1.\" $OpenBSD: pthread_key_create.3,v 1.9 2013/06/05 03:44:50 tedu 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_key_create.3,v 1.5 1999/08/28 00:03:06 peter Exp $ 34.\" 35.Dd $Mdocdate: June 5 2013 $ 36.Dt PTHREAD_KEY_CREATE 3 37.Os 38.Sh NAME 39.Nm pthread_key_create 40.Nd thread-specific data key creation 41.Sh SYNOPSIS 42.In pthread.h 43.Ft int 44.Fn pthread_key_create "pthread_key_t *key" "void (*destructor)(void *)" 45.Sh DESCRIPTION 46The 47.Fn pthread_key_create 48function creates a thread-specific data key visible to all threads in the 49process. 50Key values provided by 51.Fn pthread_key_create 52are opaque objects used to locate thread-specific data. 53Although the same 54key value may be used by different threads, the values bound to the key 55by 56.Fn pthread_setspecific 57are maintained on a per-thread basis and persist for the life of the calling 58thread. 59.Pp 60Upon key creation, the value NULL is associated with the new key in all 61active threads. 62Upon thread creation, the value NULL is associated with all 63defined keys in the new thread. 64.Pp 65An optional destructor function may be associated with each key value. 66At thread exit, if a key value has a non-NULL destructor pointer, and the 67thread has a non-NULL value associated with the key, the function pointed 68to is called with the current associated value as its sole argument. 69The order of destructor calls is unspecified if more than one destructor exists 70for a thread when it exits. 71.Pp 72If, after all the destructors have been called for all non-NULL values 73with associated destructors, there are still some non-NULL values with 74associated destructors, then the process is repeated. 75If, after at least 76[PTHREAD_DESTRUCTOR_ITERATIONS] iterations of destructor calls for 77outstanding non-NULL values, there are still some non-NULL values with 78associated destructors, the implementation stops calling destructors. 79.Sh RETURN VALUES 80If successful, the 81.Fn pthread_key_create 82function will store the newly created key value at the location specified by 83.Fa key 84and returns zero. 85Otherwise an error number will be returned to indicate the error. 86.Sh ERRORS 87.Fn pthread_key_create 88will fail if: 89.Bl -tag -width Er 90.It Bq Er EAGAIN 91The system lacked the necessary resources to create another thread-specific 92data key, or the system-imposed limit on the total number of keys per process 93[PTHREAD_KEYS_MAX] would be exceeded. 94.It Bq Er ENOMEM 95Insufficient memory exists to create the key. 96.El 97.Sh SEE ALSO 98.Xr pthread_getspecific 3 , 99.Xr pthread_key_delete 3 , 100.Xr pthread_setspecific 3 101.Sh STANDARDS 102.Fn pthread_key_create 103conforms to 104.St -p1003.1-96 . 105