android example crashes on launch: "dlopen failed: cannot locate symbol __cxa_pure_virtual"

[nikita-skobov]

My device:

google pixel 4a (sunfish)
aarch64
ro.build.version.release = 11
ro.build.version.sdk = 30

Steps to reproduce:

First I tried:

git clone https://github.com/RustAudio/cpal
cd cpal
cargo apk build --example android

Then I install the android.apk to my phone, and run it, and it crashes immediately. Looking at the logcat:

Click to expand

03-21 19:08:11.676  6588  6588 W NativeActivity: NativeActivity LoadNativeLibrary("/data/app/~~OUwQhY55D-pFmz47CJ2IbQ==/rust.example.android-wZ5h-IHTeEtI1UPvU4vctg==/lib/arm64/libandroid.so") failed: dlopen failed: cannot locate symbol "__cxa_pure_virtual" referenced by "/data/app/~~OUwQhY55D-pFmz47CJ2IbQ==/rust.example.android-wZ5h-IHTeEtI1UPvU4vctg==/lib/arm64/libandroid.so"...
03-21 19:08:11.676  6588  6588 D AndroidRuntime: Shutting down VM
03-21 19:08:11.670  6588  6588 W example.android: type=1400 audit(0.0:390678): avc: granted { execute } for path="/data/app/~~OUwQhY55D-pFmz47CJ2IbQ==/rust.example.android-wZ5h-IHTeEtI1UPvU4vctg==/lib/arm64/libandroid.so" dev="dm-16" ino=54014 scontext=u:r:untrusted_app_29:s0:c4,c257,c512,c768 tcontext=u:object_r:apk_data_file:s0 tclass=file app=rust.example.android
03-21 19:08:11.677  6588  6588 E AndroidRuntime: FATAL EXCEPTION: main
03-21 19:08:11.677  6588  6588 E AndroidRuntime: Process: rust.example.android, PID: 6588
03-21 19:08:11.677  6588  6588 E AndroidRuntime: java.lang.UnsatisfiedLinkError: Unable to load native library "/data/app/~~OUwQhY55D-pFmz47CJ2IbQ==/rust.example.android-wZ5h-IHTeEtI1UPvU4vctg==/lib/arm64/libandroid.so": dlopen failed: cannot locate symbol "__cxa_pure_virtual" referenced by "/data/app/~~OUwQhY55D-pFmz47CJ2IbQ==/rust.example.android-wZ5h-IHTeEtI1UPvU4vctg==/lib/arm64/libandroid.so"...
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.NativeActivity.onCreate(NativeActivity.java:178)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:8000)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:7984)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:106)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:223)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:7660)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
03-21 19:08:11.677  6588  6588 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)

I looked up the issue with __cxz_pure_virtual and some people said you could just stub it out with:

#[no_mangle]
pub unsafe extern "C" fn __cxa_pure_virtual() {
    loop {
         
    }
}

So I tried putting that in examples/android.rs and rebuilding, and then I get:

With the __cxa_pure_virtual stub

Click to expand

03-21 19:06:01.480  6534  6534 W NativeActivity: NativeActivity LoadNativeLibrary("/data/app/~~89rj6sFEJqYLOUzNJvP7SA==/rust.example.android-1Xjx_7TTAqivFzu181VStw==/lib/arm64/libandroid.so") failed: dlopen failed: cannot locate symbol "_ZNKSt13runtime_error4whatEv" referenced by "/data/app/~~89rj6sFEJqYLOUzNJvP7SA==/rust.example.android-1Xjx_7TTAqivFzu181VStw==/lib/arm64/libandroid.so"...
03-21 19:06:01.480  6534  6534 D AndroidRuntime: Shutting down VM
03-21 19:06:01.481  6534  6534 E AndroidRuntime: FATAL EXCEPTION: main
03-21 19:06:01.481  6534  6534 E AndroidRuntime: Process: rust.example.android, PID: 6534
03-21 19:06:01.481  6534  6534 E AndroidRuntime: java.lang.UnsatisfiedLinkError: Unable to load native library "/data/app/~~89rj6sFEJqYLOUzNJvP7SA==/rust.example.android-1Xjx_7TTAqivFzu181VStw==/lib/arm64/libandroid.so": dlopen failed: cannot locate symbol "_ZNKSt13runtime_error4whatEv" referenced by "/data/app/~~89rj6sFEJqYLOUzNJvP7SA==/rust.example.android-1Xjx_7TTAqivFzu181VStw==/lib/arm64/libandroid.so"...
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.NativeActivity.onCreate(NativeActivity.java:178)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:8000)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:7984)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:106)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:223)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:7660)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
03-21 19:06:01.481  6534  6534 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)

So a similar error, but this time it cant find some other function.

