char *cap_to_text(cap_t caps, ssize_t * length_p); ... cap_to_text() converts ... cap_p ... ... he location pointed to by len_p ... should change either the prototype or the description to use either cap_p or caps, as well as len_p or length_p.
Thanks for reporting this! It should be fixed with: https://git.kernel.org/pub/scm/libs/libcap/libcap.git/commit/?id=60ff008d95584cc18701e98ed3cc4fa3d6cef9cb
That last comment was clearly some location phishing attempt. I'll mark the comment as private.