diff --git a/scripts/build-many-glibcs.py b/scripts/build-many-glibcs.py
new file mode 100755
index 0000000..d4632cb
--- /dev/null
+++ b/scripts/build-many-glibcs.py
@@ -0,0 +1,1132 @@
+#!/usr/bin/python3
+# Build many configurations of glibc.
+# Copyright (C) 2016 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+"""Build many configurations of glibc.
+
+This script takes as arguments a directory name (containing a src
+subdirectory with sources of the relevant toolchain components) and a
+description of what to do: 'checkout', to check out sources into that
+directory, 'host-libraries', to build libraries required by the
+toolchain, 'compilers', to build cross-compilers for various
+configurations, or 'glibcs', to build glibc for various configurations
+and run the compilation parts of the testsuite.  Subsequent arguments
+name the versions of components to check out (<component>-<version),
+for 'checkout', or, for actions other than 'checkout', name
+configurations for which compilers or glibc are to be built.
+"""
+
+import argparse
+import os
+import os.path
+import re
+import shutil
+import stat
+import subprocess
+import sys
+import urllib.request
+
+
+class Context:
+
+    """The global state associated with builds in a given directory."""
+
+    def __init__(self, topdir, parallelism, keep, action):
+        """Initialize the context."""
+        self.topdir = topdir
+        self.parallelism = parallelism
+        self.keep = keep
+        self.srcdir = os.path.join(topdir, 'src')
+        self.installdir = os.path.join(topdir, 'install')
+        self.host_libraries_installdir = os.path.join(self.installdir,
+                                                      'host-libraries')
+        self.builddir = os.path.join(topdir, 'build')
+        self.logsdir = os.path.join(topdir, 'logs')
+        self.makefile = os.path.join(self.builddir, 'Makefile')
+        self.wrapper = os.path.join(self.builddir, 'wrapper')
+        self.save_logs = os.path.join(self.builddir, 'save-logs')
+        if action != 'checkout':
+            self.build_triplet = self.get_build_triplet()
+            self.glibc_version = self.get_glibc_version()
+        self.configs = {}
+        self.glibc_configs = {}
+        self.makefile_pieces = ['.PHONY: all\n']
+        self.add_all_configs()
+
+    def get_build_triplet(self):
+        """Determine the build triplet with config.guess."""
+        config_guess = os.path.join(self.component_srcdir('gcc'),
+                                    'config.guess')
+        cg_out = subprocess.run([config_guess], stdout=subprocess.PIPE,
+                                check=True, universal_newlines=True).stdout
+        return cg_out.rstrip()
+
+    def get_glibc_version(self):
+        """Determine the glibc version number (major.minor)."""
+        version_h = os.path.join(self.component_srcdir('glibc'), 'version.h')
+        with open(version_h, 'r') as f:
+            lines = f.readlines()
+        starttext = '#define VERSION "'
+        for l in lines:
+            if l.startswith(starttext):
+                l = l[len(starttext):]
+                l = l.rstrip('"\n')
+                m = re.fullmatch('([0-9]+)\.([0-9]+)[.0-9]*', l)
+                return '%s.%s' % m.group(1, 2)
+        print('error: could not determine glibc version')
+        exit(1)
+
+    def add_all_configs(self):
+        """Add all known glibc build configurations."""
+        self.add_config(arch='aarch64',
+                        os_name='linux-gnu')
+        self.add_config(arch='aarch64_be',
+                        os_name='linux-gnu')
+        self.add_config(arch='alpha',
+                        os_name='linux-gnu')
+        self.add_config(arch='arm',
+                        os_name='linux-gnueabi')
+        self.add_config(arch='armeb',
+                        os_name='linux-gnueabi')
+        self.add_config(arch='armeb',
+                        os_name='linux-gnueabi',
+                        variant='be8',
+                        gcc_cfg=['--with-arch=armv7-a'])
+        self.add_config(arch='arm',
+                        os_name='linux-gnueabihf')
+        self.add_config(arch='armeb',
+                        os_name='linux-gnueabihf')
+        self.add_config(arch='armeb',
+                        os_name='linux-gnueabihf',
+                        variant='be8',
+                        gcc_cfg=['--with-arch=armv7-a'])
+        self.add_config(arch='hppa',
+                        os_name='linux-gnu')
+        self.add_config(arch='ia64',
+                        os_name='linux-gnu',
+                        first_gcc_cfg=['--with-system-libunwind'])
+        self.add_config(arch='m68k',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--disable-multilib'])
+        self.add_config(arch='m68k',
+                        os_name='linux-gnu',
+                        variant='coldfire',
+                        gcc_cfg=['--with-arch=cf', '--disable-multilib'])
+        self.add_config(arch='microblaze',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--disable-multilib'])
+        self.add_config(arch='microblazeel',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--disable-multilib'])
+        self.add_config(arch='mips64',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--with-mips-plt'],
+                        glibcs=[{'variant': 'n32'},
+                                {'arch': 'mips',
+                                 'ccopts': '-mabi=32'},
+                                {'variant': 'n64',
+                                 'ccopts': '-mabi=64'}])
+        self.add_config(arch='mips64',
+                        os_name='linux-gnu',
+                        variant='soft',
+                        gcc_cfg=['--with-mips-plt', '--with-float=soft'],
+                        glibcs=[{'variant': 'n32-soft',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'soft',
+                                 'arch': 'mips',
