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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>longjmp</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_448"> </a>NAME</h4><blockquote>longjmp - non-local goto</blockquote><h4><a name = "tag_000_007_449"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="setjmp.h.html">setjmp.h</a>>void longjmp(jmp_buf <i>env</i>, int <i>val</i>);</code></pre></blockquote><h4><a name = "tag_000_007_450"> </a>DESCRIPTION</h4><blockquote>The<i>longjmp()</i>function restores the environment saved by the most recent invocation of<i><a href="setjmp.html">setjmp()</a></i>in the same thread, with the corresponding<i>jmp_buf</i>argument. If there is no such invocation, or if the function containing theinvocation of<i><a href="setjmp.html">setjmp()</a></i>has terminated execution in the interim, the behaviour is undefined. It is unspecified whether<i>longjmp()</i>restores the signal mask, leaves the signal mask unchanged or restores it toits value at the time<i><a href="setjmp.html">setjmp()</a></i>was called.<p>All accessible objects have values as of the time<i><a href="setjmp.html">setjmp()</a></i>was called, except that the values of objects of automaticstorage duration are indeterminate if they meet all the following conditions:<ul><p><li>They are local to the function containing the corresponding<i><a href="setjmp.html">setjmp()</a></i>invocation.<p><li>They do not have volatile-qualified type.<p><li>They are changed between the<i><a href="setjmp.html">setjmp()</a></i>invocation and<i>longjmp()</i>call.<p></ul><p>As it bypasses the usual function call and return mechanisms,<i>longjmp()</i>will execute correctly in contexts of interrupts, signals and any of theirassociated functions. However, if<i>longjmp()</i>is invoked from a nested signal handler (that is, from afunction invoked as a result of a signal raised during thehandling of another signal), the behaviour is undefined.<p>The effect of a call to<i>longjmp()</i>where initialisation of the<b>jmp_buf</b>structure was not performed in the calling thread is undefined.</blockquote><h4><a name = "tag_000_007_451"> </a>RETURN VALUE</h4><blockquote>After<i>longjmp()</i>is completed, program execution continues as if the correspondinginvocation of<i><a href="setjmp.html">setjmp()</a></i>had just returned the value specified by<i>val</i>.The<i>longjmp()</i>function cannot cause<i><a href="setjmp.html">setjmp()</a></i>to return 0; if<i>val</i>is 0,<i><a href="setjmp.html">setjmp()</a></i>returns 1.</blockquote><h4><a name = "tag_000_007_452"> </a>ERRORS</h4><blockquote>No errors are defined.</blockquote><h4><a name = "tag_000_007_453"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_454"> </a>APPLICATION USAGE</h4><blockquote>Applications whose behaviour depends on the value of the signal maskshould not use<i>longjmp()</i>and<i><a href="setjmp.html">setjmp()</a></i>,since their effect on the signal mask is unspecified, but should instead usethe<i><a href="siglongjmp.html">siglongjmp()</a></i>and<i><a href="sigsetjmp.html">sigsetjmp()</a></i>functions (which can save and restore the signal mask under applicationcontrol).</blockquote><h4><a name = "tag_000_007_455"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_456"> </a>SEE ALSO</h4><blockquote><i><a href="setjmp.html">setjmp()</a></i>,<i><a href="sigaction.html">sigaction()</a></i>,<i><a href="siglongjmp.html">siglongjmp()</a></i>,<i><a href="sigsetjmp.html">sigsetjmp()</a></i>,<i><a href="setjmp.h.html"><setjmp.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from Issue 1 of the SVID.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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