前期准备终于做完了，设置好了环境变量，提供了所需的函数，相关文件也已经到位，所有这一且都是为了最终的make。
首先是Makefile的包含关系：
Makefile
build/core/main.mk
build/core/help.mk
build/core/config.mk
build/core/pathmap.mk
buildspec.mk
device/softwinner/apollo-cubieboard/BoardConfig.mk
device/softwinner/crane-common/BoardConfigCommon.mk
build/core/combo/select.mk
build/core/combo/HOST_linux-x86.mk
build/core/combo/TARGET_linux-arm.mk
build/core/combo/javac.mk
build/core/dumpvar.mk
build/core/cleanbuild.mk
很多和 clean 相关的 Makefile，这里不再列出
out/versions_checked.mk
发现我错了，这简直是个无底洞啊，后面分析的时候有些Makefile就不展开了或是只局部分析。想到用脚本来打印这个列表的，但是发现include Makefile时，有些路径包含变量，不得不放弃了。 其实我更关心的是和硬件相关的Makefile。
make命令是在 “android” 目录下执行的，依照make的用法，在该目录下找到 Makefile 文件：
Makefile
1 ### DO NOT EDIT THIS FILE ### 2 include build/core/main.mk 3 ### DO NOT EDIT THIS FILE ###
只有一行有效语句，就是包含了 “build/core/main.mk” 文件，顺藤摸瓜：
build/core/main.mk
1 # Only use ANDROID_BUILD_SHELL to wrap around bash. 2 # DO NOT use other shells such as zsh. 3 ifdef ANDROID_BUILD_SHELL 4 SHELL := $(ANDROID_BUILD_SHELL) 5 else 6 # Use bash, not whatever shell somebody has installed as /bin/sh 7 # This is repeated in config.mk, since envsetup.sh runs that file 8 # directly. 9 SHELL := /bin/bash 10 endif
对shell类型有严格的限制，只能用 “$(ANDROID_BUILD_SHELL)” 或 “bash”，这样可以避免一些兼容性问题。
build/core/main.mk
1 # this turns off the suffix rules built into make 2 .SUFFIXES: 3 4 # this turns off the RCS / SCCS implicit rules of GNU Make 5 % : RCS/%,v 6 % : RCS/% 7 % : %,v 8 % : s.% 9 % : SCCS/s.%
见注释，关闭一些规则，但现在还没弄懂（TODO）。
build/core/main.mk
1 # If a rule fails, delete $@. 2 .DELETE_ON_ERROR:
如果规则的命令执行错误，将删除已经被修改的目标文件。
build/core/main.mk
1 # check for broken versions of make 2 ifeq (0,$(shell expr $$(echo $(MAKE_VERSION) | sed "s/[^0-9.].*//") = 3.81)) #只能使用make 3.81 3 $(warning ********************************************************************************) 4 $(warning * You are using version $(MAKE_VERSION) of make.) 5 $(warning * Android can only be built by version 3.81.) 6 $(warning * see http://source.android.com/source/download.html) 7 $(warning ********************************************************************************) 8 $(error stopping) 9 endif 10 11 TOP := . 12 TOPDIR := 13 14 BUILD_SYSTEM := $(TOPDIR)build/core
build/core/main.mk
1 # This is the default target. It must be the first declared target. 2 .PHONY: droid 3 DEFAULT_GOAL := droid 4 $(DEFAULT_GOAL): 5 6 # Used to force goals to build. Only use for conditionally defined goals. 7 .PHONY: FORCE 8 FORCE:
默认目标为 “droid”，没有什么依赖，直接执行下面的命令。
build/core/main.mk
1 # Targets that provide quick help on the build system. 2 include $(BUILD_SYSTEM)/help.mk
build/core/help.mk
1 ifeq ($(MAKECMDGOALS),help) 2 dont_bother := true 3 endif 4 ifeq ($(MAKECMDGOALS),out) 5 dont_bother := true 6 endif 7 8 .PHONY: help 9 help: 10 @echo 11 @echo "Common make targets:" 12 @echo "----------------------------------------------------------------------------------" 13 @echo "droid Default target" 14 @echo "clean (aka clobber) equivalent to rm -rf out/" 15 @echo "snod Quickly rebuild the system image from built packages" 16 @echo "offline-sdk-docs Generate the HTML for the developer SDK docs" 17 @echo "doc-comment-check-docs Check HTML doc links & validity, without generating HTML" 18 @echo "libandroid_runtime All the JNI framework stuff" 19 @echo "framework All the java framework stuff" 20 @echo "services The system server (Java) and friends" 21 @echo "help You're reading it right now" 22 23 .PHONY: out 24 out: 25 @echo "I'm sure you're nice and all, but no thanks."
提供一些帮助。当然这个目标不手动调用是不会执行的，这里不做分析。
build/core/main.mk
1 # Set up various standard variables based on configuration 2 # and host information. 3 include $(BUILD_SYSTEM)/config.mk