cef/tools/gn_args.py

# Copyright 2016 The Chromium Embedded Framework Authors. Portions copyright
# 2012 Google Inc. All rights reserved. Use of this source code is governed by
# a BSD-style license that can be found in the LICENSE file.

# This script determines the contents of the per-configuration `args.gn` files
# that are used to build CEF/Chromium with GN. See comments in CEF's top-level
# BUILD.gn file for general GN usage instructions.
#
# This script performs the following tasks:
#
# - Defines CEF's default and required arg values in cases where they differ
#   from Chromium's.
# - Accepts user-defined arg values via the GN_DEFINES environment variable.
# - Verifies that user-defined arg values do not conflict with CEF's
#   requirements.
# - Generates multiple configurations by combining user-defined arg values with
#   CEF's default and required values.
#
# Before adding a new arg value in this script determine the following:
#
# - Chromium's default value. Default values are defined in the declare_args()
#   sections of *.gni files.
# - Chromium's value requirements. Check for assert()s related to the value in
#   Chromium code.
# - Whether a particular value is optional or required for CEF.
# - Under what conditions a particular value is required for CEF (platform,
#   build type, CPU architecture, etc).
#
# If CEF can use Chromium's default value and has no additional validation
# requirements then do nothing.
#
# If CEF can use Chromium's default value but would like to enforce additional
# validation requirements then go to 3B.
#
# If CEF cannot or should not use Chromium's default value then choose one of
# the following:
#
# 1. If CEF requires a different value either globally or based on the platform:
#  - Add an assert() for the value in CEF's top-level BUILD.gn file.
#  - Add the required value in GetRequiredArgs().
#  - Result: CEF's required value will be used. The user cannot override the
#    value via GN_DEFINES.
#
# 2. If CEF requires a different value based on the build type or CPU
#    architecture:
#  - Add an assert() for the value in CEF's top-level BUILD.gn file.
#  - Add the required value in GetConfigArgs().
#  - Result: CEF's required value will be used. The user cannot override the
#    value via GN_DEFINES.
#
# 3. If CEF recommends (but does not require) a different value either globally
#    or based on the platform:
#    A. Set the default value:
#     - Add the recommended value in GetRecommendedDefaultArgs().
#     - Result: CEF's recommended value will be used by default. The user can
#       override the value via GN_DEFINES.
#
#    B. If CEF has additional validation requirements:
#     - Add the default Chromium value in GetChromiumDefaultArgs().
#     - Perform validation in ValidateArgs().
#     - Result: An AssertionError will be thrown if validation fails.

from __future__ import absolute_import
from __future__ import print_function
import os
import shlex
import sys

# The CEF directory is the parent directory of _this_ script.
cef_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), os.pardir))
# The src directory is the parent directory of the CEF directory.
src_dir = os.path.abspath(os.path.join(cef_dir, os.pardir))

# Determine the platform.
if sys.platform == 'win32':
  platform = 'windows'
elif sys.platform == 'darwin':
  platform = 'mac'
elif sys.platform.startswith('linux'):
  platform = 'linux'
else:
  print('Unknown operating system platform')
  sys.exit()


def msg(msg):
  print('NOTE: ' + msg)


def NameValueListToDict(name_value_list):
  """
  Takes an array of strings of the form 'NAME=VALUE' and creates a dictionary
  of the pairs. If a string is simply NAME, then the value in the dictionary
  is set to True. If VALUE can be converted to a boolean or integer, it is.
  """
  result = {}
  for item in name_value_list:
    tokens = item.split('=', 1)
    if len(tokens) == 2:
      token_value = tokens[1]
      if token_value.lower() == 'true':
        token_value = True
      elif token_value.lower() == 'false':
        token_value = False
      else:
        # If we can make it an int, use that, otherwise, use the string.
        try:
          token_value = int(token_value)
        except ValueError:
          pass
      # Set the variable to the supplied value.
      result[tokens[0]] = token_value
    else:
      # No value supplied, treat it as a boolean and set it.
      result[tokens[0]] = True
  return result


def ShlexEnv(env_name):
  """
  Split an environment variable using shell-like syntax.
  """
  flags = os.environ.get(env_name, [])
  if flags:
    flags = shlex.split(flags)
  return flags


def MergeDicts(*dict_args):
  """
  Given any number of dicts, shallow copy and merge into a new dict.
  Precedence goes to key value pairs in latter dicts.
  """
  result = {}
  for dictionary in dict_args:
    result.update(dictionary)
  return result


def GetValueString(val):
  """
  Return the string representation of |val| expected by GN.
  """
  if isinstance(val, bool):
    if val:
      return 'true'
    else:
      return 'false'
  elif isinstance(val, int):
    return val
  else:
    return '"%s"' % val
  return val


def GetChromiumDefaultArgs():
  """
  Return default GN args. These must match the Chromium defaults.
  Only args that may be retrieved via GetArgValue() need to be specified here.
  """
  # Search for these values in declare_args() sections of *.gni files to find
  # the defaults.

