MonoVM: Type.GetInterfaceMap may return null TargetMethods entries

[rolfbjarne]

Description

Type.GetInterfaceMap returns null entries for TargetMethods sometimes.

Test case:
consoleapp-3c50b29.zip

Repro:

• Install .NET 6.0.100-preview.6.21308.62
• Download & extract test case
• Run the run-with-mono.sh script

$ ./run-with-mono.sh 
+ DOTNET=dotnet
+ dotnet publish -r osx-x64 /p:UseMonoRuntime=true
Microsoft (R) Build Engine version 17.0.0-preview-21304-01+a5ea6d2ca for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored /Users/rolf/test/dotnet/consoleapp/myproject.csproj (in 93 ms).
  You are using a preview version of .NET. See: https://aka.ms/dotnet-core-preview
  myproject -> /Users/rolf/test/dotnet/consoleapp/bin/Debug/net6.0/osx-x64/myproject.dll
  myproject -> /Users/rolf/test/dotnet/consoleapp/bin/Debug/net6.0/osx-x64/publish/
+ MONO_ENV_OPTIONS=--version
+ ./bin/Debug/net6.0/osx-x64/publish/myproject
Mono JIT compiler version 6.0.0.0 (6.0.21.30601 @Commit: 5b8e1780ad7740e632c285bc2af13a8d0b20c5a9)
Copyright (C) Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           
	SIGSEGV:       normal
	Notification:  kqueue
	Architecture:  amd64
	Disabled:      
	Misc:          softdebug 
	Interpreter:   yes
	LLVM:          supported, not enabled.
	Suspend:       hybrid
	GC:            sgen (concurrent by default)
+ ./bin/Debug/net6.0/osx-x64/publish/myproject Xamarin.Mac.dll
Running on .NET 6.0.0-preview.6.21306.1
Loading: /Users/rolf/test/dotnet/consoleapp/Xamarin.Mac.dll
Got interface map for type CoreBluetooth.CBCentralManagerDelegate and interface CoreBluetooth.ICBCentralManagerDelegate with 1 entries:
    1 Void UpdatedState(CoreBluetooth.CBCentralManager) -> null

Compare to when running with .NET:

$ dotnet run *.dll
Running on .NET 6.0.0-preview.6.21306.1
Loading: /Users/rolf/test/dotnet/consoleapp/Xamarin.Mac.dll
Got interface map for type CoreBluetooth.CBCentralManagerDelegate and interface CoreBluetooth.ICBCentralManagerDelegate with 1 entries:
    1 Void UpdatedState(CoreBluetooth.CBCentralManager) -> Void UpdatedState(CoreBluetooth.CBCentralManager)

Configuration

.NET 6.0.100-preview.6.21308.62

Regression?

Yes (since 6.0.100-preview.6.21280.2).

Other information

Our tests ran into this when bumping to the latest .NET version (dotnet/macios#11852).

Looking at the dotnet/runtime commits since it worked, there's a possible cause here: 5d64814 (CC @bholmes).

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

Tagging subscribers to this area: @CoffeeFlux
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Type.GetInterfaceMap returns null entries for TargetMethods sometimes.

Test case:
consoleapp-3c50b29.zip

Repro:

• Install .NET 6.0.100-preview.6.21308.62
• Download & extract test case
• Run the run-with-mono.sh script

$ ./run-with-mono.sh 
+ DOTNET=dotnet
+ dotnet publish -r osx-x64 /p:UseMonoRuntime=true
Microsoft (R) Build Engine version 17.0.0-preview-21304-01+a5ea6d2ca for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored /Users/rolf/test/dotnet/consoleapp/myproject.csproj (in 93 ms).
  You are using a preview version of .NET. See: https://aka.ms/dotnet-core-preview
  myproject -> /Users/rolf/test/dotnet/consoleapp/bin/Debug/net6.0/osx-x64/myproject.dll
  myproject -> /Users/rolf/test/dotnet/consoleapp/bin/Debug/net6.0/osx-x64/publish/
+ MONO_ENV_OPTIONS=--version
+ ./bin/Debug/net6.0/osx-x64/publish/myproject
Mono JIT compiler version 6.0.0.0 (6.0.21.30601 @Commit: 5b8e1780ad7740e632c285bc2af13a8d0b20c5a9)
Copyright (C) Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           
	SIGSEGV:       normal
	Notification:  kqueue
	Architecture:  amd64
	Disabled:      
	Misc:          softdebug 
	Interpreter:   yes
	LLVM:          supported, not enabled.
	Suspend:       hybrid
	GC:            sgen (concurrent by default)
+ ./bin/Debug/net6.0/osx-x64/publish/myproject Xamarin.Mac.dll
Running on .NET 6.0.0-preview.6.21306.1
Loading: /Users/rolf/test/dotnet/consoleapp/Xamarin.Mac.dll
Got interface map for type CoreBluetooth.CBCentralManagerDelegate and interface CoreBluetooth.ICBCentralManagerDelegate with 1 entries:
    1 Void UpdatedState(CoreBluetooth.CBCentralManager) -> null

