#### POSIX Threads for Windows – REFERENCE - Pthreads-w32

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## Name

pthread_barrier_destroy, pthread_barrier_init - destroy and initialize a barrier object (ADVANCED REALTIME THREADS)

## Synopsis

#include <pthread.h>

int pthread_barrier_destroy(pthread_barrier_t *barrier);
int pthread_barrier_init(pthread_barrier_t *restrict barrier, const pthread_barrierattr_t *restrict attr, unsigned count);

## Description

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(3) 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(3) 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(3) is undefined.

## Return Value

Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error.

## Errors

The pthread_barrier_destroy function may fail if:

EBUSY
  The implementation has detected an attempt to destroy a barrier while it is in use (for example, while being used in a pthread_barrier_wait(3) call) by another thread.
EINVAL
  The value specified by barrier is invalid.

The pthread_barrier_init function shall fail if:

EAGAIN
  The system lacks the necessary resources to initialize another barrier.
EINVAL
  The value specified by count is equal to zero.
ENOMEM
  Insufficient memory exists to initialize the barrier.

The pthread_barrier_init function may fail if:

EBUSY
  The implementation has detected an attempt to reinitialize a barrier while it is in use (for example, while being used in a pthread_barrier_wait(3) call) by another thread.
EINVAL
  The value specified by attr is invalid.

These functions shall not return an error code of [EINTR].

The following sections are informative.

## Examples

None.

## Application Usage

The pthread_barrier_destroy and pthread_barrier_init functions are part of the Barriers option and need not be provided on all implementations.

Pthreads-w32 defines _POSIX_BARRIERS to indicate that these routines are implemented and may be used.

## Rationale

None.

## Future Directions

None.

## Known Bugs

  In pthreads-win32, pthread_barrier_wait(3) may deadlock if the number of running threads able to wait on the barrier object exceeds the value given as the count parameter in pthread_barrier_init.

## See Also

pthread_barrier_wait(3) , the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>

## Copyright

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 .

Modified by Ross Johnson for use with Pthreads-w32.

Table of Contents

- Name

- Synopsis

- Description

- Return Value

- Errors

- Examples

- Application Usage

- Rationale

- Future Directions

- Known Bugs

- See Also

- Copyright