# Copyright (c) 2013 Google Inc. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# Notes:
#
# This is all roughly based on the Makefile system used by the Linux
# kernel, but is a non-recursive make -- we put the entire dependency
# graph in front of make and let it figure it out.
#
# The code below generates a separate .mk file for each target, but
# all are sourced by the top-level Makefile.  This means that all
# variables in .mk-files clobber one another.  Be careful to use :=
# where appropriate for immediate evaluation, and similarly to watch
# that you're not relying on a variable value to last beween different
# .mk files.
#
# TODOs:
#
# Global settings and utility functions are currently stuffed in the
# toplevel Makefile.  It may make sense to generate some .mk files on
# the side to keep the the files readable.

import os
import re
import sys
import subprocess
import gyp
import gyp.common
import gyp.xcode_emulation
from gyp.common import GetEnvironFallback

generator_default_variables = {
  'EXECUTABLE_PREFIX': '',
  'EXECUTABLE_SUFFIX': '',
  'STATIC_LIB_PREFIX': 'lib',
  'SHARED_LIB_PREFIX': 'lib',
  'STATIC_LIB_SUFFIX': '.a',
  'INTERMEDIATE_DIR': '$(obj).$(TOOLSET)/$(TARGET)/geni',
  'SHARED_INTERMEDIATE_DIR': '$(obj)/gen',
  'PRODUCT_DIR': '$(builddir)',
  'RULE_INPUT_ROOT': '%(INPUT_ROOT)s',  # This gets expanded by Python.
  'RULE_INPUT_DIRNAME': '%(INPUT_DIRNAME)s',  # This gets expanded by Python.
  'RULE_INPUT_PATH': '$(abspath $<)',
  'RULE_INPUT_EXT': '$(suffix $<)',
  'RULE_INPUT_NAME': '$(notdir $<)',
  'CONFIGURATION_NAME': '$(BUILDTYPE)',
}

# Make supports multiple toolsets
generator_supports_multiple_toolsets = True

# Request sorted dependencies in the order from dependents to dependencies.
generator_wants_sorted_dependencies = False

# Placates pylint.
generator_additional_non_configuration_keys = []
generator_additional_path_sections = []
generator_extra_sources_for_rules = []


def CalculateVariables(default_variables, params):
  """Calculate additional variables for use in the build (called by gyp)."""
  flavor = gyp.common.GetFlavor(params)
  if flavor == 'mac':
    default_variables.setdefault('OS', 'mac')
    default_variables.setdefault('SHARED_LIB_SUFFIX', '.dylib')
    default_variables.setdefault('SHARED_LIB_DIR',
                                 generator_default_variables['PRODUCT_DIR'])
    default_variables.setdefault('LIB_DIR',
                                 generator_default_variables['PRODUCT_DIR'])

    # Copy additional generator configuration data from Xcode, which is shared
    # by the Mac Make generator.
    import gyp.generator.xcode as xcode_generator
    global generator_additional_non_configuration_keys
    generator_additional_non_configuration_keys = getattr(xcode_generator,
        'generator_additional_non_configuration_keys', [])
    global generator_additional_path_sections
    generator_additional_path_sections = getattr(xcode_generator,
        'generator_additional_path_sections', [])
    global generator_extra_sources_for_rules
    generator_extra_sources_for_rules = getattr(xcode_generator,
        'generator_extra_sources_for_rules', [])
    COMPILABLE_EXTENSIONS.update({'.m': 'objc', '.mm' : 'objcxx'})
  else:
    operating_system = flavor
    if flavor == 'android':
      operating_system = 'linux'  # Keep this legacy behavior for now.
    default_variables.setdefault('OS', operating_system)
    default_variables.setdefault('SHARED_LIB_SUFFIX', '.so')
    default_variables.setdefault('SHARED_LIB_DIR','$(builddir)/lib.$(TOOLSET)')
    default_variables.setdefault('LIB_DIR', '$(obj).$(TOOLSET)')


def CalculateGeneratorInputInfo(params):
  """Calculate the generator specific info that gets fed to input (called by
  gyp)."""
  generator_flags = params.get('generator_flags', {})
  android_ndk_version = generator_flags.get('android_ndk_version', None)
  # Android NDK requires a strict link order.
  if android_ndk_version:
    global generator_wants_sorted_dependencies
    generator_wants_sorted_dependencies = True


def ensure_directory_exists(path):
  dir = os.path.dirname(path)
  if dir and not os.path.exists(dir):
    os.makedirs(dir)


# 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 = '?'


LINK_COMMANDS_LINUX = """\
quiet_cmd_alink = AR($(TOOLSET)) $@
cmd_alink = rm -f $@ && $(AR.$(TOOLSET)) crs $@ $(filter %.o,$^)

quiet_cmd_alink_thin = AR($(TOOLSET)) $@
cmd_alink_thin = rm -f $@ && $(AR.$(TOOLSET)) crsT $@ $(filter %.o,$^)

