📄 getcontext.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>getcontext</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="getcontext"></a> <a name="tag_03_214"></a><!-- getcontext --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_214_01"></a>NAME</h4><blockquote>getcontext, setcontext - get and set current user context</blockquote><h4><a name="tag_03_214_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/ucontext.h.html">ucontext.h</a>><br><br> int getcontext(ucontext_t *</tt><i>ucp</i><tt>);<br> int setcontext(const ucontext_t *</tt><i>ucp</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_214_03"></a>DESCRIPTION</h4><blockquote><p>The <i>getcontext</i>() function shall initialize the structure pointed to by <i>ucp</i> to the current user context of thecalling thread. The <b>ucontext_t</b> type that <i>ucp</i> points to defines the user context and includes the contents of thecalling thread's machine registers, the signal mask, and the current execution stack.</p><p>The <i>setcontext</i>() function shall restore the user context pointed to by <i>ucp</i>. A successful call to<i>setcontext</i>() shall not return; program execution resumes at the point specified by the <i>ucp</i> argument passed to<i>setcontext</i>(). The <i>ucp</i> argument should be created either by a prior call to <i>getcontext</i>() or <a href="../functions/makecontext.html"><i>makecontext</i>()</a>, or by being passed as an argument to a signal handler. If the <i>ucp</i>argument was created with <i>getcontext</i>(), program execution continues as if the corresponding call of <i>getcontext</i>() hadjust returned. If the <i>ucp</i> argument was created with <a href="../functions/makecontext.html"><i>makecontext</i>()</a>,program execution continues with the function passed to <a href="../functions/makecontext.html"><i>makecontext</i>()</a>. When thatfunction returns, the thread shall continue as if after a call to <i>setcontext</i>() with the <i>ucp</i> argument that was inputto <a href="../functions/makecontext.html"><i>makecontext</i>()</a>. If the <i>uc_link</i> member of the <b>ucontext_t</b>structure pointed to by the <i>ucp</i> argument is equal to 0, then this context is the main context, and the thread shall exitwhen this context returns. The effects of passing a <i>ucp</i> argument obtained from any other source are unspecified.</p></blockquote><h4><a name="tag_03_214_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>setcontext</i>() shall not return and <i>getcontext</i>() shall return 0; otherwise, a value of-1 shall be returned.</p></blockquote><h4><a name="tag_03_214_05"></a>ERRORS</h4><blockquote><p>No errors are defined.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_214_06"></a>EXAMPLES</h4><blockquote><p>Refer to <a href="makecontext.html"><i>makecontext</i>()</a> .</p></blockquote><h4><a name="tag_03_214_07"></a>APPLICATION USAGE</h4><blockquote><p>When a signal handler is executed, the current user context is saved and a new context is created. If the thread leaves thesignal handler via <a href="../functions/longjmp.html"><i>longjmp</i>()</a>, then it is unspecified whether the context at the timeof the corresponding <a href="../functions/setjmp.html"><i>setjmp</i>()</a> call is restored and thus whether future calls to<i>getcontext</i>() provide an accurate representation of the current context, since the context restored by <a href="../functions/longjmp.html"><i>longjmp</i>()</a> does not necessarily contain all the information that <i>setcontext</i>()requires. Signal handlers should use <a href="../functions/siglongjmp.html"><i>siglongjmp</i>()</a> or <i>setcontext</i>()instead.</p><p>Conforming applications should not modify or access the <i>uc_mcontext</i> member of <b>ucontext_t</b>. A conforming applicationcannot assume that context includes any process-wide static data, possibly including <i>errno</i>. Users manipulating contextsshould take care to handle these explicitly when required.</p><p>Use of contexts to create alternate stacks is not defined by this volume of IEEE Std 1003.1-2001.</p></blockquote><h4><a name="tag_03_214_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_214_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_214_10"></a>SEE ALSO</h4><blockquote><p><a href="bsd_signal.html"><i>bsd_signal</i>()</a> , <a href="makecontext.html"><i>makecontext</i>()</a> , <a href="setcontext.html"><i>setcontext</i>()</a> , <a href="setjmp.html"><i>setjmp</i>()</a> , <a href="sigaction.html"><i>sigaction</i>()</a> , <a href="sigaltstack.html"><i>sigaltstack</i>()</a> , <a href="siglongjmp.html"><i>siglongjmp</i>()</a> , <a href="sigprocmask.html"><i>sigprocmask</i>()</a> , <a href="sigsetjmp.html"><i>sigsetjmp</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/ucontext.h.html"><i><ucontext.h></i></a></p></blockquote><h4><a name="tag_03_214_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4, Version 2.</p></blockquote><h4><a name="tag_03_214_12"></a>Issue 5</h4><blockquote><p>Moved from X/OPEN UNIX extension to BASE.</p><p>The following sentence was removed from the DESCRIPTION: "If the <i>ucp</i> argument was passed to a signal handler, programexecution continues with the program instruction following the instruction interrupted by the signal."</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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