  defaults = {
      'dcheck_always_on': False,
      'is_asan': False,
      'is_debug': True,
      'is_official_build': False,
      'target_cpu': 'x64',
  }

  if platform == 'linux':
    defaults['use_sysroot'] = True

  if platform == 'windows':
    defaults['is_win_fastlink'] = False
    defaults['visual_studio_path'] = ''
    defaults['visual_studio_version'] = ''
    defaults['visual_studio_runtime_dirs'] = ''
    defaults['windows_sdk_path'] = ''

  return defaults


def GetArgValue(args, key):
  """
  Return an existing GN arg value or the Chromium default.
  """
  defaults = GetChromiumDefaultArgs()
  assert key in defaults, "No default Chromium value specified for %s" % key
  return args.get(key, defaults[key])


def GetRecommendedDefaultArgs():
  """
  Return recommended default GN args that differ from Chromium defaults.
  """
  # Search for these values in declare_args() sections of *.gni files to find
  # the defaults.

  result = {
      # Enable NaCL. Default is true. False is recommended for faster builds.
      'enable_nacl': False,

      # Disable component builds. Default depends on the platform. True results
      # in faster local builds but False is required to create a CEF binary
      # distribution.
      'is_component_build': False,

      # Specify the current PGO phase. Default is 0 (turned off) for normal
      # builds and 2 (used during the optimization phase) for official Windows
      # and macOS builds. Currently turned off for CEF because it requires
      # additional setup and is not yet tested. See issue #2956.
      'chrome_pgo_phase': 0,

      # Disable support for background apps, which don't make sense with CEF.
      # Default is enabled on desktop platforms. This feature was also causing
      # strange shutdown crashes when using the Chrome runtime with a Debug
      # component build on Windows.
      'enable_background_mode': False,

      # Disable support for resource allowlist generation. When enabled this
      # introduces a Windows official build dependency on the
      # "//chrome:chrome_dll" target, which will fail to build with CEF.
      'enable_resource_allowlist_generation': False,
  }

  if platform != 'windows':
    # Only allow non-component Debug builds on non-Windows platforms. These
    # builds will fail on Windows due to linker issues (running out of memory,
    # etc). See https://bitbucket.org/chromiumembedded/cef/issues/2679.
    result['forbid_non_component_debug_builds'] = False

  if platform == 'linux':
    # Use a sysroot environment. Default is true. False is recommended for local
    # builds.
    # Run the following commands to download the sysroot environment:
    # x86 build only:   $ export GYP_DEFINES='target_arch=ia32'
    # x86 or x64 build: $ gclient runhooks
    result['use_sysroot'] = False

    # Don't add the `-Wl,--fatal-warnings` linker flag when building on Ubuntu
    # 14 (Trusty) host systems. It results in errors like the following:
    # ld.lld: error: found local symbol '__bss_start' in global part of symbol
    # table in file /usr/lib/x86_64-linux-gnu/libGL.so
    # TODO(cef): Remove this flag once we require a newer host system.
    result['fatal_linker_warnings'] = False

  return result


def GetGNEnvArgs():
  """
  Return GN args specified via the GN_DEFINES env variable.
  """
  return NameValueListToDict(ShlexEnv('GN_DEFINES'))


def GetRequiredArgs():
  """
  Return required GN args. Also enforced by assert() in //cef/BUILD.gn.
  """
  result = {
      # Set ENABLE_PRINTING=1 ENABLE_BASIC_PRINTING=1.
      'enable_basic_printing': True,
      # ENABLE_SERVICE_DISCOVERY=0 for print preview support
      'enable_print_preview': True,
      'optimize_webui': True,
      # Enable support for Widevine CDM.
      'enable_widevine': True,

