src/bootstrap/compile.rs - third_party/rust - Git at Google

 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.

 //! Implementation of compiling various phases of the compiler and standard
 //! library.
 //!
 //! This module contains some of the real meat in the rustbuild build system
 //! which is where Cargo is used to compiler the standard library, libtest, and
 //! compiler. This module is also responsible for assembling the sysroot as it
 //! goes along from the output of the previous stage.

 use std::collections::HashMap;
 use std::fs;
 use std::path::{Path, PathBuf};
 use std::process::Command;

 use build_helper::output;

 use util::{exe, staticlib, libdir, mtime, is_dylib, copy};
 use {Build, Compiler, Mode};

 /// Build the standard library.
 ///
 /// This will build the standard library for a particular stage of the build
 /// using the `compiler` targeting the `target` architecture. The artifacts
 /// created will also be linked into the sysroot directory.
 pub fn std<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
     println!("Building stage{} std artifacts ({} -> {})", compiler.stage,
              compiler.host, target);

     // Move compiler-rt into place as it'll be required by the compiler when
     // building the standard library to link the dylib of libstd
     let libdir = build.sysroot_libdir(compiler, target);
     let _ = fs::remove_dir_all(&libdir);
     t!(fs::create_dir_all(&libdir));
     copy(&build.compiler_rt_built.borrow()[target],
          &libdir.join(staticlib("compiler-rt", target)));

     // Some platforms have startup objects that may be required to produce the
     // libstd dynamic library, for example.
     build_startup_objects(build, target, &libdir);

     let out_dir = build.cargo_out(compiler, Mode::Libstd, target);
     build.clear_if_dirty(&out_dir, &build.compiler_path(compiler));
     let mut cargo = build.cargo(compiler, Mode::Libstd, target, "build");
     cargo.arg("--features").arg(build.std_features())
          .arg("--manifest-path")
          .arg(build.src.join("src/rustc/std_shim/Cargo.toml"));

     if let Some(target) = build.config.target_config.get(target) {
         if let Some(ref jemalloc) = target.jemalloc {
             cargo.env("JEMALLOC_OVERRIDE", jemalloc);
         }
     }
     if let Some(ref p) = build.config.musl_root {
         if target.contains("musl") {
             cargo.env("MUSL_ROOT", p);
         }
     }

     build.run(&mut cargo);
     std_link(build, target, compiler, compiler.host);
 }

 /// Link all libstd rlibs/dylibs into the sysroot location.
 ///
 /// Links those artifacts generated in the given `stage` for `target` produced
 /// by `compiler` into `host`'s sysroot.
 pub fn std_link(build: &Build,
                 target: &str,
                 compiler: &Compiler,
                 host: &str) {
     let target_compiler = Compiler::new(compiler.stage, host);
     let libdir = build.sysroot_libdir(&target_compiler, target);
     let out_dir = build.cargo_out(compiler, Mode::Libstd, target);

     // If we're linking one compiler host's output into another, then we weren't
     // called from the `std` method above. In that case we clean out what's
     // already there and then also link compiler-rt into place.
     if host != compiler.host {
         let _ = fs::remove_dir_all(&libdir);
         t!(fs::create_dir_all(&libdir));
         copy(&build.compiler_rt_built.borrow()[target],
              &libdir.join(staticlib("compiler-rt", target)));
     }
     add_to_sysroot(&out_dir, &libdir);

     if target.contains("musl") &&
        (target.contains("x86_64") || target.contains("i686")) {
         copy_third_party_objects(build, target, &libdir);
     }
 }

 /// Copies the crt(1,i,n).o startup objects
 ///
 /// Only required for musl targets that statically link to libc
 fn copy_third_party_objects(build: &Build, target: &str, into: &Path) {
     for &obj in &["crt1.o", "crti.o", "crtn.o"] {
         copy(&compiler_file(build.cc(target), obj), &into.join(obj));
     }
 }