+                                 'ccopts': '-mabi=32',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'n64-soft',
+                                 'ccopts': '-mabi=64',
+                                 'cfg': ['--without-fp']}])
+        self.add_config(arch='mips64',
+                        os_name='linux-gnu',
+                        variant='nan2008',
+                        gcc_cfg=['--with-mips-plt', '--with-nan=2008',
+                                 '--with-arch-64=mips64r2',
+                                 '--with-arch-32=mips32r2'],
+                        glibcs=[{'variant': 'n32-nan2008'},
+                                {'variant': 'nan2008',
+                                 'arch': 'mips',
+                                 'ccopts': '-mabi=32'},
+                                {'variant': 'n64-nan2008',
+                                 'ccopts': '-mabi=64'}])
+        self.add_config(arch='mips64',
+                        os_name='linux-gnu',
+                        variant='nan2008-soft',
+                        gcc_cfg=['--with-mips-plt', '--with-nan=2008',
+                                 '--with-arch-64=mips64r2',
+                                 '--with-arch-32=mips32r2',
+                                 '--with-float=soft'],
+                        glibcs=[{'variant': 'n32-nan2008-soft',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'nan2008-soft',
+                                 'arch': 'mips',
+                                 'ccopts': '-mabi=32',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'n64-nan2008-soft',
+                                 'ccopts': '-mabi=64',
+                                 'cfg': ['--without-fp']}])
+        self.add_config(arch='mips64el',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--with-mips-plt'],
+                        glibcs=[{'variant': 'n32'},
+                                {'arch': 'mipsel',
+                                 'ccopts': '-mabi=32'},
+                                {'variant': 'n64',
+                                 'ccopts': '-mabi=64'}])
+        self.add_config(arch='mips64el',
+                        os_name='linux-gnu',
+                        variant='soft',
+                        gcc_cfg=['--with-mips-plt', '--with-float=soft'],
+                        glibcs=[{'variant': 'n32-soft',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'soft',
+                                 'arch': 'mipsel',
+                                 'ccopts': '-mabi=32',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'n64-soft',
+                                 'ccopts': '-mabi=64',
+                                 'cfg': ['--without-fp']}])
+        self.add_config(arch='mips64el',
+                        os_name='linux-gnu',
+                        variant='nan2008',
+                        gcc_cfg=['--with-mips-plt', '--with-nan=2008',
+                                 '--with-arch-64=mips64r2',
+                                 '--with-arch-32=mips32r2'],
+                        glibcs=[{'variant': 'n32-nan2008'},
+                                {'variant': 'nan2008',
+                                 'arch': 'mipsel',
+                                 'ccopts': '-mabi=32'},
+                                {'variant': 'n64-nan2008',
+                                 'ccopts': '-mabi=64'}])
+        self.add_config(arch='mips64el',
+                        os_name='linux-gnu',
+                        variant='nan2008-soft',
+                        gcc_cfg=['--with-mips-plt', '--with-nan=2008',
+                                 '--with-arch-64=mips64r2',
+                                 '--with-arch-32=mips32r2',
+                                 '--with-float=soft'],
+                        glibcs=[{'variant': 'n32-nan2008-soft',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'nan2008-soft',
+                                 'arch': 'mipsel',
+                                 'ccopts': '-mabi=32',
+                                 'cfg': ['--without-fp']},
+                                {'variant': 'n64-nan2008-soft',
+                                 'ccopts': '-mabi=64',
+                                 'cfg': ['--without-fp']}])
+        self.add_config(arch='nios2',
+                        os_name='linux-gnu')
+        self.add_config(arch='powerpc',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--disable-multilib', '--enable-secureplt'])
+        self.add_config(arch='powerpc',
+                        os_name='linux-gnu',
+                        variant='soft',
+                        gcc_cfg=['--disable-multilib', '--with-float=soft',
+                                 '--enable-secureplt'],
+                        glibcs=[{'variant': 'soft', 'cfg': ['--without-fp']}])
+        self.add_config(arch='powerpc64',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--disable-multilib', '--enable-secureplt'])
+        self.add_config(arch='powerpc64le',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--disable-multilib', '--enable-secureplt'])
+        self.add_config(arch='powerpc',
+                        os_name='linux-gnuspe',
+                        gcc_cfg=['--disable-multilib', '--enable-secureplt',
+                                 '--enable-e500-double'],
+                        glibcs=[{'cfg': ['--without-fp']}])
+        self.add_config(arch='powerpc',
+                        os_name='linux-gnuspe',
+                        variant='e500v1',
+                        gcc_cfg=['--disable-multilib', '--enable-secureplt'],
+                        glibcs=[{'variant': 'e500v1', 'cfg': ['--without-fp']}])
+        self.add_config(arch='s390x',
+                        os_name='linux-gnu',
+                        glibcs=[{},
+                                {'arch': 's390', 'ccopts': '-m31'}])
+        # SH is missing __builtin_trap support, so work around this;
+        # see <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70216>.