# Due to circular dependencies between libraries :(, we wrap the
# special "figure out circular dependencies" flags around the entire
# input list during linking.
quiet_cmd_link = LINK($(TOOLSET)) $@
cmd_link = $(LINK.$(TOOLSET)) $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ -Wl,--start-group $(LD_INPUTS) -Wl,--end-group $(LIBS)

# We support two kinds of shared objects (.so):
# 1) shared_library, which is just bundling together many dependent libraries
# into a link line.
# 2) loadable_module, which is generating a module intended for dlopen().
#
# They differ only slightly:
# In the former case, we want to package all dependent code into the .so.
# In the latter case, we want to package just the API exposed by the
# outermost module.
# This means shared_library uses --whole-archive, while loadable_module doesn't.
# (Note that --whole-archive is incompatible with the --start-group used in
# normal linking.)

# Other shared-object link notes:
# - Set SONAME to the library filename so our binaries don't reference
# the local, absolute paths used on the link command-line.
quiet_cmd_solink = SOLINK($(TOOLSET)) $@
cmd_solink = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -Wl,-soname=$(@F) -o $@ -Wl,--whole-archive $(LD_INPUTS) -Wl,--no-whole-archive $(LIBS)

quiet_cmd_solink_module = SOLINK_MODULE($(TOOLSET)) $@
cmd_solink_module = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -Wl,-soname=$(@F) -o $@ -Wl,--start-group $(filter-out FORCE_DO_CMD, $^) -Wl,--end-group $(LIBS)
"""

LINK_COMMANDS_MAC = """\
quiet_cmd_alink = LIBTOOL-STATIC $@
cmd_alink = rm -f $@ && ./gyp-mac-tool filter-libtool libtool $(GYP_LIBTOOLFLAGS) -static -o $@ $(filter %.o,$^)

quiet_cmd_link = LINK($(TOOLSET)) $@
cmd_link = $(LINK.$(TOOLSET)) $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o "$@" $(LD_INPUTS) $(LIBS)

quiet_cmd_solink = SOLINK($(TOOLSET)) $@
cmd_solink = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o "$@" $(LD_INPUTS) $(LIBS)

quiet_cmd_solink_module = SOLINK_MODULE($(TOOLSET)) $@
cmd_solink_module = $(LINK.$(TOOLSET)) -bundle $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ $(filter-out FORCE_DO_CMD, $^) $(LIBS)
"""

LINK_COMMANDS_ANDROID = """\
quiet_cmd_alink = AR($(TOOLSET)) $@
cmd_alink = rm -f $@ && $(AR.$(TOOLSET)) crs $@ $(filter %.o,$^)

quiet_cmd_alink_thin = AR($(TOOLSET)) $@
cmd_alink_thin = rm -f $@ && $(AR.$(TOOLSET)) crsT $@ $(filter %.o,$^)

# Due to circular dependencies between libraries :(, we wrap the
# special "figure out circular dependencies" flags around the entire
# input list during linking.
quiet_cmd_link = LINK($(TOOLSET)) $@
quiet_cmd_link_host = LINK($(TOOLSET)) $@
cmd_link = $(LINK.$(TOOLSET)) $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ -Wl,--start-group $(LD_INPUTS) -Wl,--end-group $(LIBS)
cmd_link_host = $(LINK.$(TOOLSET)) $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ $(LD_INPUTS) $(LIBS)

# Other shared-object link notes:
# - Set SONAME to the library filename so our binaries don't reference
# the local, absolute paths used on the link command-line.
quiet_cmd_solink = SOLINK($(TOOLSET)) $@
cmd_solink = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -Wl,-soname=$(@F) -o $@ -Wl,--whole-archive $(LD_INPUTS) -Wl,--no-whole-archive $(LIBS)

quiet_cmd_solink_module = SOLINK_MODULE($(TOOLSET)) $@
cmd_solink_module = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -Wl,-soname=$(@F) -o $@ -Wl,--start-group $(filter-out FORCE_DO_CMD, $^) -Wl,--end-group $(LIBS)
quiet_cmd_solink_module_host = SOLINK_MODULE($(TOOLSET)) $@
cmd_solink_module_host = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -Wl,-soname=$(@F) -o $@ $(filter-out FORCE_DO_CMD, $^) $(LIBS)
"""


LINK_COMMANDS_AIX = """\
quiet_cmd_alink = AR($(TOOLSET)) $@
cmd_alink = rm -f $@ && $(AR.$(TOOLSET)) crs $@ $(filter %.o,$^)

quiet_cmd_alink_thin = AR($(TOOLSET)) $@
cmd_alink_thin = rm -f $@ && $(AR.$(TOOLSET)) crs $@ $(filter %.o,$^)

quiet_cmd_link = LINK($(TOOLSET)) $@
cmd_link = $(LINK.$(TOOLSET)) $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ $(LD_INPUTS) $(LIBS)

quiet_cmd_solink = SOLINK($(TOOLSET)) $@
cmd_solink = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ $(LD_INPUTS) $(LIBS)

quiet_cmd_solink_module = SOLINK_MODULE($(TOOLSET)) $@
cmd_solink_module = $(LINK.$(TOOLSET)) -shared $(GYP_LDFLAGS) $(LDFLAGS.$(TOOLSET)) -o $@ $(filter-out FORCE_DO_CMD, $^) $(LIBS)
"""


# Header of toplevel Makefile.
# This should go into the build tree, but it's easier to keep it here for now.
SHARED_HEADER = ("""\
# We borrow heavily from the kernel build setup, though we are simpler since
# we don't have Kconfig tweaking settings on us.

