clang update script: Verify that VERSION is correct.

tools/clang/scripts/update.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """This script is used to download prebuilt clang binaries.
 
 It is also used by package.py to build the prebuilt clang binaries."""
 
 import argparse
@@ skipping 355 matching lines @@
   return vs_version
 
 
 def CopyDiaDllTo(target_dir):
   # This script always wants to use the 64-bit msdia*.dll.
   dia_path = os.path.join(GetVSVersion().Path(), 'DIA SDK', 'bin', 'amd64')
   dia_dll = os.path.join(dia_path, DIA_DLL[GetVSVersion().ShortName()])
   CopyFile(dia_dll, target_dir)
 
 
+def VeryifyVersionOfBuiltClangMatchesVERSION():
+  """Checks that `clang --version` outputs VERSION.  If this fails, VERSION
+  in this file is out-of-date and needs to be updated (possibly in an
+  `if use_head_revision:` block in main() first)."""
+  clang = os.path.join(LLVM_BUILD_DIR, 'bin', 'clang')
+  if sys.platform == 'win32':
+    # TODO: Parse `clang-cl /?` output for built clang's version and check that
+    # to check the binary we're actually shipping? But clang-cl.exe is just
+    # a copy of clang.exe, so this does check the same thing.
+    clang += '.exe'

[hans, 2016/08/08 18:54:00]

Yeah, I think checking clang is good enough.

If we *really* wanted to, we could do "clang-cl.exe --driver-mode=gcc", which we
could pass --version too and it will behave just like clang.exe. But that also
seems like a lot of hoops to jump through.

+  version_out = subprocess.check_output([clang, '--version'])
+  version_out = re.match(r'clang version (\S+)', version_out).group(1)

[hans, 2016/08/08 18:54:00]

Sorry, I should have mentioned this the first time: Perhaps \S might be too
broad? Could we check for [0-9.]+ instead?

[Nico, 2016/08/08 19:00:31]

Does it matter if we compare to VERSION later? If it always matches too much
we'll find out then. But I can make it [0-9.] too if you think it' s important.

[hans, 2016/08/08 19:27:32]

I figured if for whatever reason clang starts printing "4.0.0-trunk" instead of
just "4.0.0" or whatever, that would unnecessarily break this test. Sure we'd
catch it, but it would be annoying.

[Nico, 2016/08/08 20:26:20]

Hm, I think I'd prefer if this turned red in that case (maybe the headers are
now in include/clang/4.0.0-trunk too) so we'd catch if this changes in
surprising ways.

But I also think it's less important than the time we're going to spend arguing
about this, so done :-)

+  if version_out != VERSION:
+    print ('unexpected clang version %s (not %s), update VERSION in update.py'
+           % (version_out, VERSION))
+    sys.exit(1)
+
+
 def UpdateClang(args):
   print 'Updating Clang to %s...' % PACKAGE_VERSION
 
   need_gold_plugin = 'LLVM_DOWNLOAD_GOLD_PLUGIN' in os.environ or (
       sys.platform.startswith('linux') and
       'buildtype=Official' in os.environ.get('GYP_DEFINES', '') and
       'branding=Chrome' in os.environ.get('GYP_DEFINES', ''))
 
   if ReadStampFile() == PACKAGE_VERSION and not args.force_local_build:
     print 'Clang is already up to date.'
@@ skipping 255 matching lines @@
   if args.tools:
     # If any Chromium tools were built, install those now.
     RunCommand(['ninja', 'cr-install'], msvc_arch='x64')
 
   if sys.platform == 'darwin':
     # 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')])
 
-  # TODO(thakis): Check that `clang --version` matches VERSION.
+  VeryifyVersionOfBuiltClangMatchesVERSION()
 
   # Do an out-of-tree build of compiler-rt.
   # On Windows, this is used to get the 32-bit ASan run-time.
   # TODO(hans): Remove once the regular build above produces this.
   # On Mac and Linux, this is used to get the regular 64-bit run-time.
   # Do a clobbered build due to cmake changes.
   if os.path.isdir(COMPILER_RT_BUILD_DIR):
     RmTree(COMPILER_RT_BUILD_DIR)
   os.makedirs(COMPILER_RT_BUILD_DIR)
   os.chdir(COMPILER_RT_BUILD_DIR)
@@ skipping 218 matching lines @@
     args.force_local_build = True
     if 'OS=android' not in os.environ.get('GYP_DEFINES', ''):
       # Only build the Android ASan rt on ToT bots when targetting Android.
       args.with_android = False
 
   return UpdateClang(args)
 
 
 if __name__ == '__main__':
   sys.exit(main())