 /// Build and prepare startup objects like rsbegin.o and rsend.o
 ///
 /// These are primarily used on Windows right now for linking executables/dlls.
 /// They don't require any library support as they're just plain old object
 /// files, so we just use the nightly snapshot compiler to always build them (as
 /// no other compilers are guaranteed to be available).
 fn build_startup_objects(build: &Build, target: &str, into: &Path) {
     if !target.contains("pc-windows-gnu") {
         return
     }
     let compiler = Compiler::new(0, &build.config.build);
     let compiler = build.compiler_path(&compiler);

     for file in t!(fs::read_dir(build.src.join("src/rtstartup"))) {
         let file = t!(file);
         build.run(Command::new(&compiler)
                           .arg("--emit=obj")
                           .arg("--out-dir").arg(into)
                           .arg(file.path()));
     }

     for obj in ["crt2.o", "dllcrt2.o"].iter() {
         copy(&compiler_file(build.cc(target), obj), &into.join(obj));
     }
 }

 /// Build libtest.
 ///
 /// This will build libtest and supporting libraries for a particular stage of
 /// the build using the `compiler` targeting the `target` architecture. The
 /// artifacts created will also be linked into the sysroot directory.
 pub fn test<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
     println!("Building stage{} test artifacts ({} -> {})", compiler.stage,
              compiler.host, target);
     let out_dir = build.cargo_out(compiler, Mode::Libtest, target);
     build.clear_if_dirty(&out_dir, &libstd_shim(build, compiler, target));
     let mut cargo = build.cargo(compiler, Mode::Libtest, target, "build");
     cargo.arg("--manifest-path")
          .arg(build.src.join("src/rustc/test_shim/Cargo.toml"));
     build.run(&mut cargo);
     test_link(build, target, compiler, compiler.host);
 }

 /// Link all libtest rlibs/dylibs into the sysroot location.
 ///
 /// Links those artifacts generated in the given `stage` for `target` produced
 /// by `compiler` into `host`'s sysroot.
 pub fn test_link(build: &Build,
                  target: &str,
                  compiler: &Compiler,
                  host: &str) {
     let target_compiler = Compiler::new(compiler.stage, host);
     let libdir = build.sysroot_libdir(&target_compiler, target);
     let out_dir = build.cargo_out(compiler, Mode::Libtest, target);
     add_to_sysroot(&out_dir, &libdir);
 }

 /// Build the compiler.
 ///
 /// This will build the compiler for a particular stage of the build using
 /// the `compiler` targeting the `target` architecture. The artifacts
 /// created will also be linked into the sysroot directory.
 pub fn rustc<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
     println!("Building stage{} compiler artifacts ({} -> {})",
              compiler.stage, compiler.host, target);

     let out_dir = build.cargo_out(compiler, Mode::Librustc, target);
     build.clear_if_dirty(&out_dir, &libtest_shim(build, compiler, target));

     let mut cargo = build.cargo(compiler, Mode::Librustc, target, "build");
     cargo.arg("--features").arg(build.rustc_features())
          .arg("--manifest-path")
          .arg(build.src.join("src/rustc/Cargo.toml"));

     // Set some configuration variables picked up by build scripts and
     // the compiler alike
     cargo.env("CFG_RELEASE", &build.release)
          .env("CFG_RELEASE_CHANNEL", &build.config.channel)
          .env("CFG_VERSION", &build.version)
          .env("CFG_BOOTSTRAP_KEY", &build.bootstrap_key)
          .env("CFG_PREFIX", build.config.prefix.clone().unwrap_or(String::new()))
          .env("CFG_LIBDIR_RELATIVE", "lib");

     if let Some(ref ver_date) = build.ver_date {
         cargo.env("CFG_VER_DATE", ver_date);
     }
     if let Some(ref ver_hash) = build.ver_hash {
         cargo.env("CFG_VER_HASH", ver_hash);
     }
     if !build.unstable_features {
         cargo.env("CFG_DISABLE_UNSTABLE_FEATURES", "1");
     }
     cargo.env("LLVM_CONFIG", build.llvm_config(target));
     if build.config.llvm_static_stdcpp {
         cargo.env("LLVM_STATIC_STDCPP",
                   compiler_file(build.cxx(target), "libstdc++.a"));
     }
     if let Some(ref s) = build.config.rustc_default_linker {
         cargo.env("CFG_DEFAULT_LINKER", s);
     }
     if let Some(ref s) = build.config.rustc_default_ar {
         cargo.env("CFG_DEFAULT_AR", s);
     }
     build.run(&mut cargo);