+        no_isolate = ('-fno-isolate-erroneous-paths-dereference'
+                      ' -fno-isolate-erroneous-paths-attribute')
+        self.add_config(arch='sh3',
+                        os_name='linux-gnu',
+                        glibcs=[{'ccopts': no_isolate}])
+        self.add_config(arch='sh3eb',
+                        os_name='linux-gnu',
+                        glibcs=[{'ccopts': no_isolate}])
+        self.add_config(arch='sh4',
+                        os_name='linux-gnu',
+                        glibcs=[{'ccopts': no_isolate}])
+        self.add_config(arch='sh4eb',
+                        os_name='linux-gnu',
+                        glibcs=[{'ccopts': no_isolate}])
+        self.add_config(arch='sh4',
+                        os_name='linux-gnu',
+                        variant='soft',
+                        gcc_cfg=['--without-fp'],
+                        glibcs=[{'variant': 'soft',
+                                 'cfg': ['--without-fp'],
+                                 'ccopts': no_isolate}])
+        self.add_config(arch='sh4eb',
+                        os_name='linux-gnu',
+                        variant='soft',
+                        gcc_cfg=['--without-fp'],
+                        glibcs=[{'variant': 'soft',
+                                 'cfg': ['--without-fp'],
+                                 'ccopts': no_isolate}])
+        self.add_config(arch='sparc64',
+                        os_name='linux-gnu',
+                        glibcs=[{},
+                                {'arch': 'sparcv9',
+                                 'ccopts': '-m32 -mlong-double-128'}])
+        self.add_config(arch='tilegx',
+                        os_name='linux-gnu',
+                        glibcs=[{},
+                                {'variant': '32', 'ccopts': '-m32'}])
+        self.add_config(arch='tilegxbe',
+                        os_name='linux-gnu',
+                        glibcs=[{},
+                                {'variant': '32', 'ccopts': '-m32'}])
+        self.add_config(arch='tilepro',
+                        os_name='linux-gnu')
+        self.add_config(arch='x86_64',
+                        os_name='linux-gnu',
+                        gcc_cfg=['--with-multilib-list=m64,m32,mx32'],
+                        glibcs=[{},
+                                {'variant': 'x32', 'ccopts': '-mx32'},
+                                {'arch': 'i686', 'ccopts': '-m32 -march=i686'}],
+                        extra_glibcs=[{'variant': 'disable-multi-arch',
+                                       'cfg': ['--disable-multi-arch']},
+                                      {'variant': 'disable-multi-arch',
+                                       'arch': 'i686',
+                                       'ccopts': '-m32 -march=i686',
+                                       'cfg': ['--disable-multi-arch']},
+                                      {'arch': 'i486',
+                                       'ccopts': '-m32 -march=i486'},
+                                      {'arch': 'i586',
+                                       'ccopts': '-m32 -march=i586'}])
+
+    def add_config(self, **args):
+        """Add an individual build configuration."""
+        cfg = Config(self, **args)
+        if cfg.name in self.configs:
+            print('error: duplicate config %s' % cfg.name)
+            exit(1)
+        self.configs[cfg.name] = cfg
+        for c in cfg.all_glibcs:
+            if c.name in self.glibc_configs:
+                print('error: duplicate glibc config %s' % c.name)
+                exit(1)
+            self.glibc_configs[c.name] = c
+
+    def component_srcdir(self, component):
+        """Return the source directory for a given component, e.g. gcc."""
+        return os.path.join(self.srcdir, component)
+
+    def component_builddir(self, action, config, component, subconfig=None):
+        """Return the directory to use for a build."""
+        if config is None:
+            # Host libraries.
+            assert subconfig is None
+            return os.path.join(self.builddir, action, component)
+        if subconfig is None:
+            return os.path.join(self.builddir, action, config, component)
+        else:
+            # glibc build as part of compiler build.
+            return os.path.join(self.builddir, action, config, component,
+                                subconfig)
+
+    def compiler_installdir(self, config):
+        """Return the directory in which to install a compiler."""
+        return os.path.join(self.installdir, 'compilers', config)
+
+    def compiler_bindir(self, config):
+        """Return the directory in which to find compiler binaries."""
+        return os.path.join(self.compiler_installdir(config), 'bin')
+
+    def compiler_sysroot(self, config):
+        """Return the sysroot directory for a compiler."""
+        return os.path.join(self.compiler_installdir(config), 'sysroot')
+
+    def glibc_installdir(self, config):
+        """Return the directory in which to install glibc."""
+        return os.path.join(self.installdir, 'glibcs', config)
+
+    def run_builds(self, action, configs):
+        """Run the requested builds."""
+        if action == 'checkout':
+            self.checkout(configs)
+            return
+        elif action == 'host-libraries':
+            if configs:
+                print('error: configurations specified for host-libraries')
+                exit(1)
+            self.build_host_libraries()
+        elif action == 'compilers':
+            self.build_compilers(configs)
+        else:
+            self.build_glibcs(configs)
+        self.write_files()
+        self.do_build()
+
+    @staticmethod
+    def remove_dirs(*args):
+        """Remove directories and their contents if they exist."""
+        for dir in args:
+            shutil.rmtree(dir, ignore_errors=True)
+
+    @staticmethod
+    def remove_recreate_dirs(*args):
+        """Remove directories if they exist, and create them as empty."""
+        Context.remove_dirs(*args)
+        for dir in args:
+            os.makedirs(dir, exist_ok=True)
+
+    def add_makefile_cmdlist(self, target, cmdlist, logsdir):
+        """Add makefile text for a list of commands."""
+        commands = cmdlist.makefile_commands(self.wrapper, logsdir)
+        self.makefile_pieces.append('all: %s\n.PHONY: %s\n%s:\n%s\n' %
+                                    (target, target, target, commands))
+
+    def write_files(self):
+        """Write out the Makefile and wrapper script."""
