點擊打開鏈接
1、get_abs_build_var() 和 get_build_var()的實現都在build/envsetup.sh中。
2、在buld目錄下grep這兩個函數可知：這兩個函數只在build/envsetup.sh腳本中使用。
言歸正傳，貼代碼
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#?Get?the?value?of?a?build?variable?as?an?absolute?path.??function?get_abs_build_var()??{??????T=$(gettop)??????if?[?!?"$T"?];?then??????????echo?"Couldn't?locate?the?top?of?the?tree.??Try?setting?TOP."?>&2??????????return??????fi??????(\cd?$T;?CALLED_FROM_SETUP=true?BUILD_SYSTEM=build/core?\????????command?make?--no-print-directory?-f?build/core/config.mk?dumpvar-abs-$1)??}????#?Get?the?exact?value?of?a?build?variable.??function?get_build_var()??{??????T=$(gettop)??????if?[?!?"$T"?];?then??????????echo?"Couldn't?locate?the?top?of?the?tree.??Try?setting?TOP."?>&2??????????return??????fi??????(\cd?$T;?CALLED_FROM_SETUP=true?BUILD_SYSTEM=build/core?\????????command?make?--no-print-directory?-f?build/core/config.mk?dumpvar-$1)??}??
這兩個shell函數的實現很相似，都是通過make指定build/core/config.mk文件，唯一不同的地方是target目標不同。
接下來我們分析config.mk文件。
config.mk文件開頭的注釋：
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#?This?is?included?by?the?top-level?Makefile.??#?It?sets?up?standard?variables?based?on?the??#?current?configuration?and?platform,?which??#?are?not?specific?to?what?is?being?built.??
根據注釋，我們可知config.mk文件主要是配置變量。
而且，config.mk 文件最后一行包含的$(BUILD_SYSTEM)/dumpvar.mk用于獲取一些變量。
接下來我們分析dumpvar.mk文件。
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#?---------------------------------------------------------------??#?the?setpath?shell?function?in?envsetup.sh?uses?this?to?figure?out??#?what?to?add?to?the?path?given?the?config?we?have?chosen.??ifeq?($(CALLED_FROM_SETUP),true)?#?在get_abs_build_var()?和?get_build_var()函數中，CALLED_FROM_SETUP=true，走if分支。????ifneq?($(filter?/%,$(HOST_OUT_EXECUTABLES)),)???#?HOST_OUT_EXECUTABLES變量是在envsetup.mk文件中設置的。??ABP:=$(HOST_OUT_EXECUTABLES)??else??ABP:=$(PWD)/$(HOST_OUT_EXECUTABLES)??endif????ANDROID_BUILD_PATHS?:=?$(ABP)???#?應該是?out/host/linux-x86/bin??ANDROID_PREBUILTS?:=?prebuilt/$(HOST_PREBUILT_TAG)???#?HOST_PREBUILT_TAG變量是在envsetup.mk文件中設置的。應該是?linux-x86??ANDROID_GCC_PREBUILTS?:=?prebuilts/gcc/$(HOST_PREBUILT_TAG)????#?The?"dumpvar"?stuff?lets?you?say?something?like??#??#?????CALLED_FROM_SETUP=true?\??#???????make?-f?config/envsetup.make?dumpvar-TARGET_OUT??#?or??#?????CALLED_FROM_SETUP=true?\??#???????make?-f?config/envsetup.make?dumpvar-abs-HOST_OUT_EXECUTABLES??#??#?The?plain?(non-abs)?version?just?dumps?the?value?of?the?named?variable.??#?The?"abs"?version?will?treat?the?variable?as?a?path,?and?dumps?an??#?absolute?path?to?it.??#??dumpvar_goals?:=?\??????????$(strip?$(patsubst?dumpvar-%,%,$(filter?dumpvar-%,$(MAKECMDGOALS))))???????????#?MAKECMDGOALS?變量就是傳進來的目標dumpvar-abs-$1或?dumpvar-$1。??ifdef?dumpvar_goals??????ifneq?($(words?$(dumpvar_goals)),1)??????$(error?Only?one?"dumpvar-"?goal?allowed.?Saw?"$(MAKECMDGOALS)")????endif??????#?If?the?goal?is?of?the?form?"dumpvar-abs-VARNAME",?then????#?treat?VARNAME?as?a?path?and?return?the?absolute?path?to?it.????absolute_dumpvar?:=?$(strip?$(filter?abs-%,$(dumpvar_goals)))????ifdef?absolute_dumpvar??????dumpvar_goals?:=?$(patsubst?abs-%,%,$(dumpvar_goals))??????ifneq?