Compare to when running with .NET:

$ dotnet run *.dll
Running on .NET 6.0.0-preview.6.21306.1
Loading: /Users/rolf/test/dotnet/consoleapp/Xamarin.Mac.dll
Got interface map for type CoreBluetooth.CBCentralManagerDelegate and interface CoreBluetooth.ICBCentralManagerDelegate with 1 entries:
    1 Void UpdatedState(CoreBluetooth.CBCentralManager) -> Void UpdatedState(CoreBluetooth.CBCentralManager)

Configuration

.NET 6.0.100-preview.6.21308.62

Regression?

Yes (since 6.0.100-preview.6.21280.2).

Other information

Our tests ran into this when bumping to the latest .NET version (dotnet/macios#11852).

Looking at the dotnet/runtime commits since it worked, there's a possible cause here: 5d64814 (CC @bholmes).

Author:	rolfbjarne
Assignees:	-
Labels:	area-VM-meta-mono, untriaged
Milestone:	-

[akoeplinger]

/cc @lambdageek looks like a regression most likely from #52566

[CoffeeFlux]

cc: @bholmes

[marek-safar]

/cc @SamMonoRT

[lambdageek]

Here's the repro (.NET 6 Preview 4, using CoreCLR):

using System;

interface I {
    public void M ();
}

abstract class C : I {
    public abstract void M ();
}

interface ID {
    public void M () { /* I have a DIM */ Console.WriteLine ("ID"); }
}

abstract class CD : ID  {
    public abstract void M ();
}

class H : CD {
    public override void M () { Console.WriteLine ("H"); }
}

interface I3 : ID {
    abstract void ID.M (); // reabstracted
}

abstract class J : I3 {
    public abstract void M ();
}

namespace hark
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

	    var inputs = new (Type,Type)[] { (typeof(C), typeof(I)), (typeof(CD), typeof(ID)),
		    (typeof (J), typeof (ID)), (typeof (J), typeof (I3))};

	    foreach (var (type,iface) in inputs) {
		dumpIfaces (type, iface);
	    }
	    

	    (new H() as ID).M();
        }

	public static void dumpIfaces (Type type, Type iface) {
	    var map = type.GetInterfaceMap (iface);

	    Console.WriteLine ($"Got interface map for type {type} and interface {iface} with {map.InterfaceMethods.Length} entries:");
	    for (int i = 0; i < map.InterfaceMethods.Length; i++) {
		Console.WriteLine ($"    {i + 1} {map.InterfaceMethods [i]} -> {(map.TargetMethods [i] == null ? "null" : map.TargetMethods [i])}");
		}
	}
    }
}

Should Print

Hello World!
Got interface map for type C and interface I with 1 entries:
    1 Void M() -> Void M()
Got interface map for type CD and interface ID with 1 entries:
    1 Void M() -> Void M()
Got interface map for type J and interface ID with 1 entries:
    1 Void M() -> Void M()
Got interface map for type J and interface I3 with 1 entries:
    1 Void ID.M() -> null
H

Mono prints

Hello World!
Got interface map for type C and interface I with 1 entries:
    1 Void M() -> null
Got interface map for type CD and interface ID with 1 entries:
    1 Void M() -> null
Got interface map for type J and interface ID with 1 entries:
    1 Void M() -> null
Got interface map for type J and interface I3 with 1 entries:
    1 Void ID.M() -> null
H

[bholmes]

I suspect that I did not cover the case when the found target method is abstract, but is on an a class.

I think a check needs to be added here to ensure that the found method is an interface.

However I am still trying to understand why the 4th case provided above returns null.

[bholmes]

@bholmes I'm unclear in what scenario with reabstraction you want to return NULL in #52566 ?

Lines 106 and 111.

runtime/src/tests/reflection/DefaultInterfaceMethods/GetInterfaceMapConsumer.cs

Lines 103 to 112 in ac87f00

	if (declMethod.Equals(ifooDefaultMethod))
	{
	foundMatchMask |= 1;
	CheckEqual(ref failed, implMethod, null);
	}
	else if (declMethod.Equals(ifooOtherMethod))
	{
	foundMatchMask |= 2;
	CheckEqual(ref failed, implMethod, null);
	}