Proposal: non standard user data hook

[Romano Paolo Tenca <rotenca@telvia.it>]

I have seen (under windows) many cases where user must associate some 
data to new thread to be used from another thread. Usually pthread id is 
registered in a user array/list of structures with the data needed for 
future access. When the user need that data he will search the array for 
the pthread id: this means allocation, search, destroy, mutex and a lot 
of complexity, bugs and race conditions.

My proposal is a np set of functions to set and get user data:

    void pthread_userdataset_np(ptrhead_t id, void * userdata)
    void * pthread_userdataget_np(ptrhead_t id)

pthread_userdataget_np return NULL if pthread_userdataset_np() was never 
called or the thread has already been destroyed.

Implementation is very simple: add an user slot to ptw32_thread_t structure.
That slot is totally ignored by pthread functions, only when the 
ptw32_thread_t is destroyed the pointer is set to NULL.


-- 
Romano Paolo Tenca