Rust panic - android context was not initialized: Flutter-Rinf-Rust [ hub -> rodio -> cpal -> oboe -> ndk-context ]

[sergey-serov]

Good Day!
Several days were spent to trying to combine rinf+rodio on Android.

I had been reading and rereading issues about this known difficulties, like:

• Using cpal in a library for android causes an error RustAudio/cpal#720
• Problems building Android apk because of a third-party crate that depends on libc++ #280

But without success.

On Linux everything is OK.

The error with shared c++ lib was successfully resolved.
But Android context is not friendly during long time:

Rust panic at ndk-context-0.1.1/src/lib.rs:72:30
and android context was not initialized

all the time...

The way seems to be:
rodio -> cpal -> oboe -> ndk-context

I found the explanation and it seems to be very near to true:
https://cjycode.com/flutter_rust_bridge/guides/how-to/ndk-init

"Typically, in a normal application, the Android JVM would System.loadLibrary() the library through the Activity inside the JVM. It looks for symbols related to the JNI and executes them in accordance with the JNI standard. This would initialize the ndk_context normally via JNI_OnLoad. However, using the DartVM this step is skipped while loading the library, as the DartVM is not the JVM. "

There are also some suggestions but they are not applicable for my case.

Also, I tried to insert this snippet:

#[cfg(target_os = "android")]
#[no_mangle]
pub extern "C" fn JNI_OnLoad(vm: jni::JavaVM, res: *mut std::os::raw::c_void) -> jni::sys::jint {
    use std::ffi::c_void;

    let vm = vm.get_java_vm_pointer() as *mut c_void;
    unsafe {
        ndk_context::initialize_android_context(vm, res);
    }
    jni::JNIVersion::V6.into()
}

Before and after "rinf::write_interface!();"
And in several places in my rust files with the same effect.

Result of all my experiments is the same: flutter app works fine (both on Android device via USB and Emulator)
BUT all rust functionality is inaccessible.

And on Linux everything is perfect! :)

P.S.: I cloned crates "cpal" and "ndk-context" and tried to debug place with Android context initialization.
And face with new difficulties - it is really not easy to debug such application: "flutter-rinf-rust" on android.

[temeddix]

Hi @sergey-serov :) Thank you for the report.

I'm aware that there are issues related to dynamic library symbols on Android. The cause is usually the different behaivor of dart:ffi between platforms, specifically how RTLD_LOCAL and RTLD_GLOBAL are handled when calling DynamicLibrary.open in Dart.

In my opinion, the code snippet you provided

#[cfg(target_os = "android")]
#[no_mangle]
pub extern "C" fn JNI_OnLoad(vm: jni::JavaVM, res: *mut std::os::raw::c_void) -> jni::sys::jint {
    use std::ffi::c_void;

    let vm = vm.get_java_vm_pointer() as *mut c_void;
    unsafe {
        ndk_context::initialize_android_context(vm, res);
    }
    jni::JNIVersion::V6.into()
}

or similar might be able to help us, and I'm open to putting this code inside the rinf crate. I don't think the place we're putting this code matters.

Result of all my experiments is the same: flutter app works fine (both on Android device via USB and Emulator)
BUT all rust functionality is inaccessible.

Does this mean the panic still occurs when trying to call rodio functions?

[sergey-serov]

Hello @temeddix Thank you for answer!!!

Does this mean the panic still occurs when trying to call rodio functions?

1). Yes.

$ flutter run

...
Compiling bin/build_tool_runner.dart to kernel file bin/build_tool_runner.dill.
INFO: Precompiled binaries are disabled
INFO: Building hub for aarch64-linux-android
INFO: Building hub for i686-linux-android
INFO: Building hub for x86_64-linux-android
Running Gradle task 'assembleDebug'...                             20.2s
✓ Built build/app/outputs/flutter-apk/app-debug.apk
Installing build/app/outputs/flutter-apk/app-debug.apk...           6.6s
I/flutter (17046): [IMPORTANT:flutter/shell/platform/android/android_context_vk_impeller.cc(60)] Using the Impeller rendering backend (Vulkan).
I/flutter (17046): **A panic occurred in Rust.**
I/flutter (17046): panicked at /home/sergey/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/**ndk-context-0.1.1/src/lib.rs:72:30:**
I/flutter (17046): **android context was not initialized**
...

