MakefileWriter.py

import hashlib
import os
import re

import gyp
from gyp import xcode_emulation
from gyp.common import GypError, EnsureDirExists
from gyp.generator.make import generator_default_variables,CalculateVariables

# The .d checking code below uses these functions:
# wildcard, sort, foreach, shell, wordlist
# wildcard can handle spaces, the rest can't.
# Since I could find no way to make foreach work with spaces in filenames
# correctly, the .d files have spaces replaced with another character. The .d
# file for
#     Chromium\ Framework.framework/foo
# is for example
#     out/Release/.deps/out/Release/Chromium?Framework.framework/foo
# This is the replacement character.
SPACE_REPLACEMENT = '?'

# Header of toplevel Makefile.
# This should go into the build tree, but it's easier to keep it here for now.
_dirname = os.path.dirname(os.path.abspath(__file__))
with open(os.path.join(_dirname, 'Makefile.tmpl'), 'rt') as f:
  file_content = f.read()
  SHARED_HEADER = file_content.format(SPACE_REPLACEMENT=SPACE_REPLACEMENT)

SHARED_HEADER_SUFFIX_RULES_COMMENT1 = ("""\
# Suffix rules, putting all outputs into $(obj).
""")

SHARED_HEADER_SUFFIX_RULES_COMMENT2 = ("""\
# Try building from generated source, too.
""")

header = """\
# This file is generated by gyp; do not edit.

"""

# Maps every compilable file extension to the do_cmd that compiles it.
COMPILABLE_EXTENSIONS = {
  '.c': 'cc',
  '.cc': 'cxx',
  '.cpp': 'cxx',
  '.cxx': 'cxx',
  '.s': 'cc',
  '.S': 'cc',
  '.m': 'objc',
  '.mm': 'objcxx',
}


def WriteRootHeaderSuffixRules(writer):
  extensions = sorted(COMPILABLE_EXTENSIONS.keys(), key=str.lower)

  writer.write('# Suffix rules, putting all outputs into $(obj).\n')
  for ext in extensions:
    writer.write('$(obj).$(TOOLSET)/%%.o: $(srcdir)/%%%s FORCE_DO_CMD\n' % ext)
    writer.write('\t@$(call do_cmd,%s,1)\n' % COMPILABLE_EXTENSIONS[ext])

  writer.write('\n# Try building from generated source, too.\n')
  for ext in extensions:
    writer.write('$(obj).$(TOOLSET)/%%.o: $(obj).$(TOOLSET)/%%%s FORCE_DO_CMD\n' % ext)
    writer.write('\t@$(call do_cmd,%s,1)\n' % COMPILABLE_EXTENSIONS[ext])
  writer.write('\n')
  for ext in extensions:
    writer.write('$(obj).$(TOOLSET)/%%.o: $(obj)/%%%s FORCE_DO_CMD\n' % ext)
    writer.write('\t@$(call do_cmd,%s,1)\n' % COMPILABLE_EXTENSIONS[ext])
  writer.write('\n')


def Compilable(filename):
  """Return true if the file is compilable (should be in OBJS)."""
  for res in (filename.endswith(e) for e in COMPILABLE_EXTENSIONS):
    if res:
      return True
  return False



# Map from qualified target to path to output.
target_outputs = {}
# Map from qualified target to any linkable output.  A subset
# of target_outputs.  E.g. when mybinary depends on liba, we want to
# include liba in the linker line; when otherbinary depends on
# mybinary, we just want to build mybinary first.
target_link_deps = {}


def Linkable(filename):
  """Return true if the file is linkable (should be on the link line)."""
  return filename.endswith('.o')


def Target(filename):
  """Translate a compilable filename to its .o target."""
  return os.path.splitext(filename)[0] + '.o'


def EscapeShellArgument(s):
  """
  Quotes an argument so that it will be interpreted literally by a POSIX shell.
  Taken from http://stackoverflow.com/questions/35817/whats-the-best-way-to-escape-ossystem-calls-in-python
  """
  return "'" + s.replace("'", "'\\''") + "'"


def EscapeMakeVariableExpansion(s):
  """Make has its own variable expansion syntax using $. We must escape it for string to be interpreted literally."""
  return s.replace('$', '$$')


def EscapeCppDefine(s):
  """Escapes a CPP define so that it will reach the compiler unaltered."""
  s = EscapeShellArgument(s)
  s = EscapeMakeVariableExpansion(s)
  # '#' characters must be escaped even embedded in a string, else Make will
  # treat it as the start of a comment.
  return s.replace('#', r'\#')


def QuoteIfNecessary(string):
  """TODO: Should this ideally be replaced with one or more of the above functions?"""
  if '"' in string:
    string = '"' + string.replace('"', '\\"') + '"'
  return string


def StringToMakefileVariable(string):
  """Convert a string to a value that is acceptable as a make variable name."""
  return re.sub('[^a-zA-Z0-9_]', '_', string)


def Sourceify(path):
  """Convert a path to its source directory form."""
  if '$(' in path:
    return path
  if os.path.isabs(path):
    return path
  return Sourceify.srcdir_prefix + path
Sourceify.srcdir_prefix = ''


def QuoteSpaces(s, quote=r'\ '):
  return s.replace(' ', quote)


# TODO: Avoid code duplication with _ValidateSourcesForMSVSProject in msvs.py.
def _ValidateSourcesForOSX(spec, all_sources):
  """
  Makes sure if duplicate basenames are not specified in the source list.

  Arguments:
    spec: The target dictionary containing the properties of the target.
  """
  if spec.get('type', None) != 'static_library':
    return

  basenames = {}
  for source in all_sources:
    name, ext = os.path.splitext(source)
    is_compiled_file = ext in ['.c', '.cc', '.cpp', '.cxx', '.m', '.mm', '.s', '.S']
    if not is_compiled_file:
      continue
    basename = os.path.basename(name)  # Don't include extension.
    basenames.setdefault(basename, []).append(source)

  error = ''
  for basename, files in basenames.items():
    if len(files) > 1:
      error += '  %s: %s\n' % (basename, ' '.join(files))

  if error:
    print('static library %s%s libtool on OS X will generate warnings for them. has several files with the same basename:\n' % (spec['target_name'], error))
    raise GypError('Duplicate basenames in sources section, see list above')


# noinspection PyAttributeOutsideInit
class MakefileWriter(object):
  """MakefileWriter packages up the writing of one target-specific foobar.mk.

  Its only real entry point is Write(), and is mostly used for namespacing.
  """

  def __init__(self, generator_flags, flavor):
    self.generator_flags = generator_flags
    self.flavor = flavor

    self.suffix_rules_srcdir = {}
    self.suffix_rules_objdir1 = {}
    self.suffix_rules_objdir2 = {}

    # Generate suffix rules for all compilable extensions.
    for ext in COMPILABLE_EXTENSIONS.keys():
      # Suffix rules for source folder.
      self.suffix_rules_srcdir.update({
        ext: ("""\
$(obj).$(TOOLSET)/$(TARGET)/%%.o: $(srcdir)/%%%s FORCE_DO_CMD
	@$(call do_cmd,%s,1)
""" % (ext, COMPILABLE_EXTENSIONS[ext]))
      })

      # Suffix rules for generated source files.
      self.suffix_rules_objdir1.update({
        ext: ("""\
$(obj).$(TOOLSET)/$(TARGET)/%%.o: $(obj).$(TOOLSET)/%%%s FORCE_DO_CMD
	@$(call do_cmd,%s,1)
""" % (ext, COMPILABLE_EXTENSIONS[ext]))
      })
      self.suffix_rules_objdir2.update({
        ext: ("""\
$(obj).$(TOOLSET)/$(TARGET)/%%.o: $(obj)/%%%s FORCE_DO_CMD
	@$(call do_cmd,%s,1)
""" % (ext, COMPILABLE_EXTENSIONS[ext]))
      })

  def Write(self, qualified_target, base_path, output_filename, spec, configs, part_of_all):
    """
    The main entry point: writes a .mk file for a single target.

