Mono hangs when creating a new thread in an external library module about oberon

[rochus-keller]

I found the following:

  public class Test5 {
      private static void worker(object o) {
              System.Console.WriteLine("hello from worker");
      }
      
      static void begin() {
              System.Console.WriteLine("start test");
	          System.Threading.Thread t = new System.Threading.Thread(worker);
	          t.Start();
	          t.Join(); // hangs in join
              System.Console.WriteLine("end test");
      }
    	      
      static Test5()  {
	  // no effect: System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(typeof (object).TypeHandle);
	  // no effect: begin();
             System.Console.WriteLine("start test");
	         System.Threading.Thread t = new System.Threading.Thread(worker);
	         t.Start();
	         t.Join(); // hangs in join
             System.Console.WriteLine("end test");
      }
  
  static void Main(string[] args)  {
	      /*
          System.Console.WriteLine("hello from Main");
          System.Console.WriteLine("start test");
	      System.Threading.Thread t = new System.Threading.Thread(worker);
	      t.Start();
	      t.Join(); // works
          System.Console.WriteLine("end test");
          */
      }
  }

This is a minimal C# application which is able to demonstrate the effect. Thread.Join() uses assumingly the same low-level function as bthread_wait(). If we call Join() in the static constructor the thread starts but doesn't run its body; so we aparently cannot use static constructors as the "begin" part of a module - the system doesn't seem to be working properly at this point.

[rochus-keller]

Fixed with commit 18e7d0d; the issue was indeed related to the static constructor; apparently it is a bad idea to map Oberon module begin sections to static constructors; in the present case the thread system seems to be in an unknown state causing the strange observations. Since I moved module begin to a dedicated method called via import dependency chain NAppGUI threads work seamless with Mono.

The NAppGUI Fractals example now works fine on Linux and Windows when run from Mono. There is still an issue on macOS though; the NAppGUI app seems to hang in osmain just after window_show; will be traced in a separate issue.