+        mftext = ''.join(self.makefile_pieces)
+        with open(self.makefile, 'w') as f:
+            f.write(mftext)
+        wrapper_text = (
+            '#!/bin/sh\n'
+            'prev_base=$1\n'
+            'this_base=$2\n'
+            'desc=$3\n'
+            'dir=$4\n'
+            'path=$5\n'
+            'shift 5\n'
+            'prev_status=$prev_base-status.txt\n'
+            'this_status=$this_base-status.txt\n'
+            'this_log=$this_base-log.txt\n'
+            'date > "$this_log"\n'
+            'echo >> "$this_log"\n'
+            'echo "Description: $desc" >> "$this_log"\n'
+            'echo "Command: $*" >> "$this_log"\n'
+            'echo "Directory: $dir" >> "$this_log"\n'
+            'echo "Path addition: $path" >> "$this_log"\n'
+            'echo >> "$this_log"\n'
+            'record_status ()\n'
+            '{\n'
+            '  echo >> "$this_log"\n'
+            '  echo "$1: $desc" > "$this_status"\n'
+            '  echo "$1: $desc" >> "$this_log"\n'
+            '  echo >> "$this_log"\n'
+            '  date >> "$this_log"\n'
+            '  echo "$1: $desc"\n'
+            '  exit 0\n'
+            '}\n'
+            'check_error ()\n'
+            '{\n'
+            '  if [ "$1" != "0" ]; then\n'
+            '    record_status FAIL\n'
+            '  fi\n'
+            '}\n'
+            'if [ "$prev_base" ] && ! grep -q "^PASS" "$prev_status"; then\n'
+            '    record_status UNRESOLVED\n'
+            'fi\n'
+            'if [ "$dir" ]; then\n'
+            '  cd "$dir"\n'
+            '  check_error "$?"\n'
+            'fi\n'
+            'if [ "$path" ]; then\n'
+            '  PATH=$path:$PATH\n'
+            'fi\n'
+            '"$@" < /dev/null >> "$this_log" 2>&1\n'
+            'check_error "$?"\n'
+            'record_status PASS\n')
+        with open(self.wrapper, 'w') as f:
+            f.write(wrapper_text)
+        os.chmod(self.wrapper,
+                 (stat.S_IRWXU|stat.S_IRGRP|stat.S_IXGRP|
+                  stat.S_IROTH|stat.S_IXOTH))
+        save_logs_text = (
+            '#!/bin/sh\n'
+            'if ! [ -f tests.sum ]; then\n'
+            '  echo "No test summary available."\n'
+            '  exit 0\n'
+            'fi\n'
+            'save_file ()\n'
+            '{\n'
+            '  echo "Contents of $1:"\n'
+            '  echo\n'
+            '  cat "$1"\n'
+            '  echo\n'
+            '  echo "End of contents of $1."\n'
+            '  echo\n'
+            '}\n'
+            'save_file tests.sum\n'
+            'non_pass_tests=$(grep -v "^PASS: " tests.sum | sed -e "s/^PASS: //")\n'
+            'for t in $non_pass_tests; do\n'
+            '  if [ -f "$t.out" ]; then\n'
+            '    save_file "$t.out"\n'
+            '  fi\n'
+            'done\n')
+        with open(self.save_logs, 'w') as f:
+            f.write(save_logs_text)
+        os.chmod(self.save_logs,
+                 (stat.S_IRWXU|stat.S_IRGRP|stat.S_IXGRP|
+                  stat.S_IROTH|stat.S_IXOTH))
+
+    def do_build(self):
+        """Do the actual build."""
+        cmd = ['make', '-j%d' % self.parallelism, '-s', '-C', self.builddir]
+        subprocess.run(cmd, check=True)
+
+    def build_host_libraries(self):
+        """Build the host libraries."""
+        installdir = self.host_libraries_installdir
+        builddir = os.path.join(self.builddir, 'host-libraries')
+        logsdir = os.path.join(self.logsdir, 'host-libraries')
+        self.remove_recreate_dirs(installdir, builddir, logsdir)
+        cmdlist = CommandList('host-libraries', self.keep)
+        self.build_host_library(cmdlist, 'gmp')
+        self.build_host_library(cmdlist, 'mpfr',
+                                ['--with-gmp=%s' % installdir])
+        self.build_host_library(cmdlist, 'mpc',
+                                ['--with-gmp=%s' % installdir,
+                                '--with-mpfr=%s' % installdir])
+        cmdlist.add_command('done', ['touch', os.path.join(installdir, 'ok')])
+        self.add_makefile_cmdlist('host-libraries', cmdlist, logsdir)
+
+    def build_host_library(self, cmdlist, lib, extra_opts=None):
+        """Build one host library."""
+        srcdir = self.component_srcdir(lib)
+        builddir = self.component_builddir('host-libraries', None, lib)
+        installdir = self.host_libraries_installdir
+        cmdlist.push_subdesc(lib)
+        cmdlist.create_use_dir(builddir)
+        cfg_cmd = [os.path.join(srcdir, 'configure'),
+                   '--prefix=%s' % installdir,
+                   '--disable-shared']
+        if extra_opts:
+            cfg_cmd.extend (extra_opts)
+        cmdlist.add_command('configure', cfg_cmd)
+        cmdlist.add_command('build', ['make'])
+        cmdlist.add_command('check', ['make', 'check'])
+        cmdlist.add_command('install', ['make', 'install'])
+        cmdlist.cleanup_dir()
+        cmdlist.pop_subdesc()
+
+    def build_compilers(self, configs):
+        """Build the compilers."""
+        if not configs:
+            self.remove_dirs(os.path.join(self.builddir, 'compilers'))
+            self.remove_dirs(os.path.join(self.installdir, 'compilers'))
+            self.remove_dirs(os.path.join(self.logsdir, 'compilers'))
+            configs = sorted(self.configs.keys())
+        for c in configs:
+            self.configs[c].build()
+
+    def build_glibcs(self, configs):
+        """Build the glibcs."""
+        if not configs:
+            self.remove_dirs(os.path.join(self.builddir, 'glibcs'))
+            self.remove_dirs(os.path.join(self.installdir, 'glibcs'))
+            self.remove_dirs(os.path.join(self.logsdir, 'glibcs'))
+            configs = sorted(self.glibc_configs.keys())
+        for c in configs:
+            self.glibc_configs[c].build()
+
+    def checkout(self, versions):
+        """Check out the desired component versions."""
+        default_versions = {'binutils': 'vcs-2.27',
+                            'gcc': 'vcs-6',
+                            'glibc': 'vcs-mainline',
+                            'gmp': '6.1.1',
+                            'linux': '4.8.6',
+                            'mpc': '1.0.3',
+                            'mpfr': '3.1.5'}
+        use_versions = {}
+        for v in versions:
+            found_v = False
+            for k in default_versions.keys():
+                kx = k + '-'
+                if v.startswith(kx):
+                    vx = v[len(kx):]
+                    if k in use_versions:
+                        print('error: multiple versions for %s' % k)
+                        exit(1)
+                    use_versions[k] = vx
+                    found_v = True
+                    break
+            if not found_v:
+                print('error: unknown component in %s' % v)
+                exit(1)
+        for k in default_versions.keys():
+            if k not in use_versions:
+                use_versions[k] = default_versions[k]
+        os.makedirs(self.srcdir, exist_ok=True)
+        for k in sorted(default_versions.keys()):
+            v = use_versions[k]
+            if v.startswith('vcs-'):
+                self.checkout_vcs(k, v[4:])
+            else:
+                self.checkout_tar(k, v)
+
+    def checkout_vcs(self, component, version):
+        """Check out the given version of the given component from version
+        control."""
