function associates a thread-specific value with a
obtained via a previous call to
Different threads can bind different values to the same key.
These values are
typically pointers to blocks of dynamically allocated memory that have been
reserved for use by the calling thread.
The effect of calling
with a key value not obtained from
has been deleted with
function may be called from a thread-specific data destructor function,
however this may result in lost storage or infinite loops if doing so
causes non-NULL key values to remain after
iterations of destructor calls have been made.