Building System之编译前的准备工作

Android系统编译前的准备工作，我个人认为由如下三个步骤完成。接下来，我就逐一分析每一步骤都干了什么事情。

1、安装jdk、设置环境变量JAVA_HOME。

2、source build/envsetup.sh

3、lunch <product_name>-<build_variant>

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博文中出现的get_abs_build_var() 和 get_build_var()请移步到 这里

1、设置JAVA_HMOE环境变量

export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64

2、source build/envsetup.sh

该shell脚本实现了许多有用的shell函数，可通过执行hmm命令查看（hmm是envsetup.sh实现的第一个shell函数）。

下面是hmm命令显示的一部分：

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.

除了上面实现的shell函数，envsetup.sh还把device和vendor目录下的所有vendorsetup.sh脚本包含进来了。最后，还调用shell函数addcompletions。

if [ "x$SHELL" != "x/bin/bash" ]; then    case `ps -o command -p $$` in # $$属于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"            ;;    esacfi# 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doneunset faddcompletions # 检查bash版本，并source sdk/bash_completion目录下的所有[a-z]*.bash文件

$$ 请查看 Special Shell Variables

vendorsetup.sh的内容大多数是调用add_lunch_combo函数添加<product_name>-<build_variant>格式的lunch选项（也可以实现一些shell functions）。如：

add_lunch_combo aosp_flounder-userdebug

接下来，看一下add_lunch_combo函数的实现，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_CHOICESfunction 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选项都保存在数组LUNCH_MENU_CHOICES中}

我们回到envsetup.sh脚本的最后一行，看一下addcompletions函数的实现，File：build/envsetup.sh。

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脚本        done    fi}

3、lunch <product_name>-<build_variant>

lunch命令是一个shell函数，是在执行source  build/envsetup.sh时添加到shell环境中的。

function lunch(){    local answer    if [ "$1" ] ; then        answer=$1    else        print_lunch_menu # 3.1、循环打印LUNCH_MENU_CHOICES数组中的<product_name>-<build_variant>选项        echo -n "Which would you like? [aosp_arm-eng] "        read answer    fi    local selection=    if [ -z "$answer" ]    then# 3.2、如果lunch时没有指定或选中任何combo，就默认使用aosp_arm-eng，该combo是执行source build/envsetup.sh时添加到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>赋值给变量product    check_product $product # 3.3、检查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>赋值给变量variant    check_variant $variant # 3.4、检查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、设置编译所需的环境变量    printconfig # 3.6、打印config}

3.1、循环打印LUNCH_MENU_CHOICES数组中的<product_name>-<build_variant>选项。

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数组中的所有元素    do        echo "     $i. $choice"        i=$(($i+1))    done    echo}

3.2、如果lunch时没有指定或选中任何combo，就默认使用aosp_arm-eng，该combo是执行source build/envsetup.sh时添加到LUNCH_MENU_CHOICES中的。

# add the default one hereadd_lunch_combo aosp_arm-engadd_lunch_combo aosp_arm64-engadd_lunch_combo aosp_mips-engadd_lunch_combo aosp_mips64-engadd_lunch_combo aosp_x86-engadd_lunch_combo aosp_x86_64-eng

3.3、检查product是否存在

# check to see if the supplied product is one we can buildfunction 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}

3.4、检查variant是否合法

VARIANT_CHOICES=(user userdebug eng)

# check to see if the supplied variant is validfunction check_variant(){    for v in ${VARIANT_CHOICES[@]} # <build_variant>必须是（user userdebug eng）中的一个。    do        if [ "$v" = "$1" ]        then            return 0        fi    done    return 1}

3.5、设置编译所需的环境变量

function set_stuff_for_environment(){    settitle # 3.5.1、设置title    set_java_home # 3.5.2、设置java home    setpaths # 3.5.3、设置paths    set_sequence_number # 3.5.4、设置sequence number    export ANDROID_BUILD_TOP=$(gettop) # 该变量是android代码树根目录的绝对路径    # 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' # 设置gcc的警告和错误可以彩色显示}

3.5.1、设置title

function settitle(){    if [ "$STAY_OFF_MY_LAWN" = "" ]; then # $STAY_OFF_MY_LAWN默认为空，走if分支        local arch=$(gettargetarch)        local product=$TARGET_PRODUCT # 即<product_name>        local variant=$TARGET_BUILD_VARIANT # 即<build_name>        local apps=$TARGET_BUILD_APPS # 默认为空        if [ -z "$apps" ]; then # $apps默认为空，走if分会            export PROMPT_COMMAND="echo -ne \"\033]0;[${arch}-${product}-${variant}] ${USER}@${HOSTNAME}: ${PWD}\007\""        else            export PROMPT_COMMAND="echo -ne \"\033]0;[$arch $apps $variant] ${USER}@${HOSTNAME}: ${PWD}\007\""        fi    fi}

3.5.2、设置java home

# 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 "$ANDROID_SET_JAVA_HOME" ]; then # linux系统，$ANDROID_SET_JAVA_HOME默认为空，不走if分支。      export JAVA_HOME=""    fi    if [ ! "$JAVA_HOME" ]; then # JAVA_HOME已经在第一步骤中export了。$JAVA_HOME不为空，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}

3.5.3、设置paths

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=$JAVA_HOME/bin # 第1步骤设置的JAVA_HOME环境变量，就在这个地方被使用了。        export ANDROID_PRE_BUILD_PATHS=$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}

3.5.4、设置sequence number

function set_sequence_number(){    export BUILD_ENV_SEQUENCE_NUMBER=10}

3.6、打印config

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}

Example of printconfig
============================================
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
============================================

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