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