Start massaging the GYP files for building with clang on Windows

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 1905 matching lines @@
       ['OS=="win" and use_goma==1', {
         # goma doesn't support pch yet.
         'chromium_win_pch': 0,
         # goma doesn't support PDB yet, so win_z7=1 or fastbuild=1.
         'conditions': [
           ['fastbuild==0', {
             'win_z7': 1,
           }],
         ],
       }],
+
+      ['OS=="win" and clang==1', {
+        'chromium_win_pch': 0,
+      }],
+
       # The seccomp-bpf sandbox is only supported on three architectures
       # currently.
       # Do not disable seccomp_bpf anywhere without talking to
       # security@chromium.org!
       ['((OS=="linux" or OS=="android") and '
            '(target_arch=="ia32" or target_arch=="x64" or '
              'target_arch=="arm"))', {
          'use_seccomp_bpf%': 1,
       }, {
          'use_seccomp_bpf%': 0,
@@ skipping 608 matching lines @@
                 'WarnAsError': '<(win_third_party_warn_as_error)',
                 'Detect64BitPortabilityProblems': 'false',
               },
             },
             'conditions': [
               ['buildtype=="Official"', {
                 'msvs_settings': {
                   'VCCLCompilerTool': { 'WarnAsError': 'false' },
                 }
               }],
+              ['clang==1', {
+                'msvs_settings': {
+                  'VCCLCompilerTool': { 'WarnAsError': 'false' },
+                }
+              }],
             ],
           }],
           # TODO(darin): Unfortunately, some third_party code depends on base.
           [ 'OS=="win" and component=="shared_library"', {
             'msvs_disabled_warnings': [
               4251,  # class 'std::xx' needs to have dll-interface.
             ],
           }],
           [ 'OS=="mac" or OS=="ios"', {
             'xcode_settings': {
@@ skipping 2086 matching lines @@
               'VCManifestTool': {
                 'EmbedManifest': 'true',
               }
             }],
             ['_type=="executable" and >(win_use_external_manifest)==1', {
               'VCManifestTool': {
                 'EmbedManifest': 'false',
               }
             }],
           ],
+          'conditions': [
+            ['clang==1', {
+              'VCCLCompilerTool': {
+                'WarnAsError': 'false',
+                'RuntimeTypeInfo': 'false',
+                'AdditionalOptions': [
+                  '/fallback',
+
+                  # Many files use intrinsics without including this header.
+                  # TODO(hans): Fix those files, or move this to sub-GYPs.
+                  '/FIIntrin.h',
+
+                  # TODO(hans): Make this list shorter eventually.

[Reid Kleckner, 2014/01/24 00:38:33]

Why turn these off if we've turned off -WX / -Werror?  Are these just the
noisiest?  I noticed -Wmsvc-include is far too noisy due to
http://llvm.org/PR18481, but the rest are probably true positives.

[hans, 2014/01/24 00:54:03]

It gets really noisy if I leave them on. I considered -Wno-everything, but I
figured that tracking and addressing these explicitly would be nice.

A lot of the noise is coming from third-party code that's inconvenient to
change, so the flags should move to the respective GYP-files for those
sub-projects, but I consider that part of the TODO here.

+                  '-Qunused-arguments',
+                  '-Wno-c++11-compat-deprecated-writable-strings',
+                  '-Wno-char-subscripts',
+                  '-Wno-deprecated-declarations',
+                  '-Wno-deprecated-register',
+                  '-Wno-empty-body',
+                  '-Wno-enum-conversion',
+                  '-Wno-incompatible-pointer-types',
+                  '-Wno-logical-op-parentheses',
+                  '-Wno-microsoft',
+                  '-Wno-missing-braces',
+                  '-Wno-msvc-include',
+                  '-Wno-null-dereference',
+                  '-Wno-overloaded-virtual',
+                  '-Wno-parentheses',
+                  '-Wno-pointer-sign',
+                  '-Wno-reorder',
+                  '-Wno-return-type-c-linkage',
+                  '-Wno-self-assign',
+                  '-Wno-switch',
+                  '-Wno-tautological-compare',
+                  '-Wno-unknown-pragmas',
+                  '-Wno-unsequenced',
+                  '-Wno-unused-function',
+                  '-Wno-unused-private-field',
+                  '-Wno-unused-value',
+                  '-Wno-unused-variable',
+                  '-ferror-limit=1',
+                ],
+              },
+            }],
+          ],
         },
       },
     }],
     ['disable_nacl==1', {
       'target_defaults': {
         'defines': [
           'DISABLE_NACL',
         ],
       },
     }],
@@ skipping 163 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }