From 46b3aa19875c0507efe489534035117d5fc1c6be Mon Sep 17 00:00:00 2001
From: Jeremy Koritzinsky <jekoritz@microsoft.com>
Date: Wed, 3 May 2023 11:46:26 -0700
Subject: [PATCH 1/2] Keep `this` alive across the native call for VTable-based
 source-generation

---
 .../ManagedToNativeVTableMethodGenerator.cs            | 10 ++++++++++
 .../Microsoft.Interop.SourceGeneration/TypeNames.cs    |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs b/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs
index 482cc2bc5c9bd5..04474ea49c78ae 100644
--- a/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs
+++ b/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs
@@ -185,6 +185,16 @@ public BlockSyntax GenerateStubBody(int index, ImmutableArray<FunctionPointerUnm
             }
 
             tryStatements.AddRange(statements.NotifyForSuccessfulInvoke);
+
+            // GC.KeepAlive(this);
+            tryStatements.Add(
+                ExpressionStatement(
+                    InvocationExpression(
+                        MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression,
+                            ParseTypeName(TypeNames.System_GC),
+                            IdentifierName("KeepAlive")),
+                        ArgumentList(SingletonSeparatedList(Argument(ThisExpression()))))));
+
             tryStatements.AddRange(statements.Unmarshal);
 
             List<StatementSyntax> allStatements = setupStatements;
diff --git a/src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/TypeNames.cs b/src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/TypeNames.cs
index 43a458a0dfa8e1..314b8197699e2b 100644
--- a/src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/TypeNames.cs
+++ b/src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/TypeNames.cs
@@ -51,6 +51,8 @@ public static class TypeNames
 
         public const string System_Exception = "System.Exception";
 
+        public const string System_GC = "System.GC";
+
         public const string System_Type = "System.Type";
 
         public const string System_Int16 = "System.Int16";

From 1149f9baeb7658a3b4b99edcc8e16a475f079d2d Mon Sep 17 00:00:00 2001
From: Jeremy Koritzinsky <jkoritzinsky@gmail.com>
Date: Wed, 3 May 2023 15:28:04 -0700
Subject: [PATCH 2/2] Update ManagedToNativeVTableMethodGenerator.cs

---
 .../ManagedToNativeVTableMethodGenerator.cs                    | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs b/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs
index 04474ea49c78ae..3792231bfadd77 100644
--- a/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs
+++ b/src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ManagedToNativeVTableMethodGenerator.cs
@@ -186,6 +186,9 @@ public BlockSyntax GenerateStubBody(int index, ImmutableArray<FunctionPointerUnm
 
             tryStatements.AddRange(statements.NotifyForSuccessfulInvoke);
 
+            // Keep the this object alive across the native call, similar to how we handle marshalling managed delegates.
+            // We do this right after the NotifyForSuccessfulInvoke phase as that phase is where the delegate objects are kept alive.
+            // If we ever move the "this" object handling out of this type, we'll move the handling to be emitted in that phase.
             // GC.KeepAlive(this);
             tryStatements.Add(
                 ExpressionStatement(