Android编译原理之lunch

source build/envsetup.sh
lunch bengal_515-userdebug
make -j8

Android.bp --> Blueprint --> Soong --> Ninja
Makefile or Android.mk --> kati --> Ninja
Android.mk --> Soong --> Blueprint --> Android.bp

validate_current_shell
source_vendorsetup
addcompletions

function validate_current_shell() {
    local current_sh="$(ps -o command -p $$)"
    case "$current_sh" in
        *bash*)
            function check_type() { type -t "$1"; }
            ;;
        *zsh*)
            function check_type() { type "$1"; }
            enable_zsh_completion ;;
        *)
            echo -e "WARNING: Only bash and zsh are supported.\\nUse of other shell would lead to erroneous results."
            ;;
    esac
}

function source_vendorsetup() {
    allowed=
    for f in $(find -L device vendor product -maxdepth 4 -name 'allowed-vendorsetup_sh-files' 2>/dev/null | sort); do
        if [ -n "$allowed" ]; then
            echo "More than one 'allowed_vendorsetup_sh-files' file found, not including any vendorsetup.sh files:"
            echo "  $allowed"
            echo "  $f"
            return
        fi
        allowed="$f"
    done

    allowed_files=
    [ -n "$allowed" ] && allowed_files=$(cat "$allowed")
    for dir in device vendor product; do
        for f in $(test -d $dir && \\
            find -L $dir -maxdepth 4 -name 'vendorsetup.sh' 2>/dev/null | sort); do

            if [[ -z "$allowed" || "$allowed_files" =~ $f ]]; then
                echo "including $f"; . "$f"
            else
                echo "ignoring $f, not in $allowed"
            fi
        done
    done
}

function addcompletions()
{
    local T dir f

    # Keep us from trying to run in something that's neither bash nor zsh.
        # 检测shell版本字符串BASH_VERSION 或ZSH_VERSION长度为0时，返回
    if [ -z "$BASH_VERSION" -a -z "$ZSH_VERSION" ]; then
        return
    fi

    # Keep us from trying to run in bash that's too old.
    # 检测bash主版本低于3时返回
    if [ -n "$BASH_VERSION" -a ${BASH_VERSINFO[0]} -lt 3 ]; then
        return
    fi

        # 指定bash文件目录并检查是否存在
    local completion_files=(
      system/core/adb/adb.bash
      system/core/fastboot/fastboot.bash
      tools/asuite/asuite.sh
    )
    # Completion can be disabled selectively to allow users to use non-standard completion.
    # e.g.
    # ENVSETUP_NO_COMPLETION=adb # -> disable adb completion
    # ENVSETUP_NO_COMPLETION=adb:bit # -> disable adb and bit completion
        #*.bash文件列表，并将这些*.bash文件包含进来
    for f in ${completion_files[*]}; do
        if [ -f "$f" ] && should_add_completion "$f"; then
                 # 对*.bash文件执行'.'操作
            . $f
        fi
    done

    if should_add_completion bit ; then
        complete -C "bit --tab" bit
    fi
    if [ -z "$ZSH_VERSION" ]; then
        # Doesn't work in zsh.
        complete -o nospace -F _croot croot
    fi
    complete -F _lunch lunch   # _lunch命令提供lunch命令的补全操作

    complete -F _complete_android_module_names gomod
    complete -F _complete_android_module_names m
}

function lunch()
{
    local answer
        # 获取lunch操作的参数
    if [ "$1" ] ; then
        answer=$1
    else
           # lunch操作不带参数，则先显示lunch menu，然后读取用户输入
        print_lunch_menu
        echo -n "Which would you like? [aosp_arm-eng] "
        read answer
    fi

    local selection=
       # lunch操作得到的结果为空（例如用户直接在lunch要求输入时回车的情况）
    # 则将选项默认为"aosp_arm-eng"
    if [ -z "$answer" ]
    then
        selection=aosp_arm-eng
        # lunch操作得到的输入是数字，则将数字转换为LUNCH_MENU_CHOICES中的字符串
    elif (echo -n $answer | grep -q -e "^[0-9][0-9]*$")
    then
        local choices=($(TARGET_BUILD_APPS= get_build_var COMMON_LUNCH_CHOICES))
        if [ $answer -le ${#choices[@]} ]
        then
            # array in zsh starts from 1 instead of 0.
            if [ -n "$ZSH_VERSION" ]
            then
                selection=${choices[$(($answer))]}
            else
                selection=${choices[$(($answer-1))]}
            fi
        fi
    else
        selection=$answer
    fi