    Arguments:
      qualified_target: target we're generating
      base_path: path relative to source root we're building in, used to resolve target-relative paths
      output_filename: output .mk file name to write
      spec: gyp info
      configs: gyp info
      part_of_all: flag indicating this target is part of 'all'
    """
    EnsureDirExists(output_filename)

    self.fp = open(output_filename, 'w')

    self.fp.write(header)

    self.qualified_target = qualified_target
    self.path = base_path
    self.target = spec['target_name']
    self.type = spec['type']
    self.toolset = spec['toolset']

    self.is_mac_bundle = xcode_emulation.IsMacBundle(self.flavor, spec)
    if self.flavor == 'mac':
      self.xcode_settings = xcode_emulation.XcodeSettings(spec)
    else:
      self.xcode_settings = None

    deps, link_deps = self.ComputeDeps(spec)

    # Some of the generation below can add extra output, sources, or
    # link dependencies.  All of the out params of the functions that
    # follow use names like extra_foo.
    extra_outputs = []
    extra_sources = []
    extra_link_deps = []
    extra_mac_bundle_resources = []
    mac_bundle_deps = []

    if self.is_mac_bundle:
      self.output = self.ComputeMacBundleOutput()
      self.output_binary = self.ComputeMacBundleBinaryOutput()
    else:
      self.output = self.output_binary = self.ComputeOutput(spec)

    self.is_standalone_static_library = bool(
      spec.get('standalone_static_library', 0))
    self._INSTALLABLE_TARGETS = ('executable', 'loadable_module', 'shared_library')
    if (self.is_standalone_static_library or
        self.type in self._INSTALLABLE_TARGETS):
      self.alias = os.path.basename(self.output)
      install_path = self._InstallableTargetInstallPath()
    else:
      self.alias = self.output
      install_path = self.output

    self.WriteLn("TOOLSET := " + self.toolset)
    self.WriteLn("TARGET := " + self.target)

    # Actions must come first, since they can generate more OBJs for use below.
    if 'actions' in spec:
      self.WriteActions(spec['actions'], extra_sources, extra_outputs,
                        extra_mac_bundle_resources, part_of_all)

    # Rules must be early like actions.
    if 'rules' in spec:
      self.WriteRules(spec['rules'], extra_sources, extra_outputs, extra_mac_bundle_resources)

    if 'copies' in spec:
      self.WriteCopies(spec['copies'], extra_outputs, part_of_all)

    # Bundle resources.
    if self.is_mac_bundle:
      all_mac_bundle_resources = spec.get('mac_bundle_resources', []) + extra_mac_bundle_resources
      self.WriteMacBundleResources(all_mac_bundle_resources, mac_bundle_deps)
      self.WriteMacInfoPlist(mac_bundle_deps)
      self.WriteMacBundleResources(all_mac_bundle_resources, mac_bundle_deps)

    # Sources.
    all_sources = spec.get('sources', []) + extra_sources
    if all_sources:
      if self.flavor == 'mac':
        # libtool on OS X generates warnings for duplicate basenames in the same
        # target.
        _ValidateSourcesForOSX(spec, all_sources)
      self.WriteSources(
        configs, deps, all_sources, extra_outputs, extra_link_deps,
        gyp.xcode_emulation.MacPrefixHeader(self.xcode_settings, lambda p: Sourceify(self.Absolutify(p)), self.Pchify)
      )
      sources = [x for x in all_sources if Compilable(x)]
      if sources:
        self.WriteLn(SHARED_HEADER_SUFFIX_RULES_COMMENT1)
        extensions = set([os.path.splitext(s)[1] for s in sources])
        for ext in extensions:
          if ext in self.suffix_rules_srcdir:
            self.WriteLn(self.suffix_rules_srcdir[ext])
        self.WriteLn(SHARED_HEADER_SUFFIX_RULES_COMMENT2)
        for ext in extensions:
          if ext in self.suffix_rules_objdir1:
            self.WriteLn(self.suffix_rules_objdir1[ext])
        for ext in extensions:
          if ext in self.suffix_rules_objdir2:
            self.WriteLn(self.suffix_rules_objdir2[ext])
        self.WriteLn('# End of this set of suffix rules')

        # Add dependency from bundle to bundle binary.
        if self.is_mac_bundle:
          mac_bundle_deps.append(self.output_binary)

    self.WriteTarget(spec, configs, deps, extra_link_deps + link_deps,
                     mac_bundle_deps, extra_outputs, part_of_all)

    # Update global list of target outputs, used in dependency tracking.
    target_outputs[qualified_target] = install_path

    # Update global list of link dependencies.
    if self.type in ('static_library', 'shared_library'):
      target_link_deps[qualified_target] = self.output_binary

    # Currently any versions have the same effect, but in future the behavior
    # could be different.
    if self.generator_flags.get('android_ndk_version', None):
      self.WriteAndroidNdkModuleRule(self.target, all_sources, link_deps)

    self.fp.close()

  def WriteSubMake(self, output_filename, makefile_path, targets, build_dir):
    """Write a "sub-project" Makefile.

    This is a small, wrapper Makefile that calls the top-level Makefile to build
    the targets from a single gyp file (i.e. a sub-project).

    Arguments:
      output_filename: sub-project Makefile name to write
      makefile_path: path to the top-level Makefile
      targets: list of "all" targets for this sub-project
      build_dir: build output directory, relative to the sub-project
    """
    gyp.common.EnsureDirExists(output_filename)
    self.fp = open(output_filename, 'w')
    self.fp.write(header)
    # For consistency with other builders, put sub-project build output in the
    # sub-project dir (see test/subdirectory/gyptest-subdir-all.py).
    self.WriteLn('export builddir_name ?= %s' %
                 os.path.join(os.path.dirname(output_filename), build_dir))
    self.WriteLn('.PHONY: all')
    self.WriteLn('all:')
    if makefile_path:
      makefile_path = ' -C ' + makefile_path
    self.WriteLn('\t$(MAKE)%s %s' % (makefile_path, ' '.join(targets)))
    self.fp.close()

  def WriteActions(self, actions, extra_sources, extra_outputs,
                   extra_mac_bundle_resources, part_of_all):
    """Write Makefile code for any 'actions' from the gyp input.

    extra_sources: a list that will be filled in with newly generated source
                   files, if any
    extra_outputs: a list that will be filled in with any outputs of these
                   actions (used to make other pieces dependent on these
                   actions)
    part_of_all: flag indicating this target is part of 'all'
    """
    env = self.GetSortedXcodeEnv()
    for action in actions:
      name = StringToMakefileVariable('%s_%s' % (self.qualified_target,
                                                 action['action_name']))
      self.WriteLn('### Rules for action "%s":' % action['action_name'])
      inputs = action['inputs']
      outputs = action['outputs']

      # Build up a list of outputs.
      # Collect the output dirs we'll need.
      dirs = set()
      for out in outputs:
        d = os.path.split(out)[0]
        if d:
          dirs.add(d)
      if int(action.get('process_outputs_as_sources', False)):
        extra_sources += outputs
      if int(action.get('process_outputs_as_mac_bundle_resources', False)):
        extra_mac_bundle_resources += outputs

      # Write the actual command.
      action_commands = action['action']
      if self.flavor == 'mac':
        action_commands = [gyp.xcode_emulation.ExpandEnvVars(command, env) for command in action_commands]
      command = gyp.common.EncodePOSIXShellList(action_commands)
      if 'message' in action:
        self.WriteLn('quiet_cmd_%s = ACTION %s $@' % (name, action['message']))
      else:
        self.WriteLn('quiet_cmd_%s = ACTION %s $@' % (name, name))
      if len(dirs) > 0:
        command = 'mkdir -p %s' % ' '.join(dirs) + '; ' + command

      cd_action = 'cd %s; ' % Sourceify(self.path or '.')

