Rolling forward clang, hiding some warnings

tools/clang/scripts/update.py

Index: tools/clang/scripts/update.py
diff --git a/tools/clang/scripts/update.py b/tools/clang/scripts/update.py
index aa74bdc37afc7500c412c5cd063524a1386874ce..38c0e779d212ffb588f0d2d54d535e409ad03f41 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -9,7 +9,9 @@ update.sh. This script should replace update.sh on all platforms eventually."""
 import argparse
 import contextlib
 import cStringIO
+import glob
 import os
+import pipes
 import re
 import shutil
 import subprocess
@@ -26,7 +28,7 @@ import zipfile
 # Note: this revision is only used for Windows. Other platforms use update.sh.
 # TODO(thakis): Use the same revision on Windows and non-Windows.
 # TODO(thakis): Remove update.sh, use update.py everywhere.
-LLVM_WIN_REVISION = '238562'
+LLVM_WIN_REVISION = '247874'
 
 use_head_revision = 'LLVM_FORCE_HEAD_REVISION' in os.environ
 if use_head_revision:
@@ -52,11 +54,13 @@ COMPILER_RT_BUILD_DIR = os.path.join(LLVM_BUILD_DIR, '32bit-compiler-rt')
 CLANG_DIR = os.path.join(LLVM_DIR, 'tools', 'clang')
 LLD_DIR = os.path.join(LLVM_DIR, 'tools', 'lld')
 COMPILER_RT_DIR = os.path.join(LLVM_DIR, 'projects', 'compiler-rt')
+LIBCXX_DIR = os.path.join(LLVM_DIR, 'projects', 'libcxx')
+LIBCXXABI_DIR = os.path.join(LLVM_DIR, 'projects', 'libcxxabi')
 LLVM_BUILD_TOOLS_DIR = os.path.abspath(
     os.path.join(LLVM_DIR, '..', 'llvm-build-tools'))
 STAMP_FILE = os.path.join(LLVM_DIR, '..', 'llvm-build', 'cr_build_revision')
 BINUTILS_DIR = os.path.join(THIRD_PARTY_DIR, 'binutils')
-VERSION = '3.7.0'
+VERSION = '3.8.0'
 
 # URL for pre-built binaries.
 CDS_URL = 'https://commondatastorage.googleapis.com/chromium-browser-clang'
@@ -93,22 +97,22 @@ def ReadStampFile():
   """Return the contents of the stamp file, or '' if it doesn't exist."""
   try:
     with open(STAMP_FILE, 'r') as f:
-      return f.read();
+      return f.read()
   except IOError:
     return ''
 
 
 def WriteStampFile(s):
   """Write s to the stamp file."""
-  if not os.path.exists(LLVM_BUILD_DIR):
-    os.makedirs(LLVM_BUILD_DIR)
+  if not os.path.exists(os.path.dirname(STAMP_FILE)):
+    os.makedirs(os.path.dirname(STAMP_FILE))
   with open(STAMP_FILE, 'w') as f:
     f.write(s)
 
 
 def GetSvnRevision(svn_repo):
   """Returns current revision of the svn repo at svn_repo."""
-  svn_info = subprocess.check_output(['svn', 'info', svn_repo], shell=True)
+  svn_info = subprocess.check_output('svn info ' + svn_repo, shell=True)
   m = re.search(r'Revision: (\d+)', svn_info)
   return m.group(1)
 
@@ -125,12 +129,31 @@ def RmTree(dir):
   shutil.rmtree(dir, onerror=ChmodAndRetry)
 
