c-down-conditional is an interactive compiled Lisp function in `cc-cmds.el'.

(c-down-conditional COUNT)

Move forward into the next preprocessor conditional, leaving mark behind.
A prefix argument acts as a repeat count. With a negative argument,
move backward into the previous preprocessor conditional.

"#elif" is treated like "#else" followed by "#if", so the
function stops at them when going forward, but not when going