`ReadAsync()` `ThrowIfStatusNotOk(readTask.Task.Result)` throws `ErrorNotImplemented` on Alpine Linux

[OtavioDePaula]

Hi, I'm using libplctag in a .NET 6 application. I'm calling the ReadAsync() method from your C# wrapper.

When running on Alpine Linux, and I can't handle this using a basic try/catch, it's crashing my entire app, it always throws the following exception:

try
{
    lock (item)
    {
        var tagRead = _tagsRead[item];
        tagRead.ReadAsync();
    }
}
catch (Exception e)
{
}

Unhandled exception. System.AggregateException: One or more errors occurred. (ErrorNotImplemented)
 ---> libplctag.LibPlcTagException: ErrorNotImplemented
   at libplctag.Tag.Qo2yXV0rXkT(Nullable`1  )
   at libplctag.Tag.Abort()
   at libplctag.Tag.<>c__DisplayClass134_0.StwyBqT7PRQ()
   at System.Threading.CancellationToken.<>c.<Register>b__12_0(Object obj)
   at System.Threading.CancellationTokenSource.Invoke(Delegate d, Object state, CancellationTokenSource source)
   at System.Threading.CancellationTokenSource.CallbackNode.<>c.<ExecuteCallback>b__9_0(Object s)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.CancellationTokenSource.CallbackNode.ExecuteCallback()
   at System.Threading.CancellationTokenSource.ExecuteCallbackHandlers(Boolean throwOnFirstException)
   --- End of inner exception stack trace ---
   at System.Threading.CancellationTokenSource.ExecuteCallbackHandlers(Boolean throwOnFirstException)
   at System.Threading.CancellationTokenSource.NotifyCancellation(Boolean throwOnFirstException)
   at System.Threading.CancellationTokenSource.TimerCallback(Object state)
   at System.Threading.TimerQueueTimer.Fire(Boolean isThreadPool)
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()

You can see part of the full dump in the attached log. It seems to happen deep inside the Abort() method and callback registration.

Also, I noticed another issue: when I publish the app using dotnet publish -r linux-musl-x64, the libplctag.so is not correctly built for musl (Alpine). The published file is targeting glibc (x64) instead. Because of this, I need to clone the libplctag repo and build the .so file manually to make it work on Alpine.
This problem here: #341

It used to work directly with publish, but now I always have to build the native lib myself.

DUMP01.txt

[timyhac]

To understand what is throwing the exception, it would be useful to have the libplctag logs.
But it is a surprise that it ever worked - as far as I know the libplctag binaries have always targeted glibc. Can you point to which versions did work?

There are many systems that libplctag could be built for, but this package only bundles the subset that are built as artifacts in the primary repo. Musl would be a good target though, and it looks like kyle has an issue to look at this.

One issue with that code is that you aren't awaiting the async call - so its a fire-and-forget so the exception will surface somewhere else depending on how you've configured global unhandled exception handling.
One issue is you can't use await inside a lock section, so you'll need to use something else like SemaphoreSlim or AsyncEx to achieve exclusion.