Always define the `gcc_version' variable to some value.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 795231a1184f9323eb8386ca7d441c4afd2978d3..f05557d6675c73a19c5b016caff16dee39ee2a47 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -895,6 +895,11 @@
     'clang%': '<(clang)',
     'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',
 
+    # The version of GCC in use, set later in platforms that use GCC and have
+    # not explicitly chosen to build with clang. Currently, this means all
+    # platforms except Windows, Mac and iOS.
+    'gcc_version%': 0,

[Paweł Hajdan Jr., 2013/04/26 17:02:07]

We already have a block like:

          ['clang==0 and asan==0 and tsan==0 and msan==0', {
            # This will set gcc_version to XY if you are running gcc X.Y.*.
            # This is used to tweak build flags for gcc 4.5.
            'gcc_version%': '<!(python <(DEPTH)/build/compiler_version.py)',
          }, {
            'gcc_version%': 0,
          }],

in this file. Please extract it and update the condition. This will make
gcc_version defined in only one place, making it easier to reason about.

+
     # 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.
@@ -2717,14 +2722,6 @@
           },
         },
         '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
-          [ 'gcc_version>=48', {
-            'cflags': [
-              '-Wno-unused-local-typedefs',
-            ],
-          }],
           ['target_arch=="ia32"', {
             'target_conditions': [
               ['_toolset=="target"', {
@@ -4187,6 +4184,16 @@
         ],
       },
     }],
+    # Don't warn about the "typedef 'foo' locally defined but not used"

[Paweł Hajdan Jr., 2013/04/26 17:02:07]

Why is this code being moved?

+    # for gcc 4.8.
+    # TODO: remove this flag once all builds work. See crbug.com/227506
+    ['gcc_version>=48', {
+      'target_defaults': {
+        'cflags': [
+          '-Wno-unused-local-typedefs',
+        ],
+      },
+    }],
     ['clang==1', {
       'conditions': [
         ['OS=="android"', {