[apple/libpthread.git] / man / pthread_key_create.3

.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by John Birrell.
.\" 4. Neither the name of the author nor the names of any co-contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd April 4, 1996
.Dt PTHREAD_KEY_CREATE 3
.Os
.Sh NAME
.Nm pthread_key_create
.Nd thread-specific data key creation
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_key_create "pthread_key_t *key" "void (*destructor)(void *)"
.Sh DESCRIPTION
The
.Fn pthread_key_create
function creates a thread-specific data key visible to all threads in the
process.
Key values provided by
.Fn pthread_key_create
are opaque objects used to locate thread-specific data.
Although the same
key value may be used by different threads, the values bound to the key
by
.Fn pthread_setspecific
are maintained on a per-thread basis and persist for the life of the calling
thread.
.Pp
Upon key creation, the value NULL is associated with the new key in all
active threads.
Upon thread creation, the value NULL is associated with all
defined keys in the new thread.
.Pp
An optional destructor function may be associated with each key value.
At
thread exit, if a key value has a non-NULL destructor pointer, and the
thread has a non-NULL value associated with the key, the function pointed
to is called with the current associated value as its sole argument.
The
order of destructor calls is unspecified if more than one destructor exists
for a thread when it exits.
.Pp
If, after all the destructors have been called for all non-NULL values
with associated destructors, there are still some non-NULL values with
associated destructors, then the process is repeated.
If, after at least
[PTHREAD_DESTRUCTOR_ITERATIONS] iterations of destructor calls for
outstanding non-NULL values, there are still some non-NULL values with
associated destructors, the implementation stops calling destructors.
.Sh RETURN VALUES
If successful, the
.Fn pthread_key_create
function will store the newly created key value at the location specified by
.Fa key
and returns zero.
Otherwise an error number will be returned to indicate
the error.
.Sh ERRORS
The
.Fn pthread_key_create
function will fail if:
.Bl -tag -width Er
.It Bq Er EAGAIN
The system lacked the necessary resources to create another thread-specific
data key, or the system-imposed limit on the total number of keys per process
[PTHREAD_KEYS_MAX] would be exceeded.
.It Bq Er ENOMEM
Insufficient memory exists to create the key.
.El
.Sh SEE ALSO
.Xr pthread_getspecific 3 ,
.Xr pthread_key_delete 3 ,
.Xr pthread_setspecific 3
.Sh STANDARDS
The
.Fn pthread_key_create
function conforms to
.St -p1003.1-96 .
Commit	Line	Data
f1a1da6c A	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	.\"
2546420a	31	.\" $FreeBSD$
f1a1da6c A	32	.\"
	33	.Dd April 4, 1996
	34	.Dt PTHREAD_KEY_CREATE 3
	35	.Os
	36	.Sh NAME
	37	.Nm pthread_key_create
	38	.Nd thread-specific data key creation
	39	.Sh SYNOPSIS
2546420a	40	.In pthread.h
f1a1da6c	41	.Ft int
2546420a	42	.Fn pthread_key_create "pthread_key_t key" "void (destructor)(void *)"
f1a1da6c A	43	.Sh DESCRIPTION
	44	The
	45	.Fn pthread_key_create
2546420a A	46	function creates a thread-specific data key visible to all threads in the
2546420a A	47	process.
f1a1da6c A	48	Key values provided by
f1a1da6c A	49	.Fn pthread_key_create
2546420a	50	are opaque objects used to locate thread-specific data.
f1a1da6c A	51	Although the same
	52	key value may be used by different threads, the values bound to the key
	53	by
	54	.Fn pthread_setspecific
	55	are maintained on a per-thread basis and persist for the life of the calling
	56	thread.
	57	.Pp
	58	Upon key creation, the value NULL is associated with the new key in all
	59	active threads.
	60	Upon thread creation, the value NULL is associated with all
	61	defined keys in the new thread.
	62	.Pp
	63	An optional destructor function may be associated with each key value.
2546420a A	64	At
	65	thread exit, if a key value has a non-NULL destructor pointer, and the
	66	thread has a non-NULL value associated with the key, the function pointed
	67	to is called with the current associated value as its sole argument.
	68	The
	69	order of destructor calls is unspecified if more than one destructor exists
	70	for a thread when it exits.
f1a1da6c A	71	.Pp
	72	If, after all the destructors have been called for all non-NULL values
	73	with associated destructors, there are still some non-NULL values with
	74	associated destructors, then the process is repeated.
	75	If, after at least
	76	[PTHREAD_DESTRUCTOR_ITERATIONS] iterations of destructor calls for
	77	outstanding non-NULL values, there are still some non-NULL values with
	78	associated destructors, the implementation stops calling destructors.
	79	.Sh RETURN VALUES
	80	If successful, the
	81	.Fn pthread_key_create
	82	function will store the newly created key value at the location specified by
	83	.Fa key
	84	and returns zero.
2546420a	85	Otherwise an error number will be returned to indicate
f1a1da6c A	86	the error.
f1a1da6c A	87	.Sh ERRORS
2546420a	88	The
f1a1da6c	89	.Fn pthread_key_create
2546420a	90	function will fail if:
f1a1da6c A	91	.Bl -tag -width Er
	92	.It Bq Er EAGAIN
	93	The system lacked the necessary resources to create another thread-specific
	94	data key, or the system-imposed limit on the total number of keys per process
	95	[PTHREAD_KEYS_MAX] would be exceeded.
	96	.It Bq Er ENOMEM
	97	Insufficient memory exists to create the key.
	98	.El
	99	.Sh SEE ALSO
	100	.Xr pthread_getspecific 3 ,
	101	.Xr pthread_key_delete 3 ,
	102	.Xr pthread_setspecific 3
	103	.Sh STANDARDS
2546420a	104	The
f1a1da6c	105	.Fn pthread_key_create
2546420a	106	function conforms to
f1a1da6c	107	.St -p1003.1-96 .