Function pthread_attr_getstacksize 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_attr_getstacksize(
    attr: *const pthread_attr_t,
    stacksize: *mut size_t,
) -> c_int

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