Android系統編譯前的準備工作，我個人認爲由如下三個步驟完成。接下來，我就逐一分析每一步驟都幹了什麼事情。
1、安裝jdk、設置環境變量JAVA_HOME。
2、source build/envsetup.sh
3、lunch <product_name>-<build_variant>
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博文中出現的get_abs_build_var() 和 get_build_var()請移步到
這裏
1、設置JAVA_HMOE環境變量
export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64該shell腳本實現了許多有用的shell函數，可通過執行hmm命令查看（hmm是envsetup.sh實現的第一個shell函數）。
下面是hmm命令顯示的一部分：
Invoke ". build/envsetup.sh" from your shell to add the following functions to your environment:
- lunch: lunch <product_name>-<build_variant>
- tapas: tapas [<App1> <App2> ...] [arm|x86|mips|armv5|arm64|x86_64|mips64] [eng|userdebug|user]
- croot: Changes directory to the top of the tree.
- m: Makes from the top of the tree.
- mm: Builds all of the modules in the current directory, but not their dependencies.
- mmm: Builds all of the modules in the supplied directories, but not their dependencies.
To limit the modules being built use the syntax: mmm dir/:target1,target2.
- mma: Builds all of the modules in the current directory, and their dependencies.
- mmma: Builds all of the modules in the supplied directories, and their dependencies.
- cgrep: Greps on all local C/C++ files.
- ggrep: Greps on all local Gradle files.
- jgrep: Greps on all local Java files.
- resgrep: Greps on all local res/*.xml files.
- sgrep: Greps on all local source files.
- godir: Go to the directory containing a file.除了上面實現的shell函數，envsetup.sh還把device和vendor目錄下的所有vendorsetup.sh腳本包含進來了。最後，還調用shell函數addcompletions。
if [ "x$SHELL" != "x/bin/bash" ]; then
case `ps -o command -p $$` in # $$屬於Special Shell Variables,表示Process ID of shell
*bash*)
;;
*)
echo "WARNING: Only bash is supported, use of other shell would lead to erroneous results"
;;
esac
fi
# Execute the contents of any vendorsetup.sh files we can find.
for f in `test -d device && find -L device -maxdepth 4 -name 'vendorsetup.sh' 2> /dev/null` \
`test -d vendor && find -L vendor -maxdepth 4 -name 'vendorsetup.sh' 2> /dev/null`
do
echo "including $f"
. $f # source找到的所有vendorsetup.sh文件
done
unset f
addcompletions # 檢查bash版本，並source sdk/bash_completion目錄下的所有[a-z]*.bash文件vendorsetup.sh的內容大多數是調用add_lunch_combo函數添加<product_name>-<build_variant>格式的lunch選項（也可以實現一些shell functions）。如：
add_lunch_combo aosp_flounder-userdebug接下來，看一下add_lunch_combo函數的實現，File：build/envsetup.sh。
# Clear this variable. It will be built up again when the vendorsetup.sh
# files are included at the end of this file.
unset LUNCH_MENU_CHOICES
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[@]} $new_combo) # vendorsetup.sh中添加的combo選項都保存在數組LUNCH_MENU_CHOICES中
}function addcompletions()
