Set CC to clang when GYP_DEFINES=clang=1.

build/common.gypi

 # Copyright (c) 2011 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 1658 matching lines @@
             '-Wno-unused-parameter',
             # Don't warn about the "struct foo f = {0};" initialization
             # pattern.
             '-Wno-missing-field-initializers',
           ],
           'conditions': [
             ['chromium_mac_pch', {'GCC_PRECOMPILE_PREFIX_HEADER': 'YES'},
                                  {'GCC_PRECOMPILE_PREFIX_HEADER': 'NO'}
             ],
             ['clang==1', {
+              'CC': '$(SOURCE_ROOT)/<(clang_dir)/clang',
+              'LDPLUSPLUS': '$(SOURCE_ROOT)/<(clang_dir)/clang++',

[Evan Martin, 2011/09/06 17:41:16]

Where does SOURCE_ROOT come from?

[Nico, 2011/09/06 17:47:08]

I think it's one of the many magic environment variables that xcode sets when
building, see
http://developer.apple.com/library/mac/#documentation/DeveloperTools/Referenc...

+              'GCC_VERSION': 'com.apple.compilers.llvm.clang.1_0',
               'WARNING_CFLAGS': [
                 '-Wheader-hygiene',
                 # Don't die on dtoa code that uses a char as an array index.
                 # This is required solely for base/third_party/dmg_fp/dtoa.cc.
                 '-Wno-char-subscripts',
                 # Clang spots more unused functions.
                 '-Wno-unused-function',
                 # See comments on this flag higher up in this file.
                 '-Wno-unnamed-type-template-args',
                 # TODO(thakis): Reenable once the one instance this warns on
                 # is fixed.
                 '-Wno-parentheses',
               ],
             }],
             ['clang==1 and clang_use_chrome_plugins==1', {
               'OTHER_CFLAGS': [
                 '<(clang_chrome_plugins_flags)',
               ],
             }],
             ['clang==1 and clang_load!="" and clang_add_plugin!=""', {
               'OTHER_CFLAGS': [
                 '-Xclang', '-load', '-Xclang', '<(clang_load)',
                 '-Xclang', '-add-plugin', '-Xclang', '<(clang_add_plugin)',
               ],
             }],
           ],
         },
+        'conditions': [
+          ['clang==1', {
+            'variables': {
+              'clang_dir': '../third_party/llvm-build/Release+Asserts/bin',
+            },
+          }],
+        ],
         'target_conditions': [
           ['_type!="static_library"', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
           }],
           ['_mac_bundle', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-ObjC']},
           }],
           ['_type=="executable"', {
             'postbuilds': [
               {
@@ skipping 287 matching lines @@
         },
       },
     }],
     ['enable_new_npdevice_api==1', {
       'target_defaults': {
         'defines': [
           'ENABLE_NEW_NPDEVICE_API',
         ],
       },
     }],
+    ['clang==1', {
+      'make_global_settings': [
+        ['CC', 'third_party/llvm-build/Release+Asserts/bin/clang'],
+        ['CXX', 'third_party/llvm-build/Release+Asserts/bin/clang++'],
+        ['LINK', 'third_party/llvm-build/Release+Asserts/bin/clang++'],

[Mark Mentovai, 2011/09/07 01:36:24]

This is fine for now.

We’ll need to split this up in the same way that Xcode does in order to migrate
the official build to make, so that make doesn’t link C-only programs as C++.

+        ['CC.host', '$(CC)'],
+        ['CXX.host', '$(CXX)'],
+        ['LINK.host', '$(LINK)'],
+      ],
+    }],
   ],
   'xcode_settings': {
     # DON'T ADD ANYTHING NEW TO THIS BLOCK UNLESS YOU REALLY REALLY NEED IT!
     # This block adds *project-wide* configuration settings to each project
     # file.  It's almost always wrong to put things here.  Specify your
     # custom xcode_settings in target_defaults to add them to targets instead.
 
     # In an Xcode Project Info window, the "Base SDK for All Configurations"
     # setting sets the SDK on a project-wide basis.  In order to get the
     # configured SDK to show properly in the Xcode UI, SDKROOT must be set
     # here at the project level.
     'SDKROOT': 'macosx<(mac_sdk)',  # -isysroot
 
     # The Xcode generator will look for an xcode_settings section at the root
     # of each dict and use it to apply settings on a file-wide basis.  Most
     # settings should not be here, they should be in target-specific
     # xcode_settings sections, or better yet, should use non-Xcode-specific
     # 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',
   },
 }