My device runs on Android 14. Trying to access the network within std::thread results in an app crash.

Native code:

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    std::thread t{[&]{
        gethostbyname("www.google"); // app crash
    }};
    return env->NewStringUTF(hello.c_str());
}

Java code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    binding = ActivityMainBinding.inflate(getLayoutInflater());
    setContentView(binding.getRoot());

    // Example of a call to a native method
    TextView tv = binding.sampleText;
    new Thread(this::stringFromJNI).start();
}

Logcat message:

Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 15894 (e.myapplication), pid 15894 (e.myapplication)

P.S. android.permission.INTERNET is already declared in the manifest. Accessing the network in Java has no problem.

Does anyone know what's going on here?

I tried the follow code, and it works fine:

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    gethostbyname("www.google"); // works fine
    return env->NewStringUTF(hello.c_str());
}

My device runs on Android 14. Trying to access the network within std::thread results in an app crash.

Native code:

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    std::thread t{[&]{
        gethostbyname("www.google"); // app crash
    }};
    return env->NewStringUTF(hello.c_str());
}

Java code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    binding = ActivityMainBinding.inflate(getLayoutInflater());
    setContentView(binding.getRoot());

    // Example of a call to a native method
    TextView tv = binding.sampleText;
    new Thread(this::stringFromJNI).start();
}

Logcat message:

Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 15894 (e.myapplication), pid 15894 (e.myapplication)

P.S. android.permission.INTERNET is already declared in the manifest. Accessing the network in Java has no problem.

Does anyone know what's going on here?

I tried the follow code, and it works fine:

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_myapplication_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    gethostbyname("www.google"); // works fine
    return env->NewStringUTF(hello.c_str());
}

• android
• c++

• You might consider using std::jthread instead of std::thread, as the former will not call std::terminate() it is destroyed, unjoined. – Drew Dormann Commented Mar 14 at 18:02

1 Answer 1

You are not calling join() or detach() on the std::thread object before it is destroyed when your stringFromJNI function exits. So, the std::thread destructor will call std::terminate() to kill the process.

https://en.cppreference/w/cpp/thread/thread/%7Ethread

If *this has an associated thread (joinable() == true), std::terminate() is called.

Notes

A thread object does not have an associated thread (and is safe to destroy) after

• it was default-constructed.
• it was moved from.
• join() has been called.
• detach() has been called.

C++20 adds std::jthread, which does not have this behavior. Its destructor will join() the thread for you:

https://en.cppreference/w/cpp/thread/jthread/%7Ejthread

If *this has an associated thread (joinable() == true), calls request_stop() and then join().

That being said, since your Java code is already calling stringFromJNI in a thread, there is no need for stringFromJNI to create its own thread.