configure.py

# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""configure script to get build parameters from user."""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import argparse
import errno
import os
import platform
import re
import subprocess
import sys

# pylint: disable=g-import-not-at-top
try:
  from shutil import which
except ImportError:
  from distutils.spawn import find_executable as which
# pylint: enable=g-import-not-at-top

_DEFAULT_CUDA_VERSION = '10'
_DEFAULT_CUDNN_VERSION = '7'
_DEFAULT_TENSORRT_VERSION = '6'
_DEFAULT_CUDA_COMPUTE_CAPABILITIES = '3.5,7.0'

_TF_OPENCL_VERSION = '1.2'
_DEFAULT_COMPUTECPP_TOOLKIT_PATH = '/usr/local/computecpp'
_DEFAULT_TRISYCL_INCLUDE_DIR = '/usr/local/triSYCL/include'
_SUPPORTED_ANDROID_NDK_VERSIONS = [10, 11, 12, 13, 14, 15, 16, 17, 18]

_DEFAULT_PROMPT_ASK_ATTEMPTS = 10

_TF_BAZELRC_FILENAME = '.tf_configure.bazelrc'
_TF_WORKSPACE_ROOT = ''
_TF_BAZELRC = ''
_TF_CURRENT_BAZEL_VERSION = None
_TF_MIN_BAZEL_VERSION = '1.0.0'
_TF_MAX_BAZEL_VERSION = '1.1.0'

NCCL_LIB_PATHS = [
    'lib64/', 'lib/powerpc64le-linux-gnu/', 'lib/x86_64-linux-gnu/', ''
]

# List of files to configure when building Bazel on Apple platforms.
APPLE_BAZEL_FILES = [
    'tensorflow/lite/experimental/ios/BUILD',
    'tensorflow/lite/experimental/objc/BUILD',
    'tensorflow/lite/experimental/swift/BUILD',
    'tensorflow/lite/tools/benchmark/experimental/ios/BUILD'
]

# List of files to move when building for iOS.
IOS_FILES = [
    'tensorflow/lite/experimental/objc/TensorFlowLiteObjC.podspec',
    'tensorflow/lite/experimental/swift/TensorFlowLiteSwift.podspec',
]


class UserInputError(Exception):
  pass


def is_windows():
  return platform.system() == 'Windows'


def is_linux():
  return platform.system() == 'Linux'


def is_macos():
  return platform.system() == 'Darwin'


def is_ppc64le():
  return platform.machine() == 'ppc64le'


def is_cygwin():
  return platform.system().startswith('CYGWIN_NT')


def get_input(question):
  try:
    try:
      answer = raw_input(question)
    except NameError:
      answer = input(question)  # pylint: disable=bad-builtin
  except EOFError:
    answer = ''
  return answer


def symlink_force(target, link_name):
  """Force symlink, equivalent of 'ln -sf'.

  Args:
    target: items to link to.
    link_name: name of the link.
  """
  try:
    os.symlink(target, link_name)
  except OSError as e:
    if e.errno == errno.EEXIST:
      os.remove(link_name)
      os.symlink(target, link_name)
    else:
      raise e


def sed_in_place(filename, old, new):
  """Replace old string with new string in file.

  Args:
    filename: string for filename.
    old: string to replace.
    new: new string to replace to.
  """
  with open(filename, 'r') as f:
    filedata = f.read()
  newdata = filedata.replace(old, new)
  with open(filename, 'w') as f:
    f.write(newdata)


def write_to_bazelrc(line):
  with open(_TF_BAZELRC, 'a') as f:
    f.write(line + '\n')


def write_action_env_to_bazelrc(var_name, var):
  write_to_bazelrc('build --action_env %s="%s"' % (var_name, str(var)))


def run_shell(cmd, allow_non_zero=False, stderr=None):
  if stderr is None:
    stderr = sys.stdout
  if allow_non_zero:
    try:
      output = subprocess.check_output(cmd, stderr=stderr)
    except subprocess.CalledProcessError as e:
      output = e.output
  else:
    output = subprocess.check_output(cmd, stderr=stderr)
  return output.decode('UTF-8').strip()


def cygpath(path):
  """Convert path from posix to windows."""
  return os.path.abspath(path).replace('\\', '/')


def get_python_path(environ_cp, python_bin_path):
  """Get the python site package paths."""
  python_paths = []
  if environ_cp.get('PYTHONPATH'):
    python_paths = environ_cp.get('PYTHONPATH').split(':')
  try:
    library_paths = run_shell([
        python_bin_path, '-c',
        'import site; print("\\n".join(site.getsitepackages()))'
    ]).split('\n')
  except subprocess.CalledProcessError:
    library_paths = [
        run_shell([
            python_bin_path, '-c',
            'from distutils.sysconfig import get_python_lib;'
            'print(get_python_lib())'
        ])
    ]

  all_paths = set(python_paths + library_paths)

  paths = []
  for path in all_paths:
    if os.path.isdir(path):
      paths.append(path)
  return paths


def get_python_major_version(python_bin_path):
  """Get the python major version."""
  return run_shell([python_bin_path, '-c', 'import sys; print(sys.version[0])'])


def setup_python(environ_cp):
  """Setup python related env variables."""
  # Get PYTHON_BIN_PATH, default is the current running python.
  default_python_bin_path = sys.executable
  ask_python_bin_path = ('Please specify the location of python. [Default is '
                         '%s]: ') % default_python_bin_path
  while True:
    python_bin_path = get_from_env_or_user_or_default(environ_cp,
                                                      'PYTHON_BIN_PATH',
                                                      ask_python_bin_path,
                                                      default_python_bin_path)
    # Check if the path is valid
    if os.path.isfile(python_bin_path) and os.access(python_bin_path, os.X_OK):
      break
    elif not os.path.exists(python_bin_path):
      print('Invalid python path: %s cannot be found.' % python_bin_path)
    else:
      print('%s is not executable.  Is it the python binary?' % python_bin_path)
    environ_cp['PYTHON_BIN_PATH'] = ''

  # Convert python path to Windows style before checking lib and version
  if is_windows() or is_cygwin():
    python_bin_path = cygpath(python_bin_path)

  # Get PYTHON_LIB_PATH
  python_lib_path = environ_cp.get('PYTHON_LIB_PATH')
  if not python_lib_path:
    python_lib_paths = get_python_path(environ_cp, python_bin_path)
    if environ_cp.get('USE_DEFAULT_PYTHON_LIB_PATH') == '1':
      python_lib_path = python_lib_paths[0]
    else:
      print('Found possible Python library paths:\n  %s' %
            '\n  '.join(python_lib_paths))
      default_python_lib_path = python_lib_paths[0]
      python_lib_path = get_input(
          'Please input the desired Python library path to use.  '
          'Default is [%s]\n' % python_lib_paths[0])
      if not python_lib_path:
        python_lib_path = default_python_lib_path
    environ_cp['PYTHON_LIB_PATH'] = python_lib_path

  python_major_version = get_python_major_version(python_bin_path)
  if python_major_version == '2':
    write_to_bazelrc('build --host_force_python=PY2')

  # Convert python path to Windows style before writing into bazel.rc
  if is_windows() or is_cygwin():
    python_lib_path = cygpath(python_lib_path)

