/I> in the calling thread. 
</P>
<P>The routines <B>pthread_setspecific</B>, <B>pthread_getspecific</B>,
and <B>pthread_key_delete</B> can be called from <I>destr_function</I>
targeting any valid key including the key on which <I>destr_function</I>
is currently operating. If <B>pthread_getspecific</B> is called on
the key whose thread specific data is being destroyed, the value NULL
is returned, unless <B>pthread_setspecific</B> was called previously
on that key from within <I>destr_function</I> to set the 