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