      # command and cd_action get written to a toplevel variable called
      # cmd_foo. Toplevel variables can't handle things that change per
      # makefile like $(TARGET), so hardcode the target.
      command = command.replace('$(TARGET)', self.target)
      cd_action = cd_action.replace('$(TARGET)', self.target)

      # Set LD_LIBRARY_PATH in case the action runs an executable from this
      # build which links to shared libs from this build.
      # actions run on the host, so they should in theory only use host
      # libraries, but until everything is made cross-compile safe, also use
      # target libraries.
      # TODO(piman): when everything is cross-compile safe, remove lib.target
      self.WriteLn('cmd_%s = LD_LIBRARY_PATH=$(builddir)/lib.host:'
                   '$(builddir)/lib.target:$$LD_LIBRARY_PATH; '
                   'export LD_LIBRARY_PATH; '
                   '%s%s'
                   % (name, cd_action, command))
      self.WriteLn()
      outputs = [self.Absolutify(o) for o in outputs]
      # The makefile rules are all relative to the top dir, but the gyp actions
      # are defined relative to their containing dir.  This replaces the obj
      # variable for the action rule with an absolute version so that the output
      # goes in the right place.
      # Only write the 'obj' and 'builddir' rules for the "primary" output (:1);
      # it's superfluous for the "extra outputs", and this avoids accidentally
      # writing duplicate dummy rules for those outputs.
      # Same for environment.
      self.WriteLn("%s: obj := $(abs_obj)" % QuoteSpaces(outputs[0]))
      self.WriteLn("%s: builddir := $(abs_builddir)" % QuoteSpaces(outputs[0]))
      self.WriteSortedXcodeEnv(outputs[0], self.GetSortedXcodeEnv())

      for i in inputs:
        assert ' ' not in i, ("Spaces in action input filenames not supported (%s)" % i)
      for output in outputs:
        assert ' ' not in output, ("Spaces in action output filenames not supported (%s)" % output)

      # See the comment in WriteCopies about expanding env vars.
      outputs = [gyp.xcode_emulation.ExpandEnvVars(o, env) for o in outputs]
      inputs = [gyp.xcode_emulation.ExpandEnvVars(i, env) for i in inputs]

      self.WriteDoCmd(outputs, map(Sourceify, map(self.Absolutify, inputs)), part_of_all=part_of_all, command=name)

      # Stuff the outputs in a variable so we can refer to them later.
      outputs_variable = 'action_%s_outputs' % name
      self.WriteLn('%s := %s' % (outputs_variable, ' '.join(outputs)))
      extra_outputs.append('$(%s)' % outputs_variable)
      self.WriteLn()

    self.WriteLn()

  def WriteRules(self, rules, extra_sources, extra_outputs, extra_mac_bundle_resources):
    """Write Makefile code for any 'rules' from the gyp input.

    extra_sources: a list that will be filled in with newly generated source
                   files, if any
    extra_outputs: a list that will be filled in with any outputs of these
                   rules (used to make other pieces dependent on these rules)
    part_of_all: flag indicating this target is part of 'all'
    """
    env = self.GetSortedXcodeEnv()
    for rule in rules:
      name = StringToMakefileVariable('%s_%s' % (self.qualified_target,
                                                 rule['rule_name']))
      count = 0
      self.WriteLn('### Generated for rule %s:' % name)

      all_outputs = []

      for rule_source in rule.get('rule_sources', []):
        dirs = set()
        (rule_source_dirname, rule_source_basename) = os.path.split(rule_source)
        (rule_source_root, rule_source_ext) = os.path.splitext(rule_source_basename)

        outputs = [self.ExpandInputRoot(out, rule_source_root,
                                        rule_source_dirname)
                   for out in rule['outputs']]

        for out in outputs:
          d = os.path.dirname(out)
          if d:
            dirs.add(d)
        if int(rule.get('process_outputs_as_sources', False)):
          extra_sources += outputs
        if int(rule.get('process_outputs_as_mac_bundle_resources', False)):
          extra_mac_bundle_resources += outputs
        inputs = map(Sourceify, map(self.Absolutify, [rule_source] +
                                    rule.get('inputs', [])))
        actions = ['$(call do_cmd,%s_%d)' % (name, count)]

        if name == 'resources_grit':
          # HACK: This is ugly.  Grit intentionally doesn't touch the
          # timestamp of its output file when the file doesn't change,
          # which is fine in hash-based dependency systems like scons
          # and forge, but not kosher in the make world.  After some
          # discussion, hacking around it here seems like the least
          # amount of pain.
          actions += ['@touch --no-create $@']

        # See the comment in WriteCopies about expanding env vars.
        outputs = [gyp.xcode_emulation.ExpandEnvVars(o, env) for o in outputs]
        inputs = [gyp.xcode_emulation.ExpandEnvVars(i, env) for i in inputs]

        outputs = [self.Absolutify(o) for o in outputs]
        all_outputs += outputs
        # Only write the 'obj' and 'builddir' rules for the "primary" output
        # (:1); it's superfluous for the "extra outputs", and this avoids
        # accidentally writing duplicate dummy rules for those outputs.
        self.WriteLn('%s: obj := $(abs_obj)' % outputs[0])
        self.WriteLn('%s: builddir := $(abs_builddir)' % outputs[0])
        self.WriteMakeRule(outputs, inputs, actions,
                           command="%s_%d" % (name, count))
        # Spaces in rule filenames are not supported, but rule variables have
        # spaces in them (e.g. RULE_INPUT_PATH expands to '$(abspath $<)').
        # The spaces within the variables are valid, so remove the variables
        # before checking.
        variables_with_spaces = re.compile(r'\$\([^ ]* \$<\)')
        for output in outputs:
          output = re.sub(variables_with_spaces, '', output)
          assert ' ' not in output, (
              "Spaces in rule filenames not yet supported (%s)" % output)
        self.WriteLn('all_deps += %s' % ' '.join(outputs))

        action = [self.ExpandInputRoot(ac, rule_source_root,
                                       rule_source_dirname)
                  for ac in rule['action']]
        mkdirs = ''
        if len(dirs) > 0:
          mkdirs = 'mkdir -p %s; ' % ' '.join(dirs)
        cd_action = 'cd %s; ' % Sourceify(self.path or '.')

