238 lines
7.3 KiB
HTML
238 lines
7.3 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>pthread_clear_exit_np()--Clear Exit Status of Thread</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ========================================== -->
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<!-- NETMG2 SCRIPT A converted by B2H R4.1 (346) (CMS) by HOLTJM at -->
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<!-- RCHVMW2 on 29 Jan 1999 at 10:01:37 -->
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<!--File Edited November 2001 -->
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<!--End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>pthread_clear_exit_np()--Clear Exit Status of Thread</h2>
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<div class="box" style="width: 50%;">
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<br>
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Syntax:
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<pre>
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#include <pthread.h
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int pthread_clear_exit_np(void);
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</pre>
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Service Program Name: QP0WPTHR<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE <br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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Signal Safe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>pthread_clear_exit_np</strong>() function clears the exit status
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of the thread. If the thread is currently exiting due to a call to
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<strong>pthread_exit</strong>() or is the target of a
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<strong>pthread_cancel</strong>(), then
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<strong>pthread_clear_exit_np</strong>() can be used in conjunction with
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<strong>setjmp</strong>(), <strong>longjmp</strong>(), and
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<strong>pthread_setcancelstate</strong>() to prevent a thread from terminating,
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and `handle' the exit condition.</p>
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<p>The only supported way to prevent thread exit during the condition in which
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<strong>pthread_exit</strong>() was called, or action is being taken for the
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target of a <strong>pthread_cancel</strong>() is shown in the example. It
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consists of using <strong>longjmp</strong>() from a cancellation cleanup
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handler back into some thread routine that is still on the invocation stack.
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From that routine, the functions <strong>pthread_clear_exit_np</strong>(), and
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<strong>pthread_setcancelstate</strong>() are used to restore the state of the
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thread before the condition that was causing the thread exit.</p>
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<p><strong>Note:</strong> This function is not portable.</p>
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<br>
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<h3>Authorities and Locks</h3>
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<p>None.</p>
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<br>
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<h3>Parameters</h3>
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<p>None.</p>
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<br>
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<h3>Return Value</h3>
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<dl>
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<dt><strong>0</strong></dt>
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<dd><strong>pthread_clear_exit_np</strong>() was successful.<br><br></dd>
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<dt><strong>value</strong></dt>
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<dd><strong>pthread_clear_exit_np</strong>() was not successful. <em>value</em>
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is set to indicate the error condition.</dd>
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</dl>
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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>pthread_clear_exit</strong>_np() was not successful, the error
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condition returned usually indicates one of the following errors. Under some
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conditions, the value returned could indicate an error other than those listed
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here.</p>
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<dl>
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<dt><em>[EINVAL]</em></dt>
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<dd><p>The thread is not currently exiting</p></dd>
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</dl>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li>The <<strong>pthread.h</strong>> header file. See <a href=
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"rzah4hed.htm">Header files for Pthread functions</a>.<br><br></li>
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<li><a href="users_18.htm">pthread_exit()</a>--Terminate Calling Thread<br><br></li>
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<li><a href="users_39.htm">pthread_cancel()</a>--Cancel Thread</li>
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</ul>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<pre>
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#define _MULTI_THREADED
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#include <pthread.h>
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#include <stdio.h>
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#include <except.h>
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#include <setjmp.h>
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#include "check.h"
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int threadStatus=1;
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void cleanupHandler(void *p)
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{
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jmp_buf *j = (jmp_buf *)p;
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/* Warning, it is quite possible that using combinations of */
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/* setjmp(), longjmp(), pthread_clear_exit_np(), and */
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/* pthread_setcancelstate() to handle thread exits or */
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/* cancellation could result in looping or non-cancelable */
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/* threads if done incorrectly. */
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printf("In cancellation cleanup handler. Handling the thread exit\n");
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longjmp(*j, 1);
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printf("The exit/cancellation was not stopped!\n");
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return;
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}
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void *threadfunc(void *parm)
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{
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jmp_buf j;
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int rc, old;
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printf("Inside secondary thread\n");
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if (setjmp(j)) {
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/* Returned from longjmp after stopping the thread exit */
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/* Since longjmp was called from within the cancellation */
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/* cleanup handler, we must clear the exit state of the */
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/* thread and reset the cancelability state to what it was */
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/* before the cancellation cleanup handlers were called */
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/* (Cancellation cleanup handlers are called with */
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/* thread cancellation disabled) */
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printf("Stopped the thread exit, now clean up the states\n");
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printf("Clear exit state\n");
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rc = pthread_clear_exit_np();
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checkResults("pthread_clear_exit_np()\n", rc);
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printf("Restore cancel state\n");
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rc = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &old);
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checkResults("pthread_setcancelstate()\n", rc);
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/* This example was successful */
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threadStatus = 0;
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}
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else {
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printf("Pushing cleanup handler that will stop the exit\n");
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pthread_cleanup_push(cleanupHandler, &j);
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/* This exit will be stopped by cleanupHandler2 and the */
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/* pthread_clear_exit_np() that is done above */
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pthread_exit(__VOID(threadStatus));
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printf("Did not expect to get here! Left status as 1.\n");
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pthread_cleanup_pop(0);
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}
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pthread_exit(__VOID(threadStatus));
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}
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int main(int argc, char **argv)
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{
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pthread_t thread;
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int rc=0;
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char c;
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void *status;
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printf("Enter Testcase - %s\n", argv[0]);
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printf("Create thread that will demonstrate handling an exit\n");
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rc = pthread_create(&thread, NULL, threadfunc, NULL);
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checkResults("pthread_create()\n", rc);
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rc = pthread_join(thread, &status);
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checkResults("pthread_join()\n", rc);
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if (__INT(status) != 0) {
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printf("Got an unexpected return status from the thread!\n");
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exit(1);
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}
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printf("Main completed\n");
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return 0;
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}
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</pre>
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<p><strong>Output:</strong></p>
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<pre>
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Enter Testcase - QP0WTEST/TPCEXIT0
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Create thread that will demonstrate handling an exit
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Inside secondary thread
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Pushing cleanup handler that will stop the exit
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In cancellation cleanup handler. Handling the thread exit
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Stopped the thread exit, now clean up the states
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Clear exit state
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Restore cancel state
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Main completed
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</pre><br>
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<hr>
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API introduced: V4R3
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"rzah4mst.htm">Pthread APIs</a> | <a href="aplist.htm">APIs by
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category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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