{
local T dir f
# Keep us from trying to run in something that isn't bash.
if [ -z "${BASH_VERSION}" ]; then
return
fi
# Keep us from trying to run in bash that's too old.
if [ ${BASH_VERSINFO[0]} -lt 3 ]; then
return
fi
dir="sdk/bash_completion"
if [ -d ${dir} ]; then
for f in `/bin/ls ${dir}/[a-z]*.bash 2> /dev/null`; do
echo ">>> including $f"
. $f # source 所有[a-z]*.bash腳本
done
fi
}3、lunch <product_name>-<build_variant>
lunch命令是一個shell函數，是在執行source build/envsetup.sh時添加到shell環境中的。
function lunch()
{
local answer
if [ "$1" ] ; then
answer=$1
else
print_lunch_menu # 3.1、循環打印LUNCH_MENU_CHOICES數組中的<product_name>-<build_variant>選項
echo -n "Which would you like? [aosp_arm-eng] "
read answer
fi
local selection=
if [ -z "$answer" ]
then
# 3.2、如果lunch時沒有指定或選中任何combo，就默認使用aosp_arm-eng，該combo是執行source build/envsetup.sh時添加到LUNCH_MENU_CHOICES中的
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 $selection | sed -e "s/-.*$//") # 把<product_name>賦值給變量product
check_product $product # 3.3、檢查product是否存在
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/^[^\-]*-//") # 把<build_variant>賦值給變量variant
check_variant $variant # 3.4、檢查variant是否合法
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=$variant
export TARGET_BUILD_TYPE=release
echo
set_stuff_for_environment # 3.5、設置編譯所需的環境變量
printconfig # 3.6、打印config
}3.1、循環打印LUNCH_MENU_CHOICES數組中的<product_name>-<build_variant>選項。
function print_lunch_menu()
{
local uname=$(uname)
echo
echo "You're building on" $uname
echo
echo "Lunch menu... pick a combo:"
local i=1
local choice
for choice in ${LUNCH_MENU_CHOICES[@]} # 打印LUNCH_MENU_CHOICES數組中的所有元素
do
echo " $i. $choice"
i=$(($i+1))
done
echo
}3.2、如果lunch時沒有指定或選中任何combo，就默認使用aosp_arm-eng，該combo是執行source build/envsetup.sh時添加到LUNCH_MENU_CHOICES中的。
# add the default one here
add_lunch_combo aosp_arm-eng
add_lunch_combo aosp_arm64-eng
add_lunch_combo aosp_mips-eng
add_lunch_combo aosp_mips64-eng
add_lunch_combo aosp_x86-eng
add_lunch_combo aosp_x86_64-eng3.3、檢查product是否存在
# check to see if the supplied product is one we can build
function check_product()
{
T=$(gettop)
if [ ! "$T" ]; then
echo "Couldn't locate the top of the tree. Try setting TOP." >&2
return
fi
TARGET_PRODUCT=$1 \
TARGET_BUILD_VARIANT= \
TARGET_BUILD_TYPE= \
TARGET_BUILD_APPS= \
get_build_var TARGET_DEVICE > /dev/null
# hide successful answers, but allow the errors to show
}VARIANT_CHOICES=(user userdebug eng)# check to see if the supplied variant is valid
function check_variant()
{
for v in ${VARIANT_CHOICES[@]} # <build_variant>必須是（user userdebug eng）中的一個。
do
if [ "$v" = "$1" ]
then
return 0
fi
done
return 1
}3.5、設置編譯所需的環境變量
function set_stuff_for_environment()
{
settitle # 3.5.1、設置title
set_java_home # 3.5.2、設置java home
setpaths # 3.5.3、設置paths
set_sequence_number # 3.5.4、設置sequence number
export ANDROID_BUILD_TOP=$(gettop) # 該變量是android代碼樹根目錄的絕對路徑
# With this environment variable new GCC can apply colors to warnings/errors
export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01' # 設置gcc的警告和錯誤可以彩色顯示
}3.5.1、設置title
function settitle()
{
if [ "$STAY_OFF_MY_LAWN" = "" ]; then # $STAY_OFF_MY_LAWN默認爲空，走if分支
local arch=$(gettargetarch)
local product=$TARGET_PRODUCT # 即<product_name>
local variant=$TARGET_BUILD_VARIANT # 即<build_name>
local apps=$TARGET_BUILD_APPS # 默認爲空
if [ -z "$apps" ]; then # $apps默認爲空，走if分會
export PROMPT_COMMAND="echo -ne \"\033]0;[${arch}-${product}-${variant}] ${USER}@${HOSTNAME}: ${PWD}\007\""
else
export PROMPT_COMMAND="echo -ne \"\033]0;[$arch $apps $variant] ${USER}@${HOSTNAME}: ${PWD}\007\""
fi
fi
}# Force JAVA_HOME to point to java 1.7 or java 1.6 if it isn't already set.
