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 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 53The 54.Fn getcontext 55function 56saves the current thread's execution context in the structure pointed to by 57.Fa ucp . 58This saved context may then later be restored by calling 59.Fn setcontext . 60.Pp 61The 62.Fn setcontext 63function 64makes a previously saved thread context the current thread context, i.e., 65the current context is lost and 66.Fn setcontext 67does not return. 68Instead, execution continues in the context specified by 69.Fa ucp , 70which must have been previously initialized by a call to 71.Fn getcontext , 72.Xr makecontext 3 , 73or by being passed as an argument to a signal handler (see 74.Xr sigaction 2 ) . 75.Pp 76If 77.Fa ucp 78was initialized by 79.Fn getcontext , 80then execution continues as if the original 81.Fn getcontext 82call had just returned (again). 83.Pp 84If 85.Fa ucp 86was initialized by 87.Xr makecontext 3 , 88execution continues with the invocation of the function specified to 89.Xr makecontext 3 . 90When that function returns, 91.Fa "ucp->uc_link" 92determines what happens next: 93if 94.Fa "ucp->uc_link" 95is 96.Dv NULL , 97the process exits; 98otherwise, 99.Fn setcontext "ucp->uc_link" 100is implicitly invoked. 101.Pp 102If 103.Fa ucp 104was initialized by the invocation of a signal handler, execution continues 105at the point the thread was interrupted by the signal. 106.Sh RETURN VALUES 107If successful, 108.Fn getcontext 109returns zero and 110.Fn setcontext 111does not return; otherwise \-1 is returned. 112.Sh ERRORS 113No errors are defined for 114.Fn getcontext 115or 116.Fn setcontext . 117.Sh SEE ALSO 118.Xr sigaction 2 , 119.Xr sigaltstack 2 , 120.Xr makecontext 3 , 121.Xr ucontext 3 122