I also found @katyo oboe-rs project, and I see they have oboe-demo.apk in their releases, so I thought I should try running an apk that someone else built (maybe my error was coming from me building it wrong somehow), so I ran that oboe-demo.apk and this time I see:

From the oboe-demo example

Click to expand

03-21 19:10:01.545  6752  6752 W NativeActivity: NativeActivity LoadNativeLibrary("/data/app/~~LpiXmkBDwZU5Vl8-g-5AqQ==/rust.oboe_demo-VFTxoG3fefCxFcnGPQCc0Q==/lib/arm64/liboboe_demo.so") failed: dlopen failed: cannot locate symbol "__cxa_pure_virtual" referenced by "/data/app/~~LpiXmkBDwZU5Vl8-g-5AqQ==/rust.oboe_demo-VFTxoG3fefCxFcnGPQCc0Q==/lib/arm64/liboboe_demo.so"...
03-21 19:10:01.546  6752  6752 D AndroidRuntime: Shutting down VM
03-21 19:10:01.546  6752  6752 E AndroidRuntime: FATAL EXCEPTION: main
03-21 19:10:01.546  6752  6752 E AndroidRuntime: Process: rust.oboe_demo, PID: 6752
03-21 19:10:01.546  6752  6752 E AndroidRuntime: java.lang.UnsatisfiedLinkError: Unable to load native library "/data/app/~~LpiXmkBDwZU5Vl8-g-5AqQ==/rust.oboe_demo-VFTxoG3fefCxFcnGPQCc0Q==/lib/arm64/liboboe_demo.so": dlopen failed: cannot locate symbol "__cxa_pure_virtual" referenced by "/data/app/~~LpiXmkBDwZU5Vl8-g-5AqQ==/rust.oboe_demo-VFTxoG3fefCxFcnGPQCc0Q==/lib/arm64/liboboe_demo.so"...
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.NativeActivity.onCreate(NativeActivity.java:178)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:8000)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:7984)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:106)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:223)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:7660)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at com.android.internal.os.ExecInit.main(ExecInit.java:48)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit.nativeFinishInit(Native Method)
03-21 19:10:01.546  6752  6752 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit.main(RuntimeInit.java:399)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: Error reporting crash
03-21 19:10:01.547  6752  6752 E AndroidRuntime: java.lang.RuntimeException: Bad file descriptor
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at android.os.BinderProxy.transactNative(Native Method)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at android.os.BinderProxy.transact(BinderProxy.java:550)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at android.app.IActivityManager$Stub$Proxy.handleApplicationCrash(IActivityManager.java:5208)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$KillApplicationHandler.uncaughtException(RuntimeInit.java:158)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:1073)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:1068)
03-21 19:10:01.547  6752  6752 E AndroidRuntime: 	at java.lang.Thread.dispatchUncaughtException(Thread.java:2203)

So in the oboe-demo, it actually didnt 'crash' right away. it kept running, but it wasnt doing anything. it was just producing this error over and over, and once again the issue is dlopen failed: cannot locate symbol "__cxa_pure_virtual"

Conclusion

Is this an issue with android 11 not having stdc++ or something like that? i think i saw someone comment something like that before.

I debugged this for a few hours today and tried a bunch of different forks and hacks and I couldn't figure it out, so hoping someone with more knowledge about android audio could help me out.

[irh]

@nikita-skobov I've also run into this issue, also on a Pixel 4a.

I also tried a bunch of different things over a couple of days (including manually linking the missing C++ runtime symbols from libc++abi.a), with no success.

In the end I've chosen to use AAudio directly instead of using cpal+Oboe when building for Android.

[nikita-skobov]

@irh

Could you refer me to a minimal example? I tried AAudio as well but I've must have done it wrong because I couldn't get it to work.

