ifeq ($(SDK_ONLY),true)

# ----- SDK for Windows ------

# These configure the build targets that are available for the SDK under Cygwin.

# The first section defines all the C/C++ tools that can be compiled under Cygwin,

# the second section defines all the Java ones (assuming javac is available.)

#(23)确定subdirs，这里包含的文件目录下的文件最终被编译，其中第一部分决定了一些C/C++工具被编译的子目录。

#第二部分为使用java编译器编译的目录。

#这是第一部分。

subdirs := /

prebuilt /

build/libs/host /

build/tools/zipalign /

dalvik/dexdump /

dalvik/libdex /

dalvik/tools/dmtracedump /

dalvik/tools/hprof-conv /

development/tools/line_endings /

development/tools/etc1tool /

sdk/emulator/mksdcard /

sdk/sdklauncher /

development/host /

external/expat /

external/libpng /

external/qemu /

external/sqlite/dist /

external/zlib /

frameworks/base/libs/utils /

frameworks/base/tools/aapt /

frameworks/base/tools/aidl /

frameworks/base/opengl/libs /

system/core/adb /

system/core/fastboot /

system/core/libcutils /

system/core/liblog /

system/core/libzipfile

# The following can only be built if "javac" is available.

# This check is used when building parts of the SDK under Cygwin.

#(24)调用which命令查看在环境变量中是否有javac这个命令，若是有的话，说明java编译器是已经安装的了，

#那么就包含这些目录，否则不包含这些目录，并抛出一个警告。

ifneq (,$(shell which javac 2>/dev/null))

$(warning sdk-only: javac available.)

#这是第二部分。

subdirs += /

build/tools/signapk /

dalvik/dx /

dalvik/libcore /

sdk/archquery /

sdk/androidprefs /

sdk/apkbuilder /

sdk/jarutils /

sdk/layoutlib_api /

sdk/layoutlib_utils /

sdk/ninepatch /

sdk/sdkstats /

sdk/sdkmanager /

sdk/layoutopt /

development/apps /

development/tools/mkstubs /

frameworks/base/tools/layoutlib /

external/googleclient /

packages

else

$(warning sdk-only: javac not available.)

endif

#(25)若当前HOST不是linux，那么还要要添加build/tools/acp这个目录。

# Exclude tools/acp when cross-compiling windows under linux

ifeq ($(findstring Linux,$(UNAME)),)

subdirs += build/tools/acp

endif

#(26)若SDK_ONLY不为真，且BUILD_TINY_ANDROID为真，那么添加一些文件，编译一个最小的系统.

else # !SDK_ONLY

ifeq ($(BUILD_TINY_ANDROID), true)

# TINY_ANDROID is a super-minimal build configuration, handy for board

# bringup and very low level debugging

subdirs := /

bionic /

system/core /

build/libs /

build/target /

build/tools/acp /

build/tools/apriori /

build/tools/kcm /

build/tools/soslim /

external/elfcopy /

external/elfutils /

external/yaffs2 /

external/zlib

else # !BUILD_TINY_ANDROID

#(27)若上面的两个条件(SDK_ONLY为真，BUILD_TINY_ANDROID为真)都不成了，那么就要包含$(TOP)下面

#的所有android.mk文件了。这才是最典型的编译.

#

# Typical build; include any Android.mk files we can find.

#

subdirs := $(TOP)

FULL_BUILD := true

endif # !BUILD_TINY_ANDROID

endif # !SDK_ONLY

ifneq ($(ONE_SHOT_MAKEFILE),)

# We've probably been invoked by the "mm" shell function

# with a subdirectory's makefile.

include $(ONE_SHOT_MAKEFILE)

# Change CUSTOM_MODULES to include only modules that were

# defined by this makefile; this will install all of those

# modules as a side-effect. Do this after including ONE_SHOT_MAKEFILE

# so that the modules will be installed in the same place they

# would have been with a normal make.

#(28)设定CUSTOM_MODULES，在后面会涉及到。非常重要。

CUSTOM_MODULES := $(sort $(call get-tagged-modules,$(ALL_MODULE_TAGS),))

FULL_BUILD :=

# Stub out the notice targets, which probably aren't defined

# when using ONE_SHOT_MAKEFILE.

NOTICE-HOST-%: ;