        # action, cd_action, and mkdirs get written to a toplevel variable
        # called cmd_foo. Toplevel variables can't handle things that change
        # per makefile like $(TARGET), so hardcode the target.
        if self.flavor == 'mac':
          action = [gyp.xcode_emulation.ExpandEnvVars(command, env)
                    for command in action]
        action = gyp.common.EncodePOSIXShellList(action)
        action = action.replace('$(TARGET)', self.target)
        cd_action = cd_action.replace('$(TARGET)', self.target)
        mkdirs = mkdirs.replace('$(TARGET)', self.target)

        # Set LD_LIBRARY_PATH in case the rule runs an executable from this
        # build which links to shared libs from this build.
        # rules run on the host, so they should in theory only use host
        # libraries, but until everything is made cross-compile safe, also use
        # target libraries.
        # TODO(piman): when everything is cross-compile safe, remove lib.target
        self.WriteLn(
            "cmd_%(name)s_%(count)d = LD_LIBRARY_PATH="
              "$(builddir)/lib.host:$(builddir)/lib.target:$$LD_LIBRARY_PATH; "
              "export LD_LIBRARY_PATH; "
              "%(cd_action)s%(mkdirs)s%(action)s" % {
          'action': action,
          'cd_action': cd_action,
          'count': count,
          'mkdirs': mkdirs,
          'name': name,
        })
        self.WriteLn(
            'quiet_cmd_%(name)s_%(count)d = RULE %(name)s_%(count)d $@' % {
          'count': count,
          'name': name,
        })
        self.WriteLn()
        count += 1

      outputs_variable = 'rule_%s_outputs' % name
      self.WriteList(all_outputs, outputs_variable)
      extra_outputs.append('$(%s)' % outputs_variable)

      self.WriteLn('### Finished generating for rule: %s' % name)
      self.WriteLn()
    self.WriteLn('### Finished generating for all rules')
    self.WriteLn('')

  def WriteCopies(self, copies, extra_outputs, part_of_all):
    """Write Makefile code for any 'copies' from the gyp input.

    extra_outputs: a list that will be filled in with any outputs of this action
                   (used to make other pieces dependent on this action)
    part_of_all: flag indicating this target is part of 'all'
    """
    self.WriteLn('### Generated for copy rule.')

    variable = StringToMakefileVariable(self.qualified_target + '_copies')
    outputs = []
    for copy in copies:
      for path in copy['files']:
        # Absolutify() may call normpath, and will strip trailing slashes.
        path = Sourceify(self.Absolutify(path))
        filename = os.path.split(path)[1]
        output = Sourceify(self.Absolutify(os.path.join(copy['destination'],
                                                        filename)))

        # If the output path has variables in it, which happens in practice for
        # 'copies', writing the environment as target-local doesn't work,
        # because the variables are already needed for the target name.
        # Copying the environment variables into global make variables doesn't
        # work either, because then the .d files will potentially contain spaces
        # after variable expansion, and .d file handling cannot handle spaces.
        # As a workaround, manually expand variables at gyp time. Since 'copies'
        # can't run scripts, there's no need to write the env then.
        # WriteDoCmd() will escape spaces for .d files.
        env = self.GetSortedXcodeEnv()
        output = gyp.xcode_emulation.ExpandEnvVars(output, env)
        path = gyp.xcode_emulation.ExpandEnvVars(path, env)
        self.WriteDoCmd([output], [path], 'copy', part_of_all)
        outputs.append(output)
    self.WriteLn('%s = %s' % (variable, ' '.join(map(QuoteSpaces, outputs))))
    extra_outputs.append('$(%s)' % variable)
    self.WriteLn()

  def WriteMacBundleResources(self, resources, bundle_deps):
    """Writes Makefile code for 'mac_bundle_resources'."""
    self.WriteLn('### Generated for mac_bundle_resources')

    product_dir = generator_default_variables['PRODUCT_DIR']
    sources = map(Sourceify, map(self.Absolutify, resources))
    bundle_resources = gyp.xcode_emulation.GetMacBundleResources(product_dir, self.xcode_settings, sources)
    for output, res in bundle_resources:
      _, ext = os.path.splitext(output)
      # TODO(refack): actualy figure this out for `copy-bundle-resource`
      # is_binary = xcode_emulation.IsBinaryOutputFormat(output)
      if ext != '.xcassets':
        # Make does not supports '.xcassets' emulation.
        self.WriteDoCmd([output], [res], 'mac_tool,,,copy-bundle-resource', part_of_all=True)
        bundle_deps.append(output)

  def WriteMacInfoPlist(self, bundle_deps):
    """Write Makefile code for bundle Info.plist files."""
    info_plist, out, defines, extra_env = gyp.xcode_emulation.GetMacInfoPlist(
      generator_default_variables['PRODUCT_DIR'], self.xcode_settings,
      lambda p: Sourceify(self.Absolutify(p)))
    if not info_plist:
      return
    if defines:
      # Create an intermediate file to store preprocessed results.
      intermediate_plist = ('$(obj).$(TOOLSET)/$(TARGET)/' + os.path.basename(info_plist))
      self.WriteList(defines, intermediate_plist + ': INFOPLIST_DEFINES', '-D', quoter=EscapeCppDefine)
      self.WriteMakeRule([intermediate_plist], [info_plist],
                         ['$(call do_cmd,infoplist)',
                          # "Convert" the plist so that any weird whitespace changes from the
                          # preprocessor do not affect the XML parser in mac_tool.
                          '@plutil -convert xml1 $@ $@'])
      info_plist = intermediate_plist
    # plists can contain envvars and substitute them into the file.
    self.WriteSortedXcodeEnv(out, self.GetSortedXcodeEnv(additional_settings=extra_env))
    self.WriteDoCmd([out], [info_plist], 'mac_tool,,,copy-info-plist', part_of_all=True)
    bundle_deps.append(out)

  def WriteSources(self, configs, deps, sources, extra_outputs, extra_link_deps, precompiled_header):
    """Write Makefile code for any 'sources' from the gyp input.
    These are source files necessary to build the current target.

    configs, deps, sources: input from gyp.
    extra_outputs: a list of extra outputs this action should be dependent on;
                   used to serialize action/rules before compilation
    extra_link_deps: a list that will be filled in with any outputs of
                     compilation (to be used in link lines)
    part_of_all: flag indicating this target is part of 'all'
    """

    # Write configuration-specific variables for CFLAGS, etc.
    for configname in sorted(configs.keys()):
      config = configs[configname]
      self.WriteList(config.get('defines'), 'DEFS_%s' % configname, prefix='-D', quoter=EscapeCppDefine)

      if self.flavor == 'mac':
        cflags = self.xcode_settings.GetCflags(configname)
        cflags_c = self.xcode_settings.GetCflagsC(configname)
        cflags_cc = self.xcode_settings.GetCflagsCC(configname)
        cflags_objc = self.xcode_settings.GetCflagsObjC(configname)
        cflags_objcc = self.xcode_settings.GetCflagsObjCC(configname)
      else:
        cflags = config.get('cflags')
        cflags_c = config.get('cflags_c')
        cflags_cc = config.get('cflags_cc')
        cflags_objc = None
        cflags_objcc = None

      self.WriteLn("# Flags passed to all source files.")
      self.WriteList(cflags, 'CFLAGS_%s' % configname)
      self.WriteLn("# Flags passed to only C files.")
      self.WriteList(cflags_c, 'CFLAGS_C_%s' % configname)
      self.WriteLn("# Flags passed to only C++ files.")
      self.WriteList(cflags_cc, 'CFLAGS_CC_%s' % configname)
      if self.flavor == 'mac':
        self.WriteLn("# Flags passed to only ObjC files.")
        self.WriteList(cflags_objc, 'CFLAGS_OBJC_%s' % configname)
        self.WriteLn("# Flags passed to only ObjC++ files.")
        self.WriteList(cflags_objcc, 'CFLAGS_OBJCC_%s' % configname)
      includes = config.get('include_dirs')
      if includes:
        includes = [Sourceify(self.Absolutify(include)) for include in includes]
      self.WriteList(includes, 'INCS_%s' % configname, prefix='-I')

    compilable = filter(Compilable, sources)
    objs = [self.Objectify(self.Absolutify(Target(x))) for x in compilable]
    self.WriteList(objs, 'OBJS')

    for obj in objs:
      assert ' ' not in obj, (
          "Spaces in object filenames not supported (%s)" % obj)
    self.WriteLn('# Add to the list of files we specially track '
                 'dependencies for.')
    self.WriteLn('all_deps += $(OBJS)')
    self.WriteLn()

