1.\" $OpenBSD: pthread_key_create.3,v 1.5 1999/11/24 05:35:32 d Exp $ 2.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>. 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. All advertising materials mentioning features or use of this software 14.\" must display the following acknowledgement: 15.\" This product includes software developed by John Birrell. 16.\" 4. Neither the name of the author nor the names of any co-contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $FreeBSD: pthread_key_create.3,v 1.5 1999/08/28 00:03:06 peter Exp $ 33.\" 34.Dd April 4, 1996 35.Dt PTHREAD_KEY_CREATE 3 36.Os 37.Sh NAME 38.Nm pthread_key_create 39.Nd thread-specific data key creation 40.Sh SYNOPSIS 41.Fd #include <pthread.h> 42.Ft int 43.Fn pthread_key_create "pthread_key_t *key" "void (*destructor)(void *)" 44.Sh DESCRIPTION 45The 46.Fn pthread_key_create 47function creates a thread-specific data key visible to all threads in the 48process. Key values provided by 49.Fn pthread_key_create 50are opaque objects used to locate thread-specific data. Although the same 51key value may be used by different threads, the values bound to the key 52by 53.Fn pthread_setspecific 54are maintained on a per-thread basis and persist for the life of the calling 55thread. 56.Pp 57Upon key creation, the value NULL is associated with the new key in all 58active threads. Upon thread creation, the value NULL is associated with all 59defined keys in the new thread. 60.Pp 61An optional destructor function may be associated with each key value. At 62thread exit, if a key value has a non-NULL destructor pointer, and the 63thread has a non-NULL value associated with the key, the function pointed 64to is called with the current associated value as its sole argument. The 65order of destructor calls is unspecified if more than one destructor exists 66for a thread when it exits. 67.Pp 68If, after all the destructors have been called for all non-NULL values 69with associated destructors, there are still some non-NULL values with 70associated destructors, then the process is repeated. If, after at least 71[PTHREAD_DESTRUCTOR_ITERATIONS] iterations of destructor calls for 72outstanding non-NULL values, there are still some non-NULL values with 73associated destructors, the implementation stops calling destructors. 74.Sh RETURN VALUES 75If successful, the 76.Fn pthread_key_create 77function will store the newly created key value at the location specified by 78.Fa key 79and returns zero. Otherwise an error number will be returned to indicate 80the error. 81.Sh ERRORS 82.Fn pthread_key_create 83will fail if: 84.Bl -tag -width Er 85.It Bq Er EAGAIN 86The system lacked the necessary resources to create another thread-specific 87data key, or the system-imposed limit on the total number of keys per process 88[PTHREAD_KEYS_MAX] would be exceeded. 89.It Bq Er ENOMEM 90Insufficient memory exists to create the key. 91.El 92.Sh SEE ALSO 93.Xr pthread_getspecific 3 , 94.Xr pthread_key_delete 3 , 95.Xr pthread_setspecific 3 96.Sh STANDARDS 97.Fn pthread_key_create 98conforms to ISO/IEC 9945-1 ANSI/IEEE 99.Pq Dq Tn POSIX 100Std 1003.1 Second Edition 1996-07-12. 101