Hello, Will using GetComInterfaceForObject and passing the returned IntPtr to unmanaged code keep the managed object from being moved in memory? Or does the clr somehow maintain that ptr? Note that the unmanaged code will use this for the lifetime of the program, and I need to make sure the managed object is not being moved by the GC.(At least I think that's right?)
- EDIT - Alright I found some info and I am thinking that this may be the answer. It deals with delegates, but I would have to believe calling GetComInterfaceForObject does something along the same lines.
"Managed Delegates can be marshaled to unmanaged code, where they are exposed as unmanaged function pointers. Calls on those pointers will perform an unmanaged to managed transition; a change in calling convention; entry into the correct AppDomain; and any necessary argument marshaling. Clearly the unmanaged function pointer must refer to a fixed address. It would be a disaster if the GC were relocating that! This leads many applications to create a pinning handle for the delegate. This is completely unnecessary. The unmanaged function pointer actually refers to a native code stub that we dynamically generate to perform the transition & marshaling. This stub exists in fixed memory outside of the GC heap.
However, the application is responsible for somehow extending the lifetime of the delegate until no more calls will occur from unmanaged code. The lifetime of the native code stub is directly related to the lifetime of the delegate. Once the delegate is collected, subsequent calls via the unmanaged function pointer will crash or otherwise corrupt the process. In our recent release, we added a Customer Debug Probe which allows you to cleanly detect this all too common bug in your code. If you havent started using Customer Debug Probes during development, please take a look!"