Function regexec 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn regexec(
    regex: *const regex_t,
    input: *const c_char,
    nmatch: size_t,
    pmatch: *mut regmatch_t,
    eflags: c_int,
) -> c_int

See https://pubs.opengroup.org/onlinepubs/9799919799/functions/regexec.html.