online compiler

https://cppinsights.io/

https://godbolt.org/

Modern C++ Feature

Dependent name lookup for C++ templates

https://ljwo.wordpress.com/2018/06/02/on-a-forwarding-bug/

http://madebyevan.com/obscure-cpp-features/

https://www.fluentcpp.com/2018/06/22/variadic-crtp-opt-in-for-class-features-at-compile-time/ Part 1

https://www.fluentcpp.com/2018/06/26/variadic-crtp-packs-from-opt-in-skills-to-opt-in-skillsets/ Part 2

http://c-faq.com/decl/spiral.anderson.html