Custom Marshallers never use stateful GetPinnableReference on struct #90621

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1. jtschuster

   added

   area-System.Runtime.InteropServices

   source-generatorIndicates an issue with a source generator featureIndicates an issue with a source generator feature

   on Aug 15, 2023
2. jtschuster

   added this to the 9.0.0 milestone on Aug 15, 2023
4. jkoritzinsky commented on Aug 15, 2023

   

   jkoritzinsky

   on Aug 15, 2023

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   @jtschuster can you share the case where this occurs? I could have sworn that we have tests that validate this behavior in the LibraryImportGenerator.Tests test suite.
5. jtschuster commented on Aug 15, 2023

   

   jtschuster

   on Aug 15, 2023

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   In IStatefulPinnedMarshalling, with a stateless GetPinnableReference on the marshaller, the by value parameter RCW looks like this:

       void global::SharedTypes.ComInterfaces.IStatefulPinnedMarshalling.Method(global::SharedTypes.ComInterfaces.StatefulPinnedType param)
       {
           var(__this, __vtable_native) = ((System.Runtime.InteropServices.Marshalling.IUnmanagedVirtualMethodTableProvider)this).GetVirtualMethodTableInfoForKey(typeof(global::SharedTypes.ComInterfaces.IStatefulPinnedMarshalling));
           int __invokeRetVal;
           // Pin - Pin data in preparation for calling the P/Invoke.
           fixed (void* __param_native = &global::SharedTypes.ComInterfaces.StatefulPinnedTypeMarshaller.GetPinnableReference(param))
           {
               __invokeRetVal = ((delegate* unmanaged[MemberFunction]<void*, nint, int> )__vtable_native[3])(__this, (nint)__param_native);
           }
   
           // NotifyForSuccessfulInvoke - Keep alive any managed objects that need to stay alive across the call.
           System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(__invokeRetVal);
           System.GC.KeepAlive(this);
       }

   With only a stateful GetPinnableReference, it looks like this:

       void global::SharedTypes.ComInterfaces.IStatefulPinnedMarshalling.Method(global::SharedTypes.ComInterfaces.StatefulPinnedType param)
       {
           var(__this, __vtable_native) = ((System.Runtime.InteropServices.Marshalling.IUnmanagedVirtualMethodTableProvider)this).GetVirtualMethodTableInfoForKey(typeof(global::SharedTypes.ComInterfaces.IStatefulPinnedMarshalling));
           nint __param_native = default;
           int __invokeRetVal = default;
           // Setup - Perform required setup.
           global::SharedTypes.ComInterfaces.StatefulPinnedTypeMarshaller __param_native__marshaller = new();
           try
           {
               // Marshal - Convert managed data to native data.
               __param_native__marshaller.FromManaged(param);
               // Pin - Pin data in preparation for calling the P/Invoke.
               fixed (void* __param_native__unused = __param_native__marshaller)
               {
                   // PinnedMarshal - Convert managed data to native data that requires the managed data to be pinned.
                   __param_native = __param_native__marshaller.ToUnmanaged();
                   __invokeRetVal = ((delegate* unmanaged[MemberFunction]<void*, nint, int> )__vtable_native[3])(__this, __param_native);
               }
   
               // NotifyForSuccessfulInvoke - Keep alive any managed objects that need to stay alive across the call.
               System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(__invokeRetVal);
               __param_native__marshaller.OnInvoked();
               System.GC.KeepAlive(this);
           }
           finally
           {
               // CleanupCallerAllocated - Perform cleanup of caller allocated resources.
               __param_native__marshaller.Free();
           }
       }
6. jtschuster commented on Aug 15, 2023

   

   jtschuster

   on Aug 15, 2023

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   Looks like this test is supposed to, but it doesn't actually validate that GetPinnableReference was called.
7. jkoritzinsky commented on Aug 16, 2023

   

   jkoritzinsky

   on Aug 16, 2023

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   No, that is calling GetPinnableReference. The GetPinnableReference call is part of the fixed (void* __param_native__unused = __param_native__marshaller) statement (it's implied by the C# language).
8. jtschuster

   closed this as completedon Aug 17, 2023
9. ghost locked as resolved and limited conversation to collaborators on Sep 16, 2023