更新了最新的vs2019 16.7版本后 chromium 编译不通过

chromium在最新的vs2019 16.7.1编译报错。

 方法一：同时安装以前版本：

msvs vs2019 安装较早期版本，同时安装vs2019的不同版本参考：

https://docs.microsoft.com/zh-cn/visualstudio/install/install-visual-studio-versions-side-by-side?view=vs-2019

https://docs.microsoft.com/zh-cn/visualstudio/releases/2019/history#installing-an-earlier-release

查看chromium编译脚本，在D:develectron7srcuildvs_toolchain.py中有查找vs版本的方法：

指定查找的版本顺序，自定义优先：

def DetectVisualStudioPath():
  """Return path to the GYP_MSVS_VERSION of Visual Studio.
  """

  # Note that this code is used from
  # build/toolchain/win/setup_toolchain.py as well.
  version_as_year = GetVisualStudioVersion()

  # The VC++ >=2017 install location needs to be located using COM instead of
  # the registry. For details see:
  # https://blogs.msdn.microsoft.com/heaths/2016/09/15/changes-to-visual-studio-15-setup/
  # For now we use a hardcoded default with an environment variable override.
  for path in (
      os.environ.get('vs%s_install' % version_as_year),
      os.path.expandvars('%ProgramFiles(x86)%' +
                         '/Microsoft Visual Studio/%s/Community' %
                         version_as_year),
      os.path.expandvars('%ProgramFiles(x86)%' +
                         '/Microsoft Visual Studio/%s/Enterprise' %
                         version_as_year),
      os.path.expandvars('%ProgramFiles(x86)%' +
                         '/Microsoft Visual Studio/%s/Professional' %
                         version_as_year),
      os.path.expandvars('%ProgramFiles(x86)%' +
                         '/Microsoft Visual Studio/%s/Preview' %
                         version_as_year)):
    if path and os.path.exists(path):
      return path

  raise Exception('Visual Studio Version %s (from GYP_MSVS_VERSION)'
                  ' not found.' % version_as_year)

方法二、

D:develectron7srcuild oolchainwinsetup_toolchain.py 这个是调用方，构造vs环境路径：

def _LoadToolchainEnv(cpu, sdk_dir, target_store):
  """Returns a dictionary with environment variables that must be set while
  running binaries from the toolchain (e.g. INCLUDE and PATH for cl.exe)."""
  # Check if we are running in the SDK command line environment and use
  # the setup script from the SDK if so. |cpu| should be either
  # 'x86' or 'x64' or 'arm' or 'arm64'.
  assert cpu in ('x86', 'x64', 'arm', 'arm64')
  if bool(int(os.environ.get('DEPOT_TOOLS_WIN_TOOLCHAIN', 1))) and sdk_dir:
    # Load environment from json file.
    env = os.path.normpath(os.path.join(sdk_dir, 'bin/SetEnv.%s.json' % cpu))
    env = json.load(open(env))['env']
    for k in env:
      entries = [os.path.join(*([os.path.join(sdk_dir, 'bin')] + e))
                 for e in env[k]]
      # clang-cl wants INCLUDE to be ;-separated even on non-Windows,
      # lld-link wants LIB to be ;-separated even on non-Windows.  Path gets :.
      # The separator for INCLUDE here must match the one used in main() below.
      sep = os.pathsep if k == 'PATH' else ';'
      env[k] = sep.join(entries)
    # PATH is a bit of a special case, it's in addition to the current PATH.
    env['PATH'] = env['PATH'] + os.pathsep + os.environ['PATH']
    # Augment with the current env to pick up TEMP and friends.
    for k in os.environ:
      if k not in env:
        env[k] = os.environ[k]

    varlines = []
    for k in sorted(env.keys()):
      varlines.append('%s=%s' % (str(k), str(env[k])))
    variables = '
'.join(varlines)

