gyp_chromium分析
gclient最后会执行hooks里的动作，而在chromium的代码配置文件中设置的hooks是运行src/build/gyp_chromium文件。下面分析这个文件的作用以及运行过程。
定义两个路径分别是script_dir和chromium_src，这里分别是脚本所在的路径和它的父目录。然后定义两个函数apply_gyp_environment和additional_include_files。
在程序运行开始就检查是否设置了环境变量SKIP_CHROMIUM_GYP_ENV，如果没有则调用函数apply_gyp_environment尝试读取chromium.gyp_env。
def apply_gyp_environment(file_path=None):
"""
Reads in a *.gyp_env file and applies the valid keys to os.environ.
"""
if not file_path or not os.path.exists(file_path):
return
file_contents = open(file_path).read()
try:
file_data = eval(file_contents, {'__builtins__': None}, None)
except SyntaxError, e:
e.filename = os.path.abspath(file_path)
raise
supported_vars = ( 'CHROMIUM_GYP_FILE',
'CHROMIUM_GYP_SYNTAX_CHECK',
'GYP_DEFINES',
'GYP_GENERATOR_FLAGS',
'GYP_GENERATOR_OUTPUT', )
for var in supported_vars:
val = file_data.get(var)
if val:
if var in os.environ:
print 'INFO: Environment value for "%s" overrides value in %s.' % (
var, os.path.abspath(file_path)
)
else:
os.environ[var] = val
读取file_path的内容，赋值给file_data。eval函数求值file_data字符串的值，其结果file_data是dict。读取其中的内容，与环境定义的变量supported_vars比较，如果环境中存在的变量则保持不变，否则加入到环境。
如果没有指定gyp文件，则添加all.gyp路径到args中，args.append(os.path.join(script_dir, 'all.gyp'))，并且args.extend(['-I' + i for i in additional_include_files(args)])把参数中以-I指定的路径加入到args中，在本例中args开始为空。
########## gyp_chromium ##############
def additional_include_files(args=[]):
"""
Returns a list of additional (.gypi) files to include, without
duplicating ones that are already specified on the command line.
"""
# Determine the include files specified on the command line.
# This doesn't cover all the different option formats you can use,
# but it's mainly intended to avoid duplicating flags on the automatic
# makefile regeneration which only uses this format.
specified_includes = set()
for arg in args:
if arg.startswith('-I') and len(arg) > 2:
specified_includes.add(os.path.realpath(arg[2:]))
result = []
def AddInclude(path):
if os.path.realpath(path) not in specified_includes:
result.append(path)
# Always include common.gypi & features_override.gypi
AddInclude(os.path.join(script_dir, 'common.gypi'))
AddInclude(os.path.join(script_dir, 'features_override.gypi'))
# Optionally add supplemental .gypi files if present.
supplements = glob.glob(os.path.join(chrome_src, '*', 'supplement.gypi'))
for supplement in supplements:
AddInclude(supplement)
return result
additional_include_files函数的作用是除了命令行指定的路径外，包含chrome_src目录下的所有supplement.gypi文件以及script_dir下的common.gypi和features_override.gypi。还有all.gyp文件的路径组成了args。最后调用sys.exit(gyp.main(args))。