    # Make sure our dependencies are built first.
    if deps:
      self.WriteMakeRule(['$(OBJS)'], deps,
                         comment='Make sure our dependencies are built before any of us.',
                         order_only=True)

    # Make sure the actions and rules run first.
    # If they generate any extra headers etc., the per-.o file dep tracking
    # will catch the proper rebuilds, so order only is still ok here.
    if extra_outputs:
      self.WriteMakeRule(['$(OBJS)'], extra_outputs,
                         comment='Make sure our actions/rules run before any of us.',
                         order_only=True)

    pchdeps = precompiled_header.GetObjDependencies(compilable, objs)
    if pchdeps:
      self.WriteLn('# Dependencies from obj files to their precompiled headers')
      for source, obj, gch in pchdeps:
        self.WriteLn('%s: %s' % (obj, gch))
      self.WriteLn('# End precompiled header dependencies')

    if objs:
      extra_link_deps.append('$(OBJS)')
      self.WriteLn("""\
# CFLAGS et al overrides must be target-local.
# See "Target-specific Variable Values" in the GNU Make manual.""")
      self.WriteLn("$(OBJS): TOOLSET := $(TOOLSET)")
      self.WriteLn("$(OBJS): GYP_CFLAGS := "
                   "$(DEFS_$(BUILDTYPE)) "
                   "$(INCS_$(BUILDTYPE)) "
                   "%s " % precompiled_header.GetInclude('c') +
                   "$(CFLAGS_$(BUILDTYPE)) "
                   "$(CFLAGS_C_$(BUILDTYPE))")
      self.WriteLn("$(OBJS): GYP_CXXFLAGS := "
                   "$(DEFS_$(BUILDTYPE)) "
                   "$(INCS_$(BUILDTYPE)) "
                   "%s " % precompiled_header.GetInclude('cc') +
                   "$(CFLAGS_$(BUILDTYPE)) "
                   "$(CFLAGS_CC_$(BUILDTYPE))")
      if self.flavor == 'mac':
        self.WriteLn("$(OBJS): GYP_OBJCFLAGS := "
                     "$(DEFS_$(BUILDTYPE)) "
                     "$(INCS_$(BUILDTYPE)) "
                     "%s " % precompiled_header.GetInclude('m') +
                     "$(CFLAGS_$(BUILDTYPE)) "
                     "$(CFLAGS_C_$(BUILDTYPE)) "
                     "$(CFLAGS_OBJC_$(BUILDTYPE))")
        self.WriteLn("$(OBJS): GYP_OBJCXXFLAGS := "
                     "$(DEFS_$(BUILDTYPE)) "
                     "$(INCS_$(BUILDTYPE)) "
                     "%s " % precompiled_header.GetInclude('mm') +
                     "$(CFLAGS_$(BUILDTYPE)) "
                     "$(CFLAGS_CC_$(BUILDTYPE)) "
                     "$(CFLAGS_OBJCC_$(BUILDTYPE))")

    self.WritePchTargets(precompiled_header.GetPchBuildCommands())

    # If there are any object files in our input file list, link them into our
    # output.
    extra_link_deps += [source for source in sources if Linkable(source)]

    self.WriteLn()

  def WritePchTargets(self, pch_commands):
    """Writes make rules to compile prefix headers."""
    if not pch_commands:
      return

    for gch, lang_flag, lang, inpt in pch_commands:
      extra_flags = {
        'c': '$(CFLAGS_C_$(BUILDTYPE))',
        'cc': '$(CFLAGS_CC_$(BUILDTYPE))',
        'm': '$(CFLAGS_C_$(BUILDTYPE)) $(CFLAGS_OBJC_$(BUILDTYPE))',
        'mm': '$(CFLAGS_CC_$(BUILDTYPE)) $(CFLAGS_OBJCC_$(BUILDTYPE))',
      }[lang]
      var_name = {
        'c': 'GYP_PCH_CFLAGS',
        'cc': 'GYP_PCH_CXXFLAGS',
        'm': 'GYP_PCH_OBJCFLAGS',
        'mm': 'GYP_PCH_OBJCXXFLAGS',
      }[lang]
      self.WriteLn("%s: %s := %s " % (gch, var_name, lang_flag) +
                   "$(DEFS_$(BUILDTYPE)) "
                   "$(INCS_$(BUILDTYPE)) "
                   "$(CFLAGS_$(BUILDTYPE)) " +
                   extra_flags)

      self.WriteLn('%s: %s FORCE_DO_CMD' % (gch, inpt))
      self.WriteLn('\t@$(call do_cmd,pch_%s,1)' % lang)
      self.WriteLn('')
      assert ' ' not in gch, (
          "Spaces in gch filenames not supported (%s)" % gch)
      self.WriteLn('all_deps += %s' % gch)
      self.WriteLn('')

  def ComputeOutputBasename(self, spec):
    """Return the 'output basename' of a gyp spec.

    E.g., the loadable module 'foobar' in directory 'baz' will produce
      'libfoobar.so'
    """
    assert not self.is_mac_bundle

    if self.flavor == 'mac' and self.type in (
        'static_library', 'executable', 'shared_library', 'loadable_module'):
      return self.xcode_settings.GetExecutablePath()

    target = spec['target_name']
    target_prefix = ''
    target_ext = ''
    if self.type == 'static_library':
      if target[:3] == 'lib':
        target = target[3:]
      target_prefix = 'lib'
      target_ext = '.a'
    elif self.type in ('loadable_module', 'shared_library'):
      if target[:3] == 'lib':
        target = target[3:]
      target_prefix = 'lib'
      if self.flavor == 'aix':
        target_ext = '.a'
      else:
        target_ext = '.so'
    elif self.type == 'none':
      target = '%s.stamp' % target
    elif self.type != 'executable':
      print(("ERROR: What output file should be generated?",
             "type", self.type, "target", target))

    target_prefix = spec.get('product_prefix', target_prefix)
    target = spec.get('product_name', target)
    product_ext = spec.get('product_extension')
    if product_ext:
      target_ext = '.' + product_ext

    return target_prefix + target + target_ext

  def _InstallImmediately(self):
    return self.toolset == 'target' and self.flavor == 'mac' and self.type in ('static_library', 'executable', 'shared_library', 'loadable_module')

  def ComputeOutput(self, spec):
    """Return the 'output' (full output path) of a gyp spec.

    E.g., the loadable module 'foobar' in directory 'baz' will produce
      '$(obj)/baz/libfoobar.so'
    """
    assert not self.is_mac_bundle

    path = os.path.join('$(obj).' + self.toolset, self.path)
    if self.type == 'executable' or self._InstallImmediately():
      path = '$(builddir)'
    path = spec.get('product_dir', path)
    return os.path.join(path, self.ComputeOutputBasename(spec))

  def ComputeMacBundleOutput(self):
    """Return the 'output' (full output path) to a bundle output directory."""
    assert self.is_mac_bundle
    path = generator_default_variables['PRODUCT_DIR']
    return os.path.join(path, self.xcode_settings.GetWrapperName())

  def ComputeMacBundleBinaryOutput(self):
    """Return the 'output' (full output path) to the binary in a bundle."""
    path = generator_default_variables['PRODUCT_DIR']
    return os.path.join(path, self.xcode_settings.GetExecutablePath())

  @staticmethod
  def ComputeDeps(spec):
    """Compute the dependencies of a gyp spec.

