NAME
pthread_once —
dynamic package
initialization
SYNOPSIS
#include
<pthread.h>
pthread_once_t once_control =
PTHREAD_ONCE_INIT;
int
pthread_once(pthread_once_t
*once_control, void
(*init_routine)(void));
DESCRIPTION
The first call to
pthread_once()
by any thread in a process, with a given once_control,
will call the
init_routine()
with no arguments. Subsequent calls to
pthread_once() with the same
once_control will not call the
init_routine(). On return from
pthread_once(), it is guaranteed that
init_routine() has completed. The
once_control parameter is used to determine whether
the associated initialization routine has been called.
The function
pthread_once()
is not a cancellation point. However, if
init_routine()
is a cancellation point and is cancelled, the effect on
once_control is as if
pthread_once() was never called.
The constant PTHREAD_ONCE_INIT is defined
in the header file
<pthread.h>.
The behavior of
pthread_once()
is undefined if once_control has automatic storage
duration or is not initialized by
PTHREAD_ONCE_INIT.
RETURN VALUES
If successful, the pthread_once() function
will return zero. Otherwise an error number will be returned to indicate the
error.
ERRORS
None.
STANDARDS
pthread_once() conforms to
ISO/IEC 9945-1:1996 (“POSIX.1”).