  # Set-up env variables used by python_configure.bzl
  write_action_env_to_bazelrc('PYTHON_BIN_PATH', python_bin_path)
  write_action_env_to_bazelrc('PYTHON_LIB_PATH', python_lib_path)
  write_to_bazelrc('build --python_path=\"%s"' % python_bin_path)
  environ_cp['PYTHON_BIN_PATH'] = python_bin_path

  # If choosen python_lib_path is from a path specified in the PYTHONPATH
  # variable, need to tell bazel to include PYTHONPATH
  if environ_cp.get('PYTHONPATH'):
    python_paths = environ_cp.get('PYTHONPATH').split(':')
    if python_lib_path in python_paths:
      write_action_env_to_bazelrc('PYTHONPATH', environ_cp.get('PYTHONPATH'))

  # Write tools/python_bin_path.sh
  with open(
      os.path.join(_TF_WORKSPACE_ROOT, 'tools', 'python_bin_path.sh'),
      'w') as f:
    f.write('export PYTHON_BIN_PATH="%s"' % python_bin_path)


def reset_tf_configure_bazelrc():
  """Reset file that contains customized config settings."""
  open(_TF_BAZELRC, 'w').close()


def cleanup_makefile():
  """Delete any leftover BUILD files from the Makefile build.

  These files could interfere with Bazel parsing.
  """
  makefile_download_dir = os.path.join(_TF_WORKSPACE_ROOT, 'tensorflow',
                                       'contrib', 'makefile', 'downloads')
  if os.path.isdir(makefile_download_dir):
    for root, _, filenames in os.walk(makefile_download_dir):
      for f in filenames:
        if f.endswith('BUILD'):
          os.remove(os.path.join(root, f))


def get_var(environ_cp,
            var_name,
            query_item,
            enabled_by_default,
            question=None,
            yes_reply=None,
            no_reply=None):
  """Get boolean input from user.

  If var_name is not set in env, ask user to enable query_item or not. If the
  response is empty, use the default.

  Args:
    environ_cp: copy of the os.environ.
    var_name: string for name of environment variable, e.g. "TF_NEED_CUDA".
    query_item: string for feature related to the variable, e.g. "CUDA for
      Nvidia GPUs".
    enabled_by_default: boolean for default behavior.
    question: optional string for how to ask for user input.
    yes_reply: optional string for reply when feature is enabled.
    no_reply: optional string for reply when feature is disabled.

  Returns:
    boolean value of the variable.

  Raises:
    UserInputError: if an environment variable is set, but it cannot be
      interpreted as a boolean indicator, assume that the user has made a
      scripting error, and will continue to provide invalid input.
      Raise the error to avoid infinitely looping.
  """
  if not question:
    question = 'Do you wish to build TensorFlow with %s support?' % query_item
  if not yes_reply:
    yes_reply = '%s support will be enabled for TensorFlow.' % query_item
  if not no_reply:
    no_reply = 'No %s' % yes_reply

  yes_reply += '\n'
  no_reply += '\n'

  if enabled_by_default:
    question += ' [Y/n]: '
  else:
    question += ' [y/N]: '

  var = environ_cp.get(var_name)
  if var is not None:
    var_content = var.strip().lower()
    true_strings = ('1', 't', 'true', 'y', 'yes')
    false_strings = ('0', 'f', 'false', 'n', 'no')
    if var_content in true_strings:
      var = True
    elif var_content in false_strings:
      var = False
    else:
      raise UserInputError(
          'Environment variable %s must be set as a boolean indicator.\n'
          'The following are accepted as TRUE : %s.\n'
          'The following are accepted as FALSE: %s.\n'
          'Current value is %s.' %
          (var_name, ', '.join(true_strings), ', '.join(false_strings), var))

  while var is None:
    user_input_origin = get_input(question)
    user_input = user_input_origin.strip().lower()
    if user_input == 'y':
      print(yes_reply)
      var = True
    elif user_input == 'n':
      print(no_reply)
      var = False
    elif not user_input:
      if enabled_by_default:
        print(yes_reply)
        var = True
      else:
        print(no_reply)
        var = False
    else:
      print('Invalid selection: %s' % user_input_origin)
  return var


def set_build_var(environ_cp,
                  var_name,
                  query_item,
                  option_name,
                  enabled_by_default,
                  bazel_config_name=None):
  """Set if query_item will be enabled for the build.

  Ask user if query_item will be enabled. Default is used if no input is given.
  Set subprocess environment variable and write to .bazelrc if enabled.

  Args:
    environ_cp: copy of the os.environ.
    var_name: string for name of environment variable, e.g. "TF_NEED_CUDA".
    query_item: string for feature related to the variable, e.g. "CUDA for
      Nvidia GPUs".
    option_name: string for option to define in .bazelrc.
    enabled_by_default: boolean for default behavior.
    bazel_config_name: Name for Bazel --config argument to enable build feature.
  """

  var = str(int(get_var(environ_cp, var_name, query_item, enabled_by_default)))
  environ_cp[var_name] = var
  if var == '1':
    write_to_bazelrc('build:%s --define %s=true' %
                     (bazel_config_name, option_name))
    write_to_bazelrc('build --config=%s' % bazel_config_name)
  elif bazel_config_name is not None:
    # TODO(mikecase): Migrate all users of configure.py to use --config Bazel
    # options and not to set build configs through environment variables.
    write_to_bazelrc('build:%s --define %s=true' %
                     (bazel_config_name, option_name))


def set_action_env_var(environ_cp,
                       var_name,
                       query_item,
                       enabled_by_default,
                       question=None,
                       yes_reply=None,
                       no_reply=None,
                       bazel_config_name=None):
  """Set boolean action_env variable.

  Ask user if query_item will be enabled. Default is used if no input is given.
  Set environment variable and write to .bazelrc.

  Args:
    environ_cp: copy of the os.environ.
    var_name: string for name of environment variable, e.g. "TF_NEED_CUDA".
    query_item: string for feature related to the variable, e.g. "CUDA for
      Nvidia GPUs".
    enabled_by_default: boolean for default behavior.
    question: optional string for how to ask for user input.
    yes_reply: optional string for reply when feature is enabled.
    no_reply: optional string for reply when feature is disabled.
    bazel_config_name: adding config to .bazelrc instead of action_env.
  """
  var = int(
      get_var(environ_cp, var_name, query_item, enabled_by_default, question,
              yes_reply, no_reply))

  if not bazel_config_name:
    write_action_env_to_bazelrc(var_name, var)
  elif var:
    write_to_bazelrc('build --config=%s' % bazel_config_name)
  environ_cp[var_name] = str(var)


def convert_version_to_int(version):
  """Convert a version number to a integer that can be used to compare.

  Version strings of the form X.YZ and X.Y.Z-xxxxx are supported. The
  'xxxxx' part, for instance 'homebrew' on OS/X, is ignored.

  Args:
    version: a version to be converted

  Returns:
    An integer if converted successfully, otherwise return None.
  """
  version = version.split('-')[0]
  version_segments = version.split('.')
  # Treat "0.24" as "0.24.0"
  if len(version_segments) == 2:
    version_segments.append('0')
  for seg in version_segments:
    if not seg.isdigit():
      return None

  version_str = ''.join(['%03d' % int(seg) for seg in version_segments])
  return int(version_str)


def check_bazel_version(min_version, max_version):
  """Check installed bazel version is between min_version and max_version.

