> Second, we got a warning under Cygwin x86_64, and we really did not > understand it. The warning is/was: > > Warning: defaulted move assignment operator of X will move assign > virtual base class Y multiple times > > It seems to me the diagnostic is telling me I should provide it. Also > see http://stackoverflow.com/q/34554612. > My bad... That's a Clang warning on OX S under Xcode 7, IIRC. But I use GCC for my heavy lifting, so I was trying to get GCC to tell me where the compiler is generating those functions. Jeff