prev.1);
 163             }
 164             println!();
 165             println!("to fix this you will probably want to edit the local \
 166                       src/tools/rustc-workspace-hack/Cargo.toml crate, as \
 167                       that will update the dependency graph to ensure that \
 168                       these crates all share the same feature set");
 169             panic!("tools should not compile multiple copies of the same crate");
 170         }
 171
 172         builder.save_toolstate(tool, if is_expected {
 173             ToolState::TestFail
 174         } else {
 175             ToolState::BuildFail
 176         });
 177
 178         if !is_expected {
 179             if !is_optional_tool {
 180                 exit(1);
 181             } else {
 182                 None
 183             }
 184         } else {
 185             let cargo_out = builder.cargo_out(compiler, self.mode, target)
 186                 .join(exe(tool, &compiler.host));
 187             let bin = builder.tools_dir(compiler).join(exe(tool, &compiler.host));
 188             builder.copy(&cargo_out, &bin);
 189             Some(bin)
 190         }
 191     }
 192 }
 193
 194 pub fn prepare_tool_cargo(
 195     builder: &Builder<'_>,
 196     compiler: Compiler,
 197     mode: Mode,
 198     target: Interned<String>,
 199     command: &'static str,
 200     path: &'static str,
 201     source_type: SourceType,
 202     extra_features: &[String],
 203 ) -> Command {
 204     let mut cargo = builder.cargo(compiler, mode, target, command);
 205     let dir = builder.src.join(path);
 206     cargo.arg("--manifest-path").arg(dir.join("Cargo.toml"));
 207
 208     // We don't want to build tools dynamically as they'll be running across
 209     // stages and such and it's just easier if they're not dynamically linked.
 210     cargo.env("RUSTC_NO_PREFER_DYNAMIC", "1");
 211
 212     if source_type == SourceType::Submodule {
 213         cargo.env("RUSTC_EXTERNAL_TOOL", "1");
 214     }
 215
 216     let mut features = extra_features.iter().cloned().collect::<Vec<_>>();
 217     if builder.build.config.cargo_native_static {
 218         if path.ends_with("cargo") ||
 219             path.ends_with("rls") ||
 220             path.ends_with("clippy") ||
 221             path.ends_with("miri") ||
 222             path.ends_with("rustfmt")
 223         {
 224             cargo.env("LIBZ_SYS_STATIC", "1");
 225             features.push("rustc-workspace-hack/all-static".to_string());
 226         }
 227     }
 228
 229     // if tools are using lzma we want to force the build script to build its
 230     // own copy
 231     cargo.env("LZMA_API_STATIC", "1");
 232
 233     cargo.env("CFG_RELEASE_CHANNEL", &builder.config.channel);
 234     cargo.env("CFG_VERSION", builder.rust_version());
 235     cargo.env("CFG_RELEASE_NUM", channel::CFG_RELEASE_NUM);
 236
 237     let info = GitInfo::new(builder.config.ignore_git, &dir);
 238     if let Some(sha) = info.sha() {
 239         cargo.env("CFG_COMMIT_HASH", sha);
 240     }
 241     if let Some(sha_short) = info.sha_short() {
 242         cargo.env("CFG_SHORT_COMMIT_HASH", sha_short);
 243     }
 244     if let Some(date) = info.commit_date() {
 245         cargo.env("CFG_COMMIT_DATE", date);
 246     }
 247     if !features.is_empty() {
 248         cargo.arg("--features").arg(&features.join(", "));
 249     }
 250     cargo
 251 }
 252
 253 macro_rules! bootstrap_tool {
 254     ($(
 255         $name:ident, $path:expr, $tool_name:expr
 256         $(,llvm_tools = $llvm:expr)*
 257         $(,is_external_tool = $external:expr)*
 258         ;
 259     )+) => {
 260         #[derive(Copy, PartialEq, Eq, Clone)]
 261         pub enum Tool {
 262             $(
 263                 $name,
 264             )+
 265         }
 266
 267         impl Tool {
 268             pub fn get_mode(&self) -> Mode {
 269                 Mode::ToolBootstrap
 270             }
