Banana Rogue has already 6 files that compile which can be seen as a minor success. It tells that once you get old C translated to C++ compiler it will be "fine" if we forget about memory management problems of C like raw arrays etc.
Function pointer stuff in daemon and daemons modules doesn't work, because the function signature has to match the pointer in C++ which is more strict about types. If I'm lucky it will be fixed by changing all 'void' functions to 'int' return value, even if they don't use it. Or check out if the functions actually are all void type.
The gui refactoring is almost ready. Most of the action happens in Window (previously WINDOW) struct of curses which I replaced with a class. Window is used inside io module through procedural function wrappers which makes it "easy-ish" to replace later with other type of implementation. Everything works in ascii level, the Window is simply a rectangle of ascii data. It's quite brilliant. The only connection to SDL2 will be Display which shows the window. Then also you need SDL2 in keyboard routines which are also simple in case of ascii codes. There will be some complications if you want to use modifier keys or any special keys like arrow keys, but it can't be too difficult to fix.
The rest of bigger problems are in save game routine, options module (which can be easy, I have skipped it) and linked list routines. The internal type for linked list data is surprisingly char* which is a mystery, because malloc itself is void type or typeless.