NAME
pthread_once —
dynamic package
initialization
LIBRARY
POSIX Threads Library (libpthread, -lpthread)
SYNOPSIS
#include <pthread.h>
int
pthread_once(
pthread_once_t
*once_control,
void
(*init_routine)(void));
pthread_once_t once_control =
PTHREAD_ONCE_INIT
;
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
initializes the static
once synchronization control structure
once_control to
be used with
pthread_once(). 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
The function conforms to
IEEE Std 1003.1-2001
(“POSIX.1”).