build/core/init.mk - platform/ndk - Git at Google

 # Copyright (C) 2009-2010 The Android Open Source Project
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #      http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #

 # Initialization of the NDK build system. This file is included by
 # several build scripts.
 #

 # Disable GNU Make implicit rules

 # this turns off the suffix rules built into make
 .SUFFIXES:

 # this turns off the RCS / SCCS implicit rules of GNU Make
 % : RCS/%,v
 % : RCS/%
 % : %,v
 % : s.%
 % : SCCS/s.%

 # If a rule fails, delete $@.
 .DELETE_ON_ERROR:


 # Define NDK_LOG=1 in your environment to display log traces when
 # using the build scripts. See also the definition of ndk_log below.
 #
 NDK_LOG := $(strip $(NDK_LOG))
 ifeq ($(NDK_LOG),true)
     override NDK_LOG := 1
 endif

 # Check that we have at least GNU Make 3.81
 # We do this by detecting whether 'lastword' is supported
 #
 MAKE_TEST := $(lastword a b c d e f)
 ifneq ($(MAKE_TEST),f)
     $(error Android NDK: GNU Make version $(MAKE_VERSION) is too low (should be >= 3.81))
 endif
 ifeq ($(NDK_LOG),1)
     $(info Android NDK: GNU Make version $(MAKE_VERSION) detected)
 endif

 # NDK_ROOT *must* be defined and point to the root of the NDK installation
 NDK_ROOT := $(strip $(NDK_ROOT))
 ifndef NDK_ROOT
     $(error ERROR while including init.mk: NDK_ROOT must be defined !)
 endif
 ifneq ($(words $(NDK_ROOT)),1)
     $(info,The Android NDK installation path contains spaces: '$(NDK_ROOT)')
     $(error,Please fix the problem by reinstalling to a different location.)
 endif

 # ====================================================================
 #
 # Define a few useful variables and functions.
 # More stuff will follow in definitions.mk.
 #
 # ====================================================================

 # Used to output warnings and error from the library, it's possible to
 # disable any warnings or errors by overriding these definitions
 # manually or by setting NDK_NO_WARNINGS or NDK_NO_ERRORS

 __ndk_name    := Android NDK
 __ndk_info     = $(info $(__ndk_name): $1 $2 $3 $4 $5)
 __ndk_warning  = $(warning $(__ndk_name): $1 $2 $3 $4 $5)
 __ndk_error    = $(error $(__ndk_name): $1 $2 $3 $4 $5)

 ifdef NDK_NO_INFO
 __ndk_info :=
 endif
 ifdef NDK_NO_WARNINGS
 __ndk_warning :=
 endif
 ifdef NDK_NO_ERRORS
 __ndk_error :=
 endif

 # -----------------------------------------------------------------------------
 # Function : ndk_log
 # Arguments: 1: text to print when NDK_LOG is defined to 1
 # Returns  : None
 # Usage    : $(call ndk_log,<some text>)
 # -----------------------------------------------------------------------------
 ifeq ($(NDK_LOG),1)
 ndk_log = $(info $(__ndk_name): $1)
 else
 ndk_log :=
 endif

 # -----------------------------------------------------------------------------
 # Function : host-toolchain-path
 # Arguments: 1: NDK root
 #            2: Toolchain name
 # Returns  : The parent path of all toolchains for this host. Note that
 #            HOST_TAG64 == HOST_TAG for 32-bit systems.
 # -----------------------------------------------------------------------------
 ifeq ($(NDK_NEW_TOOLCHAINS_LAYOUT),true)
     host-toolchain-path = $1/$(HOST_TAG64)/$2
 else
     host-toolchain-path = $1/$2/prebuilt/$(HOST_TAG64)
 endif

 # -----------------------------------------------------------------------------
 # Function : get-gcclibs-path
 # Arguments: 1: NDK root
 #            2: Toolchain name (no version number)
 # Returns  : Path to the given prebuilt gcclibs.
 # -----------------------------------------------------------------------------
 get-gcclibs-path = $1/gcclibs/$2

 # ====================================================================
 #
 # Host system auto-detection.
 #
 # ====================================================================

 #
 # Determine host system and architecture from the environment
 #
 HOST_OS := $(strip $(HOST_OS))
 ifndef HOST_OS
     # On all modern variants of Windows (including Cygwin and Wine)
     # the OS environment variable is defined to 'Windows_NT'
     #
     # The value of PROCESSOR_ARCHITECTURE will be x86 or AMD64
     #
     ifeq ($(OS),Windows_NT)
         HOST_OS := windows
     else
         # For other systems, use the `uname` output
         UNAME := $(shell uname -s)
         ifneq (,$(findstring Linux,$(UNAME)))
             HOST_OS := linux
         endif
         ifneq (,$(findstring Darwin,$(UNAME)))
             HOST_OS := darwin
         endif
         # We should not be there, but just in case !
         ifneq (,$(findstring CYGWIN,$(UNAME)))
             $(call __ndk_warning,Unsupported build environment CYGWIN.)
             HOST_OS := windows
         endif
         ifneq (,$(findstring MINGW64,$(UNAME)))
             $(call __ndk_warning,Unsupported build environment MSYS.)
             HOST_OS := windows
         endif
         ifeq ($(HOST_OS),)
             $(call __ndk_info,Unable to determine HOST_OS from uname -s: $(UNAME))
             $(call __ndk_info,Please define HOST_OS in your environment.)
             $(call __ndk_error,Aborting.)
         endif
     endif
     $(call ndk_log,Host OS was auto-detected: $(HOST_OS))
 else
     $(call ndk_log,Host OS from environment: $(HOST_OS))
 endif