# The implicit make rules have it looking for RCS files, among other things.
# We instead explicitly write all the rules we care about.
# It's even quicker (saves ~200ms) to pass -r on the command line.
MAKEFLAGS=-r

# The source directory tree.
srcdir := %(srcdir)s
abs_srcdir := $(abspath $(srcdir))

# The name of the builddir.
builddir_name ?= %(builddir)s

# The V=1 flag on command line makes us verbosely print command lines.
ifdef V
  quiet=
else
  quiet=quiet_
endif

# Specify BUILDTYPE=Release on the command line for a release build.
BUILDTYPE ?= %(default_configuration)s

# Directory all our build output goes into.
# Note that this must be two directories beneath src/ for unit tests to pass,
# as they reach into the src/ directory for data with relative paths.
builddir ?= $(builddir_name)/$(BUILDTYPE)
abs_builddir := $(abspath $(builddir))
depsdir := $(builddir)/.deps

# Object output directory.
obj := $(builddir)/obj
abs_obj := $(abspath $(obj))

# We build up a list of every single one of the targets so we can slurp in the
# generated dependency rule Makefiles in one pass.
all_deps :=

%(make_global_settings)s

CC.target ?= %(CC.target)s
CFLAGS.target ?= $(CFLAGS)
CXX.target ?= %(CXX.target)s
CXXFLAGS.target ?= $(CXXFLAGS)
LINK.target ?= %(LINK.target)s
LDFLAGS.target ?= $(LDFLAGS)
AR.target ?= $(AR)

# C++ apps need to be linked with g++.
#
# Note: flock is used to seralize linking. Linking is a memory-intensive
# process so running parallel links can often lead to thrashing.  To disable
# the serialization, override LINK via an envrionment variable as follows:
#
#   export LINK=g++
#
# This will allow make to invoke N linker processes as specified in -jN.
LINK ?= %(flock)s $(builddir)/linker.lock $(CXX.target)

# TODO(evan): move all cross-compilation logic to gyp-time so we don't need
# to replicate this environment fallback in make as well.
CC.host ?= %(CC.host)s
CFLAGS.host ?=
CXX.host ?= %(CXX.host)s
CXXFLAGS.host ?=
LINK.host ?= %(LINK.host)s
LDFLAGS.host ?=
AR.host ?= %(AR.host)s

# Define a dir function that can handle spaces.
# http://www.gnu.org/software/make/manual/make.html#Syntax-of-Functions
# "leading spaces cannot appear in the text of the first argument as written.
# These characters can be put into the argument value by variable substitution."
empty :=
space := $(empty) $(empty)

# http://stackoverflow.com/questions/1189781/using-make-dir-or-notdir-on-a-path-with-spaces
replace_spaces = $(subst $(space),""" + SPACE_REPLACEMENT + """,$1)
unreplace_spaces = $(subst """ + SPACE_REPLACEMENT + """,$(space),$1)
dirx = $(call unreplace_spaces,$(dir $(call replace_spaces,$1)))

# Flags to make gcc output dependency info.  Note that you need to be
# careful here to use the flags that ccache and distcc can understand.
# We write to a dep file on the side first and then rename at the end
# so we can't end up with a broken dep file.
depfile = $(depsdir)/$(call replace_spaces,$@).d
DEPFLAGS = -MMD -MF $(depfile).raw

# We have to fixup the deps output in a few ways.
# (1) the file output should mention the proper .o file.
# ccache or distcc lose the path to the target, so we convert a rule of
# the form:
#   foobar.o: DEP1 DEP2
# into
#   path/to/foobar.o: DEP1 DEP2
# (2) we want missing files not to cause us to fail to build.
# We want to rewrite
#   foobar.o: DEP1 DEP2 \\
#               DEP3
# to
#   DEP1:
#   DEP2:
#   DEP3:
# so if the files are missing, they're just considered phony rules.
# We have to do some pretty insane escaping to get those backslashes
# and dollar signs past make, the shell, and sed at the same time.
# Doesn't work with spaces, but that's fine: .d files have spaces in
# their names replaced with other characters."""
r"""
define fixup_dep
# The depfile may not exist if the input file didn't have any #includes.
touch $(depfile).raw
# Fixup path as in (1).
sed -e "s|^$(notdir $@)|$@|" $(depfile).raw >> $(depfile)
# Add extra rules as in (2).
# We remove slashes and replace spaces with new lines;
# remove blank lines;
# delete the first line and append a colon to the remaining lines.
sed -e 's|\\||' -e 'y| |\n|' $(depfile).raw |\
  grep -v '^$$'                             |\
  sed -e 1d -e 's|$$|:|'                     \
    >> $(depfile)
rm $(depfile).raw
endef
"""
"""
# Command definitions:
# - cmd_foo is the actual command to run;
# - quiet_cmd_foo is the brief-output summary of the command.

