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 MAKECONTEXT 3 40.Os 41.Sh NAME 42.Nm makecontext , swapcontext 43.Nd modify and exchange user thread contexts 44.Sh LIBRARY 45.Lb libc 46.Sh SYNOPSIS 47.In ucontext.h 48.Ft void 49.Fo makecontext 50.Fa "ucontext_t *ucp" 51.Fa "void \*[lp]*func\*[rp]\*[lp]void\*[rp]" 52.Fa "int argc" ... 53.Fc 54.Ft int 55.Fn swapcontext "ucontext_t *oucp" "const ucontext_t *ucp" 56.Sh DESCRIPTION 57The 58.Fn makecontext 59function 60modifies the user thread context pointed to by 61.Fa ucp , 62which must have previously been initialized by a call to 63.Xr getcontext 3 64and had a stack allocated for it. 65The context is modified so that it will continue execution by invoking 66.Fn func 67with the arguments provided. 68The 69.Fa argc 70argument 71must be equal to the number of additional arguments provided to 72.Fn makecontext 73and also equal to the number of arguments to 74.Fn func , 75or else the behavior is undefined. 76.Pp 77The 78.Fa "ucp->uc_link" 79argument 80must be initialized before calling 81.Fn makecontext 82and determines the action to take when 83.Fn func 84returns: 85if equal to 86.Dv NULL , 87the process exits; 88otherwise, 89.Fn setcontext "ucp->uc_link" 90is implicitly invoked. 91.Pp 92The 93.Fn swapcontext 94function 95saves the current thread context in 96.Fa "*oucp" 97and makes 98.Fa "*ucp" 99the currently active context. 100.Sh RETURN VALUES 101If successful, 102.Fn swapcontext 103returns zero; 104otherwise \-1 is returned and the global variable 105.Va errno 106is set appropriately. 107.Sh ERRORS 108The 109.Fn swapcontext 110function 111will fail if: 112.Bl -tag -width Er 113.It Bq Er ENOMEM 114There is not enough stack space in 115.Fa ucp 116to complete the operation. 117.El 118.Sh SEE ALSO 119.Xr setcontext 3 , 120.Xr ucontext 3 121