    export TARGET_BUILD_APPS=

    local product variant_and_version variant version

    product=${selection%%-*} # Trim everything after first dash
    variant_and_version=${selection#*-} # Trim everything up to first dash
    if [ "$variant_and_version" != "$selection" ]; then
        variant=${variant_and_version%%-*}
        if [ "$variant" != "$variant_and_version" ]; then
            version=${variant_and_version#*-}
        fi
    fi

    if [ -z "$product" ]
    then
        echo
        echo "Invalid lunch combo: $selection"
        return 1
    fi

        # 设置TARGET_PRODUCT和TARGET_BUILD_VARIANT
    TARGET_PRODUCT=$product \\
    TARGET_BUILD_VARIANT=$variant \\
    TARGET_PLATFORM_VERSION=$version \\

    # 根据前面的设置，更新编译环境相关变量
    build_build_var_cache     #参考[3.1.1]
    if [ $? -ne 0 ]
    then
        return 1
    fi

        # export 编译选项TARGET_PRODUCT, TARGET_BUILD_VARIANT和TARGET_BUILD_TYPE三元组
    export TARGET_PRODUCT=$(get_build_var TARGET_PRODUCT)
    export TARGET_BUILD_VARIANT=$(get_build_var TARGET_BUILD_VARIANT)
    if [ -n "$version" ]; then
      export TARGET_PLATFORM_VERSION=$(get_build_var TARGET_PLATFORM_VERSION)
    else
      unset TARGET_PLATFORM_VERSION
    fi
    export TARGET_BUILD_TYPE=release

    echo

    set_stuff_for_environment # 设置其他环境变量，如PROMPT_COMMAND，编译toolchain和tools相关的路径等
    printconfig        # 输出当前的设置选项
    destroy_build_var_cache
}

function build_build_var_cache()
{
    local T=$(gettop)
    # Grep out the variable names from the script.
    cached_vars=(`cat $T/build/envsetup.sh | tr '()' '  ' | awk '{for(i=1;i<=NF;i++) if($i~/get_build_var/) print $(i+1)}' | sort -u | tr '\\n' ' '`)
    cached_abs_vars=(`cat $T/build/envsetup.sh | tr '()' '  ' | awk '{for(i=1;i<=NF;i++) if($i~/get_abs_build_var/) print $(i+1)}' | sort -u | tr '\\n' ' '`)
    # Call the build system to dump the "<val>=<value>" pairs as a shell script.
    build_dicts_script=`\\builtin cd $T; build/soong/soong_ui.bash --dumpvars-mode \\
                        --vars="${cached_vars[*]}" \\
                        --abs-vars="${cached_abs_vars[*]}" \\
                        --var-prefix=var_cache_ \\
                        --abs-var-prefix=abs_var_cache_`
    local ret=$?
    if [ $ret -ne 0 ]
    then
        unset build_dicts_script
        return $ret
    fi
    # Execute the script to store the "<val>=<value>" pairs as shell variables.
    eval "$build_dicts_script"
    ret=$?
    unset build_dicts_script
    if [ $ret -ne 0 ]
    then
        return $ret
    fi
    BUILD_VAR_CACHE_READY="true"
}

[build/soong/cmd/soong_ui/main.go]
func main() {
...
    if os.Args[1] == "--dumpvar-mode" {
        dumpVar(buildCtx, config, os.Args[2:])
    } else if os.Args[1] == "--dumpvars-mode" {
        dumpVars(buildCtx, config, os.Args[2:])
    } else {
        ...
    }
...
}
[build/soong/cmd/soong_ui/main.go]
func dumpVars(ctx build.Context, config build.Config, args []string) {
       varData, err := build.DumpMakeVars(ctx, config, nil, allVars)
}

