build/build-clang/build-clang.py
author Nathan Froyd <froydnj@gmail.com>
Tue, 12 Mar 2019 00:21:20 +0000
changeset 521812 c64bfaad8a2f0098be09b646fd4ce4b582f12056
parent 511589 24e1359b53ca15beedd2142844bc237ea4f19fc6
child 521813 675f73d41eb4467f106f5c0a60043f5ec34c0ead
permissions -rwxr-xr-x
Bug 1451104 - part 2 - force clang to always pick up its local GCC headers and libraries; r=glandium We want our clang bootstrap to use the GCC headers we're building with, not whatever sysroot it happens to find on the server we're building on. The -gcc-toolchain argument we specify when building clang will also be picked up by llvm-config, so we need to strip it out when building the plugin. Otherwise, we will get peculiar failures about not being able to find C++ header files. Depends on D22879 Differential Revision: https://phabricator.services.mozilla.com/D22880

#!/usr/bin/python2.7
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

import os
import os.path
import shutil
import subprocess
import platform
import json
import argparse
import fnmatch
import glob
import errno
import re
from contextlib import contextmanager
import sys
import which
from distutils.dir_util import copy_tree


def symlink(source, link_name):
    os_symlink = getattr(os, "symlink", None)
    if callable(os_symlink):
        os_symlink(source, link_name)
    else:
        if os.path.isdir(source):
            # Fall back to copying the directory :(
            copy_tree(source, link_name)


def check_run(args):
    print >> sys.stderr, ' '.join(args)
    r = subprocess.call(args)
    assert r == 0


def run_in(path, args):
    d = os.getcwd()
    print >> sys.stderr, 'cd "%s"' % path
    os.chdir(path)
    check_run(args)
    print >> sys.stderr, 'cd "%s"' % d
    os.chdir(d)


def patch(patch, srcdir):
    patch = os.path.realpath(patch)
    check_run(['patch', '-d', srcdir, '-p1', '-i', patch, '--fuzz=0',
               '-s'])


def import_clang_tidy(source_dir):
    clang_plugin_path = os.path.join(os.path.dirname(sys.argv[0]),
                                     '..', 'clang-plugin')
    clang_tidy_path = os.path.join(source_dir,
                                   'tools/clang/tools/extra/clang-tidy')
    sys.path.append(clang_plugin_path)
    from import_mozilla_checks import do_import
    do_import(clang_plugin_path, clang_tidy_path)


def build_package(package_build_dir, cmake_args):
    if not os.path.exists(package_build_dir):
        os.mkdir(package_build_dir)
    # If CMake has already been run, it may have been run with different
    # arguments, so we need to re-run it.  Make sure the cached copy of the
    # previous CMake run is cleared before running it again.
    if os.path.exists(package_build_dir + "/CMakeCache.txt"):
        os.remove(package_build_dir + "/CMakeCache.txt")
    if os.path.exists(package_build_dir + "/CMakeFiles"):
        shutil.rmtree(package_build_dir + "/CMakeFiles")

    run_in(package_build_dir, ["cmake"] + cmake_args)
    run_in(package_build_dir, ["ninja", "install"])


@contextmanager
def updated_env(env):
    old_env = os.environ.copy()
    os.environ.update(env)
    yield
    os.environ.clear()
    os.environ.update(old_env)


def build_tar_package(tar, name, base, directory):
    name = os.path.realpath(name)
    # On Windows, we have to convert this into an msys path so that tar can
    # understand it.
    if is_windows():
        name = name.replace('\\', '/')

        def f(match):
            return '/' + match.group(1).lower()
        name = re.sub(r'^([A-Za-z]):', f, name)
    run_in(base, [tar,
                  "-c",
                  "-%s" % ("J" if ".xz" in name else "j"),
                  "-f",
                  name, directory])


def mkdir_p(path):
    try:
        os.makedirs(path)
    except OSError as e:
        if e.errno != errno.EEXIST or not os.path.isdir(path):
            raise


def delete(path):
    if os.path.isdir(path):
        shutil.rmtree(path)
    else:
        try:
            os.unlink(path)
        except Exception:
            pass


def install_libgcc(gcc_dir, clang_dir):
    out = subprocess.check_output([os.path.join(gcc_dir, "bin", "gcc"),
                                   '-print-libgcc-file-name'])