quiet_cmd_cc = CC($(TOOLSET)) $@
cmd_cc = $(CC.$(TOOLSET)) $(GYP_CFLAGS) $(DEPFLAGS) $(CFLAGS.$(TOOLSET)) -c -o $@ $<

quiet_cmd_cxx = CXX($(TOOLSET)) $@
cmd_cxx = $(CXX.$(TOOLSET)) $(GYP_CXXFLAGS) $(DEPFLAGS) $(CXXFLAGS.$(TOOLSET)) -c -o $@ $<
%(extra_commands)s
quiet_cmd_touch = TOUCH $@
cmd_touch = touch $@

quiet_cmd_copy = COPY $@
# send stderr to /dev/null to ignore messages when linking directories.
cmd_copy = rm -rf "$@" && cp -af "$<" "$@"

%(link_commands)s
"""

r"""
# Define an escape_quotes function to escape single quotes.
# This allows us to handle quotes properly as long as we always use
# use single quotes and escape_quotes.
escape_quotes = $(subst ','\'',$(1))
# This comment is here just to include a ' to unconfuse syntax highlighting.
# Define an escape_vars function to escape '$' variable syntax.
# This allows us to read/write command lines with shell variables (e.g.
# $LD_LIBRARY_PATH), without triggering make substitution.
escape_vars = $(subst $$,$$$$,$(1))
# Helper that expands to a shell command to echo a string exactly as it is in
# make. This uses printf instead of echo because printf's behaviour with respect
# to escape sequences is more portable than echo's across different shells
# (e.g., dash, bash).
exact_echo = printf '%%s\n' '$(call escape_quotes,$(1))'
"""
"""
# Helper to compare the command we're about to run against the command
# we logged the last time we ran the command.  Produces an empty
# string (false) when the commands match.
# Tricky point: Make has no string-equality test function.
# The kernel uses the following, but it seems like it would have false
# positives, where one string reordered its arguments.
#   arg_check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \\
#                       $(filter-out $(cmd_$@), $(cmd_$(1))))
# We instead substitute each for the empty string into the other, and
# say they're equal if both substitutions produce the empty string.
# .d files contain """ + SPACE_REPLACEMENT + \
                   """ instead of spaces, take that into account.
command_changed = $(or $(subst $(cmd_$(1)),,$(cmd_$(call replace_spaces,$@))),\\
                       $(subst $(cmd_$(call replace_spaces,$@)),,$(cmd_$(1))))

# Helper that is non-empty when a prerequisite changes.
# Normally make does this implicitly, but we force rules to always run
# so we can check their command lines.
#   $? -- new prerequisites
#   $| -- order-only dependencies
prereq_changed = $(filter-out FORCE_DO_CMD,$(filter-out $|,$?))

# Helper that executes all postbuilds until one fails.
define do_postbuilds
  @E=0;\\
  for p in $(POSTBUILDS); do\\
    eval $$p;\\
    E=$$?;\\
    if [ $$E -ne 0 ]; then\\
      break;\\
    fi;\\
  done;\\
  if [ $$E -ne 0 ]; then\\
    rm -rf "$@";\\
    exit $$E;\\
  fi
endef

# do_cmd: run a command via the above cmd_foo names, if necessary.
# Should always run for a given target to handle command-line changes.
# Second argument, if non-zero, makes it do asm/C/C++ dependency munging.
# Third argument, if non-zero, makes it do POSTBUILDS processing.
# Note: We intentionally do NOT call dirx for depfile, since it contains """ + \
                                                     SPACE_REPLACEMENT + """ for
# spaces already and dirx strips the """ + SPACE_REPLACEMENT + \
                                     """ characters.
define do_cmd
$(if $(or $(command_changed),$(prereq_changed)),
  @$(call exact_echo,  $($(quiet)cmd_$(1)))
  @mkdir -p "$(call dirx,$@)" "$(dir $(depfile))"
  $(if $(findstring flock,$(word %(flock_index)d,$(cmd_$1))),
    @$(cmd_$(1))
    @echo "  $(quiet_cmd_$(1)): Finished",
    @$(cmd_$(1))
  )
  @$(call exact_echo,$(call escape_vars,cmd_$(call replace_spaces,$@) := $(cmd_$(1)))) > $(depfile)
  @$(if $(2),$(fixup_dep))
  $(if $(and $(3), $(POSTBUILDS)),
    $(call do_postbuilds)
  )
)
endef

# Declare the "%(default_target)s" target first so it is the default,
# even though we don't have the deps yet.
.PHONY: %(default_target)s
%(default_target)s:

