Android6.0源码编译教程
Android6.0源码编译教程
第一次成功编译了Android的源码，记录一下。
回忆
这是我第二次尝试去编译Android的源码，第一次是半年前，当时刚刚拿到去腾讯实习的Offer，虽然当时会一些Android开发的皮毛知识，但想到将来可能长期从事这个领域，就一时踌躇满志，打算先研究一下Android源码。
当时是按照网上最常见的方法，通过repo工具来下载代码，结果下了30G左右，似乎下载了所有版本，而且网络似乎有中断，都不知道下载的代码是否完整，再加上120G固态硬盘实在不够用，所以不了了之。
寒假回来，感觉自己最近一段时间过于沉迷游戏，毕设进度不及预期，博客也多荒废了。明年打算去公司继续实习，所以还是早回正轨吧！
下载源码
这次看到一篇博客，给了我一些新的启发，博主将Android6.0的源码打包，然后切割成10个700M左右的文件放在百度网盘，所以我只需要下载之后再合并这些文件就行了：
➜ 下载 ls
Android6_r1_aa
Android6_r1_ab
Android6_r1_ac
Android6_r1_ad
Android6_r1_ae
Android6_r1_af
Android6_r1_ag
Android6_r1_ah
Android6_r1_ai
Android6_r1_aj
通过：
➜ 下载 cat Android6_r1_*>Android6_r1.tgz
便可以合并这些文件，值得一提的是：由于文件下载过程中可能损坏（确实存在，有一个文件用浏览器老是下载失败，我便用手机客户端下载之后拷贝过来，就发现合并之后解压失败，检查之后发现这个文件的md5值已经变了），所以需要通过md5检验。通过md5sum命令查看每个文件的md5值，并与随同下载的hash.txt对比：
➜ 下载 cat hash.txt
a4129f5d2d6a8293ee3ee3ed4343f0fd Android6_r1_aa
e601f1239c0f60895cc6b9199b1cd7d1 Android6_r1_ab
af2d9e653a51072031ce40b62791c2de Android6_r1_ac
482866559a4d6a8533411e512436363c Android6_r1_ad
cef15f072f6d52243d9dea126c22f794 Android6_r1_ae
457979779748dae9f5f4f3c99db04826 Android6_r1_af
7ca217b1fd60a41c7ff9b7e294864fe3 Android6_r1_ag
5b468da830ef51fdd5f35d5d8ac72bd1 Android6_r1_ah
ba80f4acf5f61b1b82d3c1ba6ba702c1 Android6_r1_ai
4350d1bb74589ad03735279421dced92 Android6_r1_aj
cat Android6_r1_*>M.tgz
23858108e95095dc8d0292505a0d28e4 M.tgz
➜ 下载
构建环境
这一步比较看运气，之前用Ubuntu12就是各种冲突，这次我用的是LinuxMint18 Xfce，而AOSP的官方说明只说了Ubuntu各版本的依赖安装，由于LinuxMint是Ubuntu的近亲，所以我就直接按照最新版本（>=Ubuntu15）来安装依赖，所幸一次通过：
sudo apt-get install git-core gnupg flex bison gperf build-essential zip curl zlib1g-dev gcc-multilib g++-multilib libc6-dev-i386 lib32ncurses5-dev x11proto-core-dev libx11-dev lib32z-dev ccache libgl1-mesa-dev libxml2-utils xsltproc unzip
开始编译
make之后，日常报错，第一次错误很好解决：
You are attempting to build with the incorrect version
of java.
Your version is: openjdk version "1.8.0_151" OpenJDK Runtime Environment (build 1.8.0_151-8u151-b12-0ubuntu0.16.04.2-b12) OpenJDK 64-Bit Server VM (build 25.151-b12, mixed mode).
The required version is: "1.7.x"
Please follow the machine setup instructions at
https://source.android.com/source/initializing.html
由于最新版本已经不能下载openjdk7，所以需要重新设置一下源，下载之后重写一下当前终端的环境变量（一次使用无污染）：
➜ Android_r1 export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64
➜ Android_r1 export PATH=$JAVA_HOME/bin:$PATH
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
➜ Android_r1 java -version
java version "1.7.0_95"
OpenJDK Runtime Environment (IcedTea 2.6.4) (7u95-2.6.4-3)
OpenJDK 64-Bit Server VM (build 24.95-b01, mixed mode)
最新版本的LinuxMint可能无法直接安装jdk1.7，需要手动设置源：
sudo add-apt-repository ppa:openjdk-r/ppa
sudo apt-get update
sudo apt-get install openjdk-7-jdk
注意不要用
sudo update-alternatives --config java
sudo update-alternatives --config javac
来指定版本，否则可能出现
Lock.ReentrantReadWriteLock.ReadLock(ReentrantReadWriteLock)
prebuilts/sdk/api/23.txt:53035: error 9: Removed public constructor java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock.ReentrantReadWriteLock.WriteLock(ReentrantReadWriteLock)
prebuilts/sdk/api/23.txt:53074: error 9: Removed public constructor java.util.jar.Attributes.Name.Attributes.Name(String)
prebuilts/sdk/api/23.txt:54404: error 9: Removed public constructor javax.crypto.spec.PSource.PSpecified.PSource.PSpecified(byte)
******************************
You have tried to change the API from what has been previously released in
an SDK. Please fix the errors listed above.