 
-def RunCommand(command, fail_hard=True):
+def RunCommand(command, msvc_arch=None, env=None, fail_hard=True):
   """Run command and return success (True) or failure; or if fail_hard is
-     True, exit on failure."""
-
-  print 'Running %s' % (str(command))
-  if subprocess.call(command, shell=True) == 0:
+     True, exit on failure.  If msvc_arch is set, runs the command in a
+     shell with the msvc tools for that architecture."""
+
+  if msvc_arch and sys.platform == 'win32':
+    command = GetVSVersion().SetupScript(msvc_arch) + ['&&'] + command
+
+  # https://docs.python.org/2/library/subprocess.html:
+  # "On Unix with shell=True [...] if args is a sequence, the first item
+  # specifies the command string, and any additional items will be treated as
+  # additional arguments to the shell itself.  That is to say, Popen does the
+  # equivalent of:
+  #   Popen(['/bin/sh', '-c', args[0], args[1], ...])"
+  #
+  # We want to pass additional arguments to command[0], not to the shell,
+  # so manually join everything into a single string.
+  # Annoyingly, for "svn co url c:\path", pipes.quote() thinks that it should
+  # quote c:\path but svn can't handle quoted paths on Windows.  Since on
+  # Windows follow-on args are passed to args[0] instead of the shell, don't
+  # do the single-string transformation there.
+  if sys.platform != 'win32':
+    command = ' '.join([pipes.quote(c) for c in command])
+  print 'Running', command
+  if subprocess.call(command, env=env, shell=True) == 0:
     return True
   print 'Failed.'
   if fail_hard:
@@ -172,7 +195,58 @@ def Checkout(name, url, dir):
   RunCommand(command)
 
 
+def RevertPreviouslyPatchedFiles():
+  print 'Reverting previously patched files'
+  files = [
+    '%(clang)s/test/Index/crash-recovery-modules.m',
+    '%(clang)s/unittests/libclang/LibclangTest.cpp',
+    '%(compiler_rt)s/lib/asan/asan_rtl.cc',
+    '%(compiler_rt)s/test/asan/TestCases/Linux/new_array_cookie_test.cc',
+    '%(llvm)s/test/DebugInfo/gmlt.ll',
+    '%(llvm)s/lib/CodeGen/SpillPlacement.cpp',
+    '%(llvm)s/lib/CodeGen/SpillPlacement.h',
+    '%(llvm)s/lib/Transforms/Instrumentation/MemorySanitizer.cpp',
+    '%(clang)s/test/Driver/env.c',
+    '%(clang)s/lib/Frontend/InitPreprocessor.cpp',
+    '%(clang)s/test/Frontend/exceptions.c',
+    '%(clang)s/test/Preprocessor/predefined-exceptions.m',
+    '%(llvm)s/test/Bindings/Go/go.test',
+    '%(clang)s/lib/Parse/ParseExpr.cpp',
+    '%(clang)s/lib/Parse/ParseTemplate.cpp',
+    '%(clang)s/lib/Sema/SemaDeclCXX.cpp',
+    '%(clang)s/lib/Sema/SemaExprCXX.cpp',
+    '%(clang)s/test/SemaCXX/default2.cpp',
+    '%(clang)s/test/SemaCXX/typo-correction-delayed.cpp',
+    '%(compiler_rt)s/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc',
+    '%(compiler_rt)s/test/tsan/signal_segv_handler.cc',
+    '%(compiler_rt)s/lib/sanitizer_common/sanitizer_coverage_libcdep.cc',
+    '%(compiler_rt)s/cmake/config-ix.cmake',
+    '%(compiler_rt)s/CMakeLists.txt',
+    '%(compiler_rt)s/lib/ubsan/ubsan_platform.h',
+    ]
+  for f in files:
+    f = f % {
+        'clang': CLANG_DIR,
+        'compiler_rt': COMPILER_RT_DIR,
+        'llvm': LLVM_DIR,
+        }
+    if os.path.exists(f):
+      os.remove(f)  # For unversioned files.
+      RunCommand(['svn', 'revert', f])
+
+
+def ApplyLocalPatches():
+  # There's no patch program on Windows by default.  We don't need patches on
+  # Windows yet, and maybe this not working on Windows will motivate us to
+  # remove patches over time.
+  assert sys.platform != 'win32'
+
+  # No patches.
+
+
 def DeleteChromeToolsShim():
+  OLD_SHIM_DIR = os.path.join(LLVM_DIR, 'tools', 'zzz-chrometools')
+  shutil.rmtree(OLD_SHIM_DIR, ignore_errors=True)
   shutil.rmtree(CHROME_TOOLS_SHIM_DIR, ignore_errors=True)
 
