Android 编译过程分析（1）
以Google Nexus 5 为例：
1. 编译文件
系统编译文件存放位置: android4.4.2_r1/build/core/
产品编译文件存放位置：android4.4.2_r1/build/target/product/
Device 编译文件存放位置：android4.4.2_r1/device/lge/hammerhead/
Android 编译初始文件位置： android4.4.2_r1/Makefile
2. 设置环境变量
$cd android4.4.2_r1
$. build/envsetup.sh
##################################################################
# #
# Read me before you modify this code #
# #
# This function sets ANDROID_BUILD_PATHS to what it is adding #
# to PATH, and the next time it is run, it removes that from #
# PATH. This is required so lunch can be run more than once #
# and still have working paths. #
# #
##################################################################
lunch 命令： 选择产品及配置编译环境变量
function lunch()
{
local answer
if [ "$1" ] ; then
answer=$1
else
print_lunch_menu
echo -n "Which would you like? [aosp_arm-eng] "
read answer
fi
local selection=
if [ -z "$answer" ]
then
selection=aosp_arm-eng
elif (echo -n $answer | grep -q -e "^[0-9][0-9]*$")
then
if [ $answer -le ${#LUNCH_MENU_CHOICES[@]} ]
then
selection=${LUNCH_MENU_CHOICES[$(($answer-1))]}
fi
elif (echo -n $answer | grep -q -e "^[^\-][^\-]*-[^\-][^\-]*$")
then
selection=$answer
fi
if [ -z "$selection" ]
then
echo
echo "Invalid lunch combo: $answer"
return 1
fi
export TARGET_BUILD_APPS=
local product=$(echo -n $selection | sed -e "s/-.*$//")
check_product $product
if [ $? -ne 0 ]
then
echo
echo "** Don't have a product spec for: '$product'"
echo "** Do you have the right repo manifest?"
product=
fi
local variant=$(echo -n $selection | sed -e "s/^[^\-]*-//")
check_variant $variant
if [ $? -ne 0 ]
then
echo
echo "** Invalid variant: '$variant'"
echo "** Must be one of ${VARIANT_CHOICES[@]}"
variant=
fi
if [ -z "$product" -o -z "$variant" ]
then
echo
return 1
fi
export TARGET_PRODUCT=$product
export TARGET_BUILD_VARIANT=$variant
export TARGET_BUILD_TYPE=release
echo
set_stuff_for_environment
printconfig
}
2. 编译文件之间的关系：
android4.4.2_r1/Makefile==> build/core/main.mk
in main.mk
定义系统编译文件目录; BUILD_SYSTEM := $(TOPDIR)build/core
包含了help.mk 给出了make 命令后可以跟的参数，如下：
@echo
@echo "Common make targets:"
@echo "----------------------------------------------------------------------------------"
@echo "droid Default target"
@echo "clean (aka clobber) equivalent to rm -rf out/"
@echo "snod Quickly rebuild the system image from built packages"
@echo "offline-sdk-docs Generate the HTML for the developer SDK docs"
@echo "doc-comment-check-docs Check HTML doc links & validity, without generating HTML"
@echo "libandroid_runtime All the JNI framework stuff"
@echo "framework All the java framework stuff"
@echo "services The system server (Java) and friends"
@echo "help You're reading it right now"
包含了config.mk:
# This is included by the top-level Makefile.
# It sets up standard variables based on the
# current configuration and platform, which
# are not specific to what is being built.
# ###############################################################
# Build system internal files
# ###############################################################
# The 'showcommands' goal says to show the full command
# lines being executed, instead of a short message about
# the kind of operation being done.
# The default key if not set as LOCAL_CERTIFICATE
ifdef PRODUCT_DEFAULT_DEV_CERTIFICATE
DEFAULT_SYSTEM_DEV_CERTIFICATE := $(PRODUCT_DEFAULT_DEV_CERTIFICATE)
else
DEFAULT_SYSTEM_DEV_CERTIFICATE := build/target/product/security/testkey
endif
config.mk 最后调用dumpvar.mk 输出配置结果
HOST_OS_EXTRA:=$(shell python -c "import platform; print(platform.platform())")
$(info ============================================)
$(info PLATFORM_VERSION_CODENAME=$(PLATFORM_VERSION_CODENAME))
$(info PLATFORM_VERSION=$(PLATFORM_VERSION))
$(info TARGET_PRODUCT=$(TARGET_PRODUCT))
$(info TARGET_BUILD_VARIANT=$(TARGET_BUILD_VARIANT))
$(info TARGET_BUILD_TYPE=$(TARGET_BUILD_TYPE))
$(info TARGET_BUILD_APPS=$(TARGET_BUILD_APPS))
$(info TARGET_ARCH=$(TARGET_ARCH))
$(info TARGET_ARCH_VARIANT=$(TARGET_ARCH_VARIANT))
$(info TARGET_CPU_VARIANT=$(TARGET_CPU_VARIANT))
$(info HOST_ARCH=$(HOST_ARCH))
$(info HOST_OS=$(HOST_OS))
$(info HOST_OS_EXTRA=$(HOST_OS_EXTRA))
$(info HOST_BUILD_TYPE=$(HOST_BUILD_TYPE))
$(info BUILD_ID=$(BUILD_ID))
$(info OUT_DIR=$(OUT_DIR))
$(info ============================================)
接下来会检查当前操作系统、Java、等编译工具的检查
检查所有Android.mk 文件
#
# Typical build; include any Android.mk files we can find.
#
将文件打包
.PHONY: ramdisk
ramdisk: $(INSTALLED_RAMDISK_TARGET)
.PHONY: factory_ramdisk
factory_ramdisk: $(INSTALLED_FACTORY_RAMDISK_TARGET)
.PHONY: factory_bundle
factory_bundle: $(INSTALLED_FACTORY_BUNDLE_TARGET)
.PHONY: systemtarball
systemtarball: $(INSTALLED_SYSTEMTARBALL_TARGET)
.PHONY: boottarball
boottarball: $(INSTALLED_BOOTTARBALL_TARGET)
.PHONY: userdataimage
userdataimage: $(INSTALLED_USERDATAIMAGE_TARGET)
ifneq (,$(filter userdataimage, $(MAKECMDGOALS)))
$(call dist-for-goals, userdataimage, $(BUILT_USERDATAIMAGE_TARGET))
endif
.PHONY: userdatatarball
userdatatarball: $(INSTALLED_USERDATATARBALL_TARGET)
.PHONY: cacheimage
cacheimage: $(INSTALLED_CACHEIMAGE_TARGET)
.PHONY: vendorimage
vendorimage: $(INSTALLED_VENDORIMAGE_TARGET)
.PHONY: bootimage
bootimage: $(INSTALLED_BOOTIMAGE_TARGET)
将打包文件编译为ROM 文件
# Build files and then package it into the rom formats
.PHONY: droidcore
droidcore: files \
systemimage \
$(INSTALLED_BOOTIMAGE_TARGET) \
$(INSTALLED_RECOVERYIMAGE_TARGET) \
$(INSTALLED_USERDATAIMAGE_TARGET) \
$(INSTALLED_CACHEIMAGE_TARGET) \
$(INSTALLED_VENDORIMAGE_TARGET) \
$(INSTALLED_FILES_FILE)
把打包文件及ROM 文件拷贝到安装目录
.PHONY: lintall