PTHREAD_COND_INIT(3C) Standard C Library Functions PTHREAD_COND_INIT(3C)

NAME

pthread_cond_init, pthread_cond_destroy - initialize or destroy condition
variables

SYNOPSIS

cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>

int pthread_cond_init(pthread_cond_t *restrict cond,
const pthread_condattr_t *restrict attr);


int pthread_cond_destroy(pthread_cond_t *cond


pthread_cond_t cond= PTHREAD_COND_INITIALIZER;

DESCRIPTION

The function pthread_cond_init() initializes the condition variable
referenced by cond with attributes referenced by attr. If attr is NULL,
the default condition variable attributes are used; the effect is the
same as passing the address of a default condition variable attributes
object. See pthread_condattr_init(3C). Upon successful initialization,
the state of the condition variable becomes initialized.


Attempting to initialize an already initialized condition variable
results in undefined behavior.


The function pthread_cond_destroy() destroys the given condition variable
specified by cond; the object becomes, in effect, uninitialized. An
implementation may cause pthread_cond_destroy() to set the object
referenced by cond to an invalid value. A destroyed condition variable
object can be re-initialized using pthread_cond_init(); the results of
otherwise referencing the object after it has been destroyed are
undefined.


It is safe to destroy an initialized condition variable upon which no
threads are currently blocked. Attempting to destroy a condition variable
upon which other threads are currently blocked results in undefined
behavior.


In cases where default condition variable attributes are appropriate, the
macro PTHREAD_COND_INITIALIZER can be used to initialize condition
variables that are statically allocated. The effect is equivalent to
dynamic initialization by a call to pthread_cond_init() with parameter
attr specified as NULL, except that no error checks are performed.

RETURN VALUES

If successful, the pthread_cond_init() and pthread_cond_destroy()
functions return 0. Otherwise, an error number is returned to indicate
the error. The EBUSY and EINVAL error checks, if implemented, act as if
they were performed immediately at the beginning of processing for the
function and caused an error return prior to modifying the state of the
condition variable specified by cond.

ERRORS

The pthread_cond_init() function will fail if:

EAGAIN
The system lacked the necessary resources (other than memory)
to initialize another condition variable.


ENOMEM
Insufficient memory exists to initialize the condition
variable.


The pthread_cond_init() function may fail if:

EBUSY
The implementation has detected an attempt to re-initialize the
object referenced by cond, a previously initialized, but not
yet destroyed, condition variable.


EINVAL
The value specified by attr is invalid.


The pthread_cond_destroy() function may fail if:

EBUSY
The implementation has detected an attempt to destroy the
object referenced by cond while it is referenced (for example,
while being used in a pthread_cond_wait() or
pthread_cond_timedwait()) by another thread.


EINVAL
The value specified by cond is invalid.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO

pthread_cond_broadcast(3C), pthread_cond_signal(3C),
pthread_cond_timedwait(3C), pthread_cond_wait(3C),
pthread_condattr_init(3C), attributes(7), condition(7), standards(7)

March 23, 2005 PTHREAD_COND_INIT(3C)