[apple/libc.git] / gen / makecontext.3

.\" Copyright (c) 2002 Packet Design, LLC.
.\" All rights reserved.
.\"
.\" Subject to the following obligations and disclaimer of warranty,
.\" use and redistribution of this software, in source or object code
.\" forms, with or without modifications are expressly permitted by
.\" Packet Design; provided, however, that:
.\"
.\"    (i)  Any and all reproductions of the source or object code
.\"         must include the copyright notice above and the following
.\"         disclaimer of warranties; and
.\"    (ii) No rights are granted, in any manner or form, to use
.\"         Packet Design trademarks, including the mark "PACKET DESIGN"
.\"         on advertising, endorsements, or otherwise except as such
.\"         appears in the above copyright notice or in the software.
.\"
.\" THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
.\" THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
.\" WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
.\" OR NON-INFRINGEMENT.  PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
.\" OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
.\" OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
.\" RELIABILITY OR OTHERWISE.  IN NO EVENT SHALL PACKET DESIGN BE
.\" LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
.\" OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
.\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
.\" DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
.\" USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 PACKET DESIGN IS ADVISED OF
.\" THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $FreeBSD: src/lib/libc/gen/makecontext.3,v 1.4 2002/12/19 09:40:21 ru Exp $
.\"
.Dd September 10, 2002
.Dt MAKECONTEXT 3
.Os
.Sh NAME
.Nm makecontext , swapcontext
.Nd modify and exchange user thread contexts
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In ucontext.h
.Ft void
.Fo makecontext
.Fa "ucontext_t *ucp"
.Fa "void \*[lp]*func\*[rp]\*[lp]\*[rp]"
.Fa "int argc" ...
.Fc
.Ft int
.Fn swapcontext "ucontext_t *oucp" "const ucontext_t *ucp"
.Sh DESCRIPTION
The
.Fn makecontext
function
modifies the user thread context pointed to by
.Fa ucp ,
which must have previously been initialized by a call to
.Xr getcontext 3
and had a stack allocated for it.
The context is modified so that it will continue execution by invoking
.Fn func
with the arguments (of type
.Ft int )
provided.
The
.Fa argc
argument
must be equal to the number of additional arguments provided to
.Fn makecontext
and also equal to the number of arguments to
.Fn func ,
or else the behavior is undefined.
.Pp
The
.Fa "ucp->uc_link"
argument
must be initialized before calling
.Fn makecontext
and determines the action to take when
.Fn func
returns:
if equal to
.Dv NULL ,
the process exits;
otherwise,
.Fn setcontext "ucp->uc_link"
is implicitly invoked.
.Pp
The
.Fn swapcontext
function
saves the current thread context in
.Fa "*oucp"
and makes
.Fa "*ucp"
the currently active context.
.Sh RETURN VALUES
If successful,
.Fn swapcontext
returns zero;
otherwise \-1 is returned and the global variable
.Va errno
is set appropriately.
.Sh ERRORS
The
.Fn swapcontext
function
will fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
There is not enough stack space in
.Fa ucp
to complete the operation.
.El
.Sh SEE ALSO
.Xr setcontext 3 ,
.Xr ucontext 3
Commit	Line	Data
34e8f829 A	1	.\" Copyright (c) 2002 Packet Design, LLC.
	2	.\" All rights reserved.
	3	.\"
	4	.\" Subject to the following obligations and disclaimer of warranty,
	5	.\" use and redistribution of this software, in source or object code
	6	.\" forms, with or without modifications are expressly permitted by
	7	.\" Packet Design; provided, however, that:
	8	.\"
	9	.\" (i) Any and all reproductions of the source or object code
	10	.\" must include the copyright notice above and the following
	11	.\" disclaimer of warranties; and
	12	.\" (ii) No rights are granted, in any manner or form, to use
	13	.\" Packet Design trademarks, including the mark "PACKET DESIGN"
	14	.\" on advertising, endorsements, or otherwise except as such
	15	.\" appears in the above copyright notice or in the software.
	16	.\"
	17	.\" THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
	18	.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
	19	.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
	20	.\" THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
	21	.\" WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
	22	.\" OR NON-INFRINGEMENT. PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
	23	.\" OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
	24	.\" OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
	25	.\" RELIABILITY OR OTHERWISE. IN NO EVENT SHALL PACKET DESIGN BE
	26	.\" LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
	27	.\" OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
	28	.\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
	29	.\" DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
	30	.\" USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF
	31	.\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	32	.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
	33	.\" THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF
	34	.\" THE POSSIBILITY OF SUCH DAMAGE.
	35	.\"
	36	.\" $FreeBSD: src/lib/libc/gen/makecontext.3,v 1.4 2002/12/19 09:40:21 ru Exp $
	37	.\"
	38	.Dd September 10, 2002
	39	.Dt MAKECONTEXT 3
	40	.Os
	41	.Sh NAME
	42	.Nm makecontext , swapcontext
	43	.Nd modify and exchange user thread contexts
	44	.Sh LIBRARY
	45	.Lb libc
	46	.Sh SYNOPSIS
	47	.In ucontext.h
	48	.Ft void
	49	.Fo makecontext
	50	.Fa "ucontext_t *ucp"
	51	.Fa "void \[lp]func\[rp]\[lp]\*[rp]"
	52	.Fa "int argc" ...
	53	.Fc
	54	.Ft int
	55	.Fn swapcontext "ucontext_t oucp" "const ucontext_t ucp"
	56	.Sh DESCRIPTION
	57	The
	58	.Fn makecontext
	59	function
	60	modifies the user thread context pointed to by
	61	.Fa ucp ,
	62	which must have previously been initialized by a call to
	63	.Xr getcontext 3
	64	and had a stack allocated for it.
65	The context is modified so that it will continue execution by invoking
66	.Fn func
67	with the arguments (of type
68	.Ft int )
69	provided.
70	The
71	.Fa argc
72	argument
73	must be equal to the number of additional arguments provided to
74	.Fn makecontext
75	and also equal to the number of arguments to
76	.Fn func ,
77	or else the behavior is undefined.
78	.Pp
79	The
80	.Fa "ucp->uc_link"
81	argument
82	must be initialized before calling
83	.Fn makecontext
84	and determines the action to take when
85	.Fn func
86	returns:
87	if equal to
88	.Dv NULL ,
89	the process exits;
90	otherwise,
91	.Fn setcontext "ucp->uc_link"
92	is implicitly invoked.
93	.Pp
94	The
95	.Fn swapcontext
96	function
97	saves the current thread context in
98	.Fa "*oucp"
99	and makes
100	.Fa "*ucp"
101	the currently active context.
102	.Sh RETURN VALUES
103	If successful,
104	.Fn swapcontext
105	returns zero;
106	otherwise \-1 is returned and the global variable
107	.Va errno
108	is set appropriately.
109	.Sh ERRORS
110	The
111	.Fn swapcontext
112	function
113	will fail if:
114	.Bl -tag -width Er
115	.It Bq Er ENOMEM
116	There is not enough stack space in
117	.Fa ucp
118	to complete the operation.
119	.El
120	.Sh SEE ALSO
121	.Xr setcontext 3 ,
122	.Xr ucontext 3