Error disappears after commenting code exactly from these lines:

```rust
let (_stream, stream_handle) = OutputStream::try_default().expect("cpal config problem");
let sink = rodio::Sink::try_new(&stream_handle).expect("sink creating problem");

But, expect() not runs here, I mean that I don't see "cpal config problem" or "sink creating problem" messages.

2). Also I have cloned related crates and defined local versions in its Cargo.toml to research problem places.
And on this way: "rodio -> cpal -> oboe" I got a lot of errors such as:

Compiling bin/build_tool_runner.dart to kernel file bin/build_tool_runner.dill.
INFO: Precompiled binaries are disabled
INFO: Building hub for x86_64-linux-android
SEVERE: ================================================================================
SEVERE: Cargokit BuildTool failed with error:
SEVERE: --------------------------------------------------------------------------------
SEVERE: External Command: rustup "run" "stable" "cargo" "build" "--manifest-path" "/home/sergey/Forge/b_music/native/hub/Cargo.toml" "-p" "hub" "--target" "x86_64-linux-android" "--target-dir" "/home/sergey/Forge/b_music/build/rinf/build"
SEVERE: Returned Exit Code: 101
...
SEVERE: warning: oboe-sys@0.6.1: clang++: error: no such file or directory: 'oboe/src/aaudio/AAudioLoader.cpp'
SEVERE: warning: oboe-sys@0.6.1: clang++: error: no input files
SEVERE: warning: oboe-sys@0.6.1: ToolExecError: Command "/home/sergey/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++" "-O0" "-DANDROID" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-2" "-fno-omit-frame-pointer" "-m64" "--target=x86_64-linux-android" "-static" "-I" "oboe/include" "-I" "oboe/src" "-I" "oboe-ext/include" "-I" "oboe-ext/src" "--target=x86_64-linux-android21" "-std=c++17" "-Wall" "-Wextra-semi" "-Wshadow" "-Wshadow-field" "-fno-rtti" "-fno-exceptions" "-DOBOE_ENABLE_LOGGING=1" "-o" "/home/sergey/Forge/b_music/build/rinf/build/x86_64-linux-android/debug/build/oboe-sys-687f979fe53803b3/out/library/0dbb27d44cb4730c-AAudioLoader.o" "-c" "oboe/src/aaudio/AAudioLoader.cpp" with args clang++ did not execute successfully (status code exit status: 1).cargo:warning=clang++: error: no such file or directory: 'oboe/src/aaudio/AudioStreamAAudio.cpp'
SEVERE: warning: oboe-sys@0.6.1: clang++: error: no input files
...
FAILURE: Build failed with an exception.

* Where:
Script '/home/sergey/.pub-cache/hosted/pub.dev/rinf-7.1.0/cargokit/gradle/plugin.gradle' line: 65

* What went wrong:
Execution failed for task ':rinf:cargokitCargoBuildHubDebug'.
> Process 'command '/home/sergey/.pub-cache/hosted/pub.dev/rinf-7.1.0/cargokit/gradle/../run_build_tool.sh'' finished with non-zero exit value 1
...

It appears only when crate 'oboe' is local.

3). Code snippet with function "JNI_OnLoad" was taken from this message
RustAudio/cpal#720 (comment)

[temeddix]

There's a music player that uses Rinf, and it's called rune. It seems that they are using rodio have solved this problem in their own way.

• fix Android compile process Losses/rune#26

Would you mind trying their solution and sharing the results here?

[sergey-serov]

Greetings!
The answer was in front of me all this time.
On the link from my question: https://cjycode.com/flutter_rust_bridge/guides/how-to/ndk-init - I was just confused that there is code on Kotlin and thought that it's appropriate only for "flutter_rust_bridge".
Finally, it is enough just to add 3 lines:

init {
    System.loadLibrary("hub")
}

in "MainActivity.kt".
Additionally to function "JNI_OnLoad" in "hub/src/lib.rs".

[temeddix]

Congratulations on solving it, and thank you for sharing your experience :)