CPP-Conf

CPP-Conf-20. Back to Basics: Class Layout - Stephen Dewhurst

Empty class optimization (EBCO)

https://en.cppreference.com/w/cpp/language/ebo
https://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Empty_Base_Optimization

The spaceship operator <=>

https://devblogs.microsoft.com/cppblog/simplify-your-code-with-rocket-science-c20s-spaceship-operator/
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1185r2.html