<code>Sizeof</code> are compile-time constant expressions of type <code>uintptr</code>.
</p>

<p>
The function <code>Add</code> adds <code>len</code> to <code>ptr</code>
and returns the updated pointer <code>unsafe.Pointer(uintptr(ptr) + uintptr(len))</code>.
The <code>len</code> argument must be of integer type or an untyped <a href="#Constants">constant</a>.