#
# Note that the MacOS path for java 1.7 includes a minor revision number (sigh).
# For some reason, installing the JDK doesn't make it show up in the
# JavaVM.framework/Versions/1.7/ folder.
function set_java_home() {
# Clear the existing JAVA_HOME value if we set it ourselves, so that
# we can reset it later, depending on the version of java the build
# system needs.
#
# If we don't do this, the JAVA_HOME value set by the first call to
# build/envsetup.sh will persist forever.
if [ -n "$ANDROID_SET_JAVA_HOME" ]; then # linux系統，$ANDROID_SET_JAVA_HOME默認爲空，不走if分支。
export JAVA_HOME=""
fi
if [ ! "$JAVA_HOME" ]; then # JAVA_HOME已經在第一步驟中export了。$JAVA_HOME不爲空，不走if分支。
if [ -n "$LEGACY_USE_JAVA6" ]; then
case `uname -s` in
Darwin)
export JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home
;;
*)
export JAVA_HOME=/usr/lib/jvm/java-6-sun
;;
esac
else
case `uname -s` in
Darwin)
export JAVA_HOME=$(/usr/libexec/java_home -v 1.7)
;;
*)
export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64
;;
esac
fi
# Keep track of the fact that we set JAVA_HOME ourselves, so that
# we can change it on the next envsetup.sh, if required.
export ANDROID_SET_JAVA_HOME=true
fi
}function setpaths()
{
T=$(gettop)
if [ ! "$T" ]; then
echo "Couldn't locate the top of the tree. Try setting TOP."
return
fi
##################################################################
# #
# Read me before you modify this code #
# #
# This function sets ANDROID_BUILD_PATHS to what it is adding #
# to PATH, and the next time it is run, it removes that from #
# PATH. This is required so lunch can be run more than once #
# and still have working paths. #
# #
##################################################################
# Note: on windows/cygwin, ANDROID_BUILD_PATHS will contain spaces
# due to "C:\Program Files" being in the path.
# out with the old
if [ -n "$ANDROID_BUILD_PATHS" ] ; then
export PATH=${PATH/$ANDROID_BUILD_PATHS/}
fi
if [ -n "$ANDROID_PRE_BUILD_PATHS" ] ; then
export PATH=${PATH/$ANDROID_PRE_BUILD_PATHS/}
# strip leading ':', if any
export PATH=${PATH/:%/}
fi
# and in with the new
prebuiltdir=$(getprebuilt)
gccprebuiltdir=$(get_abs_build_var ANDROID_GCC_PREBUILTS)
# defined in core/config.mk
targetgccversion=$(get_build_var TARGET_GCC_VERSION)
targetgccversion2=$(get_build_var 2ND_TARGET_GCC_VERSION)
export TARGET_GCC_VERSION=$targetgccversion
# The gcc toolchain does not exists for windows/cygwin. In this case, do not reference it.
export ANDROID_TOOLCHAIN=
export ANDROID_TOOLCHAIN_2ND_ARCH=
local ARCH=$(get_build_var TARGET_ARCH)
case $ARCH in
x86) toolchaindir=x86/x86_64-linux-android-$targetgccversion/bin
;;
x86_64) toolchaindir=x86/x86_64-linux-android-$targetgccversion/bin
;;
arm) toolchaindir=arm/arm-linux-androideabi-$targetgccversion/bin;
toolchaindir2=aarch64/aarch64-linux-android-$targetgccversion/bin
;;
arm64) toolchaindir=aarch64/aarch64-linux-android-$targetgccversion/bin;
toolchaindir2=arm/arm-linux-androideabi-$targetgccversion2/bin
;;
mips|mips64) toolchaindir=mips/mips64el-linux-android-$targetgccversion/bin
;;
*)
echo "Can't find toolchain for unknown architecture: $ARCH"