# make looks for ways to re-generate included makefiles, but in our case, we
# don't have a direct way. Explicitly telling make that it has nothing to do
# for them makes it go faster.
%%.d: ;

# Use FORCE_DO_CMD to force a target to run.  Should be coupled with
# do_cmd.
.PHONY: FORCE_DO_CMD
FORCE_DO_CMD:

""")

SHARED_HEADER_MAC_COMMANDS = """
quiet_cmd_objc = CXX($(TOOLSET)) $@
cmd_objc = $(CC.$(TOOLSET)) $(GYP_OBJCFLAGS) $(DEPFLAGS) -c -o $@ $<

quiet_cmd_objcxx = CXX($(TOOLSET)) $@
cmd_objcxx = $(CXX.$(TOOLSET)) $(GYP_OBJCXXFLAGS) $(DEPFLAGS) -c -o $@ $<

# Commands for precompiled header files.
quiet_cmd_pch_c = CXX($(TOOLSET)) $@
cmd_pch_c = $(CC.$(TOOLSET)) $(GYP_PCH_CFLAGS) $(DEPFLAGS) $(CXXFLAGS.$(TOOLSET)) -c -o $@ $<
quiet_cmd_pch_cc = CXX($(TOOLSET)) $@
cmd_pch_cc = $(CC.$(TOOLSET)) $(GYP_PCH_CXXFLAGS) $(DEPFLAGS) $(CXXFLAGS.$(TOOLSET)) -c -o $@ $<
quiet_cmd_pch_m = CXX($(TOOLSET)) $@
cmd_pch_m = $(CC.$(TOOLSET)) $(GYP_PCH_OBJCFLAGS) $(DEPFLAGS) -c -o $@ $<
quiet_cmd_pch_mm = CXX($(TOOLSET)) $@
cmd_pch_mm = $(CC.$(TOOLSET)) $(GYP_PCH_OBJCXXFLAGS) $(DEPFLAGS) -c -o $@ $<

# gyp-mac-tool is written next to the root Makefile by gyp.
# Use $(4) for the command, since $(2) and $(3) are used as flag by do_cmd
# already.
quiet_cmd_mac_tool = MACTOOL $(4) $<
cmd_mac_tool = ./gyp-mac-tool $(4) $< "$@"

quiet_cmd_mac_package_framework = PACKAGE FRAMEWORK $@
cmd_mac_package_framework = ./gyp-mac-tool package-framework "$@" $(4)

quiet_cmd_infoplist = INFOPLIST $@
cmd_infoplist = $(CC.$(TOOLSET)) -E -P -Wno-trigraphs -x c $(INFOPLIST_DEFINES) "$<" -o "$@"
"""


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')


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


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


SHARED_FOOTER = """\
# "all" is a concatenation of the "all" targets from all the included
# sub-makefiles. This is just here to clarify.
all:

# Add in dependency-tracking rules.  $(all_deps) is the list of every single
# target in our tree. Only consider the ones with .d (dependency) info:
d_files := $(wildcard $(foreach f,$(all_deps),$(depsdir)/$(f).d))
ifneq ($(d_files),)
  include $(d_files)
endif
"""

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',
}

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


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)


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


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


# 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 = {}


class MakefileWriter:
  """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, configs: gyp info
      part_of_all: flag indicating this target is part of 'all'
    """
    ensure_directory_exists(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 = gyp.xcode_emulation.IsMacBundle(self.flavor, spec)
    if self.flavor == 'mac':
      self.xcode_settings = gyp.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(spec)
      self.output_binary = self.ComputeMacBundleBinaryOutput(spec)
    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, part_of_all)

    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)

    # Sources.
    all_sources = spec.get('sources', []) + extra_sources
    if all_sources:
      self.WriteSources(
          configs, deps, all_sources, extra_outputs,
          extra_link_deps, part_of_all,
          gyp.xcode_emulation.MacPrefixHeader(
              self.xcode_settings, lambda p: Sourceify(self.Absolutify(p)),
              self.Pchify))
      sources = filter(Compilable, all_sources)
      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
    """
    ensure_directory_exists(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:
        dir = os.path.split(out)[0]
        if dir:
          dirs.add(dir)
      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 = map(self.Absolutify, 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 input in inputs:
        assert ' ' not in input, (
            "Spaces in action input filenames not supported (%s)"  % input)
      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, part_of_all):
    """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:
          dir = os.path.dirname(out)
          if dir:
            dirs.add(dir)
        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 = map(self.Absolutify, 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 := $(abs_builddir)' % outputs[0])
        self.WriteMakeRule(outputs, inputs + ['FORCE_DO_CMD'], actions)
        # Spaces in rule filenames are not supported, but rule variables have
        # spaces in them (e.g. RULE_INPUT_PATH expands to '$(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')

    for output, res in gyp.xcode_emulation.GetMacBundleResources(
        generator_default_variables['PRODUCT_DIR'], self.xcode_settings,
        map(Sourceify, map(self.Absolutify, resources))):
      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,
                   part_of_all, 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')