      # Don't use the chrome style plugin.
      'clang_use_chrome_plugins': False,
  }

  if platform == 'linux':
    # Don't generate Chromium installer packages. This avoids GN dependency
    # errors with CEF (see issue #2301).
    # Due to the way this variable is declared in chrome/installer/BUILD.gn it
    # can't be enforced by assert().
    result['enable_linux_installer'] = False

  return result


def GetMergedArgs(build_args):
  """
  Return merged GN args.
  """
  dict = MergeDicts(GetRecommendedDefaultArgs(), GetGNEnvArgs(), build_args)

  # Verify that the user is not trying to override required args.
  required = GetRequiredArgs()
  for key in required.keys():
    if key in dict:
      assert dict[key] == required[key], \
          "%s=%s is required" % (key, GetValueString(required[key]))

  return MergeDicts(dict, required)


def ValidateArgs(args):
  """
  Validate GN arg combinations that we know about. Also provide suggestions
  where appropriate.
  """
  dcheck_always_on = GetArgValue(args, 'dcheck_always_on')
  is_asan = GetArgValue(args, 'is_asan')
  is_debug = GetArgValue(args, 'is_debug')
  is_official_build = GetArgValue(args, 'is_official_build')
  target_cpu = GetArgValue(args, 'target_cpu')

  if platform == 'linux':
    use_sysroot = GetArgValue(args, 'use_sysroot')

  if platform == 'windows':
    is_win_fastlink = GetArgValue(args, 'is_win_fastlink')
    visual_studio_path = GetArgValue(args, 'visual_studio_path')
    visual_studio_version = GetArgValue(args, 'visual_studio_version')
    visual_studio_runtime_dirs = GetArgValue(args, 'visual_studio_runtime_dirs')
    windows_sdk_path = GetArgValue(args, 'windows_sdk_path')

  # Target CPU architecture.
  # - Windows supports "x86", "x64" and "arm64".
  # - Mac supports "x64" and "arm64".
  # - Linux supports only "x64" unless using a sysroot environment.
  if platform == 'mac':
    assert target_cpu in ('x64', 'arm64'), 'target_cpu must be "x64" or "arm64"'
  elif platform == 'windows':
    assert target_cpu in ('x86', 'x64',
                          'arm64'), 'target_cpu must be "x86", "x64" or "arm64"'
  elif platform == 'linux':
    assert target_cpu in (
        'x86', 'x64', 'arm',
        'arm64'), 'target_cpu must be "x86", "x64", "arm" or "arm64"'

  if platform == 'linux':
    if target_cpu == 'x86':
      assert use_sysroot, 'target_cpu="x86" requires use_sysroot=true'
    elif target_cpu == 'arm':
      assert use_sysroot, 'target_cpu="arm" requires use_sysroot=true'
    elif target_cpu == 'arm64':
      assert use_sysroot, 'target_cpu="arm64" requires use_sysroot=true'

  # ASAN requires Release builds.
  if is_asan:
    assert not is_debug, "is_asan=true requires is_debug=false"
    if not dcheck_always_on:
      msg('is_asan=true recommends dcheck_always_on=true')

  # Official build requires Release builds.
  if is_official_build:
    assert not is_debug, "is_official_build=true requires is_debug=false"

  if platform == 'windows':
    # Official builds should not use /DEBUG:FASTLINK.
    if is_official_build:
      assert not is_win_fastlink, "is_official_build=true precludes is_win_fastlink=true"

    # Windows custom toolchain requirements.
    #
    # Required GN arguments:
    #   visual_studio_path="<path to VS root>"
    #     The directory that contains Visual Studio. For example, a subset of
    #     "C:\Program Files (x86)\Microsoft Visual Studio 14.0".
    #   visual_studio_version="<VS version>"
    #     The VS version. For example, "2015".
    #   visual_studio_runtime_dirs="<path to VS CRT>"
    #     The directory that contains the VS CRT. For example, the contents of
    #     "C:\Program Files (x86)\Windows Kits\10\Redist\ucrt\DLLs\x64" plus
    #     "C:\Windows\System32\ucrtbased.dll"
    #   windows_sdk_path="<path to WinSDK>"
    #     The directory that contains the Win SDK. For example, a subset of
    #     "C:\Program Files (x86)\Windows Kits\10".
    #
    # Required environment variables:
    #   DEPOT_TOOLS_WIN_TOOLCHAIN=0
    #   GYP_MSVS_OVERRIDE_PATH=<path to VS root, must match visual_studio_path>
    #   GYP_MSVS_VERSION=<VS version, must match visual_studio_version>
    #   CEF_VCVARS=none
    #
    # Optional environment variables (required if vcvarsall.bat does not exist):
    #   INCLUDE=<VS include paths>
    #   LIB=<VS library paths>
    #   PATH=<VS executable paths>
    #
    # See comments in gclient_hook.py for environment variable usage.
    #
    if visual_studio_path != '':
      assert visual_studio_version != '', 'visual_studio_path requires visual_studio_version'
      assert visual_studio_runtime_dirs != '', 'visual_studio_path requires visual_studio_runtime_dirs'
      assert windows_sdk_path != '', 'visual_studio_path requires windows_sdk_path'

