LGTM but there are a couple of things I strongly encourage considering.
https://codereview.appspot.com/549890043/diff/573710043/lily/global-context.cc File lily/global-context.cc (right): https://codereview.appspot.com/549890043/diff/573710043/lily/global-context.cc#newcode49 lily/global-context.cc:49: event_source ()->add_listener (GET_LISTENER (static_cast<Context *> (this), create_context_from_event), This is a wart. Without the cast, my version of g++ has this to say: ... error: no matching function for call to 'Callback_wrapper::make_smob<trampoline<std::decay<Global_context&>::type, &Context::create_context_from_event> > ... Notice that it correctly selects the method Context::create_context_from_event. It should be possible to extract the proper class type in a second step from that instead of directly from the provided pointer. For that, I think you might need to write a template function that returns the class type given the member function pointer as a function parameter; I don't remember if the C++11 standard library has this, and I don't see it as I skim through cppreference. I'm sure you won't like complicating your macro, but as it stands, someone who writes code that is missing a cast has some reading to do, whereas if you complicate the macro to handle this case, they won't have to read it. https://codereview.appspot.com/549890043/diff/573710043/lily/include/listener.hh File lily/include/listener.hh (right): https://codereview.appspot.com/549890043/diff/573710043/lily/include/listener.hh#newcode143 lily/include/listener.hh:143: // This is somewhat more official, but way overkill Overkill in what respect? I would use standard features where they are appropriate rather than reinventing them. Especially in tricky situations like this, using something with a fixed meaning is beneficial. It looks like dummy_deref also removes const from the class type, which would be more like std::remove_const<std::remove_reference<... If you must have something shorter, consider std::decay<decltype(*(ptr))>::type. It removes the reference and const/volatile. It also tries a couple more conversions than this relies on, but not ones that seem likely to cause stumbling. In any case, as a not-fully-oriented contributor, I prefer not finding stuff in #if 0 when I use grep. If you're set on keeping dummy_deref, it would be enough just to comment that it's an alternative to std::remove_const plus std::remove_reference. But this might all be moot, depending on your reaction to my comment on the static_cast in Global_context. https://codereview.appspot.com/549890043/