NOTICE-TARGET-%: ;

else # ONE_SHOT_MAKEFILE

#

# Include all of the makefiles in the system

#

# Can't use first-makefiles-under here because

# --mindepth=2 makes the prunes not work.

#(29)在这里调用findleaves.py查找在subdirs的包含的子目录下所有的Android.mk文件。

subdir_makefiles := /

$(shell build/tools/findleaves.py --prune=out --prune=.repo --prune=.git $(subdirs) Android.mk)

include $(subdir_makefiles)

endif # ONE_SHOT_MAKEFILE

# -------------------------------------------------------------------

# All module makefiles have been included at this point.

# -------------------------------------------------------------------

# -------------------------------------------------------------------

# Include any makefiles that must happen after the module makefiles

# have been included.

# TODO: have these files register themselves via a global var rather

# than hard-coding the list here.

ifdef FULL_BUILD

# Only include this during a full build, otherwise we can't be

# guaranteed that any policies were included.

-include frameworks/policies/base/PolicyConfig.mk

endif

# -------------------------------------------------------------------

# Fix up CUSTOM_MODULES to refer to installed files rather than

# just bare module names. Leave unknown modules alone in case

# they're actually full paths to a particular file.

#(30)提取用户定义的定义的模块，用户定义的模块，不一定在系统的所有模块中有定义，这里做了分类

#分为: known_custom_modules:用户定义了，并且在系统中有定义。

# unknown_custom_modules:用户没有定义，但系统系统中有定义。

known_custom_modules := $(filter $(ALL_MODULES),$(CUSTOM_MODULES))

unknown_custom_modules := $(filter-out $(ALL_MODULES),$(CUSTOM_MODULES))

CUSTOM_MODULES := /

$(call module-installed-files,$(known_custom_modules)) /

$(unknown_custom_modules)

# -------------------------------------------------------------------

# Define dependencies for modules that require other modules.

# This can only happen now, after we've read in all module makefiles.

#

# TODO: deal with the fact that a bare module name isn't

# unambiguous enough. Maybe declare short targets like

# APPS:Quake or HOST:SHARED_LIBRARIES:libutils.

# BUG: the system p_w_picpath won't know to depend on modules that are

# brought in as requirements of other modules.

define add-required-deps

#(31)这里调用了module-installed-files和add-required-deps函数，设定各个模块对各种库的依赖

$(1): $(2)

endef

$(foreach m,$(ALL_MODULES), /

$(eval r := $(ALL_MODULES.$(m).REQUIRED)) /

$(if $(r), /

$(eval r := $(call module-installed-files,$(r))) /

$(eval $(call add-required-deps,$(ALL_MODULES.$(m).INSTALLED),$(r))) /

) /

)

m :=

r :=

add-required-deps :=

# -------------------------------------------------------------------

# Figure out our module sets.

# Of the modules defined by the component makefiles,

# determine what we actually want to build.

# If a module has the "restricted" tag on it, it

# poisons the rest of the tags and shouldn't appear

# on any list.

#(32)设定Default_MODULES;

Default_MODULES := $(sort $(ALL_DEFAULT_INSTALLED_MODULES) /

$(CUSTOM_MODULES))

# TODO: Remove the 3 places in the tree that use

# ALL_DEFAULT_INSTALLED_MODULES and get rid of it from this list.

ifdef FULL_BUILD

# The base list of modules to build for this product is specified

# by the appropriate product definition file, which was included

# by product_config.make.

#

#(33)设定user_PACKAGES获取这个product的所有的modules 的list，这份list定义的module选择定义在

# product_config.mk这个文件以及这个文件包含的子*.mk文件中。

user_PACKAGES := $(call module-installed-files, /

$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_PACKAGES))

ifeq (0,1)

$(info user packages for $(TARGET_DEVICE) ($(INTERNAL_PRODUCT)):)

$(foreach p,$(user_PACKAGES),$(info : $(p)))