 
@@ -221,7 +295,8 @@ def AddCMakeToPath():
       if zip_name.endswith('.zip'):
         zipfile.ZipFile(f).extractall(path=LLVM_BUILD_TOOLS_DIR)
       else:
-        tarfile.open(mode='r:gz', fileobj=f).extractall(path=LLVM_BUILD_DIR)
+        tarfile.open(mode='r:gz', fileobj=f).extractall(path=
+            LLVM_BUILD_TOOLS_DIR)
   os.environ['PATH'] = cmake_dir + os.pathsep + os.environ.get('PATH', '')
 
 vs_version = None
@@ -267,8 +342,13 @@ def UpdateClang(args):
       try:
         DownloadUrl(cds_full_url, f)
         f.seek(0)
+        # TODO(thakis): Delete LLVM_BUILD_DIR before extracting.
         tarfile.open(mode='r:gz', fileobj=f).extractall(path=LLVM_BUILD_DIR)
         print 'clang %s unpacked' % PACKAGE_VERSION
+        # Download the gold plugin if requested to by an environment variable.
+        # This is used by the CFI ClusterFuzz bot.
+        if 'LLVM_DOWNLOAD_GOLD_PLUGIN' in os.environ:
+          RunCommand(['python', CHROMIUM_DIR+'/build/download_gold_plugin.py'])
         WriteStampFile(PACKAGE_VERSION)
         return 0
       except urllib2.HTTPError:
@@ -276,22 +356,63 @@ def UpdateClang(args):
 
   AddCMakeToPath()
 
-  DeleteChromeToolsShim();
+  RevertPreviouslyPatchedFiles()
+  DeleteChromeToolsShim()
+
   Checkout('LLVM', LLVM_REPO_URL + '/llvm/trunk', LLVM_DIR)
   Checkout('Clang', LLVM_REPO_URL + '/cfe/trunk', CLANG_DIR)
-  Checkout('LLD', LLVM_REPO_URL + '/lld/trunk', LLD_DIR)
+  if sys.platform == 'win32':
+    Checkout('LLD', LLVM_REPO_URL + '/lld/trunk', LLD_DIR)
   Checkout('compiler-rt', LLVM_REPO_URL + '/compiler-rt/trunk', COMPILER_RT_DIR)
-  CreateChromeToolsShim();
+  if sys.platform == 'darwin':
+    # clang needs a libc++ checkout, else -stdlib=libc++ won't find includes
+    # (i.e. this is needed for bootstrap builds).
+    Checkout('libcxx', LLVM_REPO_URL + '/libcxx/trunk', LIBCXX_DIR)
+    # While we're bundling our own libc++ on OS X, we need to compile libc++abi
+    # into it too (since OS X 10.6 doesn't have libc++abi.dylib either).
+    Checkout('libcxxabi', LLVM_REPO_URL + '/libcxxabi/trunk', LIBCXXABI_DIR)
 
-  # If building at head, define a macro that plugins can use for #ifdefing
-  # out code that builds at head, but not at CLANG_REVISION or vice versa.
-  cflags = cxxflags = ''
+  if args.with_patches and sys.platform != 'win32':
+    ApplyLocalPatches()
 
