.\" Copyright (C) 2001 Andries Brouwer (aeb@cwi.nl)
.\" and Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" 2006-08-02, mtk, Added example program
.\"
.\" Japanese Version Copyright (c) 2001 NAKANO Takeo all rights reserved.
.\" Translated Sat Dec 15 2001 by NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\" Updated 2008-12-24, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v3.15
.\"
.TH MAKECONTEXT 3 2009-03-31 "GNU" "Linux Programmer's Manual"
.SH ̾
makecontext, swapcontext \- 桼ƥȤ
.SH 
.B #include <ucontext.h>
.sp
.BI "void makecontext(ucontext_t *" ucp ", void (*" func )(),
.BI "int " argc ", ...);"
.sp
.BI "int swapcontext(ucontext_t *" oucp ", ucontext_t *" ucp );
.SH 
System V ŪʴĶǤϡ
\fBmcontext_t\fP  \fBucontext_t\fP Ȥ 2 Ĥηȡ
.BR getcontext (2),
.BR setcontext (2),
.BR makecontext (),
.BR swapcontext ()
Ȥ 4 Ĥδؿ
.I <ucontext.h>
Ƥꡢץ沼ˤʣΥåɴ֤ǡ
桼٥ΥƥؤǤ褦ˤʤäƤ롣
.LP
ηȡǽ 2 ĤδؿˤĤƤϡ
.BR getcontext (2)
򻲾ȤΤȡ
.LP
.BR makecontext ()
ؿϡݥ \fIucp\fP ؤƥȤѹ
(\fIucp\fP ϰ
.BR getcontext (2)
ƤӽФ줿ΤǤ)
.BR makecontext ()
ưˤϡƤӽФԤϡΥƥѤ
åݤΥɥ쥹 \fIucp\->uc_stack\fP 
˸ѤΥƥȤΥɥ쥹 \fIucp\->uc_link\fP 
ʤФʤʤ

ΥƥȤ
.RB ( setcontext (2)
ޤ
.BR swapcontext ()
ˤä)
ͭˤȡؿ \fIfunc\fP ƤФ졢
Ȥ
.I argc
ʹߤ
.RI ( int )
Ϥ롣
ƤӽФԤ
.I argc
ˤΰθĿꤷʤФʤʤ
δؿȡѤΥƥȤͭˤʤ롣
ѥƥȤΥݥ󥿤 NULL ξ硢Υåɤλ롣
.LP
.BR swapcontext ()
ؿϸߤΥƥȤ
ݥ \fIoucp\fP ؤ¤Τ¸
ݥ \fIucp\fP ؤƥȤͭˤ롣
.SH ֤
ȡ
.BR swapcontext ()
֤ʤ
( \fIoucp\fP ͭˤʤäˤ֤뤳Ȥ롣
ΤȤˤ
.BR swapcontext ()
 0 ֤褦˸롣)
Ԥȡ
.BR swapcontext ()
 \-1 ֤
\fIerrno\fP 򥨥顼˱ꤹ롣
.SH 顼
.TP
.B ENOMEM
å˳Ƥ֤ĤäƤʤ
.SH С
.BR makecontext ()

.BR swapcontext ()
ϡС 2.1 ʹߤ glibc 󶡤Ƥ롣
.SH 
SUSv2, POSIX.1-2001.
POSIX.1-2008 Ǥϡ꤫ܿ
.BR makecontext ()

.BR swapcontext ()
λͤƤ롣
ˡץꥱ POSIX åɤȤäƽľȤ
侩Ƥ롣
.SH 
\fIucp\->uc_stack\fP β
.BR sigaltstack (2)
ξƱǤ롣
ʤι¤Τˤϡ
åȤѤΰγϥɥ쥹Ĺޤޤ졢
ϥåӤɤǤ뤫ˤϴطʤ
äơ桼ץϤηˤĤƤϿۤʤƤ褤

.I int
ȥݥ󥿷Ʊ礭Ǥ륢ƥǤ
(x86-32 ϤǤꡢξηȤ 32 ӥåȤǤ)
.BR makecontext ()

.I argc
ʹߤΰȤƥݥ󥿤ϤƤ⤦ޤư⤷ʤ
ʤ顢Τ褦ˤȡܿݾڤ줺
ɸ˽ư̤Ǥꡢݥ󥿤
.I int
礭ƥǤưʤȤ
ˤؤ餺С 2.8 ʹߤ glibc Ǥϡ
.BR makecontext (3)
ѹԤ졢(x86-64 ʤɤ) Ĥ 64 ӥåȥƥ
Ȥƥݥ󥿤ϤȤǤ褦ˤʤäƤ롣
.SH 
.PP
ʲΥץ롦ץϡ
.BR getcontext (2),
.BR makecontext (),
.BR swapcontext ()
λˡ򼨤ΤǤ롣
Υץ¹ԤȡʲΤ褦ʽϤ:
.in +4n
.nf

.RB "$" " ./a.out"
main: swapcontext(&uctx_main, &uctx_func2)
func2: started
func2: swapcontext(&uctx_func2, &uctx_func1)
func1: started
func1: swapcontext(&uctx_func1, &uctx_func2)
func2: returning
func1: returning
main: exiting
.fi
.in
.SS ץΥ
\&
.nf
#include <ucontext.h>
#include <stdio.h>
#include <stdlib.h>

static ucontext_t uctx_main, uctx_func1, uctx_func2;

#define handle_error(msg) \\
    do { perror(msg); exit(EXIT_FAILURE); } while (0)

static void
func1(void)
{
    printf("func1: started\\n");
    printf("func1: swapcontext(&uctx_func1, &uctx_func2)\\n");
    if (swapcontext(&uctx_func1, &uctx_func2) == \-1)
        handle_error("swapcontext");
    printf("func1: returning\\n");
}

static void
func2(void)
{
    printf("func2: started\\n");
    printf("func2: swapcontext(&uctx_func2, &uctx_func1)\\n");
    if (swapcontext(&uctx_func2, &uctx_func1) == \-1)
        handle_error("swapcontext");
    printf("func2: returning\\n");
}

int
main(int argc, char *argv[])
{
    char func1_stack[16384];
    char func2_stack[16384];

    if (getcontext(&uctx_func1) == \-1)
        handle_error("getcontext");
    uctx_func1.uc_stack.ss_sp = func1_stack;
    uctx_func1.uc_stack.ss_size = sizeof(func1_stack);
    uctx_func1.uc_link = &uctx_main;
    makecontext(&uctx_func1, func1, 0);

    if (getcontext(&uctx_func2) == \-1)
        handle_error("getcontext");
    uctx_func2.uc_stack.ss_sp = func2_stack;
    uctx_func2.uc_stack.ss_size = sizeof(func2_stack);
    /* Successor context is f1(), unless argc > 1 */
    uctx_func2.uc_link = (argc > 1) ? NULL : &uctx_func1;
    makecontext(&uctx_func2, func2, 0);

    printf("main: swapcontext(&uctx_main, &uctx_func2)\\n");
    if (swapcontext(&uctx_main, &uctx_func2) == \-1)
        handle_error("swapcontext");

    printf("main: exiting\\n");
    exit(EXIT_SUCCESS);
}
.fi
.SH Ϣ
.BR getcontext (2),
.BR sigaction (2),
.BR sigaltstack (2),
.BR sigprocmask (2),
.BR sigsetjmp (3)