  Args:
    min_version: string for minimum bazel version (must exist!).
    max_version: string for maximum bazel version (must exist!).

  Returns:
    The bazel version detected.
  """
  if which('bazel') is None:
    print('Cannot find bazel. Please install bazel.')
    sys.exit(0)
  curr_version = run_shell(
      ['bazel', '--batch', '--bazelrc=/dev/null', 'version'])

  for line in curr_version.split('\n'):
    if 'Build label: ' in line:
      curr_version = line.split('Build label: ')[1]
      break

  min_version_int = convert_version_to_int(min_version)
  curr_version_int = convert_version_to_int(curr_version)
  max_version_int = convert_version_to_int(max_version)

  # Check if current bazel version can be detected properly.
  if not curr_version_int:
    print('WARNING: current bazel installation is not a release version.')
    print('Make sure you are running at least bazel %s' % min_version)
    return curr_version

  print('You have bazel %s installed.' % curr_version)

  if curr_version_int < min_version_int:
    print('Please upgrade your bazel installation to version %s or higher to '
          'build TensorFlow!' % min_version)
    sys.exit(1)
  if (curr_version_int > max_version_int and
      'TF_IGNORE_MAX_BAZEL_VERSION' not in os.environ):
    print('Please downgrade your bazel installation to version %s or lower to '
          'build TensorFlow! To downgrade: download the installer for the old '
          'version (from https://github.com/bazelbuild/bazel/releases) then '
          'run the installer.' % max_version)
    sys.exit(1)
  return curr_version


def set_cc_opt_flags(environ_cp):
  """Set up architecture-dependent optimization flags.

  Also append CC optimization flags to bazel.rc..

  Args:
    environ_cp: copy of the os.environ.
  """
  if is_ppc64le():
    # gcc on ppc64le does not support -march, use mcpu instead
    default_cc_opt_flags = '-mcpu=native'
  elif is_windows():
    default_cc_opt_flags = '/arch:AVX'
  else:
    default_cc_opt_flags = '-march=native -Wno-sign-compare'
  question = ('Please specify optimization flags to use during compilation when'
              ' bazel option "--config=opt" is specified [Default is %s]: '
             ) % default_cc_opt_flags
  cc_opt_flags = get_from_env_or_user_or_default(environ_cp, 'CC_OPT_FLAGS',
                                                 question, default_cc_opt_flags)
  for opt in cc_opt_flags.split():
    write_to_bazelrc('build:opt --copt=%s' % opt)
  # It should be safe on the same build host.
  if not is_ppc64le() and not is_windows():
    write_to_bazelrc('build:opt --host_copt=-march=native')
  write_to_bazelrc('build:opt --define with_default_optimizations=true')


def set_tf_cuda_clang(environ_cp):
  """set TF_CUDA_CLANG action_env.

  Args:
    environ_cp: copy of the os.environ.
  """
  question = 'Do you want to use clang as CUDA compiler?'
  yes_reply = 'Clang will be used as CUDA compiler.'
  no_reply = 'nvcc will be used as CUDA compiler.'
  set_action_env_var(
      environ_cp,
      'TF_CUDA_CLANG',
      None,
      False,
      question=question,
      yes_reply=yes_reply,
      no_reply=no_reply,
      bazel_config_name='cuda_clang')


def set_tf_download_clang(environ_cp):
  """Set TF_DOWNLOAD_CLANG action_env."""
  question = 'Do you wish to download a fresh release of clang? (Experimental)'
  yes_reply = 'Clang will be downloaded and used to compile tensorflow.'
  no_reply = 'Clang will not be downloaded.'
  set_action_env_var(
      environ_cp,
      'TF_DOWNLOAD_CLANG',
      None,
      False,
      question=question,
      yes_reply=yes_reply,
      no_reply=no_reply,
      bazel_config_name='download_clang')


def get_from_env_or_user_or_default(environ_cp, var_name, ask_for_var,
                                    var_default):
  """Get var_name either from env, or user or default.

  If var_name has been set as environment variable, use the preset value, else
  ask for user input. If no input is provided, the default is used.

  Args:
    environ_cp: copy of the os.environ.
    var_name: string for name of environment variable, e.g. "TF_NEED_CUDA".
    ask_for_var: string for how to ask for user input.
    var_default: default value string.

  Returns:
    string value for var_name
  """
  var = environ_cp.get(var_name)
  if not var:
    var = get_input(ask_for_var)
    print('\n')
  if not var:
    var = var_default
  return var


def set_clang_cuda_compiler_path(environ_cp):
  """Set CLANG_CUDA_COMPILER_PATH."""
  default_clang_path = which('clang') or ''
  ask_clang_path = ('Please specify which clang should be used as device and '
                    'host compiler. [Default is %s]: ') % default_clang_path

  while True:
    clang_cuda_compiler_path = get_from_env_or_user_or_default(
        environ_cp, 'CLANG_CUDA_COMPILER_PATH', ask_clang_path,
        default_clang_path)
    if os.path.exists(clang_cuda_compiler_path):
      break

    # Reset and retry
    print('Invalid clang path: %s cannot be found.' % clang_cuda_compiler_path)
    environ_cp['CLANG_CUDA_COMPILER_PATH'] = ''

  # Set CLANG_CUDA_COMPILER_PATH
  environ_cp['CLANG_CUDA_COMPILER_PATH'] = clang_cuda_compiler_path
  write_action_env_to_bazelrc('CLANG_CUDA_COMPILER_PATH',
                              clang_cuda_compiler_path)


def prompt_loop_or_load_from_env(environ_cp,
                                 var_name,
                                 var_default,
                                 ask_for_var,
                                 check_success,
                                 error_msg,
                                 suppress_default_error=False,
                                 resolve_symlinks=False,
                                 n_ask_attempts=_DEFAULT_PROMPT_ASK_ATTEMPTS):
  """Loop over user prompts for an ENV param until receiving a valid response.

  For the env param var_name, read from the environment or verify user input
  until receiving valid input. When done, set var_name in the environ_cp to its
  new value.

  Args:
    environ_cp: (Dict) copy of the os.environ.
    var_name: (String) string for name of environment variable, e.g. "TF_MYVAR".
    var_default: (String) default value string.
    ask_for_var: (String) string for how to ask for user input.
    check_success: (Function) function that takes one argument and returns a
      boolean. Should return True if the value provided is considered valid. May
      contain a complex error message if error_msg does not provide enough
      information. In that case, set suppress_default_error to True.
    error_msg: (String) String with one and only one '%s'. Formatted with each
      invalid response upon check_success(input) failure.
    suppress_default_error: (Bool) Suppress the above error message in favor of
      one from the check_success function.
    resolve_symlinks: (Bool) Translate symbolic links into the real filepath.
    n_ask_attempts: (Integer) Number of times to query for valid input before
      raising an error and quitting.

  Returns:
    [String] The value of var_name after querying for input.