      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 = map(Sourceify, map(self.Absolutify, includes))
      self.WriteList(includes, 'INCS_%s' % configname, prefix='-I')

    compilable = filter(Compilable, sources)
    objs = map(self.Objectify, map(self.Absolutify, map(Target, 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 += filter(Linkable, sources)

    self.WriteLn()

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

    for gch, lang_flag, lang, input 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, input))
      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'
      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, spec):
    """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, spec):
    """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())


  def ComputeDeps(self, 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, target, 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, configs: input from gyp.
    deps, 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(self.output_binary, 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 in xrange(len(postbuilds)):
        if not postbuilds[i].startswith('$'):
          postbuilds[i] = EscapeShellArgument(postbuilds[i])
      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(self.output, 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', '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, 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))


  def WriteDoCmd(self, outputs, inputs, command, part_of_all, comment=None,
                 postbuilds=False):
    """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,
                       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):
    """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
    """
    outputs = map(QuoteSpaces, outputs)
    inputs = map(QuoteSpaces, inputs)

    if comment:
      self.WriteLn('# ' + comment)
    if phony:
      self.WriteLn('.PHONY: ' + ' '.join(outputs))
    # TODO(evanm): just make order_only a list of deps instead of these hacks.
    if order_only:
      order_insert = '| '
      pick_output = ' '.join(outputs)
    else:
      order_insert = ''
      pick_output = outputs[0]
    if force:
      force_append = ' FORCE_DO_CMD'
    else:
      force_append = ''
    if actions:
      self.WriteLn("%s: TOOLSET := $(TOOLSET)" % outputs[0])
    self.WriteLn('%s: %s%s%s' % (pick_output, order_insert, ' '.join(inputs),
                                 force_append))
    if actions:
      for action in actions:
        self.WriteLn('\t%s' % action)
    if not order_only and len(outputs) > 1:
      # If we have more than one output, a rule like
      #   foo bar: baz
      # that for *each* output we must run the action, potentially
      # in parallel.  That is not what we're trying to write -- what
      # we want is that we run the action once and it generates all
      # the files.
      # http://www.gnu.org/software/hello/manual/automake/Multiple-Outputs.html
      # discusses this problem and has this solution:
      # 1) Write the naive rule that would produce parallel runs of
      # the action.
      # 2) Make the outputs seralized on each other, so we won't start
      # a parallel run until the first run finishes, at which point
      # we'll have generated all the outputs and we're done.
      self.WriteLn('%s: %s' % (' '.join(outputs[1:]), outputs[0]))
      # Add a dummy command to the "extra outputs" rule, otherwise make seems to
      # think these outputs haven't (couldn't have?) changed, and thus doesn't
      # flag them as changed (i.e. include in '$?') when evaluating dependent
      # rules, which in turn causes do_cmd() to skip running dependent commands.
      self.WriteLn('%s: ;' % (' '.join(outputs[1:])))
    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:
        filename = os.path.basename(filepath)
        if filename.startswith(prefix) and filename.endswith(suffix):
          modules.append(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))


  def ExpandInputRoot(self, 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.

    # XXX(TooTallNate): disabling this code since we don't want this behavior...
    #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


def WriteAutoRegenerationRule(params, root_makefile, makefile_name,
                              build_files):
  """Write the target to regenerate the Makefile."""
  options = params['options']
  build_files_args = [gyp.common.RelativePath(filename, options.toplevel_dir)
                      for filename in params['build_files_arg']]

  gyp_binary = gyp.common.FixIfRelativePath(params['gyp_binary'],
                                            options.toplevel_dir)
  if not gyp_binary.startswith(os.sep):
    gyp_binary = os.path.join('.', gyp_binary)

  root_makefile.write(
      "quiet_cmd_regen_makefile = ACTION Regenerating $@\n"
      "cmd_regen_makefile = cd $(srcdir); %(cmd)s\n"
      "%(makefile_name)s: %(deps)s\n"
      "\t$(call do_cmd,regen_makefile)\n\n" % {
          'makefile_name': makefile_name,
          'deps': ' '.join(map(Sourceify, build_files)),
          'cmd': gyp.common.EncodePOSIXShellList(
                     [gyp_binary, '-fmake'] +
                     gyp.RegenerateFlags(options) +
                     build_files_args)})


def PerformBuild(data, configurations, params):
  options = params['options']
  for config in configurations:
    arguments = ['make']
    if options.toplevel_dir and options.toplevel_dir != '.':
      arguments += '-C', options.toplevel_dir
    arguments.append('BUILDTYPE=' + config)
    print 'Building [%s]: %s' % (config, arguments)
    subprocess.check_call(arguments)


def GenerateOutput(target_list, target_dicts, data, params):
  options = params['options']
  flavor = gyp.common.GetFlavor(params)
  generator_flags = params.get('generator_flags', {})
  builddir_name = generator_flags.get('output_dir', 'out')
  android_ndk_version = generator_flags.get('android_ndk_version', None)
  default_target = generator_flags.get('default_target', 'all')

