Android build system note 收藏 1. Android编译系统分析编译脚本及系统变量build/envsetup.sh脚本分析在编译源代码之前通常需要在android源代码顶层目录执行 . ./build/envsetup.sh 目的是为了使用脚本 envsetup.sh 里面定义了一些函数：function help()function get_abs_build_var()function get_build_var()function check_product()function check_variant()function setpaths()function printconfig()function set_stuff_for_environment()function set_sequence_number()function settitle()function choosetype()function chooseproduct()function choosevariant()function tapas()function choosecombo()function print_lunch_menu()function lunch()function gettopfunction m()function findmakefile()function mm()function mmm()function croot()function pid()function gdbclient()function jgrep()function cgrep()function resgrep()function getprebuiltfunction tracedmdump()function runhat()function getbugreports()function startviewserver()function stopviewserver()function isviewserverstarted()function smoketest()function runtest()function runtest_py()function godir ()
choosecombo 命令分析：function choosecombo(){choosesim $1echoechochoosetype $2
echoechochooseproduct $3
echoechochoosevariant $4
echoset_stuff_for_environmentprintconfig}会依次进行如下选择：Build for the simulator or the device?1. Device2. SimulatorWhich would you like? [1]
Build type choices are:1. release2. debugWhich would you like? [1]
Product choices are:1. emulator2. generic3. sim4. littletonYou can also type the name of a product if you know it.Which would you like? [littleton]
Variant choices are:1. user2. userdebug3. engWhich would you like? [eng] user默认选择以后会出现：TARGET_PRODUCT=littletonTARGET_BUILD_VARIANT=userTARGET_SIMULATOR=falseTARGET_BUILD_TYPE=releaseTARGET_ARCH=armHOST_ARCH=x86HOST_OS=linuxHOST_BUILD_TYPE=releaseBUILD_ID=＝＝＝＝＝＝＝＝＝＝function chooseproduct()函数分析：choices=(`/bin/ls build/target/board/*/BoardConfig.mk vendor/*/*/BoardConfig.mk 2> /dev/null`)读取 build/target/board/* 目录下的板配置文件：BoardConfig.mk读取 vendor/*/*/目录下的板配置文件：BoardConfig.mkchoices 的值为：build/target/board/emulator/BoardConfig.mkbuild/target/board/generic/BoardConfig.mkbuild/target/board/sim/BoardConfig.mkvendor/marvell/littleton/BoardConfig.mk经过：for choice in ${choices[@]} do# The product name is the name of the directory containing# the makefile we found, above.prodlist=(${prodlist[@]} `dirname ${choice} | xargs basename`)done的处理，prodlist的值为：emulator generic sim littleton所以选择菜单为：Product choices are:1. emulator2. generic3. sim4. littleton如果选择 4，那么 TARGET_PRODUCT 被赋值为： littleton。
board_config_mk := /$(strip $(wildcard /$(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk /vendor/*/$(TARGET_DEVICE)/BoardConfig.mk /))
怎样添加一个模块LOCAL_PATH:= $(call my-dir)#编译静态库include $(CLEAR_VARS)LOCAL_MODULE = libhellosLOCAL_CFLAGS = $(L_CFLAGS)LOCAL_SRC_FILES = hellos.cLOCAL_C_INCLUDES = $(INCLUDES)LOCAL_SHARED_LIBRARIES := libcutilsLOCAL_COPY_HEADERS_TO := libhellosLOCAL_COPY_HEADERS := hellos.hinclude $(BUILD_STATIC_LIBRARY)
