Raise out android-jsc issues in current master

[Kudo]

• Review the documentation: https://facebook.github.io/react-native
• Search for existing issues: https://github.com/facebook/react-native/issues
• Use the latest React Native release: https://github.com/facebook/react-native/releases

Environment

React Native Environment Info:
System:
OS: macOS 10.14
CPU: x64 Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz
Memory: 4.55 GB / 16.00 GB
Shell: 5.6.2 - /usr/local/bin/zsh
Binaries:
Node: 8.12.0 - ~/.nvm/versions/node/v8.12.0/bin/node
Yarn: 1.12.1 - /usr/local/bin/yarn
npm: 6.4.1 - ~/.nvm/versions/node/v8.12.0/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 12.1, macOS 10.14, tvOS 12.1, watchOS 5.1
Android SDK:
Build Tools: 21.1.2, 23.0.1, 23.0.2, 23.0.3, 24.0.0, 24.0.1, 25.0.2, 25.0.3, 26.0.0, 26.0.1, 26.0.2, 27.0.0, 27.0.1, 27.0.3, 28.0.0, 28.0.2, 28.0.3
API Levels: 17, 19, 22, 23, 25, 26, 27, 28
IDEs:
Android Studio: 3.2 AI-181.5540.7.32.5056338
Xcode: 10.1/10B61 - /usr/bin/xcodebuild

Description

There are two issues for current approach of android-jsc adoption. Related to #18754.

1. The minSdkVersion is implicitly changed to API 21.
   Running on Android < 5 will have launch crash.
   Since this android-jsc is built by NDK APP_PLATFORM 21,
   there are some unresolved symbols for Android < 5 devices. E.g. sigemptyset

2. Build break once published out as AAR format.
   Currently the dependency of android-jsc is added by this line.
   compile project(':android-jsc')
   For Android library as AAR, this dependency just tells the integrated application there is a 'android-jsc' package need to further resolved. Neither jar nor *.so will be packed into react-native AAR.
   User does not have android-jsc in their gradle projects, the dependency not found problem will cause build break.
   (Google plans to officially support fat aar in gradle plugin, which is fulfill this case to bundle all things in one AAR, but not ready yet.)

Reproducible Demo

1. The minSdkVersion is implicitly changed to API 21.
   Simply do ./gradlew :RNTester:android:app:installDebug on Android 4.1 emulator and check adb log for missing symbols.
   E.g.

         AndroidRuntime  E  FATAL EXCEPTION: create_react_context
                         E  java.lang.ExceptionInInitializerError
                         E      at com.facebook.react.jscexecutor.JSCExecutorFactory.create(JSCExecutorFactory.java:25)
                         E      at com.facebook.react.ReactInstanceManager$5.run(ReactInstanceManager.java:944)
                         E      at java.lang.Thread.run(Thread.java:856)
                         E  Caused by: java.lang.UnsatisfiedLinkError: couldn't find DSO to load: libreactnativejni.so caused by: couldn't find DSO to load: libjsc.so caused by: Can
                            not load library: reloc_library[1306]:  1138 cannot locate 'sigemptyset'...
                         E      at com.facebook.soloader.SoLoader.doLoadLibraryBySoName(SoLoader.java:703)
                         E      at com.facebook.soloader.SoLoader.loadLibraryBySoName(SoLoader.java:564)
                         E      at com.facebook.soloader.SoLoader.loadLibrary(SoLoader.java:500)
                         E      at com.facebook.soloader.SoLoader.loadLibrary(SoLoader.java:455)
                         E      at com.facebook.react.bridge.ReactBridge.staticInit(ReactBridge.java:30)
                         E      at com.facebook.react.bridge.NativeMap.<clinit>(NativeMap.java:19)
                         E      ... 3 more

2. For RNTester to use AAR dependency.
   1. Apply this patch. Assume your $HOME is /Users/foo.
   2. Build AAR and deployed at mavenLocal: ./gradlew :ReactAndroid:uploadArchives
   3. Build RNTester: ./gradlew :RNTester:android:app:assembleDebug
   4. This is the build error:

FAILURE: Build failed with an exception.

* What went wrong:
Could not resolve all files for configuration ':RNTester:android:app:debugCompileClasspath'.
> Could not find react-native:android-jsc:unspecified.

[react-native-bot]

We are automatically closing this issue because it does not appear to follow any of the provided issue templates.

Please make use of the bug report template to let us know about a reproducible bug or regression in the core React Native library.

If you'd like to propose a change or discuss a feature request, there is a repository dedicated to Discussions and Proposals you may use for this purpose.

[gengjiawen]

I will take a look at RNTester build tormorrow, I have tested it, maybe I miss something.

[gengjiawen]

For the first, the miniSDK it's still 16, I am using a fork of buck when build it.

[Kudo]

@gengjiawen The problem of minSDK is caused by this line in fact.
app_platform = android-21
If not specified this, BUCK will by default use android-16.

For APP_PLATFORM, there is some reference on stackoverflow.
Even minSdkVersion was not changed, the actual expected API need to reference APP_PLATFORM.
During apk installation, Android does not have information about what APP_PLATFORM specified.
It will crash when there are unresolved symbols at runtime.
That's why I said the minSdkVersion is implicitly changed to 21.

[gengjiawen]

Yes, I know that. I only change app_platform when I bundle 64bit.

[hey99xx]

So then did you use facebookarchive/android-jsc#30 to create the android-jsc.aar that you checked into this project, or you only used to create 64bit .so files, then created the .aar by hand by adding all of regular 32bit .so files and the new 64bit .so files?

[gengjiawen]

I put the buck patch link in pr description, and want to update the buck version later, but buck team seems not care this issue.

[Kudo]

@gengjiawen FYI, BUCK support an option app_platform_per_cpu_abi.
This is from facebook/buck#1889 which is to fix your opened issue.
And that's I used in https://github.com/Kudo/android-jsc/blob/clang/.buckconfig#L3 in fact.

[gengjiawen]

@Kudo Thanks. So the master branch actually won't crash on pre-sdk-21 device.
But I am intended to replace it with jsc-android-buildscript after react-native-community/jsc-android-buildscripts#66 got merged.

cc @DanielZlotin @dulmandakh @kelset

[Kudo]

@gengjiawen How did you test that master branch code will not crash on pre-sdk-21 devices?
Because I could reproduced the problem on Android 4.1 emulator.

One way to check the unresolved symbols:

1. Dump undefined symbols from your *.so (unzip from android-jsc.aar)
   ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-nm -D -u jni/armeabi-v7a/libjsc.so
2. Dump libc.so symbols
   ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-nm -D ndk-bundle/platforms/android-16/arch-arm/usr/lib/libc.so
3. Check if libjsc.so undefined symbols exists in libc.so or not. And there are actually some undefined symbols. E.g. sigemptyset or log2.
   (Note that there are a few symbols not expected in libc.so, such as C++ symbols. However, you can differentiate them as C++ symbol name are mangled.)

Also agreed to migrate jsc-android-buildscript. Maybe #22263 (comment) will fix the issue right now.