 271
 272             /// Whether this tool requires LLVM to run
 273             pub fn uses_llvm_tools(&self) -> bool {
 274                 match self {
 275                     $(Tool::$name => false $(|| $llvm)*,)+
 276                 }
 277             }
 278         }
 279
 280         impl<'a> Builder<'a> {
 281             pub fn tool_exe(&self, tool: Tool) -> PathBuf {
 282                 match tool {
 283                     $(Tool::$name =>
 284                         self.ensure($name {
 285                             compiler: self.compiler(0, self.config.build),
 286                             target: self.config.build,
 287                         }),
 288                     )+
 289                 }
 290             }
 291         }
 292
 293         $(
 294             #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 295         pub struct $name {
 296             pub compiler: Compiler,
 297             pub target: Interned<String>,
 298         }
 299
 300         impl Step for $name {
 301             type Output = PathBuf;
 302
 303             fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 304                 run.path($path)
 305             }
 306
 307             fn make_run(run: RunConfig<'_>) {
 308                 run.builder.ensure($name {
 309                     // snapshot compiler
 310                     compiler: run.builder.compiler(0, run.builder.config.build),
 311                     target: run.target,
 312                 });
 313             }
 314
 315             fn run(self, builder: &Builder<'_>) -> PathBuf {
 316                 builder.ensure(ToolBuild {
 317                     compiler: self.compiler,
 318                     target: self.target,
 319                     tool: $tool_name,
 320                     mode: Mode::ToolBootstrap,
 321                     path: $path,
 322                     is_optional_tool: false,
 323                     source_type: if false $(|| $external)* {
 324                         SourceType::Submodule
 325                     } else {
 326                         SourceType::InTree
 327                     },
 328                     extra_features: Vec::new(),
 329                 }).expect("expected to build -- essential tool")
 330             }
 331         }
 332         )+
 333     }
 334 }
 335
 336 bootstrap_tool!(
 337     Rustbook, "src/tools/rustbook", "rustbook";
 338     UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen";
 339     Tidy, "src/tools/tidy", "tidy";
 340     Linkchecker, "src/tools/linkchecker", "linkchecker";
 341     CargoTest, "src/tools/cargotest", "cargotest";
 342     Compiletest, "src/tools/compiletest", "compiletest", llvm_tools = true;
 343     BuildManifest, "src/tools/build-manifest", "build-manifest";
 344     RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
 345     RustInstaller, "src/tools/rust-installer", "fabricate", is_external_tool = true;
 346     RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes";
 347 );
 348
 349 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 350 pub struct ErrorIndex {
 351     pub compiler: Compiler,
 352 }
 353
 354 impl ErrorIndex {
 355     pub fn command(builder: &Builder<'_>, compiler: Compiler) -> Command {
 356         let mut cmd = Command::new(builder.ensure(ErrorIndex {
 357             compiler
 358         }));
 359         add_lib_path(
 360             vec![PathBuf::from(&builder.sysroot_libdir(compiler, compiler.host))],
 361             &mut cmd,
 362         );
 363         cmd
 364     }
 365 }
 366
 367 impl Step for ErrorIndex {
 368     type Output = PathBuf;
 369
 370     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 371         run.path("src/tools/error_index_generator")
 372     }
 373
 374     fn make_run(run: RunConfig<'_>) {
 375         // Compile the error-index in the same stage as rustdoc to avoid
 376         // recompiling rustdoc twice if we can.
