Function fmtmsg 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn fmtmsg(
    classification: c_long,
    label: *const c_char,
    severity: c_int,
    text: *const c_char,
    action: *const c_char,
    tag: *const c_char,
) -> c_int

See https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fmtmsg.h.html