I've worked through the GDNative C++ example, and everything works, but the Godot editor seems to be keeping the DLL open after I stop running the demo (Windows x64). This means that I can't replace (i.e. recompile) the DLL without closing the editor. This is rather annoying, so I think I must be missing something, but I don't know if there's a setting somewhere or what.
It's the same as this issue but restarting hasn't fixed anything.