    Returns a tuple (deps, link_deps), where each is a list of
    filenames that will need to be put in front of make for either
    building (deps) or linking (link_deps).
    """
    deps = []
    link_deps = []
    if 'dependencies' in spec:
      deps.extend([target_outputs[dep] for dep in spec['dependencies']
                   if target_outputs[dep]])
      for dep in spec['dependencies']:
        if dep in target_link_deps:
          link_deps.append(target_link_deps[dep])
      deps.extend(link_deps)
      # TODO: It seems we need to transitively link in libraries (e.g. -lfoo)?
      # This hack makes it work:
      # link_deps.extend(spec.get('libraries', []))
    return gyp.common.uniquer(deps), gyp.common.uniquer(link_deps)

  def WriteDependencyOnExtraOutputs(self, extra_outputs):
    self.WriteMakeRule([self.output_binary], extra_outputs, comment='Build our special outputs first.', order_only=True)

  def WriteTarget(self, spec, configs, deps, link_deps, bundle_deps, extra_outputs, part_of_all):
    """
    Write Makefile code to produce the final target of the gyp spec.

    spec: input from gyp.
    configs: input from gyp.
    deps: dependency lists; see ComputeDeps()
    link_deps: dependency lists; see ComputeDeps()
    extra_outputs: any extra outputs that our target should depend on
    part_of_all: flag indicating this target is part of 'all'
    """

    self.WriteLn('### Rules for final target.')

    if extra_outputs:
      self.WriteDependencyOnExtraOutputs(extra_outputs)
      self.WriteMakeRule(extra_outputs, deps, comment='Preserve order dependency of special output on deps.', order_only=True)

    target_postbuilds = {}
    if self.type != 'none':
      for configname in sorted(configs.keys()):
        config = configs[configname]
        if self.flavor == 'mac':
          ldflags = self.xcode_settings.GetLdflags(configname,
                                                   generator_default_variables['PRODUCT_DIR'],
                                                   lambda p: Sourceify(self.Absolutify(p)))

          # TARGET_POSTBUILDS_$(BUILDTYPE) is added to postbuilds later on.
          gyp_to_build = gyp.common.InvertRelativePath(self.path)
          target_postbuild = self.xcode_settings.AddImplicitPostbuilds(
            configname,
            QuoteSpaces(os.path.normpath(os.path.join(gyp_to_build, self.output))),
            QuoteSpaces(os.path.normpath(os.path.join(gyp_to_build, self.output_binary))))
          if target_postbuild:
            target_postbuilds[configname] = target_postbuild
        else:
          ldflags = config.get('ldflags', [])
          # Compute an rpath for this output if needed.
          if any(dep.endswith('.so') or '.so.' in dep for dep in deps):
            # We want to get the literal string "$ORIGIN" into the link command,
            # so we need lots of escaping.
            ldflags.append(r'-Wl,-rpath=\$$ORIGIN/lib.%s/' % self.toolset)
            ldflags.append(r'-Wl,-rpath-link=\$(builddir)/lib.%s/' %
                           self.toolset)
        library_dirs = config.get('library_dirs', [])
        ldflags += [('-L%s' % library_dir) for library_dir in library_dirs]
        self.WriteList(ldflags, 'LDFLAGS_%s' % configname)
        if self.flavor == 'mac':
          self.WriteList(self.xcode_settings.GetLibtoolflags(configname),
                         'LIBTOOLFLAGS_%s' % configname)
      libraries = spec.get('libraries')
      if libraries:
        # Remove duplicate entries
        libraries = gyp.common.uniquer(libraries)
        if self.flavor == 'mac':
          libraries = self.xcode_settings.AdjustLibraries(libraries)
      self.WriteList(libraries, 'LIBS')
      self.WriteLn('%s: GYP_LDFLAGS := $(LDFLAGS_$(BUILDTYPE))' % QuoteSpaces(self.output_binary))
      self.WriteLn('%s: LIBS := $(LIBS)' % QuoteSpaces(self.output_binary))

      if self.flavor == 'mac':
        self.WriteLn('%s: GYP_LIBTOOLFLAGS := $(LIBTOOLFLAGS_$(BUILDTYPE))' % QuoteSpaces(self.output_binary))

    # Postbuild actions. Like actions, but implicitly depend on the target's
    # output.
    postbuilds = []
    if self.flavor == 'mac':
      if target_postbuilds:
        postbuilds.append('$(TARGET_POSTBUILDS_$(BUILDTYPE))')
      postbuilds.extend(gyp.xcode_emulation.GetSpecPostbuildCommands(spec))

    if postbuilds:
      # Envvars may be referenced by TARGET_POSTBUILDS_$(BUILDTYPE),
      # so we must output its definition first, since we declare variables
      # using ":=".
      self.WriteSortedXcodeEnv(self.output, self.GetSortedXcodePostbuildEnv())

      for configname in target_postbuilds:
        self.WriteLn('%s: TARGET_POSTBUILDS_%s := %s' % (QuoteSpaces(self.output), configname, gyp.common.EncodePOSIXShellList(target_postbuilds[configname])))

      # Postbuilds expect to be run in the gyp file's directory, so insert an
      # implicit postbuild to cd to there.
      postbuilds.insert(0, gyp.common.EncodePOSIXShellList(['cd', self.path]))
      for i, postbuild in enumerate(postbuilds):
        if not postbuild.startswith('$'):
          postbuilds[i] = EscapeShellArgument(postbuild)
      self.WriteLn('%s: builddir := $(abs_builddir)' % QuoteSpaces(self.output))
      self.WriteLn('%s: POSTBUILDS := %s' % (
        QuoteSpaces(self.output), ' '.join(postbuilds)))

    # A bundle directory depends on its dependencies such as bundle resources
    # and bundle binary. When all dependencies have been built, the bundle
    # needs to be packaged.
    if self.is_mac_bundle:
      # If the framework doesn't contain a binary, then nothing depends
      # on the actions -- make the framework depend on them directly too.
      self.WriteDependencyOnExtraOutputs(extra_outputs)

      # Bundle dependencies. Note that the code below adds actions to this
      # target, so if you move these two lines, move the lines below as well.
      self.WriteList(map(QuoteSpaces, bundle_deps), 'BUNDLE_DEPS')
      self.WriteLn('%s: $(BUNDLE_DEPS)' % QuoteSpaces(self.output))

      # After the framework is built, package it. Needs to happen before
      # postbuilds, since postbuilds depend on this.
      if self.type in ('shared_library', 'loadable_module'):
        self.WriteLn('\t@$(call do_cmd,mac_package_framework,,,%s)' % self.xcode_settings.GetFrameworkVersion())

      # Bundle postbuilds can depend on the whole bundle, so run them after
      # the bundle is packaged, not already after the bundle binary is done.
      if postbuilds:
        self.WriteLn('\t@$(call do_postbuilds)')
      postbuilds = []  # Don't write postbuilds for target's output.

