LockServer

[adrianwithah]

Currently, IClassFactory::LockServer is currently unimplemented for all our generated class factories. This should be implemented even for in-process servers.

It's primary purpose is to ensure that the server DLL is not unloaded prematurely, while clients still hold references to objects from the DLL. This usually occurs when clients call CoFreeUnusedLibraries

As it stands now, this premature unloading will never happen, as we do not expose DllCanUnloadNow for our in-process DLLs, meaning our DLL can only be unloaded when the client calls CoUninitialize. (this behaviour is stated here)

However, implementing this is crucial as it will allow developers to be efficient with memory usage.

[Rantanen]

DllCanUnloadNow should allow unloading only when there are no external references to the library. Given com-rs implements class objects as normal heap based COM objects, their references should count as references for DllCanUnloadNow as well.

Furthermore the documentation of LockServer states:

It is important to count all calls, not just the last one, to LockServer, because calls must be balanced before attempting to release the pointer to the IClassFactory interface on the class object or an error results.

Which implies that LockServer should only be active while a reference on IClassFactory is held and that reference on IClassFactory should be enough to keep the DllCanUnloadNow from allowing unloading.

Or is there something I'm missing here concerning in-process servers?

Of course this doesn't really mean LockServer should be ignored, especially since there's a long term goal to support out-of-process COM servers.