 # For all systems, we will have HOST_OS_BASE defined as
 # $(HOST_OS), except on Cygwin where we will have:
 #
 #  HOST_OS      == cygwin
 #  HOST_OS_BASE == windows
 #
 # Trying to detect that we're running from Cygwin is tricky
 # because we can't use $(OSTYPE): It's a Bash shell variable
 # that is not exported to sub-processes, and isn't defined by
 # other shells (for those with really weird setups).
 #
 # Instead, we assume that a program named /bin/uname.exe
 # that can be invoked and returns a valid value corresponds
 # to a Cygwin installation.
 #
 HOST_OS_BASE := $(HOST_OS)

 ifeq ($(HOST_OS),windows)
     ifneq (,$(strip $(wildcard /bin/uname.exe)))
         $(call ndk_log,Found /bin/uname.exe on Windows host, checking for Cygwin)
         # NOTE: The 2>NUL here is for the case where we're running inside the
         #       native Windows shell. On cygwin, this will create an empty NUL file
         #       that we're going to remove later (see below).
         UNAME := $(shell /bin/uname.exe -s 2>NUL)
         $(call ndk_log,uname -s returned: $(UNAME))
         ifneq (,$(filter CYGWIN%,$(UNAME)))
             $(call ndk_log,Cygwin detected: $(shell uname -a))
             HOST_OS := cygwin
             _ := $(shell rm -f NUL) # Cleaning up
         else
             ifneq (,$(filter MINGW32%,$(UNAME)))
                 $(call ndk_log,MSys detected: $(shell uname -a))
                 HOST_OS := cygwin
             else
                 $(call ndk_log,Cygwin *not* detected!)
             endif
         endif
     endif
 endif

 ifneq ($(HOST_OS),$(HOST_OS_BASE))
     $(call ndk_log, Host operating system detected: $(HOST_OS), base OS: $(HOST_OS_BASE))
 else
     $(call ndk_log, Host operating system detected: $(HOST_OS))
 endif

 HOST_ARCH := $(strip $(HOST_ARCH))
 HOST_ARCH64 :=
 ifndef HOST_ARCH
     ifeq ($(HOST_OS_BASE),windows)
         # In the case that we're a 32-bit make (shouldn't be the case, but maybe
         # the user is using their own make binary rather than the NDK's), on a
         # 64-bit OS, PROCESSOR_ARCHITECTURE will be x86 but
         # PROCESSOR_ARCHITEW6432 will be AMD64. If PROCESSOR_ARCHITECTURE is x86
         # and PROCESSOR_ARCHITEW6432 is empty, this is a 32-bit OS.
         # https://blogs.msdn.microsoft.com/david.wang/2006/03/27/howto-detect-process-bitness/
         ifeq ($(PROCESSOR_ARCHITECTURE)$(PROCESSOR_ARCHITEW6432),x86)
             $(call __ndk_error,32-bit Windows is supported.)
         endif
     endif
     HOST_ARCH := x86
     HOST_ARCH64 := x86_64
 else
     $(call ndk_log,Host CPU from environment: $(HOST_ARCH))
 endif

 ifeq (,$(HOST_ARCH64))
     HOST_ARCH64 := $(HOST_ARCH)
 endif

 HOST_TAG := $(HOST_OS_BASE)-$(HOST_ARCH)
 HOST_TAG64 := $(HOST_OS_BASE)-$(HOST_ARCH64)

 # The directory separator used on this host
 HOST_DIRSEP := :
 ifeq ($(HOST_OS),windows)
   HOST_DIRSEP := ;
 endif

 # The host executable extension
 HOST_EXEEXT :=
 ifeq ($(HOST_OS),windows)
   HOST_EXEEXT := .exe
 endif

 ifeq ($(HOST_TAG),windows-x86)
     # If we are on Windows, we need to check that we are not running Cygwin 1.5,
     # which is deprecated and won't run our toolchain binaries properly.
     ifeq ($(HOST_OS),cygwin)
         # On cygwin, 'uname -r' returns something like 1.5.23(0.225/5/3)
         # We recognize 1.5. as the prefix to look for then.
         CYGWIN_VERSION := $(shell uname -r)
         ifneq ($(filter XX1.5.%,XX$(CYGWIN_VERSION)),)
             $(call __ndk_info,You seem to be running Cygwin 1.5, which is not supported.)
             $(call __ndk_info,Please upgrade to Cygwin 1.7 or higher.)
             $(call __ndk_error,Aborting.)
         endif
     endif

     # special-case the host-tag
     HOST_TAG := windows
 endif

 $(call ndk_log,HOST_TAG set to $(HOST_TAG))