($(filter?/%,$($(dumpvar_goals))),)????????DUMPVAR_VALUE?:=?$($(dumpvar_goals))??????else????????DUMPVAR_VALUE?:=?$(PWD)/$($(dumpvar_goals))??????endif??????dumpvar_target?:=?dumpvar-abs-$(dumpvar_goals)????else??????DUMPVAR_VALUE?:=?$($(dumpvar_goals))??????dumpvar_target?:=?dumpvar-$(dumpvar_goals)????endif????.PHONY:?$(dumpvar_target)??$(dumpvar_target):??????????@echo?$(DUMPVAR_VALUE)???????????#?DUMPVAR_VALE其實就是dumpvar-$1中的$1變量的值。????endif?#?dumpvar_goals????ifneq?($(dumpvar_goals),report_config)???#?PRINT_BUILD_CONFIG?在envsetup.mk中被定義為true??PRINT_BUILD_CONFIG:=??endif????endif?#?CALLED_FROM_SETUP??????ifneq?($(PRINT_BUILD_CONFIG),)??HOST_OS_EXTRA:=$(shell?python?-c?"import?platform;?print(platform.platform())")???$(info?============================================)??$(info???PLATFORM_VERSION_CODENAME=$(PLATFORM_VERSION_CODENAME))??$(info???PLATFORM_VERSION=$(PLATFORM_VERSION))??$(info???TARGET_PRODUCT=$(TARGET_PRODUCT))??$(info???TARGET_BUILD_VARIANT=$(TARGET_BUILD_VARIANT))??$(info???TARGET_BUILD_TYPE=$(TARGET_BUILD_TYPE))??$(info???TARGET_BUILD_APPS=$(TARGET_BUILD_APPS))??$(info???TARGET_ARCH=$(TARGET_ARCH))??$(info???TARGET_ARCH_VARIANT=$(TARGET_ARCH_VARIANT))??$(info???TARGET_CPU_VARIANT=$(TARGET_CPU_VARIANT))??$(info???TARGET_2ND_ARCH=$(TARGET_2ND_ARCH))??$(info???TARGET_2ND_ARCH_VARIANT=$(TARGET_2ND_ARCH_VARIANT))??$(info???TARGET_2ND_CPU_VARIANT=$(TARGET_2ND_CPU_VARIANT))??$(info???HOST_ARCH=$(HOST_ARCH))??$(info???HOST_OS=$(HOST_OS))??$(info???HOST_OS_EXTRA=$(HOST_OS_EXTRA))??$(info???HOST_BUILD_TYPE=$(HOST_BUILD_TYPE))??$(info???BUILD_ID=$(BUILD_ID))??$(info???OUT_DIR=$(OUT_DIR))??$(info?============================================)??endif??
小結：
大多數的變量配置都是在config.mk中設置的，尤其是其包含的envsetup.mk文件。所以，就在config.mk的最后包含dumpvar.mk文件，該文件執行@echo $(DUMPVAR_VALUE)輸出$1變量值。
Examples:
1、get_abs_build_var?ANDROID_GCC_PREBUILTS
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#####################???#?file：envsetup.mk?#??#####################???34?#?---------------------------------------------------------------???35?#?Set?up?configuration?for?host?machine.??We?don't?do?cross-???36?#?compiles?except?for?arm/mips,?so?the?HOST?is?whatever?we?are???37?#?running?on???38????39?UNAME?:=?$(shell?uname?-sm)???40????41?#?HOST_OS???42?ifneq?(,$(findstring?Linux,$(UNAME)))???43???<u><strong>HOST_OS</strong></u>?:=?linux???44?endif???45?ifneq?(,$(findstring?Darwin,$(UNAME)))???46???HOST_OS?:=?darwin???47?endif???48?ifneq?(,$(findstring?Macintosh,$(UNAME)))???49???HOST_OS?:=?darwin???50?endif???51?ifneq?(,$(findstring?CYGWIN,$(UNAME)))???52???HOST_OS?:=?windows???53?endif????108?#?We?don't?want?to?move?all?the?prebuilt?host?tools?to?a?$(HOST_OS)-x86_64?dir.??109?HOST_PREBUILT_ARCH?:=?x86??110?#?This?is?the?standard?way?to?name?a?directory?containing?prebuilt?host??111?#?objects.?E.g.,?prebuilt/$(HOST_PREBUILT_TAG)/cc??112?ifeq?($(HOST_OS),windows)??113???HOST_PREBUILT_TAG?:=?windows??114?else??115???HOST_PREBUILT_TAG?:=?$(HOST_OS)-$(HOST_PREBUILT_ARCH)??116?endif??##############??#?dumpvar.mk?#??##############??./dumpvar.mk:ANDROID_GCC_PREBUILTS?:=?prebuilts/gcc/$(HOST_PREBUILT_TAG)??
