Fix build warnings with gcc4.8

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 2540 matching lines @@
           # '-Wextra',
           # Don't warn about unused function params.  We use those everywhere.
           '-Wno-unused-parameter',
           # Don't warn about the "struct foo f = {0};" initialization pattern.
           '-Wno-missing-field-initializers',
           # Don't export any symbols (for example, to plugins we dlopen()).
           # Note: this is *required* to make some plugins work.
           '-fvisibility=hidden',
           '-pipe',
         ],
+        'conditions': [

[qiankun, 2013/04/13 01:21:30]

  Add a conditions section to check if gcc_version>=48. But it seems this
conditions section doesn't work. Because this flag doesn't appear in the
generated *.mk files. 
  If use 'target_conditions' instead of 'conditions', got the following error
"gyp: name 'gcc_version' is not defined while evaluating condition
'gcc_version>=48' in src/v8/tools/gyp/v8.gyp".
  If use the following code, it works.
        'target_conditions': [
          # 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
          [ '1==1', {
            'cflags': [
              '-Wno-unused-local-typedefs',
            ],
          }],
        ],
   Could you give some comments on these problems? What's the correct method to
check gcc_version here?

[Raphael Kubo da Costa (rakuco), 2013/04/15 10:57:07]

Have you tried running `gyp_chromium' with the CHROMIUM_GYP_SYNTAX_CHECK
environment variable set? I think the problem with putting this section here is
that there's also a `conditions' section defined later (around line 2706). I
don't really know what's wrong with the `target_conditions' part.

In any case, it should all work if you just add this check to the existing
`conditions' section.

+          # 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', {
+            'cflags': [
+              '-Wno-unused-local-typedefs',
+            ],
+          }],
+        ],
         'cflags_cc': [
           '-fno-rtti',
           '-fno-threadsafe-statics',
           # Make inline functions have hidden visiblity by default.
           # Surprisingly, not covered by -fvisibility=hidden.
           '-fvisibility-inlines-hidden',
           # GCC turns on -Wsign-compare for C++ under -Wall, but clang doesn't,
           # so we specify it explicitly.
           # TODO(fischman): remove this if http://llvm.org/PR10448 obsoletes it.
           # http://code.google.com/p/chromium/issues/detail?id=90453
@@ skipping 1651 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',
   },
 }