Android.mk to Android.bp conversion

[Shakir Mohammed]

Hi,

Am trying to convert all my Android.mk files which are actually designed in hierarchical manner using several Android.mk files. I have total 60 Android.mk files which are linked to each other. Am using a global make file to provide configuration variables to each make files.

Currently I need to convert it to Android.bp so that I could use "vndk", "vendor_available", etc. Am facing "Internal error: not yet implemented" error in Android 8.1 for some modules and it crashed total Android make/mmm system.

And then I have shifted to Android 9. Now am getting all properly but am in slight confusion on how to get proper tutorial on Android.bp generation. Some of my requirements are as follows,

# How to use LOCAL_JNI_SHARED_LIBS in android_app module, which is not getting converted using androidmk tool.

# Perform condition checks using some custom variable with custom option in each modules.

# How not to jump in to some subdirectories, which I haven't specified in subdir variable.

# What is the difference between subdir and optional_subdir.

# How to pass some varibles between bp files. Some variables are getting passed whereas others are not.

[Dan Willemsen]

Comments inline:

On Tue, May 28, 2019 at 11:21 AM Shakir Mohammed <shaki...@gmail.com> wrote:

Hi,

Am trying to convert all my Android.mk files which are actually designed in hierarchical manner using several Android.mk files. I have total 60 Android.mk files which are linked to each other. Am using a global make file to provide configuration variables to each make files.

We've found that variables generally haven't been that useful -- careful application of (cc|java)_defaults, and/or a bit of refactoring goes a long way to not needing them at all. Plus, that simplifies how many combinations of builds that you need to run in your CI systems to ensure that a change won't break a build (in addition to making your code easier to understand).

Currently I need to convert it to Android.bp so that I could use "vndk", "vendor_available", etc.

These concepts only exist for the cc_* (C/C++) rules, they don't apply to Java-based rules. 

"vndk" is something that really should only be set by the upstream project, as it's defining an ABI guarantee between different distributable pieces.

"vendor_available" is mostly just a shortcut to define a module twice, once with vendor: true, and once without. It's possible to emulate that in Make.

 

Am facing "Internal error: not yet implemented" error in Android 8.1 for some modules and it crashed total Android make/mmm system. And then I have shifted to Android 9.

Java support in Android.bp was very broken in 8.1 -- it was an old prototype while we focused on the cc_* modules. If I remember correctly, there was minimal support for Java in Android.bp in 9, but it's much much better in Android Q (with a few advancements in master -- in particular, JNI support for android_app didn't make it in for Q, but should mostly work in AOSP master).

 

Now am getting all properly but am in slight confusion on how to get proper tutorial on Android.bp generation. Some of my requirements are as follows,

# How to use LOCAL_JNI_SHARED_LIBS in android_app module, which is not getting converted using androidmk tool.

In master, you can use the jni_libs property on android_app: https://ci.android.com/builds/submitted/5612488/linux/latest/java.html#android_app.jni_libs

In earlier versions of Android, you'll need to stick with Android.mk for that module.

 

# Perform condition checks using some custom variable with custom option in each modules.

We really encourage you not to do condition checks, they make your build significantly more complicated. Here's our FAQ entry:

https://android.googlesource.com/platform/build/soong/+/master#how-do-i-write-conditionals

If you want/need to ignore this advice, we do support passing through specific variables from Make to Go, where you'd need to write your own soong module type in Go: https://android.googlesource.com/platform/build/soong/+/0fe7866897b177f2bf7ec934c5615a2b48e48a23. There are a number of examples of soong plugins in the tree, but no public ones that use the SOONG_CONFIG_* feature -- they're usually doing something special, or making changes based on environment variables (which aren't useful for device-specific configuration, but for certain temporary cases can be useful).

 

# How not to jump in to some subdirectories, which I haven't specified in subdir variable.

# What is the difference between subdir and optional_subdir.

As of Android 9 (I don't think it made 8.1), all Android.bp files found in the tree will always be loaded no matter what, there is no way to conditionally load the files.

As a replacement for conditional loading, we added the concept of soong namespaces, so that you can define two modules of the same name, as long as the two namespaces that they're defined within aren't selected by the current device. We've got some (minimal) documentation here: https://android.googlesource.com/platform/build/soong/+/master/README.md#name-resolution. Many of the devices in AOSP now use this.

 

# How to pass some varibles between bp files. Some variables are getting passed whereas others are not.

They're passed down between bp files based on the filesystem layout, so if you define a variable in foo/Android.bp, foo/bar/Android.bp and foo/a/b/Android.bp will be able to read it, but baz/Android.bp will not see it. (It will be considered read-only after it has been used within the Android.bp that defined it, and always read-only in other Android.bp files).

- Dan

 

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[Shakir Mohammed]

This was totally helpful knowlege, but still I recommend you to provide more information of soong documentation. It's better to have an FAQ or small documentation on manual convertion of Android.mk to Android.bp. Am happy with Android 9, since it gives more information on bugs found in bp files.

- Shakir

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