Use clang as default host compiler when cross-compiling

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 525 matching lines @@
       #
       # This variable may be explicitly set to 1 (enabled) or 0
       # (disabled) in ~/.gyp/include.gypi or via the GYP command line.
       # This setting will override the default.
       #
       # See
       # http://code.google.com/p/chromium/wiki/WindowsPrecompiledHeaders
       # for details.
       'chromium_win_pch%': 0,
 
+      # Clang stuff.
+      'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',
       # Set this to true when building with Clang.
       # See http://code.google.com/p/chromium/wiki/Clang for details.
+      # If this is set, clang is used as both host and target compiler in
+      # cross-compile builds.
       'clang%': 0,
 
       # Enable plug-in installation by default.
       'enable_plugin_installation%': 1,
 
       # Specifies whether to use canvas_skia.cc in place of platform
       # specific implementations of gfx::Canvas. Affects text drawing in the
       # Chrome UI.
       # TODO(asvitkine): Enable this on all platforms and delete this flag.
       #                  http://crbug.com/105550
@@ skipping 39 matching lines @@
       'syzygy_optimize%': 0,
 
       # Enable hole punching for the protected video.
       'video_hole%': 0,
 
       # Automatically select platforms under ozone. Turn this off to
       # build only explicitly selected platforms.
       'ozone_auto_platforms%': 1,
 
       'conditions': [
+        ['android_webview_build==0', {
+          # If this is set clang is used as host compiler, but not as target
+          # compiler. Always do this by default, except when building for AOSP.
+          'host_clang%': 1,
+        }, {
+          # See http://crbug.com/377684
+          'host_clang%': 0,
+        }],
         # A flag for POSIX platforms
         ['OS=="win"', {
           'os_posix%': 0,
         }, {
           'os_posix%': 1,
         }],
 
         # A flag for BSD platforms
         ['OS=="freebsd" or OS=="openbsd"', {
           'os_bsd%': 1,
@@ skipping 630 matching lines @@
 
     # Experimental setting to break chrome.dll into multiple pieces based on
     # process type.
     'chrome_multiple_dll%': '0',
 
     # Experimental setting to optimize Chrome's DLLs with PGO.
     'chrome_pgo_phase%': '0',
 
     # Clang stuff.
     'clang%': '<(clang)',
-    'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',
+    'host_clang%': '<(host_clang)',
+    'make_clang_dir%': '<(make_clang_dir)',
 
     # Control which version of clang to use when building for iOS.  If set to
     # '1', uses the version of clang that ships with Xcode.  If set to '0', uses
     # the version of clang that ships with the Chromium source.  This variable
     # is automatically set to '1' when using the Xcode generator.
     'clang_xcode%': 0,
 
     # These two variables can be set in GYP_DEFINES while running
     # |gclient runhooks| to let clang run a plugin in every compilation.
     # Only has an effect if 'clang=1' is in GYP_DEFINES as well.
@@ skipping 998 matching lines @@
           ['win_z7==0', {
             'fastbuild': 1,
           }],
         ],
       }],
 
       ['OS=="win" and (clang==1 or asan==1)', {
         'chromium_win_pch': 0,
       }],
 
