Add PRESUBMIT check for #ifdefs on values that are always defined.

PRESUBMIT.py

 # 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 1265 matching lines @@
   results.extend(_CheckNoTrinaryTrueFalse(input_api, output_api))
   results.extend(_CheckUnwantedDependencies(input_api, output_api))
   results.extend(_CheckFilePermissions(input_api, output_api))
   results.extend(_CheckNoAuraWindowPropertyHInHeaders(input_api, output_api))
   results.extend(_CheckIncludeOrder(input_api, output_api))
   results.extend(_CheckForVersionControlConflicts(input_api, output_api))
   results.extend(_CheckPatchFiles(input_api, output_api))
   results.extend(_CheckHardcodedGoogleHostsInLowerLayers(input_api, output_api))
   results.extend(_CheckNoAbbreviationInPngFileName(input_api, output_api))
   results.extend(_CheckForInvalidOSMacros(input_api, output_api))
+  results.extend(_CheckForInvalidIfDefinedMacros(input_api, output_api))
   results.extend(_CheckAddedDepsHaveTargetApprovals(input_api, output_api))
   results.extend(
       input_api.canned_checks.CheckChangeHasNoTabs(
           input_api,
           output_api,
           source_file_filter=lambda x: x.LocalPath().endswith('.grd')))
   results.extend(_CheckSpamLogging(input_api, output_api))
   results.extend(_CheckForAnonymousVariables(input_api, output_api))
   results.extend(_CheckCygwinShell(input_api, output_api))
   results.extend(_CheckUserActionUpdate(input_api, output_api))
@@ skipping 90 matching lines @@
     if not f.LocalPath().endswith(('.py', '.js', '.html', '.css')):
       bad_macros.extend(_CheckForInvalidOSMacrosInFile(input_api, f))
 
   if not bad_macros:
     return []
 
   return [output_api.PresubmitError(
       'Possibly invalid OS macro[s] found. Please fix your code\n'
       'or add your macro to src/PRESUBMIT.py.', bad_macros)]
 
+
+def _CheckForInvalidIfDefinedMacrosInFile(input_api, f):
+  """Check all affected files for invalid "if defined" macros."""
+  ALWAYS_DEFINED_MACROS = (
+      "TARGET_IPHONE_SIMULATOR",

[stuartmorgan, 2014/09/25 23:42:32]

From TargetConditionals.h, I'd suggest we also add TARGET_OS_MAC,
TARGET_OS_IPHONE, and TARGET_CPU_*. At least the OS one has bitten me before.

[lliabraa, 2014/09/26 18:22:43]

Done. I added all the CPU and OS defines

+  )
+  preprocessor_statement = input_api.re.compile(r'^\s*#')
+  ifdef_macro = input_api.re.compile(r'(ifdef\s|defined\()([^\s\)]+)')

[stuartmorgan, 2014/09/25 23:42:32]

Why separate regexes, vs ^\s*#.*(ifdef|defined\() ... ? Is it to catch multiple
violations on the same line in one pass instead of two? (I'm not sure it's worth
it since this won't work with sufficiently long ifs anyway, since after one or
two you run out of room and continue with \)

Also, if you aren't using match group one you can replace () with (?:) to make
it a non-capturing group.

[lliabraa, 2014/09/26 18:22:43]

I copied that bit from _CheckForInvalidOSMacrosInFile, but your single regex
works just as well. Thx.
Done.

+  results = []
+  for lnum, line in f.ChangedContents():
+    if preprocessor_statement.search(line):
+      for match in ifdef_macro.finditer(line):
+        if match.group(2) in ALWAYS_DEFINED_MACROS:
+          always_defined = ' %s is always defined. ' % match.group(2)
+          did_you_mean = 'Did you mean \'#if %s\'?' % match.group(2)
+          results.append('    %s:%d %s\n\t%s' % (f.LocalPath(),
+                                             lnum,
+                                             always_defined,
+                                             did_you_mean))
+  return results
+
+
+def _CheckForInvalidIfDefinedMacros(input_api, output_api):
+  """Check all affected files for invalid "if defined" macros."""
+  bad_macros = []
+  for f in input_api.AffectedFiles():
+    if f.LocalPath().endswith(('.h', '.c', '.cc', '.m', '.mm')):
+      bad_macros.extend(_CheckForInvalidIfDefinedMacrosInFile(input_api, f))
+
+  if not bad_macros:
+    return []
+
+  return [output_api.PresubmitError(
+      'Possibly invalid if defined macro[s] found. Please fix your code\n'
+      'or add your macro to src/PRESUBMIT.py.', bad_macros)]

[stuartmorgan, 2014/09/25 23:42:32]

Where would they add it to fix the error?

[lliabraa, 2014/09/26 18:22:43]

Done. I've changed this text a bit. If the ifdef is intentional then they
probably need to remove the macro from the of always defined macros.

+
+
 def _CheckForIPCRules(input_api, output_api):
   """Check for same IPC rules described in
   http://www.chromium.org/Home/chromium-security/education/security-tips-for-ipc
   """
   base_pattern = r'IPC_ENUM_TRAITS\('
   inclusion_pattern = input_api.re.compile(r'(%s)' % base_pattern)
   comment_pattern = input_api.re.compile(r'//.*(%s)' % base_pattern)
 
   problems = []
   for f in input_api.AffectedSourceFiles(None):
@@ skipping 241 matching lines @@
     builders.extend(['cros_x86'])
 
   # The AOSP bot doesn't build the chrome/ layer, so ignore any changes to it
   # unless they're .gyp(i) files as changes to those files can break the gyp
   # step on that bot.
   if (not all(re.search('^chrome', f) for f in files) or
       any(re.search('\.gypi?$', f) for f in files)):
     builders.extend(['android_aosp'])
 
   return GetDefaultTryConfigs(builders)