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 MAKECONTEXT 3 40.Os 41.Sh NAME 42.Nm makecontext 43.Nm swapcontext 44.Nd modify and exchange user thread contexts 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.In ucontext.h 49.Ft void 50.Fn makecontext "ucontext_t *ucp" "void (*func)()" "int argc" "..." 51.Ft int 52.Fn swapcontext "ucontext_t *oucp" "const ucontext_t *ucp" 53.Sh DESCRIPTION 54.Fn makecontext 55modifies the user thread context pointed to by 56.Fa ucp , 57which must have previously been initialized by a call to 58.Fn getcontext 59and had a stack allocated for it. 60The context is modified so that it will continue execution by invoking 61.Fn func 62with the arguments provided. 63.Fa argc 64must be equal to the number of additional arguments provided to 65.Fn makecontext 66and also equal to the number of parameters to 67.Fn func , 68or else the behavior is undefined. 69.Pp 70.Fa "ucp->uc_link" 71must be initialized before calling 72.Fn makecontext 73and determines the action to take when 74.Fn func 75returns: 76if equal to 77.Dv NULL , 78the process exits; 79otherwise, 80.Fn setcontext "ucp->uc_link" 81is implicitly invoked. 82.Pp 83.Fn swapcontext 84saves the current thread context in 85.Fa "*oucp" 86and makes 87.Fa "*ucp" 88the currently active context. 89.Sh RETURN VALUES 90If successful, 91.Fn swapcontext 92returns zero; 93otherwise -1 is returned and 94.Va errno 95is set appropriately. 96.Sh ERRORS 97.Fn swapcontext 98will fail if: 99.Bl -tag -width Er 100.It Bq Er ENOMEM 101There is not enough stack space in 102.Fa ucp 103to complete the operation. 104.El 105.Sh SEE ALSO 106.Xr setcontext 3 , 107.Xr ucontext 3 108