[irh]

I can't point you to an example as I'm working on a private project, but I can say that I found it quite straight-forward using @endragor's AAudio bindings.

• Use an AAudioStreamBuilder to configure a stream, finalising the build with .open_stream().
• Once the stream's created, use .request_start() to get the stream running.
• The only slightly tricky thing was figuring out how to make use of the audio buffer in the callback.
  • My approach has been to specify the format to Format::F32 with a fixed channel count. You can then build a [f32] slice with:

let buffer = unsafe {
  std::slice::from_raw_parts_mut(
    buffer.as_ptr() as *mut f32,
    frames as usize * CHANNEL_COUNT,
  )
};

• If you don't specify the format+channel count then you'll need to inspect the callback's AAudioStreamInfo.

This is my first time looking at AAudio so I might have misunderstood something here, but it seems to be working pretty well so far.

[chriscoomber]

Hi, I saw this same error when using jni-rs (so nothing to do with cpal, sorry, I found this issue through google).

In my lib.rs I had some JNI method implementations (e.g. #[no_mangle] pub extern "system" fn Java_path_to_package_MyClass_helloWorld(...)) and some C implementations (e.g. #[no_mangle] pub extern "C" fn hello_world()). I then compiled this to a cdylib (targeting Android) and tried to load the library in my Android app, and I saw the same error about __cxz_pure_virtual (and when I implemented that with a loop, I got the next error that OP found also).

I found that when I deleted my C functions from lib.rs (I didn't need them anyway, just a relic from some testing I was doing) this error went away.

FWIW my rust library depends on oboe-rs, so I'm in the same ballpark as you two. I'm not using CPAL because I only found out about it today.

Edit: scratch that, it's started showing this error again and I've just added more JNI functions...

Edit edit: it looks like the C functions were a red herring. When I switched between building with debug to building with release mode, it seemed to resolve the issue. I must have tried two things at once - not very scientific of me. Edit edit edit: I'm not even sure it's release mode as it seems to come and go completely randomly. It might be going wrong when I build with this plugin but not when I build via command line, but I'm not 100% sure. Last edit: seems just random whether it decides to fail. I can make any change to the code and next time it might work or might fail.

[trobanga]

This can be solved by enabling the shared-stdcxx feature for oboe

oboe = { version = "0.4", features = [ "java-interface", "shared-stdcxx" ] }

Then I also had to copy libc++_shared.so into my jniLibs directory (there's likely a way to automate this...)

[Icemic]

Still a problem in 2025, but it works for me just add println!("cargo:rustc-link-lib=static=c++"); to build.rs

[heydocode]

You all just have to enable the feature shared-stdcxx from oboe for android builds.
Or, write this in build.rs: println!("cargo:rustc-link-lib=dylib=c++_shared"); (static C++ STL can be optimized away and some symbols will be missing).

When you build an app using Oboe without the “shared-stdcxx” feature, it links against the static C++ STL (Standard Template Library) by default. In that configuration, some runtime symbols—like __cxa_pure_virtual—may not be included (or may be optimized away) by the linker. This missing symbol causes the dynamic linker to fail at runtime (dynamic linker open fails).

By enabling the feature "oboe/shared-stdcxx", you switch Oboe’s linkage to use the shared C++ runtime (typically, libc++_shared.so). This shared library provides a full set of C++ runtime symbols (including __cxa_pure_virtual), which ensures that all necessary symbols are available at runtime and prevents the dlopen error.

In short, the feature forces Oboe to link against a shared STL that includes the missing symbols, thereby fixing the error.

For example, in one GitHub discussion related to oboe-sys (even if initially the concern was about rodio), a maintainer mentioned that Oboe links against the static C++ STL by default unless the shared-stdcxx feature is enabled, and that switching to the shared runtime resolved the undefined symbol errors.

[jonatino]

Still a problem in 2025, but it works for me just add println!("cargo:rustc-link-lib=static=c++"); to build.rs

Works!

[roderickvd]

Still a problem in 2025, but it works for me just add println!("cargo:rustc-link-lib=static=c++"); to build.rs

Also now that we switched from oboe to ndk?

[heydocode]

I think that it should be fixed now, as CPAL seems to be a pure-Rust dependency and so does not require any C++ runtime.