-  # If building at head, define a macro that plugins can use for #ifdefing
-  # out code that builds at head, but not at LLVM_WIN_REVISION or vice versa.
-  if use_head_revision:
-    cflags += ' -DLLVM_FORCE_HEAD_REVISION'
-    cxxflags += ' -DLLVM_FORCE_HEAD_REVISION'
+  cc, cxx = None, None
+  libstdcpp = None
+  if args.gcc_toolchain:  # This option is only used on Linux.
+    # Use the specified gcc installation for building.
+    cc = os.path.join(args.gcc_toolchain, 'bin', 'gcc')
+    cxx = os.path.join(args.gcc_toolchain, 'bin', 'g++')
+
+    if not os.access(cc, os.X_OK):
+      print 'Invalid --gcc-toolchain: "%s"' % args.gcc_toolchain
+      print '"%s" does not appear to be valid.' % cc
+      return 1
+
+    # Set LD_LIBRARY_PATH to make auxiliary targets (tablegen, bootstrap
+    # compiler, etc.) find the .so.
+    libstdcpp = subprocess.check_output(
+        [cxx, '-print-file-name=libstdc++.so.6']).rstrip()
+    os.environ['LD_LIBRARY_PATH'] = os.path.dirname(libstdcpp)
+
+  cflags = cxxflags = ldflags = []
+
+  # LLVM uses C++11 starting in llvm 3.5. On Linux, this means libstdc++4.7+ is
+  # needed, on OS X it requires libc++. clang only automatically links to libc++
+  # when targeting OS X 10.9+, so add stdlib=libc++ explicitly so clang can run
+  # on OS X versions as old as 10.7.
+  # TODO(thakis): Some bots are still on 10.6 (nacl...), so for now bundle
+  # libc++.dylib.  Remove this once all bots are on 10.7+, then use
+  # -DLLVM_ENABLE_LIBCXX=ON and change deployment_target to 10.7.
+  deployment_target = ''
+
+  if sys.platform == 'darwin':
+    # When building on 10.9, /usr/include usually doesn't exist, and while
+    # Xcode's clang automatically sets a sysroot, self-built clangs don't.
+    cflags = ['-isysroot', subprocess.check_output(
+        ['xcrun', '--show-sdk-path']).rstrip()]
+    cxxflags = ['-stdlib=libc++', '-nostdinc++',
+                '-I' + os.path.join(LIBCXX_DIR, 'include')] + cflags
+    if args.bootstrap:
+      deployment_target = '10.6'
 
   base_cmake_args = ['-GNinja',
                      '-DCMAKE_BUILD_TYPE=Release',
@@ -299,7 +420,6 @@ def UpdateClang(args):
                      '-DLLVM_ENABLE_THREADS=OFF',
                      ]
 
-  cc, cxx = None, None
   if args.bootstrap:
     print 'Building bootstrap compiler'
     if not os.path.exists(LLVM_BOOTSTRAP_DIR):
@@ -308,50 +428,147 @@ def UpdateClang(args):
     bootstrap_args = base_cmake_args + [
         '-DLLVM_TARGETS_TO_BUILD=host',
         '-DCMAKE_INSTALL_PREFIX=' + LLVM_BOOTSTRAP_INSTALL_DIR,
-        '-DCMAKE_C_FLAGS=' + cflags,
-        '-DCMAKE_CXX_FLAGS=' + cxxflags,
+        '-DCMAKE_C_FLAGS=' + ' '.join(cflags),
+        '-DCMAKE_CXX_FLAGS=' + ' '.join(cxxflags),
         ]
     if cc is not None:  bootstrap_args.append('-DCMAKE_C_COMPILER=' + cc)
     if cxx is not None: bootstrap_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
-    RunCommand(GetVSVersion().SetupScript('x64') +
-               ['&&', 'cmake'] + bootstrap_args + [LLVM_DIR])
-    RunCommand(GetVSVersion().SetupScript('x64') + ['&&', 'ninja'])
+    RunCommand(['cmake'] + bootstrap_args + [LLVM_DIR], msvc_arch='x64')
+    RunCommand(['ninja'], msvc_arch='x64')
     if args.run_tests:
-      RunCommand(GetVSVersion().SetupScript('x64') +
-                 ['&&', 'ninja', 'check-all'])
-    RunCommand(GetVSVersion().SetupScript('x64') + ['&&', 'ninja', 'install'])
-    # TODO(thakis): Set these to clang / clang++ on posix once this script
-    # is used on posix.
-    cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
-    cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
-    # CMake has a hard time with backslashes in compiler paths:
-    # https://stackoverflow.com/questions/13050827
-    cc = cc.replace('\\', '/')
-    cxx = cxx.replace('\\', '/')
+      RunCommand(['ninja', 'check-all'], msvc_arch='x64')
+    RunCommand(['ninja', 'install'], msvc_arch='x64')
+    if args.gcc_toolchain:
+      # Copy that gcc's stdlibc++.so.6 to the build dir, so the bootstrap
+      # compiler can start.
+      CopyFile(libstdcpp, os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'lib'))
+
+    if sys.platform == 'win32':
+      cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
+      cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
+      # CMake has a hard time with backslashes in compiler paths:
+      # https://stackoverflow.com/questions/13050827
+      cc = cc.replace('\\', '/')
+      cxx = cxx.replace('\\', '/')
+    else:
+      cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang')
+      cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang++')
+
+    if args.gcc_toolchain:
+      # Tell the bootstrap compiler to use a specific gcc prefix to search
+      # for standard library headers and shared object files.
+      cflags = ['--gcc-toolchain=' + args.gcc_toolchain]
+      cxxflags = ['--gcc-toolchain=' + args.gcc_toolchain]
     print 'Building final compiler'
 