+        if component == 'binutils':
+            git_url = 'git://sourceware.org/git/binutils-gdb.git'
+            if version == 'mainline':
+                git_branch = 'master'
+            else:
+                trans = str.maketrans({'.': '_'})
+                git_branch = 'binutils-%s-branch' % version.translate(trans)
+            self.git_checkout(component, git_url, git_branch)
+        elif component == 'gcc':
+            if version == 'mainline':
+                branch = 'trunk'
+            else:
+                trans = str.maketrans({'.': '_'})
+                branch = 'branches/gcc-%s-branch' % version.translate(trans)
+            svn_url = 'svn://gcc.gnu.org/svn/gcc/%s' % branch
+            self.gcc_checkout(svn_url)
+        elif component == 'glibc':
+            git_url = 'git://sourceware.org/git/glibc.git'
+            if version == 'mainline':
+                git_branch = 'master'
+            else:
+                git_branch = 'release/%s/master' % version
+            self.git_checkout(component, git_url, git_branch)
+            self.fix_glibc_timestamps()
+        else:
+            print('error: component %s coming from VCS' % component)
+            exit(1)
+
+    def git_checkout(self, component, git_url, git_branch):
+        """Check out a component from git."""
+        subprocess.run(['git', 'clone', '-q', '-b', git_branch, git_url,
+                        self.component_srcdir(component)], check=True)
+
+    def fix_glibc_timestamps(self):
+        """Fix timestamps in a glibc checkout."""
+        # Ensure that builds do not try to regenerate generated files
+        # in the source tree.
+        srcdir = self.component_srcdir('glibc')
+        for dirpath, dirnames, filenames in os.walk(srcdir):
+            for f in filenames:
+                if (f == 'configure' or
+                    f == 'preconfigure' or
+                    f.endswith('-kw.h')):
+                    to_touch = os.path.join(dirpath, f)
+                    subprocess.run(['touch', to_touch], check=True)
+
+    def gcc_checkout(self, svn_url):
+        """Check out GCC from SVN."""
+        subprocess.run(['svn', 'co', '-q', svn_url,
+                        self.component_srcdir('gcc')], check=True)
+        subprocess.run(['contrib/gcc_update', '--silent'],
+                       cwd=self.component_srcdir('gcc'), check=True)
+
+    def checkout_tar(self, component, version):
+        """Check out the given version of the given component from a
+        tarball."""
+        url_map = {'binutils': 'https://ftp.gnu.org/gnu/binutils/binutils-%(version)s.tar.bz2',
+                   'gcc': 'https://ftp.gnu.org/gnu/gcc/gcc-%(version)s/gcc-%(version)s.tar.bz2',
+                   'gmp': 'https://ftp.gnu.org/gnu/gmp/gmp-%(version)s.tar.xz',
+                   'linux': 'https://www.kernel.org/pub/linux/kernel/v4.x/linux-%(version)s.tar.xz',
+                   'mpc': 'https://ftp.gnu.org/gnu/mpc/mpc-%(version)s.tar.gz',
+                   'mpfr': 'https://ftp.gnu.org/gnu/mpfr/mpfr-%(version)s.tar.xz'}
+        if component not in url_map:
+            print('error: component %s coming from tarball' % component)
+            exit(1)
+        url = url_map[component] % {'version': version}
+        filename = os.path.join(self.srcdir, url.split('/')[-1])
+        response = urllib.request.urlopen(url)
+        data = response.read()
+        with open(filename, 'wb') as f:
+            f.write(data)
+        subprocess.run(['tar', '-C', self.srcdir, '-x', '-f', filename],
+                       check=True)
+        os.rename(os.path.join(self.srcdir, '%s-%s' % (component, version)),
+                  self.component_srcdir(component))
+        os.remove(filename)
+
+
+class Config:
+
+    """A configuration for building a compiler and associated libraries."""
+
+    def __init__(self, ctx, arch, os_name, variant=None, gcc_cfg=None,
+                 first_gcc_cfg=None, glibcs=None, extra_glibcs=None):
+        """Initialize a Config object."""
+        self.ctx = ctx
+        self.arch = arch
+        self.os = os_name
+        self.variant = variant
+        if variant is None:
+            self.name = '%s-%s' % (arch, os_name)
+        else:
+            self.name = '%s-%s-%s' % (arch, os_name, variant)
+        self.triplet = '%s-glibc-%s' % (arch, os_name)
+        if gcc_cfg is None:
+            self.gcc_cfg = []
+        else:
+            self.gcc_cfg = gcc_cfg
+        if first_gcc_cfg is None:
+            self.first_gcc_cfg = []
+        else:
+            self.first_gcc_cfg = first_gcc_cfg
+        if glibcs is None:
+            glibcs = [{'variant': variant}]
+        if extra_glibcs is None:
+            extra_glibcs = []
+        glibcs = [Glibc(self, **g) for g in glibcs]
+        extra_glibcs = [Glibc(self, **g) for g in extra_glibcs]
+        self.all_glibcs = glibcs + extra_glibcs
+        self.compiler_glibcs = glibcs
+        self.installdir = ctx.compiler_installdir(self.name)
+        self.bindir = ctx.compiler_bindir(self.name)
+        self.sysroot = ctx.compiler_sysroot(self.name)
+        self.builddir = os.path.join(ctx.builddir, 'compilers', self.name)
+        self.logsdir = os.path.join(ctx.logsdir, 'compilers', self.name)
+
+    def component_builddir(self, component):
+        """Return the directory to use for a (non-glibc) build."""