      assert os.environ.get('DEPOT_TOOLS_WIN_TOOLCHAIN', '') == '0', \
        "visual_studio_path requires DEPOT_TOOLS_WIN_TOOLCHAIN=0 env variable"

      msvs_path = os.environ.get('GYP_MSVS_OVERRIDE_PATH', '')
      assert msvs_path == visual_studio_path and os.path.exists(msvs_path), \
        "visual_studio_path requires matching GYP_MSVS_OVERRIDE_PATH env variable"

      msvs_version = os.environ.get('GYP_MSVS_VERSION', '')
      assert msvs_version == visual_studio_version, \
        "visual_studio_version requires matching GYP_MSVS_VERSION env variable"

      assert os.environ.get('CEF_VCVARS', '') == 'none', \
        "visual_studio_path requires CEF_VCVARS=none env variable"

      # If vcvarsall.bat exists then environment variables will be derived from
      # there and any specified INCLUDE/LIB values will be ignored by Chromium
      # (PATH is retained because it might contain required VS runtime
      # libraries). If this file does not exist then the INCLUDE/LIB/PATH values
      # are also required by Chromium.
      vcvars_path = os.path.join(msvs_path, 'VC', 'vcvarsall.bat')
      if not os.path.exists(vcvars_path):
        vcvars_path = os.path.join(msvs_path, 'VC', 'Auxiliary', 'Build',
                                   'vcvarsall.bat')
      if os.path.exists(vcvars_path):
        if 'INCLUDE' in os.environ:
          del os.environ['INCLUDE']
        if 'LIB' in os.environ:
          del os.environ['LIB']
        if 'LIBPATH' in os.environ:
          del os.environ['LIBPATH']
      else:
        assert 'INCLUDE' in os.environ \
          and 'LIB' in os.environ \
          and 'PATH' in os.environ, \
          "visual_studio_path requires INCLUDE, LIB and PATH env variables"


def GetConfigArgs(args, is_debug, cpu):
  """
  Return merged GN args for the configuration and validate.
  """
  add_args = {}

  # Cannot create is_official_build=true is_debug=true builds.
  # This restriction is enforced in //build/config/BUILDCONFIG.gn.
  # Instead, our "official Debug" build is a Release build with dchecks and
  # symbols. Symbols will be generated by default for official builds; see the
  # definition of 'symbol_level' in //build/config/compiler/compiler.gni.
  if is_debug and GetArgValue(args, 'is_official_build'):
    is_debug = False
    add_args['dcheck_always_on'] = True

  result = MergeDicts(args, add_args, {
      'is_debug': is_debug,
      'target_cpu': cpu,
  })

  if platform == 'linux' and not cpu.startswith('arm'):
    # Remove any arm-related values from non-arm configs.
    for key in result.keys():
      if key.startswith('arm_'):
        del result[key]

  ValidateArgs(result)
  return result


def GetConfigArgsSandbox(platform, args, is_debug, cpu):
  """
  Return merged GN args for the cef_sandbox configuration and validate.
  """
  add_args = {
      # Avoid libucrt.lib linker errors.
      'use_allocator_shim': False,

      # PartitionAlloc is selected as the default allocator in some cases.
      # We can't use it because it requires use_allocator_shim=true.
      'use_allocator': "none",

      # Avoid /LTCG linker warnings and generate smaller lib files.
      'is_official_build': False,

      # Enable base target customizations necessary for distribution of the
      # cef_sandbox static library.
      'is_cef_sandbox_build': True,
  }

  if platform == 'windows':
    # Avoid Debug build linker errors caused by custom libc++.
    add_args['use_custom_libcxx'] = False

