ff-find-the-other-file

ff-find-the-other-file is a compiled Lisp function in `find-file.el'.

(ff-find-the-other-file &optional IN-OTHER-WINDOW)

Find the header or source file corresponding to the current file.
Being on a `#include' line pulls in that file, but see the help on
the `ff-ignore-include' variable.

If optional IN-OTHER-WINDOW is non-nil, find the file in another window.