[/build/soong/ui/build/dumpvars.go]
func dumpMakeVars(ctx Context, config Config, goals, vars []string, write_soong_vars bool) (map[string]string, error) {
    ctx.BeginTrace(metrics.RunKati, "dumpvars")
    defer ctx.EndTrace()

    cmd := Command(ctx, config, "dumpvars",
        config.PrebuiltBuildTool("ckati"),
        "-f", "build/make/core/config.mk",
        "--color_warnings",
        "--kati_stats",
        "dump-many-vars",
        "MAKECMDGOALS="+strings.Join(goals, " "))
    cmd.Environment.Set("CALLED_FROM_SETUP", "true")
    if write_soong_vars {
        cmd.Environment.Set("WRITE_SOONG_VARIABLES", "true")
    }
    cmd.Environment.Set("DUMP_MANY_VARS", strings.Join(vars, " "))
    cmd.Sandbox = dumpvarsSandbox
    output := bytes.Buffer{}
    cmd.Stdout = &output
    pipe, err := cmd.StderrPipe()
    if err != nil {
        ctx.Fatalln("Error getting output pipe for ckati:", err)
    }
    cmd.StartOrFatal()
    // TODO: error out when Stderr contains any content
    status.KatiReader(ctx.Status.StartTool(), pipe)
    cmd.WaitOrFatal()

    ret := make(map[string]string, len(vars))
    ...

    return ret, nil
}

...

#配置两个目录的变量，供之后的mk使用
BUILD_SYSTEM :=$= build/make/core
BUILD_SYSTEM_COMMON :=$= build/make/common

#加载core.mk， 只使用ANDROID_BUILD_SHELL来包装bash。
include $(BUILD_SYSTEM_COMMON)/core.mk

#设置make中使用的有效数学函数。
include $(BUILD_SYSTEM_COMMON)/math.mk

include $(BUILD_SYSTEM_COMMON)/strings.mk

include $(BUILD_SYSTEM_COMMON)/json.mk

# 避免硬件解码路径被覆盖的调用pathmap.mk建立硬解映射
include $(BUILD_SYSTEM)/pathmap.mk

# 允许项目定义自己的全局可用变量
include $(BUILD_SYSTEM)/project_definitions.mk

# ###############################################################
# Build system internal files
# ###############################################################
# 构建系统内部文件（写Android.mk时会调用include头文件，也就是这些makefile文件）

BUILD_COMBOS:= $(BUILD_SYSTEM)/combo

CLEAR_VARS:= $(BUILD_SYSTEM)/clear_vars.mk
BUILD_HOST_STATIC_LIBRARY:= $(BUILD_SYSTEM)/host_static_library.mk
BUILD_HOST_SHARED_LIBRARY:= $(BUILD_SYSTEM)/host_shared_library.mk
BUILD_STATIC_LIBRARY:= $(BUILD_SYSTEM)/static_library.mk

...

BUILD_NOTICE_FILE := $(BUILD_SYSTEM)/notice_files.mk
BUILD_HOST_DALVIK_JAVA_LIBRARY := $(BUILD_SYSTEM)/host_dalvik_java_library.mk
BUILD_HOST_DALVIK_STATIC_JAVA_LIBRARY := $(BUILD_SYSTEM)/host_dalvik_static_java_library.mk

BUILD_HOST_TEST_CONFIG := $(BUILD_SYSTEM)/host_test_config.mk
BUILD_TARGET_TEST_CONFIG := $(BUILD_SYSTEM)/target_test_config.mk

#定义大多数全局变量。这些是特定于用户的构建配置的。
include $(BUILD_SYSTEM)/envsetup.mk

#构建系统为在哪里找到内核公开了几个变量
#(1)TARGET_DEVICE_KERNEL_HEADERS是为当前正在构建的设备自动创建的。
#它被设置为$（TARGET_DEVICE_DIR）/kernel headers，
#例如DEVICE/samsung/tuna/kernel headers。此目录不是由任何人显式设置的，生成系统总是添加此子目录。
TARGET_DEVICE_KERNEL_HEADERS := $(strip $(wildcard $(TARGET_DEVICE_DIR)/kernel-headers))

