The \fIdestr_function\fP argument,
if not \fBNULL\fP,
specifies a destructor function associated with the key.
-When a thread terminates via \fBpthread_exit\fP or by cancellation,
+When a thread terminates via \fBpthread_exit\fP or by cancelation,
\fIdestr_function\fP is called with arguments
the value associated with the key in that thread.
The \fIdestr_function\fP is not called if that value is \fBNULL\fP.