  Raises:
    UserInputError: if a query has been attempted n_ask_attempts times without
      success, assume that the user has made a scripting error, and will
      continue to provide invalid input. Raise the error to avoid infinitely
      looping.
  """
  default = environ_cp.get(var_name) or var_default
  full_query = '%s [Default is %s]: ' % (
      ask_for_var,
      default,
  )

  for _ in range(n_ask_attempts):
    val = get_from_env_or_user_or_default(environ_cp, var_name, full_query,
                                          default)
    if check_success(val):
      break
    if not suppress_default_error:
      print(error_msg % val)
    environ_cp[var_name] = ''
  else:
    raise UserInputError('Invalid %s setting was provided %d times in a row. '
                         'Assuming to be a scripting mistake.' %
                         (var_name, n_ask_attempts))

  if resolve_symlinks and os.path.islink(val):
    val = os.path.realpath(val)
  environ_cp[var_name] = val
  return val


def create_android_ndk_rule(environ_cp):
  """Set ANDROID_NDK_HOME and write Android NDK WORKSPACE rule."""
  if is_windows() or is_cygwin():
    default_ndk_path = cygpath('%s/Android/Sdk/ndk-bundle' %
                               environ_cp['APPDATA'])
  elif is_macos():
    default_ndk_path = '%s/library/Android/Sdk/ndk-bundle' % environ_cp['HOME']
  else:
    default_ndk_path = '%s/Android/Sdk/ndk-bundle' % environ_cp['HOME']

  def valid_ndk_path(path):
    return (os.path.exists(path) and
            os.path.exists(os.path.join(path, 'source.properties')))

  android_ndk_home_path = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='ANDROID_NDK_HOME',
      var_default=default_ndk_path,
      ask_for_var='Please specify the home path of the Android NDK to use.',
      check_success=valid_ndk_path,
      error_msg=('The path %s or its child file "source.properties" '
                 'does not exist.'))
  write_action_env_to_bazelrc('ANDROID_NDK_HOME', android_ndk_home_path)
  write_action_env_to_bazelrc(
      'ANDROID_NDK_API_LEVEL',
      get_ndk_api_level(environ_cp, android_ndk_home_path))


def create_android_sdk_rule(environ_cp):
  """Set Android variables and write Android SDK WORKSPACE rule."""
  if is_windows() or is_cygwin():
    default_sdk_path = cygpath('%s/Android/Sdk' % environ_cp['APPDATA'])
  elif is_macos():
    default_sdk_path = '%s/library/Android/Sdk' % environ_cp['HOME']
  else:
    default_sdk_path = '%s/Android/Sdk' % environ_cp['HOME']

  def valid_sdk_path(path):
    return (os.path.exists(path) and
            os.path.exists(os.path.join(path, 'platforms')) and
            os.path.exists(os.path.join(path, 'build-tools')))

  android_sdk_home_path = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='ANDROID_SDK_HOME',
      var_default=default_sdk_path,
      ask_for_var='Please specify the home path of the Android SDK to use.',
      check_success=valid_sdk_path,
      error_msg=('Either %s does not exist, or it does not contain the '
                 'subdirectories "platforms" and "build-tools".'))

  platforms = os.path.join(android_sdk_home_path, 'platforms')
  api_levels = sorted(os.listdir(platforms))
  api_levels = [x.replace('android-', '') for x in api_levels]

  def valid_api_level(api_level):
    return os.path.exists(
        os.path.join(android_sdk_home_path, 'platforms',
                     'android-' + api_level))

  android_api_level = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='ANDROID_API_LEVEL',
      var_default=api_levels[-1],
      ask_for_var=('Please specify the Android SDK API level to use. '
                   '[Available levels: %s]') % api_levels,
      check_success=valid_api_level,
      error_msg='Android-%s is not present in the SDK path.')

  build_tools = os.path.join(android_sdk_home_path, 'build-tools')
  versions = sorted(os.listdir(build_tools))

  def valid_build_tools(version):
    return os.path.exists(
        os.path.join(android_sdk_home_path, 'build-tools', version))

  android_build_tools_version = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='ANDROID_BUILD_TOOLS_VERSION',
      var_default=versions[-1],
      ask_for_var=('Please specify an Android build tools version to use. '
                   '[Available versions: %s]') % versions,
      check_success=valid_build_tools,
      error_msg=('The selected SDK does not have build-tools version %s '
                 'available.'))

  write_action_env_to_bazelrc('ANDROID_BUILD_TOOLS_VERSION',
                              android_build_tools_version)
  write_action_env_to_bazelrc('ANDROID_SDK_API_LEVEL', android_api_level)
  write_action_env_to_bazelrc('ANDROID_SDK_HOME', android_sdk_home_path)


def get_ndk_api_level(environ_cp, android_ndk_home_path):
  """Gets the appropriate NDK API level to use for the provided Android NDK path."""

  # First check to see if we're using a blessed version of the NDK.
  properties_path = '%s/source.properties' % android_ndk_home_path
  if is_windows() or is_cygwin():
    properties_path = cygpath(properties_path)
  with open(properties_path, 'r') as f:
    filedata = f.read()

  revision = re.search(r'Pkg.Revision = (\d+)', filedata)
  if revision:
    ndk_version = revision.group(1)
  else:
    raise Exception('Unable to parse NDK revision.')
  if int(ndk_version) not in _SUPPORTED_ANDROID_NDK_VERSIONS:
    print('WARNING: The NDK version in %s is %s, which is not '
          'supported by Bazel (officially supported versions: %s). Please use '
          'another version. Compiling Android targets may result in confusing '
          'errors.\n' %
          (android_ndk_home_path, ndk_version, _SUPPORTED_ANDROID_NDK_VERSIONS))

  # Now grab the NDK API level to use. Note that this is different from the
  # SDK API level, as the NDK API level is effectively the *min* target SDK
  # version.
  platforms = os.path.join(android_ndk_home_path, 'platforms')
  api_levels = sorted(os.listdir(platforms))
  api_levels = [
      x.replace('android-', '') for x in api_levels if 'android-' in x
  ]

  def valid_api_level(api_level):
    return os.path.exists(
        os.path.join(android_ndk_home_path, 'platforms',
                     'android-' + api_level))

  android_ndk_api_level = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='ANDROID_NDK_API_LEVEL',
      var_default='21',  # 21 is required for ARM64 support.
      ask_for_var=('Please specify the (min) Android NDK API level to use. '
                   '[Available levels: %s]') % api_levels,
      check_success=valid_api_level,
      error_msg='Android-%s is not present in the NDK path.')

  return android_ndk_api_level


def set_gcc_host_compiler_path(environ_cp):
  """Set GCC_HOST_COMPILER_PATH."""
  default_gcc_host_compiler_path = which('gcc') or ''
  cuda_bin_symlink = '%s/bin/gcc' % environ_cp.get('CUDA_TOOLKIT_PATH')

  if os.path.islink(cuda_bin_symlink):
    # os.readlink is only available in linux
    default_gcc_host_compiler_path = os.path.realpath(cuda_bin_symlink)

  gcc_host_compiler_path = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='GCC_HOST_COMPILER_PATH',
      var_default=default_gcc_host_compiler_path,
      ask_for_var='Please specify which gcc should be used by nvcc as the host compiler.',
      check_success=os.path.exists,
      resolve_symlinks=True,
      error_msg='Invalid gcc path. %s cannot be found.',
  )

  write_action_env_to_bazelrc('GCC_HOST_COMPILER_PATH', gcc_host_compiler_path)


def reformat_version_sequence(version_str, sequence_count):
  """Reformat the version string to have the given number of sequences.

