Add ldvirtftn

src/Platforms/Echo.Platforms.AsmResolver/Emulation/Dispatch/ObjectModel/LdvirtftnHandler.cs

@@ -0,0 +1,56 @@
+using System.Linq;
+using AsmResolver.DotNet;
+using AsmResolver.DotNet.Signatures;
+using AsmResolver.PE.DotNet.Cil;
+
+namespace Echo.Platforms.AsmResolver.Emulation.Dispatch.ObjectModel;
+
+/// <summary>
+/// Implements a CIL instruction handler for <c>ldvirtftn</c> instruction.
+/// </summary>
+[DispatcherTableEntry(CilCode.Ldvirtftn)]
+public class LdvirtftnHandler : FallThroughOpCodeHandler
+{
+    /// <inheritdoc/>
+    protected override CilDispatchResult DispatchInternal(CilExecutionContext context, CilInstruction instruction)
+    {
+        var stack = context.CurrentFrame.EvaluationStack;
+        var factory = context.Machine.ValueFactory;
+        var methods = context.Machine.ValueFactory.ClrMockMemory.MethodEntryPoints;
+        var type = context.Machine.ContextModule.CorLibTypeFactory.IntPtr;
+
+        var thisObject = stack.Pop().Contents;
+        if (!thisObject.IsFullyKnown)
+            throw new CilEmulatorException("Unable to resolve an unknown object.");
+
+        var thisObjectType = thisObject.AsObjectHandle(context.Machine).GetObjectType().Resolve();
+        if (thisObjectType == null)
+            throw new CilEmulatorException("Unable to resolve the type of object");
+
+        var virtualFunction = ((IMethodDescriptor)instruction.Operand!);
+        var virtualFunctionName = virtualFunction.Name;
+        var virtualFunctionSignature = virtualFunction.Signature;
+
+        do
+        {   
+            // try resolve function
+            var resolvedVirtualFunction = thisObjectType.Methods
+                .FirstOrDefault(method => method.Name == virtualFunctionName 
+                && SignatureComparer.Default.Equals(method.Signature, virtualFunctionSignature));
+
+            // if resolved then push function pointer
+            if (resolvedVirtualFunction != null)
+            {
+                var functionPointer = methods.GetAddress(resolvedVirtualFunction);
+                stack.Push(factory.CreateNativeInteger(functionPointer), type);
+                return CilDispatchResult.Success();
+            }
+
+            // else switch to BaseType and try resolve again
+            thisObjectType = thisObjectType.BaseType?.Resolve();
+        }   // or exit and throw CilEmulationException
+        while (thisObjectType != null);
+
+        throw new CilEmulatorException($"Unable to resolve a virtual function for type {thisObjectType!.FullName}");
+    }
+}

test/Platforms/Echo.Platforms.AsmResolver.Tests/Emulation/CilVirtualMachineTest.cs

@@ -3,6 +3,7 @@
 using System.Reflection;
 using System.Text;
 using System.Threading;
+using AsmResolver;
 using AsmResolver.DotNet;
 using AsmResolver.DotNet.Code.Cil;
 using AsmResolver.DotNet.Signatures;
@@ -710,5 +711,41 @@ public void CallDelegate()
             Assert.Single(_mainThread.CallStack.Peek().EvaluationStack);
             Assert.Equal(5, _mainThread.CallStack.Peek().EvaluationStack.Peek().Contents.AsSpan().I32);
         }
+
+        [Fact]
+        public void CallDelegateWithVirtualFunction()
+        {
+            var method = _fixture.MockModule
+                    .LookupMember<TypeDefinition>(typeof(TestClass).MetadataToken)
+                    .Methods.First(m => m.Name == nameof(TestClass.TestVirtualDelegateCall));
+
+            _vm.Invoker = DefaultInvokers.CreateDefaultShims().WithFallback(DefaultInvokers.StepIn).WithFallback(DefaultInvokers.ReflectionInvoke);
+            _mainThread.CallStack.Push(method);
+
+            var instructions = method.CilMethodBody!.Instructions;
+
+            var invokeDelegateOffset = instructions
+                .First(instruction => instruction.Operand is IMethodDescriptor descriptor 
+                    && descriptor.Name == "Invoke")
+                .Offset;
+
+            var expectedResults = new string[] { "Mr.String", "Mocks.TestClass" };
+
+            for (int i = 0; i < expectedResults.Length; i++)
+            {
+                _mainThread.StepWhile(CancellationToken.None, context => context.CurrentFrame.ProgramCounter != invokeDelegateOffset);
+                _mainThread.Step(); // invoke: string Func<object>::Invoke()
+                // Expected stack:
+                // (0) root -> (1) TestVirtualDelegateCall -> (2) Func<object>::Invoke -> (3) *::ToString
+                Assert.Equal(4, _mainThread.CallStack.Count);
+
+                // exit from *::ToString
+                while (_mainThread.CallStack.Count != 2)
+                    _mainThread.StepOut();
+
+                var returnedString = _mainThread.CallStack.Peek().EvaluationStack.Peek();
+                Assert.Equal(expectedResults[i], _vm.ObjectMarshaller.ToObject<string>(returnedString.Contents.AsSpan()));
+            }
+        }
     }
 }

test/Platforms/Mocks/TestClass.cs

@@ -295,5 +295,21 @@ public static int TestDelegateCall()
             ReturnAnyIntDelegate del = ReturnAnyInt;
             return del();
         }
+
+        public static void TestVirtualDelegateCall()
+        {
+            var objects = new object[] { "Mr.String", new TestClass() };
+            for(int i = 0; i < objects.Length; i++)
+            {
+                var @object = objects[i];
+                var function = new Func<string>(@object.ToString);
+                _ = function();
+            }
+        }
+
+        public override string ToString()
+        {
+            return "Mocks.TestClass";
+        }
     }
 }