     rustc_link(build, target, compiler, compiler.host);
 }

 /// Link all librustc rlibs/dylibs into the sysroot location.
 ///
 /// Links those artifacts generated in the given `stage` for `target` produced
 /// by `compiler` into `host`'s sysroot.
 pub fn rustc_link(build: &Build,
                   target: &str,
                   compiler: &Compiler,
                   host: &str) {
     let target_compiler = Compiler::new(compiler.stage, host);
     let libdir = build.sysroot_libdir(&target_compiler, target);
     let out_dir = build.cargo_out(compiler, Mode::Librustc, target);
     add_to_sysroot(&out_dir, &libdir);
 }

 /// Cargo's output path for the standard library in a given stage, compiled
 /// by a particular compiler for the specified target.
 fn libstd_shim(build: &Build, compiler: &Compiler, target: &str) -> PathBuf {
     build.cargo_out(compiler, Mode::Libstd, target).join("libstd_shim.rlib")
 }

 /// Cargo's output path for libtest in a given stage, compiled by a particular
 /// compiler for the specified target.
 fn libtest_shim(build: &Build, compiler: &Compiler, target: &str) -> PathBuf {
     build.cargo_out(compiler, Mode::Libtest, target).join("libtest_shim.rlib")
 }

 fn compiler_file(compiler: &Path, file: &str) -> PathBuf {
     let out = output(Command::new(compiler)
                             .arg(format!("-print-file-name={}", file)));
     PathBuf::from(out.trim())
 }

 /// Prepare a new compiler from the artifacts in `stage`
 ///
 /// This will assemble a compiler in `build/$host/stage$stage`. The compiler
 /// must have been previously produced by the `stage - 1` build.config.build
 /// compiler.
 pub fn assemble_rustc(build: &Build, stage: u32, host: &str) {
     assert!(stage > 0, "the stage0 compiler isn't assembled, it's downloaded");
     // The compiler that we're assembling
     let target_compiler = Compiler::new(stage, host);

     // The compiler that compiled the compiler we're assembling
     let build_compiler = Compiler::new(stage - 1, &build.config.build);

     // Clear out old files
     let sysroot = build.sysroot(&target_compiler);
     let _ = fs::remove_dir_all(&sysroot);
     t!(fs::create_dir_all(&sysroot));

     // Link in all dylibs to the libdir
     let sysroot_libdir = sysroot.join(libdir(host));
     t!(fs::create_dir_all(&sysroot_libdir));
     let src_libdir = build.sysroot_libdir(&build_compiler, host);
     for f in t!(fs::read_dir(&src_libdir)).map(|f| t!(f)) {
         let filename = f.file_name().into_string().unwrap();
         if is_dylib(&filename) {
             copy(&f.path(), &sysroot_libdir.join(&filename));
         }
     }

     let out_dir = build.cargo_out(&build_compiler, Mode::Librustc, host);

     // Link the compiler binary itself into place
     let rustc = out_dir.join(exe("rustc", host));
     let bindir = sysroot.join("bin");
     t!(fs::create_dir_all(&bindir));
     let compiler = build.compiler_path(&Compiler::new(stage, host));
     let _ = fs::remove_file(&compiler);
     copy(&rustc, &compiler);

     // See if rustdoc exists to link it into place
     let rustdoc = exe("rustdoc", host);
     let rustdoc_src = out_dir.join(&rustdoc);
     let rustdoc_dst = bindir.join(&rustdoc);
     if fs::metadata(&rustdoc_src).is_ok() {
         let _ = fs::remove_file(&rustdoc_dst);
         copy(&rustdoc_src, &rustdoc_dst);
     }
 }

 /// Link some files into a rustc sysroot.
 ///
 /// For a particular stage this will link all of the contents of `out_dir`
 /// into the sysroot of the `host` compiler, assuming the artifacts are
 /// compiled for the specified `target`.
 fn add_to_sysroot(out_dir: &Path, sysroot_dst: &Path) {
     // Collect the set of all files in the dependencies directory, keyed
     // off the name of the library. We assume everything is of the form
     // `foo-<hash>.{rlib,so,...}`, and there could be multiple different
     // `<hash>` values for the same name (of old builds).
     let mut map = HashMap::new();
     for file in t!(fs::read_dir(out_dir.join("deps"))).map(|f| t!(f)) {
         let filename = file.file_name().into_string().unwrap();

