Out-of-process COM server without a proxy/stub DLL?

Question

I am learning how to implement an out-of-process COM server and came across this Code Project article, Building a LOCAL COM Server and Client: A Step by Step Example.

I can build it, and it runs fine, but where is the proxy/stub DLL? All I can see is the IDL file from which the proxy/stub code is generated during the build. But how is the DLL built, and where is it?

Answer 1

The short answer is that all the interfaces are marked "oleautomation", so oleaut32.dll performs the marshaling, since COM knows how to marshal all the types used in the interfaces.

If "oleautomation" were missing, or a type was specified that COM doesn't know how to marshal by default (see the list here), your nondefault marshaler and its stub would be required.

Answer 2

You need Proxy/Stub project to help COM marshal your interfaces. When you create ATL C++ project with Visual Studio you typically have a secondary project with PS suffix created automatically, and this is your Proxy/Stub DLL. However, you might be doing fine without it at all (I personally never ever had to build and use it, even though I did have to deal with things like custom marshaling). If you provide type library with your project, it is registered and certain conditions are met - COM will supply automatic proxy/stub pair for you.

Bonus reading:

• COM Proxy/Stub DLL and why do you need it
• When Proxy/Stub Pair is Necessary