Function strtoul 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn strtoul(
    str: *const c_char,
    endptr: *mut *mut c_char,
    base: c_int,
) -> c_ulong

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

Converts the initial portion of the string pointed to by str to a type unsigned long.

Upon success, returns the converted value. If no conversion could be performed or the value of base is not supported, returns 0.