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/makecontext.3,v 1.4 2002/12/19 09:40:21 ru Exp $ 37.\" $DragonFly: src/lib/libc/gen/makecontext.3,v 1.1 2007/01/16 07:16:23 dillon Exp $ 38.\" 39.Dd September 10, 2002 40.Dt MAKECONTEXT 3 41.Os 42.Sh NAME 43.Nm makecontext , 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.Fo makecontext 51.Fa "ucontext_t *ucp" 52.Fa "void (*func)(void)" 53.Fa "int argc" ... 54.Fc 55.Ft int 56.Fn swapcontext "ucontext_t *oucp" "const ucontext_t *ucp" 57.Sh DESCRIPTION 58The 59.Fn makecontext 60function 61modifies the user thread context pointed to by 62.Fa ucp , 63which must have previously been initialized by a call to 64.Xr getcontext 3 65and had a stack allocated for it. 66The context is modified so that it will continue execution by invoking 67.Fn func 68with the arguments provided. 69The 70.Fa argc 71argument 72must be equal to the number of additional arguments provided to 73.Fn makecontext 74and also equal to the number of arguments to 75.Fn func , 76or else the behavior is undefined. 77.Pp 78The 79.Fa "ucp->uc_link" 80argument 81must be initialized before calling 82.Fn makecontext 83and determines the action to take when 84.Fn func 85returns: 86if equal to 87.Dv NULL , 88the process exits; 89otherwise, 90.Fn setcontext "ucp->uc_link" 91is implicitly invoked. 92.Pp 93The 94.Fn swapcontext 95function 96saves the current thread context in 97.Fa "*oucp" 98and makes 99.Fa "*ucp" 100the currently active context. 101.Sh RETURN VALUES 102If successful, 103.Fn swapcontext 104returns zero; 105otherwise \-1 is returned and the global variable 106.Va errno 107is set appropriately. 108.Sh ERRORS 109The 110.Fn swapcontext 111function 112will fail if: 113.Bl -tag -width Er 114.It Bq Er ENOMEM 115There is not enough stack space in 116.Fa ucp 117to complete the operation. 118.El 119.Sh SEE ALSO 120.Xr setcontext 3 , 121.Xr ucontext 3 122