    libgcc_dir = os.path.dirname(out.rstrip())
    clang_lib_dir = os.path.join(clang_dir, "lib", "gcc",
                                 "x86_64-unknown-linux-gnu",
                                 os.path.basename(libgcc_dir))
    mkdir_p(clang_lib_dir)
    copy_tree(libgcc_dir, clang_lib_dir)
    libgcc_dir = os.path.join(gcc_dir, "lib64")
    clang_lib_dir = os.path.join(clang_dir, "lib")
    copy_tree(libgcc_dir, clang_lib_dir)
    libgcc_dir = os.path.join(gcc_dir, "lib32")
    clang_lib_dir = os.path.join(clang_dir, "lib32")
    copy_tree(libgcc_dir, clang_lib_dir)
    include_dir = os.path.join(gcc_dir, "include")
    clang_include_dir = os.path.join(clang_dir, "include")
    copy_tree(include_dir, clang_include_dir)


def install_import_library(build_dir, clang_dir):
    shutil.copy2(os.path.join(build_dir, "lib", "clang.lib"),
                 os.path.join(clang_dir, "lib"))


def install_asan_symbols(build_dir, clang_dir):
    lib_path_pattern = os.path.join("lib", "clang", "*.*.*", "lib", "windows")
    src_path = glob.glob(os.path.join(build_dir, lib_path_pattern,
                                      "clang_rt.asan_dynamic-*.pdb"))
    dst_path = glob.glob(os.path.join(clang_dir, lib_path_pattern))

    if len(src_path) != 1:
        raise Exception("Source path pattern did not resolve uniquely")

    if len(src_path) != 1:
        raise Exception("Destination path pattern did not resolve uniquely")

    shutil.copy2(src_path[0], dst_path[0])


def svn_co(source_dir, url, directory, revision):
    run_in(source_dir, ["svn", "co", "-q", "-r", revision, url, directory])


def svn_update(directory, revision):
    run_in(directory, ["svn", "revert", "-q", "-R", "."])
    run_in(directory, ["svn", "update", "-q", "-r", revision])


def is_darwin():
    return platform.system() == "Darwin"


def is_linux():
    return platform.system() == "Linux"


def is_windows():
    return platform.system() == "Windows"


def build_one_stage(cc, cxx, asm, ld, ar, ranlib, libtool,
                    src_dir, stage_dir, package_name, build_libcxx,
                    osx_cross_compile, build_type, assertions,
                    python_path, gcc_dir, libcxx_include_dir,
                    is_final_stage=False, android_targets=None):
    if not os.path.exists(stage_dir):
        os.mkdir(stage_dir)