  def CalculateMakefilePath(build_file, base_name):
    """Determine where to write a Makefile for a given gyp file."""
    # Paths in gyp files are relative to the .gyp file, but we want
    # paths relative to the source root for the master makefile.  Grab
    # the path of the .gyp file as the base to relativize against.
    # E.g. "foo/bar" when we're constructing targets for "foo/bar/baz.gyp".
    base_path = gyp.common.RelativePath(os.path.dirname(build_file),
                                        options.depth)
    # We write the file in the base_path directory.
    output_file = os.path.join(options.depth, base_path, base_name)
    if options.generator_output:
      output_file = os.path.join(options.generator_output, output_file)
    base_path = gyp.common.RelativePath(os.path.dirname(build_file),
                                        options.toplevel_dir)
    return base_path, output_file

  # TODO:  search for the first non-'Default' target.  This can go
  # away when we add verification that all targets have the
  # necessary configurations.
  default_configuration = None
  toolsets = set([target_dicts[target]['toolset'] for target in target_list])
  for target in target_list:
    spec = target_dicts[target]
    if spec['default_configuration'] != 'Default':
      default_configuration = spec['default_configuration']
      break
  if not default_configuration:
    default_configuration = 'Default'

  srcdir = '.'
  makefile_name = 'Makefile' + options.suffix
  makefile_path = os.path.join(options.toplevel_dir, makefile_name)
  if options.generator_output:
    global srcdir_prefix
    makefile_path = os.path.join(options.generator_output, makefile_path)
    srcdir = gyp.common.RelativePath(srcdir, options.generator_output)
    srcdir_prefix = '$(srcdir)/'

  flock_command= 'flock'
  header_params = {
      'default_target': default_target,
      'builddir': builddir_name,
      'default_configuration': default_configuration,
      'flock': flock_command,
      'flock_index': 1,
      'link_commands': LINK_COMMANDS_LINUX,
      'extra_commands': '',
      'srcdir': srcdir,
    }
  if flavor == 'mac':
    flock_command = './gyp-mac-tool flock'
    header_params.update({
        'flock': flock_command,
        'flock_index': 2,
        'link_commands': LINK_COMMANDS_MAC,
        'extra_commands': SHARED_HEADER_MAC_COMMANDS,
    })
  elif flavor == 'android':
    header_params.update({
        'link_commands': LINK_COMMANDS_ANDROID,
    })
  elif flavor == 'solaris':
    header_params.update({
        'flock': './gyp-flock-tool flock',
        'flock_index': 2,
    })
  elif flavor == 'freebsd':
    # Note: OpenBSD has sysutils/flock. lockf seems to be FreeBSD specific.
    header_params.update({
        'flock': 'lockf',
    })
  elif flavor == 'aix':
    header_params.update({
        'link_commands': LINK_COMMANDS_AIX,
        'flock': './gyp-flock-tool flock',
        'flock_index': 2,
    })

  header_params.update({
    'CC.target':   GetEnvironFallback(('CC_target', 'CC'), '$(CC)'),
    'AR.target':   GetEnvironFallback(('AR_target', 'AR'), '$(AR)'),
    'CXX.target':  GetEnvironFallback(('CXX_target', 'CXX'), '$(CXX)'),
    'LINK.target': GetEnvironFallback(('LINK_target', 'LINK'), '$(LINK)'),
    'CC.host':     GetEnvironFallback(('CC_host',), 'gcc'),
    'AR.host':     GetEnvironFallback(('AR_host',), 'ar'),
    'CXX.host':    GetEnvironFallback(('CXX_host',), 'g++'),
    'LINK.host':   GetEnvironFallback(('LINK_host',), '$(CXX.host)'),
  })

  build_file, _, _ = gyp.common.ParseQualifiedTarget(target_list[0])
  make_global_settings_array = data[build_file].get('make_global_settings', [])
  wrappers = {}
  wrappers['LINK'] = '%s $(builddir)/linker.lock' % flock_command
  for key, value in make_global_settings_array:
    if key.endswith('_wrapper'):
      wrappers[key[:-len('_wrapper')]] = '$(abspath %s)' % value
  make_global_settings = ''
  for key, value in make_global_settings_array:
    if re.match('.*_wrapper', key):
      continue
    if value[0] != '$':
      value = '$(abspath %s)' % value
    wrapper = wrappers.get(key)
    if wrapper:
      value = '%s %s' % (wrapper, value)
      del wrappers[key]
    if key in ('CC', 'CC.host', 'CXX', 'CXX.host'):
      make_global_settings += (
          'ifneq (,$(filter $(origin %s), undefined default))\n' % key)
      # Let gyp-time envvars win over global settings.
      if key in os.environ:
        value = os.environ[key]
      make_global_settings += '  %s = %s\n' % (key, value)
      make_global_settings += 'endif\n'
    else:
      make_global_settings += '%s ?= %s\n' % (key, value)
  # TODO(ukai): define cmd when only wrapper is specified in
  # make_global_settings.