 # Check for NDK-specific versions of our host tools
 HOST_TOOLS_ROOT := $(NDK_ROOT)/prebuilt/$(HOST_TAG64)
 HOST_PREBUILT := $(strip $(wildcard $(HOST_TOOLS_ROOT)/bin))
 HOST_MAKE := $(strip $(NDK_HOST_MAKE))
 HOST_PYTHON := $(strip $(NDK_HOST_PYTHON))
 TOOLCHAIN_ROOT := $(NDK_ROOT)/toolchains/llvm/prebuilt/$(HOST_TAG64)
 ifdef HOST_PREBUILT
     $(call ndk_log,Host tools prebuilt directory: $(HOST_PREBUILT))
     # The windows prebuilt binaries are for ndk-build.cmd
     # On cygwin, we must use the Cygwin version of these tools instead.
     ifneq ($(HOST_OS),cygwin)
         ifndef HOST_MAKE
             HOST_MAKE := $(wildcard $(HOST_PREBUILT)/make$(HOST_EXEEXT))
         endif
        ifndef HOST_PYTHON
             ifeq ($(HOST_OS),windows)
                 HOST_PYTHON := $(wildcard $(TOOLCHAIN_ROOT)/python3/python$(HOST_EXEEXT))
             else
                 HOST_PYTHON := $(wildcard $(TOOLCHAIN_ROOT)/python3/bin/python3$(HOST_EXEEXT))
             endif
         endif
     endif
 else
     $(call ndk_log,Host tools prebuilt directory not found, using system tools)
 endif
 ifndef HOST_PYTHON
     HOST_PYTHON := python
 endif

 HOST_ECHO := $(strip $(NDK_HOST_ECHO))
 ifdef HOST_PREBUILT
     ifndef HOST_ECHO
         # Special case, on Cygwin, always use the host echo, not our prebuilt one
         # which adds \r\n at the end of lines.
         ifneq ($(HOST_OS),cygwin)
             HOST_ECHO := $(strip $(wildcard $(HOST_PREBUILT)/echo$(HOST_EXEEXT)))
         endif
     endif
 endif
 ifndef HOST_ECHO
     HOST_ECHO := echo
 endif
 $(call ndk_log,Host 'echo' tool: $(HOST_ECHO))

 # Define HOST_ECHO_N to perform the equivalent of 'echo -n' on all platforms.
 ifeq ($(HOST_OS),windows)
   # Our custom toolbox echo binary supports -n.
   HOST_ECHO_N := $(HOST_ECHO) -n
 else
   # On Posix, just use bare printf.
   HOST_ECHO_N := printf %s
 endif
 $(call ndk_log,Host 'echo -n' tool: $(HOST_ECHO_N))

 HOST_CMP := $(strip $(NDK_HOST_CMP))
 ifdef HOST_PREBUILT
     ifndef HOST_CMP
         HOST_CMP := $(strip $(wildcard $(HOST_PREBUILT)/cmp$(HOST_EXEEXT)))
     endif
 endif
 ifndef HOST_CMP
     HOST_CMP := cmp
 endif
 $(call ndk_log,Host 'cmp' tool: $(HOST_CMP))

 # Location of python build helpers.
 BUILD_PY := $(NDK_ROOT)/build

 #
 # On Cygwin/MSys, define the 'cygwin-to-host-path' function here depending on the
 # environment. The rules are the following:
 #
 # 1/ If NDK_USE_CYGPATH=1 and cygpath does exist in your path, cygwin-to-host-path
 #    calls "cygpath -m" for each host path.  Since invoking 'cygpath -m' from GNU
 #    Make for each source file is _very_ slow, this is only a backup plan in
 #    case our automatic substitution function (described below) doesn't work.
 #
 # 2/ Generate a Make function that performs the mapping from cygwin/msys to host
 #    paths through simple substitutions.  It's really a series of nested patsubst
 #    calls, that loo like:
 #
 #     cygwin-to-host-path = $(patsubst /cygdrive/c/%,c:/%,\
 #                             $(patsusbt /cygdrive/d/%,d:/%, \
 #                              $1)
 #    or in MSys:
 #     cygwin-to-host-path = $(patsubst /c/%,c:/%,\
 #                             $(patsusbt /d/%,d:/%, \
 #                              $1)
 #
 # except that the actual definition is built from the list of mounted
 # drives as reported by "mount" and deals with drive letter cases (i.e.
 # '/cygdrive/c' and '/cygdrive/C')
 #
 ifeq ($(HOST_OS),cygwin)
     CYGPATH := $(strip $(HOST_CYGPATH))
     ifndef CYGPATH
         $(call ndk_log, Probing for 'cygpath' program)
         CYGPATH := $(strip $(shell which cygpath 2>/dev/null))
         ifndef CYGPATH
             $(call ndk_log, 'cygpath' was *not* found in your path)
         else
             $(call ndk_log, 'cygpath' found as: $(CYGPATH))
         endif
     endif

     ifeq ($(NDK_USE_CYGPATH),1)
         ifndef CYGPATH
             $(call __ndk_info,No cygpath)
             $(call __ndk_error,Aborting)
         endif
         $(call ndk_log, Forced usage of 'cygpath -m' through NDK_USE_CYGPATH=1)
         cygwin-to-host-path = $(strip $(shell $(CYGPATH) -m $1))
     else
         # Call a Python script to generate a Makefile function that approximates
         # cygpath.
         WINDOWS_HOST_PATH_FRAGMENT := $(shell mount | $(HOST_PYTHON) $(BUILD_PY)/gen_cygpath.py)
         $(eval cygwin-to-host-path = $(WINDOWS_HOST_PATH_FRAGMENT))
     endif
 endif # HOST_OS == cygwin

