Allow selection between libstdc++ and libc++ when targeting iOS

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 392 matching lines @@
 
       # Use the dynamic libraries instrumented by one of the sanitizers
       # instead of the standard system libraries.
       'use_instrumented_libraries%': 0,
 
       # Use libc++ (third_party/libc++ and third_party/libc++abi) instead of
       # stdlibc++ as standard library. This is intended to use for instrumented
       # builds.
       'use_custom_libcxx%': 0,
 
+      # Use system libc++ instead of the default C++ library, usually libstdc++.
+      # This is intended for iOS builds only.
+      'use_system_libcxx%': 0,
+
       # Use a modified version of Clang to intercept allocated types and sizes
       # for allocated objects. clang_type_profiler=1 implies clang=1.
       # See http://dev.chromium.org/developers/deep-memory-profiler/cpp-object-type-identifier
       # TODO(dmikurube): Support mac.  See http://crbug.com/123758#c11
       'clang_type_profiler%': 0,
 
       # Set to true to instrument the code with function call logger.
       # See src/third_party/cygprofile/cyg-profile.cc for details.
       'order_profiling%': 0,
 
@@ skipping 664 matching lines @@
     'msan%': '<(msan)',
     'msan_blacklist%': '<(msan_blacklist)',
     'msan_track_origins%': '<(msan_track_origins)',
     'tsan%': '<(tsan)',
     'tsan_blacklist%': '<(tsan_blacklist)',
     'ubsan%': '<(ubsan)',
     'ubsan_vptr%': '<(ubsan_vptr)',
     'ubsan_vptr_blacklist%': '<(ubsan_vptr_blacklist)',
     'use_instrumented_libraries%': '<(use_instrumented_libraries)',
     'use_custom_libcxx%': '<(use_custom_libcxx)',
+    'use_system_libcxx%': '<(use_system_libcxx)',
     'clang_type_profiler%': '<(clang_type_profiler)',
     'order_profiling%': '<(order_profiling)',
     'order_text_section%': '<(order_text_section)',
     'enable_extensions%': '<(enable_extensions)',
     'enable_plugin_installation%': '<(enable_plugin_installation)',
     'enable_plugins%': '<(enable_plugins)',
     'enable_session_service%': '<(enable_session_service)',
     'enable_themes%': '<(enable_themes)',
     'enable_autofill_dialog%': '<(enable_autofill_dialog)',
     'enable_prod_wallet_service%': '<(enable_prod_wallet_service)',
@@ skipping 342 matching lines @@
     # Chrome OS: whether to build ChromeVox from sources in the Chromium
     # repository rather than using precompiled JavaScript in
     # chrome/third_party/chromevox.  This is still experimental.
     'use_migrated_chromevox%': 1,
 
     # Chrome OS: whether to also build the upcoming version of
     # ChromeVox, which can then be enabled via a command-line switch.
     'use_chromevox_next%': 0,
 
     'conditions': [
+      # The version of clang shipped upstream does not find C++ headers when
+      # using -stdlib=libc++ so we instead need to use the version of clang
+      # coming with Xcode.
+      ['OS=="ios" and use_system_libcxx==1', {
+        'clang_xcode%': 1,
+      }],
       # Enable the Syzygy optimization step for the official builds.
       ['OS=="win" and buildtype=="Official" and syzyasan!=1', {
         'syzygy_optimize%': 1,
       }, {
         'syzygy_optimize%': 0,
       }],
       # Get binutils version so we can enable debug fission if we can.
       ['os_posix==1 and OS!="mac" and OS!="ios"', {
         'conditions': [
           # compiler_version doesn't work with clang
@@ skipping 3564 matching lines @@
             # ones (they are used when building for the simulator).
             ['target_subarch=="arm32"', {
               'VALID_ARCHS': ['armv7', 'i386'],
             }],
             ['target_subarch=="arm64"', {
               'VALID_ARCHS': ['arm64', 'x86_64'],
             }],
             ['target_subarch=="both"', {
               'VALID_ARCHS': ['arm64', 'armv7', 'x86_64', 'i386'],
             }],
+            ['use_system_libcxx==1', {
+              'target_conditions': [
+                # Only use libc++ when building target for iOS not when building
+                # tools for the host (OS X) as Mac targets OS X SDK 10.6 which
+                # does not support libc++.
+                ['_toolset=="target"', {
+                  'CLANG_CXX_LIBRARY': 'libc++',  # -stdlib=libc++
+                }]
+              ],
+            }],
           ],
         },
         'target_conditions': [
           ['_toolset=="host"', {
             'xcode_settings': {
               'SDKROOT': 'macosx<(mac_sdk)',  # -isysroot
               'MACOSX_DEPLOYMENT_TARGET': '<(mac_deployment_target)',
               'VALID_ARCHS': [
                 'x86_64',
               ],
@@ skipping 214 matching lines @@
           # usage of this is simply more hassle than the warning is worth.
           4355,
 
           # C4503: 'identifier': decorated name length exceeded, name was
           #        truncated
           # This only means that some long error messages might have truncated
           # identifiers in the presence of lots of templates.  It has no effect
           # on program correctness and there's no real reason to waste time
           # trying to prevent it.
           4503,
-          
+
           # C4611: interaction between 'function' and C++ object destruction is
           #        non-portable
           # This warning is unavoidable when using e.g. setjmp/longjmp.  MSDN
           # suggests using exceptions instead of setjmp/longjmp for C++, but
           # Chromium code compiles without exception support.  We therefore have
           # to use setjmp/longjmp for e.g. JPEG decode error handling, which
           # means we have to turn off this warning (and be careful about how
           # object destruction happens in such cases).
           4611,
 
@@ skipping 384 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',
   },
 }