      # Needed by test/mac/gyptest-rebuild.py.
      self.WriteLn('\t@true  # No-op, used by tests')

      # Since this target depends on binary and resources which are in
      # nested subfolders, the framework directory will be older than
      # its dependencies usually. To prevent this rule from executing
      # on every build (expensive, especially with postbuilds), expliclity
      # update the time on the framework directory.
      self.WriteLn('\t@touch -c %s' % QuoteSpaces(self.output))

    if postbuilds:
      assert not self.is_mac_bundle, ('Postbuilds for bundles should be done on the bundle, not the binary (target \'%s\')' % self.target)
      assert 'product_dir' not in spec, 'Postbuilds do not work with custom product_dir'

    if self.type == 'executable':
      self.WriteLn('%s: LD_INPUTS := %s' % (QuoteSpaces(self.output_binary), ' '.join(map(QuoteSpaces, link_deps))))
      if self.toolset == 'host' and self.flavor == 'android':
        self.WriteDoCmd([self.output_binary], link_deps, 'link_host', part_of_all, postbuilds=postbuilds)
      else:
        self.WriteDoCmd([self.output_binary], link_deps, 'link', part_of_all, postbuilds=postbuilds)

    elif self.type == 'static_library':
      for link_dep in link_deps:
        assert ' ' not in link_dep, ("Spaces in alink input filenames not supported (%s)" % link_dep)
      if (self.flavor not in ('mac', 'openbsd', 'netbsd', 'win') and not
      self.is_standalone_static_library):
        self.WriteDoCmd([self.output_binary], link_deps, 'alink_thin', part_of_all, postbuilds=postbuilds)
      else:
        self.WriteDoCmd([self.output_binary], link_deps, 'alink', part_of_all, postbuilds=postbuilds)
    elif self.type == 'shared_library':
      self.WriteLn('%s: LD_INPUTS := %s' % (QuoteSpaces(self.output_binary), ' '.join(map(QuoteSpaces, link_deps))))
      self.WriteDoCmd([self.output_binary], link_deps, 'solink', part_of_all, postbuilds=postbuilds)
    elif self.type == 'loadable_module':
      for link_dep in link_deps:
        assert ' ' not in link_dep, ("Spaces in module input filenames not supported (%s)" % link_dep)
      if self.toolset == 'host' and self.flavor == 'android':
        self.WriteDoCmd([self.output_binary], link_deps, 'solink_module_host', part_of_all, postbuilds=postbuilds)
      else:
        self.WriteDoCmd([self.output_binary], link_deps, 'solink_module', part_of_all, postbuilds=postbuilds)
    elif self.type == 'none':
      # Write a stamp line.
      self.WriteDoCmd([self.output_binary], deps, 'touch', part_of_all, postbuilds=postbuilds)
    else:
      print("WARNING: no output for", self.type, self.target)

    # Add an alias for each target (if there are any outputs).
    # Installable target aliases are created below.
    if ((self.output and self.output != self.target) and
        (self.type not in self._INSTALLABLE_TARGETS)):
      self.WriteMakeRule([self.target], [self.output], comment='Add target alias', phony=True)
      if part_of_all:
        self.WriteMakeRule(['all'], [self.target], comment='Add target alias to "all" target.', phony=True)

    # Add special-case rules for our installable targets.
    # 1) They need to install to the build dir or "product" dir.
    # 2) They get shortcuts for building (e.g. "make chrome").
    # 3) They are part of "make all".
    if (self.type in self._INSTALLABLE_TARGETS or
        self.is_standalone_static_library):
      if self.type == 'shared_library':
        file_desc = 'shared library'
      elif self.type == 'static_library':
        file_desc = 'static library'
      else:
        file_desc = 'executable'
      install_path = self._InstallableTargetInstallPath()
      installable_deps = [self.output]
      if (self.flavor == 'mac' and not 'product_dir' in spec and
          self.toolset == 'target'):
        # On mac, products are created in install_path immediately.
        assert install_path == self.output, '%s != %s' % (install_path, self.output)

      # Point the target alias to the final binary output.
      self.WriteMakeRule([self.target], [install_path],
                         comment='Add target alias', phony=True)
      if install_path != self.output:
        assert not self.is_mac_bundle  # See comment a few lines above.
        self.WriteDoCmd([install_path], [self.output], 'copy', comment='Copy this to the %s output path.' % file_desc, part_of_all=part_of_all)
        installable_deps.append(install_path)
      if self.output != self.alias and self.alias != self.target:
        self.WriteMakeRule([self.alias], installable_deps, comment='Short alias for building this %s.' % file_desc, phony=True)
      if part_of_all:
        self.WriteMakeRule(['all'], [install_path], comment='Add %s to "all" target.' % file_desc, phony=True)

  def WriteList(self, value_list, variable=None, prefix='', quoter=QuoteIfNecessary):
    """
    Write a variable definition that is a list of values.

    E.g. WriteList(['a','b'], 'foo', prefix='blah') writes out
         foo = blaha blahb
    but in a pretty-printed style.
    """
    values = ''
    if value_list:
      value_list = [quoter(prefix + l) for l in value_list]
      values = ' \\\n\t' + ' \\\n\t'.join(value_list)
    self.fp.write('%s :=%s\n\n' % (variable, values))

  # TODO(refack) `part_of_all` is not used, but is part of signature used in many other places
  # noinspection PyUnusedLocal
  def WriteDoCmd(self, outputs, inputs, command, part_of_all=False, comment=None, postbuilds=None):
    """
    Write a Makefile rule that uses do_cmd.

    This makes the outputs dependent on the command line that was run,
    as well as support the V= make command line flag.
    """
    suffix = ''
    if postbuilds:
      assert ',' not in command
      suffix = ',,1'  # Tell do_cmd to honor $POSTBUILDS
    self.WriteMakeRule(
      outputs,
      inputs,
      actions=['$(call do_cmd,%s%s)' % (command, suffix)],
      comment=comment,
      command=command,
      force=True
    )
    # Add our outputs to the list of targets we read depfiles from.
    # all_deps is only used for deps file reading, and for deps files we replace
    # spaces with ? because escaping doesn't work with make's $(sort) and
    # other functions.
    outputs = [QuoteSpaces(o, SPACE_REPLACEMENT) for o in outputs]
    self.WriteLn('all_deps += %s' % ' '.join(outputs))

  def WriteMakeRule(self, outputs, inputs, actions=None, comment=None, order_only=False, force=False, phony=False, command=None):
    """
    Write a Makefile rule, with some extra tricks.

    outputs: a list of outputs for the rule (note: this is not directly
             supported by make; see comments below)
    inputs: a list of inputs for the rule
    actions: a list of shell commands to run for the rule
    comment: a comment to put in the Makefile above the rule (also useful
             for making this Python script's code self-documenting)
    order_only: if true, makes the dependency order-only
    force: if true, include FORCE_DO_CMD as an order-only dep
    phony: if true, the rule does not actually generate the named output, the
           output is just a name to run the rule
    command: (optional) command name to generate unambiguous labels
    """
    outputs = [QuoteSpaces(o) for o in outputs]
    inputs = map(QuoteSpaces, inputs)

    if comment:
      self.WriteLn('# ' + comment)
    if phony:
      self.WriteLn('.PHONY: ' + ' '.join(outputs))
    if actions:
      self.WriteLn("%s: TOOLSET := $(TOOLSET)" % outputs[0])
    force_append = ' FORCE_DO_CMD' if force else ''

    if order_only:
      # Order only rule: Just write a simple rule.
      # TODO(evanm): just make order_only a list of deps instead of this hack.
      self.WriteLn('%s: | %s%s' % (' '.join(outputs), ' '.join(inputs), force_append))
    elif len(outputs) == 1:
      # Regular rule, one output: Just write a simple rule.
      self.WriteLn('%s: %s%s' % (outputs[0], ' '.join(inputs), force_append))
    else:
      # Regular rule, more than one output: Multiple outputs are tricky in make. We will write three rules:
      # - All outputs depend on an intermediate file.
      # - Make .INTERMEDIATE depend on the intermediate.
      # - The intermediate file depends on the inputs and executes the actual command.
      # - The intermediate recipe will 'touch' the intermediate file.
      # - The multi-output rule will have a do-nothing recipe.