 377         let stage = if run.builder.top_stage >= 2 { run.builder.top_stage } else { 0 };
 378         run.builder.ensure(ErrorIndex {
 379             compiler: run.builder.compiler(stage, run.builder.config.build),
 380         });
 381     }
 382
 383     fn run(self, builder: &Builder<'_>) -> PathBuf {
 384         builder.ensure(ToolBuild {
 385             compiler: self.compiler,
 386             target: self.compiler.host,
 387             tool: "error_index_generator",
 388             mode: Mode::ToolRustc,
 389             path: "src/tools/error_index_generator",
 390             is_optional_tool: false,
 391             source_type: SourceType::InTree,
 392             extra_features: Vec::new(),
 393         }).expect("expected to build -- essential tool")
 394     }
 395 }
 396
 397 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 398 pub struct RemoteTestServer {
 399     pub compiler: Compiler,
 400     pub target: Interned<String>,
 401 }
 402
 403 impl Step for RemoteTestServer {
 404     type Output = PathBuf;
 405
 406     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 407         run.path("src/tools/remote-test-server")
 408     }
 409
 410     fn make_run(run: RunConfig<'_>) {
 411         run.builder.ensure(RemoteTestServer {
 412             compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
 413             target: run.target,
 414         });
 415     }
 416
 417     fn run(self, builder: &Builder<'_>) -> PathBuf {
 418         builder.ensure(ToolBuild {
 419             compiler: self.compiler,
 420             target: self.target,
 421             tool: "remote-test-server",
 422             mode: Mode::ToolStd,
 423             path: "src/tools/remote-test-server",
 424             is_optional_tool: false,
 425             source_type: SourceType::InTree,
 426             extra_features: Vec::new(),
 427         }).expect("expected to build -- essential tool")
 428     }
 429 }
 430
 431 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 432 pub struct Rustdoc {
 433     /// This should only ever be 0 or 2.
 434     /// We sometimes want to reference the "bootstrap" rustdoc, which is why this option is here.
 435     pub compiler: Compiler,
 436 }
 437
 438 impl Step for Rustdoc {
 439     type Output = PathBuf;
 440     const DEFAULT: bool = true;
 441     const ONLY_HOSTS: bool = true;
 442
 443     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 444         run.path("src/tools/rustdoc")
 445     }
 446
 447     fn make_run(run: RunConfig<'_>) {
 448         run.builder.ensure(Rustdoc {
 449             compiler: run.builder.compiler(run.builder.top_stage, run.host),
 450         });
 451     }
 452
 453     fn run(self, builder: &Builder<'_>) -> PathBuf {
 454         let target_compiler = self.compiler;
 455         if target_compiler.stage == 0 {
 456             if !target_compiler.is_snapshot(builder) {
 457                 panic!("rustdoc in stage 0 must be snapshot rustdoc");
 458             }
 459             return builder.initial_rustc.with_file_name(exe("rustdoc", &target_compiler.host));
 460         }
 461         let target = target_compiler.host;
 462         // Similar to `compile::Assemble`, build with the previous stage's compiler. Otherwise
 463         // we'd have stageN/bin/rustc and stageN/bin/rustdoc be effectively different stage
 464         // compilers, which isn't what we want. Rustdoc should be linked in the same way as the
 465         // rustc compiler it's paired with, so it must be built with the previous stage compiler.
 466         let build_compiler = builder.compiler(target_compiler.stage - 1, builder.config.build);
 467
 468         // The presence of `target_compiler` ensures that the necessary libraries (codegen backends,
 469         // compiler libraries, ...) are built. Rustdoc does not require the presence of any
 470         // libraries within sysroot_libdir (i.e., rustlib), though doctests may want it (since
 471         // they'll be linked to those libraries). As such, don't explicitly `ensure` any additional
 472         // libraries here. The intuition here is that If we've built a compiler, we should be able
 473         // to build rustdoc.
 474
 475         let mut cargo = prepare_tool_cargo(
 476             builder,
 477             build_compiler,
 478             Mode::ToolRustc,
 479             target,
 480             "build",
 481             "src/tools/rustdoc",
 482             SourceType::InTree,
 483             &[],
 484         );
 485
 486         // Most tools don't get debuginfo, but rustdoc should.
 487         cargo.env("RUSTC_DEBUGINFO", builder.config.rust_debuginfo.to_string())
 488              .env("RUSTC_DEBUGINFO_LINES", builder.config.rust_debuginfo_lines.to_string());
 489
 490         let _folder = builder.fold_output(|| format!("stage{}-rustdoc", target_compiler.stage));
 491         builder.info(&format!("Building rustdoc for stage{} ({})",
 492             target_compiler.stage, target_compiler.host));
 493         builder.run(&mut cargo);
 494
 495         // Cargo adds a number of paths to the dylib search path on windows, which results in
 496         // the wrong rustdoc being executed. To avoid the conflicting rustdocs, we name the "tool"
 497         // rustdoc a different name.
