clang update script: Verify that VERSION is correct.

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 520903da26edbcb221866d9224268d27b6cc97a6..54a166f5c5ce39f3ad76d528c5e23723d5dcc3ee 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -373,6 +373,23 @@ def CopyDiaDllTo(target_dir):
   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+  in this file is out-of-date and needs to be updated (possibly in an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)."""
+  if sys.platform == 'win32':
+    # FIXME: Parse `clang-cl /?` output for built clang's version and check

[hans, 2016/08/08 16:11:23]

Doesn't the code below work on Windows too? Regular clang.exe is still there.

[Nico, 2016/08/08 17:01:32]

That's a good point. I figured it'd be nicer to get it from the binary we're
actually shipping, but going to clang.exe is probably better than doing nothing
on Windows (though as soon as this runs on any one platform it'll do its
purpose). Let me upload a new patch...

+    pass
+  else:
+    clang = os.path.join(LLVM_BUILD_DIR, 'bin', 'clang')
+    version_out = subprocess.check_output([clang, '--version'])
+    version_out = re.match(r'clang version (\S+)', version_out).group(1)
+    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
 
@@ -648,7 +665,7 @@ def UpdateClang(args):
   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.