+  if sys.platform == 'darwin':
+    # Build libc++.dylib while some bots are still on OS X 10.6.
+    libcxxbuild = os.path.join(LLVM_BUILD_DIR, 'libcxxbuild')
+    if os.path.isdir(libcxxbuild):
+      RmTree(libcxxbuild)
+    libcxxflags = ['-O3', '-std=c++11', '-fstrict-aliasing']
+
+    # libcxx and libcxxabi both have a file stdexcept.cpp, so put their .o files
+    # into different subdirectories.
+    os.makedirs(os.path.join(libcxxbuild, 'libcxx'))
+    os.chdir(os.path.join(libcxxbuild, 'libcxx'))
+    RunCommand(['c++', '-c'] + cxxflags + libcxxflags +
+                glob.glob(os.path.join(LIBCXX_DIR, 'src', '*.cpp')))
+
+    os.makedirs(os.path.join(libcxxbuild, 'libcxxabi'))
+    os.chdir(os.path.join(libcxxbuild, 'libcxxabi'))
+    RunCommand(['c++', '-c'] + cxxflags + libcxxflags +
+               glob.glob(os.path.join(LIBCXXABI_DIR, 'src', '*.cpp')) +
+               ['-I' + os.path.join(LIBCXXABI_DIR, 'include')])
+
+    os.chdir(libcxxbuild)
+    libdir = os.path.join(LIBCXX_DIR, 'lib')
+    RunCommand(['cc'] + glob.glob('libcxx/*.o') + glob.glob('libcxxabi/*.o') +
+        ['-o', 'libc++.1.dylib', '-dynamiclib', '-nodefaultlibs',
+         '-current_version', '1', '-compatibility_version', '1', '-lSystem',
+         '-install_name', '@executable_path/libc++.dylib',
+         '-Wl,-unexported_symbols_list,' + libdir + '/libc++unexp.exp',
+         '-Wl,-force_symbols_not_weak_list,' + libdir + '/notweak.exp',
+         '-Wl,-force_symbols_weak_list,' + libdir + '/weak.exp'])
+    if os.path.exists('libc++.dylib'):
+      os.remove('libc++.dylib')
+    os.symlink('libc++.1.dylib', 'libc++.dylib')
+    ldflags += ['-stdlib=libc++', '-L' + libcxxbuild]
+
+    if args.bootstrap:
+      # Now that the libc++ headers have been installed and libc++.dylib is
+      # built, delete the libc++ checkout again so that it's not part of the
+      # main build below -- the libc++(abi) tests don't pass on OS X in
+      # bootstrap builds (http://llvm.org/PR24068)
+      RmTree(LIBCXX_DIR)
+      RmTree(LIBCXXABI_DIR)
+      cxxflags = ['-stdlib=libc++', '-nostdinc++',
+                  '-I' + os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR,
+                                      'include/c++/v1')
+                  ] + cflags
+
   # Build clang.
   binutils_incdir = ''
   if sys.platform.startswith('linux'):
     binutils_incdir = os.path.join(BINUTILS_DIR, 'Linux_x64/Release/include')
 