      # Hash the target name to avoid generating overlong filenames.
      key = (command if command else self.target).encode('utf-8')
      slug = re.sub(r'\w', key, '')
      cmddigest = hashlib.sha1(key).hexdigest()
      intermediate = "%s.%s.intermediate" % (cmddigest, slug)
      self.WriteLn('%s: %s' % (' '.join(outputs), intermediate))
      self.WriteLn('\t%s' % '@:')
      self.WriteLn('%s: %s' % ('.INTERMEDIATE', intermediate))
      self.WriteLn('%s: %s%s' % (intermediate, ' '.join(inputs), force_append))
      actions.insert(0, '$(call do_cmd,touch)')

    if actions:
      for action in actions:
        self.WriteLn('\t%s' % action)
    self.WriteLn()

  def WriteAndroidNdkModuleRule(self, module_name, all_sources, link_deps):
    """Write a set of LOCAL_XXX definitions for Android NDK.

    These variable definitions will be used by Android NDK but do nothing for
    non-Android applications.

    Arguments:
      module_name: Android NDK module name, which must be unique among all
          module names.
      all_sources: A list of source files (will be filtered by Compilable).
      link_deps: A list of link dependencies, which must be sorted in
          the order from dependencies to dependents.
    """
    if self.type not in ('executable', 'shared_library', 'static_library'):
      return

    self.WriteLn('# Variable definitions for Android applications')
    self.WriteLn('include $(CLEAR_VARS)')
    self.WriteLn('LOCAL_MODULE := ' + module_name)
    self.WriteLn('LOCAL_CFLAGS := $(CFLAGS_$(BUILDTYPE)) '
                 '$(DEFS_$(BUILDTYPE)) '
                 # LOCAL_CFLAGS is applied to both of C and C++.  There is
                 # no way to specify $(CFLAGS_C_$(BUILDTYPE)) only for C
                 # sources.
                 '$(CFLAGS_C_$(BUILDTYPE)) '
                 # $(INCS_$(BUILDTYPE)) includes the prefix '-I' while
                 # LOCAL_C_INCLUDES does not expect it.  So put it in
                 # LOCAL_CFLAGS.
                 '$(INCS_$(BUILDTYPE))')
    # LOCAL_CXXFLAGS is obsolete and LOCAL_CPPFLAGS is preferred.
    self.WriteLn('LOCAL_CPPFLAGS := $(CFLAGS_CC_$(BUILDTYPE))')
    self.WriteLn('LOCAL_C_INCLUDES :=')
    self.WriteLn('LOCAL_LDLIBS := $(LDFLAGS_$(BUILDTYPE)) $(LIBS)')

    # Detect the C++ extension.
    cpp_ext = {'.cc': 0, '.cpp': 0, '.cxx': 0}
    default_cpp_ext = '.cpp'
    for filename in all_sources:
      ext = os.path.splitext(filename)[1]
      if ext in cpp_ext:
        cpp_ext[ext] += 1
        if cpp_ext[ext] > cpp_ext[default_cpp_ext]:
          default_cpp_ext = ext
    self.WriteLn('LOCAL_CPP_EXTENSION := ' + default_cpp_ext)

    self.WriteList(map(self.Absolutify, filter(Compilable, all_sources)),
                   'LOCAL_SRC_FILES')

    # Filter out those which do not match prefix and suffix and produce
    # the resulting list without prefix and suffix.
    def DepsToModules(deps, prefix, suffix):
      modules = []
      for filepath in deps:
        mod_filename = os.path.basename(filepath)
        if mod_filename.startswith(prefix) and mod_filename.endswith(suffix):
          modules.append(mod_filename[len(prefix):-len(suffix)])
      return modules

    # Retrieve the default value of 'SHARED_LIB_SUFFIX'
    params = {'flavor': 'linux'}
    default_variables = {}
    CalculateVariables(default_variables, params)

    self.WriteList(
      DepsToModules(link_deps, generator_default_variables['SHARED_LIB_PREFIX'], default_variables['SHARED_LIB_SUFFIX']),
      'LOCAL_SHARED_LIBRARIES')
    self.WriteList(
      DepsToModules(link_deps, generator_default_variables['STATIC_LIB_PREFIX'], generator_default_variables['STATIC_LIB_SUFFIX']),
      'LOCAL_STATIC_LIBRARIES')

    if self.type == 'executable':
      self.WriteLn('include $(BUILD_EXECUTABLE)')
    elif self.type == 'shared_library':
      self.WriteLn('include $(BUILD_SHARED_LIBRARY)')
    elif self.type == 'static_library':
      self.WriteLn('include $(BUILD_STATIC_LIBRARY)')
    self.WriteLn()

  def WriteLn(self, text=''):
    self.fp.write(text + '\n')

  def GetSortedXcodeEnv(self, additional_settings=None):
    return gyp.xcode_emulation.GetSortedXcodeEnv(self.xcode_settings, "$(abs_builddir)", os.path.join("$(abs_srcdir)", self.path), "$(BUILDTYPE)", additional_settings)

  def GetSortedXcodePostbuildEnv(self):
    # CHROMIUM_STRIP_SAVE_FILE is a chromium-specific hack.
    # TODO(thakis): It would be nice to have some general mechanism instead.
    strip_save_file = self.xcode_settings.GetPerTargetSetting('CHROMIUM_STRIP_SAVE_FILE', '')
    # Even if strip_save_file is empty, explicitly write it. Else a postbuild
    # might pick up an export from an earlier target.
    return self.GetSortedXcodeEnv(additional_settings={'CHROMIUM_STRIP_SAVE_FILE': strip_save_file})

  def WriteSortedXcodeEnv(self, target, env):
    for k, v in env:
      # For
      #  foo := a\ b
      # the escaped space does the right thing. For
      #  export foo := a\ b
      # it does not -- the backslash is written to the env as literal character.
      # So don't escape spaces in |env[k]|.
      self.WriteLn('%s: export %s := %s' % (QuoteSpaces(target), k, v))

  def Objectify(self, path):
    """Convert a path to its output directory form."""
    if '$(' in path:
      path = path.replace('$(obj)/', '$(obj).%s/$(TARGET)/' % self.toolset)
    if not '$(obj)' in path:
      path = '$(obj).%s/$(TARGET)/%s' % (self.toolset, path)
    return path

  def Pchify(self, path, lang):
    """Convert a prefix header path to its output directory form."""
    path = self.Absolutify(path)
    if '$(' in path:
      path = path.replace('$(obj)/', '$(obj).%s/$(TARGET)/pch-%s' %
                          (self.toolset, lang))
      return path
    return '$(obj).%s/$(TARGET)/pch-%s/%s' % (self.toolset, lang, path)

  def Absolutify(self, path):
    """Convert a subdirectory-relative path into a base-relative path.
    Skips over paths that contain variables."""
    if '$(' in path:
      # Don't call normpath in this case, as it might collapse the
      # path too aggressively if it features '..'. However it's still
      # important to strip trailing slashes.
      return path.rstrip('/')
    return os.path.normpath(os.path.join(self.path, path))

  @staticmethod
  def ExpandInputRoot(template, expansion, dirname):
    if '%(INPUT_ROOT)s' not in template and '%(INPUT_DIRNAME)s' not in template:
      return template
    path = template % {
      'INPUT_ROOT': expansion,
      'INPUT_DIRNAME': dirname,
    }
    return path

  def _InstallableTargetInstallPath(self):
    """Returns the location of the final output for an installable target."""
    # Xcode puts shared_library results into PRODUCT_DIR, and some gyp files
    # rely on this. Emulate this behavior for mac.
    if (self.type == 'shared_library' and
        (self.flavor != 'mac' or self.toolset != 'target')):
      # Install all shared libs into a common directory (per toolset) for
      # convenient access with LD_LIBRARY_PATH.
      return '$(builddir)/lib.%s/%s' % (self.toolset, self.alias)
    return '$(builddir)/' + self.alias