1.\" $OpenBSD: pthread_once.3,v 1.15 2015/09/14 13:08:01 schwarze Exp $ 2.\" 3.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by John Birrell. 17.\" 4. Neither the name of the author nor the names of any co-contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.\" $FreeBSD: pthread_once.3,v 1.5 1999/08/28 00:03:09 peter Exp $ 34.\" 35.Dd $Mdocdate: September 14 2015 $ 36.Dt PTHREAD_ONCE 3 37.Os 38.Sh NAME 39.Nm pthread_once 40.Nd dynamic package initialization 41.Sh SYNOPSIS 42.In pthread.h 43.Vt pthread_once_t once_control No = Dv PTHREAD_ONCE_INIT ; 44.Ft int 45.Fn pthread_once "pthread_once_t *once_control" "void (*init_routine)(void)" 46.Sh DESCRIPTION 47The first call to 48.Fn pthread_once 49by any thread in a process, with a given 50.Fa once_control , 51will call the 52.Fn init_routine 53with no arguments. 54Subsequent calls to 55.Fn pthread_once 56with the same 57.Fa once_control 58will not call the 59.Fn init_routine . 60On return from 61.Fn pthread_once , 62it is guaranteed that 63.Fn init_routine 64has completed. 65The 66.Fa once_control 67parameter is used to determine whether the associated initialization 68routine has been called. 69.Pp 70The function 71.Fn pthread_once 72is not a cancellation point. 73However, if 74.Fn init_routine 75is a cancellation point and is cancelled, the effect on 76.Va once_control 77is as if 78.Fn pthread_once 79was never called. 80.Pp 81The constant 82.Dv PTHREAD_ONCE_INIT 83is defined in the header file 84.In pthread.h . 85.Pp 86The behavior of 87.Fn pthread_once 88is undefined if 89.Fa once_control 90has automatic storage duration or is not initialized by 91.Dv PTHREAD_ONCE_INIT . 92.Sh RETURN VALUES 93If successful, the 94.Fn pthread_once 95function will return zero. 96Otherwise an error number will be returned to indicate the error. 97.Sh ERRORS 98None. 99.Sh STANDARDS 100.Fn pthread_once 101conforms to 102.St -p1003.1-96 . 103