  For example:
  Given (7, 2) -> 7.0
        (7.0.1, 2) -> 7.0
        (5, 1) -> 5
        (5.0.3.2, 1) -> 5

  Args:
      version_str: String, the version string.
      sequence_count: int, an integer.

  Returns:
      string, reformatted version string.
  """
  v = version_str.split('.')
  if len(v) < sequence_count:
    v = v + (['0'] * (sequence_count - len(v)))

  return '.'.join(v[:sequence_count])


def set_tf_cuda_paths(environ_cp):
  """Set TF_CUDA_PATHS."""
  ask_cuda_paths = (
      'Please specify the comma-separated list of base paths to look for CUDA '
      'libraries and headers. [Leave empty to use the default]: ')
  tf_cuda_paths = get_from_env_or_user_or_default(environ_cp, 'TF_CUDA_PATHS',
                                                  ask_cuda_paths, '')
  if tf_cuda_paths:
    environ_cp['TF_CUDA_PATHS'] = tf_cuda_paths


def set_tf_cuda_version(environ_cp):
  """Set TF_CUDA_VERSION."""
  ask_cuda_version = (
      'Please specify the CUDA SDK version you want to use. '
      '[Leave empty to default to CUDA %s]: ') % _DEFAULT_CUDA_VERSION
  tf_cuda_version = get_from_env_or_user_or_default(environ_cp,
                                                    'TF_CUDA_VERSION',
                                                    ask_cuda_version,
                                                    _DEFAULT_CUDA_VERSION)
  environ_cp['TF_CUDA_VERSION'] = tf_cuda_version


def set_tf_cudnn_version(environ_cp):
  """Set TF_CUDNN_VERSION."""
  ask_cudnn_version = (
      'Please specify the cuDNN version you want to use. '
      '[Leave empty to default to cuDNN %s]: ') % _DEFAULT_CUDNN_VERSION
  tf_cudnn_version = get_from_env_or_user_or_default(environ_cp,
                                                     'TF_CUDNN_VERSION',
                                                     ask_cudnn_version,
                                                     _DEFAULT_CUDNN_VERSION)
  environ_cp['TF_CUDNN_VERSION'] = tf_cudnn_version


def is_cuda_compatible(lib, cuda_ver, cudnn_ver):
  """Check compatibility between given library and cudnn/cudart libraries."""
  ldd_bin = which('ldd') or '/usr/bin/ldd'
  ldd_out = run_shell([ldd_bin, lib], True)
  ldd_out = ldd_out.split(os.linesep)
  cudnn_pattern = re.compile('.*libcudnn.so\\.?(.*) =>.*$')
  cuda_pattern = re.compile('.*libcudart.so\\.?(.*) =>.*$')
  cudnn = None
  cudart = None
  cudnn_ok = True  # assume no cudnn dependency by default
  cuda_ok = True  # assume no cuda dependency by default
  for line in ldd_out:
    if 'libcudnn.so' in line:
      cudnn = cudnn_pattern.search(line)
      cudnn_ok = False
    elif 'libcudart.so' in line:
      cudart = cuda_pattern.search(line)
      cuda_ok = False
  if cudnn and len(cudnn.group(1)):
    cudnn = convert_version_to_int(cudnn.group(1))
  if cudart and len(cudart.group(1)):
    cudart = convert_version_to_int(cudart.group(1))
  if cudnn is not None:
    cudnn_ok = (cudnn == cudnn_ver)
  if cudart is not None:
    cuda_ok = (cudart == cuda_ver)
  return cudnn_ok and cuda_ok


def set_tf_tensorrt_version(environ_cp):
  """Set TF_TENSORRT_VERSION."""
  if not is_linux():
    raise ValueError('Currently TensorRT is only supported on Linux platform.')

  if not int(environ_cp.get('TF_NEED_TENSORRT', False)):
    return

  ask_tensorrt_version = (
      'Please specify the TensorRT version you want to use. '
      '[Leave empty to default to TensorRT %s]: ') % _DEFAULT_TENSORRT_VERSION
  tf_tensorrt_version = get_from_env_or_user_or_default(
      environ_cp, 'TF_TENSORRT_VERSION', ask_tensorrt_version,
      _DEFAULT_TENSORRT_VERSION)
  environ_cp['TF_TENSORRT_VERSION'] = tf_tensorrt_version


def set_tf_nccl_version(environ_cp):
  """Set TF_NCCL_VERSION."""
  if not is_linux():
    raise ValueError('Currently NCCL is only supported on Linux platform.')

  if 'TF_NCCL_VERSION' in environ_cp:
    return

  ask_nccl_version = (
      'Please specify the locally installed NCCL version you want to use. '
      '[Leave empty to use http://github.com/nvidia/nccl]: ')
  tf_nccl_version = get_from_env_or_user_or_default(environ_cp,
                                                    'TF_NCCL_VERSION',
                                                    ask_nccl_version, '')
  environ_cp['TF_NCCL_VERSION'] = tf_nccl_version


def get_native_cuda_compute_capabilities(environ_cp):
  """Get native cuda compute capabilities.

  Args:
    environ_cp: copy of the os.environ.

  Returns:
    string of native cuda compute capabilities, separated by comma.
  """
  device_query_bin = os.path.join(
      environ_cp.get('CUDA_TOOLKIT_PATH'), 'extras/demo_suite/deviceQuery')
  if os.path.isfile(device_query_bin) and os.access(device_query_bin, os.X_OK):
    try:
      output = run_shell(device_query_bin).split('\n')
      pattern = re.compile('[0-9]*\\.[0-9]*')
      output = [pattern.search(x) for x in output if 'Capability' in x]
      output = ','.join(x.group() for x in output if x is not None)
    except subprocess.CalledProcessError:
      output = ''
  else:
    output = ''
  return output


def set_tf_cuda_compute_capabilities(environ_cp):
  """Set TF_CUDA_COMPUTE_CAPABILITIES."""
  while True:
    native_cuda_compute_capabilities = get_native_cuda_compute_capabilities(
        environ_cp)
    if not native_cuda_compute_capabilities:
      default_cuda_compute_capabilities = _DEFAULT_CUDA_COMPUTE_CAPABILITIES
    else:
      default_cuda_compute_capabilities = native_cuda_compute_capabilities

    ask_cuda_compute_capabilities = (
        'Please specify a list of comma-separated '
        'CUDA compute capabilities you want to '
        'build with.\nYou can find the compute '
        'capability of your device at: '
        'https://developer.nvidia.com/cuda-gpus.\nPlease'
        ' note that each additional compute '
        'capability significantly increases your '
        'build time and binary size, and that '
        'TensorFlow only supports compute '
        'capabilities >= 3.5 [Default is: %s]: ' %
        default_cuda_compute_capabilities)
    tf_cuda_compute_capabilities = get_from_env_or_user_or_default(
        environ_cp, 'TF_CUDA_COMPUTE_CAPABILITIES',
        ask_cuda_compute_capabilities, default_cuda_compute_capabilities)
    # Check whether all capabilities from the input is valid
    all_valid = True
    # Remove all whitespace characters before splitting the string
    # that users may insert by accident, as this will result in error
    tf_cuda_compute_capabilities = ''.join(tf_cuda_compute_capabilities.split())
    for compute_capability in tf_cuda_compute_capabilities.split(','):
      m = re.match('[0-9]+.[0-9]+', compute_capability)
      if not m:
        print('Invalid compute capability: %s' % compute_capability)
        all_valid = False
      else:
        ver = float(m.group(0))
        if ver < 3.0:
          print('ERROR: TensorFlow only supports CUDA compute capabilities 3.0 '
                'and higher. Please re-specify the list of compute '
                'capabilities excluding version %s.' % ver)
          all_valid = False
        if ver < 3.5:
          print('WARNING: XLA does not support CUDA compute capabilities '
                'lower than 3.5. Disable XLA when running on older GPUs.')