+      ['host_clang==1', {
+        'host_cc': '<(make_clang_dir)/bin/clang',
+        'host_cxx': '<(make_clang_dir)/bin/clang++',
+      }, {
+        'host_cc': '<!(which gcc)',
+        'host_cxx': '<!(which g++)',
+      }],
+
       # The seccomp-bpf sandbox is only supported on four 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" or target_arch=="mipsel"))', {
          'use_seccomp_bpf%': 1,
       }, {
          'use_seccomp_bpf%': 0,
@@ skipping 1614 matching lines @@
             'cflags': [
               # TODO(thakis): Remove, http://crbug.com/263960
               '-Wno-reserved-user-defined-literal',
             ],
             'cflags_cc': [
               # See the comment in the Mac section for what it takes to move
               # this to -std=c++11.
               '-std=gnu++11',
             ],
           }],
+          ['clang==0 and host_clang==1', {
+            'target_conditions': [
+              ['_toolset=="host"', {
+                'cflags_cc': [ '-std=gnu++11', ],
+              }],
+            ],
+          }],
           ['clang==1 and clang_use_chrome_plugins==1', {
             'cflags': [
               '<@(clang_chrome_plugins_flags)',
             ],
           }],
           ['clang==1 and clang_load!=""', {
             'cflags': [
               '-Xclang', '-load', '-Xclang', '<(clang_load)',
             ],
           }],
@@ skipping 327 matching lines @@
                 'cflags_cc': [
                   '-std=gnu++11',
                   # See comment for -Wno-c++11-narrowing.
                   '-Wno-narrowing',
                   # TODO(thakis): Remove, http://crbug.com/263960
                   '-Wno-literal-suffix',
                 ],
               }],
             ],
           }],
-          ['host_gcc_version>=47 and clang==0', {
+          ['host_gcc_version>=47 and clang==0 and host_clang==0', {
             'target_conditions': [
               ['_toolset=="host"', {
                 'cflags_cc': [
                   '-std=gnu++11',
                   # See comment for -Wno-c++11-narrowing.
                   '-Wno-narrowing',
                   # TODO(thakis): Remove, http://crbug.com/263960
                   '-Wno-literal-suffix',
                 ],
               }],
@@ skipping 1243 matching lines @@
     # Don't warn about the "typedef 'foo' locally defined but not used"
     # for gcc 4.8.
     # TODO: remove this flag once all builds work. See crbug.com/227506
     ['gcc_version>=48 and clang==0', {
       'target_defaults': {
         'cflags': [
           '-Wno-unused-local-typedefs',
         ],
       },
     }],
+    ['gcc_version>=48 and clang==0 and host_clang==1', {
+      'target_defaults': {
+        'target_conditions': [
+          ['_toolset=="host"', { 'cflags!': [ '-Wno-unused-local-typedefs' ]}],
+        ],
+      },
+    }],
     # We need a special case to handle the android webview build on mac because
     # the host gcc there doesn't accept this flag, but the target gcc may
     # require it.
     ['gcc_version>=48 and android_webview_build==1 and host_os=="mac"', {
       'target_defaults': {
         'target_conditions': [
           ['_toolset=="host"', {
             'cflags!': [
               '-Wno-unused-local-typedefs',
             ],
@@ skipping 15 matching lines @@
         # On Windows, gyp's ninja generator only looks at CC.
         ['CC', '<(make_clang_dir)/bin/clang-cl'],
       ],
     }],
     ['OS=="android" and clang==0', {
       # Hardcode the compiler names in the Makefile so that
       # it won't depend on the environment at make time.
       'make_global_settings': [
         ['CC', '<!(/bin/echo -n <(android_toolchain)/*-gcc)'],
         ['CXX', '<!(/bin/echo -n <(android_toolchain)/*-g++)'],
-        ['CC.host', '<!(which gcc)'],
-        ['CXX.host', '<!(which g++)'],
+        ['CC.host', '<(host_cc)'],
+        ['CXX.host', '<(host_cxx)'],
       ],
     }],
     ['OS=="linux" and target_arch=="mipsel"', {
       'make_global_settings': [
         ['CC', '<(sysroot)/../bin/mipsel-linux-gnu-gcc'],
         ['CXX', '<(sysroot)/../bin/mipsel-linux-gnu-g++'],
-        ['CC.host', '<!(which gcc)'],
-        ['CXX.host', '<!(which g++)'],
+        ['CC.host', '<(host_cc)'],
+        ['CXX.host', '<(host_cxx)'],
       ],
     }],
     ['OS=="linux" and target_arch=="arm" and host_arch!="arm" and chromeos==0 and clang==0', {
       # Set default ARM cross compiling on linux.  These can be overridden
       # using CC/CXX/etc environment variables.
       'make_global_settings': [
         ['CC', '<!(which arm-linux-gnueabihf-gcc)'],
         ['CXX', '<!(which arm-linux-gnueabihf-g++)'],
-        ['CC.host', '<!(which gcc)'],
-        ['CXX.host', '<!(which g++)'],
+        ['CC.host', '<(host_cc)'],
+        ['CXX.host', '<(host_cxx)'],
       ],
     }],
 
     # TODO(yyanagisawa): supports GENERATOR==make
     #  make generator doesn't support CC_wrapper without CC
     #  in make_global_settings yet.
     ['use_goma==1 and ("<(GENERATOR)"=="ninja" or clang==1)', {
       'make_global_settings': [
        ['CC_wrapper', '<(gomadir)/gomacc'],
        ['CXX_wrapper', '<(gomadir)/gomacc'],
@@ skipping 64 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',
   },
 }