《Android系统学习》第四章：分析Android系统编译过程

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以下是加载命令和选择平台编译选项，也就是设置编译环境变量。

一、/build/envsetup.sh之初始化

......add_lunch_combo full-engadd_lunch_combo full_x86-engadd_lunch_combo vbox_x86-eng#模拟器......# Execute the contents of any vendorsetup.sh files we can find.for f in `/bin/ls vendor/*/vendorsetup.sh vendor/*/*/vendorsetup.sh device/*/*/vendorsetup.sh 2> /dev/null`do    echo "including $f"    . $fdoneunset f#遍历/vendor/*/vendorsetup.sh、/vendor/*/*/vendorsetup.sh和/device/*/*/vendorsetup.sh文件；#eg：/device/tank/tanka3/vendorsetup.sh  add_lunch_combo full_tanka3-userdebug

二、/build/envsetup.sh之add_lunch_combo命令

function add_lunch_combo(){  local new_combo=$1  local c  for c in ${LUNCH_MENU_CHOICES[@]} ; do    if [ "$new_combo" = "$c" ] ; then      return    fi  done  LUNCH_MENU_CHOICES=(${LUNCH_MENU_CHOICES[@]} $new_combo)}

三、/build/envsetup.sh之lunch命令

function lunch(){  ......  check_product $product#从上处剥离$product == full_tanka3  ......}function check_product(){  ......  CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core \        TARGET_PRODUCT=$1 \        TARGET_BUILD_VARIANT= \        TARGET_BUILD_TYPE= \        TARGET_BUILD_APPS= \        get_build_var TARGET_DEVICE > /dev/null  ......}function get_build_var(){  ......  CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core \      make --no-print-directory -C "$T" -f build/core/config.mk dumpvar-$1}

四、/build/core/config.mk

......include $(BUILD_SYSTEM)/envsetup.mk......board_config_mk := \        $(strip $(wildcard \                $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk \                device/*/$(TARGET_DEVICE)/BoardConfig.mk \                vendor/*/$(TARGET_DEVICE)/BoardConfig.mk \        ))#查找/device/tank/tanka3/BoardConfig.mk #模拟器查找/build/target/board/emulator/BoardConfig.mk......

五、/build/core/envsetup.mk

......include $(BUILD_SYSTEM)/product_config.mk......ifeq ($(TARGET_ARCH),)TARGET_ARCH := armendif......

六、/build/core/product_config.mk

......include $(BUILD_SYSTEM)/product.mk......

七、/build/core/product.mk

......define _find-android-products-files$(shell test -d device && find device -maxdepth 6 -name AndroidProducts.mk) \  $(shell test -d vendor && find vendor -maxdepth 6 -name AndroidProducts.mk) \  $(SRC_TARGET_DIR)/product/AndroidProducts.mkendef......#查找/device/tank/tanka3/AndroidProducts.mk#模拟器查找/build/target/product/AndroidProducts.mk

以上执行完后，后设置如下环境变量：

PLATFORM_VERSION_CODENAME=RELPLATFORM_VERSION=4.0.3TARGET_PRODUCT=full_tanka3TARGET_BUILD_VARIANT=userdebugTARGET_BUILD_TYPE=releaseTARGET_BUILD_APPS=TARGET_ARCH=armTARGET_ARCH_VARIANT=armv7-a-neonHOST_ARCH=x86HOST_OS=linuxHOST_BUILD_TYPE=releaseBUILD_ID=IML74K

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以下是真正开始编译：

一、/Makefile

include build/core/main.mk

二、/build/core/main.mk

......include $(BUILD_SYSTEM)/config.mk......

三、/build/core/config.mk

后边与上面《四-七》一一对应。
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定制自己厂商目录：

一、mkdir /device/tank

二、mkdir /device/tank/tanka3

三、cd /device/tank/tanka3

  touch vendorsetup.sh  touch BoardConfig.mk  touch AndroidProducts.mk  //包含full_tanka3.mk  touch full_tanka3.mk  //包含device.mk  touch device.mk

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补充：

在BoardConfig.mk文件中可以设置对象CPU架构、类型以及交叉编译工具链路径，如：

  TARGET_ARCH=mips#架构，若不设置、由/build/core/envsetup.mk默认设置arm  TARGET_ARCH_VARIANT := mips32r2-fp#核类型，若不设置、由/build/core/combo/TARGET_linux-arm.mk默认设置armv5te  TARGET_ARCH_VERSION=mips32  TARGET_TOOLS_PREFIX :=#交叉编译工具链，若不设置、由build/core/combo/TARGET_linux-arm.mk默认设置#TARGET_TOOLS_PREFIX := prebuilt/$(HOST_PREBUILT_TAG)/toolchain/arm-eabi-4.4.3/bin/arm-

其他主要文件或目录：

build/core/combo/TARGET_linux-arm.mk  

//决定arm架构的具体类型（如果TARGET_ARCH_VARIANT未定义）以及交叉编译工具链路径

......ifeq ($(strip $(TARGET_ARCH_VARIANT)),)TARGET_ARCH_VARIANT := armv5teendif......ifeq ($(strip $(TARGET_TOOLS_PREFIX)),)TARGET_TOOLS_PREFIX := prebuilt/$(HOST_PREBUILT_TAG)/toolchain/arm-eabi-4.4.3/bin/arm-eabi-endif......

build/core/combo/arch/arm/

bionic/libc/arch-arm/

bionic/libm/Android.mk

bionic/linker/Android.mk

arm架构交叉编译工具链路径：

prebuilt/ndk/android-ndk-r4/platforms/android-8/arch-arm/