+  # If building at head, define a macro that plugins can use for #ifdefing
+  # out code that builds at head, but not at LLVM_WIN_REVISION or vice versa.
+  if use_head_revision:
+    cflags += ['-DLLVM_FORCE_HEAD_REVISION']
+    cxxflags += ['-DLLVM_FORCE_HEAD_REVISION']
+
+  CreateChromeToolsShim()
+
+  deployment_env = None
+  if deployment_target:
+    deployment_env = os.environ.copy()
+    deployment_env['MACOSX_DEPLOYMENT_TARGET'] = deployment_target
+
   cmake_args = base_cmake_args + [
       '-DLLVM_BINUTILS_INCDIR=' + binutils_incdir,
-      '-DCMAKE_C_FLAGS=' + cflags,
-      '-DCMAKE_CXX_FLAGS=' + cxxflags,
+      '-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=WebAssembly',
+      '-DCMAKE_C_FLAGS=' + ' '.join(cflags),
+      '-DCMAKE_CXX_FLAGS=' + ' '.join(cxxflags),
+      '-DCMAKE_EXE_LINKER_FLAGS=' + ' '.join(ldflags),
+      '-DCMAKE_SHARED_LINKER_FLAGS=' + ' '.join(ldflags),
+      '-DCMAKE_MODULE_LINKER_FLAGS=' + ' '.join(ldflags),
+      '-DCMAKE_INSTALL_PREFIX=' + LLVM_BUILD_DIR,
       '-DCHROMIUM_TOOLS_SRC=%s' % os.path.join(CHROMIUM_DIR, 'tools', 'clang'),
       '-DCHROMIUM_TOOLS=%s' % ';'.join(args.tools)]
-  # TODO(thakis): Append this to base_cmake_args instead once compiler-rt
-  # can build with clang-cl (http://llvm.org/PR23698)
-  if cc is not None:  cmake_args.append('-DCMAKE_C_COMPILER=' + cc)
-  if cxx is not None: cmake_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
+  # TODO(thakis): Unconditionally append this to base_cmake_args instead once
+  # compiler-rt can build with clang-cl on Windows (http://llvm.org/PR23698)
+  cc_args = base_cmake_args if sys.platform != 'win32' else cmake_args
+  if cc is not None:  cc_args.append('-DCMAKE_C_COMPILER=' + cc)
+  if cxx is not None: cc_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
 
   if not os.path.exists(LLVM_BUILD_DIR):
     os.makedirs(LLVM_BUILD_DIR)
   os.chdir(LLVM_BUILD_DIR)
-  RunCommand(GetVSVersion().SetupScript('x64') +
-             ['&&', 'cmake'] + cmake_args + [LLVM_DIR])
-  RunCommand(GetVSVersion().SetupScript('x64') + ['&&', 'ninja', 'all'])
+  RunCommand(['cmake'] + cmake_args + [LLVM_DIR],
+             msvc_arch='x64', env=deployment_env)
+
+  if args.gcc_toolchain:
+    # Copy in the right stdlibc++.so.6 so clang can start.
+    if not os.path.exists(os.path.join(LLVM_BUILD_DIR, 'lib')):
+      os.mkdir(os.path.join(LLVM_BUILD_DIR, 'lib'))
+    libstdcpp = subprocess.check_output(
+        [cxx] + cxxflags + ['-print-file-name=libstdc++.so.6']).rstrip()
+    CopyFile(libstdcpp, os.path.join(LLVM_BUILD_DIR, 'lib'))
+
+  RunCommand(['ninja'], msvc_arch='x64')
+
+  if args.tools:
+    # If any Chromium tools were built, install those now.
+    RunCommand(['ninja', 'cr-install'], msvc_arch='x64')
+
+  if sys.platform == 'darwin':
+    CopyFile(os.path.join(LLVM_BUILD_DIR, 'libc++.1.dylib'),
+             os.path.join(LLVM_BUILD_DIR, 'bin'))
+    # See http://crbug.com/256342
+    RunCommand(['strip', '-x', os.path.join(LLVM_BUILD_DIR, 'bin', 'clang')])
+  elif sys.platform.startswith('linux'):
+    RunCommand(['strip', os.path.join(LLVM_BUILD_DIR, 'bin', 'clang')])
 