******************************
build/core/tasks/apicheck.mk:46: recipe for target 'out/target/common/obj/PACKAGING/checkpublicapi-last-timestamp' failed
make: *** [out/target/common/obj/PACKAGING/checkpublicapi-last-timestamp] Error 38
##### make failed to build some targets (05:10 (mm:ss)) ####
第二个问题比较棘手：
clang: error: linker command failed with exit code 1 (use -v to see invocation)
build/core/host_shared_library_internal.mk:44: recipe for target 'out/host/linux-x86/obj32/lib/libnativehelper.so' failed
make: *** [out/host/linux-x86/obj32/lib/libnativehelper.so] Error 1
但StackOverflow上也能找到答案（具体参见链接），但是直接按照答案还是失败了，再参考其他博客后，我覆盖了ld文件，原来的保留为ld.old，并修改/art/build/Android.common_build.mk为：
## Host.
ART_HOST_CLANG := false
ifneq ($(WITHOUT_HOST_CLANG),true)
## By default, host builds use clang for better warnings.
ART_HOST_CLANG := false
endif
（原答案是将判断语句中的true修改为false）
最终，这份10G左右的源码在我的老电脑（500G机械硬盘，4G内存，i5处理器）上编译了大概4个小时终于成功了。
启动模拟器
这个部分原博主说的不是很清楚，这里详细说一下。在编译完成后，所有的结果文件都在out文件夹，有26G：
➜ Android_r1 du . -h --max-depth=1
16M ./build
29M ./bionic
28M ./art
108K ./abi
880K ./pdk
900K ./platform_testing
26G ./out
108M ./hardware
5.7M ./bootable
89M ./device
28M ./docs
2.6G ./external
30M ./system
493M ./cts
196K ./libnativehelper
83M ./ndk
276M ./developers
11M ./dalvik
31M ./sdk
6.5G ./prebuilts
52M ./libcore
307M ./development
1.5G ./frameworks
686M ./tools
401M ./packages
40G.
打开一个新终端，首先要设置运行环境，然后选择平台：
➜ Android_r1 source build/envsetup.sh
build/envsetup.sh:573: command not found: complete
WARNING: Only bash is supported, use of other shell would lead to erroneous results
including device/asus/deb/vendorsetup.sh
including device/asus/flo/vendorsetup.sh
including device/asus/fugu/vendorsetup.sh
including device/generic/mini-emulator-arm64/vendorsetup.sh
including device/generic/mini-emulator-armv7-a-neon/vendorsetup.sh
including device/generic/mini-emulator-mips/vendorsetup.sh
including device/generic/mini-emulator-x86_64/vendorsetup.sh
including device/generic/mini-emulator-x86/vendorsetup.sh
including device/htc/flounder/vendorsetup.sh
including device/lge/hammerhead/vendorsetup.sh
➜ Android_r1 lunch
You're building on Linux
Lunch menu... pick a combo:
1. aosp_arm-eng
2. aosp_arm64-eng
3. aosp_mips-eng
4. aosp_mips64-eng
5. aosp_x86-eng
6. aosp_x86_64-eng
7. aosp_deb-userdebug
8. aosp_flo-userdebug
9. full_fugu-userdebug
10. aosp_fugu-userdebug
11. mini_emulator_arm64-userdebug
12. m_e_arm-userdebug
13. mini_emulator_mips-userdebug
14. mini_emulator_x86_64-userdebug
15. mini_emulator_x86-userdebug
16. aosp_flounder-userdebug
17. aosp_hammerhead-userdebug
18. aosp_hammerhead_fp-userdebug
19. aosp_shamu-userdebug
Which would you like? [aosp_arm-eng]
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=6.0
TARGET_PRODUCT=aosp_arm
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a
TARGET_CPU_VARIANT=generic
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.4.0-21-generic-x86_64-with-LinuxMint-18-sarah
HOST_BUILD_TYPE=release
BUILD_ID=MRA58K
OUT_DIR=out
============================================
➜ Android_r1 which emulator
/home/vimerzhao/SourceCode/Android_r1/prebuilts/android-emulator/linux-x86_64/emulator
➜ Android_r1 which android
/home/vimerzhao/SourceCode/Android_r1/prebuilts/devtools/tools/android
➜ Android_r1 echo $ANDROID_PRODUCT_OUT
/home/vimerzhao/SourceCode/Android_r1/out/target/product/generic
这时候输入emulator就可以看到效果了：
两点遗憾
第一点，觉得编译期间输出的log对于理解源码还是很有帮助的，可惜没保存下来。第二点，打算烧录到真机的时候才发现编译之前要配置相应的驱动，这次也只好到此为止。
