have pointers into the C world and to free those pointers when they
are no longer needed.  To help, the Go code can define Go objects
holding the C pointers and use runtime.SetFinalizer on those Go objects.

It is much more difficult for the C world to have pointers into the Go
world, because the Go garbage collector is unaware of the memory
allocated by C.  The most important consideration is not to

</p>

<h3 id="finalizer">Finalizers</h3>

<p>
The <a href="/pkg/runtime/"><code>runtime</code></a> package provides
a <code>SetFinalizer</code> function that adds a finalizer to be called when
a particular object is no longer reachable by the program.
A call to <code>SetFinalizer(x, f)</code> is synchronized before the finalization call <code>f(x)</code>.
</p>

<h3 id="more">Additional Mechanisms</h3>

<p>