The pthread_barrier_destroy() function shall destroy the barrier
referenced by barrier and release any resources used by the barrier.
The effect of subsequent use of the barrier is undefined until the barrier is
reinitialized by another call to pthread_barrier_init(). An
implementation may use this function to set barrier to an invalid
value. The results are undefined if pthread_barrier_destroy() is called
when any thread is blocked on the barrier, or if this function is called with
an uninitialized barrier.
The pthread_barrier_init() function shall allocate any resources required
to use the barrier referenced by barrier and shall initialize the
barrier with attributes referenced by attr. If attr is NULL, the
default barrier attributes shall be used; the effect is the same as passing
the address of a default barrier attributes object. The results are undefined
if pthread_barrier_init() is called when any thread is blocked on the
barrier (that is, has not returned from the pthread_barrier_wait()
call). The results are undefined if a barrier is used without first being
initialized. The results are undefined if pthread_barrier_init() is
called specifying an already initialized barrier.
The count argument specifies the number of threads that must call
pthread_barrier_wait() before any of them successfully return from the
call. The value specified by count must be greater than zero.
If the pthread_barrier_init() function fails, the barrier shall not be
initialized and the contents of barrier are undefined.
Only the object referenced by barrier may be used for performing
synchronization. The result of referring to copies of that object in calls to
pthread_barrier_destroy() or pthread_barrier_wait() is
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html