 498         let tool_rustdoc = builder.cargo_out(build_compiler, Mode::ToolRustc, target)
 499             .join(exe("rustdoc_tool_binary", &target_compiler.host));
 500
 501         // don't create a stage0-sysroot/bin directory.
 502         if target_compiler.stage > 0 {
 503             let sysroot = builder.sysroot(target_compiler);
 504             let bindir = sysroot.join("bin");
 505             t!(fs::create_dir_all(&bindir));
 506             let bin_rustdoc = bindir.join(exe("rustdoc", &*target_compiler.host));
 507             let _ = fs::remove_file(&bin_rustdoc);
 508             builder.copy(&tool_rustdoc, &bin_rustdoc);
 509             bin_rustdoc
 510         } else {
 511             tool_rustdoc
 512         }
 513     }
 514 }
 515
 516 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 517 pub struct Cargo {
 518     pub compiler: Compiler,
 519     pub target: Interned<String>,
 520 }
 521
 522 impl Step for Cargo {
 523     type Output = PathBuf;
 524     const DEFAULT: bool = true;
 525     const ONLY_HOSTS: bool = true;
 526
 527     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 528         let builder = run.builder;
 529         run.path("src/tools/cargo").default_condition(builder.config.extended)
 530     }
 531
 532     fn make_run(run: RunConfig<'_>) {
 533         run.builder.ensure(Cargo {
 534             compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
 535             target: run.target,
 536         });
 537     }
 538
 539     fn run(self, builder: &Builder<'_>) -> PathBuf {
 540         // Cargo depends on procedural macros, which requires a full host
 541         // compiler to be available, so we need to depend on that.
 542         builder.ensure(compile::Rustc {
 543             compiler: self.compiler,
 544             target: builder.config.build,
 545         });
 546         builder.ensure(ToolBuild {
 547             compiler: self.compiler,
 548             target: self.target,
 549             tool: "cargo",
 550             mode: Mode::ToolRustc,
 551             path: "src/tools/cargo",
 552             is_optional_tool: false,
 553             source_type: SourceType::Submodule,
 554             extra_features: Vec::new(),
 555         }).expect("expected to build -- essential tool")
 556     }
 557 }
 558
 559 macro_rules! tool_extended {
 560     (($sel:ident, $builder:ident),
 561        $($name:ident,
 562        $toolstate:ident,
 563        $path:expr,
 564        $tool_name:expr,
 565        $extra_deps:block;)+) => {
 566         $(
 567             #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 568         pub struct $name {
 569             pub compiler: Compiler,
 570             pub target: Interned<String>,
 571             pub extra_features: Vec<String>,
 572         }
 573
 574         impl Step for $name {
 575             type Output = Option<PathBuf>;
 576             const DEFAULT: bool = true;
 577             const ONLY_HOSTS: bool = true;
 578
 579             fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
 580                 let builder = run.builder;
 581                 run.path($path).default_condition(builder.config.extended)
 582             }
 583
 584             fn make_run(run: RunConfig<'_>) {
 585                 run.builder.ensure($name {
 586                     compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
 587                     target: run.target,
 588                     extra_features: Vec::new(),
 589                 });
 590             }
 591
 592             #[allow(unused_mut)]
 593             fn run(mut $sel, $builder: &Builder<'_>) -> Option<PathBuf> {
 594                 $extra_deps
 595                 $builder.ensure(ToolBuild {
 596                     compiler: $sel.compiler,
 597                     target: $sel.target,
 598                     tool: $tool_name,
 599                     mode: Mode::ToolRustc,
 600                     path: $path,
 601                     extra_features: $sel.extra_features,
 602                     is_optional_tool: true,
 603                     source_type: SourceType::Submodule,
 604                 })
 605             }
 606         }
 607         )+
 608     }
 609 }
 610
 611 tool_extended!((self, builder),
 612     Cargofmt, rustfmt, "src/tools/rustfmt", "cargo-fmt", {};
 613     CargoClippy, clippy, "src/tools/clippy", "cargo-clippy", {
 614         // Clippy depends on procedural macros (serde), which requires a full host
 615         // compiler to be available, so we need to depend on that.