#编译动态库include $(CLEAR_VARS)LOCAL_MODULE = libhellodLOCAL_CFLAGS = $(L_CFLAGS)LOCAL_SRC_FILES = hellod.cLOCAL_C_INCLUDES = $(INCLUDES)LOCAL_SHARED_LIBRARIES := libcutilsLOCAL_COPY_HEADERS_TO := libhellodLOCAL_COPY_HEADERS := hellod.hinclude $(BUILD_SHARED_LIBRARY)
BUILD_TEST=trueifeq ($(BUILD_TEST),true)#使用静态库include $(CLEAR_VARS)LOCAL_MODULE := hellosLOCAL_STATIC_LIBRARIES := libhellosLOCAL_SHARED_LIBRARIES :=LOCAL_LDLIBS += -ldlLOCAL_CFLAGS := $(L_CFLAGS)LOCAL_SRC_FILES := mains.cLOCAL_C_INCLUDES := $(INCLUDES)include $(BUILD_EXECUTABLE)
#使用动态库include $(CLEAR_VARS)LOCAL_MODULE := hellodLOCAL_MODULE_TAGS := debugLOCAL_SHARED_LIBRARIES := libc libcutils libhellodLOCAL_LDLIBS += -ldlLOCAL_CFLAGS := $(L_CFLAGS)LOCAL_SRC_FILES := maind.cLOCAL_C_INCLUDES := $(INCLUDES)include $(BUILD_EXECUTABLE)endif # ifeq ($(WPA_BUILD_SUPPLICANT),true)
#########################local_target_dir := $(TARGET_OUT)/etc/wifi#include $(CLEAR_VARS)#LOCAL_MODULE := wpa_supplicant.conf#LOCAL_MODULE_TAGS := user#LOCAL_MODULE_CLASS := ETC#LOCAL_MODULE_PATH := $(local_target_dir)#LOCAL_SRC_FILES := $(LOCAL_MODULE)#include $(BUILD_PREBUILT)########################系统变量解析LOCAL_MODULE － 编译的目标对象LOCAL_SRC_FILES － 编译的源文件LOCAL_C_INCLUDES － 需要包含的头文件目录LOCAL_SHARED_LIBRARIES － 链接时需要的外部库LOCAL_PRELINK_MODULE － 是否需要prelink处理BUILD_SHARED_LIBRARY － 指明要编译成动态库
LOCAL_PATH - 编译时的目录$(call 目录，目录….) 目录引入操作符如该目录下有个文件夹名称 src，则可以这样写 $(call src)，那么就会得到 src 目录的完整路径
include $(CLEAR_VARS) -清除之前的一些系统变量CLEAR_VARS:= $(BUILD_SYSTEM)/clear_vars.mk在 build/core/config.mk 定义 CLEAR_VARS:= $(BUILD_SYSTEM)/clear_vars.mk通过include 包含自定义的.mk文件（即是自定义编译规则）或是引用系统其他的.mk文件（系统定义的编译规则）。
LOCAL_SRC_FILES － 编译的源文件可以是.c, .cpp, .java, .S（汇编文件）或是.aidl等格式不同的文件用空格隔开。如果编译目录子目录，采用相对路径，如子目录/文件名。也可以通过$(call 目录)，指明编译某目录下所有.c/.cpp/.java/.S/ .aidl文件.追加文件 LOCAL_SRC_FILES += 文件
LOCAL_C_INCLUDES － 需要包含的头文件目录可以是系统定义路径，也可以是相对路径. 如该编译目录下有个include目录，写法是include/*.h
LOCAL_SHARED_LIBRARIES － 链接时需要的外部共享库LOCAL_STATIC_LIBRA RIES － 链接时需要的外部外部静态LOCAL_JAVA_LIBRARIES 加入jar包
LOCAL_MODULE － 编译的目标对象module 是指系统的 native code，通常针对c,c++代码./system/core/sh/Android.mk:32:LOCAL_MODULE:= sh./system/core/libcutils/Android.mk:71:LOCAL_MODULE := libcutils./system/core/cpio/Android.mk:9:LOCAL_MODULE := mkbootfs./system/core/mkbootimg/Android.mk:8:LOCAL_MODULE := mkbootimg./system/core/toolbox/Android.mk:61:LOCAL_MODULE:= toolbox./system/core/logcat/Android.mk:10:LOCAL_MODULE:= logcat./system/core/adb/Android.mk:65:LOCAL_MODULE := adb./system/core/adb/Android.mk:125:LOCAL_MODULE := adbd./system/core/init/Android.mk:20:LOCAL_MODULE:= init./system/core/vold/Android.mk:24:LOCAL_MODULE:= vold./system/core/mountd/Android.mk:13:LOCAL_MODULE:= mountd