 # The location of the build system files
 BUILD_SYSTEM := $(NDK_ROOT)/build/core

 # Include common definitions
 include $(BUILD_SYSTEM)/definitions.mk

 # ====================================================================
 #
 # Read all platform-specific configuration files.
 #
 # Each platform must be located in build/platforms/android-<apilevel>
 # where <apilevel> corresponds to an API level number, with:
 #   3 -> Android 1.5
 #   4 -> next platform release
 #
 # ====================================================================

 # ====================================================================
 #
 # Read all toolchain-specific configuration files.
 #
 # Each toolchain must have a corresponding config.mk file located
 # in build/toolchains/<name>/ that will be included here.
 #
 # Each one of these files should define the following variables:
 #   TOOLCHAIN_NAME   toolchain name (e.g. arm-linux-androideabi-4.9)
 #   TOOLCHAIN_ABIS   list of target ABIs supported by the toolchain.
 #
 # Then, it should include $(ADD_TOOLCHAIN) which will perform
 # book-keeping for the build system.
 #
 # ====================================================================

 # the build script to include in each toolchain config.mk
 ADD_TOOLCHAIN := $(BUILD_SYSTEM)/add-toolchain.mk

 # checkbuild.py generates these two files from the files in $NDK/meta.
 include $(BUILD_SYSTEM)/abis.mk
 include $(BUILD_SYSTEM)/platforms.mk

 NDK_KNOWN_DEVICE_ABIS := $(NDK_KNOWN_DEVICE_ABI64S) $(NDK_KNOWN_DEVICE_ABI32S)

 NDK_APP_ABI_ALL_EXPANDED := $(NDK_KNOWN_DEVICE_ABIS)
 NDK_APP_ABI_ALL32_EXPANDED := $(NDK_KNOWN_DEVICE_ABI32S)
 NDK_APP_ABI_ALL64_EXPANDED := $(NDK_KNOWN_DEVICE_ABI64S)

 NDK_MIN_PLATFORM := android-$(NDK_MIN_PLATFORM_LEVEL)
 NDK_MAX_PLATFORM := android-$(NDK_MAX_PLATFORM_LEVEL)

 $(call ndk_log,Found max platform level: $(NDK_MAX_PLATFORM_LEVEL))

 # the list of all toolchains in this NDK
 NDK_ALL_TOOLCHAINS :=
 NDK_ALL_ABIS       :=
 NDK_ALL_ARCHS      :=

 TOOLCHAIN_CONFIGS := $(wildcard $(NDK_ROOT)/build/core/toolchains/*/config.mk)
 $(foreach _config_mk,$(TOOLCHAIN_CONFIGS),\
   $(eval include $(BUILD_SYSTEM)/add-toolchain.mk)\
 )

 NDK_ALL_TOOLCHAINS   := $(sort $(NDK_ALL_TOOLCHAINS))
 NDK_ALL_ABIS         := $(sort $(NDK_ALL_ABIS))
 NDK_ALL_ARCHS        := $(sort $(NDK_ALL_ARCHS))

 # Check that each ABI has a single architecture definition
 $(foreach _abi,$(strip $(NDK_ALL_ABIS)),\
   $(if $(filter-out 1,$(words $(NDK_ABI.$(_abi).arch))),\
     $(call __ndk_info,INTERNAL ERROR: The $(_abi) ABI should have exactly one architecture definitions. Found: '$(NDK_ABI.$(_abi).arch)')\
     $(call __ndk_error,Aborting...)\
   )\
 )

 # Allow the user to define NDK_TOOLCHAIN to a custom toolchain name.
 # This is normally used when the NDK release comes with several toolchains
 # for the same architecture (generally for backwards-compatibility).
 #
 NDK_TOOLCHAIN := $(strip $(NDK_TOOLCHAIN))
 ifdef NDK_TOOLCHAIN
     # check that the toolchain name is supported
     $(if $(filter-out $(NDK_ALL_TOOLCHAINS),$(NDK_TOOLCHAIN)),\
       $(call __ndk_info,NDK_TOOLCHAIN is defined to the unsupported value $(NDK_TOOLCHAIN)) \
       $(call __ndk_info,Please use one of the following values: $(NDK_ALL_TOOLCHAINS))\
       $(call __ndk_error,Aborting)\
     ,)
     $(call ndk_log, Using specific toolchain $(NDK_TOOLCHAIN))
 endif

 $(call ndk_log, This NDK supports the following target architectures and ABIS:)
 $(foreach arch,$(NDK_ALL_ARCHS),\
     $(call ndk_log, $(space)$(space)$(arch): $(NDK_ARCH.$(arch).abis))\
 )
 $(call ndk_log, This NDK supports the following toolchains and target ABIs:)
 $(foreach tc,$(NDK_ALL_TOOLCHAINS),\
     $(call ndk_log, $(space)$(space)$(tc):  $(NDK_TOOLCHAIN.$(tc).abis))\
 )
	# Copyright (C) 2009-2010 The Android Open Source Project
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.
	#

