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.\" $FreeBSD: src/lib/libc/gen/ucontext.3,v 1.1.2.1 2002/09/15 00:30:45 archie Exp $
.\" $DragonFly: src/lib/libc/gen/ucontext.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
.\"
.Dd Sep 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:
.Bl -tag -compact -offset 3n -width "mcontext_t  uc_mcontext"
.Pp
.It "ucontext_t *uc_link"
Context to assume when this one returns
.It "sigset_t    uc_sigmask"
Signals being blocked
.It "stack_t     uc_stack"
Stack area
.It "mcontext_t  uc_mcontext"
Saved registers
.El
.Pp
The
.Fa uc_link
field points to the context to resume when this context's entry point
function returns.
If
.Fa uc_link
is equal to
.Dv NULL ,
then the process exits when this context returns.
.Pp
The
.Fa uc_mcontext
field is machine-dependent and should be treated as opaque by
portable applications.
.Sh SEE ALSO
.Xr sigaltstack 2
.Sh BUGS
The
.Fn getcontext ,
.Fn setcontext ,
.Fn makecontext ,
and
.Fn swapcontext
functions are not yet implemented in this version of
.Fx .