    build_dir = stage_dir + "/build"
    inst_dir = stage_dir + "/" + package_name

    # cmake doesn't deal well with backslashes in paths.
    def slashify_path(path):
        return path.replace('\\', '/')

    def cmake_base_args(cc, cxx, asm, ld, ar, ranlib, libtool, inst_dir):
        cmake_args = [
            "-GNinja",
            "-DCMAKE_C_COMPILER=%s" % slashify_path(cc[0]),
            "-DCMAKE_CXX_COMPILER=%s" % slashify_path(cxx[0]),
            "-DCMAKE_ASM_COMPILER=%s" % slashify_path(asm[0]),
            "-DCMAKE_LINKER=%s" % slashify_path(ld[0]),
            "-DCMAKE_AR=%s" % slashify_path(ar),
            "-DCMAKE_C_FLAGS=%s" % ' '.join(cc[1:]),
            "-DCMAKE_CXX_FLAGS=%s" % ' '.join(cxx[1:]),
            "-DCMAKE_ASM_FLAGS=%s" % ' '.join(asm[1:]),
            "-DCMAKE_EXE_LINKER_FLAGS=%s" % ' '.join(ld[1:]),
            "-DCMAKE_SHARED_LINKER_FLAGS=%s" % ' '.join(ld[1:]),
            "-DCMAKE_BUILD_TYPE=%s" % build_type,
            "-DCMAKE_INSTALL_PREFIX=%s" % inst_dir,
            "-DLLVM_TARGETS_TO_BUILD=X86;ARM;AArch64",
            "-DLLVM_ENABLE_ASSERTIONS=%s" % ("ON" if assertions else "OFF"),
            "-DPYTHON_EXECUTABLE=%s" % slashify_path(python_path),
            "-DLLVM_TOOL_LIBCXX_BUILD=%s" % ("ON" if build_libcxx else "OFF"),
            "-DLIBCXX_LIBCPPABI_VERSION=\"\"",
        ]
        if is_linux():
            cmake_args += ["-DLLVM_BINUTILS_INCDIR=%s/include" % gcc_dir]
        if is_windows():
            cmake_args.insert(-1, "-DLLVM_EXPORT_SYMBOLS_FOR_PLUGINS=ON")
            cmake_args.insert(-1, "-DLLVM_USE_CRT_RELEASE=MT")
        else:
            # libllvm as a shared library is not supported on Windows
            cmake_args += ["-DLLVM_LINK_LLVM_DYLIB=ON"]
        if ranlib is not None:
            cmake_args += ["-DCMAKE_RANLIB=%s" % slashify_path(ranlib)]
        if libtool is not None:
            cmake_args += ["-DCMAKE_LIBTOOL=%s" % slashify_path(libtool)]
        if osx_cross_compile:
            cmake_args += [
                "-DCMAKE_SYSTEM_NAME=Darwin",
                "-DCMAKE_SYSTEM_VERSION=10.10",
                "-DLLVM_ENABLE_THREADS=OFF",
                # Xray requires a OSX 10.12 SDK (https://bugs.llvm.org/show_bug.cgi?id=38959)
                "-DCOMPILER_RT_BUILD_XRAY=OFF",
                "-DLIBCXXABI_LIBCXX_INCLUDES=%s" % libcxx_include_dir,
                "-DCMAKE_OSX_SYSROOT=%s" % slashify_path(os.getenv("CROSS_SYSROOT")),
                "-DCMAKE_FIND_ROOT_PATH=%s" % slashify_path(os.getenv("CROSS_CCTOOLS_PATH")), # noqa
                "-DCMAKE_FIND_ROOT_PATH_MODE_PROGRAM=NEVER",
                "-DCMAKE_FIND_ROOT_PATH_MODE_LIBRARY=ONLY",
                "-DCMAKE_FIND_ROOT_PATH_MODE_INCLUDE=ONLY",
                "-DCMAKE_MACOSX_RPATH=ON",
                "-DCMAKE_OSX_ARCHITECTURES=x86_64",
                "-DDARWIN_osx_ARCHS=x86_64",
                "-DDARWIN_osx_SYSROOT=%s" % slashify_path(os.getenv("CROSS_SYSROOT")),
                "-DLLVM_DEFAULT_TARGET_TRIPLE=x86_64-darwin11"
            ]
        return cmake_args

    cmake_args = []

    if is_final_stage and android_targets:
        cmake_args += [
            "-DCOMPILER_RT_DEFAULT_TARGET_TRIPLE=%s" % android_targets.keys()[0],
            "-DLLVM_BUILTIN_TARGETS=%s" % ";".join(android_targets),
            "-DLLVM_DEFAULT_TARGET_TRIPLE=%s" % android_targets.keys()[0],
            "-DLLVM_ENABLE_LIBCXX=ON",
            "-DLLVM_LIBDIR_SUFFIX=64",
            "-DLLVM_RUNTIME_TARGETS=%s" % ";".join(android_targets),
        ]

        android_link_flags = "-fuse-ld=lld"

        for target, cfg in android_targets.iteritems():
            sysroot_dir = cfg["ndk_sysroot"]
            android_gcc_dir = cfg["ndk_toolchain"]
            android_include_dirs = cfg["ndk_includes"]
            api_level = cfg["api_level"]

            android_flags = ["-isystem %s" % d for d in android_include_dirs]
            android_flags += ["--gcc-toolchain=%s" % android_gcc_dir]
            android_flags += ["-D__ANDROID_API__=%s" % api_level]
            rt_c_flags = " ".join(android_flags + cc[1:])
            rt_cxx_flags = " ".join(android_flags + cxx[1:])
            rt_asm_flags = " ".join(android_flags + asm[1:])