toolchaindir=xxxxxxxxx
;;
esac
if [ -d "$gccprebuiltdir/$toolchaindir" ]; then
export ANDROID_TOOLCHAIN=$gccprebuiltdir/$toolchaindir
fi
if [ -d "$gccprebuiltdir/$toolchaindir2" ]; then
export ANDROID_TOOLCHAIN_2ND_ARCH=$gccprebuiltdir/$toolchaindir2
fi
unset ANDROID_KERNEL_TOOLCHAIN_PATH
case $ARCH in
arm)
# Legacy toolchain configuration used for ARM kernel compilation
toolchaindir=arm/arm-eabi-$targetgccversion/bin
if [ -d "$gccprebuiltdir/$toolchaindir" ]; then
export ARM_EABI_TOOLCHAIN="$gccprebuiltdir/$toolchaindir"
ANDROID_KERNEL_TOOLCHAIN_PATH="$ARM_EABI_TOOLCHAIN":
fi
;;
arm64)
# Legacy toolchain configuration used for ARM kernel compilation
toolchaindir=arm/arm-eabi-$targetgccversion2/bin
if [ -d "$gccprebuiltdir/$toolchaindir" ]; then
export ARM_EABI_TOOLCHAIN="$gccprebuiltdir/$toolchaindir"
ANDROID_KERNEL_TOOLCHAIN_PATH="$ARM_EABI_TOOLCHAIN":
fi
;;
*)
# No need to set ARM_EABI_TOOLCHAIN for other ARCHs
;;
esac
export ANDROID_DEV_SCRIPTS=$T/development/scripts:$T/prebuilts/devtools/tools
export ANDROID_BUILD_PATHS=$(get_build_var ANDROID_BUILD_PATHS):$ANDROID_TOOLCHAIN:$ANDROID_TOOLCHAIN_2ND_ARCH:$ANDROID_KERNEL_TOOLCHAIN_PATH$ANDROID_DEV_SCRIPTS:
# If prebuilts/android-emulator/<system>/ exists, prepend it to our PATH
# to ensure that the corresponding 'emulator' binaries are used.
case $(uname -s) in
Darwin)
ANDROID_EMULATOR_PREBUILTS=$T/prebuilts/android-emulator/darwin-x86_64
;;
Linux)
ANDROID_EMULATOR_PREBUILTS=$T/prebuilts/android-emulator/linux-x86_64
;;
*)
ANDROID_EMULATOR_PREBUILTS=
;;
esac
if [ -n "$ANDROID_EMULATOR_PREBUILTS" -a -d "$ANDROID_EMULATOR_PREBUILTS" ]; then
ANDROID_BUILD_PATHS=$ANDROID_BUILD_PATHS$ANDROID_EMULATOR_PREBUILTS:
export ANDROID_EMULATOR_PREBUILTS
fi
export PATH=$ANDROID_BUILD_PATHS$PATH
unset ANDROID_JAVA_TOOLCHAIN
unset ANDROID_PRE_BUILD_PATHS
if [ -n "$JAVA_HOME" ]; then
export ANDROID_JAVA_TOOLCHAIN=$JAVA_HOME/bin # 第1步驟設置的JAVA_HOME環境變量，就在這個地方被使用了。
export ANDROID_PRE_BUILD_PATHS=$ANDROID_JAVA_TOOLCHAIN:
export PATH=$ANDROID_PRE_BUILD_PATHS$PATH
fi
unset ANDROID_PRODUCT_OUT
export ANDROID_PRODUCT_OUT=$(get_abs_build_var PRODUCT_OUT)
export OUT=$ANDROID_PRODUCT_OUT
unset ANDROID_HOST_OUT
export ANDROID_HOST_OUT=$(get_abs_build_var HOST_OUT)
# needed for building linux on MacOS
# TODO: fix the path
#export HOST_EXTRACFLAGS="-I "$T/system/kernel_headers/host_include
}function set_sequence_number()
{
export BUILD_ENV_SEQUENCE_NUMBER=10
}function printconfig()
{
T=$(gettop)
if [ ! "$T" ]; then
echo "Couldn't locate the top of the tree. Try setting TOP." >&2
return
fi
get_build_var report_config
}============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=5.1
TARGET_PRODUCT=aosp_oversea
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm64
TARGET_ARCH_VARIANT=armv8-a
TARGET_CPU_VARIANT=generic
TARGET_2ND_ARCH=arm
TARGET_2ND_ARCH_VARIANT=armv7-a-neon
TARGET_2ND_CPU_VARIANT=cortex-a15
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-3.5.0-23-generic-x86_64-with-Ubuntu-12.04-precise
HOST_BUILD_TYPE=release
BUILD_ID=LMY47D
OUT_DIR=out
============================================
~ end ~