+        return self.ctx.component_builddir('compilers', self.name, component)
+
+    def build(self):
+        """Generate commands to build this compiler."""
+        self.ctx.remove_recreate_dirs(self.installdir, self.builddir,
+                                      self.logsdir)
+        cmdlist = CommandList('compilers-%s' % self.name, self.ctx.keep)
+        cmdlist.add_command('check-host-libraries',
+                            ['test', '-f',
+                             os.path.join(self.ctx.host_libraries_installdir,
+                                          'ok')])
+        cmdlist.use_path(self.bindir)
+        self.build_cross_tool(cmdlist, 'binutils', 'binutils',
+                              ['--disable-gdb',
+                               '--disable-libdecnumber',
+                               '--disable-readline',
+                               '--disable-sim'])
+        if self.os.startswith('linux'):
+            self.install_linux_headers(cmdlist)
+        self.build_gcc(cmdlist, True)
+        for g in self.compiler_glibcs:
+            cmdlist.push_subdesc('glibc')
+            cmdlist.push_subdesc(g.name)
+            g.build_glibc(cmdlist, True)
+            cmdlist.pop_subdesc()
+            cmdlist.pop_subdesc()
+        self.build_gcc(cmdlist, False)
+        cmdlist.add_command('done', ['touch',
+                                     os.path.join(self.installdir, 'ok')])
+        self.ctx.add_makefile_cmdlist('compilers-%s' % self.name, cmdlist,
+                                      self.logsdir)
+
+    def build_cross_tool(self, cmdlist, tool_src, tool_build, extra_opts=None):
+        """Build one cross tool."""
+        srcdir = self.ctx.component_srcdir(tool_src)
+        builddir = self.component_builddir(tool_build)
+        cmdlist.push_subdesc(tool_build)
+        cmdlist.create_use_dir(builddir)
+        cfg_cmd = [os.path.join(srcdir, 'configure'),
+                   '--prefix=%s' % self.installdir,
+                   '--build=%s' % self.ctx.build_triplet,
+                   '--host=%s' % self.ctx.build_triplet,
+                   '--target=%s' % self.triplet,
+                   '--with-sysroot=%s' % self.sysroot]
+        if extra_opts:
+            cfg_cmd.extend(extra_opts)
+        cmdlist.add_command('configure', cfg_cmd)
+        cmdlist.add_command('build', ['make'])
+        cmdlist.add_command('install', ['make', 'install'])
+        cmdlist.cleanup_dir()
+        cmdlist.pop_subdesc()
+
+    def install_linux_headers(self, cmdlist):
+        """Install Linux kernel headers."""
+        arch_map = {'aarch64': 'arm64',
+                    'alpha': 'alpha',
+                    'arm': 'arm',
+                    'hppa': 'parisc',
+                    'i486': 'x86',
+                    'i586': 'x86',
+                    'i686': 'x86',
+                    'i786': 'x86',
+                    'ia64': 'ia64',
+                    'm68k': 'm68k',
+                    'microblaze': 'microblaze',
+                    'mips': 'mips',
+                    'nios2': 'nios2',
+                    'powerpc': 'powerpc',
+                    's390': 's390',
+                    'sh': 'sh',
+                    'sparc': 'sparc',
+                    'tile': 'tile',
+                    'x86_64': 'x86'}
+        linux_arch = None
+        for k in arch_map:
+            if self.arch.startswith(k):
+                linux_arch = arch_map[k]
+                break
+        assert linux_arch is not None
+        srcdir = self.ctx.component_srcdir('linux')
+        builddir = self.component_builddir('linux')
+        headers_dir = os.path.join(self.sysroot, 'usr')
+        cmdlist.push_subdesc('linux')
+        cmdlist.create_use_dir(builddir)
+        cmdlist.add_command('install-headers',
+                            ['make', '-C', srcdir, 'O=%s' % builddir,
+                             'ARCH=%s' % linux_arch,
+                             'INSTALL_HDR_PATH=%s' % headers_dir,
+                             'headers_install'])
+        cmdlist.cleanup_dir()
+        cmdlist.pop_subdesc()
+
+    def build_gcc(self, cmdlist, bootstrap):
+        """Build GCC."""
+        # libsanitizer commonly breaks because of glibc header
+        # changes, or on unusual targets.  libssp is of little
+        # relevance with glibc's own stack checking support.
+        cfg_opts = list(self.gcc_cfg)
+        cfg_opts += ['--disable-libsanitizer', '--disable-libssp']
+        if bootstrap:
+            tool_build = 'gcc-first'
+            # Building a static-only, C-only compiler that is
+            # sufficient to build glibc.  Various libraries and
+            # features that may require libc headers must be disabled.
+            # When configuring with a sysroot, --with-newlib is
+            # required to define inhibit_libc (to stop some parts of
+            # libgcc including libc headers); --without-headers is not
+            # sufficient.
+            cfg_opts += ['--enable-languages=c', '--disable-shared',
+                         '--disable-threads',
+                         '--disable-libatomic',
+                         '--disable-decimal-float',
+                         '--disable-libffi',
+                         '--disable-libgomp',
+                         '--disable-libitm',
+                         '--disable-libmpx',
+                         '--disable-libquadmath',
+                         '--without-headers', '--with-newlib',
+                         '--with-glibc-version=%s' % self.ctx.glibc_version
+                         ]
+            cfg_opts += self.first_gcc_cfg
+        else:
+            tool_build = 'gcc'
+            cfg_opts += ['--enable-languages=c,c++', '--enable-shared',
+                         '--enable-threads']
+        self.build_cross_tool(cmdlist, 'gcc', tool_build, cfg_opts)
+
+
+class Glibc:
+
+    """A configuration for building glibc."""