 616         builder.ensure(compile::Rustc {
 617             compiler: self.compiler,
 618             target: builder.config.build,
 619         });
 620     };
 621     Clippy, clippy, "src/tools/clippy", "clippy-driver", {
 622         // Clippy depends on procedural macros (serde), which requires a full host
 623         // compiler to be available, so we need to depend on that.
 624         builder.ensure(compile::Rustc {
 625             compiler: self.compiler,
 626             target: builder.config.build,
 627         });
 628     };
 629     Miri, miri, "src/tools/miri", "miri", {};
 630     CargoMiri, miri, "src/tools/miri", "cargo-miri", {
 631         // Miri depends on procedural macros (serde), which requires a full host
 632         // compiler to be available, so we need to depend on that.
 633         builder.ensure(compile::Rustc {
 634             compiler: self.compiler,
 635             target: builder.config.build,
 636         });
 637     };
 638     Rls, rls, "src/tools/rls", "rls", {
 639         let clippy = builder.ensure(Clippy {
 640             compiler: self.compiler,
 641             target: self.target,
 642             extra_features: Vec::new(),
 643         });
 644         if clippy.is_some() {
 645             self.extra_features.push("clippy".to_owned());
 646         }
 647         // RLS depends on procedural macros, which requires a full host
 648         // compiler to be available, so we need to depend on that.
 649         builder.ensure(compile::Rustc {
 650             compiler: self.compiler,
 651             target: builder.config.build,
 652         });
 653     };
 654     Rustfmt, rustfmt, "src/tools/rustfmt", "rustfmt", {};
 655 );
 656
 657 impl<'a> Builder<'a> {
 658     /// Gets a `Command` which is ready to run `tool` in `stage` built for
 659     /// `host`.
 660     pub fn tool_cmd(&self, tool: Tool) -> Command {
 661         let mut cmd = Command::new(self.tool_exe(tool));
 662         let compiler = self.compiler(0, self.config.build);
 663         self.prepare_tool_cmd(compiler, tool, &mut cmd);
 664         cmd
 665     }
 666
 667     /// Prepares the `cmd` provided to be able to run the `compiler` provided.
 668     ///
 669     /// Notably this munges the dynamic library lookup path to point to the
 670     /// right location to run `compiler`.
 671     fn prepare_tool_cmd(&self, compiler: Compiler, tool: Tool, cmd: &mut Command) {
 672         let host = &compiler.host;
 673         let mut lib_paths: Vec<PathBuf> = vec![
 674             if compiler.stage == 0 {
 675                 self.build.rustc_snapshot_libdir()
 676             } else {
 677                 PathBuf::from(&self.sysroot_libdir(compiler, compiler.host))
 678             },
 679             self.cargo_out(compiler, tool.get_mode(), *host).join("deps"),
 680         ];
 681
 682         // On MSVC a tool may invoke a C compiler (e.g., compiletest in run-make
 683         // mode) and that C compiler may need some extra PATH modification. Do
 684         // so here.
 685         if compiler.host.contains("msvc") {
 686             let curpaths = env::var_os("PATH").unwrap_or_default();
 687             let curpaths = env::split_paths(&curpaths).collect::<Vec<_>>();
 688             for &(ref k, ref v) in self.cc[&compiler.host].env() {
 689                 if k != "PATH" {
 690                     continue
 691                 }
 692                 for path in env::split_paths(v) {
 693                     if !curpaths.contains(&path) {
 694                         lib_paths.push(path);
 695                     }
 696                 }
 697             }
 698         }
 699
 700         add_lib_path(lib_paths, cmd);
 701     }
 702 }