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.\" $DragonFly: src/lib/libc/gen/getcontext.3,v 1.1 2007/01/16 07:16:23 dillon Exp $ 38.\" 39.Dd September 10, 2002 40.Dt GETCONTEXT 3 41.Os 42.Sh NAME 43.Nm getcontext , 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 54The 55.Fn getcontext 56function 57saves the current thread's execution context in the structure pointed to by 58.Fa ucp . 59This saved context may then later be restored by calling 60.Fn setcontext . 61.Pp 62The 63.Fn setcontext 64function 65makes a previously saved thread context the current thread context, i.e., 66the current context is lost and 67.Fn setcontext 68does not return. 69Instead, execution continues in the context specified by 70.Fa ucp , 71which must have been previously initialized by a call to 72.Fn getcontext , 73.Xr makecontext 3 , 74or by being passed as an argument to a signal handler (see 75.Xr sigaction 2 ) . 76.Pp 77If 78.Fa ucp 79was initialized by 80.Fn getcontext , 81then execution continues as if the original 82.Fn getcontext 83call had just returned (again). 84.Pp 85If 86.Fa ucp 87was initialized by 88.Xr makecontext 3 , 89execution continues with the invocation of the function specified to 90.Xr makecontext 3 . 91When that function returns, 92.Fa "ucp->uc_link" 93determines what happens next: 94if 95.Fa "ucp->uc_link" 96is 97.Dv NULL , 98the process exits; 99otherwise, 100.Fn setcontext "ucp->uc_link" 101is implicitly invoked. 102.Pp 103If 104.Fa ucp 105was initialized by the invocation of a signal handler, execution continues 106at the point the thread was interrupted by the signal. 107.Sh RETURN VALUES 108If successful, 109.Fn getcontext 110returns zero and 111.Fn setcontext 112does not return; otherwise \-1 is returned. 113.Sh ERRORS 114No errors are defined for 115.Fn getcontext 116or 117.Fn setcontext . 118.Sh SEE ALSO 119.Xr sigaction 2 , 120.Xr sigaltstack 2 , 121.Xr makecontext 3 , 122.Xr ucontext 3 123