    if all_valid:
      break

    # Reset and Retry
    environ_cp['TF_CUDA_COMPUTE_CAPABILITIES'] = ''

  # Set TF_CUDA_COMPUTE_CAPABILITIES
  environ_cp['TF_CUDA_COMPUTE_CAPABILITIES'] = tf_cuda_compute_capabilities
  write_action_env_to_bazelrc('TF_CUDA_COMPUTE_CAPABILITIES',
                              tf_cuda_compute_capabilities)


def set_other_cuda_vars(environ_cp):
  """Set other CUDA related variables."""
  # If CUDA is enabled, always use GPU during build and test.
  if environ_cp.get('TF_CUDA_CLANG') == '1':
    write_to_bazelrc('build --config=cuda_clang')
  else:
    write_to_bazelrc('build --config=cuda')


def set_host_cxx_compiler(environ_cp):
  """Set HOST_CXX_COMPILER."""
  default_cxx_host_compiler = which('g++') or ''

  host_cxx_compiler = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='HOST_CXX_COMPILER',
      var_default=default_cxx_host_compiler,
      ask_for_var=('Please specify which C++ compiler should be used as the '
                   'host C++ compiler.'),
      check_success=os.path.exists,
      error_msg='Invalid C++ compiler path. %s cannot be found.',
  )

  write_action_env_to_bazelrc('HOST_CXX_COMPILER', host_cxx_compiler)


def set_host_c_compiler(environ_cp):
  """Set HOST_C_COMPILER."""
  default_c_host_compiler = which('gcc') or ''

  host_c_compiler = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='HOST_C_COMPILER',
      var_default=default_c_host_compiler,
      ask_for_var=('Please specify which C compiler should be used as the host '
                   'C compiler.'),
      check_success=os.path.exists,
      error_msg='Invalid C compiler path. %s cannot be found.',
  )

  write_action_env_to_bazelrc('HOST_C_COMPILER', host_c_compiler)


def set_computecpp_toolkit_path(environ_cp):
  """Set COMPUTECPP_TOOLKIT_PATH."""

  def toolkit_exists(toolkit_path):
    """Check if a computecpp toolkit path is valid."""
    if is_linux():
      sycl_rt_lib_path = 'lib/libComputeCpp.so'
    else:
      sycl_rt_lib_path = ''

    sycl_rt_lib_path_full = os.path.join(toolkit_path, sycl_rt_lib_path)
    exists = os.path.exists(sycl_rt_lib_path_full)
    if not exists:
      print('Invalid SYCL %s library path. %s cannot be found' %
            (_TF_OPENCL_VERSION, sycl_rt_lib_path_full))
    return exists

  computecpp_toolkit_path = prompt_loop_or_load_from_env(
      environ_cp,
      var_name='COMPUTECPP_TOOLKIT_PATH',
      var_default=_DEFAULT_COMPUTECPP_TOOLKIT_PATH,
      ask_for_var=(
          'Please specify the location where ComputeCpp for SYCL %s is '
          'installed.' % _TF_OPENCL_VERSION),
      check_success=toolkit_exists,
      error_msg='Invalid SYCL compiler path. %s cannot be found.',
      suppress_default_error=True)

  write_action_env_to_bazelrc('COMPUTECPP_TOOLKIT_PATH',
                              computecpp_toolkit_path)


def set_trisycl_include_dir(environ_cp):
  """Set TRISYCL_INCLUDE_DIR."""

  ask_trisycl_include_dir = ('Please specify the location of the triSYCL '
                             'include directory. (Use --config=sycl_trisycl '
                             'when building with Bazel) '
                             '[Default is %s]: ') % (
                                 _DEFAULT_TRISYCL_INCLUDE_DIR)

  while True:
    trisycl_include_dir = get_from_env_or_user_or_default(
        environ_cp, 'TRISYCL_INCLUDE_DIR', ask_trisycl_include_dir,
        _DEFAULT_TRISYCL_INCLUDE_DIR)
    if os.path.exists(trisycl_include_dir):
      break

    print('Invalid triSYCL include directory, %s cannot be found' %
          (trisycl_include_dir))

  # Set TRISYCL_INCLUDE_DIR
  environ_cp['TRISYCL_INCLUDE_DIR'] = trisycl_include_dir
  write_action_env_to_bazelrc('TRISYCL_INCLUDE_DIR', trisycl_include_dir)


def system_specific_test_config(env):
  """Add default build and test flags required for TF tests to bazelrc."""
  write_to_bazelrc('test --flaky_test_attempts=3')
  write_to_bazelrc('test --test_size_filters=small,medium')

  # Each instance of --test_tag_filters or --build_tag_filters overrides all
  # previous instances, so we need to build up a complete list and write a
  # single list of filters for the .bazelrc file.

  # Filters to use with both --test_tag_filters and --build_tag_filters
  test_and_build_filters = ['-benchmark-test', '-no_oss']
  # Additional filters for --test_tag_filters beyond those in
  # test_and_build_filters
  test_only_filters = ['-oss_serial']
  if is_windows():
    test_and_build_filters.append('-no_windows')
    if env.get('TF_NEED_CUDA', None) == '1':
      test_and_build_filters += ['-no_windows_gpu', '-no_gpu']
    else:
      test_and_build_filters.append('-gpu')
  elif is_macos():
    test_and_build_filters += ['-gpu', '-nomac', '-no_mac']
  elif is_linux():
    if env.get('TF_NEED_CUDA', None) == '1':
      test_and_build_filters.append('-no_gpu')
      write_to_bazelrc('test --test_env=LD_LIBRARY_PATH')
    else:
      test_and_build_filters.append('-gpu')

  # Disable tests with "v1only" tag in "v2" Bazel config, but not in "v1" config
  write_to_bazelrc('test:v1 --test_tag_filters=%s' %
                   ','.join(test_and_build_filters + test_only_filters))
  write_to_bazelrc('test:v1 --build_tag_filters=%s' %
                   ','.join(test_and_build_filters))
  write_to_bazelrc(
      'test:v2 --test_tag_filters=%s' %
      ','.join(test_and_build_filters + test_only_filters + ['-v1only']))
  write_to_bazelrc('test:v2 --build_tag_filters=%s' %
                   ','.join(test_and_build_filters + ['-v1only']))


def set_system_libs_flag(environ_cp):
  syslibs = environ_cp.get('TF_SYSTEM_LIBS', '')
  if syslibs:
    if ',' in syslibs:
      syslibs = ','.join(sorted(syslibs.split(',')))
    else:
      syslibs = ','.join(sorted(syslibs.split()))
    write_action_env_to_bazelrc('TF_SYSTEM_LIBS', syslibs)

  if 'PREFIX' in environ_cp:
    write_to_bazelrc('build --define=PREFIX=%s' % environ_cp['PREFIX'])
  if 'LIBDIR' in environ_cp:
    write_to_bazelrc('build --define=LIBDIR=%s' % environ_cp['LIBDIR'])
  if 'INCLUDEDIR' in environ_cp:
    write_to_bazelrc('build --define=INCLUDEDIR=%s' % environ_cp['INCLUDEDIR'])


def is_reduced_optimize_huge_functions_available(environ_cp):
  """Check to see if the system supports /d2ReducedOptimizeHugeFunctions.