LOCAL_PACKAGE_NAME Java 应用程序的名字用该变量定义./packages/apps/Music/Android.mk:9:LOCAL_PACKAGE_NAME := Music./packages/apps/Browser/Android.mk:14:LOCAL_PACKAGE_NAME := Browser./packages/apps/Settings/Android.mk:8:LOCAL_PACKAGE_NAME := Settings./packages/apps/Stk/Android.mk:10:LOCAL_PACKAGE_NAME := Stk./packages/apps/Contacts/Android.mk:10:LOCAL_PACKAGE_NAME := Contacts./packages/apps/Mms/Android.mk:8:LOCAL_PACKAGE_NAME := Mms./packages/apps/Camera/Android.mk:8:LOCAL_PACKAGE_NAME := Camera./packages/apps/Phone/Android.mk:11:LOCAL_PACKAGE_NAME := Phone./packages/apps/VoiceDialer/Android.mk:8:LOCAL_PACKAGE_NAME := VoiceDialer
BUILD_SHARED_LIBRARY － 指明要编译成动态库。编译的目标，用include 操作符UILD_STATIC_LIBRARY来指明要编译成静态库。如果是java文件的话，会用到系统的编译脚本host_java_library.mk，用BUILD_PACKAGE来指明。三个编译－－－－－－－－－－－－－－－－－－－include $(BUILD_STATIC_LIBRARY)BUILD_STATIC_LIBRARY:= $(BUILD_SYSTEM)/static_library.mk－－－－－－－－－－－－－－－－－－－include $(BUILD_SHARED_LIBRARY)./build/core/config.mk:50:BUILD_SHARED_LIBRARY:= $(BUILD_SYSTEM)/shared_library.mk－－－－－－－－－－－－－－－－－－－include $(BUILD_HOST_SHARED_LIBRARY)BUILD_HOST_SHARED_LIBRARY:= $(BUILD_SYSTEM)/host_shared_library.mk－－－－－－－－－－－－－－－－－－－include $(BUILD_EXECUTABLE)build/core/config.mk:51:BUILD_EXECUTABLE:= $(BUILD_SYSTEM)/executable.mk－－－－－－－－－－－－－－－－－－－include $(BUILD_HOST_EXECUTABLE)./build/core/config.mk:53:BUILD_HOST_EXECUTABLE:= $(BUILD_SYSTEM)/host_executable.mk－－－－－－－－－－－－－－－－－－－BUILD_HOST_JAVA_LIBRARY:= $(BUILD_SYSTEM)/host_java_library.mk－－－－－－－－－－－－－－－－－－－BUILD_JAVA_LIBRARY./build/core/config.mk:58:BUILD_JAVA_LIBRARY:= $(BUILD_SYSTEM)/java_library.mk－－－－－－－－－－－－－－－－－－BUILD_STATIC_JAVA_LIBRARY 编译静态JAVA库./build/core/config.mk:59:BUILD_STATIC_JAVA_LIBRARY:= $(BUILD_SYSTEM)/static_java_library.mk－－－－－－－－－－－－－－－－－－BUILD_HOST_JAVA_LIBRARY 编译本机用的JAVA库./build/core/config.mk:60:BUILD_HOST_JAVA_LIBRARY:= $(BUILD_SYSTEM)/host_java_library.mk－－－－－－－－－－－－－－－－－－
BUILD_HOST_STATIC_LIBRARY:= $(BUILD_SYSTEM)/host_static_library.mkBUILD_HOST_SHARED_LIBRARY:= $(BUILD_SYSTEM)/host_shared_library.mkBUILD_STATIC_LIBRARY:= $(BUILD_SYSTEM)/static_library.mkBUILD_RAW_STATIC_LIBRARY := $(BUILD_SYSTEM)/raw_static_library.mkBUILD_SHARED_LIBRARY:= $(BUILD_SYSTEM)/shared_library.mkBUILD_EXECUTABLE:= $(BUILD_SYSTEM)/executable.mkBUILD_RAW_EXECUTABLE:= $(BUILD_SYSTEM)/raw_executable.mkBUILD_HOST_EXECUTABLE:= $(BUILD_SYSTEM)/host_executable.mkBUILD_PACKAGE:= $(BUILD_SYSTEM)/package.mkBUILD_HOST_PREBUILT:= $(BUILD_SYSTEM)/host_prebuilt.mkBUILD_PREBUILT:= $(BUILD_SYSTEM)/prebuilt.mkBUILD_MULTI_PREBUILT:= $(BUILD_SYSTEM)/multi_prebuilt.mkBUILD_JAVA_LIBRARY:= $(BUILD_SYSTEM)/java_library.mkBUILD_STATIC_JAVA_LIBRARY:= $(BUILD_SYSTEM)/static_java_library.mkBUILD_HOST_JAVA_LIBRARY:= $(BUILD_SYSTEM)/host_java_library.mkBUILD_DROIDDOC:= $(BUILD_SYSTEM)/droiddoc.mkBUILD_COPY_HEADERS := $(BUILD_SYSTEM)/copy_headers.mkBUILD_KEY_CHAR_MAP := $(BUILD_SYSTEM)/key_char_map.mk
