Q:

What should I use to replace SDL_Flip? 

I have a graphics engine in development, and I can't test it because there's no example on how to display an SDL_Surface on a window in SDL2, and there's no older SDL libraries to D.
I can use examples from C++ too, but even with a lot of searching on he internet I only could find tutorials for SDL 1.2. 

A:

SDL_RenderPresent replaced SDL_Flip in SDL 2. 
See the SDL 1.2 to 2.0 Migration Guide for more information.