The destructor function passed to PR_NewThreadPrivateIndex that is associated with the resulting thread private index.
#include <prthread.h> typedef void (PR_CALLBACK *PRThreadPrivateDTOR)(void *priv);
Until the data associated with an index is actually set with a call to
PR_SetThreadPrivate, the value of the data is
NULL. If the data associated with the index is not
NULL, NSPR passes a reference to the data to the destructor function when the thread terminates.