+
+    def __init__(self, compiler, arch=None, os_name=None, variant=None,
+                 cfg=None, ccopts=None):
+        """Initialize a Glibc object."""
+        self.ctx = compiler.ctx
+        self.compiler = compiler
+        if arch is None:
+            self.arch = compiler.arch
+        else:
+            self.arch = arch
+        if os_name is None:
+            self.os = compiler.os
+        else:
+            self.os = os_name
+        self.variant = variant
+        if variant is None:
+            self.name = '%s-%s' % (self.arch, self.os)
+        else:
+            self.name = '%s-%s-%s' % (self.arch, self.os, variant)
+        self.triplet = '%s-glibc-%s' % (self.arch, self.os)
+        if cfg is None:
+            self.cfg = []
+        else:
+            self.cfg = cfg
+        self.ccopts = ccopts
+
+    def tool_name(self, tool):
+        """Return the name of a cross-compilation tool."""
+        ctool = '%s-%s' % (self.compiler.triplet, tool)
+        if self.ccopts and (tool == 'gcc' or tool == 'g++'):
+            ctool = '%s %s' % (ctool, self.ccopts)
+        return ctool
+
+    def build(self):
+        """Generate commands to build this glibc."""
+        builddir = self.ctx.component_builddir('glibcs', self.name, 'glibc')
+        installdir = self.ctx.glibc_installdir(self.name)
+        logsdir = os.path.join(self.ctx.logsdir, 'glibcs', self.name)
+        self.ctx.remove_recreate_dirs(installdir, builddir, logsdir)
+        cmdlist = CommandList('glibcs-%s' % self.name, self.ctx.keep)
+        cmdlist.add_command('check-compilers',
+                            ['test', '-f',
+                             os.path.join(self.compiler.installdir, 'ok')])
+        cmdlist.use_path(self.compiler.bindir)
+        self.build_glibc(cmdlist, False)
+        self.ctx.add_makefile_cmdlist('glibcs-%s' % self.name, cmdlist,
+                                      logsdir)
+
+    def build_glibc(self, cmdlist, for_compiler):
+        """Generate commands to build this glibc, either as part of a compiler
+        build or with the bootstrapped compiler (and in the latter case, run
+        tests as well)."""
+        srcdir = self.ctx.component_srcdir('glibc')
+        if for_compiler:
+            builddir = self.ctx.component_builddir('compilers',
+                                                   self.compiler.name, 'glibc',
+                                                   self.name)
+            installdir = self.compiler.sysroot
+            srcdir_copy = self.ctx.component_builddir('compilers',
+                                                      self.compiler.name,
+                                                      'glibc-src',
+                                                      self.name)
+        else:
+            builddir = self.ctx.component_builddir('glibcs', self.name,
+                                                   'glibc')
+            installdir = self.ctx.glibc_installdir(self.name)
+            srcdir_copy = self.ctx.component_builddir('glibcs', self.name,
+                                                      'glibc-src')
+        cmdlist.create_use_dir(builddir)
+        # glibc builds write into the source directory, and even if
+        # not intentionally there is a risk of bugs that involve
+        # writing into the working directory.  To avoid possible
+        # concurrency issues, copy the source directory.
+        cmdlist.create_copy_dir(srcdir, srcdir_copy)
+        cfg_cmd = [os.path.join(srcdir_copy, 'configure'),
+                   '--prefix=/usr',
+                   '--enable-add-ons',
+                   '--build=%s' % self.ctx.build_triplet,
+                   '--host=%s' % self.triplet,
+                   'CC=%s' % self.tool_name('gcc'),
+                   'CXX=%s' % self.tool_name('g++'),
+                   'AR=%s' % self.tool_name('ar'),
+                   'AS=%s' % self.tool_name('as'),
+                   'LD=%s' % self.tool_name('ld'),
+                   'NM=%s' % self.tool_name('nm'),
+                   'OBJCOPY=%s' % self.tool_name('objcopy'),
+                   'OBJDUMP=%s' % self.tool_name('objdump'),
+                   'RANLIB=%s' % self.tool_name('ranlib'),
+                   'READELF=%s' % self.tool_name('readelf'),
+                   'STRIP=%s' % self.tool_name('strip')]
+        cfg_cmd += self.cfg
+        cmdlist.add_command('configure', cfg_cmd)
+        cmdlist.add_command('build', ['make'])
+        cmdlist.add_command('install', ['make', 'install',
+                                        'install_root=%s' % installdir])
+        # GCC uses paths such as lib/../lib64, so make sure lib
+        # directories always exist.
+        cmdlist.add_command('mkdir-lib', ['mkdir', '-p',
+                                          os.path.join(installdir, 'lib'),
+                                          os.path.join(installdir,
+                                                       'usr', 'lib')])
+        if not for_compiler:
+            cmdlist.add_command('check', ['make', 'check'])
+            cmdlist.add_command('save-logs', [self.ctx.save_logs],
+                                always_run=True)
+        cmdlist.cleanup_dir('cleanup-src', srcdir_copy)
+        cmdlist.cleanup_dir()
+
+
+class Command:
+
+    """A command run in the build process."""
+
+    def __init__(self, desc, num, dir, path, command, always_run=False):
+        """Initialize a Command object."""
+        self.dir = dir
+        self.path = path
+        self.desc = desc
+        trans = str.maketrans({' ': '-'})
+        self.logbase = '%03d-%s' % (num, desc.translate(trans))
+        self.command = command
+        self.always_run = always_run
+
+    @staticmethod
+    def shell_make_quote_string(s):
+        """Given a string not containing a newline, quote it for use by the
+        shell and make."""