2、get_abs_build_var?PRODUCT_OUT
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#####################???#?file：envsetup.mk?#??#####################??192?#?the?target?build?type?defaults?to?release??193?ifneq?($(TARGET_BUILD_TYPE),debug)??194?TARGET_BUILD_TYPE?:=?release??195?endif??196???197?#?---------------------------------------------------------------??198?#?figure?out?the?output?directories??199???200?ifeq?(,$(strip?$(OUT_DIR)))??201?ifeq?(,$(strip?$(OUT_DIR_COMMON_BASE)))??202?OUT_DIR?:=?$(TOPDIR)out??203?else??204?OUT_DIR?:=?$(OUT_DIR_COMMON_BASE)/$(notdir?$(PWD))??205?endif??206?endif207???208?DEBUG_OUT_DIR?:=?$(OUT_DIR)/debug??209??210?#?Move?the?host?or?target?under?the?debug/?directory??211?#?if?necessary.??212?TARGET_OUT_ROOT_release?:=?$(OUT_DIR)/target??213?TARGET_OUT_ROOT_debug?:=?$(DEBUG_OUT_DIR)/target??214?TARGET_OUT_ROOT?:=?$(TARGET_OUT_ROOT_$(TARGET_BUILD_TYPE))????227?TARGET_PRODUCT_OUT_ROOT?:=?$(TARGET_OUT_ROOT)/product????232?PRODUCT_OUT?:=?$(TARGET_PRODUCT_OUT_ROOT)/$(TARGET_DEVICE)????#####################??#?product_config.mk?#??#####################??./product_config.mk:TARGET_DEVICE?:=?$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_DEVICE)???#?該變量的分析將獨立寫一篇文章介紹。??
3、get_abs_build_var?HOST_OUT
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??#####################????#?file:?envsetup.mk?#????#####################????1?#?Variables?we?check:????2?#?????HOST_BUILD_TYPE?=?{?release?debug?}????3?#?????TARGET_BUILD_TYPE?=?{?release?debug?}????4?#?and?we?output?a?bunch?of?variables,?see?the?case?statement?at????5?#?the?bottom?for?the?full?list????6?#?????OUT_DIR?is?also?set?to?"out"?if?it's?not?already?set.????7?#?????????this?allows?you?to?set?it?to?somewhere?else?if?you?like?????97?#?the?host?build?defaults?to?release,?and?it?must?be?release?or?debug???98?ifeq?($(HOST_BUILD_TYPE),)???99?HOST_BUILD_TYPE?:=?release??100?endif??101???102?ifneq?($(HOST_BUILD_TYPE),release)??103?ifneq?($(HOST_BUILD_TYPE),debug)??104?$(error?HOST_BUILD_TYPE?must?be?either?release?or?debug,?not?'$(HOST_BUILD_TYPE)')??105?endif??106?endif????216?HOST_OUT_ROOT_release?:=?$(OUT_DIR)/host?#?OUT_DIR?見2的分析。??217?HOST_OUT_ROOT_debug?:=?$(DEBUG_OUT_DIR)/host?#?DEBUG_OUT_DIR?見2的分析。????220?#?We?want?to?avoid?two?host?bin?directories?in?multilib?build.??221?HOST_OUT_release?:=?$(HOST_OUT_ROOT_release)/$(HOST_OS)-$(HOST_PREBUILT_ARCH)????????????????????????????????????????????????????#?HOST_OS?見?1?的分析。??222?HOST_OUT_debug?:=?$(HOST_OUT_ROOT_debug)/$(HOST_OS)-$(HOST_PREBUILT_ARCH)???????????????????????????????????????????????????#?HOST_PREBUILT_ARCH?見?1?的分析。??223?HOST_OUT?:=?$(HOST_OUT_$(HOST_BUILD_TYPE))??
4、get_build_var?TARGET_DEVICE
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#####################??#?product_config.mk?#??#####################??./product_config.mk:TARGET_DEVICE?:=?$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_DEVICE)???#?該變量的分析將獨立寫一篇文章介紹。??
5、get_build_var TARGET_GCC_VERSION
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TARGET_GCC_VERSION是在combo/TARGET_linux-$(TARGET_ARCH).mk文件中賦的值。??而TARGET_linux-$(TARGET_ARCH).mk文件是有config.mk?->?combo/select.mk文件選擇性包含進來的。??
6、get_build_var?2ND_TARGET_GCC_VERSION
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./core/envsetup.mk:254:HOST_2ND_ARCH_VAR_PREFIX?:=?2ND_??./core/envsetup.mk:297:TARGET_2ND_ARCH_VAR_PREFIX?:=?$(HOST_2ND_ARCH_VAR_PREFIX)????./core/config.mk:156:include?$(BUILD_SYSTEM)/envsetup.mk??./core/config.mk:230:combo_2nd_arch_prefix?:=??./core/config.mk:236:combo_2nd_arch_prefix?:=?$(HOST_2ND_ARCH_VAR_PREFIX)??./core/config.mk:244:combo_2nd_arch_prefix?:=??./core/config.mk:250:combo_2nd_arch_prefix?:=?$(TARGET_2ND_ARCH_VAR_PREFIX)????$(combo_2nd_arch_prefix)TARGET_GCC_VERSION的賦值是在combo/TARGET_linux-$(TARGET_ARCH).mk?文件中賦的值。??