         // We're only interested in linking rlibs + dylibs, other things like
         // unit tests don't get linked in
         if !filename.ends_with(".rlib") &&
            !filename.ends_with(".lib") &&
            !is_dylib(&filename) {
             continue
         }
         let file = file.path();
         let dash = filename.find("-").unwrap();
         let key = (filename[..dash].to_string(),
                    file.extension().unwrap().to_owned());
         map.entry(key).or_insert(Vec::new())
            .push(file.clone());
     }

     // For all hash values found, pick the most recent one to move into the
     // sysroot, that should be the one we just built.
     for (_, paths) in map {
         let (_, path) = paths.iter().map(|path| {
             (mtime(&path).seconds(), path)
         }).max().unwrap();
         copy(&path, &sysroot_dst.join(path.file_name().unwrap()));
     }
 }

 /// Build a tool in `src/tools`
 ///
 /// This will build the specified tool with the specified `host` compiler in
 /// `stage` into the normal cargo output directory.
 pub fn tool(build: &Build, stage: u32, host: &str, tool: &str) {
     println!("Building stage{} tool {} ({})", stage, tool, host);

     let compiler = Compiler::new(stage, host);

     // FIXME: need to clear out previous tool and ideally deps, may require
     //        isolating output directories or require a pseudo shim step to
     //        clear out all the info.
     //
     //        Maybe when libstd is compiled it should clear out the rustc of the
     //        corresponding stage?
     // let out_dir = build.cargo_out(stage, &host, Mode::Librustc, target);
     // build.clear_if_dirty(&out_dir, &libstd_shim(build, stage, &host, target));

     let mut cargo = build.cargo(&compiler, Mode::Tool, host, "build");
     cargo.arg("--manifest-path")
          .arg(build.src.join(format!("src/tools/{}/Cargo.toml", tool)));
     build.run(&mut cargo);
 }
	// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
	// file at the top-level directory of this distribution and at
	// http://rust-lang.org/COPYRIGHT.
	//
	// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
	// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
	// option. This file may not be copied, modified, or distributed
	// except according to those terms.

	//! Implementation of compiling various phases of the compiler and standard
	//! library.
	//!
	//! This module contains some of the real meat in the rustbuild build system
	//! which is where Cargo is used to compiler the standard library, libtest, and
	//! compiler. This module is also responsible for assembling the sysroot as it
	//! goes along from the output of the previous stage.

	use std::collections::HashMap;
	use std::fs;
	use std::path::{Path, PathBuf};
	use std::process::Command;

	use build_helper::output;

	use util::{exe, staticlib, libdir, mtime, is_dylib, copy};
	use {Build, Compiler, Mode};

	/// Build the standard library.
	///
	/// This will build the standard library for a particular stage of the build
	/// using the `compiler` targeting the `target` architecture. The artifacts
	/// created will also be linked into the sysroot directory.
	pub fn std<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
	println!("Building stage{} std artifacts ({} -> {})", compiler.stage,
	compiler.host, target);

	// Move compiler-rt into place as it'll be required by the compiler when
	// building the standard library to link the dylib of libstd
	let libdir = build.sysroot_libdir(compiler, target);
	let _ = fs::remove_dir_all(&libdir);
	t!(fs::create_dir_all(&libdir));
	copy(&build.compiler_rt_built.borrow()[target],
	&libdir.join(staticlib("compiler-rt", target)));

	// Some platforms have startup objects that may be required to produce the
	// libstd dynamic library, for example.
	build_startup_objects(build, target, &libdir);

	let out_dir = build.cargo_out(compiler, Mode::Libstd, target);
	build.clear_if_dirty(&out_dir, &build.compiler_path(compiler));
	let mut cargo = build.cargo(compiler, Mode::Libstd, target, "build");
	cargo.arg("--features").arg(build.std_features())
	.arg("--manifest-path")
	.arg(build.src.join("src/rustc/std_shim/Cargo.toml"));