+        assert '\n' not in s
+        if re.fullmatch('[]+,./0-9@A-Z_a-z-]+', s):
+            return s
+        strans = str.maketrans({"'": "'\\''"})
+        s = "'%s'" % s.translate(strans)
+        mtrans = str.maketrans({'$': '$$'})
+        return s.translate(mtrans)
+
+    @staticmethod
+    def shell_make_quote_list(l, translate_make):
+        """Given a list of strings not containing newlines, quote them for use
+        by the shell and make, returning a single string.  If translate_make
+        is true and the first string is 'make', change it to $(MAKE)."""
+        l = [Command.shell_make_quote_string(s) for s in l]
+        if translate_make and l[0] == 'make':
+            l[0] = '$(MAKE)'
+        return ' '.join(l)
+
+    def shell_make_quote(self):
+        """Return this command quoted for the shell and make."""
+        return self.shell_make_quote_list(self.command, True)
+
+
+class CommandList:
+
+    """A list of commands run in the build process."""
+
+    def __init__(self, desc, keep):
+        """Initialize a CommandList object."""
+        self.cmdlist = []
+        self.dir = None
+        self.path = None
+        self.desc = [desc]
+        self.keep = keep
+
+    def desc_txt(self, desc):
+        """Return the description to use for a command."""
+        return '%s %s' % (' '.join(self.desc), desc)
+
+    def use_dir(self, dir):
+        """Set the default directory for subsequent commands."""
+        self.dir = dir
+
+    def use_path(self, path):
+        """Set a directory to be prepended to the PATH for subsequent
+        commands."""
+        self.path = path
+
+    def push_subdesc(self, subdesc):
+        """Set the default subdescription for subsequent commands (e.g., the
+        name of a component being built, within the series of commands
+        building it)."""
+        self.desc.append(subdesc)
+
+    def pop_subdesc(self):
+        """Pop a subdescription from the list of descriptions."""
+        self.desc.pop()
+
+    def create_use_dir(self, dir):
+        """Remove and recreate a directory and use it for subsequent
+        commands."""
+        self.add_command_dir('rm', None, ['rm', '-rf', dir])
+        self.add_command_dir('mkdir', None, ['mkdir', '-p', dir])
+        self.use_dir(dir)
+
+    def create_copy_dir(self, src, dest):
+        """Remove a directory and recreate it as a copy from the given
+        source."""
+        self.add_command_dir('copy-rm', None, ['rm', '-rf', dest])
+        parent = os.path.dirname(dest)
+        self.add_command_dir('copy-mkdir', None, ['mkdir', '-p', parent])
+        self.add_command_dir('copy', None, ['cp', '-a', src, dest])
+
+    def add_command_dir(self, desc, dir, command, always_run=False):
+        """Add a command to run in a given directory."""
+        cmd = Command(self.desc_txt(desc), len(self.cmdlist), dir, self.path,
+                      command, always_run)
+        self.cmdlist.append(cmd)
+
+    def add_command(self, desc, command, always_run=False):
+        """Add a command to run in the default directory."""
+        cmd = Command(self.desc_txt(desc), len(self.cmdlist), self.dir,
+                      self.path, command, always_run)
+        self.cmdlist.append(cmd)
+
+    def cleanup_dir(self, desc='cleanup', dir=None):
+        """Clean up a build directory.  If no directory is specified, the
+        default directory is cleaned up and ceases to be the default
+        directory."""
+        if dir is None:
+            dir = self.dir
+            self.use_dir(None)
+        if self.keep != 'all':
+            self.add_command_dir(desc, None, ['rm', '-rf', dir],
+                                 always_run=(self.keep == 'none'))
+
+    def makefile_commands(self, wrapper, logsdir):
+        """Return the sequence of commands in the form of text for a Makefile.
+        The given wrapper script takes arguments: base of logs for
+        previous command, or empty; base of logs for this command;
+        description; directory; PATH addition; the command itself."""
+        # prev_base is the base of the name for logs of the previous
+        # command that is not always-run (that is, a build command,
+        # whose failure should stop subsequent build commands from
+        # being run, as opposed to a cleanup command, which is run
+        # even if previous commands failed).
+        prev_base = ''
+        cmds = []
+        for c in self.cmdlist:
+            ctxt = c.shell_make_quote()
+            if prev_base and not c.always_run:
+                prev_log = os.path.join(logsdir, prev_base)
+            else:
+                prev_log = ''
+            this_log = os.path.join(logsdir, c.logbase)
+            if not c.always_run:
+                prev_base = c.logbase
+            if c.dir is None:
+                dir = ''
+            else:
+                dir = c.dir
+            if c.path is None:
+                path = ''
+            else:
+                path = c.path
+            prelims = [wrapper, prev_log, this_log, c.desc, dir, path]
+            prelim_txt = Command.shell_make_quote_list(prelims, False)
+            cmds.append('\t@%s %s' % (prelim_txt, ctxt))
+        return '\n'.join(cmds)
+
+
+def get_parser():
+    """Return an argument parser for this module."""
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('-j', dest='parallelism',
+                        help='Run this number of jobs in parallel',
+                        type=int, default=os.cpu_count())
+    parser.add_argument('--keep', dest='keep',
+                        help='Whether to keep all build directories, '
+                        'none or only those from failed builds',
+                        default='none', choices=('none', 'all', 'failed'))
+    parser.add_argument('topdir',
+                        help='Toplevel working directory')
+    parser.add_argument('action',
+                        help='What to do',
+                        choices=('checkout', 'host-libraries', 'compilers',
+                                 'glibcs'))
+    parser.add_argument('configs',
+                        help='Versions to check out or configurations to build',
+                        nargs='*')
+    return parser
+
+
+def main(argv):
+    """The main entry point."""
+    parser = get_parser()
+    opts = parser.parse_args(argv)
+    topdir = os.path.abspath(opts.topdir)
+    ctx = Context(topdir, opts.parallelism, opts.keep, opts.action)
+    ctx.run_builds(opts.action, opts.configs)
+
+
+if __name__ == '__main__':
+    main(sys.argv[1:])