$(error done)

endif

else

# We're not doing a full build, and are probably only including

# a subset of the module makefiles. Don't try to build any modules

# requested by the product, because we probably won't have rules

# to build them.

user_PACKAGES :=

endif

#(34)模块设定:引擎类模块eng_MODULES，应用类模块user_MODULES,测试模块test_MODULES,调试模块debug_MOUDLE

# Use tags to get the non-APPS user modules. Use the product

# definition files to get the APPS user modules.

user_MODULES := $(sort $(call get-tagged-modules,user,_class@APPS restricted))

user_MODULES := $(user_MODULES) $(user_PACKAGES)

eng_MODULES := $(sort $(call get-tagged-modules,eng,restricted))

debug_MODULES := $(sort $(call get-tagged-modules,debug,restricted))

tests_MODULES := $(sort $(call get-tagged-modules,tests,restricted))

ifeq ($(strip $(tags_to_install)),)

$(error ASSERTION FAILED: tags_to_install should not be empty)

endif

#(35)从tags_to_install获取要安装的模块

#获取关系如下:tags_to_install

modules_to_install := $(sort $(Default_MODULES) /

$(foreach tag,$(tags_to_install),$($(tag)_MODULES)))

# Some packages may override others using LOCAL_OVERRIDES_PACKAGES.

# Filter out (do not install) any overridden packages.

overridden_packages := $(call get-package-overrides,$(modules_to_install))

ifdef overridden_packages

# old_modules_to_install := $(modules_to_install)

modules_to_install := /

$(filter-out $(foreach p,$(overridden_packages),$(p) %/$(p).apk), /

$(modules_to_install))

endif

#$(error filtered out

# $(filter-out $(modules_to_install),$(old_modules_to_install)))

# Don't include any GNU targets in the SDK. It's ok (and necessary)

# to build the host tools, but nothing that's going to be installed

# on the target (including static libraries).

#(36)剔除目标里包含的gnu里的tools，这是sdk里包含的工具类模块，是不能安装在目标里的。

ifdef is_sdk_build

target_gnu_MODULES := /

$(filter /

$(TARGET_OUT_INTERMEDIATES)/% /

$(TARGET_OUT)/% /

$(TARGET_OUT_DATA)/%, /

$(sort $(call get-tagged-modules,gnu)))

$(info Removing from sdk:)$(foreach d,$(target_gnu_MODULES),$(info : $(d)))

modules_to_install := /

$(filter-out $(target_gnu_MODULES),$(modules_to_install))

endif

# build/core/Makefile contains extra stuff that we don't want to pollute this

# top-level makefile with. It expects that ALL_DEFAULT_INSTALLED_MODULES

# contains everything that's built during the current make, but it also further

# extends ALL_DEFAULT_INSTALLED_MODULES.

#(37)对ALL_DEFAULT_INSTALLED_MODULES 的处理

ALL_DEFAULT_INSTALLED_MODULES := $(modules_to_install)

include $(BUILD_SYSTEM)/Makefile

modules_to_install := $(sort $(ALL_DEFAULT_INSTALLED_MODULES))

ALL_DEFAULT_INSTALLED_MODULES :=

endif # dont_bother

# These are additional goals that we build, in order to make sure that there

# is as little code as possible in the tree that doesn't build.

#(38)确保我们定义我们构建的模块是没有冗余的。

modules_to_check := $(foreach m,$(ALL_MODULES),$(ALL_MODULES.$(m).CHECKED))

# If you would like to build all goals, and not skip any intermediate

# steps, you can pass the "all" modifier goal on the commandline.

ifneq ($(filter all,$(MAKECMDGOALS)),)

modules_to_check += $(foreach m,$(ALL_MODULES),$(ALL_MODULES.$(m).BUILT))

endif

# for easier debugging

modules_to_check := $(sort $(modules_to_check))

#$(error modules_to_check $(modules_to_check))

# -------------------------------------------------------------------

# This is used to to get the ordering right, you can also use these,

# but they're considered undocumented, so don't complain if their

# behavior changes.

.PHONY: prebuilt

prebuilt: $(ALL_PREBUILT)

# An internal target that depends on all copied headers

# (see copy_headers.make). Other targets that need the

# headers to be copied first can depend on this target.

.PHONY: all_copied_headers

all_copied_headers: ;

$(ALL_C_CPP_ETC_OBJECTS): | all_copied_headers

#(39)files这个目标在这里是一个非常大的目标，包括moudules_to_install,modules_to_check,prebuilt等等

#前面所做的就是为这几个目标的正确生成。关系如下:droid依赖于droidcore,而droidcore依赖于files,如下，

#就是这几项的依赖的关系控制着整个项目的编译流程。

# All the droid stuff, in directories

.PHONY: files

files: prebuilt /

$(modules_to_install) /

$(modules_to_check) /

$(INSTALLED_ANDROID_INFO_TXT_TARGET)

