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)