	# Initialization of the NDK build system. This file is included by
	# several build scripts.
	#

	# Disable GNU Make implicit rules

	# this turns off the suffix rules built into make
	.SUFFIXES:

	# this turns off the RCS / SCCS implicit rules of GNU Make
	% : RCS/%,v
	% : RCS/%
	% : %,v
	% : s.%
	% : SCCS/s.%

	# If a rule fails, delete $@.
	.DELETE_ON_ERROR:


	# Define NDK_LOG=1 in your environment to display log traces when
	# using the build scripts. See also the definition of ndk_log below.
	#
	NDK_LOG := $(strip $(NDK_LOG))
	ifeq ($(NDK_LOG),true)
	override NDK_LOG := 1
	endif

	# Check that we have at least GNU Make 3.81
	# We do this by detecting whether 'lastword' is supported
	#
	MAKE_TEST := $(lastword a b c d e f)
	ifneq ($(MAKE_TEST),f)
	$(error Android NDK: GNU Make version $(MAKE_VERSION) is too low (should be >= 3.81))
	endif
	ifeq ($(NDK_LOG),1)
	$(info Android NDK: GNU Make version $(MAKE_VERSION) detected)
	endif

	# NDK_ROOT must be defined and point to the root of the NDK installation
	NDK_ROOT := $(strip $(NDK_ROOT))
	ifndef NDK_ROOT
	$(error ERROR while including init.mk: NDK_ROOT must be defined !)
	endif
	ifneq ($(words $(NDK_ROOT)),1)
	$(info,The Android NDK installation path contains spaces: '$(NDK_ROOT)')
	$(error,Please fix the problem by reinstalling to a different location.)
	endif

	# ====================================================================
	#
	# Define a few useful variables and functions.
	# More stuff will follow in definitions.mk.
	#
	# ====================================================================

	# Used to output warnings and error from the library, it's possible to
	# disable any warnings or errors by overriding these definitions
	# manually or by setting NDK_NO_WARNINGS or NDK_NO_ERRORS

	__ndk_name := Android NDK
	__ndk_info = $(info $(__ndk_name): $1 $2 $3 $4 $5)
	__ndk_warning = $(warning $(__ndk_name): $1 $2 $3 $4 $5)
	__ndk_error = $(error $(__ndk_name): $1 $2 $3 $4 $5)

	ifdef NDK_NO_INFO
	__ndk_info :=
	endif
	ifdef NDK_NO_WARNINGS
	__ndk_warning :=
	endif
	ifdef NDK_NO_ERRORS
	__ndk_error :=
	endif

	# -----------------------------------------------------------------------------
	# Function : ndk_log
	# Arguments: 1: text to print when NDK_LOG is defined to 1
	# Returns : None
	# Usage : $(call ndk_log,<some text>)
	# -----------------------------------------------------------------------------
	ifeq ($(NDK_LOG),1)
	ndk_log = $(info $(__ndk_name): $1)
	else
	ndk_log :=
	endif

	# -----------------------------------------------------------------------------
	# Function : host-toolchain-path
	# Arguments: 1: NDK root
	# 2: Toolchain name
	# Returns : The parent path of all toolchains for this host. Note that
	# HOST_TAG64 == HOST_TAG for 32-bit systems.
	# -----------------------------------------------------------------------------
	ifeq ($(NDK_NEW_TOOLCHAINS_LAYOUT),true)
	host-toolchain-path = $1/$(HOST_TAG64)/$2
	else
	host-toolchain-path = $1/$2/prebuilt/$(HOST_TAG64)
	endif

	# -----------------------------------------------------------------------------
	# Function : get-gcclibs-path
	# Arguments: 1: NDK root
	# 2: Toolchain name (no version number)
	# Returns : Path to the given prebuilt gcclibs.
	# -----------------------------------------------------------------------------
	get-gcclibs-path = $1/gcclibs/$2

	# ====================================================================
	#
	# Host system auto-detection.
	#
	# ====================================================================

	#
	# Determine host system and architecture from the environment
	#
	HOST_OS := $(strip $(HOST_OS))
	ifndef HOST_OS
	# On all modern variants of Windows (including Cygwin and Wine)
	# the OS environment variable is defined to 'Windows_NT'
	#
	# The value of PROCESSOR_ARCHITECTURE will be x86 or AMD64
	#
	ifeq ($(OS),Windows_NT)
	HOST_OS := windows
	else
	# For other systems, use the `uname` output
	UNAME := $(shell uname -s)
	ifneq (,$(findstring Linux,$(UNAME)))
	HOST_OS := linux
	endif
	ifneq (,$(findstring Darwin,$(UNAME)))
	HOST_OS := darwin
	endif
	# We should not be there, but just in case !
	ifneq (,$(findstring CYGWIN,$(UNAME)))
	$(call __ndk_warning,Unsupported build environment CYGWIN.)
	HOST_OS := windows
	endif
	ifneq (,$(findstring MINGW64,$(UNAME)))
	$(call __ndk_warning,Unsupported build environment MSYS.)
	HOST_OS := windows
	endif
	ifeq ($(HOST_OS),)
	$(call __ndk_info,Unable to determine HOST_OS from uname -s: $(UNAME))
	$(call __ndk_info,Please define HOST_OS in your environment.)
	$(call __ndk_error,Aborting.)
	endif
	endif
	$(call ndk_log,Host OS was auto-detected: $(HOST_OS))
	else
	$(call ndk_log,Host OS from environment: $(HOST_OS))
	endif

