mirror of https://github.com/mkerrisk/man-pages
143 lines
3.7 KiB
Plaintext
143 lines
3.7 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "MAKECONTEXT" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" makecontext
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.SH NAME
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makecontext, swapcontext \- manipulate user contexts
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.SH SYNOPSIS
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.LP
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\fB#include <ucontext.h>
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.br
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.sp
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void makecontext(ucontext_t *\fP\fIucp\fP\fB, void (*\fP\fIfunc\fP\fB)(void),
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.br
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\ \ \ \ \ \ int\fP \fIargc\fP\fB, ...);
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.br
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int swapcontext(ucontext_t *restrict\fP \fIoucp\fP\fB,
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.br
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\ \ \ \ \ \ const ucontext_t *restrict\fP \fIucp\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fImakecontext\fP() function shall modify the context specified
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by \fIucp\fP, which has been initialized using \fIgetcontext\fP().
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When this context is resumed using \fIswapcontext\fP() or \fIsetcontext\fP(),
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program execution shall continue by calling \fIfunc\fP, passing it
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the
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arguments that follow \fIargc\fP in the \fImakecontext\fP() call.
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.LP
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Before a call is made to \fImakecontext\fP(), the application shall
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ensure that the context being modified has a stack
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allocated for it. The application shall ensure that the value of \fIargc\fP
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matches the number of arguments of type \fBint\fP
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passed to \fIfunc\fP; otherwise, the behavior is undefined.
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.LP
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The \fIuc_link\fP member is used to determine the context that shall
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be resumed when the context being modified by
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\fImakecontext\fP() returns. The application shall ensure that the
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\fIuc_link\fP member is initialized prior to the call to
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\fImakecontext\fP().
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.LP
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The \fIswapcontext\fP() function shall save the current context in
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the context structure pointed to by \fIoucp\fP and shall
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set the context to the context structure pointed to by \fIucp\fP.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fIswapcontext\fP() shall return 0. Otherwise,
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-1 shall be returned and \fIerrno\fP set to
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indicate the error.
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.SH ERRORS
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.LP
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The \fIswapcontext\fP() function shall fail if:
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.TP 7
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.B ENOMEM
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The \fIucp\fP argument does not have enough stack left to complete
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the operation.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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The following example illustrates the use of \fImakecontext\fP():
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.sp
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.RS
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.nf
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\fB#include <stdio.h>
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#include <ucontext.h>
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.sp
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static ucontext_t ctx[3];
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.sp
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static void
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f1 (void)
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{
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puts("start f1");
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swapcontext(&ctx[1], &ctx[2]);
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puts("finish f1");
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}
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.sp
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static void
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f2 (void)
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{
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puts("start f2");
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swapcontext(&ctx[2], &ctx[1]);
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puts("finish f2");
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}
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.sp
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int
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main (void)
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{
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char st1[8192];
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char st2[8192];
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.sp
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getcontext(&ctx[1]);
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ctx[1].uc_stack.ss_sp = st1;
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ctx[1].uc_stack.ss_size = sizeof st1;
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ctx[1].uc_link = &ctx[0];
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makecontext(&ctx[1], f1, 0);
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.sp
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getcontext(&ctx[2]);
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ctx[2].uc_stack.ss_sp = st2;
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ctx[2].uc_stack.ss_size = sizeof st2;
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ctx[2].uc_link = &ctx[1];
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makecontext(&ctx[2], f2, 0);
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.sp
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swapcontext(&ctx[0], &ctx[2]);
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return 0;
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}
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIexit\fP() , \fIgetcontext\fP() , \fIsigaction\fP() , \fIsigprocmask\fP()
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, the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, \fI<ucontext.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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