	if let Some(target) = build.config.target_config.get(target) {
	if let Some(ref jemalloc) = target.jemalloc {
	cargo.env("JEMALLOC_OVERRIDE", jemalloc);
	}
	}
	if let Some(ref p) = build.config.musl_root {
	if target.contains("musl") {
	cargo.env("MUSL_ROOT", p);
	}
	}

	build.run(&mut cargo);
	std_link(build, target, compiler, compiler.host);
	}

	/// Link all libstd rlibs/dylibs into the sysroot location.
	///
	/// Links those artifacts generated in the given `stage` for `target` produced
	/// by `compiler` into `host`'s sysroot.
	pub fn std_link(build: &Build,
	target: &str,
	compiler: &Compiler,
	host: &str) {
	let target_compiler = Compiler::new(compiler.stage, host);
	let libdir = build.sysroot_libdir(&target_compiler, target);
	let out_dir = build.cargo_out(compiler, Mode::Libstd, target);

	// If we're linking one compiler host's output into another, then we weren't
	// called from the `std` method above. In that case we clean out what's
	// already there and then also link compiler-rt into place.
	if host != compiler.host {
	let _ = fs::remove_dir_all(&libdir);
	t!(fs::create_dir_all(&libdir));
	copy(&build.compiler_rt_built.borrow()[target],
	&libdir.join(staticlib("compiler-rt", target)));
	}
	add_to_sysroot(&out_dir, &libdir);

	if target.contains("musl") &&
	(target.contains("x86_64") \|\| target.contains("i686")) {
	copy_third_party_objects(build, target, &libdir);
	}
	}

	/// Copies the crt(1,i,n).o startup objects
	///
	/// Only required for musl targets that statically link to libc
	fn copy_third_party_objects(build: &Build, target: &str, into: &Path) {
	for &obj in &["crt1.o", "crti.o", "crtn.o"] {
	copy(&compiler_file(build.cc(target), obj), &into.join(obj));
	}
	}

	/// Build and prepare startup objects like rsbegin.o and rsend.o
	///
	/// These are primarily used on Windows right now for linking executables/dlls.
	/// They don't require any library support as they're just plain old object
	/// files, so we just use the nightly snapshot compiler to always build them (as
	/// no other compilers are guaranteed to be available).
	fn build_startup_objects(build: &Build, target: &str, into: &Path) {
	if !target.contains("pc-windows-gnu") {
	return
	}
	let compiler = Compiler::new(0, &build.config.build);
	let compiler = build.compiler_path(&compiler);

	for file in t!(fs::read_dir(build.src.join("src/rtstartup"))) {
	let file = t!(file);
	build.run(Command::new(&compiler)
	.arg("--emit=obj")
	.arg("--out-dir").arg(into)
	.arg(file.path()));
	}

	for obj in ["crt2.o", "dllcrt2.o"].iter() {
	copy(&compiler_file(build.cc(target), obj), &into.join(obj));
	}
	}

	/// Build libtest.
	///
	/// This will build libtest and supporting libraries for a particular stage of
	/// the build using the `compiler` targeting the `target` architecture. The
	/// artifacts created will also be linked into the sysroot directory.
	pub fn test<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
	println!("Building stage{} test artifacts ({} -> {})", compiler.stage,
	compiler.host, target);
	let out_dir = build.cargo_out(compiler, Mode::Libtest, target);
	build.clear_if_dirty(&out_dir, &libstd_shim(build, compiler, target));
	let mut cargo = build.cargo(compiler, Mode::Libtest, target, "build");
	cargo.arg("--manifest-path")
	.arg(build.src.join("src/rustc/test_shim/Cargo.toml"));
	build.run(&mut cargo);
	test_link(build, target, compiler, compiler.host);
	}

	/// Link all libtest rlibs/dylibs into the sysroot location.
	///
	/// Links those artifacts generated in the given `stage` for `target` produced
	/// by `compiler` into `host`'s sysroot.
	pub fn test_link(build: &Build,
	target: &str,
	compiler: &Compiler,
	host: &str) {
	let target_compiler = Compiler::new(compiler.stage, host);
	let libdir = build.sysroot_libdir(&target_compiler, target);
	let out_dir = build.cargo_out(compiler, Mode::Libtest, target);
	add_to_sysroot(&out_dir, &libdir);
	}