# -------------------------------------------------------------------

.PHONY: checkbuild

checkbuild: $(modules_to_check)

.PHONY: ramdisk

ramdisk: $(INSTALLED_RAMDISK_TARGET)

.PHONY: systemtarball

systemtarball: $(INSTALLED_SYSTEMTARBALL_TARGET)

.PHONY: userdatap_w_picpath

userdatap_w_picpath: $(INSTALLED_USERDATAIMAGE_TARGET)

.PHONY: userdatatarball

userdatatarball: $(INSTALLED_USERDATATARBALL_TARGET)

.PHONY: bootp_w_picpath

bootp_w_picpath: $(INSTALLED_BOOTIMAGE_TARGET)

ifeq ($(BUILD_TINY_ANDROID), true)

INSTALLED_RECOVERYIMAGE_TARGET :=

endif

#(40)一下是整改项目的build动作，如果要把整个编译过程分成：配置和编译两部分的话，

#上面的所有的都是配置过程，下面的为编译过程。

#这里确定好要生成的子目标。

# Build files and then package it into the rom formats

.PHONY: droidcore

droidcore: files /

systemp_w_picpath /

$(INSTALLED_BOOTIMAGE_TARGET) /

$(INSTALLED_RECOVERYIMAGE_TARGET) /

$(INSTALLED_USERDATAIMAGE_TARGET) /

$(INSTALLED_FILES_FILE)

# The actual files built by the droidcore target changes depending

# on the build variant.

#这里开始编译。

.PHONY: droid tests

droid tests: droidcore

$(call dist-for-goals, droid, /

$(INTERNAL_UPDATE_PACKAGE_TARGET) /

$(INTERNAL_OTA_PACKAGE_TARGET) /

$(SYMBOLS_ZIP) /

$(APPS_ZIP) /

$(INTERNAL_EMULATOR_PACKAGE_TARGET) /

$(PACKAGE_STATS_FILE) /

$(INSTALLED_FILES_FILE) /

$(INSTALLED_BUILD_PROP_TARGET) /

$(BUILT_TARGET_FILES_PACKAGE) /

)

# Tests are installed in userdata.img. If we're building the tests

# variant, copy it for "make tests dist". Also copy a zip of the

# contents of userdata.img, so that people can easily extract a

# single .apk.

ifeq ($(TARGET_BUILD_VARIANT),tests)

$(call dist-for-goals, droid, /

$(INSTALLED_USERDATAIMAGE_TARGET) /

$(BUILT_TESTS_ZIP_PACKAGE) /

)

endif

.PHONY: docs

docs: $(ALL_DOCS)

.PHONY: sdk

ALL_SDK_TARGETS := $(INTERNAL_SDK_TARGET)

sdk: $(ALL_SDK_TARGETS)

$(call dist-for-goals,sdk,$(ALL_SDK_TARGETS))

.PHONY: findbugs

findbugs: $(INTERNAL_FINDBUGS_HTML_TARGET) $(INTERNAL_FINDBUGS_XML_TARGET)

.PHONY: clean

dirs_to_clean := /

$(PRODUCT_OUT) /

$(TARGET_COMMON_OUT_ROOT) /

$(HOST_OUT) /

$(HOST_COMMON_OUT_ROOT)

clean:

@for dir in $(dirs_to_clean) ; do /

echo "Cleaning $$dir..."; /

rm -rf $$dir; /

done

@echo "Clean."; /

.PHONY: clobber

clobber:

@rm -rf $(OUT_DIR)

@echo "Entire build directory removed."

# The rules for dataclean and installclean are defined in cleanbuild.mk.

#xxx scrape this from ALL_MODULE_NAME_TAGS

.PHONY: modules

modules:

@echo "Available sub-modules:"

@echo "$(call module-names-for-tag-list,$(ALL_MODULE_TAGS))" | /

sed -e 's/ *//n/g' | sort -u | $(COLUMN)

.PHONY: showcommands

showcommands:

@echo >/dev/null