＝＝＝＝＝＝＝＝＝＝＝＝LOCAL_PRELINK_MODULEPrelink利用事先链接代替运行时链接的方法来加速共享库的加载，它不仅可以加快起动速度，还可以减少部分内存开销，是各种Linux架构上用于减少程序加载时间、缩短系统启动时间和加快应用程序启动的很受欢迎的一个工具。程序运行时的动态链接尤其是重定位(relocation)的开销对于大型系统来说是很大的。动态链接和加载的过程开销很大，并且在大多数的系统上, 函数库并不会常常被更动, 每次程序被执行时所进行的链接动作都是完全相同的，对于嵌入式系统来说尤其如此。因此，这一过程可以改在运行时之前就可以预先处理好，即花一些时间利用Prelink工具对动态共享库和可执行文件进行处理，修改这些二进制文件并加入相应的重定位等信息，节约了本来在程序启动时的比较耗时的查询函数地址等工作，这样可以减少程序启动的时间，同时也减少了内存的耗用。 Prelink的这种做法当然也有代价：每次更新动态共享库时，相关的可执行文件都需要重新执行一遍Prelink才能保证有效，因为新的共享库中的符号信息、地址等很可能与原来的已经不同了，这就是为什么 android framework代码一改动，这时候就会导致相关的应用程序重新被编译。这种代价对于嵌入式系统的开发者来说可能稍微带来一些复杂度，不过好在对用户来说几乎是可以忽略的。－－－－－－－－－－－－－－－－－－－－变量设置为false那么将不做prelink操作LOCAL_PRELINK_MODULE := false默认是需要prlink的，同时需要在 build/core/prelink-linux-arm.map 中加入libhellod.so 0x96000000这个map文件好像是制定动态库的地址的，在前面注释上面有一些地址范围的信息，注意库与库之间的间隔数，如果指定不好的话编译的时候会提示说地址空间冲突的问题。另外，注意排序，这里要把数大的放到前面去，按照大小降序排序。解析 LOCAL_PRELINK_MODULE 变量build/core/dynamic_binary.mk:94:ifeq ($(LOCAL_PRELINK_MODULE),true)ifeq ($(LOCAL_PRELINK_MODULE),true)$(prelink_output): $(prelink_input) $(TARGET_PRELINKER_MAP) $(APRIORI)$(transform-to-prelinked)transform-to-prelinked定义：./build/core/definitions.mk:1002:define transform-to-prelinkeddefine transform-to-prelinked@mkdir -p $(dir $@)@echo "target Prelink: $(PRIVATE_MODULE) ($@)"$(hide) $(APRIORI) /--prelinkmap $(TARGET_PRELINKER_MAP) /--locals-only /--quiet /$< /--output $@endef./build/core/config.mk:183:APRIORI := $(HOST_OUT_EXECUTABLES)/apriori$(HOST_EXECUTABLE_SUFFIX)prelink工具不是常用的prelink而是apriori，其源代码位于” <your_android>/build/tools/apriori”参考文档：动态库优化——Prelink（预连接）技术http://www.eefocus.com/article/09-04/71629s.html
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝LOCAL_ARM_MODE := arm目前Android大部分都是基于Arm处理器的，Arm指令用两种模式Thumb(每条指令两个字节)和arm指令（每条指令四个字节）
LOCAL_CFLAGS += -O3 -fstrict-aliasing -fprefetch-loop-arrays通过设定编译器操作，优化级别，-O0表示没有优化,-O1为缺省值，-O3优化级别最高LOCAL_CFLAGS += -W -WallLOCAL_CFLAGS += -fPIC -DPICLOCAL_CFLAGS += -O2 -g -DADB_HOST=1 -Wall -Wno-unused-parameterLOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE -DSH_HISTORYLOCAL_CFLAGS += -DUSEOVERLAY2根据条件选择相应的编译参数ifeq ($(TARGET_ARCH),arm)LOCAL_CFLAGS += -DANDROID_GADGET=1LOCAL_CFLAGS := $(PV_CFLAGS)endififeq ($(TARGET_BUILD_TYPE),release)LOCAL_CFLAGS += -O2endif
LOCAL_LDLIBS := -lpthreadLOCAL_LDLIBS += -ldl
ifdef USE_MARVELL_MVEDLOCAL_WHOLE_STATIC_LIBRARIES += lib_il_mpeg4aspdecmved_wmmx2lnx lib_il_h264decmved_wmmx2lnxLOCAL_SHARED_LIBRARIES += libMrvlMVEDelseLOCAL_WHOLE_STATIC_LIBRARIES += lib_il_h264dec_wmmx2lnx lib_il_mpeg4aspdec_wmmx2lnxendif＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
本文来自博客，转载请标明出处：http://blog.csdn.net/yangzhu1982/archive/2010/09/27/5909060.aspx