            cmake_args += [
                "-DBUILTINS_%s_ANDROID=1" % target,
                "-DBUILTINS_%s_CMAKE_ASM_FLAGS=%s" % (target, rt_asm_flags),
                "-DBUILTINS_%s_CMAKE_CXX_FLAGS=%s" % (target, rt_cxx_flags),
                "-DBUILTINS_%s_CMAKE_C_FLAGS=%s" % (target, rt_c_flags),
                "-DBUILTINS_%s_CMAKE_EXE_LINKER_FLAGS=%s" % (target, android_link_flags),
                "-DBUILTINS_%s_CMAKE_SHARED_LINKER_FLAGS=%s" % (target, android_link_flags),
                "-DBUILTINS_%s_CMAKE_SYSROOT=%s" % (target, sysroot_dir),
                "-DRUNTIMES_%s_CMAKE_ASM_FLAGS=%s" % (target, rt_asm_flags),
                "-DRUNTIMES_%s_CMAKE_CXX_FLAGS=%s" % (target, rt_cxx_flags),
                "-DRUNTIMES_%s_CMAKE_C_FLAGS=%s" % (target, rt_c_flags),
                "-DRUNTIMES_%s_CMAKE_EXE_LINKER_FLAGS=%s" % (target, android_link_flags),
                "-DRUNTIMES_%s_CMAKE_SHARED_LINKER_FLAGS=%s" % (target, android_link_flags),
                "-DRUNTIMES_%s_CMAKE_SYSROOT=%s" % (target, sysroot_dir),
                "-DRUNTIMES_%s_COMPILER_RT_BUILD_PROFILE=ON" % target,
                "-DRUNTIMES_%s_COMPILER_RT_BUILD_SANITIZERS=OFF" % target,
                "-DRUNTIMES_%s_COMPILER_RT_BUILD_LIBFUZZER=OFF" % target,
                "-DRUNTIMES_%s_COMPILER_RT_INCLUDE_TESTS=OFF" % target,
                "-DRUNTIMES_%s_LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF" % target,
                "-DRUNTIMES_%s_LLVM_INCLUDE_TESTS=OFF" % target,
                "-DRUNTIMES_%s_ANDROID_NATIVE_API_LEVEL=%s" % (target, api_level),
            ]

    cmake_args += cmake_base_args(
        cc, cxx, asm, ld, ar, ranlib, libtool, inst_dir)
    cmake_args += [
        src_dir
    ]
    build_package(build_dir, cmake_args)

    if is_linux():
        install_libgcc(gcc_dir, inst_dir)
    # For some reasons the import library clang.lib of clang.exe is not
    # installed, so we copy it by ourselves.
    if is_windows():
        # The compiler-rt cmake scripts don't allow to build it for multiple
        # targets at once on Windows, so manually build the 32-bits compiler-rt
        # during the final stage.
        build_32_bit = False
        if is_final_stage:
            # Only build the 32-bits compiler-rt when we originally built for
            # 64-bits, which we detect through the contents of the LIB
            # environment variable, which we also adjust for a 32-bits build
            # at the same time.
            old_lib = os.environ['LIB']
            new_lib = []
            for l in old_lib.split(os.pathsep):
                if l.endswith('x64'):
                    l = l[:-3] + 'x86'
                    build_32_bit = True
                elif l.endswith('amd64'):
                    l = l[:-5]
                    build_32_bit = True
                new_lib.append(l)
        if build_32_bit:
            os.environ['LIB'] = os.pathsep.join(new_lib)
            compiler_rt_build_dir = stage_dir + '/compiler-rt'
            compiler_rt_inst_dir = inst_dir + '/lib/clang/'
            subdirs = os.listdir(compiler_rt_inst_dir)
            assert len(subdirs) == 1
            compiler_rt_inst_dir += subdirs[0]
            cmake_args = cmake_base_args(
                [os.path.join(inst_dir, 'bin', 'clang-cl.exe'), '-m32'] + cc[1:],
                [os.path.join(inst_dir, 'bin', 'clang-cl.exe'), '-m32'] + cxx[1:],
                [os.path.join(inst_dir, 'bin', 'clang-cl.exe'), '-m32'] + asm[1:],
                ld, ar, ranlib, libtool, compiler_rt_inst_dir)
            cmake_args += [
                '-DLLVM_CONFIG_PATH=%s' % slashify_path(
                    os.path.join(inst_dir, 'bin', 'llvm-config')),
                os.path.join(src_dir, 'projects', 'compiler-rt'),
            ]
            build_package(compiler_rt_build_dir, cmake_args)
            os.environ['LIB'] = old_lib
        install_import_library(build_dir, inst_dir)
        install_asan_symbols(build_dir, inst_dir)


# Return the absolute path of a build tool.  We first look to see if the
# variable is defined in the config file, and if so we make sure it's an
# absolute path to an existing tool, otherwise we look for a program in
# $PATH named "key".
#
# This expects the name of the key in the config file to match the name of
# the tool in the default toolchain on the system (for example, "ld" on Unix
# and "link" on Windows).
def get_tool(config, key):
    f = None
    if key in config:
        f = config[key]
        if os.path.isabs(f):
            if not os.path.exists(f):
                raise ValueError("%s must point to an existing path" % key)
            return f