	# For all systems, we will have HOST_OS_BASE defined as
	# $(HOST_OS), except on Cygwin where we will have:
	#
	# HOST_OS == cygwin
	# HOST_OS_BASE == windows
	#
	# Trying to detect that we're running from Cygwin is tricky
	# because we can't use $(OSTYPE): It's a Bash shell variable
	# that is not exported to sub-processes, and isn't defined by
	# other shells (for those with really weird setups).
	#
	# Instead, we assume that a program named /bin/uname.exe
	# that can be invoked and returns a valid value corresponds
	# to a Cygwin installation.
	#
	HOST_OS_BASE := $(HOST_OS)

	ifeq ($(HOST_OS),windows)
	ifneq (,$(strip $(wildcard /bin/uname.exe)))
	$(call ndk_log,Found /bin/uname.exe on Windows host, checking for Cygwin)
	# NOTE: The 2>NUL here is for the case where we're running inside the
	# native Windows shell. On cygwin, this will create an empty NUL file
	# that we're going to remove later (see below).
	UNAME := $(shell /bin/uname.exe -s 2>NUL)
	$(call ndk_log,uname -s returned: $(UNAME))
	ifneq (,$(filter CYGWIN%,$(UNAME)))
	$(call ndk_log,Cygwin detected: $(shell uname -a))
	HOST_OS := cygwin
	_ := $(shell rm -f NUL) # Cleaning up
	else
	ifneq (,$(filter MINGW32%,$(UNAME)))
	$(call ndk_log,MSys detected: $(shell uname -a))
	HOST_OS := cygwin
	else
	$(call ndk_log,Cygwin not detected!)
	endif
	endif
	endif
	endif

	ifneq ($(HOST_OS),$(HOST_OS_BASE))
	$(call ndk_log, Host operating system detected: $(HOST_OS), base OS: $(HOST_OS_BASE))
	else
	$(call ndk_log, Host operating system detected: $(HOST_OS))
	endif

	HOST_ARCH := $(strip $(HOST_ARCH))
	HOST_ARCH64 :=
	ifndef HOST_ARCH
	ifeq ($(HOST_OS_BASE),windows)
	# In the case that we're a 32-bit make (shouldn't be the case, but maybe
	# the user is using their own make binary rather than the NDK's), on a
	# 64-bit OS, PROCESSOR_ARCHITECTURE will be x86 but
	# PROCESSOR_ARCHITEW6432 will be AMD64. If PROCESSOR_ARCHITECTURE is x86
	# and PROCESSOR_ARCHITEW6432 is empty, this is a 32-bit OS.
	# https://blogs.msdn.microsoft.com/david.wang/2006/03/27/howto-detect-process-bitness/
	ifeq ($(PROCESSOR_ARCHITECTURE)$(PROCESSOR_ARCHITEW6432),x86)
	$(call __ndk_error,32-bit Windows is supported.)
	endif
	endif
	HOST_ARCH := x86
	HOST_ARCH64 := x86_64
	else
	$(call ndk_log,Host CPU from environment: $(HOST_ARCH))
	endif

	ifeq (,$(HOST_ARCH64))
	HOST_ARCH64 := $(HOST_ARCH)
	endif

	HOST_TAG := $(HOST_OS_BASE)-$(HOST_ARCH)
	HOST_TAG64 := $(HOST_OS_BASE)-$(HOST_ARCH64)

	# The directory separator used on this host
	HOST_DIRSEP := :
	ifeq ($(HOST_OS),windows)
	HOST_DIRSEP := ;
	endif

	# The host executable extension
	HOST_EXEEXT :=
	ifeq ($(HOST_OS),windows)
	HOST_EXEEXT := .exe
	endif

	ifeq ($(HOST_TAG),windows-x86)
	# If we are on Windows, we need to check that we are not running Cygwin 1.5,
	# which is deprecated and won't run our toolchain binaries properly.
	ifeq ($(HOST_OS),cygwin)
	# On cygwin, 'uname -r' returns something like 1.5.23(0.225/5/3)
	# We recognize 1.5. as the prefix to look for then.
	CYGWIN_VERSION := $(shell uname -r)
	ifneq ($(filter XX1.5.%,XX$(CYGWIN_VERSION)),)
	$(call __ndk_info,You seem to be running Cygwin 1.5, which is not supported.)
	$(call __ndk_info,Please upgrade to Cygwin 1.7 or higher.)
	$(call __ndk_error,Aborting.)
	endif
	endif

	# special-case the host-tag
	HOST_TAG := windows
	endif

	$(call ndk_log,HOST_TAG set to $(HOST_TAG))

