Bundling with "libc++_shared.so"

[kwek20]

Hi!

Ive been trying to use cargo ndk with a bigger rust library.
The library is generating Java JNI bindings through a generator called "flapigen". (So its not a direct cmake project)
After building the APK with gradlew aR, which triggers gradlew jar (For making the Java side of the generated bindings) and a gradle task for running cargo ndk -t ${arch} -o ${libsPath} build --release.

Yea.. a bit of a trip :D But in the end the APK gets generated, and properly links with the generated jar.
When i install the APK, it also loads the native library correctly, however, one of the native parts needs libc++_shared.so (for i think a rust dependency, im in a bit over my head!).

According to .. the internet it should compile with that .so when i set APP_STL:=c++_shared in Application.mk, or

android {
    defaultConfig {
        ...
        externalNativeBuild {
            ndkBuild {
                arguments  "-DAPP_STL=c++_shared", "-DANDROID_TOOLCHAIN=clang"
            } 
        }
    }
}

However, inspecting the APK, it doesnt have it incuded.

The error: Caused by: java.lang.UnsatisfiedLinkError: dlopen failed: library "libc++_shared.so" not found: needed by /data/app/~~1wFPIY2YxMCnGcnEq7pBpA==/org.example-MjRM-ZMHEp1x9fjGfZEjrA==/base.apk!/lib/arm64-v8a/libexample_java.so in namespace classloader-namespace.
Ive tried building on NDK 20, 21 and 23, and targeting SDK 27, 28 and 29 to no avail.
Using gradle-6.7.1, if it makes a difference

        classpath 'com.android.tools.build:gradle:4.2.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.3.31"

Any pointers you can give me?
Thank you!

[MarijnS95]

For the record this is something that cargo-apk already deals with:

https://github.com/MarijnS95/android-ndk-rs/blob/670376712a2581af0c9c208e6a0ed39d7ff4fc7a/ndk-build/src/readelf.rs#L42-L45

Unfortunately cargo-apk cannot easily compile native binaries without the surrounding APK (see rust-mobile/ndk#147), which is why I envision cargo-ndk using ndk-build (cargo-apk's core) as backend: #28.

[rahimklaber]

Hey, did you guys figure this out? I was initially initially using https://github.com/rust-mobile/xbuild and extracting the libs from the resulting apk/aab manually. However xbuild does not support x86.

On second thought, maybe i don't need x86 support as it seems to be extremely rare.

[MarijnS95]

@rahimklaber xbuild and cargo-apk/ndk-build pull these directly from the NDK, so you don't even need to go through the hassle of running those tools and extracting the libs manually:

a@b:~/Android/Sdk/ndk/25.1.8937393 $ fd _shared
toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/aarch64-linux-android/libc++_shared.so
toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/libc++_shared.so
toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/i686-linux-android/libc++_shared.so
toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/x86_64-linux-android/libc++_shared.so

That said I was under the impression xbuild supports at least x86 or more specifically x86_64, strangely x86/i686 (as well as 32-bit arm support) is commented out...

[rahimklaber]

Thanks!