  The above compiler flag is a new compiler flag introduced to the Visual Studio
  compiler in version 16.4 (available in Visual Studio 2019, Preview edition
  only, as of 2019-11-19). TensorFlow needs this flag to massively reduce
  compile times, but until 16.4 is officially released, we can't depend on it.

  See also https://groups.google.com/a/tensorflow.org/g/build/c/SsW98Eo7l3o

  Because it's very annoying to check this manually (to check the MSVC installed
  versions, you need to use the registry, and it's not clear if Bazel will be
  using that install version anyway), we expect enviroments who know they may
  use this flag to export TF_VC_VERSION=16.4

  TODO(angerson, gunan): Remove this function when TensorFlow's minimum VS
  version is upgraded to 16.4.

  Arguments:
    environ_cp: Environment of the current execution

  Returns:
    boolean, whether or not /d2ReducedOptimizeHugeFunctions is available on this
    machine.
  """
  return float(environ_cp.get('TF_VC_VERSION', '0')) >= 16.4


def set_windows_build_flags(environ_cp):
  """Set Windows specific build options."""
  if is_reduced_optimize_huge_functions_available(environ_cp):
    write_to_bazelrc(
        'build --copt=/d2ReducedOptimizeHugeFunctions --host_copt=/d2ReducedOptimizeHugeFunctions'
    )

  if get_var(
      environ_cp, 'TF_OVERRIDE_EIGEN_STRONG_INLINE', 'Eigen strong inline',
      True, ('Would you like to override eigen strong inline for some C++ '
             'compilation to reduce the compilation time?'),
      'Eigen strong inline overridden.', 'Not overriding eigen strong inline, '
      'some compilations could take more than 20 mins.'):
    # Due to a known MSVC compiler issue
    # https://github.com/tensorflow/tensorflow/issues/10521
    # Overriding eigen strong inline speeds up the compiling of
    # conv_grad_ops_3d.cc and conv_ops_3d.cc by 20 minutes,
    # but this also hurts the performance. Let users decide what they want.
    write_to_bazelrc('build --define=override_eigen_strong_inline=true')


def config_info_line(name, help_text):
  """Helper function to print formatted help text for Bazel config options."""
  print('\t--config=%-12s\t# %s' % (name, help_text))


def configure_ios():
  """Configures TensorFlow for iOS builds.

  This function will only be executed if `is_macos()` is true.
  """
  if not is_macos():
    return
  for filepath in APPLE_BAZEL_FILES:
    existing_filepath = os.path.join(_TF_WORKSPACE_ROOT, filepath + '.apple')
    renamed_filepath = os.path.join(_TF_WORKSPACE_ROOT, filepath)
    symlink_force(existing_filepath, renamed_filepath)
  for filepath in IOS_FILES:
    filename = os.path.basename(filepath)
    new_filepath = os.path.join(_TF_WORKSPACE_ROOT, filename)
    symlink_force(filepath, new_filepath)


def validate_cuda_config(environ_cp):
  """Run find_cuda_config.py and return cuda_toolkit_path, or None."""

  def maybe_encode_env(env):
    """Encodes unicode in env to str on Windows python 2.x."""
    if not is_windows() or sys.version_info[0] != 2:
      return env
    for k, v in env.items():
      if isinstance(k, unicode):
        k = k.encode('ascii')
      if isinstance(v, unicode):
        v = v.encode('ascii')
      env[k] = v
    return env

  cuda_libraries = ['cuda', 'cudnn']
  if is_linux():
    if int(environ_cp.get('TF_NEED_TENSORRT', False)):
      cuda_libraries.append('tensorrt')
    if environ_cp.get('TF_NCCL_VERSION', None):
      cuda_libraries.append('nccl')

  proc = subprocess.Popen(
      [environ_cp['PYTHON_BIN_PATH'], 'third_party/gpus/find_cuda_config.py'] +
      cuda_libraries,
      stdout=subprocess.PIPE,
      env=maybe_encode_env(environ_cp))

  if proc.wait():
    # Errors from find_cuda_config.py were sent to stderr.
    print('Asking for detailed CUDA configuration...\n')
    return False

  config = dict(
      tuple(line.decode('ascii').rstrip().split(': ')) for line in proc.stdout)

  print('Found CUDA %s in:' % config['cuda_version'])
  print('    %s' % config['cuda_library_dir'])
  print('    %s' % config['cuda_include_dir'])

  print('Found cuDNN %s in:' % config['cudnn_version'])
  print('    %s' % config['cudnn_library_dir'])
  print('    %s' % config['cudnn_include_dir'])

  if 'tensorrt_version' in config:
    print('Found TensorRT %s in:' % config['tensorrt_version'])
    print('    %s' % config['tensorrt_library_dir'])
    print('    %s' % config['tensorrt_include_dir'])

  if config.get('nccl_version', None):
    print('Found NCCL %s in:' % config['nccl_version'])
    print('    %s' % config['nccl_library_dir'])
    print('    %s' % config['nccl_include_dir'])

  print('\n')

  environ_cp['CUDA_TOOLKIT_PATH'] = config['cuda_toolkit_path']
  return True


def main():
  global _TF_WORKSPACE_ROOT
  global _TF_BAZELRC
  global _TF_CURRENT_BAZEL_VERSION

  parser = argparse.ArgumentParser()
  parser.add_argument(
      '--workspace',
      type=str,
      default=os.path.abspath(os.path.dirname(__file__)),
      help='The absolute path to your active Bazel workspace.')
  args = parser.parse_args()

  _TF_WORKSPACE_ROOT = args.workspace
  _TF_BAZELRC = os.path.join(_TF_WORKSPACE_ROOT, _TF_BAZELRC_FILENAME)

