252 lines
7.4 KiB
HTML
252 lines
7.4 KiB
HTML
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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>C++ destructors and Pthread termination</title>
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</head>
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<body>
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</script>
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<a name="Top_Of_Page"></a>
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<h2>C++ destructors and Pthread termination</h2>
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<p>Unlike some other implementations of threads, C++ destructors for automatic
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objects are allowed to run in a well defined and consistent manner when a
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thread is terminated.</p>
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<p>The following list includes some of the causes of thread termination:</p>
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<ul>
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<li>A thread calls <strong>pthread_exit</strong>() or returns from the thread
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start routine.</li>
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<li>A thread is the target of <strong>pthread_cancel</strong>().</li>
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<li>A thread is ended due to an unhandled exception.</li>
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<li>A thread is in a process that contains another thread that calls <strong>
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exit</strong>() or <strong>abort</strong>().</li>
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<li>A thread is in a process that is terminated by the system
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administrator.</li>
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<li>A thread is being terminated by the system administrator.</li>
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</ul>
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<p>When a thread terminates, the following occurs:</p>
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<ol>
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<li>If the thread was ended using <strong>pthread_exit</strong>(), <strong>
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pthread_cancel</strong>() or return from the thread start routine, then
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cancellation cleanup handlers and data destructors are run.</li>
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<li>The thread is terminated. At the time that the thread is terminated, both
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C++ destructors for automatic objects and i5/OS cancel handlers run.</li>
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</ol>
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<p>If a Pthread is terminated using a non-Pthread method (an i5/OS exception,
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a different thread termination primitive provided by the system, <strong>
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exit</strong>() or <strong>abort</strong>(), or other job termination method),
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Pthread cancellation cleanup handlers and data destructors do not run.</p>
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<br>
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<h3>Example</h3>
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<p>This example shows the relationship between C++ destructors and Pthread
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cleanup mechanisms.</p>
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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 <stdio.h>
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#include <qp0z1170.h>
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#include <time.h>
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#include <pthread.h>
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#include "check.h"
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#define bufferSize 100
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#define threadRc 55
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pthread_key_t tlskey;
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void dataDestructor(void *parm);
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void cancelHandler(void *parm);
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void *threadfunc(void *parm);
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void level2(void);
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void level3(void);
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class A {
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public:
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A(char *label);
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~A();
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private:
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pthread_id_np_t tid;
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char buffer[bufferSize];
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};
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void dataDestructor(void *parm) {
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printf("In data destructor\n");
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pthread_setspecific(tlskey, NULL);
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}
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void cancelHandler(void *parm) {
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printf("In cancellation cleanup handler\n");
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}
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void *threadfunc(void *parm) {
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A object("start routine object");
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level2();
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return NULL;
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}
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void level2(void) {
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A object("Second level object");
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level3();
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}
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void level3(void) {
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int rc;
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struct timespec ts = {5, 0};
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A object("Third level object");
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pthread_setspecific(tlskey, &tlskey);
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pthread_cleanup_push(cancelHandler, NULL);
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printf("Thread blocked\n");
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rc = pthread_delay_np(&ts);
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if (rc != 0) {
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printf("pthread_delay_np() - return code %d\n", rc);
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return;
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}
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printf("Calling pthread_exit()\n");
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pthread_exit(__VOID(threadRc));
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pthread_cleanup_pop(0);
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}
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int main(int argc, char **argv)
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{
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int rc=0;
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int i;
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pthread_t threadid;
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void *status;
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int fail=0;
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printf("Enter Testcase - %s\n", argv[0]);
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rc = pthread_key_create(&tlskey, dataDestructor);
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checkResults("pthread_key_create()\n", rc);
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printf("----------- Start pthread_cancel() example -------------\n");
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printf("Create a thread\n");
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rc = pthread_create(&threadid, NULL, threadfunc, NULL);
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checkResults("pthread_create()\n", rc);
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sleep(2);
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rc = pthread_cancel(threadid);
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checkResults("pthread_cancel()\n", rc);
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rc = pthread_join(threadid, &status);
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checkResults("pthread_join()\n", rc);
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if (status != PTHREAD_CANCELED) {
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printf("Canceled thread did not return the expected results\n");
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fail = 1;
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}
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printf("----------- Start pthread_exit() example -------------\n");
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printf("Create a thread\n");
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rc = pthread_create(&threadid, NULL, threadfunc, NULL);
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checkResults("pthread_create()\n", rc);
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rc = pthread_join(threadid, &status);
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checkResults("pthread_join()\n", rc);
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if (__INT(status) != threadRc) {
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printf("pthread_exit() thread did not return the expected results\n");
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fail = 1;
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}
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pthread_key_delete(tlskey);
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if (fail) {
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printf("At least one thread failed!\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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A::A(char *label) {
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strncpy(buffer, label, bufferSize);
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pthread_t me;
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me = pthread_self();
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pthread_getunique_np(&me, &tid);
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printf("`%s' instantiated in thread 0x%.8x %.8x\n",
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buffer, tid);
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}
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A::~A() {
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printf("`%s' destroyed in thread 0x%.8x %.8x\n",
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buffer, tid);
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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/TPCPP0
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----------- Start pthread_cancel() example -------------
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Create a thread
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`start routine object' instantiated in thread 0x00000000 00000161
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`Second level object' instantiated in thread 0x00000000 00000161
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`Third level object' instantiated in thread 0x00000000 00000161
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Thread blocked
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In cancellation cleanup handler
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In data destructor
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`Third level object' destroyed in thread 0x00000000 00000161
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`Second level object' destroyed in thread 0x00000000 00000161
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`start routine object' destroyed in thread 0x00000000 00000161
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----------- Start pthread_exit() example -------------
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Create a thread
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`start routine object' instantiated in thread 0x00000000 00000162
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`Second level object' instantiated in thread 0x00000000 00000162
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`Third level object' instantiated in thread 0x00000000 00000162
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Thread blocked
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Calling pthread_exit()
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In cancellation cleanup handler
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In data destructor
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`Third level object' destroyed in thread 0x00000000 00000162
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`Second level object' destroyed in thread 0x00000000 00000162
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`start routine object' destroyed in thread 0x00000000 00000162
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Main completed
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</pre>
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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">
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<a href="#Top_Of_Page">Top</a> |
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<a href="rzah4mst.htm">Pthread APIs</a> |
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<a href="aplist.htm">APIs by 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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