	/// Build the compiler.
	///
	/// This will build the compiler for a particular stage of the build using
	/// the `compiler` targeting the `target` architecture. The artifacts
	/// created will also be linked into the sysroot directory.
	pub fn rustc<'a>(build: &'a Build, target: &str, compiler: &Compiler<'a>) {
	println!("Building stage{} compiler artifacts ({} -> {})",
	compiler.stage, compiler.host, target);

	let out_dir = build.cargo_out(compiler, Mode::Librustc, target);
	build.clear_if_dirty(&out_dir, &libtest_shim(build, compiler, target));

	let mut cargo = build.cargo(compiler, Mode::Librustc, target, "build");
	cargo.arg("--features").arg(build.rustc_features())
	.arg("--manifest-path")
	.arg(build.src.join("src/rustc/Cargo.toml"));

	// Set some configuration variables picked up by build scripts and
	// the compiler alike
	cargo.env("CFG_RELEASE", &build.release)
	.env("CFG_RELEASE_CHANNEL", &build.config.channel)
	.env("CFG_VERSION", &build.version)
	.env("CFG_BOOTSTRAP_KEY", &build.bootstrap_key)
	.env("CFG_PREFIX", build.config.prefix.clone().unwrap_or(String::new()))
	.env("CFG_LIBDIR_RELATIVE", "lib");

	if let Some(ref ver_date) = build.ver_date {
	cargo.env("CFG_VER_DATE", ver_date);
	}
	if let Some(ref ver_hash) = build.ver_hash {
	cargo.env("CFG_VER_HASH", ver_hash);
	}
	if !build.unstable_features {
	cargo.env("CFG_DISABLE_UNSTABLE_FEATURES", "1");
	}
	cargo.env("LLVM_CONFIG", build.llvm_config(target));
	if build.config.llvm_static_stdcpp {
	cargo.env("LLVM_STATIC_STDCPP",
	compiler_file(build.cxx(target), "libstdc++.a"));
	}
	if let Some(ref s) = build.config.rustc_default_linker {
	cargo.env("CFG_DEFAULT_LINKER", s);
	}
	if let Some(ref s) = build.config.rustc_default_ar {
	cargo.env("CFG_DEFAULT_AR", s);
	}
	build.run(&mut cargo);

	rustc_link(build, target, compiler, compiler.host);
	}

	/// Link all librustc rlibs/dylibs into the sysroot location.
	///
	/// Links those artifacts generated in the given `stage` for `target` produced
	/// by `compiler` into `host`'s sysroot.
	pub fn rustc_link(build: &Build,
	target: &str,
	compiler: &Compiler,
	host: &str) {
	let target_compiler = Compiler::new(compiler.stage, host);
	let libdir = build.sysroot_libdir(&target_compiler, target);
	let out_dir = build.cargo_out(compiler, Mode::Librustc, target);
	add_to_sysroot(&out_dir, &libdir);
	}

	/// Cargo's output path for the standard library in a given stage, compiled
	/// by a particular compiler for the specified target.
	fn libstd_shim(build: &Build, compiler: &Compiler, target: &str) -> PathBuf {
	build.cargo_out(compiler, Mode::Libstd, target).join("libstd_shim.rlib")
	}

	/// Cargo's output path for libtest in a given stage, compiled by a particular
	/// compiler for the specified target.
	fn libtest_shim(build: &Build, compiler: &Compiler, target: &str) -> PathBuf {
	build.cargo_out(compiler, Mode::Libtest, target).join("libtest_shim.rlib")
	}

	fn compiler_file(compiler: &Path, file: &str) -> PathBuf {
	let out = output(Command::new(compiler)
	.arg(format!("-print-file-name={}", file)));
	PathBuf::from(out.trim())
	}

	/// Prepare a new compiler from the artifacts in `stage`
	///
	/// This will assemble a compiler in `build/$host/stage$stage`. The compiler
	/// must have been previously produced by the `stage - 1` build.config.build
	/// compiler.
	pub fn assemble_rustc(build: &Build, stage: u32, host: &str) {
	assert!(stage > 0, "the stage0 compiler isn't assembled, it's downloaded");
	// The compiler that we're assembling
	let target_compiler = Compiler::new(stage, host);

