An emacs package to track open C preprocessor branches and collect them for display at the top of the buffer window.
Left to right: example C file, scrolled file with preprocessor state not visible, scrolled file with preprocessor-collect showing preprocessor state.
Use (preprocessor-collect-toggle-overlay-ifdefs) to enable/disable the state popup.
Warning: this is a hacky elisp learning experiment. It is not polished, lacks configuration options, and undoubtedly has bugs.