.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd September 10, 2002
.Dt UCONTEXT 3
.Os
.Sh NAME
.Nm ucontext
.Nd user thread context
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In ucontext.h
.Sh DESCRIPTION
The
.Vt ucontext_t
type is a structure type suitable for holding the context for a user
thread of execution.
A thread's context includes its stack, saved registers, and list of
blocked signals.
.Pp
The
.Vt ucontext_t
structure contains at least these fields:
.Pp
.Bl -tag -width ".Va mcontext_t\ \ uc_mcontext" -offset 3n -compact
.It Va "ucontext_t *uc_link"
context to assume when this one returns
.It Va "sigset_t uc_sigmask"
signals being blocked
.It Va "stack_t uc_stack"
stack area
.It Va "mcontext_t uc_mcontext"
saved registers
.El
.Pp
The
.Va uc_link
field points to the context to resume when this context's entry point
function returns.
If
.Va uc_link
is equal to
.Dv NULL ,
then the process exits when this context returns.
.Pp
The
.Va uc_mcontext
field is machine-dependent and should be treated as opaque by
portable applications.
.Pp
The following functions are defined to manipulate
.Vt ucontext_t
structures:
.Pp
.Bl -item -offset 3n -compact
.It
.Ft int
.Fn getcontext "ucontext_t *" ;
.It
.Ft "ucontext_t *"
.Fn getcontextx "void" ;
.It
.Ft int
.Fn setcontext "const ucontext_t *" ;
.It
.Ft void
.Fn makecontext "ucontext_t *" "void \*[lp]*\*[rp]\*[lp]void\*[rp]" int ... ;
.It
.Ft int
.Fn swapcontext "ucontext_t *" "const ucontext_t *" ;
.El
.Sh SEE ALSO
.Xr sigaltstack 2 ,
.Xr getcontext 3 ,
.Xr getcontextx 3 ,
.Xr makecontext 3