[apple/libc.git] / gen / FreeBSD / getcontext.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/getcontext.3,v 1.3 2004/12/03 14:10:04 rse Exp $
.\"
.Dd September 10, 2002
.Dt GETCONTEXT 3
.Os
.Sh NAME
.Nm getcontext , setcontext
.Nd get and set user thread context
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In ucontext.h
.Ft int
.Fn getcontext "ucontext_t *ucp"
.Ft int
.Fn setcontext "const ucontext_t *ucp"
.Sh DESCRIPTION
The
.Fn getcontext
function
saves the current thread's execution context in the structure pointed to by
.Fa ucp .
This saved context may then later be restored by calling
.Fn setcontext .
.Pp
The
.Fn setcontext
function
makes a previously saved thread context the current thread context, i.e.,
the current context is lost and
.Fn setcontext
does not return.
Instead, execution continues in the context specified by
.Fa ucp ,
which must have been previously initialized by a call to
.Fn getcontext ,
.Xr makecontext 3 ,
or by being passed as an argument to a signal handler (see
.Xr sigaction 2 ) .
.Pp
If
.Fa ucp
was initialized by
.Fn getcontext ,
then execution continues as if the original
.Fn getcontext
call had just returned (again).
.Pp
If
.Fa ucp
was initialized by
.Xr makecontext 3 ,
execution continues with the invocation of the function specified to
.Xr makecontext 3 .
When that function returns,
.Fa "ucp->uc_link"
determines what happens next:
if
.Fa "ucp->uc_link"
is
.Dv NULL ,
the process exits;
otherwise,
.Fn setcontext "ucp->uc_link"
is implicitly invoked.
.Pp
If
.Fa ucp
was initialized by the invocation of a signal handler, execution continues
at the point the thread was interrupted by the signal.
.Sh RETURN VALUES
If successful,
.Fn getcontext
returns zero and
.Fn setcontext
does not return; otherwise \-1 is returned.
.Sh ERRORS
No errors are defined for
.Fn getcontext
or
.Fn setcontext .
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr sigaltstack 2 ,
.Xr makecontext 3 ,
.Xr ucontext 3
Commit	Line	Data
224c7076 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/getcontext.3,v 1.3 2004/12/03 14:10:04 rse Exp $
	37	.\"
	38	.Dd September 10, 2002
	39	.Dt GETCONTEXT 3
	40	.Os
	41	.Sh NAME
	42	.Nm getcontext , setcontext
	43	.Nd get and set user thread context
	44	.Sh LIBRARY
	45	.Lb libc
	46	.Sh SYNOPSIS
	47	.In ucontext.h
	48	.Ft int
	49	.Fn getcontext "ucontext_t *ucp"
	50	.Ft int
	51	.Fn setcontext "const ucontext_t *ucp"
	52	.Sh DESCRIPTION
	53	The
	54	.Fn getcontext
	55	function
	56	saves the current thread's execution context in the structure pointed to by
	57	.Fa ucp .
	58	This saved context may then later be restored by calling
	59	.Fn setcontext .
	60	.Pp
	61	The
	62	.Fn setcontext
	63	function
	64	makes a previously saved thread context the current thread context, i.e.,
65	the current context is lost and
66	.Fn setcontext
67	does not return.
68	Instead, execution continues in the context specified by
69	.Fa ucp ,
70	which must have been previously initialized by a call to
71	.Fn getcontext ,
72	.Xr makecontext 3 ,
73	or by being passed as an argument to a signal handler (see
74	.Xr sigaction 2 ) .
75	.Pp
76	If
77	.Fa ucp
78	was initialized by
79	.Fn getcontext ,
80	then execution continues as if the original
81	.Fn getcontext
82	call had just returned (again).
83	.Pp
84	If
85	.Fa ucp
86	was initialized by
87	.Xr makecontext 3 ,
88	execution continues with the invocation of the function specified to
89	.Xr makecontext 3 .
90	When that function returns,
91	.Fa "ucp->uc_link"
92	determines what happens next:
93	if
94	.Fa "ucp->uc_link"
95	is
96	.Dv NULL ,
97	the process exits;
98	otherwise,
99	.Fn setcontext "ucp->uc_link"
100	is implicitly invoked.
101	.Pp
102	If
103	.Fa ucp
104	was initialized by the invocation of a signal handler, execution continues
105	at the point the thread was interrupted by the signal.
106	.Sh RETURN VALUES
107	If successful,
108	.Fn getcontext
109	returns zero and
110	.Fn setcontext
111	does not return; otherwise \-1 is returned.
112	.Sh ERRORS
113	No errors are defined for
114	.Fn getcontext
115	or
116	.Fn setcontext .
117	.Sh SEE ALSO
118	.Xr sigaction 2 ,
119	.Xr sigaltstack 2 ,
120	.Xr makecontext 3 ,
121	.Xr ucontext 3