   # Do an x86 build of compiler-rt to get the 32-bit ASan run-time.
   # TODO(hans): Remove once the regular build above produces this.
@@ -360,23 +577,34 @@ def UpdateClang(args):
   os.chdir(COMPILER_RT_BUILD_DIR)
   # TODO(thakis): Add this once compiler-rt can build with clang-cl (see
   # above).
-  #if args.bootstrap:
+  #if args.bootstrap and sys.platform == 'win32':
     # The bootstrap compiler produces 64-bit binaries by default.
-    #cflags += ' -m32'
-    #cxxflags += ' -m32'
+    #cflags += ['-m32']
+    #cxxflags += ['-m32']
   compiler_rt_args = base_cmake_args + [
-      '-DCMAKE_C_FLAGS=' + cflags,
-      '-DCMAKE_CXX_FLAGS=' + cxxflags]
-  RunCommand(GetVSVersion().SetupScript('x86') +
-             ['&&', 'cmake'] + compiler_rt_args + [LLVM_DIR])
-  RunCommand(GetVSVersion().SetupScript('x86') + ['&&', 'ninja', 'compiler-rt'])
+      '-DCMAKE_C_FLAGS=' + ' '.join(cflags),
+      '-DCMAKE_CXX_FLAGS=' + ' '.join(cxxflags)]
+  if sys.platform != 'win32':
+    compiler_rt_args += ['-DLLVM_CONFIG_PATH=' +
+                         os.path.join(LLVM_BUILD_DIR, 'bin', 'llvm-config'),
+                        '-DSANITIZER_MIN_OSX_VERSION="10.7"']
+  RunCommand(['cmake'] + compiler_rt_args + [LLVM_DIR],
+              msvc_arch='x86', env=deployment_env)
+  RunCommand(['ninja', 'compiler-rt'], msvc_arch='x86')
 
   # TODO(hans): Make this (and the .gypi and .isolate files) version number
   # independent.
+  if sys.platform == 'win32':
+    platform = 'windows'
+  elif sys.platform == 'darwin':
+    platform = 'darwin'
+  else:
+    assert sys.platform.startswith('linux')
+    platform = 'linux'
   asan_rt_lib_src_dir = os.path.join(COMPILER_RT_BUILD_DIR, 'lib', 'clang',
-                                     VERSION, 'lib', 'windows')
+                                     VERSION, 'lib', platform)
   asan_rt_lib_dst_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang',
-                                     VERSION, 'lib', 'windows')
+                                     VERSION, 'lib', platform)
   CopyDirectoryContents(asan_rt_lib_src_dir, asan_rt_lib_dst_dir,
                         r'^.*-i386\.lib$')
   CopyDirectoryContents(asan_rt_lib_src_dir, asan_rt_lib_dst_dir,
@@ -385,19 +613,20 @@ def UpdateClang(args):
   CopyFile(os.path.join(asan_rt_lib_src_dir, '..', '..', 'asan_blacklist.txt'),
            os.path.join(asan_rt_lib_dst_dir, '..', '..'))
 
