Android Makefile 分析之 (build/envsetup.sh)

build/envsetup.sh 脚本主体部分

看源代码之前需要了解代码分布和结构，分析Makefile应该是最好的方法。在Blog记录之以备以后查看，也供有兴趣朋友参考。

在编译donut之前，需要运行

cd ~/mydroid
. build/envsetup.sh
lunch aosp_dream_us-eng
make

build/envsetup.sh 是编译android的入口。该shell脚本定义了一些函数，并设定了编译的环境变量。

lunch aosp_dream_us-eng 配置用户需要编译的目标产品(target product)和变体(variant)。

aosp_dream_us-eng 字符串包含了target product 和variant，它们用减号-隔开，aosp_dream_us是target product，eng是variant。

variant 有三种选择user userdebug eng，可以从字面上看出其意义，但具体的差别还不是特别清楚，待后面分析之。

lunch 的入口是让用户指定或者选择需要编译的target product 和 variant，出口是设定编译相关的环境变量。

build/envsetup.sh 定义了很多函数，并且执行的脚本很分散，因此下面将所有的函数都删除掉了，剩余下脚本的主体，便于代码分析和走读。

该主体主要做的事情是：

1. 首先脚本设定了两个缺省的target product，一个是generic-eng，一个是simulator

2. 运行所有vendor下的 vendorsetup.sh文件，在google官方的 donut源代码中，为vendor/aosp/vendorsetup.sh，内容如下：

add_lunch_combo aosp_emulator_us-eng
add_lunch_combo aosp_emulator_eu-eng
add_lunch_combo aosp_dream_us-userdebug
add_lunch_combo aosp_dream_eu-userdebug
add_lunch_combo aosp_dream_us-eng
add_lunch_combo aosp_dream_eu-eng
add_lunch_combo aosp_sapphire_us-userdebug
add_lunch_combo aosp_sapphire_eu-userdebug
add_lunch_combo aosp_sapphire_us-eng
add_lunch_combo aosp_sapphire_eu-eng

可以看出，又添加了一些 和 aosp 相关的 target product 和 variant。

下面是脚本主体，用蓝色添加了一下注释，便于阅读：

# 定义了 variant的字符范围
VARIANT_CHOICES=(user userdebug eng)

# 如果是Linux环境，定义了几个和simulator相关的函数
case `uname -s` in
Linux)
function choosesim()
{
echo "Build for the simulator or the device?"
echo " 1. Device"
echo " 2. Simulator"
echo

export TARGET_SIMULATOR=
local ANSWER
while [ -z $TARGET_SIMULATOR ]
do
echo -n "Which would you like? [1] "
if [ -z "$1" ] ; then
read ANSWER
else
echo $1
ANSWER=$1
fi
case $ANSWER in
"")
export TARGET_SIMULATOR=false
;;
1)
export TARGET_SIMULATOR=false
;;
Device)
export TARGET_SIMULATOR=false
;;
2)
export TARGET_SIMULATOR=true
;;
Simulator)
export TARGET_SIMULATOR=true
;;
*)
echo
echo "I didn't understand your response. Please try again."
echo
;;
esac
if [ -n "$1" ] ; then
break
fi
done

set_stuff_for_environment
}
;;
*)
function choosesim()
{
echo "Only device builds are supported for" `uname -s`
echo " Forcing TARGET_SIMULATOR=false"
echo
if [ -z "$1" ]
then
echo -n "Press enter: "
read
fi

export TARGET_SIMULATOR=false
set_stuff_for_environment
}
;;
esac

# 首先将 LUNCH_MENU_CHOICES 变量消除
# 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

# 当前 LUNCH_MENU_CHOICES = generic-eng
# add the default one here
add_lunch_combo generic-eng

# 当前 LUNCH_MENU_CHOICES = generic-eng simulator
# if we're on linux, add the simulator. There is a special case
# in lunch to deal with the simulator
if [ "$(uname)" = "Linux" ] ; then
add_lunch_combo simulator
fi

# 这里是MAC OS的环境，不考虑
case `uname -s` in
Darwin)
function mgrep()
{
find -E . -type f -iregex '.*/(Makefile|Makefile/..*|.*/.make|.*/.mak|.*/.mk)' -print0 | xargs -0 grep --color -n "$@"
}

function treegrep()
{
find -E . -type f -iregex '.*/.(c|h|cpp|S|java|xml)' -print0 | xargs -0 grep --color -n -i "$@"
}

;;
*)
function mgrep()
{
find . -regextype posix-egrep -iregex '(.*//Makefile|.*//Makefile/..*|.*/.make|.*/.mak|.*/.mk)' -type f -print0 | xargs -0 grep --color -n "$@"
}

function treegrep()
{
find . -regextype posix-egrep -iregex '.*/.(c|h|cpp|S|java|xml)' -type f -print0 | xargs -0 grep --color -n -i "$@"
}

;;
esac

# 设定当前shell环境的数组下标从0开始还是1开始，并记录在 _arrayoffset
# determine whether arrays are zero-based (bash) or one-based (zsh)
_xarray=(a b c)
if [ -z "${_xarray[${#_xarray[@]}]}" ]
then
_arrayoffset=1
else
_arrayoffset=0
fi
unset _xarray

# 运行所有vendor下的 vendorsetup.sh文件
#存在vendor/aosp/vendorsetup.sh
当前 LUNCH_MENU_CHOICES = generic-eng simulator aosp_emulator_us-eng aosp_emulator_eu-eng aosp_dream_us-userdebug aosp_dream_eu-userdebug aosp_dream_us-eng aosp_dream_eu-eng aosp_sapphire_us-userdebug aosp_sapphire_eu-userdebug aosp_sapphire_us-eng aosp_sapphire_eu-eng

# Execute the contents of any vendorsetup.sh files we can find.
for f in `/bin/ls vendor/*/vendorsetup.sh vendor/*/build/vendorsetup.sh 2> /dev/null`
do
echo "including $f"
. $f
done
unset f