  # Make a copy of os.environ to be clear when functions and getting and setting
  # environment variables.
  environ_cp = dict(os.environ)

  current_bazel_version = check_bazel_version(_TF_MIN_BAZEL_VERSION,
                                              _TF_MAX_BAZEL_VERSION)
  _TF_CURRENT_BAZEL_VERSION = convert_version_to_int(current_bazel_version)

  reset_tf_configure_bazelrc()

  cleanup_makefile()
  setup_python(environ_cp)

  if is_windows():
    environ_cp['TF_NEED_OPENCL_SYCL'] = '0'
    environ_cp['TF_NEED_COMPUTECPP'] = '0'
    environ_cp['TF_NEED_OPENCL'] = '0'
    environ_cp['TF_CUDA_CLANG'] = '0'
    environ_cp['TF_NEED_TENSORRT'] = '0'
    # TODO(ibiryukov): Investigate using clang as a cpu or cuda compiler on
    # Windows.
    environ_cp['TF_DOWNLOAD_CLANG'] = '0'
    environ_cp['TF_NEED_MPI'] = '0'
    environ_cp['TF_SET_ANDROID_WORKSPACE'] = '0'

  if is_macos():
    environ_cp['TF_NEED_TENSORRT'] = '0'
  else:
    environ_cp['TF_CONFIGURE_IOS'] = '0'

  xla_enabled_by_default = is_linux() or is_macos()
  set_build_var(environ_cp, 'TF_ENABLE_XLA', 'XLA JIT', 'with_xla_support',
                xla_enabled_by_default, 'xla')

  set_action_env_var(
      environ_cp,
      'TF_NEED_OPENCL_SYCL',
      'OpenCL SYCL',
      False,
      bazel_config_name='sycl')
  if environ_cp.get('TF_NEED_OPENCL_SYCL') == '1':
    set_host_cxx_compiler(environ_cp)
    set_host_c_compiler(environ_cp)
    set_action_env_var(environ_cp, 'TF_NEED_COMPUTECPP', 'ComputeCPP', True)
    if environ_cp.get('TF_NEED_COMPUTECPP') == '1':
      set_computecpp_toolkit_path(environ_cp)
    else:
      set_trisycl_include_dir(environ_cp)

  set_action_env_var(
      environ_cp, 'TF_NEED_ROCM', 'ROCm', False, bazel_config_name='rocm')
  if (environ_cp.get('TF_NEED_ROCM') == '1' and
      'LD_LIBRARY_PATH' in environ_cp and
      environ_cp.get('LD_LIBRARY_PATH') != '1'):
    write_action_env_to_bazelrc('LD_LIBRARY_PATH',
                                environ_cp.get('LD_LIBRARY_PATH'))

  environ_cp['TF_NEED_CUDA'] = str(
      int(get_var(environ_cp, 'TF_NEED_CUDA', 'CUDA', False)))
  if (environ_cp.get('TF_NEED_CUDA') == '1' and
      'TF_CUDA_CONFIG_REPO' not in environ_cp):

    set_action_env_var(
        environ_cp,
        'TF_NEED_TENSORRT',
        'TensorRT',
        False,
        bazel_config_name='tensorrt')

    environ_save = dict(environ_cp)
    for _ in range(_DEFAULT_PROMPT_ASK_ATTEMPTS):

      if validate_cuda_config(environ_cp):
        cuda_env_names = [
            'TF_CUDA_VERSION',
            'TF_CUBLAS_VERSION',
            'TF_CUDNN_VERSION',
            'TF_TENSORRT_VERSION',
            'TF_NCCL_VERSION',
            'TF_CUDA_PATHS',
            # Items below are for backwards compatibility when not using
            # TF_CUDA_PATHS.
            'CUDA_TOOLKIT_PATH',
            'CUDNN_INSTALL_PATH',
            'NCCL_INSTALL_PATH',
            'NCCL_HDR_PATH',
            'TENSORRT_INSTALL_PATH'
        ]
        # Note: set_action_env_var above already writes to bazelrc.
        for name in cuda_env_names:
          if name in environ_cp:
            write_action_env_to_bazelrc(name, environ_cp[name])
        break

      # Restore settings changed below if CUDA config could not be validated.
      environ_cp = dict(environ_save)

      set_tf_cuda_version(environ_cp)
      set_tf_cudnn_version(environ_cp)
      if is_linux():
        set_tf_tensorrt_version(environ_cp)
        set_tf_nccl_version(environ_cp)

      set_tf_cuda_paths(environ_cp)

    else:
      raise UserInputError(
          'Invalid CUDA setting were provided %d '
          'times in a row. Assuming to be a scripting mistake.' %
          _DEFAULT_PROMPT_ASK_ATTEMPTS)

    set_tf_cuda_compute_capabilities(environ_cp)
    if 'LD_LIBRARY_PATH' in environ_cp and environ_cp.get(
        'LD_LIBRARY_PATH') != '1':
      write_action_env_to_bazelrc('LD_LIBRARY_PATH',
                                  environ_cp.get('LD_LIBRARY_PATH'))

    set_tf_cuda_clang(environ_cp)
    if environ_cp.get('TF_CUDA_CLANG') == '1':
      # Ask whether we should download the clang toolchain.
      set_tf_download_clang(environ_cp)
      if environ_cp.get('TF_DOWNLOAD_CLANG') != '1':
        # Set up which clang we should use as the cuda / host compiler.
        set_clang_cuda_compiler_path(environ_cp)
      else:
        # Use downloaded LLD for linking.
        write_to_bazelrc('build:cuda_clang --config=download_clang_use_lld')
    else:
      # Set up which gcc nvcc should use as the host compiler
      # No need to set this on Windows
      if not is_windows():
        set_gcc_host_compiler_path(environ_cp)
    set_other_cuda_vars(environ_cp)
  else:
    # CUDA not required. Ask whether we should download the clang toolchain and
    # use it for the CPU build.
    set_tf_download_clang(environ_cp)

  # SYCL / ROCm / CUDA are mutually exclusive.
  # At most 1 GPU platform can be configured.
  gpu_platform_count = 0
  if environ_cp.get('TF_NEED_OPENCL_SYCL') == '1':
    gpu_platform_count += 1
  if environ_cp.get('TF_NEED_ROCM') == '1':
    gpu_platform_count += 1
  if environ_cp.get('TF_NEED_CUDA') == '1':
    gpu_platform_count += 1
  if gpu_platform_count >= 2:
    raise UserInputError('SYCL / CUDA / ROCm are mututally exclusive. '
                         'At most 1 GPU platform can be configured.')

  set_cc_opt_flags(environ_cp)
  set_system_libs_flag(environ_cp)
  if is_windows():
    set_windows_build_flags(environ_cp)

  if get_var(environ_cp, 'TF_SET_ANDROID_WORKSPACE', 'android workspace', False,
             ('Would you like to interactively configure ./WORKSPACE for '
              'Android builds?'), 'Searching for NDK and SDK installations.',
             'Not configuring the WORKSPACE for Android builds.'):
    create_android_ndk_rule(environ_cp)
    create_android_sdk_rule(environ_cp)

  system_specific_test_config(os.environ)

  set_action_env_var(environ_cp, 'TF_CONFIGURE_IOS', 'iOS', False)
  if environ_cp.get('TF_CONFIGURE_IOS') == '1':
    configure_ios()

  print('Preconfigured Bazel build configs. You can use any of the below by '
        'adding "--config=<>" to your build command. See .bazelrc for more '
        'details.')
  config_info_line('mkl', 'Build with MKL support.')
  config_info_line('monolithic', 'Config for mostly static monolithic build.')
  config_info_line('ngraph', 'Build with Intel nGraph support.')
  config_info_line('numa', 'Build with NUMA support.')
  config_info_line(
      'dynamic_kernels',
      '(Experimental) Build kernels into separate shared objects.')
  config_info_line('v2', 'Build TensorFlow 2.x instead of 1.x.')

  print('Preconfigured Bazel build configs to DISABLE default on features:')
  config_info_line('noaws', 'Disable AWS S3 filesystem support.')
  config_info_line('nogcp', 'Disable GCP support.')
  config_info_line('nohdfs', 'Disable HDFS support.')
  config_info_line('nonccl', 'Disable NVIDIA NCCL support.')


if __name__ == '__main__':
  main()