CoreRT quits when Foreground threads are running

[Suchiman]

This code will print Hello World until all eternity on CoreCLR but exit immediately and print nothing on CoreRT.

using System;
using System.Threading;

class Program
{
    static void Main(string[] args)
    {
        var t = new Thread(Meh);
        t.IsBackground = false;
        t.Start();
    }

    private static void Meh(object obj)
    {
        while (true)
        {
            Thread.Sleep(10);
            Console.WriteLine("Hello World!");
        }
    }
}

I suppose it would need to check before this line

corert/src/Native/Bootstrap/main.cpp

Line 450 in 9d8bd29

RhpShutdown();

if there are any Foreground threads still running, how does this work on CoreCLR?

[jkotas]

CoreCLR has this logic in ThreadStore::WaitForOtherThreads https://github.com/dotnet/runtime/blob/6072e4d3a7a2a1493f514cdf4be75a3d56580e84/src/coreclr/src/vm/threads.cpp#L5704 . It is a counter of non-background thread + event that is set whenever this counter goes towards zero.

These two TODOs look related:

• corert/src/System.Private.CoreLib/src/System/Environment.CoreRT.cs

  Line 56 in 9d8bd29

  // TODO: shut down threading etc.

• corert/src/System.Private.CoreLib/src/System/Threading/Thread.CoreRT.cs

  Line 172 in 9d8bd29

  // TODO: Keep a counter of running foregroung threads so we can wait on process exit

[jkotas]

Fixed by dotnet/runtimelab#235