    # Assume that we have the name of some program that should be on PATH.
    try:
        return which.which(f) if f else which.which(key)
    except which.WhichError:
        raise ValueError("%s not found on PATH" % f)


# This function is intended to be called on the final build directory when
# building clang-tidy. Also clang-format binaries are included that can be used
# in conjunction with clang-tidy.
# Its job is to remove all of the files which won't be used for clang-tidy or
# clang-format to reduce the download size.  Currently when this function
# finishes its job, it will leave final_dir with a layout like this:
#
# clang/
#   bin/
#     clang-apply-replacements
#     clang-format
#     clang-tidy
#   include/
#     * (nothing will be deleted here)
#   lib/
#     clang/
#       4.0.0/
#         include/
#           * (nothing will be deleted here)
#   share/
#     clang/
#       clang-format-diff.py
#       clang-tidy-diff.py
#       run-clang-tidy.py
def prune_final_dir_for_clang_tidy(final_dir, osx_cross_compile):
    # Make sure we only have what we expect.
    dirs = ("bin", "include", "lib", "lib32", "libexec", "msbuild-bin", "share", "tools")
    for f in glob.glob("%s/*" % final_dir):
        if os.path.basename(f) not in dirs:
            raise Exception("Found unknown file %s in the final directory" % f)
        if not os.path.isdir(f):
            raise Exception("Expected %s to be a directory" % f)

    # In bin/, only keep clang-tidy and clang-apply-replacements. The last one
    # is used to auto-fix some of the issues detected by clang-tidy.
    re_clang_tidy = re.compile(
        r"^clang-(apply-replacements|format|tidy)(\.exe)?$", re.I)
    for f in glob.glob("%s/bin/*" % final_dir):
        if re_clang_tidy.search(os.path.basename(f)) is None:
            delete(f)

    # Keep include/ intact.

    # In lib/, only keep lib/clang/N.M.O/include and the LLVM shared library.
    re_ver_num = re.compile(r"^\d+\.\d+\.\d+$", re.I)
    for f in glob.glob("%s/lib/*" % final_dir):
        name = os.path.basename(f)
        if name == "clang":
            continue
        if osx_cross_compile and name == 'libLLVM.dylib':
            continue
        if is_linux() and fnmatch.fnmatch(name, 'libLLVM*.so'):
            continue
        delete(f)
    for f in glob.glob("%s/lib/clang/*" % final_dir):
        if re_ver_num.search(os.path.basename(f)) is None:
            delete(f)
    for f in glob.glob("%s/lib/clang/*/*" % final_dir):
        if os.path.basename(f) != "include":
            delete(f)

    # Completely remove libexec/, msbuilld-bin and tools, if it exists.
    shutil.rmtree(os.path.join(final_dir, "libexec"))
    for d in ("msbuild-bin", "tools"):
        d = os.path.join(final_dir, d)
        if os.path.exists(d):
            shutil.rmtree(d)

    # In share/, only keep share/clang/*tidy*
    re_clang_tidy = re.compile(r"format|tidy", re.I)
    for f in glob.glob("%s/share/*" % final_dir):
        if os.path.basename(f) != "clang":
            delete(f)
    for f in glob.glob("%s/share/clang/*" % final_dir):
        if re_clang_tidy.search(os.path.basename(f)) is None:
            delete(f)


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('-c', '--config', required=True,
                        type=argparse.FileType('r'),
                        help="Clang configuration file")
    parser.add_argument('-b', '--base-dir', required=False,
                        help="Base directory for code and build artifacts")
    parser.add_argument('--clean', required=False,
                        action='store_true',
                        help="Clean the build directory")
    parser.add_argument('--skip-tar', required=False,
                        action='store_true',
                        help="Skip tar packaging stage")
    parser.add_argument('--skip-checkout', required=False,
                        action='store_true',
                        help="Do not checkout/revert source")

    args = parser.parse_args()

    # The directories end up in the debug info, so the easy way of getting
    # a reproducible build is to run it in a know absolute directory.
    # We use a directory that is registered as a volume in the Docker image.