	# Check for NDK-specific versions of our host tools
	HOST_TOOLS_ROOT := $(NDK_ROOT)/prebuilt/$(HOST_TAG64)
	HOST_PREBUILT := $(strip $(wildcard $(HOST_TOOLS_ROOT)/bin))
	HOST_MAKE := $(strip $(NDK_HOST_MAKE))
	HOST_PYTHON := $(strip $(NDK_HOST_PYTHON))
	TOOLCHAIN_ROOT := $(NDK_ROOT)/toolchains/llvm/prebuilt/$(HOST_TAG64)
	ifdef HOST_PREBUILT
	$(call ndk_log,Host tools prebuilt directory: $(HOST_PREBUILT))
	# The windows prebuilt binaries are for ndk-build.cmd
	# On cygwin, we must use the Cygwin version of these tools instead.
	ifneq ($(HOST_OS),cygwin)
	ifndef HOST_MAKE
	HOST_MAKE := $(wildcard $(HOST_PREBUILT)/make$(HOST_EXEEXT))
	endif
	ifndef HOST_PYTHON
	ifeq ($(HOST_OS),windows)
	HOST_PYTHON := $(wildcard $(TOOLCHAIN_ROOT)/python3/python$(HOST_EXEEXT))
	else
	HOST_PYTHON := $(wildcard $(TOOLCHAIN_ROOT)/python3/bin/python3$(HOST_EXEEXT))
	endif
	endif
	endif
	else
	$(call ndk_log,Host tools prebuilt directory not found, using system tools)
	endif
	ifndef HOST_PYTHON
	HOST_PYTHON := python
	endif

	HOST_ECHO := $(strip $(NDK_HOST_ECHO))
	ifdef HOST_PREBUILT
	ifndef HOST_ECHO
	# Special case, on Cygwin, always use the host echo, not our prebuilt one
	# which adds \r\n at the end of lines.
	ifneq ($(HOST_OS),cygwin)
	HOST_ECHO := $(strip $(wildcard $(HOST_PREBUILT)/echo$(HOST_EXEEXT)))
	endif
	endif
	endif
	ifndef HOST_ECHO
	HOST_ECHO := echo
	endif
	$(call ndk_log,Host 'echo' tool: $(HOST_ECHO))

	# Define HOST_ECHO_N to perform the equivalent of 'echo -n' on all platforms.
	ifeq ($(HOST_OS),windows)
	# Our custom toolbox echo binary supports -n.
	HOST_ECHO_N := $(HOST_ECHO) -n
	else
	# On Posix, just use bare printf.
	HOST_ECHO_N := printf %s
	endif
	$(call ndk_log,Host 'echo -n' tool: $(HOST_ECHO_N))

	HOST_CMP := $(strip $(NDK_HOST_CMP))
	ifdef HOST_PREBUILT
	ifndef HOST_CMP
	HOST_CMP := $(strip $(wildcard $(HOST_PREBUILT)/cmp$(HOST_EXEEXT)))
	endif
	endif
	ifndef HOST_CMP
	HOST_CMP := cmp
	endif
	$(call ndk_log,Host 'cmp' tool: $(HOST_CMP))

	# Location of python build helpers.
	BUILD_PY := $(NDK_ROOT)/build

	#
	# On Cygwin/MSys, define the 'cygwin-to-host-path' function here depending on the
	# environment. The rules are the following:
	#
	# 1/ If NDK_USE_CYGPATH=1 and cygpath does exist in your path, cygwin-to-host-path
	# calls "cygpath -m" for each host path. Since invoking 'cygpath -m' from GNU
	# Make for each source file is _very_ slow, this is only a backup plan in
	# case our automatic substitution function (described below) doesn't work.
	#
	# 2/ Generate a Make function that performs the mapping from cygwin/msys to host
	# paths through simple substitutions. It's really a series of nested patsubst
	# calls, that loo like:
	#
	# cygwin-to-host-path = $(patsubst /cygdrive/c/%,c:/%,\
	# $(patsusbt /cygdrive/d/%,d:/%, \
	# $1)
	# or in MSys:
	# cygwin-to-host-path = $(patsubst /c/%,c:/%,\
	# $(patsusbt /d/%,d:/%, \
	# $1)
	#
	# except that the actual definition is built from the list of mounted
	# drives as reported by "mount" and deals with drive letter cases (i.e.
	# '/cygdrive/c' and '/cygdrive/C')
	#
	ifeq ($(HOST_OS),cygwin)
	CYGPATH := $(strip $(HOST_CYGPATH))
	ifndef CYGPATH
	$(call ndk_log, Probing for 'cygpath' program)
	CYGPATH := $(strip $(shell which cygpath 2>/dev/null))
	ifndef CYGPATH
	$(call ndk_log, 'cygpath' was not found in your path)
	else
	$(call ndk_log, 'cygpath' found as: $(CYGPATH))
	endif
	endif

	ifeq ($(NDK_USE_CYGPATH),1)
	ifndef CYGPATH
	$(call __ndk_info,No cygpath)
	$(call __ndk_error,Aborting)
	endif
	$(call ndk_log, Forced usage of 'cygpath -m' through NDK_USE_CYGPATH=1)
	cygwin-to-host-path = $(strip $(shell $(CYGPATH) -m $1))
	else
	# Call a Python script to generate a Makefile function that approximates
	# cygpath.
	WINDOWS_HOST_PATH_FRAGMENT := $(shell mount \| $(HOST_PYTHON) $(BUILD_PY)/gen_cygpath.py)
	$(eval cygwin-to-host-path = $(WINDOWS_HOST_PATH_FRAGMENT))
	endif
	endif # HOST_OS == cygwin