#(2)TARGET_BOARD_KERNEL_HEADERS由BoardConfig.mk允许包含其他目录的文件。
#如果有一些常见的地方为一组设备保留了一些报头，那么这很有用。
#例如，device/<vendor>/common/kernel头可以包含一些<vendor>设备的头。
TARGET_BOARD_KERNEL_HEADERS := $(strip $(wildcard $(TARGET_BOARD_KERNEL_HEADERS)))
TARGET_BOARD_KERNEL_HEADERS := $(patsubst %/,%,$(TARGET_BOARD_KERNEL_HEADERS))
$(call validate-kernel-headers,$(TARGET_BOARD_KERNEL_HEADERS))
#(3)TARGET_PRODUCT_KERNEL_头由产品继承图生成。
#这允许体系结构产品为使用该体系结构的设备提供报头。
TARGET_PRODUCT_KERNEL_HEADERS := $(strip $(wildcard $(PRODUCT_VENDOR_KERNEL_HEADERS)))
TARGET_PRODUCT_KERNEL_HEADERS := $(patsubst %/,%,$(TARGET_PRODUCT_KERNEL_HEADERS))
$(call validate-kernel-headers,$(TARGET_PRODUCT_KERNEL_HEADERS))

# 选择一个Java编译器
include $(BUILD_SYSTEM)/combo/javac.mk

# A list of SEPolicy versions, besides PLATFORM_SEPOLICY_VERSION, that the framework supports.
#框架支持的SEPolicy版本列表，除了PLATFORM_SEPOLICY_VERSION
PLATFORM_SEPOLICY_COMPAT_VERSIONS := \\
    26.0 \\
    27.0 \\
    28.0 \\

ifeq ($(CALLED_FROM_SETUP),true)
include $(BUILD_SYSTEM)/ninja_config.mk
include $(BUILD_SYSTEM)/soong_config.mk
endif

#加载dumpvar.mk,用来生成make目标
include $(BUILD_SYSTEM)/dumpvar.mk

...
#设置host和target编译链相关的变量
include $(BUILD_SYSTEM)/combo/select.mk
#可以得到TARGET_DEVICE和其他变量，我们需要找到输出文件
include $(BUILD_SYSTEM)/product_config.mk

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

...
# ---------------------------------------------------------------
# Include the product definitions.
# We need to do this to translate TARGET_PRODUCT into its
# underlying TARGET_DEVICE before we start defining any rules.
#
include $(BUILD_SYSTEM)/node_fns.mk
include $(BUILD_SYSTEM)/product.mk
include $(BUILD_SYSTEM)/device.mk

...

#############################################################################
# Sanity check and assign default values
TARGET_DEVICE := $(PRODUCT_DEVICE)
...

...
# Boards may be defined under $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)
# or under vendor/*/$(TARGET_DEVICE).  Search in both places, but
# make sure only one exists.
# Real boards should always be associated with an OEM vendor.
ifdef TARGET_DEVICE_DIR
  ifneq ($(origin TARGET_DEVICE_DIR),command line)
    $(error TARGET_DEVICE_DIR may not be set manually)
  endif
  board_config_mk := $(TARGET_DEVICE_DIR)/BoardConfig.mk
else
  board_config_mk := \\
    $(strip $(sort $(wildcard \\
      $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk \\
      $(shell test -d device && find -L device -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \\
      $(shell test -d vendor && find -L vendor -maxdepth 4 -path '*/$(TARGET_DEVICE)/BoardConfig.mk') \\
    )))
  ifeq ($(board_config_mk),)
    $(error No config file found for TARGET_DEVICE $(TARGET_DEVICE))
  endif
  ifneq ($(words $(board_config_mk)),1)
    $(error Multiple board config files for TARGET_DEVICE $(TARGET_DEVICE): $(board_config_mk))
  endif
  TARGET_DEVICE_DIR := $(patsubst %/,%,$(dir $(board_config_mk)))
  .KATI_READONLY := TARGET_DEVICE_DIR
endif
include $(board_config_mk)
...