	// The compiler that compiled the compiler we're assembling
	let build_compiler = Compiler::new(stage - 1, &build.config.build);

	// Clear out old files
	let sysroot = build.sysroot(&target_compiler);
	let _ = fs::remove_dir_all(&sysroot);
	t!(fs::create_dir_all(&sysroot));

	// Link in all dylibs to the libdir
	let sysroot_libdir = sysroot.join(libdir(host));
	t!(fs::create_dir_all(&sysroot_libdir));
	let src_libdir = build.sysroot_libdir(&build_compiler, host);
	for f in t!(fs::read_dir(&src_libdir)).map(\|f\| t!(f)) {
	let filename = f.file_name().into_string().unwrap();
	if is_dylib(&filename) {
	copy(&f.path(), &sysroot_libdir.join(&filename));
	}
	}

	let out_dir = build.cargo_out(&build_compiler, Mode::Librustc, host);

	// Link the compiler binary itself into place
	let rustc = out_dir.join(exe("rustc", host));
	let bindir = sysroot.join("bin");
	t!(fs::create_dir_all(&bindir));
	let compiler = build.compiler_path(&Compiler::new(stage, host));
	let _ = fs::remove_file(&compiler);
	copy(&rustc, &compiler);

	// See if rustdoc exists to link it into place
	let rustdoc = exe("rustdoc", host);
	let rustdoc_src = out_dir.join(&rustdoc);
	let rustdoc_dst = bindir.join(&rustdoc);
	if fs::metadata(&rustdoc_src).is_ok() {
	let _ = fs::remove_file(&rustdoc_dst);
	copy(&rustdoc_src, &rustdoc_dst);
	}
	}

	/// Link some files into a rustc sysroot.
	///
	/// For a particular stage this will link all of the contents of `out_dir`
	/// into the sysroot of the `host` compiler, assuming the artifacts are
	/// compiled for the specified `target`.
	fn add_to_sysroot(out_dir: &Path, sysroot_dst: &Path) {
	// Collect the set of all files in the dependencies directory, keyed
	// off the name of the library. We assume everything is of the form
	// `foo-<hash>.{rlib,so,...}`, and there could be multiple different
	// `<hash>` values for the same name (of old builds).
	let mut map = HashMap::new();
	for file in t!(fs::read_dir(out_dir.join("deps"))).map(\|f\| t!(f)) {
	let filename = file.file_name().into_string().unwrap();

	// We're only interested in linking rlibs + dylibs, other things like
	// unit tests don't get linked in
	if !filename.ends_with(".rlib") &&
	!filename.ends_with(".lib") &&
	!is_dylib(&filename) {
	continue
	}
	let file = file.path();
	let dash = filename.find("-").unwrap();
	let key = (filename[..dash].to_string(),
	file.extension().unwrap().to_owned());
	map.entry(key).or_insert(Vec::new())
	.push(file.clone());
	}

	// For all hash values found, pick the most recent one to move into the
	// sysroot, that should be the one we just built.
	for (_, paths) in map {
	let (_, path) = paths.iter().map(\|path\| {
	(mtime(&path).seconds(), path)
	}).max().unwrap();
	copy(&path, &sysroot_dst.join(path.file_name().unwrap()));
	}
	}

	/// Build a tool in `src/tools`
	///
	/// This will build the specified tool with the specified `host` compiler in
	/// `stage` into the normal cargo output directory.
	pub fn tool(build: &Build, stage: u32, host: &str, tool: &str) {
	println!("Building stage{} tool {} ({})", stage, tool, host);

	let compiler = Compiler::new(stage, host);

	// FIXME: need to clear out previous tool and ideally deps, may require
	// isolating output directories or require a pseudo shim step to
	// clear out all the info.
	//
	// Maybe when libstd is compiled it should clear out the rustc of the
	// corresponding stage?
	// let out_dir = build.cargo_out(stage, &host, Mode::Librustc, target);
	// build.clear_if_dirty(&out_dir, &libstd_shim(build, stage, &host, target));

	let mut cargo = build.cargo(&compiler, Mode::Tool, host, "build");
	cargo.arg("--manifest-path")
	.arg(build.src.join(format!("src/tools/{}/Cargo.toml", tool)));
	build.run(&mut cargo);
	}