	# The location of the build system files
	BUILD_SYSTEM := $(NDK_ROOT)/build/core

	# Include common definitions
	include $(BUILD_SYSTEM)/definitions.mk

	# ====================================================================
	#
	# Read all platform-specific configuration files.
	#
	# Each platform must be located in build/platforms/android-<apilevel>
	# where <apilevel> corresponds to an API level number, with:
	# 3 -> Android 1.5
	# 4 -> next platform release
	#
	# ====================================================================

	# ====================================================================
	#
	# Read all toolchain-specific configuration files.
	#
	# Each toolchain must have a corresponding config.mk file located
	# in build/toolchains/<name>/ that will be included here.
	#
	# Each one of these files should define the following variables:
	# TOOLCHAIN_NAME toolchain name (e.g. arm-linux-androideabi-4.9)
	# TOOLCHAIN_ABIS list of target ABIs supported by the toolchain.
	#
	# Then, it should include $(ADD_TOOLCHAIN) which will perform
	# book-keeping for the build system.
	#
	# ====================================================================

	# the build script to include in each toolchain config.mk
	ADD_TOOLCHAIN := $(BUILD_SYSTEM)/add-toolchain.mk

	# checkbuild.py generates these two files from the files in $NDK/meta.
	include $(BUILD_SYSTEM)/abis.mk
	include $(BUILD_SYSTEM)/platforms.mk

	NDK_KNOWN_DEVICE_ABIS := $(NDK_KNOWN_DEVICE_ABI64S) $(NDK_KNOWN_DEVICE_ABI32S)

	NDK_APP_ABI_ALL_EXPANDED := $(NDK_KNOWN_DEVICE_ABIS)
	NDK_APP_ABI_ALL32_EXPANDED := $(NDK_KNOWN_DEVICE_ABI32S)
	NDK_APP_ABI_ALL64_EXPANDED := $(NDK_KNOWN_DEVICE_ABI64S)

	NDK_MIN_PLATFORM := android-$(NDK_MIN_PLATFORM_LEVEL)
	NDK_MAX_PLATFORM := android-$(NDK_MAX_PLATFORM_LEVEL)

	$(call ndk_log,Found max platform level: $(NDK_MAX_PLATFORM_LEVEL))

	# the list of all toolchains in this NDK
	NDK_ALL_TOOLCHAINS :=
	NDK_ALL_ABIS :=
	NDK_ALL_ARCHS :=

	TOOLCHAIN_CONFIGS := $(wildcard $(NDK_ROOT)/build/core/toolchains/*/config.mk)
	$(foreach _config_mk,$(TOOLCHAIN_CONFIGS),\
	$(eval include $(BUILD_SYSTEM)/add-toolchain.mk)\
	)

	NDK_ALL_TOOLCHAINS := $(sort $(NDK_ALL_TOOLCHAINS))
	NDK_ALL_ABIS := $(sort $(NDK_ALL_ABIS))
	NDK_ALL_ARCHS := $(sort $(NDK_ALL_ARCHS))

	# Check that each ABI has a single architecture definition
	$(foreach _abi,$(strip $(NDK_ALL_ABIS)),\
	$(if $(filter-out 1,$(words $(NDK_ABI.$(_abi).arch))),\
	$(call __ndk_info,INTERNAL ERROR: The $(_abi) ABI should have exactly one architecture definitions. Found: '$(NDK_ABI.$(_abi).arch)')\
	$(call __ndk_error,Aborting...)\
	)\
	)

	# Allow the user to define NDK_TOOLCHAIN to a custom toolchain name.
	# This is normally used when the NDK release comes with several toolchains
	# for the same architecture (generally for backwards-compatibility).
	#
	NDK_TOOLCHAIN := $(strip $(NDK_TOOLCHAIN))
	ifdef NDK_TOOLCHAIN
	# check that the toolchain name is supported
	$(if $(filter-out $(NDK_ALL_TOOLCHAINS),$(NDK_TOOLCHAIN)),\
	$(call __ndk_info,NDK_TOOLCHAIN is defined to the unsupported value $(NDK_TOOLCHAIN)) \
	$(call __ndk_info,Please use one of the following values: $(NDK_ALL_TOOLCHAINS))\
	$(call __ndk_error,Aborting)\
	,)
	$(call ndk_log, Using specific toolchain $(NDK_TOOLCHAIN))
	endif

	$(call ndk_log, This NDK supports the following target architectures and ABIS:)
	$(foreach arch,$(NDK_ALL_ARCHS),\
	$(call ndk_log, $(space)$(space)$(arch): $(NDK_ARCH.$(arch).abis))\
	)
	$(call ndk_log, This NDK supports the following toolchains and target ABIs:)
	$(foreach tc,$(NDK_ALL_TOOLCHAINS),\
	$(call ndk_log, $(space)$(space)$(tc): $(NDK_TOOLCHAIN.$(tc).abis))\
	)