    # Check that the json file contained the same environment as the .cmd file.
    if sys.platform in ('win32', 'cygwin'):
      script = os.path.normpath(os.path.join(sdk_dir, 'Bin/SetEnv.cmd'))
      arg = '/' + cpu
      json_env = _ExtractImportantEnvironment(variables)
      cmd_env = _ExtractImportantEnvironment(_LoadEnvFromBat([script, arg]))
      assert _LowercaseDict(json_env) == _LowercaseDict(cmd_env)
  else:
    if 'GYP_MSVS_OVERRIDE_PATH' not in os.environ:
      os.environ['GYP_MSVS_OVERRIDE_PATH'] = _DetectVisualStudioPath()
    # We only support x64-hosted tools.
    script_path = os.path.normpath(os.path.join(
                                       os.environ['GYP_MSVS_OVERRIDE_PATH'],
                                       'VC/vcvarsall.bat'))
    print('vs path: %s ' % (script_path), file=sys.stderr)                                           
    if not os.path.exists(script_path):
      # vcvarsall.bat for VS 2017 fails if run after running vcvarsall.bat from
      # VS 2013 or VS 2015. Fix this by clearing the vsinstalldir environment
      # variable.
      if 'VSINSTALLDIR' in os.environ:
        del os.environ['VSINSTALLDIR']
      other_path = os.path.normpath(os.path.join(
                                        os.environ['GYP_MSVS_OVERRIDE_PATH'],
                                        'VC/Auxiliary/Build/vcvarsall.bat'))
      print('other_path path: %s ' % (other_path), file=sys.stderr)  
      if not os.path.exists(other_path):
        raise Exception('%s is missing - make sure VC++ tools are installed.' %
                        script_path)
      script_path = other_path
    cpu_arg = "amd64"
    if (cpu != 'x64'):
      # x64 is default target CPU thus any other CPU requires a target set
      cpu_arg += '_' + cpu
    args = [script_path, cpu_arg]
    # Store target must come before any SDK version declaration
    if (target_store):
      args.append(['store'])
    variables = _LoadEnvFromBat(args)
  print(args, file=sys.stderr)
  return _ExtractImportantEnvironment(variables)

解决方法：

调用到了加载环境变量，根据命令行D:>"C:Program Files (x86)Microsoft Visual Studio2019CommunityVCAuxiliaryBuildvcvarsall.bat" amd64  -vcvars_ver=14.25 是使用指定的编译环境。

在python中加一句：  args.append('-vcvars_ver=14.25')

def _LoadEnvFromBat(args):
  """Given a bat command, runs it and returns env vars set by it."""
  args = args[:]
  args.append('-vcvars_ver=14.25') //加了一句指定版本
  args.extend(('&&', 'set'))
  popen = subprocess.Popen(
      args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  variables, _ = popen.communicate()
  if popen.returncode != 0:
    raise Exception('"%s" failed with error %d' % (args, popen.returncode))
  return variables.decode(errors='ignore')

 记得必须安装alt mfc的生成工具：

从最外层调用：

def main():
  if len(sys.argv) != 7:
    print('Usage setup_toolchain.py '
          '<visual studio path> <win sdk path> '
          '<runtime dirs> <target_os> <target_cpu> '
          '<environment block name|none>')
    sys.exit(2)
  win_sdk_path = sys.argv[2]
  runtime_dirs = sys.argv[3]
  target_os = sys.argv[4]
  target_cpu = sys.argv[5]
  environment_block_name = sys.argv[6]
  if (environment_block_name == 'none'):
    environment_block_name = ''

  if (target_os == 'winuwp'):
    target_store = True
  else:
    target_store = False

  cpus = ('x86', 'x64', 'arm', 'arm64')
  assert target_cpu in cpus
  vc_bin_dir = ''
  vc_lib_path = ''
  vc_lib_atlmfc_path = ''
  vc_lib_um_path = ''
  include = ''
  lib = ''

  # TODO(scottmg|goma): Do we need an equivalent of
  # ninja_use_custom_environment_files?

  for cpu in cpus:
    if cpu == target_cpu:
      # Extract environment variables for subprocesses.
      env = _LoadToolchainEnv(cpu, win_sdk_path, target_store)
      print(env, file=sys.stderr)   
      env['PATH'] = runtime_dirs + os.pathsep + env['PATH']

      for path in env['PATH'].split(os.pathsep):
        print('vs path: %s ' % (path), file=sys.stderr)              
        if os.path.exists(os.path.join(path, 'cl.exe')):
          vc_bin_dir = os.path.realpath(path)
          break