    if args.base_dir:
        base_dir = args.base_dir
    elif os.environ.get('MOZ_AUTOMATION') and not is_windows():
        base_dir = "/builds/worker/workspace/moz-toolchain"
    else:
        # Handles both the Windows automation case and the local build case
        # TODO: Because Windows taskcluster builds are run with distinct
        # user IDs for each job, we can't store things in some globally
        # accessible directory: one job will run, checkout LLVM to that
        # directory, and then if another job runs, the new user won't be
        # able to access the previously-checked out code--or be able to
        # delete it.  So on Windows, we build in the task-specific home
        # directory; we will eventually add -fdebug-prefix-map options
        # to the LLVM build to bring back reproducibility.
        base_dir = os.path.join(os.getcwd(), 'build-clang')

    source_dir = base_dir + "/src"
    build_dir = base_dir + "/build"

    if not os.path.exists(base_dir):
        os.makedirs(base_dir)
    elif os.listdir(base_dir) and not os.path.exists(os.path.join(base_dir, '.build-clang')):
        raise ValueError("Base directory %s exists and is not a build-clang directory. "
                         "Supply a non-existent or empty directory with --base-dir" % base_dir)
    open(os.path.join(base_dir, '.build-clang'), 'a').close()

    if args.clean:
        shutil.rmtree(build_dir)
        os.sys.exit(0)

    llvm_source_dir = source_dir + "/llvm"
    clang_source_dir = source_dir + "/clang"
    extra_source_dir = source_dir + "/extra"
    lld_source_dir = source_dir + "/lld"
    compiler_rt_source_dir = source_dir + "/compiler-rt"
    libcxx_source_dir = source_dir + "/libcxx"
    libcxxabi_source_dir = source_dir + "/libcxxabi"

    if is_darwin():
        os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.7'

    exe_ext = ""
    if is_windows():
        exe_ext = ".exe"

    cc_name = "clang"
    cxx_name = "clang++"
    if is_windows():
        cc_name = "clang-cl"
        cxx_name = "clang-cl"

    config = json.load(args.config)

    llvm_revision = config["llvm_revision"]
    llvm_repo = config["llvm_repo"]
    clang_repo = config["clang_repo"]
    extra_repo = config.get("extra_repo")
    lld_repo = config.get("lld_repo")
    # On some packages we don't use compiler_repo
    compiler_repo = config.get("compiler_repo")
    libcxx_repo = config["libcxx_repo"]
    libcxxabi_repo = config.get("libcxxabi_repo")
    stages = 3
    if "stages" in config:
        stages = int(config["stages"])
        if stages not in (1, 2, 3):
            raise ValueError("We only know how to build 1, 2, or 3 stages")
    build_type = "Release"
    if "build_type" in config:
        build_type = config["build_type"]
        if build_type not in ("Release", "Debug", "RelWithDebInfo", "MinSizeRel"):
            raise ValueError("We only know how to do Release, Debug, RelWithDebInfo or "
                             "MinSizeRel builds")
    build_libcxx = False
    if "build_libcxx" in config:
        build_libcxx = config["build_libcxx"]
        if build_libcxx not in (True, False):
            raise ValueError("Only boolean values are accepted for build_libcxx.")
    build_clang_tidy = False
    if "build_clang_tidy" in config:
        build_clang_tidy = config["build_clang_tidy"]
        if build_clang_tidy not in (True, False):
            raise ValueError("Only boolean values are accepted for build_clang_tidy.")
    osx_cross_compile = False
    if "osx_cross_compile" in config:
        osx_cross_compile = config["osx_cross_compile"]
        if osx_cross_compile not in (True, False):
            raise ValueError("Only boolean values are accepted for osx_cross_compile.")
        if osx_cross_compile and not is_linux():
            raise ValueError("osx_cross_compile can only be used on Linux.")
    assertions = False
    if "assertions" in config:
        assertions = config["assertions"]
        if assertions not in (True, False):
            raise ValueError("Only boolean values are accepted for assertions.")
    python_path = None
    if "python_path" not in config:
        raise ValueError("Config file needs to set python_path")
    python_path = config["python_path"]
    gcc_dir = None
    if "gcc_dir" in config:
        gcc_dir = config["gcc_dir"]
        if not os.path.exists(gcc_dir):
            raise ValueError("gcc_dir must point to an existing path")
    ndk_dir = None
    android_targets = None
    if "android_targets" in config:
        android_targets = config["android_targets"]
        for attr in ("ndk_toolchain", "ndk_sysroot", "ndk_includes", "api_level"):
            for target, cfg in android_targets.iteritems():
                if attr not in cfg:
                    raise ValueError("must specify '%s' as a key for android target: %s" %
                                     (attr, target))
    if is_linux() and gcc_dir is None:
        raise ValueError("Config file needs to set gcc_dir")
    cc = get_tool(config, "cc")
    cxx = get_tool(config, "cxx")
    asm = get_tool(config, "ml" if is_windows() else "as")
    ld = get_tool(config, "link" if is_windows() else "ld")
    ar = get_tool(config, "lib" if is_windows() else "ar")
    ranlib = None if is_windows() else get_tool(config, "ranlib")
    libtool = None
    if "libtool" in config:
        libtool = get_tool(config, "libtool")