    # Avoid dependency on //third_party/perfetto:libperfetto which fails to
    # build with MSVC libc++.
    add_args['enable_base_tracing'] = False

    # Don't enable -Wmax-tokens in combination with MSVC libc++.
    add_args['enable_wmax_tokens'] = False

    # Allow non-component Debug builds for the sandbox.
    add_args['forbid_non_component_debug_builds'] = False

  result = MergeDicts(args, add_args, {
      'is_debug': is_debug,
      'target_cpu': cpu,
  })

  ValidateArgs(result)
  return result


def LinuxSysrootExists(cpu):
  """
  Returns true if the sysroot for the specified |cpu| architecture exists.
  """
  # Directory that contains sysroots.
  sysroot_root = os.path.join(src_dir, 'build', 'linux')
  # CPU-specific sysroot directory names.
  # Should match the values in build/config/sysroot.gni.
  if cpu == 'x86':
    sysroot_name = 'debian_sid_i386-sysroot'
  elif cpu == 'x64':
    sysroot_name = 'debian_sid_amd64-sysroot'
  elif cpu == 'arm':
    sysroot_name = 'debian_sid_arm-sysroot'
  elif cpu == 'arm64':
    sysroot_name = 'debian_sid_arm64-sysroot'
  else:
    raise Exception('Unrecognized sysroot CPU: %s' % cpu)

  return os.path.isdir(os.path.join(sysroot_root, sysroot_name))


def GetAllPlatformConfigs(build_args):
  """
  Return a map of directory name to GN args for the current platform.
  """
  result = {}

  # Merged args without validation.
  args = GetMergedArgs(build_args)

  create_debug = True

  # Don't create debug directories for asan builds.
  if GetArgValue(args, 'is_asan'):
    create_debug = False
    msg('Not generating Debug configuration due to is_asan=true')

  supported_cpus = []

  if platform == 'linux':
    use_sysroot = GetArgValue(args, 'use_sysroot')
    if use_sysroot:
      # Only generate configurations for sysroots that have been installed.
      for cpu in ('x86', 'x64', 'arm', 'arm64'):
        if LinuxSysrootExists(cpu):
          supported_cpus.append(cpu)
        else:
          msg('Not generating %s configuration due to missing sysroot directory'
              % cpu)
    else:
      supported_cpus = ['x64']
  elif platform == 'windows':
    supported_cpus = ['x86', 'x64']
    if os.environ.get('CEF_ENABLE_ARM64', '') == '1':
      supported_cpus.append('arm64')
  elif platform == 'mac':
    supported_cpus = ['x64']
    if os.environ.get('CEF_ENABLE_ARM64', '') == '1':
      supported_cpus.append('arm64')
  else:
    raise Exception('Unsupported platform')

  for cpu in supported_cpus:
    if create_debug:
      result['Debug_GN_' + cpu] = GetConfigArgs(args, True, cpu)
    result['Release_GN_' + cpu] = GetConfigArgs(args, False, cpu)

    if platform in ('windows', 'mac') and GetArgValue(args,
                                                      'is_official_build'):
      # Build cef_sandbox.lib with a different configuration.
      if create_debug:
        result['Debug_GN_' + cpu + '_sandbox'] = GetConfigArgsSandbox(
            platform, args, True, cpu)
      result['Release_GN_' + cpu + '_sandbox'] = GetConfigArgsSandbox(
          platform, args, False, cpu)

  return result


def GetConfigFileContents(args):
  """
  Generate config file contents for the arguments.
  """
  pairs = []
  for k in sorted(args.keys()):
    pairs.append("%s=%s" % (k, GetValueString(args[k])))
  return "\n".join(pairs)


# Program entry point.
if __name__ == '__main__':
  import sys

  # Allow override of the platform via the command-line for testing.
  if len(sys.argv) > 1:
    platform = sys.argv[1]
    if not platform in ('linux', 'mac', 'windows'):
      sys.stderr.write('Usage: %s <platform>\n' % sys.argv[0])
      sys.exit()

  print('Platform: %s' % platform)

  # Dump the configuration based on platform and environment.
  configs = GetAllPlatformConfigs({})
  for dir, config in configs.items():
    print('\n\nout/%s:\n' % dir)
    print(GetConfigFileContents(config))