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