    if not os.path.exists(source_dir):
        os.makedirs(source_dir)

    def checkout_or_update(repo, checkout_dir):
        if os.path.exists(checkout_dir):
            svn_update(checkout_dir, llvm_revision)
        else:
            svn_co(source_dir, repo, checkout_dir, llvm_revision)

    if not args.skip_checkout:
        checkout_or_update(llvm_repo, llvm_source_dir)
        checkout_or_update(clang_repo, clang_source_dir)
        if compiler_repo is not None:
            checkout_or_update(compiler_repo, compiler_rt_source_dir)
        checkout_or_update(libcxx_repo, libcxx_source_dir)
        if lld_repo:
            checkout_or_update(lld_repo, lld_source_dir)
        if libcxxabi_repo:
            checkout_or_update(libcxxabi_repo, libcxxabi_source_dir)
        if extra_repo:
            checkout_or_update(extra_repo, extra_source_dir)
        for p in config.get("patches", []):
            patch(p, source_dir)

    compiler_rt_source_link = llvm_source_dir + "/projects/compiler-rt"

    symlinks = [(clang_source_dir,
                 llvm_source_dir + "/tools/clang"),
                (extra_source_dir,
                 llvm_source_dir + "/tools/clang/tools/extra"),
                (lld_source_dir,
                 llvm_source_dir + "/tools/lld"),
                (compiler_rt_source_dir, compiler_rt_source_link),
                (libcxx_source_dir,
                 llvm_source_dir + "/projects/libcxx"),
                (libcxxabi_source_dir,
                 llvm_source_dir + "/projects/libcxxabi")]
    for l in symlinks:
        # On Windows, we have to re-copy the whole directory every time.
        if not is_windows() and os.path.islink(l[1]):
            continue
        delete(l[1])
        if os.path.exists(l[0]):
            symlink(l[0], l[1])

    package_name = "clang"
    if build_clang_tidy:
        package_name = "clang-tidy"
        import_clang_tidy(llvm_source_dir)

    if not os.path.exists(build_dir):
        os.makedirs(build_dir)

    libcxx_include_dir = os.path.join(llvm_source_dir, "projects",
                                      "libcxx", "include")

    stage1_dir = build_dir + '/stage1'
    stage1_inst_dir = stage1_dir + '/' + package_name

    final_stage_dir = stage1_dir

    if is_darwin():
        extra_cflags = []
        extra_cxxflags = ["-stdlib=libc++"]
        extra_cflags2 = []
        extra_cxxflags2 = ["-stdlib=libc++"]
        extra_asmflags = []
        extra_ldflags = []
    elif is_linux():
        extra_cflags = []
        extra_cxxflags = []
        # When building stage2 and stage3, we want the newly-built clang to pick
        # up whatever headers were installed from the gcc we used to build stage1,
        # always, rather than the system headers.  Providing -gcc-toolchain
        # encourages clang to do that.
        extra_cflags2 = ["-fPIC", '-gcc-toolchain', stage1_inst_dir]
        # Silence clang's warnings about arguments not being used in compilation.
        extra_cxxflags2 = ["-fPIC", '-Qunused-arguments', '-gcc-toolchain', stage1_inst_dir]
        extra_asmflags = []
        # Avoid libLLVM internal function calls going through the PLT.
        extra_ldflags = ['-Wl,-Bsymbolic-functions']