-  # Make an extra copy of the sanitizer headers, to be put on the include path
-  # of the fallback compiler.
-  sanitizer_include_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang', VERSION,
-                                       'include', 'sanitizer')
-  aux_sanitizer_include_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang',
-                                           VERSION, 'include_sanitizer',
-                                           'sanitizer')
-  if not os.path.exists(aux_sanitizer_include_dir):
-    os.makedirs(aux_sanitizer_include_dir)
-  for _, _, files in os.walk(sanitizer_include_dir):
-    for f in files:
-      CopyFile(os.path.join(sanitizer_include_dir, f),
-               aux_sanitizer_include_dir)
+  if sys.platform == 'win32':
+    # Make an extra copy of the sanitizer headers, to be put on the include path
+    # of the fallback compiler.
+    sanitizer_include_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang',
+                                         VERSION, 'include', 'sanitizer')
+    aux_sanitizer_include_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang',
+                                             VERSION, 'include_sanitizer',
+                                             'sanitizer')
+    if not os.path.exists(aux_sanitizer_include_dir):
+      os.makedirs(aux_sanitizer_include_dir)
+    for _, _, files in os.walk(sanitizer_include_dir):
+      for f in files:
+        CopyFile(os.path.join(sanitizer_include_dir, f),
+                 aux_sanitizer_include_dir)
 
   # Run tests.
   if args.run_tests or use_head_revision:
@@ -447,22 +676,28 @@ def main():
                       help="run only if the script thinks clang is needed")
   parser.add_argument('--force-local-build', action='store_true',
                       help="don't try to download prebuild binaries")
+  parser.add_argument('--gcc-toolchain', help='set the version for which gcc '
+                      'version be used for building; --gcc-toolchain=/opt/foo '
+                      'picks /opt/foo/bin/gcc')
   parser.add_argument('--print-revision', action='store_true',
                       help='print current clang revision and exit.')
+  parser.add_argument('--print-clang-version', action='store_true',
+                      help='print current clang version (e.g. x.y.z) and exit.')
   parser.add_argument('--run-tests', action='store_true',
                       help='run tests after building; only for local builds')
   parser.add_argument('--tools', nargs='*',
                       help='select which chrome tools to build',
                       default=['plugins', 'blink_gc_plugin'])
+  parser.add_argument('--without-patches', action='store_false',
+                      help="don't apply patches (default)", dest='with_patches',
+                      default=True)
+
   # For now, these flags are only used for the non-Windows flow, but argparser
   # gets mad if it sees a flag it doesn't recognize.
   parser.add_argument('--no-stdin-hack', action='store_true')
 
   args = parser.parse_args()
 
-  if re.search(r'\b(make_clang_dir)=', os.environ.get('GYP_DEFINES', '')):
-    print 'Skipping Clang update (make_clang_dir= was set in GYP_DEFINES).'
-    return 0
   if args.if_needed:
     is_clang_required = False
     # clang is always used on Mac and Linux.
@@ -478,6 +713,9 @@ def main():
       is_clang_required = True
     if not is_clang_required:
       return 0
+    if re.search(r'\b(make_clang_dir)=', os.environ.get('GYP_DEFINES', '')):
+      print 'Skipping Clang update (make_clang_dir= was set in GYP_DEFINES).'
+      return 0
 
   global LLVM_WIN_REVISION, PACKAGE_VERSION
   if args.print_revision:
@@ -487,12 +725,25 @@ def main():
       print PACKAGE_VERSION
     return 0
 
-  if LLVM_WIN_REVISION == 'HEAD':
+  if args.print_clang_version:
+    sys.stdout.write(VERSION)
+    return 0
+
+  # Don't buffer stdout, so that print statements are immediately flushed.
+  # Do this only after --print-revision has been handled, else we'll get
+  # an error message when this script is run from gn for some reason.
+  sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
+
+  if use_head_revision:
     # Use a real revision number rather than HEAD to make sure that the stamp
     # file logic works.
     LLVM_WIN_REVISION = GetSvnRevision(LLVM_REPO_URL)
     PACKAGE_VERSION = LLVM_WIN_REVISION + '-0'
 
+    args.force_local_build = True
+    # Skip local patches when using HEAD: they probably don't apply anymore.
+    args.with_patches = False
+
   return UpdateClang(args)