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

(c-backward-conditional COUNT &optional TARGET-DEPTH WITH-ELSE)

Move back across a preprocessor conditional, leaving mark behind.
A prefix argument acts as a repeat count. With a negative argument,
move forward across a preprocessor conditional.

The optional arguments TARGET-DEPTH and WITH-ELSE are historical,
and have the same meanings as in `c-scan-conditionals'. If you
are calling c-forward-conditional from a program, you might want
to call `c-scan-conditionals' directly instead.