  header_params['make_global_settings'] = make_global_settings

  ensure_directory_exists(makefile_path)
  root_makefile = open(makefile_path, 'w')
  root_makefile.write(SHARED_HEADER % header_params)
  # Currently any versions have the same effect, but in future the behavior
  # could be different.
  if android_ndk_version:
    root_makefile.write(
        '# Define LOCAL_PATH for build of Android applications.\n'
        'LOCAL_PATH := $(call my-dir)\n'
        '\n')
  for toolset in toolsets:
    root_makefile.write('TOOLSET := %s\n' % toolset)
    WriteRootHeaderSuffixRules(root_makefile)

  # Put build-time support tools next to the root Makefile.
  dest_path = os.path.dirname(makefile_path)
  gyp.common.CopyTool(flavor, dest_path)

  # Find the list of targets that derive from the gyp file(s) being built.
  needed_targets = set()
  for build_file in params['build_files']:
    for target in gyp.common.AllTargets(target_list, target_dicts, build_file):
      needed_targets.add(target)

  build_files = set()
  include_list = set()
  for qualified_target in target_list:
    build_file, target, toolset = gyp.common.ParseQualifiedTarget(
        qualified_target)

    this_make_global_settings = data[build_file].get('make_global_settings', [])
    assert make_global_settings_array == this_make_global_settings, (
        "make_global_settings needs to be the same for all targets.")

    build_files.add(gyp.common.RelativePath(build_file, options.toplevel_dir))
    included_files = data[build_file]['included_files']
    for included_file in included_files:
      # The included_files entries are relative to the dir of the build file
      # that included them, so we have to undo that and then make them relative
      # to the root dir.
      relative_include_file = gyp.common.RelativePath(
          gyp.common.UnrelativePath(included_file, build_file),
          options.toplevel_dir)
      abs_include_file = os.path.abspath(relative_include_file)
      # If the include file is from the ~/.gyp dir, we should use absolute path
      # so that relocating the src dir doesn't break the path.
      if (params['home_dot_gyp'] and
          abs_include_file.startswith(params['home_dot_gyp'])):
        build_files.add(abs_include_file)
      else:
        build_files.add(relative_include_file)

    base_path, output_file = CalculateMakefilePath(build_file,
        target + '.' + toolset + options.suffix + '.mk')

    spec = target_dicts[qualified_target]
    configs = spec['configurations']

    if flavor == 'mac':
      gyp.xcode_emulation.MergeGlobalXcodeSettingsToSpec(data[build_file], spec)

    writer = MakefileWriter(generator_flags, flavor)
    writer.Write(qualified_target, base_path, output_file, spec, configs,
                 part_of_all=qualified_target in needed_targets)

    # Our root_makefile lives at the source root.  Compute the relative path
    # from there to the output_file for including.
    mkfile_rel_path = gyp.common.RelativePath(output_file,
                                              os.path.dirname(makefile_path))
    include_list.add(mkfile_rel_path)

  # Write out per-gyp (sub-project) Makefiles.
  depth_rel_path = gyp.common.RelativePath(options.depth, os.getcwd())
  for build_file in build_files:
    # The paths in build_files were relativized above, so undo that before
    # testing against the non-relativized items in target_list and before
    # calculating the Makefile path.
    build_file = os.path.join(depth_rel_path, build_file)
    gyp_targets = [target_dicts[target]['target_name'] for target in target_list
                   if target.startswith(build_file) and
                   target in needed_targets]
    # Only generate Makefiles for gyp files with targets.
    if not gyp_targets:
      continue
    base_path, output_file = CalculateMakefilePath(build_file,
        os.path.splitext(os.path.basename(build_file))[0] + '.Makefile')
    makefile_rel_path = gyp.common.RelativePath(os.path.dirname(makefile_path),
                                                os.path.dirname(output_file))
    writer.WriteSubMake(output_file, makefile_rel_path, gyp_targets,
                        builddir_name)


  # Write out the sorted list of includes.
  root_makefile.write('\n')
  for include_file in sorted(include_list):
    # We wrap each .mk include in an if statement so users can tell make to
    # not load a file by setting NO_LOAD.  The below make code says, only
    # load the .mk file if the .mk filename doesn't start with a token in
    # NO_LOAD.
    root_makefile.write(
        "ifeq ($(strip $(foreach prefix,$(NO_LOAD),\\\n"
        "    $(findstring $(join ^,$(prefix)),\\\n"
        "                 $(join ^," + include_file + ")))),)\n")
    root_makefile.write("  include " + include_file + "\n")
    root_makefile.write("endif\n")
  root_makefile.write('\n')

  if (not generator_flags.get('standalone')
      and generator_flags.get('auto_regeneration', True)):
    WriteAutoRegenerationRule(params, root_makefile, makefile_name, build_files)

  root_makefile.write(SHARED_FOOTER)

  root_makefile.close()