        if 'LD_LIBRARY_PATH' in os.environ:
            os.environ['LD_LIBRARY_PATH'] = ('%s/lib64/:%s' %
                                             (gcc_dir, os.environ['LD_LIBRARY_PATH']))
        else:
            os.environ['LD_LIBRARY_PATH'] = '%s/lib64/' % gcc_dir
    elif is_windows():
        extra_cflags = []
        extra_cxxflags = []
        # clang-cl would like to figure out what it's supposed to be emulating
        # by looking at an MSVC install, but we don't really have that here.
        # Force things on.
        extra_cflags2 = []
        extra_cxxflags2 = ['-fms-compatibility-version=19.13.26128', '-Xclang', '-std=c++14']
        extra_asmflags = []
        extra_ldflags = []

    if osx_cross_compile:
        # undo the damage done in the is_linux() block above, and also simulate
        # the is_darwin() block above.
        extra_cflags = []
        extra_cxxflags = ["-stdlib=libc++"]
        extra_cxxflags2 = ["-stdlib=libc++"]

        extra_flags = ["-target", "x86_64-darwin11", "-mlinker-version=137",
                       "-B", "%s/bin" % os.getenv("CROSS_CCTOOLS_PATH"),
                       "-isysroot", os.getenv("CROSS_SYSROOT"),
                       # technically the sysroot flag there should be enough to deduce this,
                       # but clang needs some help to figure this out.
                       "-I%s/usr/include" % os.getenv("CROSS_SYSROOT"),
                       "-iframework", "%s/System/Library/Frameworks" % os.getenv("CROSS_SYSROOT")]
        extra_cflags += extra_flags
        extra_cxxflags += extra_flags
        extra_cflags2 += extra_flags
        extra_cxxflags2 += extra_flags
        extra_asmflags += extra_flags
        extra_ldflags = ["-Wl,-syslibroot,%s" % os.getenv("CROSS_SYSROOT"),
                         "-Wl,-dead_strip"]

    build_one_stage(
        [cc] + extra_cflags,
        [cxx] + extra_cxxflags,
        [asm] + extra_asmflags,
        [ld] + extra_ldflags,
        ar, ranlib, libtool,
        llvm_source_dir, stage1_dir, package_name, build_libcxx, osx_cross_compile,
        build_type, assertions, python_path, gcc_dir, libcxx_include_dir)

    if android_targets:
        # Linking compiler-rt under "runtimes" activates LLVM_RUNTIME_TARGETS
        # and related arguments.
        symlink(compiler_rt_source_dir, llvm_source_dir + "/runtimes/compiler-rt")
        try:
            os.unlink(compiler_rt_source_link)
        except Exception:
            pass

    if stages > 1:
        stage2_dir = build_dir + '/stage2'
        stage2_inst_dir = stage2_dir + '/' + package_name
        final_stage_dir = stage2_dir
        build_one_stage(
            [stage1_inst_dir + "/bin/%s%s" %
                (cc_name, exe_ext)] + extra_cflags2,
            [stage1_inst_dir + "/bin/%s%s" %
                (cxx_name, exe_ext)] + extra_cxxflags2,
            [stage1_inst_dir + "/bin/%s%s" %
                (cc_name, exe_ext)] + extra_asmflags,
            [ld] + extra_ldflags,
            ar, ranlib, libtool,
            llvm_source_dir, stage2_dir, package_name, build_libcxx, osx_cross_compile,
            build_type, assertions, python_path, gcc_dir, libcxx_include_dir,
            is_final_stage=(stages == 2), android_targets=android_targets)

    if stages > 2:
        stage3_dir = build_dir + '/stage3'
        final_stage_dir = stage3_dir
        build_one_stage(
            [stage2_inst_dir + "/bin/%s%s" %
                (cc_name, exe_ext)] + extra_cflags2,
            [stage2_inst_dir + "/bin/%s%s" %
                (cxx_name, exe_ext)] + extra_cxxflags2,
            [stage2_inst_dir + "/bin/%s%s" %
                (cc_name, exe_ext)] + extra_asmflags,
            [ld] + extra_ldflags,
            ar, ranlib, libtool,
            llvm_source_dir, stage3_dir, package_name, build_libcxx, osx_cross_compile,
            build_type, assertions, python_path, gcc_dir, libcxx_include_dir,
            (stages == 3))

    if build_clang_tidy:
        prune_final_dir_for_clang_tidy(os.path.join(final_stage_dir, package_name),
                                       osx_cross_compile)

    if not args.skip_tar:
        ext = "bz2" if is_darwin() or is_windows() else "xz"
        build_tar_package("tar", "%s.tar.%s" % (package_name, ext), final_stage_dir, package_name)