android - 构建 AOSP 5.1 时出现 API 更改错误

Question

目前正在尝试构建 android-5.1.0_r5。我检查了来源并没有做任何修改。但是，在编译时出现以下错误。

Checking API: checkpublicapi-current
out/target/common/obj/PACKAGING/public_api.txt:20: error 5: Added public field android.Manifest.permission.BACKUP
out/target/common/obj/PACKAGING/public_api.txt:82: error 5: Added public field android.Manifest.permission.INVOKE_CARRIER_SETUP
out/target/common/obj/PACKAGING/public_api.txt:106: error 5: Added public field android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE
out/target/common/obj/PACKAGING/public_api.txt:116: error 5: Added public field android.Manifest.permission.RECEIVE_EMERGENCY_BROADCAST

******************************
You have tried to change the API from what has been previously approved.

To make these errors go away, you have two choices:
   1) You can add "@hide" javadoc comments to the methods, etc. listed in the
      errors above.

   2) You can update current.txt by executing the following command:
         make update-api

      To submit the revised current.txt to the main Android repository,
      you will need approval.
******************************

比较公共(public) api txt 文件确实显示出差异。

diff frameworks/base/api/current.txt out/target/common/obj/PACKAGING/public_api.txt 
19a20
>     field public static final java.lang.String BACKUP = "android.permission.BACKUP";
80a82
>     field public static final java.lang.String INVOKE_CARRIER_SETUP = "android.permission.INVOKE_CARRIER_SETUP";
103a106
>     field public static final java.lang.String READ_PRIVILEGED_PHONE_STATE = "android.permission.READ_PRIVILEGED_PHONE_STATE";
112a116
>     field public static final java.lang.String RECEIVE_EMERGENCY_BROADCAST = "android.permission.RECEIVE_EMERGENCY_BROADCAST";

但是，我无法弄清楚这些额外的公共(public)字段是从哪里来的。有什么想法吗？

Answer 1

如果你什么都没碰，不要做'make update-api'。还有其他 api 来自 frameworks/base/res/AndroidManifest.xml 被 aapt 严重解析，它使用有缺陷的 system/core/libcore/String8.cpp@@removeAll() 他们使用 memcpy 但应该是内存中重叠字符串的 memmove。

这是最新的 Debian (sid) 或 Ubuntu(16 或 15)构建机器上的问题。这是 libcore/String8.cpp 中的谷歌错误。修复在这里: https://android.googlesource.com/platform/system/core/+/dd060f01f68ee0e633e9cae24c4e565cda2032bd

这个人找到了它(Michael Scott)，也许其他一些人也找到了。这是他的调查:https://plus.google.com/+hashcode0f/posts/URHo3hBmfHY

Living on the Edge (of Ubuntu) ... can be painful!

I've been running Ubuntu 15.04 for a while now. It's been great having a very current kernel alongside the latest improvements from Ubuntu and Debian. (My past post on using zRAM ramdisk is one example).

However, having the newest greatest toys also has it's downsides. I recently spent 4 days troubleshooting a build break in Android which started some time after March 25th. I'm guessing I updated packages or inadvertently changed my glibc version.

The outcome was a build error during the checkapi stage of Android build:

Install: /out/mydroid-ara/host/linux-x86/bin/apicheck Checking API: checkpublicapi-last Checking API: checkpublicapi-current /out/mydroid-ara/target/common/obj/PACKAGING/public_api.txt:20: error 5: Added public field android.Manifest.permission.BACKUP /out/mydroid-ara/target/common/obj/PACKAGING/public_api.txt:82: error 5: Added public field android.Manifest.permission.INVOKE_CARRIER_SETUP /out/mydroid-ara/target/common/obj/PACKAGING/public_api.txt:106: error 5: Added public field android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE /out/mydroid-ara/target/common/obj/PACKAGING/public_api.txt:116: error 5: Added public field android.Manifest.permission.RECEIVE_EMERGENCY_BROADCAST

**************************** You have tried to change the API from what has been previously approved.

To make these errors go away, you have two choices: 1) You can add "@hide" javadoc comments to the methods, etc. listed in the errors above.

2) You can update current.txt by executing the following command: make update-api

  To submit the revised current.txt to the main Android repository,
  you will need approval.

---

This occurred on both of my Ubuntu 15.04 boxes and was present when when build AOSP android-5.0.2_r1 and android-5.1.0_r1.

For those of you who are unfamiliar with this portion of the Android build, the Android framework exports all of the public portions of the API and makes sure that the current build matches up with what's located under frameworks/base/api/current.txt. It does this by parsing frameworks/base/res/AndroidManifest.xml and any of the current device's overlay .xml files and processes items marked with various flags in the comments above them:@SystemApi, @hide, etc. This parsing and processing portion of the checkapi stage is done by a binary "aapt" (Android Asset Packagng Tool). It's source is located under frameworks/base/tools/aapt.

I started by checking for upstream fixes to the platform/build or platform/frameworks/base projects. After striking out, I began debugging the android build via the use of: "make checkapi showcommands" and then manually running the commands with "strace" to see how each binary was involved and what output it generated.

After the first few hours of debugging, it became apparent that out/target/common/obj/APPS/frameworks-res_intermediates/src/android/Manifest.java file had comments which were being corrupted when aapt was generating it. I was able to make some manual changes to the AndroidManifest.xml file and get the build to pass (removing extra portions of the comments).

Digging deeper via strace and then looking at various static link sources, I found that during the AndroidManifest.xml comments processing the @SystemApi token was being filtered out via a String8.removeAll("@SystemApi") function call. Experimentally, I removed this part of the processing. Lo and Behold! The build worked. Taking a closer look at the removeAll function, I was able to pin point a memcpy function as the part of the function which was causing corruption.

I then researched memcpy a bit and noted that you are not supposed to use memcpy on overlapping memory addresses, instead memmove was preferred, because it makes a copy of the source prior to any changes being made to the destination. After changing the use of memcpy to memmove the build was fixed and all was well with the world!

As a good player in the open source world, I immediately thought I should upstream this incredible feat of debugging to the master branch of system/core. BUT, alas! The fix has been in the master branch since November 11th 2014! And hasn't been brought into any of the current development tags! grumble https://android.googlesource.com/platform/system/core/+/dd060f01f68ee0e633e9cae24c4e565cda2032bd

I've since contacted the Google team about this change and let them know of my experience in hopes that we may yet see this patch in future release tags of Android.

Conclusion: apparently glibc is undergoeing some changes and some of those have now filtered onto my Ubuntu boxes. Where previously the memcpy usage was incorrect but still usable, it now causes the build break I was seeing.

If you see this kind of error in your Android builds, and you're on a newish version of Ubuntu or Debian distrobution, you may want to try this simple patch and see if it helps.

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自大!