7、get_build_var?TARGET_ARCH
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TARGET_ARCH是在BoardConfig.mk文件中賦的值。??BoardConfig.mk文件是由config.mk?->?envsetup.mk中的$(board_config_mk)變量包含進來的。??
8、get_build_var?ANDROID_BUILD_PATHS
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./core/envsetup.mk:238:HOST_OUT_EXECUTABLES?:=?$(HOST_OUT)/bin???????????????????????????????????????????????#?HOST_OUT?見?3?的分析。??##############??#?dumpvar.mk?#??##############??ifneq?($(filter?/%,$(HOST_OUT_EXECUTABLES)),)??ABP:=$(HOST_OUT_EXECUTABLES)??else??ABP:=$(PWD)/$(HOST_OUT_EXECUTABLES)??endif????ANDROID_BUILD_PATHS?:=?$(ABP)??
9、get_build_var?report_config
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在dumpvar.mk中，目標是report_config的代碼流程如下：????ifneq?($(dumpvar_goals),report_config)??PRINT_BUILD_CONFIG:=??endif????endif?#?CALLED_FROM_SETUP????ifneq?($(PRINT_BUILD_CONFIG),)??HOST_OS_EXTRA:=$(shell?python?-c?"import?platform;?print(platform.platform())")??$(info?============================================)??$(info???PLATFORM_VERSION_CODENAME=$(PLATFORM_VERSION_CODENAME))??#?./core/version_defaults.mk:62:??PLATFORM_VERSION_CODENAME?:=?REL??$(info???PLATFORM_VERSION=$(PLATFORM_VERSION))??#?./core/version_defaults.mk:44:??PLATFORM_VERSION?:=?5.1????$(info???TARGET_PRODUCT=$(TARGET_PRODUCT))??#?是lunch時選擇的<product_name>??#?./envsetup.sh:????export?TARGET_PRODUCT=$product??$(info???TARGET_BUILD_VARIANT=$(TARGET_BUILD_VARIANT))??#?是lunch時選擇的<product_variant>??#?./envsetup.sh:????export?TARGET_BUILD_VARIANT=$variant??$(info???TARGET_BUILD_TYPE=$(TARGET_BUILD_TYPE))??#?是lunch時默認指定的，release??#?./envsetup.sh:????export?TARGET_BUILD_TYPE=release??$(info???TARGET_BUILD_APPS=$(TARGET_BUILD_APPS))??#?是lunch時默認指定的，空值??#?./envsetup.sh:????export?TARGET_BUILD_APPS=??$(info???TARGET_ARCH=$(TARGET_ARCH))?#?TARGET_ARCH?見?7?的分析。????$(info???TARGET_ARCH_VARIANT=$(TARGET_ARCH_VARIANT))??#?是在$(board_config_mk)即?BoardConfig.mk文件中賦的值。??$(info???TARGET_CPU_VARIANT=$(TARGET_CPU_VARIANT))??#?是在$(board_config_mk)即?BoardConfig.mk文件中賦的值。??$(info???TARGET_2ND_ARCH=$(TARGET_2ND_ARCH))??#?是在$(board_config_mk)即?BoardConfig.mk文件中賦的值。??$(info???TARGET_2ND_ARCH_VARIANT=$(TARGET_2ND_ARCH_VARIANT))??#?是在$(board_config_mk)即?BoardConfig.mk文件中賦的值。??$(info???TARGET_2ND_CPU_VARIANT=$(TARGET_2ND_CPU_VARIANT))??#?是在$(board_config_mk)即?BoardConfig.mk文件中賦的值。????$(info???HOST_ARCH=$(HOST_ARCH))??#?./core/envsetup.mk:79:??HOST_ARCH?:=?x86_64??$(info???HOST_OS=$(HOST_OS))?#?HOST_OS?見?1?的分析。??$(info???HOST_OS_EXTRA=$(HOST_OS_EXTRA))?#?ifneq?的第一行。??$(info???HOST_BUILD_TYPE=$(HOST_BUILD_TYPE))?#?HOST_BUILD_TYPE?見?3?的分析。????$(info???BUILD_ID=$(BUILD_ID))??#?./core/build_id.mk:21:export?BUILD_ID=LMY47D??$(info???OUT_DIR=$(OUT_DIR))?#?OUT_DIR?見?2?的分析。??$(info?============================================)??endif??
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